Excellence in Lightweight Design - The Institute of Lightweight Engineering and Polymer Technology

IN FOCUS: GERMANY´S ELITE-INSTITUTES

EXCELLENCE IN LIGHTWEIGHT DESIGN INSTITUTE OF LIGHTWEIGHT ENGINEERING AND POLYMER TECHNOLOGY

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QuaLität know-how

maschinen technoLogien

heimat des spritzgiessens marktführerschaft Leidenschaft weitbLick

innovation

Seitdem sich ARBURG mit dem Spritzgießen beschäftigt, geschieht das mit dem Anspruch, die Heimat dieses Verfahrens zu sein. Weil es in unseren Genen liegt können wir gar nicht anders, als uns mit kompromissloser Konsequenz und Hingabe der Weiterentwicklung und Perfektionierung des Spritzgießens zu widmen. Dabei haben wir immer ein Ziel vor Augen: Ihren Erfolg. www.arburg.com

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Institute of Lightweight Engineering and Polymer Technology

�� Editorial �� Having taken root in the early 1950s, Dresden’s long tradition of lightweight engineering was given new structure and direction when the Institute of Lightweight Engineering and Poly­ mer Technology (ILK) was established in 1994.

Since then, the ILK has gradually developed into not only one of the largest and most highperforming research institutes at Technische Universität Dresden, but also Germany’s lea­ ding specialist in the field of integrated light­ weight engineering based on hybrid design con­­cepts. Inspired by our tradition, and with our sights set firmly on making Saxony a bea­ con for science and industry on the interna­ tional lightweight engineering landscape, our team of over 240 employees develops new technologies and materials for function-integra­ tive lightweight engineering based on multimaterial design.

The appointment of a four-member board of management in 2015 enabled us to take a num­ ber of promising new paths. Nine expert groups now focus on a variety of disciplines within the field of lightweight engineering, thus fostering specialization among both our employees and the ILK as a whole. The institute’s objectives are defined in the ILK Future Portfolio 2030, which not only covers macrotopics such as design and calculation methods for integrated lightweight engineering based on multi-material design, resource-efficient, self-adapting proces­ sing techniques, methods compatible with mul­ tiple materials and technologies facilitating closed recycling cycles, but also targets syner­ getic, goal-oriented knowledge and technology transfer processes characterized by both close cooperation between research, industry and academia and a dynamic alumni network.

Demand for outstanding expertise in the fields of materials science and lightweight engineering is huge, which makes shorter innovation cycles necessary. Our combination of strong em­­phasis on the practical applicability of our re­­­­­­­­­search fin­ dings and a deep under­standing of the funda­ mental theories involved therefore makes us an ideal partner for indus­trial R&D pro­jects. The development of inno­vative mate­rials and the use thereof contribute to solve real-world challenges are at the heart of both our research and teach­ ing, with students in­tegrated into prac­tical re­

by Hubert Jäger search projects right from the beginning of their studies and benefitting from excellent prospects on the domestic and international job markets.

Dresden offers an optimum environment for highly innovative research and development in the fields of new materials and lightweight engineering. In particular, the city possesses an almost perfect blend of all the elements re­ quired for the development of innovative mate­ rials and the application thereof in practical sce­ narios. As such, Dresden is home for a unique constellation of materials-driven research and development facilities for which we are envied throughout the world.

In recent years TU Dresden has developed into one of Germany’s leading universities – not least because of its successful participation in the na­­­tional Excellence Initiative set up by the Ger­man federal government and federal states. From a local perspective, the university also benefits from a range of strong scientific and industrial partners in the shape of DRESDEN concept, a network set up to raise international awareness of excellent Dresden-based research and use partnerships to develop joint expertise. All of this and more places the Saxon capital at the fore­ front of German research into new materials for modern lightweight engineering applications. Our research partners draw considerable benefit from our membership of DRESDEN concept, especial­ ly as it enables us to develop solutions to com­ plex interdisciplinary problems that extend bey­ ond the boundaries of lightweight engineering.

Contact

Prof. Dr. rer. nat. Hubert Jäger Chair of Lightweight Systems Engineering and Multi Material Design, Spokesman of the Management Board Phone: +49 (0)351 463 37 900 hubert.jaeger@tu-dresden.de

This magazine uses selected development projects to present our institute, introduce our team and highlight our expertise. It is our plea­ sure to not only offer you insights into our philo­ sophy and working methods, but also arouse your curiosity in Dresden as a centre for light­ weight engineering. Our comprehensive knowhow, dedicated team and creative atmosphere speak for themselves. Welcome to the capital of new materials and lightweight engineering – welcome to the Institute of Lightweight Engi­ neering and Polymer Technology in Dresden!

Yours, Hubert Jäger Board Spokesman for the ILK

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

�� Content�� 1 Editorial

by Hubert Jäger, Chair of Lightweight Systems Engineering and Multi Material Design, Spokesman of the Management Board

10 Excellence in Lightweight Design – The Institute of Lightweight Engineering and Polymer Technology (ILK) at TU Dresden 18 FOREL: Electrifying Lightweight Design Maik Gude, Michael Müller, Michael Stegelmann

24 University Technology Centre Dresden – Lightweight Engineering for Rolls-Royce Maik Gude, Albert Langkamp

30 Thermoplastic Composites for Large-Scale serial Production Niels Modler, Werner Hufenbach

34 Piezoceramics in fibre-reinforced composites – Manufacturing Technologies

suitable for series production Niels Modler, Maik Gude, Anja Winkler, Tony Weber, Sirko Geller, Martin Dannemann, Klaudiusz Holeczek

42 Lightweight Engineering Methods for Medical Applications Angelos Filippatos, Robert Gottwald, Martin Dannemann, Michael Kucher

46 Material Models for textile-reinforced composites Robert Böhm, Ilja Koch, Mike Thieme, Gordon Just

54 Lightweight Design – The Systems of the Future Stefan Kipfelsberger, Jörn Kiele

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Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

62 Simulation Methods for High Performance Structures Bernd Grüber, Andreas Hornig, Roman Koschichow

69 Taking THERMOPLASTIc PROcESSes to the next Level Daniel Barfuß, Michael Krahl, Alexander Liebsch, Teresa Möbius

75 well shaped and quickly reacted Sirko Geller, Andreas Gruhl, Michael Müller, Oliver Weißenborn

80 joining composites efficiently René Füßel, Wikentij Koshukow, Robert Kupfer, Martin Pohl, Juliane Troschitz, Christian Vogel

86 Testing of materials, semi-finished Products

and components at ILK Christoph Ebert, Jörn Jaschinski, Michael Müller, Thomas Behnisch

92 Function integration at Material and system Level

Martin Dannemann, Robin Höhne, Pawel Kostka, Peter Lucas, Anja Winkler

97 Novel Materials and Processes – Special Solutions to Special Challenges Thomas Behnisch, Daniel Weck, Michel Wolf, Christian Vogel, Daniel S. Wolz, Alexander Rohkamm, Johanna Maier, Andreas Borowski, Eike Dohmen

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ENGEL AUSTRIA GMBH

››IN-SITU-POLYMERISATION AUF DEM WEG ZUR SERIE ‹‹ In der Spritzgießindustrie ist es Stand der Technik, in einem Arbeitsschritt einsatzfertige Bauteile zu produzieren.

Von diesem Effizienzideal ist die Fertigung von Leichtbaukomponenten mit Gewebe- oder Gelegeverstärkung noch ein gutes Stück entfernt, doch der Abstand wird kleiner. Auf der K 2016 präsentierte ENGEL AUSTRIA erstmalig einen seriennahen Mehrkomponentenprozess für die In-situ-Polymerisation von ε-Caprolactam zu FVK-Tragstrukturen und deren Funktionalisierung im Spritzguss.

Repräsentativ für das breite Einsatzspektrum hat das Technologiezentrum für Leichtbau-Composites von ENGEL die

hochautomatisierte Fertigungszelle für die Herstellung von Leichtbauschaufeln ausgelegt. Die Schließeinheit der v-duo 700 Vertikalmaschine ist mit einem Schiebetisch mit zwei Werkzeughälften ausgestattet. Die Verstärkungstextilien werden in die erste Kavität eingelegt und mit der reaktiven Matrix ( ε -Caprolactam) infiltriert.

Dank der niedrigen Viskosität des aufgeschmolzenen Monomers lassen sich die trockenen Fasern besonders gut benetzen.

So bildet sich beim Polymerisieren zu Polyamid 6 ein stark belastbarer Verbund, der sich unmittelbar nach seiner Herstellung in die zweite Kavität umsetzen lässt, um Verstärkungsrippen und Konturen aus kurzglasfaserverstärktem PA 6 anzuspritzen.

Polymerisation und Spritzgießprozess fin-

den parallel zueinander statt. Auf diese Weise liefert der integrierte Prozess in einem Arbeitsschritt einsatzfertige Teile und trägt gleichzeitig dem Trend zu einem stärkeren Einsatz von thermoplastischen Matrixmaterialien Rechnung.

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ENGEL. Ihr Partner für Faserverbundanlagen Weniger Gewicht, flexible Designs, beste Eigenschaften: Die Zukunft gehört dem Faserverbund-Leichtbau. Als treibende Kraft in der Kunststoffverarbeitung ist ENGEL der ideale Partner auf dem Weg zu innovativen Produkten.

Wir begleiten Sie mit Kompetenz, Erfahrung und visionären Lösungen zum Thema Faserverbundanlagen.

www.engelglobal.com

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�� index of advertisers �� 27 A&M Kinzel Siebdruckmaschinen Ltd. Was es so alles für den Druck gibt...

41 ADETE – Advanced Engineering

& Technologies GmbH ADETE – der Pionier im kommerziellen Composites-Engineering

7 Apodius GmbH 3D Digitalisierung und Fehlerde­tektion für die Faserverbundproduktion mit neuer Flexibilität für die wirtschaft­liche Absicherung von Kleinserien

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Arburg GmbH & Co. KG

Profoam: Physikalisch geschäumte Leichtbauteile

29 Compositence GmbH Generative Fertigung mit Compositence RoboMAG-T

9 D&S Holding GmbH Strahlen im automobilen Leichtbau

16 Elbe Flugzeugwerke GmbH Kundenanforderungen im Fokus der EFW Produktentwicklung

5 Engel Austria GmbH In-Situ-Polymerisation auf dem Weg zur Serie

60 GK Concept GmbH 15 GWT-TUD GmbH ILK und GWT: Gemeinsam auf dem Weg von der Wissenschaft zur Anwendung

53 Herbert Hänchen GmbH & Co. KG Revolution in der Werkstofftechnik: H-CFK statt Stahl

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APODIUS GMBH

›› 3D DIGITALISIERUNG UND FEHLERDETEKTION FÜR DIE

FASERVERBUNDPRODUKTION MIT NEUER FLEXIBILITÄT FÜR DIE WIRTSCHAFTLICHE ABSICHERUNG VON KLEINSERIEN ‹‹

Apodius GmbH, Teil von Hexagon Manufacturing Intelligence, stellt sein neuartiges, flexibles Apodius Vision System 3D zur dreidimensionalen Bauteildigitalisierung vor. Den Anforderungen an die Apodius Vision System Produktfamilie entsprechend, wurde das Apodius 3D speziell für die Qualitätssicherung und Bauteilauslegung in der Faserverbundproduktion entwickelt. Neu sind insbesondere flexible, handgeführte 3D-Messsysteme, die im Anlauf von Großserienproduktionen benötigt werden und gleichzeitig die wirtschaftliche Absicherung von Kleinserien ermöglichen.

Qualitätssicherung und Prozessautomatisierung stellen die erfolgskritischen Faktoren zur wirtschaftlichen Etablierung der Produktion von FVK-Bauteilen dar. Während im Bereich der Prozessautomatisierung innerhalb der vergangenen Jahre enorme Potenziale realisiert werden konnten, sehen sich produzierende Unternehmen im Bereich der Qualitätssicherung weiterhin mit der zunehmenden Herausforderung konfrontiert, den Qualitätsansprüchen des Marktes gerecht zu werden und ihre Prozesse sowie Bauteile anhand von Vorgaben bewerten zu müssen. Ohne zerstörende Vorbereitungen der textilen Zwischenerzeugnisse stoßen herkömmliche Messsysteme aufgrund des heterogenen optischen Verhaltens der Fasern an ihre Leistungsgrenzen oder erreichen nicht die geforderten Messgenauigkeiten.

Speziell für FVK-Bauteile ausgelegte Weiterentwicklungen im Bereich optischer Messtechnik ermöglichen erstmals die wirtschaftliche Umsetzung der Qualitätssicherung in der Klein- und Großserie.

2D Messungen Das Apodius Vision System 2D ist ein speziell für die Faserorientierungsmessung und Fehlerdetektion entwickeltes optisches Messsystem, welches sich sowohl zur vollautomatisierten Inline-Messung, als auch zur stationären Offline-Messung eignet. Hiermit werden bisher vor allem Großserien und Hightech-Anwendungen für 100%-Prüfungen oder eine statistische Prozessregelung (SPC) ausgestattet. Die Texturinformationen der Bauteile werden mit hochauflösenden optischen Systemen

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erfasst und anschließend analysiert. Dabei kann die Faserorientierung aufgrund einer Texturauswertung der Rohbilddaten zuverlässig mit einer Auflösung von 0,1 Grad bestimmt werden. Es handelt sich um die Basisfunktion einer Systemfamilie, auf deren Basis u.a. anforderungsspezifische Module zur Fehlerdetektion ergänzt werden können. Die Apodius 2D Vision Systeme ermöglichen somit als das einzige auf dem Markt erhältliche System für FVK-Bauteile valide Messungen zur Produktionsfreigabe und die notwendige statistische Prozesskontrolle inkl. der Bewertung der Fähigkeit der Produktionsprozesse, die für zulassungsrelevante Merkmale, wie der Faserorientierung oder Fehlerausprägungen, bei Faserverbundbauteilen sicherzustellen sind.

3D Digitalisierung Die zweidimensionalen Texturinformationen ergänzt Apodius mit dem Apodius Vision System 3D erstmals um räumliche Bauteilinformationen und ermöglicht somit eine vollständige Digitalisierung und Analyse von FVK-Bauteilen. Durch die Kombination eines ROMER Absolute Arms mit einem auf dem Apodius Vision System 2D basierenden Messsystem realisiert Apodius Synergieeffekte, die die bestmögliche Nutzung der komplementären Eigenschaften beider Systeme ermöglicht.

Unter Verwendung des integrierten Laserlichtschnittsensors werden die geometrischen Attribute des Bauteils gescannt und eine Punktewolke generiert, anhand derer die Geometrie des Bauteils gemessen werden kann.

Für die anschließende optische Aufnahme der Oberflächenstruktur findet ein gezielt ausgelegtes Kamerasystem mit einer HochleistungsLED-Beleuchtung Verwendung, wodurch hochqualitative Bauteilaufnahmen sichergestellt werden. Ein speziell entwickeltes Datenfusionsmodell ermöglicht es, Textur- und Geometriemessung miteinander zu kombinieren.

Dabei dient der ROMER Arm mit seiner präzisen Positions- und Ausrichtungsgenauigkeit als globales Referenzsystem, mit dem die Lagebeziehungen zwischen Bauteil, Sensorkopf und Arm für jede Position im Raum eindeutig bestimmt werden können. Die Positionsdaten von Sensorebene und Bauteiloberfläche ermöglichen es, die Bildinformationen einer eindeutigen Position auf der

Bauteiloberfläche zuzuordnen. Die Bild- und Geometrieinformationen setzen in ihrer Gesamtheit ein digitales Modell des Bauteils zusammen. Durch die gewonnene Flexibilisierung des Messsystems ist es nun möglich die Großserienfertigungen während des Produktentstehungsprozesses bis hin zur Zulassung bzw. Produktionsfreigabe optimal vorzubereiten. Gleichzeitig profitieren Hersteller kleiner und mittlerer Serien, die bisherige Investitionen in eigentlich notwendige Messtechnik nicht finanzieren konnten, weil die notwendige Flexibilität und Produktunabhängigkeit fehlte. Da der zumutbare Stand der Technik mittlerweile eine Produktionslenkung des Merkmals Faserorientierung für tragende Faserverbundbauteile erzwingt, ist das neue Apodius Vision System 3D ein wesentlicher Stützpfeiler einer qualitätsgesicherten Produktion. Das System ermöglicht eine industrielle Produktion, die handwerkliche Eigenschaften überwindet und sicherstellt, dass die realisierten Bauteile den Anforderungen entsprechen.

Apodius Explorer 3D Die Auswertung der Messergebnisse erfolgt mittels des neuen Apodius Explorer 3D. Hierbei handelt es sich um eine von Apodius entwickelte, umfassende Softwarelösung, die den gesamten Messprozess in Echtzeit visualisiert und die Messergebnisse automatisch auswertet. Im Anschluss an die Messung stehen dem Anwender verschiedene „Quality Tools“ zur Verfügung, die eine Fehlerdetektion und Bauteilanalyse sowie einen Soll-IstDaten-Abgleich ermöglichen. Als Referenzobjekte können sowohl Konstruktions- und Simulationsdaten als auch zuvor digitalisierte Masterbauteile definiert werden.

Die validen Messergebnisse können weiterhin mittels Exportfunktionen für iterative Simulations- oder Konstruktionszwecke verwendet und somit für ein optimiertes Leichtbaudesign zurückgeführt werden. www.apodius.de

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52 Korropol Leichtbau-Systemtechnologien 61 Lätzsch GmbH Kunststoffverarbeitung Ihr kompetenter Partner

40 Leichtbau-Zentrum Sachsen GmbH 8 Mitras Composites Systems GmbH U3 Research Center Carbon Fibers Saxony

at Technische Universität Dresden U4 Rolls-Royce Deutschland

3 Symate GmbH 104 Imprint

40 Jahre SMC- und BMC - Verarbeitung • • • • • •

Pressen Spritzgießen Powder-in-Mould-Coating In-Mould-Labeling Automatisierung Hybridtechnologie

Wir sind Ihr Partner für zielgenaue Lösungen! www.mitras-composites.de 096-497-015_cs5.indd 1

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d&s holding gmbh

›› Strahlen im automobilen leichtbau ‹‹ Zur Senkung der CO2 -Emissionen setzen Automobilhersteller zunehmend auf den Einsatz von hochfesten Stählen und CFK-Bauteilen. Diese Werkstoffe machen jedoch den Einsatz innovativer und besonders präziser Strahlverfahren notwendig.

Ab 2020 gilt in der EU ein CO 2 - Grenzwert für Neuwagen von 95 g pro Kilometer.

Neben der Effizienzsteigerung von Motoren und der Entwicklung alternativer Antriebe ist die Reduktion des Fahrzeuggewichtes eine wesentliche Stellschraube, um diese Vorgabe zu erreichen. Möglich wird dies unter anderem durch den zunehmenden Einsatz von warmumgeformten, hochfesten Stählen und CFK-Bauteilen.

Bauteile aus beiden Werkstoffen erfordern jedoch vor ihrer Weiterverarbeitung eine Oberflächenbearbeitung durch den Einsatz spezieller Strahlverfahren. Während Serienbauteile aus Stahl vornehmlich durch Schleuderradstrahlanlagen von Zunder und Oxiden gereinigt werden, hat sich für CFK-Bauteile der Einsatz von Strahlanlagen auf Basis des Injektorstrahlens bewährt. Bei diesem Verfahren wird in der Strahlpistole ein Unterdruck erzeugt, der das Strahlmittel ansaugt und der austretenden Druckluft beimischt. Diese be-

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schleunigt das Strahlmittel dann bis zum Austritt aus der Strahldüse. Neben knapp zwanzig Schleuderradstrahlanlagen an sechs Standorten in Deutschland verfügt die D & S Sandstrahltechnik GmbH über zwei robotergestützte InjektordruckluftStrahlanlagen für die Bearbeitung von CFK-Bauteilen.

Hochfesten Stahl verzugsarm strahlen Die Warmumformung hochfester Stahlteile führt trotz Schutzgas zur Oxidation der Bauteiloberflächen. Vor der Weiterverarbeitung müssen diese Oxidationsprodukte wie Zunder oder Zinkoxide entfernt werden, da sonst Probleme beim Schweißen und/oder dem Lackieren auftreten. Dies erfolgt durch das Reinigungsstrahlen der Bauteile. Da allerdings die Materialdicken der Bauteile mittlerweile teils deutlich unter 1 mm liegen und die Geometrien komplexer werden – beispielsweise bei den A- und B-Säulen sowie den Seitenschwellern –, sind die Anforderungen an das verzugsarme Strahlen dieser Bauteile in den vergangenen Jahren zunehmend gestiegen.

Punktgenaues Strahlen an der CFK-Klebestelle Im Rahmen des automobilen Leichtbaus sind auch Werkstoffe auf Basis von CFK

auf dem Vormarsch. Bauteile aus CFK, d. h. aus Kohlenstofffaserverstärkten Kunststoffen, verfügen über eine ähnliche Stabilität wie Stahl, sind aber nur halb so schwer. Im Karosseriebau kann CFK allerdings nicht geschweißt werden, sondern wird verklebt. Um eine reproduzierbare Qualität der Verklebung zu erreichen, ist eine mechanische Vorbehandlung der Klebestellen notwendig, die beispielsweise durch Strahlen erfolgen kann.

Allgemein ist das Strahlen von CFK-Teilen schwieriger als das von Metallteilen.

Während Letztere aus Vollmaterial bestehen und flächig gestrahlt werden können, handelt es sich bei CFK um einen Verbundwerkstoff aus Kohlefasern und Harz, der nur oberflächlich und sehr leicht gestrahlt werden darf. Zudem sollen hier nur die Klebeflächen partiell gestrahlt werden, was den Einsatz eines besonders präzisen Verfahrens notwendig macht.

D & S wendet hierbei eine besondere Strahltechnik an, deren Details der Geheimhaltung unterliegen. Dieses Verfahren ist aktuell im Rahmen der robotergestützten Serienbearbeitung von CFK-Bauteilen für einen großen deutschen Automobilhersteller im Einsatz.

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Institute of Lightweight Engineering and Polymer Technology

�� Excellence in Lightweight Design �� The Institute of Lightweight Engineering and Polymer Technology (ILK) at TU Dresden In keeping with Dresden’s long tradition as a centre for lightweight engineering, the Institute of Lightweight Engineering and Polymer Technology (ILK) at Technische Universität Dresden has now been active in the field of functionintegrative lightweight engineering founded on multi-material design for over twenty years. It is fully embedded in Dresden’s outstanding scientific and industrial landscape, which offers an optimum environment for innovative, pioneering research and development.

The ILK’s team of 240 employees carries out extensive research and development projects focusing on lightweight structures and systems for specific loading scenarios in a variety of sectors, for example aerospace engineering, vehicle manufacturing and mechanical engineering.

The institute’s work is founded on the Dresden Model of “function-integrative lightweight engineering in multi-material design”. Established in 1995, the model takes the entire value creation chain into account – from material selection, design, simulation and assembly to prototype testing, quality assurance and cost control. Its systematic, interdisciplinary approach to materials and products makes the model a benchmark and trailblazer for not only other research institutes, but also industrial high-tech companies.

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Technische Universität Dresden

and development, resulting in a comprehen­ sive knowledge matrix that sets us apart from our international competitors. What is more, the foundation of the DRESDEN concept research initiative has ushered in a new phase of simplified exchange between scientists and accelerated access to existing knowledge within the region.

Dresden – home to a new generation of lightweight engineering

The ILK boasts a broad range of specialist expertise thanks to its highly qualified workforce.

Employees range from mechanical engineers, materials scientists, electrical engineers and construction engineers to engineering mathematicians, computer scientists, physicists, industrial engineers, technicians and student assistants. Many of them are recruited from TU Dresden’s unique Lightweight Engineering programme, which yields around 80 graduates each year.

The Institute of Lightweight Engineering and Polymer Technology was founded by Prof.

Dr.-Ing. habil. Prof. E.h. Dr. h.c. Werner Hufen­ bach, who remained its Director until accepting the post of Distinguished Senior Professor in September 2014. TU Dresden appointed three highly qualified specialists of international renown as his successors, with the ILK now led by a four-strong board of management: Prof.

Dr.-Ing. habil. Maik Gude (Chair of Lightweight Design and Structural Assessment), Prof. Dr. rer. nat. Hubert Jäger (Chair of Lightweight Systems Engineering and Multi Material Design), Prof. Dr.-Ing Niels Modler (Chair of Function-Integrative Lightweight Engineering) and Prof. Dr.-Ing. habil. Werner Hufenbach (Distinguished Senior Professorship).

Dresden’s lightweight engineering landscape is characterized by a dynamic network of universities, research institutes and industrial partners. This cluster of expertise covers all disciplines throughout the field of material research

Having both emerged from in-house talent promotion programmes, Professor Gude and Professor Modler are now experienced scientists and ideally placed to continue the philosophy and traditions established over more

Institute of Lightweight Engineering and Polymer Technology

than 20 years of institute history. The board is further strengthened by the arrival of Professor Jäger, formerly Chief Officer Technology & Innovation at the SGL Group, who holds the newly created Chair of Lightweight Systems Engineering and Multi Material Design. His appointment gives the ILK all the benefits of a renowned lightweight engineering expert whose work at the institute will draw on practical experience gained within the framework of highly application-oriented commercial research. Professor Jäger’s dedication to lightweight engineering goes back many years, and he is regarded as a leading standard-bearer for the lightweight engineering sector.

institutes. The resultant pool of knowledge and experience guarantees the level of flexibility and rapidity required in order to fulfil the re­ quirements of specific industrial sectors.

The appointment of the institute’s new board of management coincides with the restructuring of scientific work at the ILK. Its expertise is now gathered into nine expert groups, each of which covers, investigates and expands fundamental fields of knowledge in the disciplines of materials science and lightweight engineering. This new structure empowers employees to place greater focus on their areas of specialization and develop tailored, high-quality solutions for our partners.

Main areas of research activity

The ILK draws on longstanding experience gained within the framework of both fundamental research and strictly application-oriented industrial research and development projects. Its workforce is characterized by minimal personnel turnover, thus significantly reducing losses in experience and specialist knowledge when compared with other university-based

All scientists at the ILK are characterized by a highly interdisciplinary approach. They cope with the increasing complexity of the tasks they face by applying not only their own expertise, but also the skills and knowledge of their col­ leagues and the institute’s scientific partners.

Their overriding aim is to tackle projects quickly, efficiently and, above all, sustainably. This in turn ensures the transferability of the institute’s research findings to industrial applications.

The ILK conducts cutting-edge research throughout the entire spectrum of lightweight engineering and polymer technology – from fundamental theory right through to practical solutions. Its researchers’ core expertise lies in not only the development, design and optimization of high-performance lightweight components and systems, but also the manufacturing of prototypes. All work is based on the Dresden Model, with multi-material design therefore playing a key role. Depending on the design brief involved, all classes of material – from steel, aluminium, magnesium and titanium to polymers, ceramics and composites with short/continuous fibre or textile reinforcement – can be taken into consideration and combined to deliver a set of tailored structural-technological characteristics.

Figure 1: The board of the ILK (from left to right): Prof. Dr.-Ing. habil. Prof. E.h.

Dr. h.c. Werner Hufen­bach, Prof. Dr. rer. nat. Hubert Jäger, Prof. Dr.-Ing. Niels Modler, Prof. Dr.-Ing. habil. Maik Gude

Technische Universität Dresden

11

Institute of Lightweight Engineering and Polymer Technology

Figure 2: 3D printer head.

A variety of joint interdisciplinary research projects in which the ILK has participated as an initiator and spokesperson have enabled the institute to gain comprehensive knowledge of the fundamental theory behind a range of materials, processes and technologies. Findings yielded by fundamental research feed directly into the development of innovative lightweight structures and corresponding serial manufacturing processes. The institute’s success in this area is reflected in the acquisition of substan­ tial third-party funding and longstanding re­ lationships with industrial partners.

The ILK cooperates closely with LeichtbauZentrum Sachsen (LZS) GmbH, LeichtbauSystemtechnologien KORROPOL (LSK) GmbH and GWT on the transfer of lightweight engineering innovations to industrial applications and serial manufacturing processes.

Internationalization The ILK has always built its research, academic and industrial partnerships on cooperation with leading international organizations, thus enabling the institute to both expand its portfolio of expertise and facilitate sustainable exchange between researchers and students. On a Euro­ pean level, the ILK has a tradition of close re­ lationships with research facilities in Poland and the United Kingdom. Further afield, the institute can already point to longstanding, close cooperation with Tongji University in the Chinese city of Shanghai. More recently, we

12

Technische Universität Dresden

have not only forged promising relationships with partner universities in Singapore and South Korea, but also strengthened our joint activities in the field of multi-material lightweight engineering.

In keeping with TU Dresden’s strategy of internationalization, the ILK plans to reinforce and expand its cooperation with European, Asian and North American research partners in the near future.

Generative manufacturing – a leading international technology of the future One of the key areas of research focus at the ILK is the targeted application of high-performance materials and the synergetic combi­­­ nation thereof to create multi-material lightweight structures characterized by efficiency in terms of both resources and costs. Set up by the Chair of Function-Integrative Light­ weight Engineering, the aim of the Innovation Lab for Generative Manufactu­ring is to es­ tablish generative manufacturing – a crucial bridge between bionic reinforcement struc­ tures, multi-material design and tailored fibre composites – as the leading international technology for the manufacturing of multilayered, multi-material composite struc­tures with load-specific 3D fibre reinforcement.

In particular, research and development in the field of generative manufacturing yields novel systems, series-ready process chains and re­

Institute of Lightweight Engineering and Polymer Technology

Figure 3: This high-speed radial braiding wheel with up to 288 bobbins makes it possible to braid tapes around forming structures of up to 4.2 m in diameter.

Photo: © Steffen Weigelt

liable process simulation techniques that pave the way for the processing of high-performance multi-material composites as part of serial production. The overriding aim is to combine the production of fibre-reinforced composites with conventional additive manufacturing techniques to form a continuous overall process.

Additive manufacturing offers a number of different ways to manufacture products effi­ ciently and with a high degree of design freedom. The breaking down of highly individualized, complex components into characteristic layers enables them to be produced on an automated, highly reproducible basis, with fused deposition modelling (FDM) currently one of the most successful options available. Until now, the use of unreinforced thermoplastics has nevertheless placed significant restrictions on the mechanical properties exhibited by com­­ponents manufactured using additive techniques. In order to facili­tate the 3D printing of thermoplastic materials with continuous fibre reinforcement, scientists working at the ILK’s Innovation Lab have developed a printhead adaptable to both the specific properties of fibre-reinforced composites and the demands placed on them. The novel print­head is the first to enable the 3D printing of commercial hybrid yarns, thus paving the way for the generative manufacturing of three-dimensional bodies with a high fibre volume ratio.

The ILK expands and enhances the Innovation Lab for Generative Manufacturing on a conti-

nuous basis, with a new, multi-functional preforming system set to enable scientists to manufacture complex 3D structures from thermoplastics with continuous fibre reinforcement. The system facilitates the rapid, simultaneous laying of multiple fibre-reinforced thermoplastic tapes.

Each tape is laid onto the forming structure in a way which ensures compliance with both application-specific loading and the shape of the target component. One goal pursued by the ILK’s researchers in this area is the one-step, wastefree manufacturing of an entire side panel for a car – including all necessary connection points for elements such as seatbelts, hinges and windows as well as functional components such as loudspeakers and lighting.

Facilities The ILK has a comprehensive range of modern equipment at its disposal. The institute’s ma­ chine park is the only one of its kind on the international research landscape, and provides a strong foundation for applied research and development. It includes the following facilities: ■ L aboratories for research into mechanical and physical material properties ■ CAE Training and Development Centre ■ Innovation Lab for Preforming and Generative Manufacturing ■ High-Speed Test Complex (incl. drop tower) ■ Prototype Testing Facility ■ Process Development Centre ■ Polymer Application Centre

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

Examples of series-oriented equipment available at the ILK include a long fibre injection (LFI) system (including a mould carrier), a two-part injection moulding system (clamping force: 2,300 tonnes) and a high-speed radial braiding wheel with a variable braiding eye.

The ILK’s manufacturing facilities are supplemented by a modern test laboratory featuring a CAT scanner specially designed for composite materials and structures. The scanner is the first to facilitate the in-situ capture of CAT images of samples and structural components under simul­taneous multi-axial loading. Its CAT equipment enables the ILK to play a leading interna­tional role in both research into and the development of lightweight material and structures.

The ILK continuously expands its facilities in order to maintain its ability to tackle increasing­ ly complex, application-oriented projects. To give an example, an integrated foaming head and an Arburg injection moulding system with a clamping force of 500 tonnes have recently been added to the institute’s machine park along with high-performance printers for polymers and metals. In addition to standard polymers, the polymer printers also enable scientists to process filled polymers and high-performance materials such as thermoplastics with continuous fibre reinforcement.

Teaching The ILK has now been teaching students on the unique Lightweight Engineering programme for almost 20 years. Its interdis­cipli­ nary, multi-material, multi-technology approach enables the institute to impart a broad range of both fundamental and specialist knowledge with a strong focus on practical applications.

The results of research carried out in coope­ ration with industrial partners feeds directly into taught content. Right from an early stage, students are integrated into the ILK’s forwardlooking research projects and gain insights into real-world applications as part of lectures delivered by recognized experts from the world of industry.

Ultra-lightweight engineering driven by novel, integrated automobile concepts The InEco ® project is an outstanding example of the development of integrated concepts,

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Technische Universität Dresden

and was initiated with the aim of designing a novel, forward-looking, sustainable vehicle concept. The results of the project were demonstrated with the aid of a generic project vehicle characterized by its integrated, multi-material design. More specifically, par­ ticipating scientists from the ILK designed and built a four-seater electric vehicle for the metro-urban environment in cooperation with experts from Leichtbau-Zentrum Sachsen GmbH (LZS) and ThyssenKrupp AG. The demon­­strator has a total weight of just 900 kilograms including all components and its bat­tery, and combines a sporty drive, environmentally friendly mobility and cost-efficient construction techniques with elegant design.

The vehicle concept significantly decreases the number of vehicle components required, and makes optimum use of available weight reduction opportunities.

The insights gained during the project form the foundation for the ILK’s proven vehicle design expertise, which has already been applied within the framework of projects such as SFB 639 (Textile-reinforced Composite Com­ponents for Function-integrating Multimaterial Design in Complex Lightweight Appli­cations).

The ILK’s experience and expertise in the field of lightweight engineering is by no means restricted to the automobile sector. The institute is also home to power systems manufacturer Rolls Royce’s University Technology Centre (UTC) for Lightweight Structures and Materials and Robust Design, which enables scientists to gain further experience in materials science and lightweight engineering for the aviation sector. In addition, the ILK has an extensive pool of knowledge and expertise in the fields of medical technology, mechanical engineering and rail vehicle technology – all of which is presented in this brochure.

In the future, the ILK plans to not only further enhance its know-how in the fields of avia­tion, space travel and the automobile sector, but also expand its expertise to in­­­­­ clude functionalization applications in the electric mo­­bility, biomedical engineering and sports equipment sectors. Another of the institute’s ob­jectives is to establish generative manu­­­­­­facturing based on fibre-reinforced composites as a leading international manufacturing technology.

GWT-TUD GmbH

›› ILK und GWT:

Gemeinsam auf dem Weg von der Wissenschaft zur Anwendung ‹‹

Die GWT-TUD GmbH hat sich das Ziel gesetzt, Forschungsergebnisse schneller in neue Verfahren und Produkte ein­ ­­zu­­­bringen. Als Dienstleister und kompetenter Partner für den Technologie­ transfer konzentrieren wir uns darauf, den Innovationsprozess zwischen Wis­ ­­senschaft und Wirtschaft so effizient wie möglich zu organisieren. In enger Ko­­­­­operation mit Wissenschaftlern, Uni­ ­­versitäten, Hochschulen, anderen For­ schungseinrichtungen und der Indus­ trie entwickeln wir Innovationen in in­terdisziplinären Projekten.

Dienstleistungen nach Maß Das Institut für Leichtbau und Kunststoff­ technik (ILK) an der TU Dresden unter der Leitung der Herren Professoren Maik Gu­ de, Hubert Jäger, Niels Modler sowie Se­ nior­­ professor Werner Hufenbach bindet die Dienstleistungen der GWT in seine Trans­­fer- und Industrieforschungs­projekte ein. Als Transferpartner des ILK unterstützt die GWT die Wissenschaftler einerseits bei der Überführung ihrer For­schungs­er­ geb­­ nisse in erfolgreichen Pro­ jekten mit aus­­­gewählten Industriepartnern. Anderer­ seits wirkt die GWT unterstützend in der Durchführung der akademischen Weiterbil­ dung für Fachingenieure oder Führungs­ kräfte zu Themen des Leicht­baus. Diese Projekte werden sowohl im In­­land als auch im Ausland unterstützt. Unser Support ist fo­­kussiert auf die kaufmännischen, juristi­ schen und personaladministrativen Stütz­

prozesse zur gesicherten und effektiven Um­­­­setzung der Pro­­jekte. Ebenso un­­ter­ stützt die GWT das ILK bei der Aus­gestal­ tung seines Innovationslabors für die ge­ nerative Fertigung. „Die GWT ist für das ILK ein wichtiger Part­ner bei unseren Trans­ feraktivitäten. Wir profitieren von ihrem Netz­­­werk und ihren professionell organ­ sierten Service­dienstleistungen. Die GWT bietet für unsere Anforderungen die not­ wendigen Ins­trumente und eine Flexibilität, um im Trans­­fergeschäft erfolgreich sein zu können“, sagt Prof. Gude vom ILK. GWT – ein flexibler Partner im Technologietransfer Bei der Anbahnung und Durchführung von Forschungsprojekten leistet die GWT pro­ fessionelle Unterstützung mit einem indi­ viduellen und bedarfsgerechten Zuschnitt.

Während sich Wissenschaftler hauptsäch­ lich auf ihre Forschungsaufgaben konzen­ trieren und ihr wissenschaftliches Projekt leiten, übernehmen wir das Management aller weiteren Prozesse von der Gestaltung der Verträge über die kaufmännische Ab­ wicklung bis hin zur Koordination von Wei­ terbildungsmaßnahmen. Im Gegensatz zu vielen anderen Transfer­einrichtungen kann die GWT mit der Schnel­­­­ligkeit und Flexibi­ lität eines Mittelständlers agieren, da es ein privatwirtschaftliches Un­­­­­ter­nehmen ist.

Die wachsenden Anforderungen in For­ schungs­­­­­­projekten können oftmals nicht nur von einem Experten allein umgesetzt wer­

den. Häufig sind sie das Ergebnis der Zu­ sam­­­­menarbeit der besten Spezialisten auf einem Fachgebiet, die ihre individuel­ len Stär­­­­­­ken einbringen. Aus diesem Grund bin­ ­­det die GWT Spitzenforscher in hochschul­ übergreifende Kompetenz­zen­tren und Netz­ werke ein. Oftmals beauftra­gen In­­dustrie­ un­ternehmen eher Kompe­tenz­­­zen­­tren mit meh­­­­reren Fachexperten als ein­­zelne Wis­ sen­­­schaftler. Die GWT hat Zu­­­­gang zu über 1600 zum Teil weltweit agie­­­renden Indus­ triepartnern.

Wenn Wissenschaftler für ihre For­schungs­ aufgaben eigene Forschungsstrukturen be­­­­­nötigen (z.B. Räumlichkeiten, Personal etc.), so erhalten sie auch dabei von den GWT-Experten professionelle Unterstüt­ zung: sowohl beim Aufbau als auch beim Management einer bedarfsgerechten Infra­ struktur. Die GWT ist auch Projektmanager auf dem Weg von der Idee bis zur Ver­ marktung. Denn: For­ schungsergebnisse sind das hohe Gut der Wissenschaftler.

Die GWT unterstützt dabei als verlässlicher Partner: von der Bewertung der Schutz­fä­ ­higkeit über die Anmeldung des Patent­ schut­­zes bis hin zur Verwertung einer Er­ findung durch Verkäufe/Teilverkäufe oder der Vergabe von Lizenzen.

KONTAK T

GWT-TUD GmbH Ansprechpartnerin: Jana Ulber Blasewitzer Straße 43 | 01307 Dresden Tel.: +49 (0)351 25933 168 jana.ulber@gwtonline.de www.gwtonline.de

Public Relations

Technische Universität Dresden

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Elbe Flugzeugwerke GmbH

›› Elbe Flugzeugwerke GmbH – EFW ‹‹ EFW hat drei Hauptgeschäftsbereiche: n d ie Entwicklung und Herstellung von Leichtbaukomponenten für alle AirbusModelle von der A320-Fa­ milie bis zur dop­­ pelstöckigen A380 und dem Lang­ streckenflieger A350 n d ie Umrüstung von Passagier- in Fracht­ flugzeuge n s owie die Wartung, Reparatur und In­ stand­setzung von Flugzeugen Die Engineering-Abteilung von EFW ist eine euro­päisch zertifizierte Entwick­lungs­organisa­ tion, die an der Erweiterung des gesamten Pro­ duktspektrums von EFW beteiligt ist. Das heutige Umrüstportfolio umfasst Airbus-Flugzeuge vom Typ A300-600 und A310. Künftig wird der Lang­streckenflieger A330 sowie der A320 das Spektrum erweitern. Auch das Geschäft der Flug­­zeugwartung baut EFW kontinuierlich aus.

Im Bereich der Flugzeugkomponenten reicht die umfangreiche Produktpalette von Fußboden­ plat­­ten über Innenaus­tat­tungskomponenten und Frachtraum­verkleidungen bis zu schussfesten Cock­pittüren. Das Produktportfolio umfasst dabei Sekundärstrukturbauteile ebenso wie Pri­ mär­­strukturbauteile.

Jeden Monat werden rund 25.000 Bau­teile gefertigt und just-in-time an die Montagelinien der Kunden geliefert.

Sowohl für das A380- als auch das A350Programm von Airbus entwickelt und fertigt EFW die Gesamtsysteme Fracht­raumverkleidung und Fußbodenplatten.

Auch im Bereich außerhalb der Luftfahrt erstrecken sich die Produkte der EFW, die Fuß­ bodenplatten für die neue Straßen­bahngeneration sowie Leichtbau Wand- und Deckensysteme wurden für den ma­ritimen Sektor entwickelt und erfolgreich als Serienprodukt etabliert.

ZERTIFIZIERUNGEN: Design n n n n n

D IN EN 9100 D IN EN 9110 D esign Organization: EASA 21J P roduction Organization: EASA DE 21G M aintenance Organization: EASA DE145

After Sales

Customer requirements

Certification

Leistungen: n n n n

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Z ugelassener Entwicklungsbetrieb F rachterumrüstung F lugzeugwartung Entwicklung

und Herstellung von Composite Flugzeugbauteilen

Technische Universität Dresden

Logistics

Manufacturing

Public Relations

Elbe Flugzeugwerke GmbH

Kundenanforderungen im Fokus der EFW Produktentwicklung

Die Anforderungen für unsere kundenspezifi­ sche Produktentwicklung basieren auf den Er­ fordernissen des Marktes. Dieser verlangt mit stetig wachsendem Druck nach innovativen Lö­­sungen und hat hohe Erwartungen an leichte und den­noch robuste und kostengünstige Luft­ fahrtbauteile.

Ein weiterer ganz wichtiger Aspekt ist die An­ forderung an eine ständig berei­­te und einsatzfähige Technik ohne Ein­schrän­kun­gen.

CFRP Fußbodenstrukturbauteil

Speziell in den letzten Jahren hat der Gesetzge­ ber dem Passagier eine Vielzahl von Ersatz­an­ sprüchen zugebilligt – unter anderem bei Ver­ spätungen im Flugverkehr.

Das hat natürlich erhebliche Auswirkungen auf die Rentabilität der Airline. Indem EFW entsprechende Produkte entwickelt, kommt sie dem Be­­darf der Kunden entgegen.

Time To Market ist ebenfalls ein wichtiges Krite­ rium, welches nur durch effektive Entwick­lungs­ abläufe erreichbar ist.

flap track fairing Demonstrator

Kontakt: Elbe Flugzeugwerke GmbH Grenzstraße 1 01109 Dresden www.efw.aero

Public Relations

Die luftrechtlichen Anforderungen an die zu ent­ wickelnden Bauteile bilden den verbindlichen, rechtlichen Rahmen, der dabei einzuhalten und nachzuweisen ist.

Alexander Knorr | New Products & Spares // Forschung und Entwicklung Tel.: +49 (0)351 8839 2541 | alexander.knorr@efw.aero

Frank Hörich | Head of Services Tel.: +49 (0)351 8839 2121 | frank.hoerich@efw.aero

Technische Universität Dresden

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�� FOREL: Electrifying

Lightweight Design ��

Maik Gude, Michael Müller, Michael Stegelmann

“The Centre for Research and Technology for Resource – Efficient Lightweight Structures of Electromobility” is a national comprehensive and independent platform with well-known partners participating in application-oriented technology projects. By offering pre-competitive and project-based exchange between partners while coordinating research projects, the cluster enables rapid development and transfer to industry. By accelerating the path to industry, the platform and its rapidly growing network will establish Germany as a world leading provider of lightweight components for electromobility.

Research Centre Communication Coordination

Technology Centre Competency Exploitation

1. Meaning of lightweight engineering in the electromobility 1.1 Objective The national platform of electromobility (NPE) defined six content-related flagship projects along the entire technology- and value chain in the third progress report [1]. One identified key element for a strategy of material and product innovations is function integrating systemic lightweight engineering in multi­material design.

Range and driving dynamics of electric vehicles are mainly affected by the mass and its distribution. Weight and price increase of an electric drive train can be compensated with intelligent lightweight solutions. Sustainable value chains in the electromobility – including a changed vehicle-package, ther­mal management and safety profile – can be achieved using a resource-efficient and affordable lightweight design in connection with innovative production technologies.

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Technische Universität Dresden

The cluster was established in 2013 under the coordination of the ILK. Suppor­ted by the German Federal Ministry for Edu­cation and Research (BMBF) and monitored by the Karls­ru­ he Project Management Agency (PTKA), FOREL brings together established German R&D centres with industrial leaders. By the end of 2016 FOREL has grown to a network of around 80 partners being active in nine complementary synergetic research projects. The structure and organisation of the platform is supervised by the ILK and its partners of the FOREL coordination project: Frei­berg University of Mining and Technology, Technical University of Munich, University of Paderborn and since December 2016 the Technical University of Dortmund.

1.2 Approach In contrast to the isolated and self-contained approach of topics (materials, processes, automotive engineering, …) in most research projects FOREL is based on a systemic and open

Institute of Lightweight Engineering and Polymer Technology

increases

unchanged

falls

Cast Iron

%

Steel

20

Unreinforced Thermosets

40

Unreinforced Thermoplastics

60

Ceramics

80

Titanium

Innovative lightweight technologies are often put on a level with the use of high performance materials, like carbon fibre reinforced plastics

Figure 1: Expectation of the future use of ma­terials in structural lightweight componentes in the next five years considering electromobility [2].

100

Magnesium

2.1 Material selection

To the extent that electromobility and the correspondingly extended specifications are introduced, current designs and methods of construction must also be subjected to scru­ tiny. Different approaches can be identified here. On one hand, it is attempted rapidly to serve and make inroads into the emerging

Aluminium

The scientists of the FOREL coordination project conducted a survey to identify trends, potentials and challenges for lightweight materials and manufacturing technologies. The questions were related to the FOREL topics forming and moulding technologies, joining and assembly technologies, recycling, quality assurance and process chain analysis. The results of the survey were brought together in a FOREL study. It is complementary to the third progress report of the NPE [3] highlighting the potentials of lightweight applications in the electromobility and names specific examples for funding future research and development projects.

2.2 Meaning for the electromobility

Reinforced Thermosets

2. Study

In recent years, fiber reinforced plastics (FRP) based on thermosets and their manufacturing processes, such as wet pressing and resin transfer molding (RTM) process have emerged as major trends in the auto industry. Fast-curing resins and new plant technologies have given the processes industrial-scale capability. As a complement to the thermoset FRP, techno­ logies based on thermoplastic FRP have also become significantly more ma­ture in recent years (Figure 2). In particular, the possibility of using established manufacturing techniques such as compression and injection moulding for processing thermoplastic textile semifinished products is a topic of many research projects. Assessing the potential of such combined processes is also being looked at by the FOREL study.

High-Strength Steel

FOREL significantly ads value for the partners in offering comprehensive tools for the systemic process-chain analysis and evaluation as well as continuous trend analyses concerning challenges, potentials and chances for lightweight tech­ nologies in the electromobility as shown in the “FOREL-Studie” [2]. This is the basis of future projects and the strategically positioned research-roadmap that is continuously updated in cooperation with the NPE. The key for the success of FOREL are an intensive collaboration between science and indus­try, the transdisciplinary cross-linking of the FOREL technology projects as well as the close national association of projects in the fields of elementary and application oriented research. In FOREL the fundamental multi-layered understanding is complementary to the know-how about a successful technology transfer.

(CFRP). The results of the study emphasize that this trend is just a small part of the current developments. The OEMs surveyed in the FOREL study expect a diverse mix of materials in the future, in which, besides reinforced and unreinforced plastics, metals and high-strength steel will also retain their places (Figure 1).

There is thus de facto no single “lightweight material of the future.” Those suppliers and manufac­turers with flexible, resource-efficient process chains and material-appropriate joining pro­cesses are thus best equipped to tackle the emerging challenges.

Reinforced Thermoplastics

approach. On a broad scientifical and industrial fundament a holistic development- and technology-network is established. FOREL identifies needs for technology-orientated research and transfers solutions for lightweight engineering – that have been adapted for electromobility – into industrial practice. Thus, several process chains are being developed, implemented and interlinked to a process network within a central technology centre. FOREL unites the competen­ cies about fibre reinforced plastics, light metals and steel as well as their hybrid composites in bringing German companies and research institutes together.

no data

Technische Universität Dresden

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Series-Availability of Electromobility

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Figure 2: Look back and forecast of the thermo­ set and thermoplastic development in the industrial practice: The technology readiness level of the thermoplastic composites significantly caught up [4].

Established in Large Series

Steel und Light Metals Thermoset Composites

Large-Series Components

Thermoplastic Composites Mutimaterial-Design

©ElringKlinger

TechnologyIndustrialisation Industrial Semi-Finished Production

Organic Sheets 2010

2015

2020

markets. To this end, only minor adaptations are made to conventional vehicle concepts (“conversion design”). However, the principle of “fuel tank out, battery in” is often at the cost of the weight balance.

Consequently, the auto industry is already employing complete redesigns (“purpose design”). Though this requires an immense development and logistics effort, it permits designs that incorporate the changed boundary conditions and provide “best case” solutions.

Thus, the FOREL scientists are systemically analysing the application of lightweight technologies in future electric vehicles (Figure 3).

Conversion Design

Functional Enhancement Exisiting Technologies and LogisiticChains

Low DevelopmentRisk

20

Technische Universität Dresden

Lightweight Potential

Sustainability Ressource Efficiency Future Perspective Low Investment

Design Freedom Function Integration

Degree of Innovation

Purpose Design

Figure 3: Purpose and conversion design of electric vehicles [2].

2025

Year

With this interdisciplinary evaluation of crosslinks the FOREL study identifies the “tech­­ nological gaps” in value chains. In order to address growing trends the study includes an in-depth analysis of the actual state and the expected developments from industry and science concerning lightweight technologies for the electromobility. In this context the study highlights developments that go beyond the three phases – pre-market, market-ramp-up, mass-market – defined by the NPE. To accompany and support the NPE’s technological de­velopment goals FOREL pursues a scien­­tific approach always taking lightweight-technologies into account.

One of the main conclusions of the FOREL study is that the automotive industry will not succeed in making the electromobility compe­ titive while counting only on simple conversion designs. The purpose design of new vehicle architectures and manufacturing processes is inevitable to fulfil the changing and linked demands. Besides standardised design and simu­lation methods a flexible combination of manufacturing processes is necessary. The goal is to provide holistic developments such as one-shot-processes of hybrid components for all vehicle classes with a relevant economic efficiency. This includes material adapted repair concepts and recycling strategies. This is due to the fact that next to economic effi­ ciency the ecology has a superior role. New manufacturing tech­nologies will only be transferred to industrial production when the carbon footprint permits. Therefore Life-Cycle-Assess­

Institute of Lightweight Engineering and Polymer Technology

ment (LCA) is addressed in FOREL as well in order to use this ideal tool for an objective evaluation besides the system boundaries.

3. Selected highlights of the FOREL network

Magnesium

LITECOR®

CFRP Magnesium

3.1 Metal intense lightweight design in the LEIKA project In the research project LEIKA (“ResourceEfficient Hybrid Design for Lightweight Car Bodies”) a hybrid metal-composite floor structure concept for electric vehicles was deve­ loped (Figure 4). The joint project was led

by TechCenter Carbon Composites of the thyssenkrupp AG. The special focus of the project was put on an intelligent use of materials like magnesium, steel and thermoplastic CFRP. The floor structure for electric vehicles is being used to demonstrate not only the potential offered by hybrid materials within the context of lightweight applications, but also the technological maturity/feasibility of a combined moulding and back injection process for series production.

Participating scientists combined steel or magnesium outer layers with a carbon-fibre-reinforced PA6 core to create novel hybrid mate­ rials. With this approach those sandwich structures combine the beneficial characteristic and technological properties exhibited by the two materials. In addition to efficient, applicationoriented structural design methods which take into consideration both, static and dynamic loading, particular emphasis was also placed on the development and refinement of manufacturing technologies based on the combina­ tion of two conventional processing techniques – moulding and back injection. In addition to that adapted joining technologies were deve­ loped to connect the floor panel and the seat cross-members with the battery-tunnel. The whole floor concept was extensively simulated, tested and finally compared with a metal reference structure leading to a predicted 25 percent reduction in weight.

3.2 Development of recycling adapted manufacturing technologies within the ReLei project The future intelligent use of FRP for electric vehicles is driven by political constraints as well as social and long-term economic and ecological interests. Owing to an increasing demand for resource efficiency, the integra­tion of a recycling

PA-GF Steel CFRP

CFRP

Magnesium

Steel

CFRP

strategy into the process development will gain in importance. The ReLei project (“Manu­fac­ turing and Recycling Stra­tegies for Fibre Rein­ forced Hybrid Light­weight Structures”) adopts an interdisciplinary approach treating the recycling as a central reference point for all development steps, while conventional methods usually see it as a downstream process.

Figure 4: LEIKA demonstrator: Hybrid floor structure with an integrated battery tunnel. Photo: © ThyssenKrupp AG

The project aims to develop an innovative manufacturing process and an integral recycling strategy for function integrative lightweight structures for future electric vehicles. In order to realise a sustainable material mix in future electric cars, a novel process for recovery and re-use of carbon fibres will be designed that is based on existing disassembly and separation technologies. The secondary material is re-used for functionalised structural parts manufactured by foam forming. The technology integrates CFRP top layers into conventio­nal injection moulding. The necessary forming force is applied by the gas-containing polymer melt.

As a consequence, an integral foam structure can be realised in a highly effi­cient manufacturing process. The project is led by ElringKlinger.

3.3 Development of innovative lightweight bearing structure in the FuPro project A modular combination of torsionally and bending rigid hollow profiles with complex nodes and planar structural elements represents a target-aimed approach for a load specific design of lightweight bearing structures.

While the integrative processing of planar reinforced structures and fluid moulding com-

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

Figure 5: Battery carrier.

materials

machines

properties ID stiffness ... ...

intermediate product

recycling

pounds, e.g. for ribbed structures, can be expected to enter large scale production soon, hollow profiles containing continuous fibres are still far away from being integrated into the idea of a modular assembly system.

The FuPro project (“Design and Process Development for Functionalised Multi-Compo­ nent Structures with Complex-Shaped Hollow Profiles”) aims to develop and analyse a novel large scale manufacturing process for lightweight structures made of complex FRP hollow profiles, organic sheets and injection moulding compounds. The novel architectures shall enable a largely increased level of process, structural and functional integration as well as improved design freedom for electric cars. Substantial advancements compared to the state of the art are targeted all along the process chain. As a result it is planned to build up a manufacturing complex providing pioneering process reliability, resource effi­ ciency and profitability. The availability of a modular assembly system consisting of planar and hollow structural elements made of thermoplastic FRP as well as the process related

Technische Universität Dresden

process B

process A

Figure 6: Visualisation of a process chain.

22

part

linking of primary and secondary forming steps to one single and fully automated overall system enables a cost-efficient large scale production of structural parts. Lead partner of the project is brose Fahrzeugteile.

The potential of the FuPro technology was successfully proven in the preceding project “e-Generation” by the prototype of a battery carrier, which was honoured by the “In­dus­trie­­­ vereinigung Verstärkte Kunst­stoffe e.V.” with the AVK innovation award in 2015 (Figure 5).

3.4 Links in the process network Within the framework of FOREL the NPEdriven systemic approach is addressed by the use of process chain modelling. According to [5] the method is based on a software tool providing visualisation and analysis of technological relations. It is applied to manufacturing and assembly processes aiming at the manufacturing of single components and complex systems. For this purpose sub-processes are linked on different levels. Besides production planning and design of experiments it allows

Institute of Lightweight Engineering and Polymer Technology

planning of resources by combining material and ma­chine databases. Based on the documentation of relevant parameters, an analy­­sis of status changes during the process or the process chain is performed. This enables a detailed study of the relationship between process parameters and part properties. Through­ out this procedure several statistical methods can be applied. Essential advantages of this method are the unified visualisation (Figure 6) and the systematic evaluation of varied and complex amounts of data like ma­­terial properties, ma­chine data, measurements, process times or investment and personnel costs.

Furthermore, it is favourable to inte­grate economic evaluations and tools like the LCA directly into the modelling of process chains. By doing this, inherent demands of the automo­ tive industry can be taken into account. The process chain analysis has al­ready been proven successfully for technology development and quality control purposes in complex processes like the manufacturing of FRP components [5].

In order to identify and evaluate gaps in complex and interdisciplinary process chains an open and cross-technological detection of all relevant data and information is required. The process chain analysis with its generalised approach may substantially contribute to this.

In order to exploit the full potential, an early definition of unified interfaces and target values has to be ensured.

The demand profile of chain oriented pro­ duction technologies is constantly changing because of the dynamic environment of the involved companies. Enterprises therefore

have to use effective and efficient technologies being suitable to future demands, too.

Consequently, the FOREL coordination project targets to identify alternative potential technologies with regard to the technological needs and bring them to maturity phase.

Contact

4. Conclusion Driven by the current trends in lightweight engineering, developers are forced to think out of the box if they want to be successful in future. Suppliers, OEM and research insti­ tutions have to ally with each other and collaborate to be able to efficiently cover the complex value chains. For instance already today substantial questions like the supply with carbon fibres and the provision of valuable and reproducible preforming processes are outsourced and accomplished by trustworthy development partners. As a consequence, also future market leaders will substantially depend on know-how transfer. Research institutions and open platforms like FOREL will play a major role in this context.

Prof. Dr.-Ing. habil.

Maik Gude Scientifical head of FOREL and the Chair of Lightweight Design and Structural Assessment at the ILK Phone: +49 (0)351 463 38 153 maik.gude@tu-dresden.de

Besides the initiation of further FOREL research projects bridging current technological gaps, the automotive industry will also need appropriate forms of education. Novel flexible education being dedicated not only to engineers, but also to technicians and more ex­ perienced employees is urgently required.

A good example for such an approach is the FOREL Academy. Only if current and interdisciplinary knowledge is widely available, a contribution to the ambitious aims of the NPE can be achieved.

Funding

Literature

The German Federal Ministry of Edu­ cation and Research (BMBF) funds the research and development project FOREL within the Framework Concept “Research for Tomorrow’s Production” (funding code 02PJ2760 – 02PJ2763 and 02P16Z010 – 02P16Z014). FOREL is managed by the Project Management Agency Karlsruhe (PTKA).

[1] Nationale Plattform Elektromobilität: Fortschrittsbericht der Nationalen Plattform Elektro­ mobilität (Dritter Bericht), 2012.

[2] Gude, M., Lieberwirth, H., Meschut, G., Zäh, M., Müller, M., Stegelmann, M., et. al.: FOREL-Studie – Chancen und Herausforderungen im ressourceneffizienten Leichtbau für die Elek­tromobilität, ISBN 978-3-00-049681-3, 2015.

[3] Nationale Plattform Elektromobilität: Fortschritts­­bericht 2014 – Bilanz der Marktvorbereitung, 2014.

[4] Müller, M., Stegelmann, M., Gude, M.: Elektrisierender Leichtbau – Chancen und Heraus­ forderungen im ressourceneffizienten Leichtbau für die Elektromobilität, Kunststoffe, 2 (2016) S. 22-28.

[5] Großmann, K.; Wiemer, H.; Großmann, K. K.: Methods for modelling and analysing process chains for supporting the development of new technologies. In: Procedia Materials Science 2 (2013), S. 34–42.

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

�� University Technology

Centre Dresden – LIGHTWEIGHT ENGINEERING FOR Rolls-Royce �� Maik Gude, Albert Langkamp

Power systems manufacturer Rolls-Royce clusters its research activities at University Technology Centres – or UTCs for short – at specially selected universities around the globe. Each UTC is synonymous with cutting-edge scientific research in specific areas of engineering. Technische Universität Dresden is home to the UTC for Lightweight Structures and Materials and Robust Design, which not only drives progress in the fields of integrated lightweight engineering, multi-material design and robust design, but also promotes the transfer of fundamental research findings to industrial appli­cations at Rolls-Royce.

Figure 1: Opening of the Rolls-Royce University Technology Centre in Dresden in 2006: Prof. Dr.-Ing. habil. Werner Hufenbach (ILK), Colin Smith (Rolls-Royce), Prof. Georg Milbradt (Prime Minister of the Free State of Saxony) and Prof. Herrmann Kokenge (Vice-Chancellor of TU Dresden).

Photo: © TUD/Eckold

The Rolls-Royce Group is one of the world’s leading manufacturers of power systems for the civil aviation and land and marine mobility sectors. The group has cooperated closely with Technische Universität Dresden on a variety of research projects since 1994, and in 2006 selected the university as the location of the newly founded UTC for Lightweight Structures and Materials and Robust Design.

Additionally, the composite university technology partnership (UTP) – a partnership between the Advanced Composites Centre for

Innovation and Science (ACCIS) at the Uni­­ versity of Bristol and the Institute of Light­ weight Engineering and Polymer Technology (ILK) at TU Dresden – was initiated by RollsRoyce in 2012.

The Rolls-Royce research and development network comprises 31 UTCs around the globe, and is supplemented by additional partnerships with research organizations such as the Fraunhofer Institute and institutes affiliated to the German Aerospace Center (DLR). The group’s network also includes prestigious uni­ ver­sities such as Imperial College (London), the universities of Oxford, Cambridge and Bristol, Purdue University (USA) and Nanyang Tech­nological University (Singapore).

All four of the ILK’s chairs take an active role in UTC Dresden. The majority of work carried out in cooperation with Rolls-Royce is supervised by Prof. Dr.-Ing. habil. Maik Gude (Chair of Lightweight Design and Structural Assess­ ment), with additional support and expertise provided by Prof. Dr. rer. nat. Hubert Jäger (Chair of Lightweight Systems Engineering and Multi Material Design), Prof. Dr.-Ing Niels Modler (Chair of Function-Integrative Light­ weight Engineering) and Prof. Dr.-Ing. habil.

Prof. E.h. Dr. h.c. Werner Hufenbach (Dis­ tinguished Senior Professorship).

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Technische Universität Dresden

Institute of Lightweight Engineering and Polymer Technology

Other participants in UTC projects include the Chair of Turbomachinery and Jet Propulsion (under Prof. Dr.-Ing. habil. Ronald Mailach), the Chair of Thermal Power Machinery and Plants (under Prof. Dr.-Ing. Uwe Gampe), the Chair of Materials Technology (under Prof.

Dr.-Ing. Christoph Leyens) and the Chair of Machine Elements (under Prof. Dr.-Ing. Bert­ hold Schlecht).

The UTC for Lightweight Structures and Ma­­terials and Robust Design not only drives progress in the fields of integrated lightweight engineering, multi-material design and robust design, but also promotes the transfer of fundamental research findings to industrial applications at Rolls-Royce. It sees Rolls-Royce and UTC Dresden cooperate closely with Leicht­­­bau-Zentrum Sachsen GmbH (LZS) – a strategic partner and sub­ sidiary of TU Dres­­­­den AG – on not only the development of novel technological methods, materials and components, but also the validation thereof as part of homologation. That cooperation facilitates the efficient realization of complex development processes which begin at laboratory scale (Technology Readi­ ness Level (TRL) 1) and yield air- or roadworthy components (TRL 6). In addition to their joint research and development work, UTC Dresden and Rolls-Royce also cooperate on both the rapid solution of in-service problems and the education and training of students, engineers and scientists alike.

The UTC carries out a broad range of re­­­ search and development work within the frame­­work of publicly funded regional, na­ tional and international research projects.

To give an example, the joint project KoLiBri (Complex Light­weight Intermediate Cases of Fibre-Reinforced Composite Construction for Next-Generation Turbofan Engines) sees the ILK develop design and manufacturing methods for thick-walled, complex, highly loadable lightweight structures consisting of carbon fibre-reinforced polymers. Funded by the Federal Ministry for Economic Affairs and Energy (BMWi) as part of the Federal Aero­nautical Research Programme (LuFo), the project focuses on the use of fibre-reinforced polymers as a means of sig­nificantly reducing the weight of power system components. New design strategies and manufacturing pro­cesses are being de­veloped for three core components: drive shafts, intermediate

cases and burst con­tainment housings.

In one example, a newly developed radial drive shaft characterized by the targeted combination of fibre-reinforced polymer and metal structures paves the way for optimized engine shapes accompanied by a significant increase in efficiency – and with it fuel savings.

The enhanced integration of a variety of subsystems into the innovative thrust re­­verser system developed as part of the LuFo project SuSi (System Integration of Thrust Reversers) contributes towards reductions in engine size. The upshot is a considerable boost in the profitability and environmental compatibility of aircraft engines. Participating researchers have developed a simplified predesign method for polymer-based components, thus facilitating significant improvements in both the speed and quality of the development process.

Figure 2: This fibre-reinforced composite radial shaft was jointly developed by the ILK and LZS and won the Rolls-Royce Engineering Innovation Award. The highly loadable CFRP engine shaft is not only able to cope with 30 percent more revolutions per minute than a conventional steel shaft, but also offers the benefit of a 20 percent reduction in mass.

The technology behind the shaft is currently being transferred to a Rolls-Royce supplier in Saxony.

In addition to research at regional and national level, international projects funded by the Euro­­ pean Commission offer an especially fruitful opportunity to cooperate with recognized aircraft engine experts from other EU member states on the enhancement of the environmental compatibility of civilian engines in terms of not only the emission of greenhouse gases and nitrous oxides, but also noise pollution. The LEMCOTEC (Low Emissions Core Engine Tech­ nologies) and E-BREAK (Engine Break­through Components and Sub­systems) projects are two examples, and see the ILK work jointly with the Chair of Turbo­machinery and Jet Propulsion on

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

long-term cooperation with leading interna­ tional research institutes. Researchers at TU Dresden already enjoy the benefit of longstanding partnerships with scientists at Imperial College (London) and the universities of Oxford and Bristol. Students and doctoral candidates also profit from these strong relationships, and can opt to spend either a few months or an extended period studying and conducting research at a partner university. Over 150 students have already taken advantage of this excellent opportunity for exchange.

Figure 3: Test bench for blade rubbing.

Photo: © Steffen Weigelt

Contact

Dr.-Ing. Albert Langkamp Researcher at the ILK and UTC Coordinator Phone: +49 (0)351 463 38 151 albert.langkamp@ tu-dresden.de

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Technische Universität Dresden

the development of computational and experimental compressor optimi­zation methods. The project objective is ex­tremely complex in both cases, with participating scientists required to not only investigate enhanced compressor blade geometries, but also study both interactions between rotating and non-rotating compressor components and the kinematics of blade adjustment systems. Even the development and installation of suitable test benches re­presents a consider­able challenge, and our suite of precision test benches sets us apart from other European research facilities in this regard. Experiments carried out using our modern test benches combine with advanced simulation techniques to deliver vital insights into the deformation of turbine blades when they come into contact with the surrounding case.

This type of “contact phenomena” may occur when turbine blades are exposed to consider­ able forces due to the aircraft climbing steeply or making a hard landing. Among other outcomes, research carried out in this area at UTC Dresden has already yielded a compressor design strategy that serves as a practical decisionmaking tool during the development of new, smaller core engines at Rolls-Royce.

The global UTC network offers participating scientists an outstanding chance to initiate

In addition to the aforementioned benefits, the UTC network also gives graduates a variety of excellent career opportunities. To date, over 60 graduates from TU Dresden have been re­ cruited by either Rolls-Royce itself, one of the group’s suppliers or another research partner.

Graduates have also used experience and know-how gained within the framework of UTC-based cooperation to set up spin-offs.

The network has already provided a platform for over 150 joint projects in the fields of avia­ tion and marine navigation, with up to 100 scientists and technicians from TU Dresden involved at any given time. Its success makes the expansion of the UTC network an attrac­ tive option, with drive systems for rail vehicles a particular area of interest.

About Rolls-Royce The Rolls-Royce Group is a leading global manufacturer of power systems. Its German operations are spread across more than a dozen locations and employ the group’s second-largest workforce (after the United Kingdom).

Rolls-Royce Germany is the only German aircraft engine manufacturer licensed to develop, manufacture and maintain modern jet turbine engines for civilian and military aircraft.

Since 1990, the firm has followed a consistent strategy of investment in its German employees, programmes and sites – thus making a sustainable contribution to the development of the Ger­ man aviation sector.

A&M Kinzel Siebdruckmaschinen Ltd.

››Was es so alles für den Druck gibt...‹‹ Böttcherstraße 7 – seit März 2016 das neue Domizil der Firma A&M KINZEL. Auf ca. 2000 qm Produktionsfläche wer­­den Siebdruck-, Digitaldrucklinien, Laserschneid­ systeme, Weiterbear­bei­tungsmaschinen Rolle zu Rolle/Bogen sowie weitere Ma­ schinen um den Druck gefertigt. Eine Ver­ größerung der Produktionsfläche wurde not­­wendig, da sich nicht nur die Format­ größen verändert haben, auch die Auswahl der Druckwerktypen wurde erweitert. Im Hause KINZEL werden alle drei gängigen Druckwerksysteme im Siebdruck (Flachbett, Zylinder und Rotation) für die Herstellung von unterschiedlichsten Produkten im grafischen und technischen Bereich angeboten. Nicht zu vergessen die „Maschinen um den Siebdruck“, z.B. vollautomatisch arbeitende Rakel-Schleifmaschinen, Sieb-

Beschichtungsautomaten (auch für die Be­ schichtung von mehreren Sieben gleichzeitig), Flach- und Rotationsstanzen, Längsund Querschneider für Rollenmaterial, Trans­ fer-Maschinen für die Übertragung auf unterschiedlichste Träger sowie Spe­ zialkonstruktionen, die nach Vorgabe des Kunden hergestellt werden.

Eine weitere Neuentwicklung neben den A&M KINZEL Laserschneidsystemen ist die jetzt vorgestellte eigene Rolle zu Rolle Digitaldrucklinie, die mit großem Interesse von der Kundschaft erwartet wurde. Dieses Digital-Drucksystem mit „single pass“ Kon­ zept wird angeboten mit einer Auflösung von 600x600 dpi oder auch mit 1200x1200dpi. Es können 4 Farbmotive mit einer Druck­ geschwindigkeit von bis zu 70 bis 110 Meter pro Minute produziert werden. Es eignet

sich für bedarfsorientierte Klein- und Großaufträge. Momentan steht eine Digi­ taldrucklinie zur Vorführung im Werk (Bött­ cherstr. 7) in Bielefeld bereit.

Zur Zeit befinden sich Maschinen zur Fer­ tigung von flexiblen Batterien in der Fer­ tigstellung. In diesem Turnkey Projekt werden Drucklinien, Lasersysteme und andere Weiterbearbeitungsmaschinen integriert.

Die gesamte Ausrüstung (alle Maschinen) des Auftrages werden im Hause A&M KINZEL aufgestellt, sodass der Kunde nach Fertigstellung eine Abnahme der bestellten Maschinen unter Produktionsbedingungen durchführen kann.

A&M KINZEL Maschinen werden weltweit für die Herstellung von unterschiedlichsten Produkten eingesetzt.

Seit 1993 der Ansprechpartner für Siebdruckund Weiterverarbeitungslinien (Rolle zu Rolle) Unser Produktprogramm umfasst u.a.

■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■

Flachbett-, Zylinder- und Rotativ-Siebdruckmaschinen Digitaldruckmaschinen Rolle zu Rolle/Bogen Laserschneidsysteme Rolle zu Rolle/Bogen Flachstanzen, Rotationsstanzen Heissluft-, UV- und IR-Trockner Längs- und/oder Querschneider Kontrollgeräte Beschichtungsgeräte Entschichtungsgeräte Entwicklungsgeräte, Waschanlagen Rakelschleifmaschinen Heißtransferpressen Sondermaschinen (z.B. gedruckte Batterien)

2-Farben-Flachbett-Siebdrucklinie (Rolle zu Rolle) mit Vorkonditionierer und Puderstation

A&M KINZEL Siebdruckmaschinen Ltd. Böttcherstraße 7 D-33609 Bielefeld

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info@kinzel-am.com www.kinzel-am.com

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Arburg GmbH + Co KG

›› Profoam: physikalisch

geschäumte Leichtbauteile ‹‹

Leichtbauteile sind für viele Branchen und Anwendungen interessant. Zu den Highlights, die der Maschinenbauer Ar­­­burg auf der Messe K 2016 am Bei­ spiel einer Automobil-Anwendung prä­ ­­­sentierte, zählte die Schäumtechnik Profoam. Mit dem innovativen Leicht­ bau-Verfahren produzierte eine hyd­ raulische Spritzgießmaschine All­roun­ der 630 S Strukturdeckel mit Hoch­­ glanzoberfläche für das Pkw-Interieur.

Beim physikalischen Schäumen mit Pro­ foam wird das Kunststoffgranulat bereits in einer Granulatschleuse vor der Spritz­ einheit mit gasförmigem Treibfluid ange­ reichert. Zum Einsatz kommt eine Plasti­ fiziereinheit mit standardmäßiger DreiZonen-Schneckengeometrie. Während des Plastifizierungsvorgangs löst sich das Treib­ gas in der Schmelze und tritt erst mit dem Druckabbau beim Einspritzen in Form von mikrozellularen „Bläschen“ wieder aus.

Durch eine dynamische Werkzeugtemperie­ rung lässt sich trotz Schäumtechnik eine hochglänzende Oberfläche erzeugen.

Strukturdeckel mit Hochglanzoberfläche Ein hydraulischer Allrounder 630 S mit 2.500 kN Schließkraft produzierte auf der Messe K 2016 mit einem solchen dynamisch tem­ perierten Werkzeug in einer Zyk­­­­­luszeit von rund 60 Sekunden einen Strukturdeckel aus glasfaserverstärktem Polycarbonat für das Pkw-Interieur. Die Hand­­habung über­ nahm ein lineares Robot-System Multilift Select. Das Sichtbauteil mit einer Wand­ stärke von nur 1,8 Milli­me­tern wurde konse­ quent schäum­­gerecht ausgelegt. Mit rund 213 Gramm ist der Strukturdeckel daher insge­samt rund 24 Prozent leichter als ein ver­gleichbares Kom­paktbauteil mit 2,5 Milli­ ­meter Wandstärke. Daraus ergibt sich ein deutlich reduzierter Materialeinsatz.

Neue Granulatschleuse Für die kontinuierliche Zufuhr von Material und Treibfluid sorgt eine patentierte Gra­

28

Technische Universität Dresden

nulatschleuse mit zwei Kammern, die über einen Verschlusskegel getrennt bzw. ver­ bunden werden. Die untere Speicherkam­ mer steht kontinuierlich unter Treibfluid­ druck, während der Druck in der oberen Schleusenkammer zwischen Umgebungsund Treibfluiddruck wechselt. Beim Füllen der oberen Kammer mit Granulat ist der Verschlusskegel zur unteren Kammer ge­ schlossen. Sobald Granulat aufgefüllt ist, wird die Materialzufuhr abgesperrt und Treib­­fluiddruck aufgebaut. Die Drücke und Temperaturen in der Plastifiziereinheit er­ höhen die Sorptionsgeschwindig­keit des Treibfluids in der Schmelze. Erst beim oder kurz nach dem Einspritzen in das Werkzeug tritt das Gas in Form mikrozellulärer „Bläs­ chen“ wieder aus, die beim Erstarren der Schmelze „eingefroren“ werden. Ergeb­ nis­­­se sind, abhängig von Material und Nuk­ leierungsverhalten, eine weitgehend ho­ mogene Schaumstruktur und eine deutlich reduzierte Bauteildichte. Neu im ArburgPort­folio ist eine fünf Liter fassende Gra­ nulatschleuse für Spritzein­ heiten der Größen 1300 bis 4600. Damit erweitert sich das Einsatzspektrum von Pro­­ foam deut­­lich hin zu größeren Auto­motive-Bau­ teilen. Die Ein-Liter-Variante gibt es weiter­ hin für Spritzeinheiten bis zur Größe 800.

Faserverstärkte Kunststoffe schonend verarbeiten Da eine herkömmliche Drei-Zonen-Schnecke eingesetzt wird, eignet sich Profoam sehr gut für die schonende Verarbeitung von faserverstärkten oder empfindlichen Ma­ terialien. Bedingt durch die Schnecken­geo­ metrie und die reduzierte Viskosität des

Materials können im Bauteil sogar höhere mittlere Faserlängen als im Kompakt­spritz­ guss erreicht werden.

Einfache Prozessführung Profoam zeichnet sich durch eine einfache Prozessführung aus. Das zum Schäumen er­­ forderliche einphasige Gemisch aus Poly­­­merschmelze und Prozessgas lässt sich auf konventionellen Spritzgießma­schi­nen mit geringem technischem Zu­satz­­­auf­ ­­wand erzeugen. Der abgeschlosse­ne Auf­ bau des Systems mit einer von Arburg ent­­­wickelten eigenen Steuerung erlaubt den Ein­­satz des Geräts an verschiedenen All­rounder-Spritz­gießmaschinen. An der Steu­­­­erung der Gra­nu­­latschleuse, die über eine Schnitt­­stelle mit der Selogica-Maschi­ nen­steue­rung kom­­­muniziert, muss zusätz­ lich nur der variable Parameter „Prozess­ gas­druck“ ein­­gestellt wer­­den. Aufgrund der reduzier­­­ten Vis­kosität der gasbelade­ nen Schmelze kön­­nen die Spritzgießmaschi­ nen mit geringerer Zu­hal­tekraft und Ein­ spritz­­­drücken gefahren werden, was den Ener­giebedarf reduziert. Durch die kürze­ re Zy­­k­­luszeit wird das Ver­fahren wirtschaft­ lich. Im Vergleich zu Teilen, die im Kom­ pakt­­­spritzgießen her­gestellt werden, lässt sich eine signifi­kante Ge­wichts­reduzierung erreichen. Mit Pro­­­foam gefertigte Bauteile mit ihren feinen Zell­struk­tu­­ren weisen ne­ ben dem geringeren Gewicht auch we­­ni­ ger Einfallstellen, Verzug und inne­­re Span­ ­nungen auf. Auch unterschiedliche Wand­ stärken sind möglich. Ab­­hängig vom Ma­­­­­­­­te­­rial kann die Ober­flä­chenqualität durch eine dynamisch tem­perierte Prozess­füh­ rung weiter verbessert werden. www.arburg.com

Ein hydraulischer Allrounder 630 S fertigte auf der K 2016 in einer Zykluszeit von rund 60 Sekunden im Profoam-Verfah­ ren einen Strukturdeckel (Firma Covestro) für das Pkw-Interieur.

Foto: ARBURG

Public Relations

Compositence GmbH

›› Generative Fertigung mit Compositence RoboMAG-T‹‹ Die automatische Preforming-Anlage Ro­­­bo­­­MAG-T von Compositence zur ziel­ ­­­gerichteten Ablage thermoplastischer (Carbon) Tapes wurde im Dezem­ber 2015 im Innovationslabor für generative Fer­ tigung des Instituts für Leichtbau und Kunststofftechnik (ILK) der TU Dres­­­­den installiert und in Be­ trieb genommen: Fa­­serverbund­struk­turen in Ver­­bindung mit einer thermoplastischen Matrix gewinnen – bedingt durch ihre mannigfaltigen Gestaltungs- (z.B. Funktio­nali­sie­ rung durch einen nachgeschalteten Spritz­­­­­gussprozess) und Kom­­binations­ möglichkeiten (z.B. hybrider Aufbau) – immer mehr an Be­deu­tung im Bereich des modernen Leicht­­baus und sind daher im Fokus der Dresdener Forscher.

Neben den reinen technischen Aspekten ist auch die wirtschaftliche und ressourcen­ schonende Verarbeitung des Rohstoffs „Car­­­bon“ von größter Wichtigkeit. Nur in­ dustriell einsetzbare, kostengünstige Lö­sun­ ­gen ermöglichen den großflächigen Ein­­­satz des Faserverbundwerkstoffs zur Sicherung unserer zukünftigen Mobilität. Ein weiterer wichtiger Faktor für den Erfolg von Faser­ verbundstrukturen ist die virtuelle (digitale) Verknüpfung über die gesamte Prozesskette hinweg. CAD – Bauteilkon­ struktion und -auslegung inkl. Simulation müssen mit der automatischen Tape-Ablage „Hand in Hand“ arbeiten können. Dies wird durch unsere Software „LayupPlanner“ als Bindeglied zwischen Konstruktion und Pro­duktion ge­ währleistet.

compositence

Die parallel mit der Lieferung der Robo­ MAG-T Anlage etablierte Kooperation mit dem ILK hat zum Ziel, die Ressourcen und Erfahrungen auf beiden Seiten zu bündeln.

Gemeinsame Forschungsprojekte dienen der Weiterentwicklung der Anlagentechnik und der sich hieraus ergebenden Anwen­ dungen – mit dem Ziel, den Großindustriel­ len Einsatz des Werkstoffs „Carbon“ in zeit­­­­­­­­naher Zukunft möglich zu machen. „Kos­ tengünstige Preforms sind der Schlüs­sel zur Anwendung von Faserverbund­bau­teilen in der Großserie. Das ist nur möglich durch die effektive Nutzung von so wenigen Fasern wie möglich ohne jedweden Abfall. Die Erreichung dieses Ziels motiviert uns jeden Tag aufs Neue.“ betont Gregor We­ber, CEO von Compositence.

„We think composite“ Compositence ist Ihr zentraler Ansprechpartner für alle Themen rund um die Composite und der generativen Preform-Fertigung.

Profitieren Sie von unseren langjährigen Faserverbund-Erfahrungen. Wir helfen Ihnen gerne in allen Themenbereichen weiter!

www.compositence.com

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Technische Universität Dresden

29

Institute of Lightweight Engineering and Polymer Technology

�� THERMOPLASTIC COMPOSITES FOR

LARGE-SCALE SERIAL PRODUCTION �� Niels Modler, Werner Hufenbach

Lightweight engineering is one of the keys to the development of modern high-tech products offering a high degree of sustainability and value crea­ tion. Function-integrative lightweight engineering based on textile-reinforced composites has a particularly important role to play in this area. The DFG-funded special research project SFB 639 saw Dresden-based scientists investigate a relatively new group of materials in the form of hybrid yarn textile thermoplastics (HYTTs). The results of their research are presented in a technology de­­mon­­strator characterized by the novel use of textilereinforced thermo­plastics.

A holistic approach to efficient lightweight engineering Lightweight engineering enjoys more public interest than almost any other interdisciplinary field. In the case of modern automobile manufacturing in particular, many vehicle buyers now see low vehicle weight as a desirable characteristic – not least because of its significant impact on a vehicle’s range and drivability.

To give an example, 75 per cent of the driving resistance experienced by conventional vehicles is linked to their weight. Although it is realis­tic to expect improvements in the performance of mobile energy storage systems, the level of energy density they offer is set to remain relatively low when compared with that of oil-based fuels. This means that electric vehicles have to carry significantly more weight than conventional vehicles if they are to fulfil customer requirements in terms of range and speed. Reductions in vehicle weight neverthe­ less make it possible to lower the amount of energy input required and in turn downsize energy storage systems. As such, the goal is to reverse the spiral of costs and weight and use lightweight solutions to achieve the im­ provements required in terms of both profitability and ecological impact. Resource-efficient, affordable lightweight engineering has a crucial role to play in the establishment of sustainable value creation chains within Germany, espe-

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Technische Universität Dresden

cially where electric vehicles and the entirely new set of features and safety requirements that accompany them are concerned.

The Dresden Model of “function-integrative lightweight engineering in multi-material design” represents a promising solution to the aforementioned challenges. The application of the model nevertheless necessitates a switch from stand-alone material development to a systemic, interdisciplinary approach which sees the entire development and manufacturing chain for a generic demonstrator taken into account. The reason is that gaps in technology chains only become visible when materials, processes, simulation methods, components and assemblies are viewed not in isolation, but instead in terms of the impact they have on both each other and the overall system. Rea­ lized in Dresden, the DFG-funded special research project SFB 639 “Textile-reinforced Com­­posite Components for Function-integra­ ting Multi-material Design in Complex Light­ weight Applications” is an outstanding example of this type of integrated development process.

SFB 639: From filament to component Completed in 2015, special research project SFB 639 involved the cooperation of a total of 16 Dresden-based research institutes under the leadership of the Institute of Lightweight

Institute of Lightweight Engineering and Polymer Technology

Engineering and Polymer Technology (ILK).

Scientists from the Faculty of Mechanical Science and Engineering and the Faculty of Electrical and Computer Engineering (both part of TU Dresden) worked alongside researchers from the Fraunhofer Institute for Photonic Microsystems, the Fraunhofer Institute for Material and Beam Technology and the Leibniz Institute of Polymer Research. The German Research Foundation (DFG) provided SFB 639 with a total of around 33 million Euros in funding over twelve years (the maximum funding period). The aim of the project was to establish a set of scientific fundamentals and methods that facilitate the development and application of novel textile-reinforced composites suitable for innovative multi-material structures characterized by a high degree of function integration.

The research carried out as part of SFB 639 was characterized by an integrated approach which provided an ideal platform for the development of a continuous process chain (Figure 1). The spatial and temporal concen­tration of the project provided excellent oppor­tunities for interdisciplinary exchange, which in turn yielded process guidelines and design rules delivering cost savings, a substantial in­crease in performance and shorter development cycles for textile-reinforced components. Parti­cipating scientists studied the entire development and manufacturing process – from individual filaments right through to sophisticated lightweight components. This enabled them to identify and

Filaments

Hybr

id sp

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innin

Braid g

ing, k

nittin

g

close gaps in the technology chain, thus ensuring the continuity of the value creation chain.

SFB 639 saw scientists working in five areas of focus conduct research into novel textile-based composites with thermoplastic matrix systems.

When compared with other textile-reinforced composites, hybrid yarn textile thermoplastics (HYTTs) are a relatively new group of materials that offer numerous advantages over conven­ tional materials. Among other properties, HYTT composites are characterized by a high degree of stiffness and strength, low weight, adjust­ able damping and crash behaviour, suitability for use in combination with a huge variety of textile processes and struc­tures, numerous opportunities for function integration, compatibility with cost-effective, large-volume, highly reproducible serial pro­duction processes and recyclability. The as-yet unexploited potential offered by HYTT composites is therefore a highly interesting prospect within the context of future-oriented lightweight engineering applications in a variety of sectors. To give an exam­ple, HYTT composites are able to play a significant role in reducing the weight of modern auto­­­­­mo­­ tive components and systems, thus making them ideal for the e-mobility sector.

From fundamental research to practical applications The various demonstrators developed as part of SFB 639 demonstrate that fundamental

Preform

Prep a stitch ration, ing, e tc.

Composite

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epar etc. ation,

ng

Figure 1: From filament to component: The continuous process chain developed and applied as part of SFB 639.

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Figure 2: Known as the “FiF”, this functionintegrative vehicle system demonstrator combines all the scientific findings yielded by SFB 639.

Figure 3: An adaptive leaf spring characterized by active, adaptive spring behaviour.

research can also yield tangible results. One example is the FiF, a generic, function-integra­ tive vehicle system demonstrator. In addition to paving the way for the transfer of research findings to the mobility sector, the FiF and associated technologies are highly versatile and perform a pilot role for high-tech mechanical engineering applications in areas such as re­ newable energies.

The FiF consists of novel textile-thermoplastic materials and is designed for use within the context of urban, municipal or on-site transportation (Figure 2). Its low weight and high degree of function integration are the result of the use of textile-thermoplastic technologies developed as part of SFB 639. The vehicle’s highly integrative structure consists of just two loadbearing systems – the cabin and the support structure for the chassis and drive train – and

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Technische Universität Dresden

delivers substantial weight reductions at a minimum of manufacturing effort. The number of parts comprised by the entire load-bearing structure of the vehicle was reduced to just six highly integrated components. The FiF also demonstrates the integration of a range of structural, electric and adaptive functions. A network of sensors embedded into structural components extends throughout the entire vehicle, and not only facilitates data communication within the demonstrator itself, but also receives and processes information – for example on localized material damage – before making it available through operator interfaces.

An adaptive leaf spring developed during SFB 639 and used in the FiF for the first time is an example of an active, self-monitoring, self-managing function (Figure 3). The integration of a sensor network with embedded strain gauges into the leaf spring facilitates both online structural health monitoring and the control of actuators used to adjust spring stiffness. The novel hybrid structure consists of HYTT covers and an aluminium frame, and enables the modification of the component’s cross-section further to the application of pressure, thus ensuring the adaptation of

Institute of Lightweight Engineering and Polymer Technology

Figure 4: Prof. Dr.-Ing. habil. Prof. E.h. Dr. h.c.

Werner Hufenbach (2nd from left, Spokesperson for SFB 639), Prof. Dr.Ing. Niels Modler (centre, Managing Director of SFB 639), Dr.-Ing. Daniel Weck (2nd from right), Dipl.-Ing. Bernhard Maron (right, both researchers at the ILK) and Nils Poschwatta (left, designer) present the FiF tech­ nology demonstrator vehicle to the public for the first time at the Final Specialist Colloquium on SFB 639 in December 2015.

spring stiffness to the loads currently being applied to the vehicle.

The integral sensor networks developed as part of SFB 639 can be used to determine current operational status, document load spectra and overloading events and ensure the early detection of changes in the composite structure which are not visible from the outside.

Final Specialist Colloquium raises curtain on next phase Held in Dresden in December 2015, the Final Specialist Colloquium saw participating scientists present the results of research carried out within the framework of SFB 639 (Figure 4). Project spokesperson Prof. Dr.-Ing. habil.

Werner Hufenbach underlined the historic importance of the project: “Back in 1998, even the experts viewed us with a sceptical eye as we began turning our initial ideas into what eventually became SFB 639. No-one could even imagine that a motor vehicle might one day be made of textiles. The FiF – our function-integrative vehicle system demonstrator – shows just how important it is to keep your visions facing forwards. The fundamental

technologies we developed during SFB 639 are now ready to be transferred to the industrial applications of the future.”

The Rector of TU Dresden, Prof. Dr.-Ing. habil.

Hans Müller-Steinhagen, was also keen to stress the project’s significance: “SFB 639 has made an exceptional contribution in terms of both strengthening and increasing the visibility of Dresden as a centre for science. The Final Specialist Colloquium is therefore not the finish line – it is the starting block for new, innovative research projects which build on the results achieved by SFB 639.”

Contact

Acknowledgments: The German Research Foundation (DFG) provided SFB 639 with a total of around 33 million Euros in funding over a twelve-year period. Further information on SFB 639 is available here: www.tu-dresden.de/mw/ilk/ sfb639

Prof. Dr.-Ing. Niels Modler Managing Director of SFB 639, head of the Chair of Function-integrative Lightweight Engineering Phone: +49 (0)351 463 38156 niels.modler@tu-dresden.de

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

�� Piezoceramics in fibre-

reinforced composites – Manufacturing Technologies suitable for series production�� Niels Modler, Maik Gude, Anja Winkler, Tony Weber, Sirko Geller, Martin Dannemann, Klaudiusz Holeczek

The DFG-Collaborative Research Centre/Transregio 39 deals with the development of novel manufacturing technologies suitable for the series production of function-integrating lightweight structures with embedded piezoceramic elements. The main focus is placed on lightweight applications based on alu­ minium, and fibre-reinforced composites, which are investigated at three loca­ tions – Chemnitz, Dresden and Erlangen. Originating from the manufacturing of suitable piezoceramic semi-finished products, the development of adapted piezoceramic modules as well as of the respective serial production processes for function-integrating lightweight structures is focussed.

1. Lightweight design through function integration Function integration offers a high po­tential for the realisation of lightweight, smart structures for sustainable mobility and competitive energy supply applications. High-volume applications of such structures especially re­quire energy and resource efficient production processes, which are be­coming increasingly relevant in the production-oriented research. Particularly, active structures functionalised by means of embedded piezo­ceramic actuators and sensors that enable e.g. a structure-integrated condition monitoring or the realisation of measurement tasks, offer high lightweight potential.

The DFG-Colla­bo­­­­r ative Research Centre/ Trans­regio 39 (CRC/TR39) is dedicated to the development of adapted high-volume production processes for function-integrating lightweight structures with embedded piezoceramic elements. Originating from the production of customized piezoceramic modules at the Institute of Lightweight Engineering and Poly­­ mer Tech­nology (ILK) of the Technische Uni­

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Technische Universität Dresden

versität Dresden, their integration into massseries-relevant fibre-reinforced thermoplastic composites and cellular glass-fibre-reinforced poly­urethane composites (GF-PUR) is aimed.

The goal of the research work is to transfer the highly innovative function-integrating design methods and manufacturing technologies to high-volume applications.

2. Embeddable piezoceramic modules Currently, piezoceramic modules (actuators, sensors) are bonded to the manufactured component’s surface in an additional assembly step during the production of adaptive light­­weight structures made of fibre-reinforced composite materials. Additionally, the commercially available function modules, such as Macro Fiber Composites (MFC), include thermosetting carrier films which are characterised by very limited material compatibility to the matrix ma­terial (PA, PES, PPS, PEEK) of fibre-reinforced thermoplastic composite structures and thus a proper integration is not possible.

InStItUtE oF LIGHtWEIGHt EnGInEERInG anD PoLYMER tECHnoLoGY

a

b

Thermoplastic carrier film

Electrical contracts

Piezoceramic functional layer (Piezoceramic wafer or fibre composites) Electrodes

For the transition from an assembly-oriented to an “one-shot”-integration, new holistic approaches are necessary, which take into account equally the production restrictions of the structure as well as the bonding or integration challenges connected with the piezoceramic function modules. In this context, the solution approach of a matrix-homogeneous integration is pursued within the framework of the CRC/TR39. To achieve this goal a systematic development of novel thermoplasticcompatible piezoceramic modules (TPm) is necessary. TPM are characterised by matching materials of the carrier film and the matrix material of the thermoplastic composite structure (Figure 1). Consequently, the production of active thermoplastic composite components is realised by a deliberate “melting” of the thermoplastic components of the TPM and the composite material, which enables a homogeneous bonding of the functional module to the composite structure – without application of additional adhesives [1].

TPM consist of a piezoceramic func tional layer, which can be either realised as a piezoceramic wafer or piezoceramic fibres em-

a

bedded in a thermoplastic matrix (piezoceramic fibre composite). Such layer is surrounded on both sides by finger-like so-called inter-digitated-electrode (IDE) structures (d33 function principle) or by flat electrodes (d31 function principle) used for the application of electric field to the functional layer. This composition is enclosed between the thermoplastic carrier films, which are made of identical material as the matrix of the fibrereinforced composite component. The connection of the thermoplastic and ceramic components is ensured by utilizing a materialadapted hot pressing process with a defined process window (temperature, pressure).

For the high-volume production of TPM a rollto-roll process was developed at the ILK and realised on customised production facilities.

The necessary electrode structures are applied to the thermoplastic carrier films by means of an automated screen printing system (Figure 2a), and subsequently the TPM itself is assembled from the carrier films and the piezoceramic functional layers using the so-called “TPM assembly and packaging unit” (Figure 2b). Subsequently, this assembly is consolidated into a functional module utilizing an adapted hot pressing process.

Figure 1: Schematic structure of a TPM and an actual TPM (d31-TPM).

Figure 2: Production lines capable for high-volume production of TPM: a) Screen printing system, b) TPM assembly and packaging unit.

b

Technische Universität Dresden

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Functional layer

InStItUtE oF LIGHtWEIGHt EnGInEERInG anD PoLYMER tECHnoLoGY

ePreform-Transfer

ePreforming Thermoplastic foil

Conductors

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TPM

ePreform stentering frame

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Composite lay-up

Figure 3: Schematic drawing of a process chain for the manufacturing of fibre-reinforced thermoplastic composites with integrated piezoceramic modules.

Organic Organic sheet sheet stentering frame (OSF)

OSFtransfer

Handling

Preheating

Preheating station

3. integration technologies capable for high-volume production 3.1 Manufacturing of active thermoplastic composites In regard to production processes capable for a high-volume integration of the TPM into fibre-reinforced thermoplastic composites, appropriate manufacturing technologies are necessary. The process chain developed at the ILK within the CRC/TR39 is divided into three subprocesses: ePreforming, composite assembly, and hot pressing with online polarisation (Figure 3). In the so-called ePreforming, a thermoplastic film with piezoceramic modules and the necessary electrical contacts are automatized assembled to an ePreform [2]. Simultaneously, the fibre-reinforced

Figure 4: Manufacturing of an active fibre-reinforced composite structure for ultrasonic measurement applications: a) ePreform, b) section of the manufacturing complex showing the mould and infrared radiation field, c) active component with integrated TPM array.

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Technische Universität Dresden

a

Press process with online polarisation

b

- OPU +

Active component

Online polarisation unit (OPU)

composite structure made of organic sheets is stacked in a specially designed organic sheet stentering frame (OSF) and preheated using an infrared radiation field so that the thermoplastic matrix starts to melt. In the third subprocess – the hot pressing with online polarisation – the pre-melted organic sheets melt with the ePreform within the press. Provided that identical thermoplastic materials for the TPM carrier films, the ePreform and the matrix of the organic sheets are used, a matrix-homogeneous integration of the piezoceramic modules is achieved [3].

In the case of a Polyamide 6 matrix, the thermoplastic semi-finished products can be pressed to a homogeneous component with low pressures of up to 0.5 MPa and mould temperatures of 100°C. During the hot pressing process, the TPM is simultaneously

c

Institute of Lightweight Engineering and Polymer Technology

functionalised by a process-integrated polarisation step, the so-called online polarisation.

For this purpose, a contacting unit is used to connect the conducting paths of the ePreform. A high voltage resulting in an electric field is applied to the piezoceramic module using the online polarisation unit (OPU). For safety reasons, the generation of the electric field is achieved by the discharge of a capacitor. The measurement of the voltage drop on the capacitor enables both: the documenta­ tion of the polarization process and a qualita­ tive assessment of the polarisation of the integrated TPM already during the pressing process [4].

Using the above-described process chain, both single TPM and arrays of TPM, e.g. necessary for ultrasonic measurement applications, can be integrated into fibre-reinforced thermoplastic composites. On example of a demonstrator structure (Figure 4c), the production of the respective ePreform with TPM array arrangement (Figure 4a) and its integration into the thermoplastic composite structure (Figure 4b) is presented.

3.2 Spraying process for active glass fibre-polyurethane composites For high-volume production of fibre-reinforced composite components with thermoset matrix systems, polyurethane spraying procedures such as the long-fibre injection process (LFI) are especially predestined due to the moderate loads caused by the production process itself.

In regard to the integration of piezo modules, these process characteristics connected with the discharge into an open mould offer exten­ sive possibilities. The piezo modules can be

either applied to the mould’s surface prior to the spraying process and subsequently back­ foamed or embedded between the sprayed layers. Due to the low pressure and the lower process temperatures compared to the pro­ cessing of thermoplastics an integration of electronic processing systems is also possible.

Within the subproject B06 of the CRC/TR39, a process for high-volume production of active glass-fibre-polyurethane composite structures with integrated piezoelectric sensor modules and electronic signal processing units (Figure 5) is developed on the basis of the LFI process. A new approach is used to combine the previously seperated processing steps – module production, component manufacturing and integration of the sensor elements – in a one-step process.

Piezoceramic semi-finished products as well as suitable electrode structures are locally integrated into the composite during the composite manufacturing. The sensor assembly consists of a lower electrode, the piezoceramic functional layer and an upper electrode. The input components for the piezoceramic functional layer are preferably low-cost semi-finished products, such as fibre fragments, which can be obtained from piezoceramic production residues. Due to the fact that the matrix material must penetrate the sensor’s structure in thickness direction in order to assure a proper material embedding, porous semi-finished products, such as metal wire mesh, are used as electrode structures. For the integration of the ceramic semi-finished products and the electrode structures, an evaluation unit was developed and adapted into the existing LFI mixing head (Figure 6).

Glass fibre-reinforced polyurethane Piezoceramic functional elements (fibre fragments) Electrode Evaluation unit with adapted electronic functional elements

Figure 5: Schematic drawing of an integrated sensor module with adapted evaluation electronics.

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

a

b

Feeding device for piezoceramic components LFI-mixing head

Mould

Figure 6: Spraying process for active glass fibre-reinforced polyurethane composites: a) production cell, b) LFI mixing head with process unit for the automated integration of piezoelectric sensor modules.

LFI mixing head

a)

The sensor forming represents an autonomous process step, which can be integrated into the overall process both during and after the spraying process [5].

Due to the above-mentioned advantages, the LFI spraying process is also predestined for the integration of TPM into GF-PUR compo­ sites. Preliminary investigations show that TPM with polyamide carrier film can be directly back­foamed in the LFI process and can thus be integrated into the composite structure [6].

Current research focuses on the realisation of a process-integrated contacting and polarisa­ tion of the integrated piezo modules as well as the development of structure-integrated evaluation elec­tronics. In addition to a thin-walled design of the evaluation electronics, the focus is placed on efficient power consumption and the resulting minimisation of heat development.

4. Application perspectives An exemplary application for the components functionalised within the CRC/TR39 is, in addition to structural health or load monitoring, the use of embedded piezoelectric trans-

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Technische Universität Dresden

Vacuum gripper for electrode structures

b)

ducer arrays for ultrasound measurement systems. For demonstration purposes, the integrated piezoelectric transducers were used to gene­rate mechanical waves propagating in the fibre-reinforced composite structure, which lead to sound radiation in the adjacent medium due to the acoustic-mechanical coupling. By means of this principle a material-integrated distance measurement system can be realised, since the sound waves reflected by an obstacle cause in turn mechanical waves in the com­ ponent, which can also be measured by embedded piezoceramics.

With regard to ultrasonic measurement applications, the measurement of the surface velocities using the laser scanning vibrometry as well as the determination of the sound pressure using a microphone is especially suitable for the evaluation of such function-integrative structures (Figure 7a). For this purpose, the material-integrated piezoceramic modules of the TPM array are excited with a Hannwindowed sinusoidal signal. The superposi­ tion of the generated mechanical plate waves with the determined sound pressure shown in Figure 7b illustrates an amplification of the

Institute of Lightweight Engineering and Polymer Technology

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amplitude as well as a directional propagation of the plate and sound waves caused by the successive driving of the piezoceramic modules.

In addition, the microphone measurement of the sound pressure provides a basic proof that the structures with integrated transducer arrays are suitable for the directional radiation of acous­ tic waves [7, 8].

Figure 7: Measurement of the out-of-plane velocities and the sound pressures above the fibre-reinforced thermoplastic composite structure: a) Schematic representation of the measuring planes; b) Results of the combined acoustical-mechanical measurement.

Acknowledgments The presented research work is supported by the German Research Foun­dation (DFG) within the framework of the DFGCollaborative Research Centre/Trans­ regio 39 PT-PIESA especially in the subprojects A05, B04, B06 and T03.

Literature [1] Hufenbach, W.; Gude, M.; Modler, N.; Heber, T.; Winkler, A.; Weber, T.: Process chain modelling and analysis for the high volume production of thermoplastic composites with embedded piezoceramic modules. Smart Materials Research (2013), article ID 201631, S. 1-13.

[2] Hufenbach, W.; Modler, N.; Winkler, A.: Sensitivity analysis for the manufacturing of thermoplastic e-preforms for active textile reinforced thermoplastic composites. Procedia Materials Science 2 (2013), S. 1-9.

[3] Hufenbach, W. A.; Modler, N.; Winkler, A.; Ilg, J.; Rupitsch, S. J.: Fibre-reinforced composite structures based on thermoplastic matrices with embedded piezoceramic modules. Smart Materials and Structures 23 (2014) 2, 025011.

[4] Winkler, A.; N. Modler: Online poling of thermoplastic-compatible piezoceramic modules during the manufacturing process of active fibre-reinforced composites. In proceedings of 20th symposium on composites (Vienna, 30. June-02. July 2015), S.787-794.

[5] Weder, A.; Geller, S.; Heinig, A.; Tyczynski, T.; Hufenbach, W.; Fischer, W.-J.: A novel technology for the highvolume production of intelligent composite structures with integrated piezoceramic sensors and electronic components. Sensors and Actuators A: Physical, DOI: 10.1016/j.sna.2013.01.050.

[6] Geller, S.; Winkler, A.; Gude, M.: Investigations on the structural integrity and functional capability of embedded piezoelectric modules. In: Emerging Technologies in Non-Destructive Testing VI, ISBN:978-1-138-02884-5, S.361-365.

[7] Starke, E.; Dannemann, M.; Winkler, A.; Modler, N.; Holeczek; K.: Herstellung und Charakterisierung von Faserverbundstrukturen mit integrierten piezoelektrischen Wandlerarrays für die gerichtete Abstrahlung von Ultraschall. DAGA 2015, Nürnberg, 16.-19. März 2015, S. 60-64.

[8] Holeczek, K.; Starke, E.; Winkler, A.; Dannemann, M.; Modler, N.: Numerical and experimental characterisation of fibre-reinforced thermoplastic composite structures with embedded piezoelectric sensor-actuator-arrays for ultrasonic applications. Appl. Sci. 2016, 6(3), 55; doi: 10.3390/app6030055.

Contact

Dr.-Ing. Anja Winkler Deputy Head of Function Integration Phone: +49 (0)351 463 42498 anja.winkler@tu-dresden.de

Technische Universität Dresden

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One-Stop Lightweight System Solutions Feasibility

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

Testing

Leichtbau-Zentrum Sachsen GmbH

Leichtbau-Zentrum Sachsen engineering your innovative edge

Marschnerstraße 39, 01307 Dresden  info@lzs-dd.de  www.lzs-dd.de  +49 351 463 39477

Adete – Advanced Engineering & Technologies GmbH

›› ADETE – der Pionier im kommerziellen Composites-Engineering ‹‹ Die ADETE – Advanced Engineering & Technologies GmbH mit Sitz in Kaisers­ lautern entstand vor gut siebzehn Jahren als Hoch­ schul-Spin-off der Institut für Verbundwerk­stoffe GmbH (IVW) an der TU Kaiserslautern. Seit 2015 gehört das Unter­ nehmen zur BPW-Gruppe, Wiehl, dem Mo­ bil­­itäts- und Systempartner der Transport­ industrie. Seit­dem forciert ADETE im Be­ sonderen Kunst­­stoff-Leichtbau-Lö­sun­gen für die Nutz­­fahrzeug-Branche und ersetzt mit maß­ geschneiderten Entwicklungen Me­­tall­werk­stoffe zugunsten leichterer und ra­­­tio­­neller zu fertigender Kunststoff-Bau­ wei­sen. Hier­bei steht die für die jeweilige An­ for­ derung am besten geeignete Bau­ weise im Vorder­grund. Eine Besonderheit in der Branche, denn die ADETE-Lösungen sind unabhängig von Werkstoffhersteller und Bau­­­­teil­­fertiger. Vorrang haben der best­ geeignete Werkstoff und das bestgeeigne­ te Ferti­gungs­­verfahren. Und der Erfolg gibt ADETE recht: zahlreiche Preise hat das Un­ter­­neh­men inzwischen für seine kunden­ spezifischen Kunststoff-Lösungen ergattert, zuletzt 2016 den Europäischen Transport­ preis für Nachhal­tigkeit sowie den be­­­­gehr­ ­­ten JEC-Award im Bereich „Me­di­zin­ technik“.

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Die Umsetzung der kundenspezifischen ADETE-Lösungen in Form von Prototypen­ fertigung, Zulassung und Zertifizierung er­ folgen mit erfahrenen fertigungsorientierten Partnern, weit überwiegend bis zum Serien­ start. Durch zahlreiche Kooperationen und auch das aktive Mitwirken in fachspezifi­ schen Kompetenz-Netzwerken, wie dem Carbon Composites e.V. (CCeV) und dem Commercial Vehicle Cluster (CVC) Südwest, gelingt dies besonders reibungslos und effiz­ient.

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01.03.17 13:54

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

�� LIGHTWEIGHT ENGINEERING

METHODS FOR MEDICAL APPLICATIONS ��

Angelos Filippatos, Robert Gottwald, Martin Dannemann, Michael Kucher

Scientists at the Institute of Lightweight Engineering and Polymer Techno­logy (ILK) at TU Dresden develop innovative solutions for medical technology applications. In many cases, they benefit from their lightweight engineering ex­perience gained in a number of other sectors. Working in interdisciplinary teams, they develop problem-specific solutions for a variety of applications ranging from novel implant components and dental instruments to enhanced wheelchair technology.

1. Lightweight solutions for medical technology applications Lightweight engineering is a subject of increasing focus in the field of medical technology, after traditionally been used in sectors such as mechanical engineering, automobile manufacturing and aeronautics. Ger­many is the world’s third-largest producer of medical equipment, and produces around a third of roughly 100 billion euros in medical equip­ment sold in Europe each year. Light­weight solutions play an important role in the safe­ guarding and strengthening of the mar­ket position [1].

Medical technology combines knowledge in the fields of technology and medicine. The combination of development methods from a range of engineering disciplines combined with specialist expertise provided by medical partners, set the requirements to facilitate the realization of novel medical products, which enhance patient lives. The combination of experience gained by doctors and care specialists in areas such as diagnos­tics, therapy and nursing is just as important to the development process as the engineering solution of the final product. In particular, the development of new composite materials and inte­ grated design concepts opens the door to a variety of new opportu­nities that conven­

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Technische Universität Dresden

tional materials are unable to offer. Working closely with medical research facilities and strong industrial partners, scientists from the ILK focus their research in this area on the de­velopment of novel, innovative solutions for medical technology applications [2].

Lightweight engineering involves often the substitution of conventional materials with lightweight alternatives. Due to their low den­sity and high material stiffness as well as strength, fibre-reinforced materials are pre­ destined for medical mobility applications [2].

The parallel integration of targeted functions delivers products that are not only lighter than conventional alternatives, but also ex­ploit beneficial properties exhibited by FRPs, for instance sterili­zability, biocompatibility and transparency. Furthermore, the designer has the ability to “tune” the material properties e.g. by adjusting the laminate lay-up.

Thus, plenty of options exist on the ma­terial level to develop novel medical techno­logy applications.

2. Examples of innovative application of lightweight solutions Research at the ILK focuses on osteosyn­ thetic implants, the expansion and enhancement of the functions fulfilled by medical products (e.g. wheelchairs), the develop­-

Institute of Lightweight Engineering and Polymer Technology

ment of new endodontic instrument tips and the use of orthotics and prosthetics to support and protect various parts of the human body. Particular emphasis is placed on the adap­tation of structural-mechanical properties to specific applications, and the development and realization of manufacturing processes up to and including the prototype phase.

2.1 Endodontic instrument tips made of GF/PEEK Endodontics targets the removal of bacterial infections of the root canal in order to pre­ serve the health of the tooth. Root canal treatment sees chemomechanical processes used to remove infected tissue, and requires the insertion of ultrasonic instrument tips with a diameter of less than a millimetre into the root canal. Working in cooperation with the Tooth Preservation Clinic and specialists in paediatric dentistry at TU Dresden, the ILK is

and dimensioning of the ultrasonic instrument tips. As a result of the pronounced curvature of the canal geometry, the tips must maintain a high degree of deformability throughout the cleaning process. The material used must also exhibit various beneficial structural-dy­ namic properties – for example low ma­terial damping and the maximum possible vibration amplitudes – if optimum cleaning perfomance is to be en­sured. A high level of cleaning per­ formance facilitates a significant reduction in the duration of root canal treatment, which in turn decreases the level of strain to which the patient is exposed. Instru­ment tips are currently made of nickel-tita­nium alloys.

These so-called “shape memory alloys” offer a high level of both deformability and cleaning performance. The disad­vantage of these materials is that they are charac­ terized by sudden, unforeseeable failure.

Although the use of instrument tips made of pure plastic significantly reduces the risk

Slenderness ratio Canal Taper Mean diameter canal lenght a

Kanal

Coefficient of determination

investigating the potential offered by novel FRP in­strument tips in this area, in order to pre­­­vent the well-known problems of using con­­ventional instrument tips in future treatments.

Therefore, x-rays determine the dimensions of the human root canal and the results pro­ vide a basis for the creation of suitable parametric models of the geometry of the root canal (see Figure 1). The scientific systematization and classi­fication of the results yields quanti­fiable decision making tools for dental specialists. A considerable number of require­ments need to be factored into the design

b

Figure 1: X-ray of a human tooth and a para­ metric model of the root canal created using image analysis (a); Sectional view of a human tooth with FRP instru­ment tip inserted in the root canal (b).

of this type of failure, through their high mate­rial damping and lower material stiff­­ness they achieve a much lower level of cleaning performance than conven­tional metal alloy tips.

2.2 Other examples of lightweight solutions for medical technology applications The reconstruction of bone material, for in­stance, to complex fractures or tumourrelated resections, represents a par­ticularly demanding challenge in the area of the mouth, jaw and face. The metal osteo­

Technische Universität Dresden

43

Institute of Lightweight Engineering and Polymer Technology

Figure 2: Tailored bandage consisting of carbon fibre-reinforced polyether ether ketone.

synthetic plates generally used up to now, struggle to offer the required level of indivi­ dualization in terms of geometry and rigidity.

A novel implant that facilitates the patientspecific bridging of mandible defects is one of the solutions yielded by ex­tensive research carried out in cooperation with TU Dresden’s Centre for Mouth, Jaw and Facial Surgery.

The implant takes the form of an innovative bandage consisting of carbon fibre-reinforced polyether ether ketone (CF/PEEK) [4, 5], and can be adapted to the precise contours and loading involved in each individual case (see Figure 2).

Around 1.5 million people in Germany are dependent on permanent or occasional use of a wheelchair. In order to reach objects at a higher level, users need their wheelchairs to be able to raise them to the required height (see Figure 3). Scientists at the ILK are therefore developing a lifting mechanism

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Technische Universität Dresden

charac­terized by reductions in both weight and the number of parts required. Flexible FRP connecting members absorb any un­wanted forces induced when the lifting mechanism is activated. The new mechanism is also significantly lighter than the conven­ tional reference model. An efficient design strategy enables the rapid adaptation of the mechanism to a variety of wheelchairs and user weights.

Summary Many years of research experience in the interdisciplinary field of medical technology have shown that a close cooperation bet­­ween scientists from the fields of enginee­­ring, medicine and industry is essential for the necessary fundamental understanding of the problems and the development of novel innovative solutions. In addition, the synergetic use of the resultant pool of shared knowledge

Institute of Lightweight Engineering and Polymer Technology

Figure 3: Lightweight wheelchair lifting mechanism with a reduced number of parts [6]. Photo: © PRO ACTIV Reha-Technik GmbH

leads to substantial reductions in the length of the development process. By making its cutting-edge research findings available for transfer to industrial applications, the ILK contribu-

tes significantly to the strengthening of Germany as a centre for medical technology, as well as to the enhancement of patient well-being.

Contact

Literature [1] The European Medical Technology Industry in Figures. MedTech Europe, January 2014.

[2] Thema: Medizin und Technik | DresdnerTransferbrief 2.15, 22nd annual edition.

[3] Modler, N.; Hufenbach, W.; Gäbler, S.; Gottwald, R.; Schubert, F.; Dannemann, M.: Endodontic instruments made of fibre-reinforced polymer composites for root canal treatment – Preliminary investigations.

Composites Theory and Practice 2 (2015).

[4] Hufenbach, W.; Markwardt, J.; Modler, N.; Pfeifer, G.; Reitemeier, B.: Implantat zur individuellen Überbrückung von Kontinuitätsdefekten des Unterkiefers. DE 102005041412 B4.

[5] Hufenbach, W.; Gottwald, R.; Markwardt, J.; Eckelt, U.; Modler, N.; Reitemeier, B.: Berech­nung und experimentelle Prüfung einer Implan­tat­­­struktur in Faserverbundbauweise für die Überbrückung von Kontinuitätsdefekten des Unterkiefers. Biomedizinische Technik/Biomedi­cal Engineering. Volume 53, issue 6, p. 306–313, DOI: 10.1515/BMT.2008.048, November 2008.

[6] LIFT Manual Rollstuhl, PRO ACTIV Reha-Technik GmbH, http://www.proactiv-gmbh.de/.

Prof. Dr.-Ing. Niels Modler Board Member at the Insti­ tute of Lightweight Enginee­ ring and Polymer Technology, Chair of Function-Integrative Lightweight Engineering Phone: +49 (0)351 463 38156 niels.modler@tu-dresden.de

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

�� Material models for

textile-reinforced composites �� Robert Böhm, Ilja Koch, Mike Thieme, Gordon Just

Technical textiles made from natural or industrial filaments which are embedded in high-performance polymers form the novel material class tex­ tile-reinforced composites which show outstanding properties combined with a large variety. They offer a huge potential for lightweight applications in particular due to their high specific mechanical properties. Using phenomenologically motivated and physically based material models, the complex material behaviour of textile-reinforced composites is mathematically described at the ILK. The material modelling approach is based on the statistically distributed inhomogenouos textile structure in the elastic and plastic domain. Defects due to manufacturing and environmental influences like temperature and moisture are additionally considered.

Morphology and damage phenomenology of textile-reinforced composites The mechanical properties of textile-reinforced composites are particularly defined by the architecture, the arrangement and the material of the textile reinforcement. Compared

Figure 1: Micrograph, related geometry model and contour line diagram of the fibrematrix-distribution of textile-reinforced composites: glass fibre reinforced weft knitted polymer [1].

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Technische Universität Dresden

to conventional materials like metals or ceramics, these materials have larger inherent inhomogenities on different length scales due to manufacturing. In most cases this causes a scatter of the material properties. Figure 1 shows this problem using a hybrid yarn roving as an example.

Textile-reinforced composites show an anisotropic material behaviour which is particularly characterised by a non-linear stress-strainbehaviour. Those nonlinearities are caused by different damage phenomena of various length scales [2], cf. Figure 2. By analogy to the well known damage behaviour of unidirectional plies, the first damage occurs on the sub-microscale in the fibre-matrix-interface [3]. Those phenomena can be experimentally quantified using scanning electron microscopy and numerically modelled using representative vo­ lume elements. It can be shown that particular tensile stresses and shear stresses in the area of the filament surface cause crack ini­ tiation and subsequent crack growth. With increasing load, those interface cracks grow into matrix regions and form so-called interfibre-cracks. The form and the distribution of those cracks can be quantified in the material

Institute of Lightweight Engineering and Polymer Technology

volume at ILK using in situ computer tomography measurements [4]. Such inter-fibrecracks preferentially grow along the textile reinforcing filaments due to a relatively low critical energy release rate. In the case of 3D-reinforced composites this effect may cause undesirable interactions between load carrying primary and secondary layers [5-7].

As damage develops intra-textile delaminations and fibre breaks dominate the damage behaviour until final failure occurs.

Beside such diffuse (hard to quantify) and discrete (easy to quantify) damage pheno­ mena, plastic deformations are observed in particular in thermoplastic matrix systems or under increased temperatures. Additional inelastic deformations may also arise due to the growth of voids [8].

The described phenomena lead to a macroscopic stiffness degradation due to damage and to irreversible deformations due to matrix plasticity and void growth. To quantify those mechanical effects, specific experimental methods are developed and applied at ILK. By means of ultrasonic wave speed measurents in different directions, the elements of the stiffness tensor can be directly determined [2]. Additionally, loading-unloading experiments with relaxation and retardation stages enable a separated determination of inelastic and time-dependent strain components in order to deliver all necessary input parameters for a physically-based material modelling approach [9].

Modelling of damage and plasticity The complex damage behaviour of textile-reinforced composites requires a scale-bridging analysis of the damage phenomena. The observed non-linear property functions on the macro-scale (stiffness degradation, plastic deformations etc.) are a direct consequence of damage phenomena on the microscale and the mesoscale. With known material para­ meters, the modelling of such a damage behaviour can be conducted on different length scales. At the ILK, different numerical and analytical methods are used for that purpose.

The behaviour of undamaged composites on the microscale is modelled using micromechanical models with so-called representative volume elements (RVE). Such methods are very suitable to model the initiation of inter-

face cracks, the formation of microcracks, micro-plasticity and crack coalescence between interface cracks. The description of the homogenised material behaviour under the presence of microscopic damage requires the determination of material data for all consti­ tuents. Fibres, matrix and interface are modelled using RVE’s. It has to be considered that the scale of the model is sufficiently large in order to model all microscopic properties and to de­­­liver correct homogenization results. On the other hand, the model has to be small enough to represent the composite material on a larger scale. To ensure the vali­ dity of the approach the fibre directions and distributions as well as the fibre volume content should be determined and statistically secured with micrograph measurements [10,11].

Figure 2: Damage and plasticity causing inelastic deformations in textile-reinforced composites: glass fibre reinforced weft knitted polymer [6, 8].

In order that the RVE represents a “typical” section that can be identified at a random po­ sition in the material, several RVE’s which are stringed together must not have discontinui­­ties like gaps or overlaps between them. This can be ensured by a skillful choice of suitable boundary conditions. Contrary to homogenous displacement boundary conditions which lead to an upper estimation of the effective stiffnesses of a material (VOIGT-limit) and homogenous stress boundary conditions which de­ scribe a lower limit (REUSS-limit), periodic displacement boundary conditions lead to results which ensure the periodicity of stresses and displacements and simultaneously are between the VOIGT-REUSS-limits [12,13]. By

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

Figure 3: Multi-scale approach used at ILK to describe textile-reinforced composites.

averaging stresses and strains over the volume according to

homogenised material parameter functions are determined, e.g. for single rovings or ­unidirectional plies, cf. Figure 3. To fully describe the homogenised stiffness tensor, independent RVE-simulations have to be conducted for every possible load scenario. For that purpose, the RVE is loaded with one deformation component of the strain tensor while all other strain components are set to zero. A full column of the stiffness tensor results from each a test. Hence, assuming linear elasticity with

six different calculations are necessary to fully characterise the homogenised stiffness tensor.

Beyond that, a detailed investigation of cracking phenomena like crack initiation and growth as well as crack coalescence under arbitrary loading conditions is possible with such an approach. Here, especially the sub-

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Technische Universität Dresden

model-technique is used. The determined homogenised properties are then used as input parameters to describe textile unit cells with different degrees of complexity. Virtually arbitrary textile geometries can be modelled with that technique. As a result, continuum mechanics material models for textile layers are thereby provided. To apply such scalebridging modelling approaches for textile-re­­ inforced composites, a continuous chain of modelling tools and material knowledge is existing and ready to use at ILK. When a scale-bridging modelling approach is not suitable, simplified layer-based models can be used for an industrially-relevant simu­ lation of textile-reinforced composites. In this case, the textile composites are virtually separated into multi-layered composites with equivalent properties. This process defines socalled idealised basic layers. A distinction is made between idealised unidirectional layers (i-UD) with dominating discrete damage and bidirectional basic layers (BD) with dominating diffuse damage, cf. Figure 4. The basic layers have transversal-isotropic or rather orthotropic material behavior. During the damage process, all material symmetries remain unchanged.

The equivalent multi-layered composite then shows the same material behaviour like the real textile-reinforced composite and the

Institute of Lightweight Engineering and Polymer Technology

damage phenomenology

dominating discrete damage

dominating diffuse damage

idealised unidirectional basic layer

idealised bidirectional basic layer

geometry

modelled as

Figure 4: Virtual decomposition of textile-reinforced composites into basic textile layers depending on the observed damage phenomenology [2].

design process can be conducted using the Classical Laminate Theory (CLT).

For plane stress conditions, the damage-induced stiffness degradation is described using the damage tensor Dij

and fibre fai­lure. The impact of the described damage on the stiffness components with the indices (i=1,2,6) is consistently modelled by means of coupling vectors qi . In the case of increasing quasi-static or highly dynamic loading, this approach leads to the evolution law

In the case of cyclic loading, the damage evolution law is modified in a way that the damage increment per load cycle is calculated by

and Hooke's Law for the damaged idealised basic layer according to

with the compliance matrix of the undamaged layer Sij0 .

Damage initiation and total failure are modelled using physically based failure conditions. The Cuntze-criterion has proven to be suitable for many practical cases.

The damage growth is modelled with socalled damage evolution laws  j or every ­fracture mode. This leads to separated da­mage evo­lution laws for inter fibre failure

according to [2, 14].

To identify the necessary model parameters, direct experimental methods of damage iden­ tification are used beside the classical quasistatic, cyclic and highly dynamic tension/compression-shear-tests. The components of the compliance tensor of damaged textile composites can be directly measured using a ultra­ sonic measuring technique which has been developed at the ILK. A damaged spe­cimen is therefore transmitted with water-coupled ultrasonic waves in different directions. Afterwards, the ultrasonic duration is measured. By taking advantage of the proportionality of ultrasonic velocity and stiffness, the stiffness degrada­

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

550 H7 15

F(t)

10

15

F(t)

Fo = 40,5 kN, R = 0,1

Figure 5: Textile-reinforced tensile rod: numerical analysis of damage evolution under cycling loading conditions using the damage model ILK-Fatigue and comparison with experiments.

n tio

p Ex

t 5

n = 1,1·10 cycles

1,4·105 cycles

1,75·105 cycles

tion of the damaged composite can be determined in a non-linear optimisation procedure [15]. Beyond that, acoustic emission analysis in combination with video analysis and computer tomography (CT) are excellent experimental tools for the damage analysis of textile-reinforced composites. Especially the unique Insitu-CT test device developed at ILK enables a very accurate crack analysis because cracks are analysed in situ while a mechanical load is applied on the specimen. A very high reso­­ lution can be achieved with that device.

Selected applications

Contact

Dr.-Ing. habil. Robert Böhm Head of Material models Phone: +49 (0)351 463 38 080 robert.boehm1@tu-dresden.de

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Technische Universität Dresden

nt

me

eri

ula Sim

The practical benefit of the continuous simu­ lation method to model textile-reinforced composites under static, cyclic and dynamic loading conditions has been proven within the design process of several lightweight products.

One example for such an application of the damage model for cyclic loading (ILKFATIGUE) is the life cycle analysis of a generic carbon fibre reinforced tensile strut, see Figure 5. The tensile strut has been manu­ factured using resin transfer moulding (RTM) with a multi-piece textile preform made with the tailored fibre placement (TFP) technology.

Due to a very straight arrangement of the reinforcing fibres and a low content of polymeric stitching filaments, a decomposition into i-UD layers has been conducted. The parameter identification was performed using single level tests on stitched basic layers and lami­

N = 2,0·105 cycles

nates with a layup of [90/0] s and [+45/-45] s.

The parameters of the damage evolution law were determined with the measured stiffness distributions and Wöhler curves. Using an Abaqus subroutine, the tensile strut was numerically modelled with 31.204 volume elements. Figure 5 shows a comparison between the cycle-wise calculated damage states and the experimentally observed da­ mage phenomena. Both the location and the degree of damage are modelled very accurate by the new material model. By additionally applying a so-called cycle jump technology, only 12.500 calculation steps are necessary to numerically model 200.000 load cycles.

The excellent application maturity can also be demonstrated using lightweight structures which are quasi-statically loaded. Figure 6 shows a hybrid textile-reinforced strut-wheel carrier structure as a reference component for automotive structures loaded in bending.

Here, a geometrically complex glass fibre reinforced polyamide structure with a textile-reinforced organic sheet and long fibre reinforced ribs to increase the structural stiffness has been manufactured.

The non-linear damage and failure behaviour of the wheel carrier structure has been analysed using 3-point bending experiments. Figure 6 shows the high modelling quality of the ma­ terial model ILK-DAMAGE by comparing the results of the modelled damaged zones with the experimentally observed damage.

Institute of Lightweight Engineering and Polymer Technology

injection moulded structure GFRP-sheet

support 2

support 1 detailed photographs after test

simulation results Damage

intact/ damaged deleted/ failed

Figure 6: Damage simulation of a hybrid textile-reinforced strut-wheel carrier structure with the fracture mode related damage model ILK-DAMAGE.

Literature [1] Thieme, M.: Beitrag zur Beschreibung des probabilistischen Versagens­ verhaltens textilverstärkter Verbundwerkstoffe, PhD Thesis, TU Dresden, 2015.

[2] Böhm, R.: Bruchmodebezogene Beschreibung des Degradationsverhaltens textilverstärkter Verbundwerkstoffe. PhD Thesis; TU Dresden. 2008.

[3] Quaresimin, M.; Talreja, R.: Fatigue of fiber reinforced composites under multiaxial loading. In: Polymer Composites in the Aerospace Industry, S.155-190, DOI: 10.1016/B978-0-85709-523-7.00007-4.

[4] Böhm, R.; Stiller, J.; Behnisch, T.; Zscheyge, M.; Protz, R.; Radloff, S.; Gude, M.; Hufenbach, W.: A quantitative comparison of the capabilities of in situ computed tomography and conventional computed tomography for damage analysis of composites. Composites Science and Technology 110 (2015) S. 62–68.

[5] Zangenberg J.: The effects of fibre architecture on fatigue life-time of composite materials. PhD Thesis, Technische Universität Dänemark, 2013.

[6] Koch, I.: Modellierung des Ermüdungsverhaltens textilverstärkter Kunststoffe, PhD Thesis, TU Dresden, 2010.

[7] Gude, M.; Hufenbach, W.; Koch, I.: Damage evolution of novel 3D textile reinforced composites under fatigue loading conditions. In: Composites Science and Technology 70 (2010), Nr. 1, S. 186-192.

[8] Zscheyge, M.: Zum temperatur- und dehnratenabhängigen Deformations- und Schädigungsverhalten von Textil-Thermoplast-Verbunden. PhD Thesis, TU Dresden, 2014.

[9] Koch, I.; Zscheyge, M.; Gottwald, R.; Lange, M.; Zichner, M.; Böhm, R.; Grüber, B.; Lepper, M.; Modler, N.; Gude, M.: Textile-Reinforced Thermo­ plastics for Com­­pliant Mechanisms – Application and Material Phenomena, Advanced Engineering Materials, online erschienen Nov. 2015, DOI: 10.1002/ adem.201500448.

[10] Gitman, I.M.; Askes, H.; Sluys, L.J.: Representative volume: Existance and size determination. Engineering Fracture Mechanics 74 (2007) S. 2518-2534.

[11] Vaughan, T.J.; McCarthy, C.T.: A combined experimental-numerical approach for generating statistically equivalent fibre distributions for high strength laminated composite materials. Composites Science and Technology 70 (2010) S. 291-297.

[12] Huet, C. : Application of Variational Concepts to Size Effects in Elastic Heterogeneous Bodies. Journal of the Mechanics and Physics of Solids 38 (1990), S. 813–841.

[13] Kästner, M. : Skalenübergreifende Modellierung und Simulation des mechanischen Verhaltens von textilverstärktem Polypropylen unter Nutzung der XFEM. PhD Thesis, TU Dresden, 2009.

[14] Koch, I.; Gude, M.: Multiaxial fatigue of a unidirectional ply: An experimental top-down approach, in Carvelli, V.; Lomov, S. (Ed.) Fatigue of Textile Composites, Woodhead Publishers, 2015.

[15] Böhm, R.; Hufenbach, W.: Experimentally based strategy for damage analysis of textile-reinforced composites under static loading. Composites Science and Technology 70 (2010) S. 1330–1337.

Technische Universität Dresden

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Herbert Hänchen GmbH & Co. KG

››Revolution in der Werkstofftechnik: H-CFK statt Stahl‹‹

Im Maschinenbau kommt dieses Ver­ bundmaterial erst langsam an – trotz der enormen Vorteile des Werkstoffs wie etwa geringem Gewicht sowie hoher Be­last­ barkeit und Beständigkeit gegen ver­­schie­

be­­deutet, dass je nach gewünschter Bau­ teilfestigkeit und Biegesteifigkeit die Lage, Anzahl und Art der Carbonfasern zu defi­ nieren ist. Hänchen arbeitet dabei mit einer eigens entwickelt und gebauten 7-AchsWickelmaschine.

denste Medien oder die Korro­sions­­­freiheit.

Der Werkstoff dehnt sich bei Er­wärmung nicht aus und bietet eine äußerste harte, dichte und verschleißfeste Oberfläche, die während der Produktion in das H-CFK Bau­­teil eingebracht wird und den CarbonGrundkörper versiegelt. Damit ist eine Fein­­­bearbeitung von Rz 1 möglich.

Bezüglich der Belastung ist der Werkstoff in drei Dimensionen konfigurierbar. Das

Der Fertigungsprozess erlaubt zudem eine hochfeste Verbindung zu anderen Kompo­ nenten, die wegen ihrer Form oder be­ stimmter Bearbeitungsprozesse aus Metall bestehen. Um sehr hohe Belastungen zu gewährleisten, werden die Verbindungs­ elemente in das Carbon-Bauteil eingebun­ den statt geklebt.

Auf der Hannover Messe 2017 stellt Hänchen den Werkstoff vor. In Halle 23, Stand C03, werden einige Vorteile von H-CFK zum Anfassen und Ausprobieren dargestellt.

Public Relations

Die meisten Bauteile im Maschinenbau sind ganz klassisch aus Stahl gefertigt.

Er gibt ein Gefühl von Sicherheit, ist vertraut. Dabei können Verbünde aus H-CFK bei deutlich geringerem Gewicht eine bessere Performance zeigen und damit neue Konstruktionen ermöglichen. H-CFK ist ein von Hänchen entwickelter, hoch belastbarer Werkstoff, aus carbonfaserverstärktem Kunststoff (CFK) kombiniert mit anderen Kompo­ nenten. Ursprünglich für den Einsatz in Hydraulikzylindern konzipiert, bietet das Unternehmen auch Stangen und Rohre aus H-CFK an.

H-CFK Bauteile Leicht, belastbar, rostfrei •

• •

Carbon-Zylinder aus H-CFK, bis zu 70 % leichter und 50 % energieeffizienter als Stahl-Zylinder Runde Bauteile mit hochbelastbarerm Carbon-Metall-Verbund Druckdichte Rohre und Stangen aus H-CFK

www.haenchen.de

096-497-019_cs5.indd 1

28.02.17 11:29

Institute of Lightweight Engineering and Polymer Technology

�� LIGHTWEIGHT DESIGN –

THE SYSTEMS OF THE FUTURE �� Stefan Kipfelsberger, Jörn Kiele

The term “lightweight design” describes the holistic, material-oriented development of innovative lightweight structures. This is the fundamental approach adopted by the Expert Group on Lightweight Design as they investigate innovative, material-based design concepts and use methodical analysis to develop integrated lightweight components and systems for applications in a variety of sectors.

Figure 1: The Expert Group on Lightweight Design at the InEco generic demonstrator.

A methodical design process for lightweight structures The definition of specific design principles for lightweight structures and the adoption thereof into design catalogues, guidelines and standards is a prerequisite for the widespread transfer of lab-developed lightweight struc­ tures to practical applications in a variety of industries. It is therefore at the heart of the research carried out by the Expert Group on Lightweight Design (see Figure 1).

The group aims to develop and establish a methodical design process which draws on

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fundamental research into material mechanics conducted at the Institute of Lightweight Engi­ neering and Polymer Technology (ILK). The process begins with detailed analysis of the design brief, with particular emphasis placed on the function-oriented, holistic examination of systems and subsystems. This is vital if the subsequent crea­tive design phase is to yield innovative light­­­weight solutions that go far beyond conventional solutions and exploit more than the sum of the potential offered by individual components. The analy­tical phase there­ fore involves not only critical scrutiny of the functions performed by individual components and systems, but also the definition of those functions as general points of force application and transmission within the functional system.

This includes the vector-based identification of inevitable function-related dependencies ex­ hibited by moving components, for example directions of movement. The resultant analytical findings combine with pre-de­fined constraints – for exam­ple adjacent components or other restrictions on installation space – to facilitate the precise definition of the space within which the lightweight system functions.

The next step in the methodical design process is the conceptualization phase, and more specifically the development of solutions for functions and subfunctions housed within the aforementioned functional space. This is the main focus of research into the methodical design process. As a result of the specific properties of modern lightweight materials, and in

InstItute of LIghtweIght engIneerIng and PoLymer technoLogy

particular composites, the universal design concepts proposed in this area to date have all been flawed. It is instead an interactive design process such as the one presented in Figure 2 that is required. In view of the close relationship between manufacturing technologies and mechanical material properties, the precise analysis and definition of the manufacturing process at an early stage in the development process is indispensable to the design of lightweight structures tailored to both mechanical material parameters and available installation space. The reason for this is that the manufacturing process has a direct influence on component design in two ways. On the one hand the component needs to be compatible with the manufacturing process, while on the other hand the manufacturing process may have an impact on material properties. In recent years, the ILK has conducted research into a variety of design methods for drivetrain components featuring continuous fibre reinforcement, with particular focus placed on connections between shafts and hubs. The institute’s findings have been implemented within the framework of industrial projects. Taking the analysis of specific criteria – for example the torque or bending moment to be transmitted – and dynamic operational behaviour as their basis, participating researchers have analyzed and categorized a wide range of connection types before presenting them in the form of design catalogues suitable for day-to-day design work (see Figure 3). This is an excellent example of the transfer of fundamental research into methodical lightweight design processes to industrial applications.

system demonstrators. The core objectives are always to develop solutions to lightweight engineering challenges and identify new areas of application.

Lighter wheels, longer range: a hybrid bus for route 64 Scientists at the ILK examined the wheels of the hybrid bus in order to identify weight reduction opportunities and in turn increase the vehicle’s electric range. The resultant weight reduction concept is based on a highly efficient hybrid, multi-material solution consisting of a Carbon-Fibre Reinforced Plastic (CFRP) wheel rim and an aluminium wheel centre. Working together with a Saxon manufacturing partner, participating researchers produced all the parts required for the innovative rim within the Free State of Saxony before assembling them to

To apply and deepen the aforementioned insights into the design process the expert 02.11.2015 Group on Lightweight Design plans and uses current and future projects. This is set to include research into modular systems for fibrereinforced lightweight structures as well as joining technologies for applications in a variety of sectors. Findings will feed into design tools for day-to-day development tasks.

Figure 2: Development triangle for the methodical design process.

Figure 3: Design catalogue for shaft-hub connections.

Design

Material

Structural Assessment

Interaction of material properties and manufacturing

Manufacturing

Vorstellung der Fachgruppe Leichtbauweisen

1

Examples of applications in the automotive sector The Expert Group on Lightweight Design has activities in the automotive sector cover all relevant scales. Research and development projects range from individual components and complex assemblies to roadworthy

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Si m

on ati ul

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Design

Figure 4: Holistic development process for lightweight structures.

Zentrum Sachsen GmbH (LZS), engineers from ThyssenKrupp Steel Europe AG and a range of other project partners. The aim of the project was to share insights, promote lightweight engineering and develop a new, holistic, forward-looking, sustainable vehicle concept for the e-mobility sector. Findings were incorporated into the InEco, a generic demon­strator vehicle presented to the world for the first time at the International Motor Show in Frankfurt am Main in September 2013. The vehicle’s chassis consists of a combination of CFRP and steel, thus keeping the overall mass of the ultra-lightweight vehicle below 900 kg.

Hybrid technologies for the aviation sector create a lightweight wheel (see Figure 4). About half of the hybrid rim consists of CFRP, the other half of aluminium. With a weight less than 20 kilograms, the rim is over 50 per cent lighter thana conventional steel rim and reduces the total weight of the bus by around 250 kilograms.

Since 2004, scientists at the ILK have already been conducting intensive research in this

In addition to applied research into fibrereinforced composites, the Expert Group on Lightweight Design also addresses issues in the field of hybrid material systems, with projects already resulting in numerous demon­ strators. Another area of focus is advanced hybridization strategies, many of which have been developed as part of federal aeronautical research programmes set up by the Federal Ministry for Economic Affairs and Energy

field. Two prototypes presented at the 2009 International Motor Show in Frankfurt am Main and the eCarTec trade fair demonstrated the opportunities presented by lightweight engineering and potential design concepts for the e-mobility sector (see Figure 5). The institute was also a participant in the joint project ALIEN alongside specialists from Leichtbau-

(BMWi). The strategies are generally de­ signed at structural level in order to ensure that functional elements (e.g. actuators for aviation applications, see Figure 6) meet the relevant specifications. In particular, the new opportunities opened up by multi-material design make it possible to take into account changes in the properties of fibre-reinforced

Ultra-lightweight e-mobility: Joint project ALIEN

Figure 5: The InEco generic demonstrator.

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composites when exposed to heat and a variety of media. Hybrid design concepts pave the way for the use of FRP technologies in this area, with significant progress made in the field of lightweight hydraulic components.

To date, particular emphasis has been placed on fundamental issues involving chemical resistance and thermomechanical behaviour, not least because of the necessity of ensuring that materials are compatible with one another despite differences in their thermal expansion coefficients.

The current Federal Aeronautical Research Programme (LuFo) uses the example of next-generation aircraft undercarriages to investigate the potential offered by hybridiza­ tion. Parti­cipating researchers from the ILK are deve­loping a modular design process which makes it possible to factor in hybrid structural concepts at a very early phase in a project. The process draws on comprehensive material characterization and calculation models tai­lored to hybrid materials. It will provide the basis for a coordinated utilization strategy that enables the transfer of the principles and concepts developed to technolo­ gical applications. The primary area of focus

sectors, that could be a realistic long term target for hybrid technologies.

Lightweight designs for robust applications Research into lightweight structures for rail applications represents a special challenge.

To date, research and development projects in this field have been very cautious in their approach to lightweight solutions when com­ pared with other sectors. In addition to complex relationships between forwarders, carriers, carriage owners and manufacturers of loco­ motives and carriages, the primary reasons for this situation are the demanding specifications and licensing requirements placed on robust components and cost pressure in the transport sector as a whole. In view of the increasing volume of goods – and in particular piece goods – and traffic on the roads and rails, innovative lightweight concepts are required in the case of both heavy goods vehicles and rolling stock. Importantly, the use of lightweight solutions to reduce the tare weight of a vehicle can have a positive effect on its maximum loading capacity without increasing axle loads. Given the po­tential benefits, new material concepts and vehicle designs based on lightweight en­

Figure 6: The structure of a lightweight hydraulic actuator [1].

is undercarriage components that can be reduced in weight with the aid of hybrid solutions but are not compatible with mono­ lithic FRP due to the level of operational loading they are exposed to. Looking to the future, a huge variety of solutions featuring hybrid elements are conceivable, with wide­ spread market penetration across multiple

gineering are of huge economic importance to the transport sector. They can even cause fluctuations in the appeal of entire transport systems, which may in turn lead to a shift in volumes onto or off the rails.

The Expert Group on Lightweight Design has recognized the important part lightweight

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engineering has to play in this area, and works in close cooperation with other expert groups within the ILK, fellow institutes at TU Dresden, Leichtbau-Zentrum Sachsen GmbH and nume­ rous industrial partners on the development of targeted solutions. Although the requirements involved permit the use of fundamental automotive or aviation solutions as basic frameworks for the design of structural components and systems for rail applications, those solutions nevertheless need to be thoroughly revised and methodically adapted to the specific application. The greatest challenge in this regard is the cost pressure generated by the relative affordability of reference structures, the majority of which take the form of cast and welded metal structures. To give two examples, bogies for freight wagons sell for under 15,000 euros, an entire container car for under 70,000 euros. Numerous projects have therefore focused not only on the development of lightweight structures suitable for high levels of mechanical loading, but also the definition of manufacturing-oriented design rules which enable components to be manufactured in Germany. This is an excellent example of the use of innovation to put sustainable momentum behind industrial companies.

With previous research having concentrated on drivetrain components, suspension and damping features and large-scale claddings

Lightweight systems and tribology The exploitation of all the potential light­weight solutions have to offer is dependent on the methodical analysis of individual components as part of overall systems and functional spaces rather than in isolation. This neverthe­less requires comprehensive knowledge of component interactions. Those in­ teractions, and in particular those involving moving components, are the focus of tribo­ logical research carried out by the Expert Group on Light­weight Design. The ILK’s outstanding facilities (for example the Material Physics Laboratory), mastery of the fundamental properties of tribomechanically optimized polymer-based materials and adaptable equipment suitable for the tribological testing of materials and components enable the group’s researchers to tackle tribological challenges throughout the design process – all the way from material development to prototype testing.

Among other projects, this continuous, methodical approach has been applied to the development of a tribologically optimized gliding system for the Transrapid magnetic levitation train. Rather than running on conventional wheels and rails, the train is propelled by a non-contact, electromagnetic load-bearing, guidance and drive system.

Support skid housing

Figure 7: The positioning of support skids on the undercarriage of the Transrapid (left); photo of a support skid housing and gliding segment above the guideway (right).

Support skids

which also perform a structural role, the focus of future projects is set to shift to the point of connection with the load-bearing structure.

Particular emphasis will be placed on research into suitable manufacturing technologies for large structures (e.g. thick-walled load-bearing elements) and the development of corresponding connection systems.

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Guideway

Gliding segment

Levitation magnets positioned beneath the vehicle pull it down towards the guideway, with guidance magnets used to prevent undesirable lateral movement. The train is propelled by linear motors integrated into the guideway. During normal operation, a mag­ netic levitation train travels on a non-contact basis, thus avoiding kinetic friction.

Institute of Lightweight Engineering and Polymer Technology

In order to guarantee the safety of both passen­­­gers and the surrounding environment, the Transrapid must remain fully functional even in the event of multiple failure of electric assemblies at speeds of up to 500 km/h. The project brief was therefore to de­velop a gliding system consisting of support skids equipped with gliding segments and a gliding layer for the Transrapid guideway (see Figure 7).

In keeping with the methodical design process, the project began with extensive pre­liminary studies used to select suitable support skid materials and guideway coatings, which were then tribologically optimized with the aid of standardized tests. This provided a foundation for the manufacturing of functional elements and the design of a test setup which realistically simulated their future operational environment. Given the high relative speeds of up to 112 m/s reached within the system, a high-speed tribological test bench was set up at the ILK’s multi-station tribolo­gical test facility for the purpose of techno­logical vali­ dation.

Fundamental laboratory-scale findings provided a basis for the subsequent development and testing of prototypical gliding systems.

The guideway in Shanghai witnessed the world’s first commercial use of carbon fibrereinforced carbon (CFC) support skids in combination with a specially coated guideway.

The properties predicted by the preliminary qualification and validation process [2] were either fully confirmed or exceeded by the results of verification tests carried out in Shang­hai [3, 4].

A linear wear rate of wl/s = 4.75 µm/km was determined further to a test run during which the support skid remained in contact with the guideway over the entire distance.

This equates with almost no wear in the gliding coating and a safe gliding distance of up to 400 km. As such, participating researchers were able to complete successfully every development step from fundamental research into chemical and physical pheno­ mena right through to the implementation of a practical solution [5].

The project findings are now being used by both the expert group and the ILK for the development of other tribologically optimized lightweight systems. Work focuses

on drivetrain systems and associated com­­­­ponents (e.g. shafts, bearings and gear­­wheels), as well as housings and loadbea­­ring structures for applications in a range of sectors.

Contact

Conclusion The interdisciplinary research carried out by the Expert Group on Lightweight Design focuses on the material-oriented design of lightweight components and systems. The group’s core objective is to develop and es­ tablish a methodical design process for lightweight structures that is compatible with applications in a variety of sectors.

Taking the results of material analysis and insights into functional interactions within the planned system as their basis, researchers develop methodical solutions that can be applied to the material-oriented design of lightweight structures. The group’s exper­ tise is rounded off by tailored manufacturing concepts, tool development and the creation of suitable test facilities for system validation processes required as part of both funda­men­ tal tribological research and the testing of complex overall systems, thus enabling it to realize continuous, application-oriented design and development processes.

Dipl.-Ing. Stefan Kipfelsberger Head of Lightweight Design Phone: +49 (0)351 463 42386 stefan.kipfelsberger@ tu-dresden.de

Literature/Sources [1] Hufenbach, W.; Helms, O.; Ulbricht, A.; Garthaus, C.; Baumbach, V.: Lightweight hy­draulic pipes and actuators in innovative multi-material-design. Proceedings of the 4th International Conference on Recent Advances in Aerospace Actuation Systems and Components (R3ASC), p. 66-71, Toulouse, May 2010.

[2] Bauer, M.; Hufenbach, W.; Kunze, K.; Miller, L.; Zheng, Q.: Die Transrapid – Magnetschwebetechnik und tribologische Probleme – ein Widerspruch? GfT-Tribologie-Fachtagung “Reibung, Schmierung und Verschleiß”, Göttingen, 27.-29.09.2004.

[3] Löser, F.: Betriebserfahrungen beim Transrapid in Shanghai. Proceedings of the 4th Dresden Transrapid Conference, p. 101-113, 06.10.2004.

[4] Miller, L.: Entwicklungspotential des Transrapid für zukünftige Einsatzfelder. Proceedings of the 4th Dresden Transrapid Conference, p. 43-53, 06.10.2004.

[5] Zheng, Q.; Hufenbach, W.: Der Transrapid – Eine Zukunftstechnologie für effiziente Mobilität.

Proceedings of the 13th Dresden Lightweight Engineering Symposium, 18.-19.06.2009.

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D DR RE ES SD DE EN N Product Product Development Development Part Part Construction Construction FEM FEM Simulation Simulation Rheolog./Therm.

Rheolog./Therm. Simulation Simulation

Tool Tool Construction Construction Tool Tool Management Management Project Project Management Management Process Process Development Development

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Lätzsch GmbH Kunststoffverarbeitung

›› Ihr kompetenter Partner ‹‹ Das Unternehmen wurde 1954 als Hand­werksbetrieb mit Sitz in KohrenSahlis gegründet. Im Mai 1972 erfolgte die Verstaatlichung. Am 01.06.1990 wurde der Betrieb reprivatisiert und firmiert seit dem unter Lätzsch GmbH Kunststoffverarbeitung. Geschäfts­tä­ tig­keit ist die Herstellung technischer Produkte aus Thermo- und Duroplasten.

1991 erfolgte der Erwerb eines zweiten Betriebes in Streitwald bei Frohburg. An diesem Standort wurde mit der Fertigung von PUR-Integralhalbhartschaumteilen begonnen. Hier wurde auch der Service für Nutzfahrzeuge und Baumaschinen weitergeführt. Inzwischen ist die Werkstatt Servicepartner für Multicar, Mercedes Benz Nutzfahrzeuge, Unimog und IVECO. Ebenso wird der Service an Kommunal­ geräten und -maschinen angeboten. Zum Leis­tungs­angebot der Werkstatt gehört auch eine Metallverarbeitung, wo diverse Inserts für die Kunststoffproduktion in Eigenleistung hergestellt werden. 1996 wurde ein Be­trieb zur Herstellung faserverstärkter Kunststoffe in Neustadt/ Sachsen erworben. Seit 2006 wird das Produktions­pro­gramm am neugebauten Standort in Thierbach bei Kitzscher fort-

geführt und erweitert. Inzwischen ist das Unternehmen überregional tätig und verfügt über 125 Mitarbeiter.

Zum Leistungsangebot der Lätzsch GmbH gehören neben der Fertigung von Kom­ponenten sowie Komplettbaugruppen für den Nutzfahrzeug- und Maschinenbau, die Fertigung von Gehäuse- und Verklei­ dungs­teilen für die Medizintechnik, Appa­ rate- und Behälterbau auch die Fertigung von Schie­nenfahrzeugkompo­nenten. Die Herstellung der faserverstärkten Bau­grup­ pen erfolgt in unterschiedlichen Herstel­ lungstechno­logien.

Neben der Fertigung wird auch die Kon­ struktion faserverstärkter Kunststoff­teile im 3-D sowie eigener Modell- und For­ men­ bau angeboten. Die mechanische Be­­ arbeitung der Kunststoffteile erfolgt weitestgehend mit CNC gestützten Be­­ arbeitungsmaschinen.

Ansprechpartner: Hans-Joachim Lätzsch hjlaetzsch@laetzsch.de Leistungen: Herstellung faserverstärkter Bauteile für Interieur und Exterieur Mitarbeiter: 125 Jahresumsatz: 15 Mio. Euro Ausbildungsplätze: Verfahrensmechaniker Kunststoff- und Kautschuktechnik (2)

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Public Relations

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�� Simulation methods for

high performance structures�� Bernd Grüber, Andreas Hornig, Roman Koschichow

The development of modern lightweight structures and systems requires both a better exploitation of the material’s full potential and simultaneously an increased cost efficiency. Already today, computer-based design and calculation methods deliver a crucial contribution to reach this aim. In the future, they will even get stronger into the focus of the whole development process. Therefore, the synergetic combination of different simulation methods along the entire value added chain is a key to efficient lightweight structures.

Dimensioning of resource-efficient lightweight components in multi-material design The design process for lightweight components and systems in multi-material design differs fundamentally from the design process of structures made of conventional isotropic materials. In contrast to established approaches, designing with fibre-reinforced com­­­po­ sites is governed by a complex interaction between engineering, fabrication and verification. Currently, such a design process is still characterised by a trial-and-error approach.

Compared to classical materials, it becomes apparent that higher levels of detail need to be considered when dealing with composite materials.

Already the fibre-reinforced material itself exhibits a hierarchical structure. On the micro scale the material is characterized by the properties of the reinforcing filaments and of the matrix material. Subsequently, the roving and the textile reinforcement architecture define the properties of a single reinforced layer on the meso scale. Finally, combination and stacking of different layers result in the ma­­ terial characteristics on the macro scale and beyond on the structure level. Furthermore, this hierarchical view can be expanded by considering complex systems arising from joining components and by taking the mutual inter­

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action of different structures into account.

Additio­­nally, for fibre- and textile-reinforced components and systems, the resulting properties are significantly controlled by the fabrication process and can be influenced purposefully hereby. At ILK, numerical modelling of the processing of fibre-reinforced materials and structures is an integral part of the scalespanning design process. Hence, already in an early development stage alternate variants of process management can be compared and evaluated with regard to process-efficiency and achievable material and structural properties.

For developing efficient lightweight-structures in multi-material design, joining and bonding zones are of particular importance. Therefore, in an increasing number of cases the necessity arises to incorporate such areas in detail into the simulation models for evaluating the global system behaviour realistically.

The rapidly increasing computing power of modern computer systems is a substantial basis for achieving the capability to synergis­ tically combine and apply the appropriate analysis, modelling, discretisation and calculation methods across the different scales of fibrereinforced materials and systems step by step.

Therefore, in the near future it will be possible to take into account the complex structure/ property relationship (Figure 1) along the whole process chain [1].

Institute of Lightweight Engineering and Polymer Technology

Material modelling – Scale-spanning methods for exploiting the material potential Choice of material is essential for structural design tasks. Based on mathematical approaches, a scientifically sound description of the complex composite material behaviour enables an exact modelling of occurring physical phenomena. However, a closed solution of the resulting analytical framework is not always possible. To overcome such obstacles, nume­ rical material modelling within multiscale approa­­­ches is employed at the ILK (Figure 2).

This allows us both an in-depth understanding of the material behaviour and the identifica­­tion of relevant phenomena at the respective scales.

The objective of a robust numerical material modelling route is to purposefully utilize the appropriate scale to describe the governing phenomena with adequate accuracy.

Within our ILK approaches, the basic constituents fibre (or filament) and matrix as well as

Micro

Meso

their interactions in a matrix-embedded roving are numerically considered at the micro scale.

The resulting detailed understanding enables meso-scale considerations on single-ply level to identify the influence of different textile architectures. Subsequently, mechanical properties derived for the single ply are adaptively homogenised within a multilayer composite framework on the macro scale. On the structural level, numerical analyses of composite components and (sub-) systems are performed using the multi-layer properties.

The basic idea of the multi-scale material modelling approach is to transfer relevant information from the neighbouring lower level scale into the working scale using homogenisation techniques. This enables for example the usage of filament-matrix interaction results for modelling a homogenised roving material to be used for the modelling of the textile re­ inforcement structure. In a next step on the macro scale, the ply interactions between the

Macro

Figure 1: Complex structure-property relationship to be taken into account for simulation-based design of efficient lightweight structures in multi-material design.

Figure 2: Scale-spanning modelling within FEM – a formula for success for reliable material modelling.

Structure

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Which material to use where with what material properties?

 in % 62.0 60.7 59.4 58.1 56.8 55.5 54.2 52.9 51.6 50.3 49.0

a

Figure 3: Layout, preform and analytically determined distribution of fibre volume ratio in a generic turbine blade [2].

layer sequence

b

preform

single plies are considered which can be subsequently used to investigate the delamination behaviour for instance.

Structural behaviour – Realistic modelling of complex phenomena State of the art material modelling methods allow a reliable prediction of the complex material behaviour of composites. However, be­ sides the sole consideration of the geometry of the structure, its retroactive effect on the local mate­rial properties has to be incorporated into the design process. This is of special importance for structures exhibiting locally varying thicknesses. Subsequently, this is demonstrated for a double-curved fan blade.

The layout of the fan blade is characterised by a locally varying number of reinforcement layers (Figure 3 a). Due to the smooth surface of the finished part, the reinforcement layers are compacted non-uniformly during the infil­ tration and consolidation process. Consequent­ ly, the fibre volume ratio and therefore the material properties vary locally (Figure 3 c). The large number of different reinforcement layers is an additional challenge in the modelling and analysis of such structures.

The local thickness of the reinforcing layers as a result of the varying component thickness affects the local fibre volume ratio and thereby the local material properties. Fur­ther­ more, in regions of ply-drops, matrix accu­ mulations and the respective effect on the local fibre volume ratio have to be taken into account.

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c

distribution of fibre-volume ratio 

Current modelling methods allow for a con­ venient and closed design process. But they usually do not consider the differing local material properties with a sufficient spatial resolution. Such simplifications may lead to inaccu­ rate results in the FE analysis. One example is the determination of eigenfrequencies, where the local distributions of stiffness and mass have a major impact on the results. In the case of fan blades, falsely calculated eigenfrequencies may have serious consequences – in the best case this can cause the malfunction of single components, in the worst case whole systems can fail.

Therefore, novel modelling methods for complex, double-curved components with locally varying component thickness are developed and successfully applied at the ILK. These methods allow for the robust and practicable design of such components already in the concept phase. The dimensioning is conducted at the component scale, whereby the material is analysed on the macro scale. For this, the part thickness and the arrangement of the reinforcement layers are analysed automatically.

The resulting local material properties are calculated based on the local fibre volume ratio and are subsequently mapped onto the finite element mesh. This approach allows us to consider manufacturing-related boundary conditions and their impact on the structural behaviour already in an early stage of the design process. So, a realistic manufacturing-related model is available and enhances the analyses of manifold practically relevant phenomena, like layer-wise damping behaviour or the layerwise failure [2].

Institute of Lightweight Engineering and Polymer Technology

plain textile

draped textile

forming/draping

Process simulation – The material arises from the fabrication process The resulting material and structure proper­­ties of composites are primarily defined by the manufacturing processes and can pur­ pose­­­fully be influenced by process management. At the ILK, the design of corresponding manufacturing processes for composite struc­ tures is systematically supported using simulation methods. Based on combined virtual process and structure simulations, different manufacturing processes are simulated in an early stage of component development enabling both the evalua­tion of process efficiency and resulting material as well as component properties. The correla­tion between manu­ facturing parameters and structural as well as mechanical target values enables the analysis of corresponding interactions. For example, the influence of the sequence of tex­tile reinforcement layers on the surface texture of a composite part is pre-estimated and adjusted by simulating the compaction and solidification process [3].

Another example is the draping process.

Caused by the given geometry of a struc­ture, distortions of the binding patterns occur during draping of semi-finished textile pre­­forms (Figure 4), influencing the local material properties of the final composite component significantly. These manufacturing effects have to be taken into account in a subsequent filling simulation as locally different permeability values and in a following structural simulation as locally different stiffness and strength properties.

distorted textile binding pattern caused by shear stresses

In order to understand the influence of the resin transfer moulding (RTM) process on the mechanical properties of the final component or for an optimization of the process itself, an in-depth understanding of various physical phenomena in the heated RTM moulding tool is necessary. Therefore, the determination of the local process temperature, pressure and the degree of cross-linking is focused. Based on numerically or experimentally determined material parameters, such as the thermal conductivity, the specific heat capacity or the re­ action kinetics of the resin, the processing substeps preheating, filling, cross-linking reaction and cooling are investigated (Figure 5). Both the transient, spatially resolved degree of cross-linking of the polymeric matrix material and the associated mechanical properties as well as the residual stresses in the component can be determined numerically and are used in subsequent simulations. For this purpose, the results of the process simulations are transferred to the structural simulation enabling a re­ liable and realistic pre-calculation on the structural level.

Figure 4: The material arises from the fabrication process – Draping simulation for a textile preform [4].

System interaction – Combining complementary simulation methods Within the design process of lightweight components, often the focus is not only on the mechanical characteristics of the component itself but on its behaviour and its interaction with regard to the entire system.

This systemic approach is of special significance in the case of the simulation of crash and impact processes, of joining elements, of ero­sion

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5b

5a

Figure 5: Simulation of a) mould temperature distribution followed by simulation of b) filling and c) cross-linking for the determination of transient, spatially resolved property changes of polymer matrix and composite material.

Figure 6: Simulation of a multi-body system for the design of a lightweight pivoting mechanism using a coupled kinematic/FEM analysis.

Figure 7: Simulation of impact systems: a) Acceleration of impactor due to coupled electro- mechanical interaction, b) Impact due to purely mechanical interaction, c) wave propagation and material failure due to materials interaction.

7a

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5c

and friction systems, of kinematic sequence, of fabrication processes, to name only a few.

Furthermore, this approach has been shown to be very useful in the context of the design of complex testing rigs and procedures. Besides the standard FE methods, additional simulation approaches are used, like mesh-free and particle-based numerical techniques, multi-body and multi-physics simulations, advanced analytical models or information- and knowledge-based approaches. Hereby, the different simulation methods should not be regarded as mutually exclusive alternatives but as complements and should be used in combination [6].

For example, the combination of an analysis of a kinematic systems being subject to significant deformations and a stiffness and failure analysis may be done in a multi-body simulation. Hereby, a motion analysis is interconnected with a FE analysis (figure 6). Using this approach, it is possible to investigate the influences of elastic deformations of the single parts of the kinematic system on its dynamic response. Taking into account acting forces, deformations and stresses in the whole system leads to a deeper understanding of the chain of effects and shows roads for optimisation.

By using numeric multi-physics simulation methods, it is also possible to deeply analyse

7b

6

the complex effects of coupled transient electromagnetic-mechanical phenomena occurring in a newly developed impact testing rig. Here, the acceleration of the impactor resulting from electromagnetic induction, the impact process itself and the resulting structural behaviour of the fibre composite target can be evaluated within a single integrated simulation (figure 7).

First, the impactor is accelerated to the desired impact velocity by eddy current induction, then, it hits the target structure, which fails due to wave propagation processes afterwards [7].

For the simulation of highly dynamic processes causing greater deformation, failure and complex contact processes, different explicit FE systems are used. Doing so, for example both the safety and design concept of fan

7c

InStItUtE oF LIGHtWEIGHt EnGInEERInG anD PoLYMER tECHnoLoGY

8a

8b

modules and their individual fibre composite components can be evaluated (figure 8).

Therefore, the effects of blade loss on the following blades and on the containment structure as well as the fragmentation behaviour of the blade itself and the blade geometry as a function of the rotational speed are included in the modelling of the system.

The analysis of erosion and friction systems is characterised by relative movements of the contact partners, a material removal and the temperature development and a deformation behaviour with changing contact areas during the process. This can be demonstrated for the analysis of the complex contact and friction behaviour occurring in controlled rub-in experiments for compressor blades of a high-pressure compressor stage. The highly dynamic erosion system is simulated by the combination of a standard mesh-based FE analysis and a mesh-free particle method using a smoothed particle hydrodynamic

8c

approach (SPH). The material failure and abrasion behaviour as well as the heat development during the contact phase of the blade tip are evaluated (figure 9). The simulation results can directly be compared with the experimental results using virtual sensor application [8].

8d

Figure 8: Simulation of highly dynamical system interaction: a) model, b) separation of a blade and c) + d) deformation of containment.

When designing hybrid joining systems as a combination of rivet and adhesive bonds, the joining process itself as well as the velocity and temperature dependent deformation and failure behaviour of the joint must be considered [9]. In a coupled fluid-structure simulation besides optimized beading and positions of the adhesive the influence of the joining direction, process inaccuracies, joining speed as well as resulting joining forces and gap filling is analysed (figure 10 a). Subsequently, the results of this simulation are transferred to classic FE systems and a deformation and failure analysis of the joining system is carried out (figure 10 b).

Figure 9: Evaluation of the behaviour of highly dynamic erosion and friction events in a high-pressure compressor unit: comparison of experimentally and numerically determined results using coupled mesh-free and mesh-based methods: a) situation before rub-in, b) abrasion during rub-in [6].

9a

9b

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Fluid-Struktur-Interaktion

Fluid Raumfestes Netz

t1

t3

t2

t4

a

Figure 10: Simulation of joining systems a) glue distribution using a coupled fluid-structure analysis b) joint strength of a combined rivet/thick-film bonded joint under shear load.

Contact

Dr.-Ing. Bernd Grüber Head of Numerical methods Phone: +49 (0)351 463 38 146 bernd.grueber@tu-dresden.de

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Technische Universität Dresden

b

Conclusion Efficient lightweight structures using up-todate multi-material design methods are getting more and more in the focus of R&D due to the permanent increasing demand on reduction of climate-damaging emissions and retrenchment of fossil energy carriers in many indus­trial sectors. For such lightweight structures, the design process is strongly influenced by a complex interaction of material, fabrication, joining and system behaviour. Up to now, the high material-specific potential is not fully exploited.

Hence, at the ILK the development of coupled material-, process- and application-adapted simulation methodologies are expe­dited to fully utilize this potential. Striving for reliability, robustness, efficiency and sus­tainability of

both the design process and the lightweight structure, tailored simulation strategies have been developed by combining in-house deve­ loped simulation tools with commercially avail­ able ones. Hereby, scale-spanning simulation methods for predicting material, struc­­ture and system behaviour were made available. Within over 20 years of expertise, this approach and the developed tools have been experimentally validated and successfully applied to hundreds of basic, applied and joint research and development projects across many scientific and industrial sectors: ■ M aterials science, ■ Mechanical, civil, medical and systems en­gineering, ■ Marine, automotive and aerospace.

Literature [1] Grüber, B., Hufenbach, W.: Simulation von faserverstärkten Leichtbauwerkstoffen – Struk­tu­ren und Prozesse. InnoMateria – Kongressmesse zum Zukunftsthema innovative Werkstoffe, Köln 15.-16.

März 2011.

[2] Koschichow, R.: Auslegungsmethode mehrfachgekrümmter Bauteile aus Faserverbundmaterial mit kom­plexem Laminataufbau, in 9. HyperWorks An­­ wendertreffen für Hochschulen, Böblingen, 2015.

[3] Freund, A.: 2014. Numerische Untersuchung zum visuellen Eindruck von presstechnisch hergestellten Textil-Thermoplastverbunden. Technische Uni­ versität Dresden, Dissertation, 2014.

[4] Ebhart, T.: IPA, Technische Universität Dres­den: Institut für Leichtbau und Kunststoff­technik, 2016.

[5] Hufenbach, W., Maron, B., Mertel, A., Lang­­kamp, A.: Experimentelle und numerische Thermo­form­pro­ zess-Untersuchung zur Validierung von Umform­ simulationen von Textil-Thermoplasten. Brosius, A. (Hrsg.): Tagungsband zur 20. Sächsi­schen Fach­ tagung Umformtechnik. Dresden: TU Dresden, 2013, S. 100-109.

[6] Grüber, B., Hufenbach, W., Gottwald, R., Lepper, M., Zhou, B.: A new tool for the preliminary design of notched multilayered GF/PP-composites with cut-outs and a finite outer boundary. Procedia Materials Science 2, 2013, S. 25-33.

[7] Hufenbach, W.; Hornig, A.; Nitschke, S.; Lang­ kamp, A.: Through-thickness testing and parameter identification of textile reinforced thermoplastic composites for crash and impact calculations. 1st International Conference on Composite Dyna­mics (DYNACOMP), May 22-24, 2012, Arcachon, France.

[8] Hufenbach, W., Gude, M., Ebert, C., Andrich, M., Nitschke, S., Johann, E., Lang, T.:Experi­men­­tal and Numerical Investigation of the Blade Tip Contact Interaction of a High Pressure Com­pres­sor Stage.

DGM - European Symposium on Friction, Wear and Wear Protection, Karlsruhe, 2014.

[9] Gude, M., Langkamp, A.,Füßel, R., Mertel, A.: Robuste Fügetechnologien für hybride Leicht­bau­ weisen im Güterwaggonbau. Vortrag bei der CCeVArbeitsgruppe “Engineering, Klebtechnik und NDE”, Dresden, 2015.

InstItute of LIghtweIght engIneerIng and PoLymer technoLogy

❯❯ TAKING THERMOPLASTIC PROCESSES TO THE NEXT LEVEL ❮❮ Daniel Barfuß, Michael Krahl, Alexander Liebsch, Teresa Möbius

The production of functionally integrated lightweight structures requires efficient and resource-conserving process chains. The ILK research group for thermoplastic processing is following a comprehensive research approach: starting with the development of adapted semi-finished products and their pre-processing technology to the production of highly integrated component structures in novel combination processes. In order to analyse the complex interactions along the entire process chain the researchers use a multiscale process simulation.

Introduction Thermoplastic process chains offer a high potential in terms of time- and cost-efficient serial production. Here, near-net-shape lightweight structures with a high contour complexity can be realised in short cycle times and without additional post processing.

Beyond that, the possibility of integrating enhanced functions into the part during the manufacturing process is getting more and more attractive. Due to the realisation of highly functionalised components, cost-intensive assembly and joining processes can be reduced.

For an efficient process design, a continuous consideration of the entire process chain is eminently important (Figure 1). In this context the overall efficiency can be significantly increased by the synergetically merging of individual process steps to novel process technology combinations [1].

With the use of efficient process combinations, future process chains can be further shortened, resources can be preserved and costs can be reduced. Therefore, the activities of the research group for thermoplastic pro-

PProcess combination

Production of semi-finished products

Preforming

Consolidation

Process combination

Functionalisation

Figure 1: Continuous thermoplastic process chain from semi­finished products to highly functionalised component structures and the potential for com­ bining individual process steps.

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cessing are oriented along the entire process chain and comprise the following topics: ■ D evelopment, production and characterisation of novel thermoplastic semi-finished products with appropriate properties (compounds, films, tapes, full-impregnated continuous fibre reinforced thermoplastic composite sheets – so called “organo sheets”) ■ Design of resource-efficient and repro­ ducible preforming technologies as nearnet-shape tape laying and braiding of com­ plex-shaped hollow thermoplastic preforms ■ Development of novel moulds and process technologies for an efficient manufacturing of thermoplastic hybrid structures in injection moulding, pressing, pultrusion and ex­trusion processes Within the production of functionalised complex lightweight structures each step has a considerable influence on the component's me­chanical properties. Hence, the targets of the scientists are the development and provi­ sion of specific process-analysis tools and process-simulation tools along the entire process chain. In this context necessary input for struc­­tural simu­lation can be provided and manufacturing pro­cesses can be optimised by setting the appropriate process parameter combinations.

The ILK scientists have access to an unique machinery for the development of new largescale production processes. This allows the selection of an adequate process for each single application as well as an advanced combination of the processes. Using the results of current research activities, new tech­nology developments for serial production of textilereinforced thermoplastic lightweight structures are presented in this article.

Specific semi-finished products for efficient process chains An efficient and quality-oriented production of complex lightweight structures re­quires a fundamental understanding of the process re­lated material behaviour of the thermoplastic semi-finished products along the entire process chain. For this purpose, a long-standing know-how and excellent testing and processing facilities are available at the ILK and enable the analysis and implementation of actual manufacturing processes suit­­able for

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serial production. The scientists use a variety of standardised test methods as TGA, DSC, DMA and plate-plate-rheometer. In addition, viscosities of thermoplastic melts at different shear rates and temperatures of up to 500 °C can be measured with a High Pressure Ca­ pilla­r y Rheometer “Rheograph 75” from Göttfert.

The determined process-specific material properties are used subsequently for the execution of process simulations and are an important basis for the development of adapted thermoplastic semi-finished products with novel property profiles. To cite an example, the scientists develop new injection moulding compounds with specific fibre-matrix-configurations and carry out research in context of continuous fibre reinforced thermoplastic products. Using analytical and numeric com­puta­tional models, the impregnation process can be analysed and process parameters can be synchronised to achieve high quality semi-finished products.

The film stacking process is an established technology for the production of planar thermoplastic organo sheets. Through selective combination of thermoplastic films and fibre re­inforcements the property profile of organo sheets can be adjusted accordingly. For the production of the polymeric films, a special chill roll unit from Dr. Collin in combination with a film extrusion line is available at the ILK. Films with a width of 240 mm to 260 mm and a thickness of 0.075 mm to 2 mm can be manufactured. Furthermore, this unit allows the production of films from thermoplastic matrices up to a temperature of 420 °C. These films can be subsequently processed in the impregnation and consolidation process with the selected reinforcing fibres. In this regard, an individual production of semifinished products can be realised in a wide variety of material combinations. As an innovative example functionalised organo sheets with improved tribological properties should be mentioned, which can be used as sliding patches in friction- and wear-stressed com­ ponents. For this purpose, comprehen­sive investigations were carried out on the pro­ duction of modified composite structures within the research activities of the Collabo­­ra­ tive Research Centre 639 in cooperation with the Leibniz Institute for Polymer Research Dresden (IPF). It could be shown that the use of a PTFE-based matrix system enables

Institute of Lightweight Engineering and Polymer Technology

BioComp (short fibre reinforced)

BioSheet (endless fibre reinforced)

BioHybrid (composite structure)

the production of novel organo sheets with ex­cellent friction and wear properties, especially in contact with DLC-coated steel [2].

Consequently, from the aspect of functional integration, self-lubricating semi-finished products can be provided for applications in plain bearings or guide surfaces.

search project “BioHybrid”. Here, biobased thermoplastic cellulose esters with natural fibre reinforcements were used in various material configurations as oriented planar semi-finished products for the transmission of high loads and flowable compounds for the functionalisation of composite structures.

In addition to the production of planar or­gano sheets, the manufacturing of conti­nuous fibrereinforced tapes is another main focus of the research group for thermoplastic processing.

Within this research project all process steps beginning with the processing of raw material, the production of semi-finished products up to the production of the final part were set up and analysed in detail. The project partners demonstrated the practicality of the material system on a bi­­cycle rack that serves as a technology carrier (Figure 2).

The target is the production of functionalised and process-adapted tapes that are specifically adapted to the subsequent process steps, such as tape laying, tape braiding or pultrusion.

In different research projects technologies are developed to increase the production rate, to improve the quality of the tapes, to realise new fibre-matrix-combinations as well as to work out the possibilities for the integration of additional functional elements.

For this purpose, a modular melt impregnation and consolidation unit is available at the ILK. The system allows an individual adjustment of the impregnation unit for the processing of different material combinations and also enables the production of various tape geometries [3].

Figure 2: Biobased material building kit for the realisation of hybrid lightweight structures.

For this biobased material building kit the ILK, together with the top technology cluster ECEMP, was honoured with the prestigious 2015 AVK Innovation Award in the category ”Research/ Science” by the German Industry Association for Reinforced Plastics (AVK).

Efficient consolidation processes for thermoplastic hollow structures

Special attention is always given to the systemic consideration of the entire process chain – from raw material production to the production and utilisation to recycling – as well as to the resource efficiency potentials associated with new materials, processes and design methods.

Another main focus within the research group for thermoplastic processing is the production and functionalisation of continuous fibre re­ inforced thermoplastic profile structures. The aim of the work is the development and delivery of novel and efficient manufacturing methods for the production of fibre reinforced thermoplastic (FRTP) profiles as well as the enhancement of the process and structural understanding by advanced process simula­ tion models (Figure 3).

For instance, a novel material system based on renewable raw materials for the production of hybrid lightweight structures with a load-bearing function was developed within the re-

Two basic manufacturing approaches are considered for the production of functionalised profile structures. The production of profile structures and their functionalisation

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

a

Figure 3: a) braiding design; b) tape braiding; c) braided tape preform; d) consolidated tape preform; e) computertomographic quality assurance.

b

c

can be either done in one intrinsic or in two successive process steps. The intrinsic manu­ fac­turing of functionalised profile structures shortens the process chain, while the serial production approach allows a continuous production process with a very efficient pro­duc­ tion line.

For both approaches pre-impregnated tape materials with a thermoplastic matrix are used as a semi-finished product. The appli­ cation of fully impregnated tape products prevents the complicated process step of impregnation in the component production process. As a result, the process time for the production of profile structures can be signi­ ficantly re­duced. In addition, the use of semifinished tape products is beneficial for high me­chanical properties due to an elongated fibre alignment as well as to a substantial reduction in fibre damage during the entire production process.

Due to the specific material behaviour of tape products, braiding of tapes requires adapted processing equipment. Therefor, the ILK de­ veloped material-specific tape carriers for the processing of 3 to 6 mm wide tapes. In addi­ tion, technology-specific developments are taking place to improve the braiding quality and to expand the production diversity. Accor­ ding to the application-specific requirements, the ILK produces braided tape preforms with a load-adapted braiding architecture by varying braiding patterns, braiding angles and combinations of unidirectional, bi- or triaxial laminate lay-ups. Generally, deposition rates of up to 1 kg/min are possible. In combina­­tion with a comprehensive process automa­ tion capability, the tape braiding technology shows a high potential for industrial serial applications [3].

For the manufacturing of complex shaped FRTP profile structures, the blow moulding

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d

e

process is an advantageous production method. Depending on the complexity and the required degree of deformation, tapes or hybrid yarns are used as semi-finished products for braiding. In the blow moulding process, a preheated and molten preform is pressed against the tool surface by applying an internal pressure; the preform is formed three-dimensionally and is subsequently consolidated. Due to innovative heating and tooling technologies, cycle times of less than three minutes can be achieved.

A continuous process approach such as pul­trusion is suitable for the production of straight profiles with a constant cross-section.

In combination with the braiding technology, profiles with adapted fibre architecture can be pro­duced. At the ILK, a thermoplastic pultru­ sion system was developed, which processes the braided tape preforms into FRTP profiles.

The pultruded profiles are cut individually to the required length and functionalised in further manufacturing steps. The integration of sealing and resistant thermoplastic liners is possible as well and has already been validated. The available machine set-up is now used to address open questions for an intended pilot plant [3].

FRTP profiles with PA, PPS and PEEK matrix material have been successfully produced in the pultrusion as well as the blow moulding process. The resulting component qualities with porosities of less than 1%, fibre volume contents of up to 60%, wall thickness deviations of less than 3% and the elongated fibre alignment meet the challenging standards in aviation industry.

Accompanying the technological research, process analysis and simulation models for each production step are developed. The focus of these activities is on draping and forming processes as well as on thermal and chemical influences during consolidation. Depending on the requirements of the process, a compre-

Institute of Lightweight Engineering and Polymer Technology

hensive process chain analysis is performed by a combination of various submodels. For example, the method of the ”embedded elements” is used for unit cell modelling of textiles [4] to simu­late the draping process of tape braids in undercutting geometries of contoured functional elements. Thereby, the re­quired forming forces during processing as well as the resulting fibre architecture are de­rived in order to obtain input for the structural simulation and failure analysis (Figure 4).

Functionalisation of thermoplastic composites The functionalisation by means of injection moulding represents the last part of a continuous process chain for the production of thermoplastic composite structures. For this purpose, research projects have been carried out in recent years [5-8], in which predominantly plane thermoplastic structures with organo sheets or metallic sheets have been used. In case of using organo sheets, the prefabricated semi-finished products are heated to their melting temperature, inserted into an injection moulding tool and formed three-dimensionally as a result of the tool closing movement. Subsequently, the still warm organo sheet is overmoulded with a thermoplastic melt in the same tool. Thereby, an adhesive bond between the liquid injection melt and the heated organo sheet surface is created. In contrast, the application of metallic sheets requires a previous sheet metal forming process. Additionally, surface treaments e.g. laser structuring or adhesionpromoting agents are necessary for a highly loadable joining.

In order to investigate the fundamentals of the injection moulded hybrid structures, a generic basic test specimen (Figure 5) was

Process chain analysis Design

Process simulation

Component

Testing

developed at the ILK, thus various questions concerning the processing of different material combinations can be investigated. The test specimen is divided into six areas by means of which investigations can be carried out. The shape filling behaviour of different rib geometries (1), the connection of injection moulding compound to metallic inserts or organo sheets (3, 6) and the overmoulding of inserts (4) can be analysed. In addition, test plates with a defined fibre orientation can be produced for mechanical mate­rial characterisation (5).

The determined material parameters can be used for the design of the hybrid component structures as well as for adapting process parameters.

Figure 4: Process chain analysis for a con­ tinuous development of intrinsic hybrid structures.

Based on the findings in context of the functionalisation of organo sheets by means of injection moulding, experimental and numerical investigations on the functionalisation of composite hollow profiles are currently carried out at the ILK [9, 10]. One of the essential challenges is the support of the hollow profile against the injection pressure during overmoulding. The high injection moulding pressure, which applies on the surface of the hollow profile, would lead to a collapse of the hollow profile itself if no suitable supporting measures are used. At the ILK various strate-

Figure 5: Generic basic test specimen for the investigation of overmoulded organo sheets.

Technische Universität Dresden

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Institute of Lightweight Engineering and Polymer Technology

Figure 6: Functionalisation of hollow profiles: a) simulation of the pressure distri­ bution acting on the hollow profile during overmoulding; b) structural simulation of the supporting behaviour dependent on the support medium; c) generic demonstrator structure.

gies for a process safe overmoulding of thin walled hollow profiles are developed and evaluated. In addition to experimental inves­ tigations, extensive nume­rical simulations are carried out to identify the stresses acting on the hollow as well as to illustrate the interaction between injection moulding pressure, hollow profile and supporting medium. For this purpose, new simulation methods are deve­loped that allow the transfer of data from process simulation to structural simu­la­ tion (Figure 6). Using these methods, appro­ pri­­ate support media can be characterised and subsequently validated experimentally.

a

b

c

contact

Dr.-Ing. Michael Krahl Head of Thermoplastic processing Phone: +49 (0)351 463 42 499 michael.krahl@tu-dresden.de

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Technische Universität Dresden

Based on these findings, process design guidelines are derived which enable the selection of appropriate support media sui­ table for different app­lications.

Conclusion The development of sustainable and efficient process chains requires a continuous consi­ deration of the whole process itself, starting with the production of the semi-finished products to the functionalised structural components. In addition, a profound understanding of the process specific material behaviour is essential in order to detect interactions between single process steps and to adjust process parameters accordingly. The development of novel manufacturing processes is further assisted by setting up a continuous process simulation, including the virtual in­ spection of impregnation, draping and mould filling procedures. This enables the ILK researchers to optimise the respective processes and tools and ensures a reproducible quality of the components. This continuous approach is the key to the reali­­sation of sustainable ther­­moplastic process chains and will help to establish novel lightweight technologies in industrial applications.

Literature [1] Bürkle, E.; Wobbe, H.: Kombinationstechnologien auf Basis des Spritzgießverfahrens, Carl Hanser Verlag GmbH Co KG, 2016.

[2] Kunze, K., Andrich, M., Modler, N., Kupfer, R., Leson, A. Leonhardt, M., Scheibe, H.-J. , Lehmann, D.: Wartungsfreie Gleitsysteme auf der Basis von Faserverbunden mit thermoplastischen Matrices, TribologieFachtagung 2014, Gesellschaft für Tribologie, 22.-24. September 2014, Göttingen, Deutschland.

[3] Garthaus, C., Witschel, B., Barfuss, D., Rohkamm, A., Gude, M.: Funktionalisierte Faser-Thermoplast-Profil­struk­ turen, Lightweight Design, (1) 2016, p. 40-45 .

[4] Freund, A.: Numerische Untersuchung zum visuellen Eindruck von presstechnisch hergestellten Textil-Thermo­ plastverbunden. Dresden, Techn. Univ., Fak. Maschinenwesen, Diss., 2014.

[5] Modler, N.; Hufenbach, W.; Maaß, J; Liebsch, A.; Troschitz, J; Vogel, C.: Werkstoffgerechte Fügesysteme für Strukturbauteile in Mischbau­-weise; 7. Chemnitzer Karosseriekolloquium; 8.-9. October 2014; Chemnitz.

[6] VDI Zentrum Ressourceneffizienz GmbH: Kurzanalyse Nr. 3 und Doku­mentation des Fachgesprächs: Kohlenstofffaserverstärkte Kunststoffe im Fahrzeugbau – Ressourceneffizienz und Technologien, VDI ZRE Publika­tionen, Berlin, 2013.

[7] Kaufmann; Bürkle; Bider: Leichtbauteile mit Thermoplastmatrix. Kunststoffe 3 (2011), p. 106-109.

[8] Stegelmann, M.; Krahl, M.; Garthaus, C.; Hufenbach, W.: Integration of textile reinforcements in the injectionmoulding process for manufacturing and joining thermoplastic support-frames; 20th International Conference on Composite Materials; 19.-24. July 2015; Kopenhagen.

[9] Liebsch, A.; Kupfer, R.; Hornig, A.; Gude, M.: Numerical investigation on the stress distribution in hollow composite profiles due to overmolding; 20th In­ter­­­national Conference on Composite Materials; 19.-24. July 2015; Kopenhagen.

[10] Liebsch, A.; Andricevic, N.; Maaß, J.; Geuther, M; Adam, F.; Hufenbach, W.; Gude, M.: Batterieträger in Hybrid­ bauweise – Kombination aus thermoplastischem Faserverbund und Aluminium ersetzt Stahlbauteil; Kunststoffe 9 (2015), p. 126-129.

Institute of Lightweight Engineering and Polymer Technology

�� Well shaped and quickly reacted �� Sirko Geller, Andreas Gruhl, Michael Müller, Oliver Weißenborn

The field of highly stressed fibre-reinforced components is strongly domi­ nated by thermoset matrix systems with continuous fibre reinforcement.

However, appropriate preforming solutions for textile structures and conso­ lidation technologies using fast curing matrix systems are considered as main requirements for a broad use of such high-performance structures within industrial applications. In this context, the simulation-based development of efficient manufacturing processes, taking into account the interaction of materials, processes and component properties, is gaining importance.

The department of thermoset processing and preforming

1. Design and analysis of manufacturing processes

The thermoset processing and preforming group at the ILK is mainly focused on charac­ terization, modelling and simulation of reactive processes, simulation-based design and pro­ duction of high-performance fibre-reinforced composite structures, plant and process de­ velopment for innovative preforming concepts as well as research on novel materials, semifinished products and the development of corresponding processing technologies. In addition, process development for manufactu­ ring active composite structures is a further research focus, in which the comparatively moderate processing conditions of thermosets are used in a targeted manner. Thanks to outstanding technological equipment, a variety of both prototypic and series processing tech­ nologies for thermoset matrix systems can be used. Focus areas are prepreg processing, infusion and injection processes, braiding and filament winding as well as polyurethane pro­ cessing. Beyond this outstanding technologi­ cal equipment, the interdisciplinary coope­ ration among several departments of the ins­­ titute allows for comprehensive research in the respective fields. In the following sections selected works from the fields of process de­ sign and analysis, braiding and polyurethane processing are presented.

The development of modern production pro­ cesses is characterized by a competition bet­ ween different technologies as well as different materials. Due to the numerous parameters available for process optimization, an interdis­cip­ linary process design is essential. Thermoset processing technologies, such as the resin trans­­­fer molding (RTM), offer the advantage that they can be automated and provide a high degree of freedom in design and functional in­ tegration. However, the complicated and errorprone impregnation process itself is considered to be a major drawback for series production.

Therefore, scientist at the ILK are focusing on increasing the process understanding significant­ ly by using simula­tion and process-moni­to­ring methods to investigate the relation between process parameter and material properties.

1.1 Combined design of part and mould The smart analysis of production processes already starts during the stage of part develop­ ment and is considered to be a major require­ ment for efficient and reproducible manufactu­ ring processes of fibre-reinforced composites.

In this context, the ILK has an excellent exper­ tise in the fields of novel processing technolo­ gies and appropriate material models. Since the properties of composites are strongly in­

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Institute of Lightweight Engineering and Polymer Technology

Figure 1: Implementation of the side element of the InEco® demonstrator vehicle: CAD-model including periphery (left), lower mould with presentation of the preforming process (middle), com­ plete and ready-to-assemble compo­ site part (right).

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Technische Universität Dresden

fluenced by the impregnation and consolida­tion process, the comprehensive design of these modern structures has to include a sound feasibility and efficiency study apart from a mechanical and thermo-mechanical evaluation.

To achieve these demands, the design of the part itself and the construction of the mould are two simultaneously running tasks, enabling the efficient development of highly integrative lightweight structures. The side frame of the prototypic automobile InEco®, developed at the ILK is a prime example of the combined design approach [1]. The CFRP component has me­ tallic inserts and connecting elements, which are joined form-locking and material-locking during the RTM process. Mould-integrated cores and slides permit the realization of the complex component geometry with several undercuts. In addition to the excellent level of weight reduction, the structure shows a high degree of functional integ­ration and illustrates the potential of thermoset processing solutions developed at the ILK (Figure 1).

derstand the process both in terms of material behavior and process parameters and to con­ trol them in a targeted manner.

1.2 Process monitoring and analysis

the mould are dependent on the location and time. Any deviation from the target state has potential effects on the final properties of the component. For this reason, new methods for process simulation are developed at the ILK (see chapter numerical methods). These are used to perform virtual parameter studies and thus to reduce the time-consuming trial-anderror methods. Various in-situ measurement methods are used to validate the numerical studies. Thermocouples and ultrasonic sen­ sors allow documentation of the real process

The infiltration process during RTM is charac­ terised by transient matrix flows with multiply phases and phase transitions on one hand as well as heat conduction and convection phe­ nomena on the other hand. Therefore, the RTM process is considered to be a complex, multi-physical system. The effects and mate­ rial properties are also decisively influenced by the exothermic crosslinking reaction of the used resin. In order to comprehend all these phenomena, it is therefore necessary to un­

The researchers at the ILK can draw on a wide range of testing methods for the characteriza­ tion of material properties. Using thermal ana­ lysis (see chapter test methods), important parameters such as the temperature- and crosslinking-dependent viscosity can be deter­ mined. Based on these measurements, a first estimation of the resulting processing times and the present flowability of the resin is possible. The required holding time in the mould is also derived.

For the development of resource-efficient thermoset manufacturing processes, a deep understanding of the interaction between material behavior and process parameters is required. In the case of complex-shaped com­ ponents with relatively large wall thicknesses, the above-described physical effects within

InstItute of LIghtweIght engIneerIng and PoLymer teChnoLogy

temperature and degree of cross­linking. The mold filling is monitored with the aid of capaci­ tive or pressure sensors.

The methods for process analysis developed at the ILK are characterized by a holistic, inter­ disciplinary approach (Figure 2). Knowledge from material characterization is combined with numerical simulations and sensor data from production. This allows for a compre­ hensive understanding of complex problems such as the efficient and reproducible process management in the RTM process. As a result, process times can be reduced and error images can be understood and avoided.

material and process parameters

mould

CAD-model temperature

process simulation comparison of solutions

2. efficient preforming using braiding technology composite part The braiding process is an efficient techno­ logy for producing textile preforms for various structural components. One of the largest radial braiding machines is used at the ILK, allowing for processing of up to 288 rovings to braided structures with fibre angles between 5° to 89°. In addition, the integration of up to 144 rovings in the longitudinal direction of the structure is possible. The mechanical proper­ ties of braided components as well as the enhancement of the braiding process itself are investigated in numerous research and deve­ lopment projects. At present, the focus is on modification of braiding technology for the realization of complex branched structures or usage of tapes (see chapter thermoplastic processing) as well as increase of specific mechanical properties, for example by novel braiding patterns.

During braiding, rovings are placed with a defined pattern on a braiding core, resulting into an evenly distributed fibre structure with

high­quality optical properties, making them suitable for visible components with high demands for surface quality. Apart from the radial braiding machine with 288 bobbins, a two­field axial braiding device with 48 and 72 bobbins can be used for the manufacture of braided preforms. Whereas radial braiding machines are commonly used for complex shaped structural components with a multi­ layered composition, axial braider allow for processing rovings to braided preforms with a high efficiency and low process­related costs.

Current investigations focus on the implemen­ tation of novel braiding patterns to improve strength and stiffness in the final composite part. By evaluating the modifiability of the brai­ ding technology through mechanical tests of the composite structure using torsion and internal pressure test, the range of novel brai­ ding patterns is extended constantly. Figure 3 shows current modifications of braiding pat­

Figure 2: Combined development of processes using virtual and experimental methods.

Figure 3: Experimental studies on processing novel braiding patterns with reduced fibre deflection: flange connection for chemical plants (left), prototypic structure of a drive shaft for aircraft engines (right).

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Figure 4: Braiding of branched structures using the specifically developed adjustable braiding eye: Braiding of a prototypic demonstrator for an A-pillar-connec­ tion (left and middle), prototypic structure of a bio-inspired branched lightweight-structure (right).

Contact

Dipl.-Ing. Sirko Geller Head of Thermoset processing and preforming Phone: +49 (0)351 463 42 197 sirko.geller@tu-dresden.de

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Technische Universität Dresden

terns with a reduced amount of intersec­tions, resulting into a higher amount of elongated fibres. By reducing fibre intersections and the adjustment of their angles, the resulting composite stiffness and strength could be increased significantly. The introduction of these results into series production pro­ cesses has the advantage of increasing the range of possible industrial applications by generating tailor-made mechanical properties from high elongations at break and energy absorption capacity to a very high stiffness and strength. In this context, prospective applications in­clude pressure tanks, drive shafts and piping tubes with superior me­ chanical properties.

3. Novel polyurethane processing technologies

In recent years, the ILK was able to set new standards for the braiding technology.

In 2009 for instance, a novel braiding bobbin with active control of the yarn tension was developed, reducing filament damage during processing drastically and generating high quality braided structures. Apart from that, modular housings to avoid release of carbon fibres and an adjustable braiding eye have been developed, which are by now intro­­duced to industrial braiding machines. The adjustable braiding eye allows for a defined control of fibre angle and position close to the braiding mandrel. In cooperation with the Institute of Solid Mechanics of the Technische Universität Dresden, this complex kinematics was developed to im­prove the fibre compo­ sition on polar caps of pressure tanks and to generate parts with a branched geometry.

Taking all the developments of the ILK into account, the diversity of composite structures could be extended significantly with main­ taining a high level of process efficiency at the same time (Figure 4).

the development of an efficient production process for active lightweight structures with integrated piezoelectric sensors and actuators based on the Long Fibre Injection (LFI) technology is part of the research activities (see chapter CRC/TR 39). Further projects aimed at the integration of magnetorheological liquids in open-cell polyurethane soft foams in order to actively influence the mechanical properties of the composite by magnetic fields. In addi­ tion, material models were developed to predict the complex material behavior [2].

Polyurethane is a versatile matrix material with a wide range of mechanical and morphological properties, depending on the composition of the reaction components polyol and isocyanate. Both compact and cellular polyurethanes are predestined for the usage in fibrereinforced composites. At the ILK, the poten­ tial of polyurethane as matrix material for lightweight components was identified at an early stage, leading to innovative approaches in numerous research projects. In the frame­­work of the Collaborative Research Centre/ Transregio 39 “PT-PIESA” (subproject B06),

Current investigations focus on the expansion behavior of foamable polyurethanes, e.g. for the impregnation of textile reinforcements. In this process, the matrix material is sprayed on textile semi-finished products on a defined spraying route. With the ongoing chemical reaction of the polyurethane, the matrix cures and expands in the closed mould. Due to the resulting internal pressure, the textiles are pushed against the mould geometry and im­pregnated by the liquid parts of the expanding matrix. Based on prelimi-

InstItute of LIghtweIght engIneerIng and PoLymer teChnoLogy

nary studies on the impregnation behavior of selected textiles, advanced processes for the manufacture of textile­reinforced cellular com­ posites and novel lightweight sandwich structures were developed and successfully imple­ mented [3­5] (Figure 5).

In this context, the design of the manufactu­ ring technology according to the processed materials gained in relevance. By adjusting de­ fined parameters, such as mould temperature, the morphology of the pore structure, e.g. size, orientation and distribution, can be adapted to meet the demands of mechanical loads and constraints. The high energy absorption capa­ city of cellular materials during impact load and

Attalea speciosa

Fibre-reinforced rigid PUR foam Compact material

Figure 5: Polyurethane spraying unit (left) and manufactured sandwich structures with textile-reinforced top layers (right).

Fibre-reinforced layer with gradient pore structure

Homogeneous core layer

the failure behavior in general is mainly based on the microstructure of the material. Biological models for optimized impact structures are found among fruits, which have to absorb high impact energies to protect the seed of the plant. The fruit of the pomelo and attalea spe­ ciose were chosen as biological structures with a high potential for biomimetic composites based on integral rigid foam structures.

The transfer of bio­inspired principles of the attalea speciosa, such as a graded cellular ma­ trix with partially oriented fibre reinforcement, into novel polymer composites was among the main research targets in the field of polyure­ thane processing (Figure 6). Scientists at the ILK were able to adapt established technolo­ gies, such as the polyurethane spray coat method and the reaction injection moulding method for the processing of polyurethanes to generate foam structures with a locally defined distribution of pores and fibres. In comparison to conventional foamed structures, higher im­ pact forces and energies can be dissipated.

Figure 6: Microscopic image of the structure of Attalea speciosa (left) and the transfer to partially fibre-reinforced rigid polyurethane foams (right).

literature [1] W. Hufenbach, J. Werner, J. Kiele: Elektromobilität in Ultraleichtbauweise, Engineering Leichtbau ATZextra May 2013, Vol. 18, Issue 2, pp 42-46.

[2] E. Dohmen, M. Boisly, D. Borin, M. U. V. Kästner, M. Gude, W. Hufenbach, G. Heinrich, S. Odenbach: Advancing towards polyurethanebased magnetorheological composites, Advanced Engineering Materials, Vol. 16, 2014, Issue 10, pp. 1270-1275.

[3] M. Gude, S. Geller, O. Weissenborn: Integral manufacture of fiber-reinforced sandwich structures with cellular core using a polyurethane spray-coat method, Cellular Materials – Cellmat 2014, Dresden, 22.-24. Oktober 2014.

[4] M. Gude, S. Geller, O. Weissenborn: Studies on the impregnation of textile semi-finished products using a polyurethane spray-coat method, Journal of Plastics Technology, Vol. 11, 2015, Issue 1, pp. 211-228.

[5] S. Geller, O. Weißenborn, M. Gude, A. Czulak: Impregnation studies and mechanical characterization of cellular natural fibre-reinforced composite structures. Polimery 61 (2016), 2, pp.

125-132.

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Institute of Lightweight Engineering and Polymer Technology

�� Joining Composites efficiently �� René Füßel, Wikentij Koshukow, Robert Kupfer, Martin Pohl, Juliane Troschitz, Christian Vogel

For a successful application of multi-material-design in highly loaded lightweight structures, appropriate technical and economical joining systems are required, which are specifically tailored to material, manufacturing process and application. Thereby, the specific material structure in the joining zone can be adjusted to enable efficient joining processes and high connection strengths.

1. Introduction

2. Thermoforming of holes

example since they enable a highly repro­­ ducible and fast joining process and provide detachability. To produce the required holes, a thermoforming technique was developed at the ILK, which – contrary to the drilling – causes no damage to the fibre structure.

Hereby, the fibres are shifted aside in the warmed and molten matrix by means of a tapered pin. To enhance the efficiency of the process, the hole-forming is synergistically combined with component manufacturing by integrating the required hole forming kine­ matics (pin tool and counterpunch) into the forming mould (Figure 1 a). With this in-line for­­ming, the downstream process step for hole pro­duction can be completely avoided. Process studies with a specially developed tool show that in-line hole forming does not induce an extension of the cycle time of the pressing process. Moreover, neither prepa­ration nor follow-up of the joining zone is necessary.

For local load introduction into composite structures, bolted connections are an establis­ hed joining method across the industry, for

The mechanical performance of connections with thermoformed holes is influenced by the varying fibre content and fibre direction

As they enable a highly efficient production at short cycle time composites with a thermo­ plastic matrix are currently being focussed for large-scale manufacturing of lightweight structures. In addition, the tool-bound pro­ cessing offers a high potential to integrate required joining or preparation steps directly into the component’s manufacturing process.

Hereby, the characteristic features of the thermoplastics, in particular their meltability and weldability can be utilised in a targeted manner for the material-compatible joining of such structures. The article presents selected solutions for the material and process-approp­ riate joining of textile-thermoplastic compo­ sites, highlighting the ILK´s main focus in joining technology.

a

Figure 1: Process concept of in-line thermoforming of holes (a), fibre configuration beside the thermoformed hole (b), measured and calculated deformations of a test structure with thermoformed hole under pin loading (c).

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Technische Universität Dresden

b

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Institute of Lightweight Engineering and Polymer Technology

nearby the hole (Figure 1 b). For the syste­ matic and efficient analysis of the characteris­ tic material structure, the micrograph analysis and computer tomography are used, whereby the image evaluation is largely automated. In addition, specially adapted methods for highresolution material analysis were developed, such as the calibrated X-ray image evaluation or micro-calcination [HMW+11]. Building on this, analytical modelling approaches were deve­loped at the ILK, allowing a realistic re­ presentation of the materials complex pheno­ meno­logy nearby the hole. These structural models are incorporated into FE simulations to predict the bearing behavior of thermo­formed holes under pin load (Figure 1 c) [HGK+11].

Derived application-oriented design and di­ mensioning guide­­lines enable the lightweight engineer to exploit the up to 50 % higher load-bearing capacity of joining zones with thermoformed holes [Kup16].

3. Long term behaviour For bolted joints in composite materials the bearing failure load can be increased sig­ni­ ficantly by supporting the joining zone in la­­­ minate thickness direction e.g. through app­ lication of an additional clamping force. To des­cribe the creep induced decrease of the clamping force, an extended joint diagram was developed at the ILK. In this diagram, the time dependent behaviour of the compo­ site joining partners is represented by an iso­ chronous stress-compression surface, derived from creep curves under compression load in laminate thickness direction. For the expe­­­ rimental determination of these long-term material properties unique multi-point com­ pression testing devices were developed.

However, the long operating periods of joints in constructions and vehicle applications (>10 years) cannot be tested efficiently by classical creep tests. Hence, a testing procedure based on the time-temperature superposition prin­ ciple was formulated and validated, which enables accelerated testing and data acqui­ sition within several hours [PKK+15].

4. Process-integrated embedding of inserts The principle of moulding holes can also be used to integrate metal inserts in thermoplas­ tic composites. For this purpose a two-parted pin tool is applied that is equipped with a me­

a

b

pin actuator pin actuator

insert pin tip

pull-out forceinsert overtorque pin12 tip 4 kN c Nm 3 pull-out force 8 overtorque 12 4 2 6 kN g Nm sin ted k 4 rea rcut c 3 jus oc in de ad ion l 1 t un 8 a t ro 2 2 6 0 0 g n si ted k 4 rea ut jus oc inc derc ad ion l 1 un tat

0

2 0

ro

Figure 2: Splitted pin tool for integrating metal inserts in fibre-reinforced thermoplastics (a), different types of inserts (b) and influence of insert design on load-bearing behaviour (c).

tallic insert (Figure 2a). By moving the pin forward a hole is formed and the insert is pre­ cisely positioned flush with the composites surface. As with the thermoformed holes, the opposite surface is formed by a counterpunch (cf. Figure 1 a). When retracting the pin actua­ tor after consolidation the pin tip is separated automatically and the composite part can be demoulded.

This process is suitable for integrating a va­riety of different insert types – especially with strong axial undercuts (Figure 2 b).

Manu­­­facturing studies demonstrated a pro­ cess reliable filling of the undercut with fibres and matrix by the counterpunch. Due to this form-fit, high pull-out forces can be achieved as shown in experimental studies (Figure 2 c) [TKH13]. Furthermore the outer contour of the insert can be designed non-round to rea­ lise protection against rotation, which has major significance especially for threaded bushes.

The main advantages of the process-integ­ rated embedding of inserts are the prevented fibre damage and the elimination of additional joining steps as it is necessary e.g. for ultra­ sonically embedded threaded bushes. Current research focusses on computer tomographic (CT) analyses of the complex material struc­ ture nearby the insert to determine the in­ homo­­­geneous three-dimensional fibre orien­ tation with locally varying fibre contents and d­irections.

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5. Thermoclinching To join metallic components with thermoplas­ tic composite structures, processing sequen­ ces from the thermoforming of holes and the classical clinching process are combined to the new joining technology Thermoclinching.

Developed in collaboration with the Laborato­ rium für Werk­stoff- und Fügetechnik (LWF), the Thermo­­­­clinching technology intends a plas­ tic deforma­tion process, whereby the compo­ site is locally heated, shifted through the prepunched metal sheet and compressed from the backside to generate a form-fitting joint (Figure 3 a). Compiling a defined fibre orien­ tation of the composite in the neck and head area (Figure 3 b) and without the ne­cessity to apply any additional or ancillary joining ele­ ments, a high lightweight potential of the Thermoclinched joining zone can be achieved.

Experimental studies of Thermoclinching joints show that high failure loads as well as predic­ table failure behaviour can be achieved by adap­tion of processing parameters. Com­pared to classic joining technologies like bonding, no ex­­tensive pretreatments of the joining zone are necessary, qualifying the Thermo­clinching tech­­ nology for the integration in robust process chains with short cycle times. Further­­­­more, inherent low joining forces allow the develop­ ment of light and manageable joining tools.

Beside manufacturing studies and loading tests, numerical analyses of the joining pro­ cess support the systematic Thermoclinching process development. Figure 3 c exemplary

a

b

pin

composite

pin

composite

c

Figure 3: Schematic illustration of the thermoclinching process (a), micrograph analysis of thermoclinched joint (b) and comparison of computed tomography analyses (c) with results of the numerical process simulation (d).

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Technische Universität Dresden

counterpunch

sheet metal

counterpunch

sheet metal

d

pin

composite

pin

composite

opposes a CT analysis with a numerical simula­ tion of the composite’s deformation behaviour during Thermo­clinching.

6. Loop connections for thermoplastic composites In addition to the repeatable ability of ther­mo­ for­ming, the material-inherent weldability offers potentials for the development of adapted joining technologies for thermoplastic compo­ sites. One approach is the efficient implemen­ tation of loop connections into lightweight com­ posite structures. Hereby, special mounting flaps are prepared at the flat preform which are formed and welded to the main body of the part during the manufacturing process (Figure 4 a).

For a defined geometry of the joining zone, a metallic insert is positioned coaxially to the axis of the loop. This insert can be re­moved after manufacturing or can remain in the joining zone as a load introduction element. Bearing tests on loop connections show distinct rela­ tions between the force-displacement-behavi­ our and the geometry of the welding zone.

While at flat welding zones an early crack ini­ tiation nearby the load introduction element can be observed, an increased profiling of the welding zone leads to significant higher initial failure loads (Figure 4 b).

Beside their joining functionality, loop connec­ tions enable additional function integration if they are designed as guided movements like hinges. For optimised slide bearing behaviour, tribologically adjusted slide patches from car­ bon fibre fabric with PTFE-modified matrix material were developed and tribo-mechani­ cally characterised. It was shown, that these slide patches also can be integrated into the composite part during manufacturing and en­ able a much better friction and wear behaviour compared to the basic composite material (Figure 4 a) [HKP+13].

7. Thermoactivated pinning (TAP) Based on the z-reinforcement principle, the Thermoactivated Pinning takes up the idea of classical nailing and turns it into a dynamic and automatable joining process. It enables the connection of thermoplastic composites by means of metallic pins without the need of drilling a hole or other preparation steps. The essential feature of this new joining technolo­

Institute of Lightweight Engineering and Polymer Technology

4a

loop connection

1.

1. mounting flap

5a

loop connection 2.

composite

heating module

pin

pin-holder

composite

heating module

pin

pin-holder

3.

2. slide patch metallic load 3. introduction element pin 5b

5c

pin

force force

mounting slide patch metallic load flap introduction element 16 flat welding zone 4b kN 16 12 flat welding zone kN 10 12 final failure 8 initial failure 10 6 final failure 8 4 initial failure 6 2 profiled welding zone 4 0 0 1 2 3 mm 5 2 displacement profiled welding zone 0 mm 0 1 2 3 5 displacement

gy is the warming of the metallic pin, so it can be gently embedded into the overlapping composite components (Figure 5 a).

With this fast technology, form-locked and combined joints can be established in a reli­ able and robust way. TAP is predestined for the joining of hollow structures because oneside accessibility is sufficient. With a robot‑ guided pinning device it is possible to auto­ matically build complex pin patterns with indi­ vidual pin positions and different pin angles (Figure 5 b).

To analyse the bearing behaviour of these pin connections, in situ CT is used, providing detailed information about the local defor­ mation and failure phenomena in the joining zone during mechanical testing (Figure 5 c) [HBK+14].

8. 3D-Hybrid Technology For highly loaded lightweight components, multi-material design with fibre-reinforced plastics and metals is particularly suitable. This allows the respective property profile to be used targeted in order to achieve a high light­ weight grade. The 3D-hybrid technology deve­ loped at the ILK was the first-time approach to combine metal sheets, continuous fibre-re­

Figure 4: Concept of process-integrated manufacturing of a loop (a), influence of the geometry of the welding zone on the failure be­haviour (b).

roving joining partner roving joining partner

Figure 5: Process sequence of the thermo­ activated pinning technology (a), pattern of pins with variable pinning directions (b) and in situ CT analysis of a one-pin joint (c).

inforcements and long-fibre-reinforced thermo­ plastics ribs (Figure 6 a). By integration of mul­ tiple assembling steps within one manufactu­ ring process the pro­duction efficiency of hybrid structures is in­creased significantly. In order to realise the one-step production by com­ pression or in­jection moulding special bonding agents are used. They enable high strength connections during the crash deformation.

To understand and to design the structural be­ haviour and the corresponding manufacturing process, advanced material and process mo­ delling methods are used. Based on these mo­ dels predictions of safety, durability and fai­lure of hybrid parts can be made (Figure 6 b).

The first industrial scale technology demon­ stra­­­tor was an automotive B-pillar (Figure 6 c). Manufactured in a one-step process the hybrid structure showed equivalent failure behaviour with significant weight reduction capabilities compared to its metal original [MAM+15].

9. Laser-textured in-mould joining In addition to steel, lightweight metals are becoming increasingly important for multimaterial lightweight solutions. Especially the combination of low density materials like

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Institute of Lightweight Engineering and Polymer Technology

a

magnesium with thermoplastic composites offers lightweight potential for large-scale manufacturing. However, the tar­geted exploi­ tation of their positive mechanical and techni­ cal properties is only possible, if the interface between the different mate­rials is designed properly. Here, especially adhesive strength and corrosion resistance have to be optimised in order to develop durable and highly load­ able lightweight structures.

c

continuous fiber reinforced thermoplastic sheet metal long fiber reinforced thermoplastic

b

Figure 6: 3D-hybrid-technology (a), comparison of structural simulation and experimental bending tests (b) and automotive B-pillar demonstrator (c).

a

thermoplasticc thermoplasti

magnesium magnesium

100 µm µm 100

1 mm mm 1

b

Using the efficient moulding and forming technologies known from thermoplastic processing, these interfaces can be manu­ factured with high reproducibility. Injection moulding for instance is suitable to create mounting elements with intrinsic protection against corro­sion due to electrochemical decoupling of the connector and the light metal structure. With process-compatible pretreatment methods like laser-texturing of the interface areas, high-strength bonds between thermoplastics and magnesium can be established in-process (Figure 7a).

Based on extensive analyses of the processstructure-property-relations of this kind of dissimilar joints, dimensioning guide­lines for the interface design can be provided (Figure 7b).

10. Combined joining methods for hybrid structures Figure 7: Thermoplastic rib applied on a lasertextured magnesium sheet via in­jection moulding (a) and specimen with different texturing parameters after mode I testing (b).

a

Figure 8: Exemplary failure illustration of an adhesively bonded riveted joint (a), cross section of the joining zone during in situ CT-analysis (b) and finite element model of an adhesively bonded riveted joint under shear load (c).

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Technische Universität Dresden

b

metal c

composite

adhesive layer

rivet

The thermo-mechanical performance of multi-material lightweight structures with adhesively bonded joints can be further improved by combination with other joining methods such as riveting, bolting or pinning.

Hereby, the advantages of each type of joint are combined in order to enhance the overall performance of the individual joint. However, the prediction of the damage and failure be­ haviour for such combined joints is highly complex. Due to the interactions between adhesives, metal and composite joining part­ ners and fasteners different modes and lo­ cations of damage, failure and post-failure occur (Figure 8 a).

To analyse the progressive failure behaviour e.g. of adhesively bonded riveted joints, the simultaneous application of destructive and non-destructive testing methods is necessary.

The in situ CT provides detailed online-infor­ mation about deformation, failure initiation and crack propagation during mechanical tes­

Institute of Lightweight Engineering and Polymer Technology

ting (Figure 8 b). At ILK it is applied for the development of advanced phenomenologically based deformation and failure approaches for such combined joints. By implementation into finite element simulation, complex joints in various multi-material structures can be mo­ delled efficiently (Figure 8 c) [FGM16].

Conclusions The development of efficient and light joining solutions requires an interactive cooperation of experts along the entire development chain: material, design, simulation, manufac­ turing, testing, quality assurance and costs.

Hence, the research group for joining techno­

logies of the Institute for Lightweight Structures and Polymer Techno­logy works as an interdiscipli­nary team, which develops application-oriented solutions in the field of multi-material joining technology. There­fore it focusses two approaches: On the one hand established joining solutions are modified and applied to specific joining tasks, material com­ binations and load cases. On the other hand, novel material-adapted joining solutions are developed, analysed and evaluated concer­ ning their application potential. With that in mind, we pursue a holistic material-indepen­ dent development approach for joining sys­ tems incorporating technology, design, ma­ terial structure and application conditions.

contact

Dr.-Ing. Robert Kupfer Head of Joining technologies Phone: +49 (0)351 463 38 749 robert.kupfer@tu-dresden.de

ILK joining research topics: Development and testing of material- and process-adapted joining technologies Manufacturing studies and process analyses Destructive and non-destructive testing of joining zones and connections Development of analytical and numerical models for the description of the local material structure n Simulation of joining processes and numerical analysis of the structural behaviour n Derivation of practical design guidelines n Integration of joining procedures in industrial manufacturing processes and tools n n n n

Literature [FGM16] Füssel, R.; Gude, M., Mertel, A.: In-situ X-ray computed tomography analysis of adhesively bonded riveted lap joints. ECCM17, München, 26.-30.06.2016.

[GHK+15] Gude, M.; Hufenbach, W.; Kupfer, R.; Freund, A.; Vogel, C.: Development of novel form-locked joints for textile reinforced thermoplastics and metallic components. Journal of Materials Processing Technology 216 (2015), pp 140-145.

[HBK+14] Hufenbach W.; Böhm H.; Kupfer R.; Pohl M.; Hornig A.: Thermoactivated pinning – An innovative technology for the joining of fibre-reinforced thermoplastic composites. Joining Plastics – Fügen von Kunststoffen 8 (2014) [3], pp 184-189.

[HGK+11] Hufenbach, W.; Gottwald, R.; Kupfer, R.; Spitzer, S.: Bolted Joints with moulded holes for textile reinforced thermoplastic composites. ICCM 18, Jeju (Korea), 21.-26.08.2011.

[HHK10] Hufenbach, W.; Helms, O.; Kupfer, R.: Gestaltung von textilverbundgerechten Fügezonen mit warmgeformten Niet- und Bolzen­löchern. Zeitschrift Kunststofftechnik 6 (2010), pp 255–269.

[HKP+13] Hufenbach W.; Kupfer R.; Pohl M.; Böhm H.; Stegelmann M.: Manufacturing and Analysis of Loop Connections for Thermoplastic Composites. Procedia Materials Science 2013, doi: 10.1016/j. mspro.2013.02.017.

[HMW+11] Hufenbach, W.; Modler, N.; Winkler, A.; Kupfer, R.: Characterisation of the local fibre volume content nearby moulded holes in textile-reinforced thermoplastic components. Inproceedings of the 5th ETNDTConference, 19.-21. September 2011, Ioannina (Greece), pp 447-451.

[Kup16] Kupfer, R.: Zur Warmlochformung in Textil-Thermoplast-Strukturen - Technologie, Phänomenologie, Modellierung. Ph.D. thesis, Technische Universität Dresden, 2016.

[MAM+15] Modler, N. ; Adam, F. ; Maaß, J. ; Kellner, P. ; Knothe, P. ; Geuther, M. ; Irmler, C.: Intrinsic lightweight steel-composite hybrids for structural components. In: Materials Science Forum. Trans Tech Publications, Switzerland, 2015.

[PKK+15] Pohl, M.; Kupfer, R.; Koch, I.; Modler, N.; Hufenbach, W.: Determination of the Long-Term Properties in Laminate-Thickness Direction of Textile-Reinforced Thermoplastic Composites under Compression Using Time-Temperature-Superposition. Adv. Eng. Mater. (2015), doi: 10.1002/adem.201500475.

[TKH13] Troschitz, J.; Kupfer, R.; Hufenbach, W.: Prozessintegrierte Einbettung von Lasteinleitungselementen bei der presstechnischen Fertigung von endlosfaserverstärkten Thermoplasten. Tagungsband Technomer, Chemnitz 14.-15.11.2013, pp 1-9.

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Institute of Lightweight Engineering and Polymer Technology

�� Testing of Materials, Semi-finished Products and componentS at ILK�� Christoph Ebert, Jörn Jaschinski, Michael Müller, Thomas Behnisch

Advanced knowledge and comprehensive equipment on the research field of non-destructive and destructive material, substructure, component and system testing and characterisation for the different classes of materials are main topics at the Institute of Lightweight Engineering and Polymer Techno­ logy. The development of novel material adapted or component specific testing methods and the realization of complex test stands for most realistic loading are focal points of the testing group.

Introduction The knowledge of the material behaviour ­is very important for the design of lightweight structures. Especially the stiffness and strength characteristics dependent on the loading conditions are fundamental input parameters for structural assessment. Further the determination of thermal and thermomechanical properties for lightweight design and for the development of adapted manufacturing processes is a key element of material characterization. Damage and failure phenomena and processes inside of the material can be detected and analysed by nondestructive testing methods. The results of these analyses can be input for the development of advanced material models. Load tests on components and systems with party very complex loading conditions close to rea­lity are carried out to validate developed design methods and material models. For these advanced tests load and structure specific test stands have to be developed.

Characterisation of materials, semi-finished products and substructures Conventional destructive testing of materials, semi-finished products and substructures this very day gives important inputs for the understanding of material behaviour. Especially for fibre reinforced plastics and their characteristics which can be finally determined only after

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Technische Universität Dresden

consolidation, testing is essential for reliable strength values. For the resulting challenges the ILK is very well equipped in the fields of static, quasi-static, cyclic and highly dynamic testing. Tension tests with axial forces of some newton up to more than 1000 kilonewton can be realised for various testing temperatures. The strength and stiffness characteristics during different loading conditions, e.g. tensile, bending, compression and shear tests, can be determined by a broad range of mechanical, optical and electrical strain measurement methods.

The thermal and thermomechanical analysis of materials for lightweight engineering and especially of polymers is a very important standard tool for material characterisation.

For the processing of plastics for instance the determination of glass transition temperature or the melting area are common methods also for incoming inspections. If these methods are correctly used, a holistic data analysis of the manufacturing quality of fibre reinforced plastics can be maintained. In combination with mathematical methods a cost-, timeand resource-efficient optimisation of the manufacturing processes is possible.

By the Thermo-gravimetric Analysis (TGA) essential information about the limi­ tation of use of polymers can be generated.

Institute of Lightweight Engineering and Polymer Technology

A main goal of thermal analysis is the in­­ vestigation of the process related properties of polymers during manufacturing of fibre re­inforced structures with polymeric matrix.

During vacuum infiltration of textiles in a closed RTM-mould highly complex physical and chemical processes take place. A tran­ sient inhomogeneous temperature field is caused by the anisotropic heat conduction of the fibres. In addition phase changes in the polymer occur as a result of thermal or chemical effects. At first the polymeric resin is in a liquid state in order to allow a good impregnation of the fibre structure. In the course of the infiltration cycle the viscosity of the resin is increasing and the polymer is gelling. At this stage the material is in a viscoelastic state. The demoulding of the structure after the curing process is performed below glass transition temperature when the resin has reached an elastic state.

For the analysis of the different phenomena described above the ILK uses many different measurement methods. The cross-linking is characterized by the Differencial Scan­ ning Calorimetry (DSC). For this investi­ gation the hypothesis of proportionality of measured heat flow and reaction rate is used.

In addition the reaction enthalpy can be determined and evaluated as a characteristic value.

In figure 2 the cross-linking reaction of an epoxy based adhesive film is presented [3].

In combination with a Rotational Rheo­ meter additional effects can be analysed.

A comparison of the graphs in figure 2 shows,

This effect can be described by kinetic models and integrated into FE-simulation models. The execution of process simulations plays a central role at ILK. The quality of these simulations is ensured by internal determination of the re­­­quired material properties. The thermal ana­ lysis generates important information for process control and the resulting properties of the final parts. Based on this knowledge the manufacturing processes can be adapted, im­ proved and shortened. For the assessment of the used methods, models and assumptions additional measures for quality control can be performed. Specimen, extracted from a pro­ duced part can be analysed by Dynamic Mecha­nical Analysis (DMA) (figure 3).

Within this analysis mechanical (stiffness) and thermal (glass transition) properties can be validated. By this the post-cure conditions and the resulting properties of a RTM process can be correlated and validated.

For non-destructive testing of fibre reinforced plastics different methods are used. Beside thermography the ultrasonic scanning inspection is used very often at ILK. During these

Figure 1: Analysis of thermal degradation of PEI at typical processing temperatures, measured with TGA and DSC [2].

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For an intelligent process development first of all the knowledge of the maximum working temperatures, e.g. specific ambient conditions at a defined time, is important in order to avoid damage of inner chemical bonding. During an extrusion of high performance tubes made of polyetherimide (PEI) a sub­stantial pre-damage of the polymeric structure at typical processing temperatures was observed. As shown in figure 1 the dwell time at maximum process temperature is the most critical parameter.

that the viscosity at first decreases with in­ creasing temperature (physical effect) and afterwards an increase of several orders of magnitude caused by the cross-linking reaction (chemical effect). Furthermore a shift of the chemical cross-linking reaction to higher temperatures occurs with increa­sing heating rate.

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The thermal degradation behaviour of a ma­terial plays an important role in both, the phase of product use [1] as well as during the processing [2]. So TGA can be used for root cause analysis or to find explanations for changing behaviour caused by thermal degradation.

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investigations high spreading and damping of sonic waves caused by the inner boundary surfaces (Fibre/matrix-interface) occur. Therefore the scanning resolution and the maximum thickness of the structure are limited for the use of ultrasonic based methods. To overcome these limits the coMPuTEr ToMogrAPhy method with micro focus X-ray source [4] can be applied. Depending on the specimen size a resolution of a few micrometres per voxel can be realized. For small specimen with maximum dimensions of 150 mm and a maximum weight of 2 kg a nanotom 180 NF system with 180 kV micro focus X-Ray source and area detector is used. Large structures and systems with heights up to 2500 mm, diameters up to 1000 mm and mass of 200 kg are analysed with a v|tome|x L450 system with a 300 kV micro focus X-ray source, a 450

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kV macro focus X-ray source and line as well as area detectors.

With two In-sITu-coMPuTEr ToMogrAPhy (in-situ-CT) systems the ILK is equipped with a powerful combination of methods for material diagnostics. It enables the detection and tracking of the damage or failure evolution inside the structure at microscopic scale during mechanical loading. With in-situ-CT the influence of individual damage events and mechanisms on the nonlinear stiffness degradation can be analysed. Beside a loading unit for compression and tension loading [5,6], which can be integrated in v|tome|x L450 for in-situCT analysis, a novel test arrangement is used.

It consists of a tension/compression testing unit with a maximum force of 250 kN and an additional torsion cylinder with a maximum moment of 2000 Nm for combined loading.

This unit is surrounded by a computer tomograph with a 160 kV micro focus X-Ray source with tungsten target [7]. Here the X-Ray source and the detector rotate around the specimen as it is in medical computer tomographs.

In the following section in-situ-CT based results of tension specimens with central open hole made of carbon fibre reinforced epoxy resin are presented. The specimens are built up by a layup of 16 layers [45°, 0°, -45°, 90°, 45°, 0°, -45°, 90] s. The specimens are loaded in several steps until a maximum load of 65 kN without final failure of the specimens. The maximum load level was defined by quasi-static test series, where the final failure occurs at 70 kN. The specimen is clamped by joint heads and jaws to prevent torsion loading of the specimen in the area of load introduction (figure 4).

InStItUtE oF LIGHtWEIGHt EnGInEERInG anD PoLYMER tECHnoLoGY

The results of these investigations show some effects, which were not expected directly.

Pretest series show already the force relaxation by strain increase in the specimen which occurs directly after reaching the load step.

Because of the needed time of 15 minutes for one complete computer tomography measurement no specimen movement and no change of strain is allowed during the measurement for good image sharpness. Therefore the force is reduced by 2 kN after reaching a load step to anticipate the relaxation of the load strand.

The small unloading doesn’t cause the closing of inertial cracks because the strain nearly keeps constant. The analysis of the tomography images allows the visualization of the single laminate layers and an assessment of the damage (figure 5).

It is expected, that the fibre layers directed in loading direction are carrying the load. In the area of the hole of course stress deflections and an excess of stress, which cause failure of single layers in this area. But first failure already at a load level of 12 kN in fibre layers oriented perpendicular to loading direction is not expected. At a load level of 25 kN cracks in -45°/45°-layers are clearly visible. The specimen shown in figure 6 failed early in the last load step. This may be caused by the multiple preloading. The results show the necessity to consider damage of composites before failure also in simulation. Especially it is important for composite with brittle matrix or high fibre volume content in combination with endurance loading.

contact with surrounding casing elements was realized [8] which is shown in figure 7.

Figure 4 (left): Installation situation of specimen for open hole tension.

Here contact events in the compressor and the turbine of aircraft engines, for instance the contact between compressor blade and casing segment or the rubbing of labyrinth seal systems placed between the single compressor or turbine stages in the engine were focused. To reach high efficiency of compressor and turbine in all operating ranges the control and minimisation of the gaps of blades and vanes to the adjacent parts and the sealing gaps play a decisive role.

Figure 5 (right): Crack pattern through all layers at 60 kN, material semi-transparent, cracks marked red.

Actual used materials like titanium or nickel alloys reached its stress limits in modern aircraft engines. Furthermore the thermal limits of the integrated rubbing liners are reached, which cause the necessity to develop new

Figure 6: Loading regime for tensile specimen with selected crack.

Testing of components, assemblies and systems In addition to destructive and non-destructive testing capability for materials and subcomponents the ILK exhibits an extensive knowledge in the field of structural testing of components, assemblies and systems. Adapted or novel test rigs were developed in many research projects for various tasks to test complex structures under loading conditions close to reality. Especially for the development of unique test stands for roTATIonAL TEsTIng the ILK has long-time experience. In the German funded research project AeroBlisk (BMWi) and the research projects E-Break and Lemcotec within the 7th EU framework programme a test centre for experimental analysis of rotating aircraft engine components in

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Figure 7 (left): Rubbing test rig ADP with test rotor for blade rubbing tests.

Figure 8 (right): Rubbing of labyrinth seals on metallic structures.

liner materials and mechanisms for gap control for future engines. In AeroBlisk the interaction of rotor blades and liner segments was focused. In E-Break fundamental knowledge of friction and wear behaviour during rubbing of labyrinth seals was generated. The seal fins of labyrinth seals or the blade tips rub in the counterpart during specific manoeuvres in flight, which cause high forces and especially very high temperatures. The analysis of the rubbing behaviour is needed to understand the influence of engine speed or radial rub-in velocity on the occurring forces and tem­peratures.

Contact

Dr.-Ing. Christoph Ebert Head of Testing methods and experiment Phone: +49 (0)351 463 39 636 christoph.ebert@tu-dresden.de

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The multifunctional rotational test centre developed at ILK features two testing chambers. In these chambers a casing segment is moved radially towards a rotating compressor disc to analyse the rubbing of compressor blades. For investigations on the rubbing behaviour of labyrinth seals different topologies (material and structure) are moved radially as well as axially towards a rotating test disc with seal fins (figure 8).

The maximum speed for the disc is 19,900 revolutions per minute. For the rubbing maximum infeed rates of 1.25 m/s in radial direction and 50 mm/s in axial direction of the sealing counterpart can be achieved. The re­ sulting forces are recorded in radial, axial and circumferential direction by 3-Axis-force sensors. High-speed pyrometers with a minimum spot size of 0.4 mm² enable the mea­surement of the temperatures at fin or blade tip and on the friction surface of the casing segment.

Furthermore the exact positons and paths of movement are recorded. Fur­thermore the insitu strain measurement at 2 aerofoil positions by strain gauges and telemetry system for the rubbing of compressor blades is performed.

In figure 9 the recorded signals over time and the corresponding casing position is presented.

On the left upper side the rising strain at aerofoil with growing rubbing depth is visible. The upper right diagram shows the rising temperature in the contact zone. The lower part of the figure displays the rising reaction forces (left: radial, right: axial and circumferential) with growing rubbing depth.

The assessment of wear is also a focal point of the investigations. Conclusions on the deformation behaviour during these ex­treme rubbing conditions based on the cap­tured weight reduction before and after rubbing, the geometrical changes at blade, fin tips and friction lining as well as the micro structure wear phenomeno­ logy can be made. For labyrinth seals a significant influence of infeed rate on wear behaviour was observed for some topologies. For these structures wear is a mixture of plastic defor­ mation and abrasion with varying percentage over infeed rate. High infeed rates cause mainly plastic deformation whereas low infeed rates are more abrasive to the rotating structure. For blade rubbing tests the geometry of the aerofoil, the combination of the friction partners, the rotational speed and the infeed rate show the most significant influence on the occurring forces and deformations as well as the resulting temperatures in the contact area.

Conclusion The knowledge of the material properties as well as the deformation, damage and failure processes is vitally important for the design of lightweight structures and systems with high load-bearing capacity. Based on the comprehensive test equipment and the con­soli­dated knowledge of the scientists

Institute of Lightweight Engineering and Polymer Technology

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a holistic analysis of the material characteristics can be achieved. Thereby the characte­ risation can be performed starting with the determination of thermal and thermomecha­ nical behaviour of the material followed by an analysis of stiffness and strength properties of the semi-finished products and substruc­ tures under static, quasi-static, cyclic and

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highly dynamical loading and ending with very complex loading tests on structures and systems. Furthermore novel test rigs and testing methods are de­veloped and established at ILK. The test results are used as input parameters for detailed structural simulations and for validation of advanced design methods.

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Figure 9: Results of a blade rubbing test.

Literature [1] Hufenbach, W.; Modler, N.; Winkler, A.; Kupfer, R.: Characterisation of the local fibre volume content nearby moulded holes in textile-reinforced thermoplastic components. In: Paipetis, A. S., Matikas, T. E., Aggelis, D. G., et al.

(Hrsg.): Emerging Technologies in Non-Destructive Testing V. Boca Raton: CRC Press, 2012, S. 447-451. - ISBN 978-0-415-62131-1.

[2] Stegelmann, M.; Lucas, P.; Müller, M.; Grüber, B.; Modler, N.; Grajewski, F.: Pipes for Flying – High-Performance Pipe Systems for Applications in Aircraft Construction. In: Kunststoffe international 12/2015, Carl Hanser Verlag, München, 2015.

[3] Müller, M.; Maaß, J.; Gude, M.: Curing behaviour of thermoset adhesive promoters for intrinsic hybrid designs during production processes. EUROMAT 2015, Warsaw, 22.09.2015.

[4] Anjali Singhal, James C. Grande and Ying Zhou (2013). Micro/Nano-CT for Visualization of Internal Structures. Microscopy Today, 21, pp 16-22. doi:10.1017/S1551929513000035.

[5] Gude, M., Hufenbach, W., Ullrich, H.-J., Czulak, A., Danczak, M., Böhm, R., Zscheyge, M., Dohmen, E., Geske, V., Computer tomography-aided nondestructive and destructive testing in composite engineering, Composites Theory and Practice R. 12, nr 4, p. 279-284.

[6] Hufenbach, W.; Böhm, R.; Gude, M.; Berthel, M.; Hornig, A.; Ručevskis, S.; Andrich, M.: A test device for damage characterisation of composites based on in situ computed tomography, Composites Science and Technology, Volume 72, Issue 12, 23 July 2012, Pages 1361-1367, ISSN 0266-3538, http://dx.doi. org/10.1016/j.compscitech.2012.05.007. (http://www.sciencedirect.com/science/article/pii/S0266353812001807).

[7] Böhm, R.; Stiller, J.; Behnisch, T.; Zscheyge, M.; Protz, R.; Radloff, S.; Gude,M.; Hufenbach, W.: A quantitative comparison of the capabilities of i n situ computed tomography and conventional computed tomography for damage analysis of composites, Composites Science and Technology, Volume 110, 6 April 2015, Pages 62-68, ISSN 0266-3538, http://dx.doi.org/10.1016/j. compscitech.2015.01.020. (http://www.sciencedirect.com/science/article/pii/S0266353815000585) [8] Hufenbach, W., Gude, M., Ebert, C., Nitschke, S., Andrich, M., Lang, T., Johann, E.: Experimental and numerical investigation of the blade tip contact interaction of a high pressure compressor stage. European Symposium on Friction, Wear, Wear Protection and Related Areas (Karlsruhe, Germany, 6-8 May 2014)

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�� function integration at

MATERIAL AND SYSTEM level �� Martin Dannemann, Robin Höhne, Pawel Kostka, Peter Lucas, Anja Winkler

Scientists at the ILK see function integration as a physical expression of their interdisciplinarity. It is this blend of close cooperation between disciplines such as mechanical engineering, electrical engineering, computer science and a systemic approach that enables the institute to develop and implement sustainable, competitive solutions.

1. Function integration according to the Dresden Model Scientists at the ILK primarily associate the term “function integration” with intensive interdisciplinary and transdisciplinary cooperation. In contrast with the conventional understanding of function integration, the institute’s approach not only combines functions and reduces part numbers at component level, but also factors in system-level interactions that arise as a result of phenomena in a number of different “worlds”. A high degree of interdisciplinary cooperation aimed at the exploitation of existing – yet often unused – potential is therefore a prerequisite for the development of function-integrative lightweight engineering solutions. The greatest challenge involved is the establishment of a culture of close cooperation and simplified exchange between experts from the fields of lightweight engineering, electronics and software development. In too many cases, the conventional monodisciplinary approach fails to meet the requirements placed on function integration projects, not least because adherence to clear disciplinary boun­ daries creates a barrier to mutual support which prevents scientists from developing a shared, comprehensive understanding of the overall system.

It was against this backdrop that the ILK set up the Expert group on function integration.

Experts from a wide range of disciplines including lightweight engineering, mecha­

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tronics, electrical engineering and computer science make the group an one-stop provider of function-integrative lightweight engineering solutions. In particular, the group’s wellco­ordinated, multidisciplinary team is ideally set up to combine development efforts in a variety of fields, thus paving the way for products that not only go far beyond the state of the art, but also feature “built-in copyright protection”.

One special area of focus is the integration of mechanical, electronic, acoustic, haptic, actuatory and sensory functions into overall systems. Typical challenges on the path towards function-integrative solutions include ■ t he development of novel construction methods, ■ the identification of structural integration concepts, ■ the adaptation and combination of existing manufacturing processes and the development of new manufacturing processes, ■ the selection and positioning of suitable sensors, ■ the networking of sensors and interfaces which facilitate human-machine interaction, ■ the long-term behaviour of embedded sensors, ■ the development and adaptation of data analysis techniques (e.g. data mining, arti­ ficial intelligence, neural networks, evolu­ tionary algorithms, etc.) and ■ interactions between embedded sensors/ actuators and the structure itself.

InStItUtE oF LIGHtWEIGHt EnGInEERInG AnD PoLYMER tECHnoLoGY

Close interdisciplinary cooperation and a comprehensive knowledge pool enable the ILK to offer its customers function-integrative solutions developed entirely in-house. In particular, the institute draws on synergetic expertise gained in a wide range of disciplines such as aviation, e-mobility, energy, mechanical and plant engineering, medical technology, consumer products, bespoke machine building and safety equipment.

a function-integrative composite fan blade – developed entirely in-house by the ILK The self-adapting, self-diagnostic intelligent fan blade for aircraft engines shown in figure 1 is an excellent example of close interdisciplinary cooperation at the ILK. Developed as part of the SmaComp project initiated by the European Centre For Emerging Materials and Processes (ECEMP), the blade draws on over ten years of experience gained by the ILK in the design and manufacturing of fan blades for aircraft engines in its role as a Rolls Royce University Technology Centre.

The CFRP fan blade is the first in the world to feature integrated ■ ■ ■ ■ ■

sensors, actuators, microelectronics, energy supply and tailored data analysis software.

Figure 1: Intelligent fan blade with integrated actuator technology.

Mechanical, sensory, actuatory and electronic requirements formed the foundation for the various development threads that combined to form the overall development process (see figure 2). Sensors and actuators were positioned in a way that not only ensured the optimum exploitation of sensory and actuatory functions, but also minimised the influence of functional elements on the mechanical characteristics of the structure

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itself. The evaluation of sensor signals with the aid of data analysis enabled the description of structural behaviour, which in turn provided a basis for the implementation of a control concept for active functions.

This involved the execution of softwareand hardware-in-the-loop testing at the ILK, with coupled multiphysics simulation playing a vital role in ensuring rapid, targeted concept realisation.

It was also necessary to refine the RTM manufacturing process for use in combination with composite fan blades, and in particular to guarantee the safe, damage-free embedding of sensors and actuators (see figure 3). The ILK is well set up to carry out the necessary modifications, as its expertise in the field of draping and filling simulations enables both the realistic modelling of manufacturing processes and the early identification of any negative impact those processes might have on sensors, actuators or the data analysis unit.

Figure 3: The manufacturing and testing of active CFRP structures.

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The implementation of the control concept for active functions also involved the use of hardware to supply power and both process and transmit signals. Embedded strain gauges record vibration signals, which are then processed and analysed using an integrated microprocessor. An embedded bluetooth module wirelessly sends the user

relevant information such as frequency spectrum and vibration amplitude, thus enabling the continuous monitoring of dynamic structural properties. Microelectronic components are powered by an integrated, wirelessly chargeable battery. The integrated piezoceramic module makes it possible to realise an active vibration damping system embedded into the material itself. The system delivers a substantial reduction in undesirable vibration amplitudes, for example those encountered during taxiing, take-off and landing (see figure 3). The integration of the entire system – sensors, actuators and electronic components – into the fibre-reinforced composite structure protects it from outside influences and manipulation without restricting its programmability.

Software for the system was developed parallel to the aforementioned development threads. Among other benefits, the early incorporation of software development into the overall development and design process supported the selection of suitable sensors and actuators. The resultant availability of pre-existing knowledge of the structure’s response behaviour (software-in-the-loop) also cut out unnecessary development loops.

What is more, the early implementation of complex control algorithms opened the door to additional options in areas such as active structural health monitoring (SHM).

Institute of Lightweight Engineering and Polymer Technology

Further examples of function-integrative lightweight engineering for a variety of sectors These types of complex, innovative solutions are developed entirely in-house by the ILK, and enable all partners to secure their market position over the long term. The institute’s work in this area draws on longstanding, successful cooperation with a range of pres­ tigious partners. The following section pro­ vides a brief insight into the application of the ILK’s systemic approach within the framework of projects in five key areas.

Function-integrative fibre-reinforced composite structures Special research projects in the Collaborative research Centre SFB 639 resulted in the successful integration of sensor networks into fibre-reinforced thermoplastic compo­ sites and the development of functional interfaces able to create combined mecha­nical and electrical connections between multiple embedded functional components. The use of compliant mechanisms also en­abled the development of movement-gene­rating systems that exploit the deformation capacity of individual mechanism members in order to produce highly in­tegrative mechanisms with zero play. Re­search carried out within the framework of the FUNHUB project focuses on the targeted use of com­posite mounts to reduce vibration in the masts of storage and retrieval systems [7]. The LAKS project again exploits the relatively high level of damping offered by polymers, in this case as a means of developing noise-absorbing polymer structures for aircraft engines. This also involves the development and application of calcula­ tion models compatible with fibre-reinforced composites [11].

Structural health monitoring The objective of research projects SFB/TR39, DREAM, SENSO, KombiSens and FELAF is to integrate sensor-actuator networks into fibre-reinforced composite structures as a means of monitoring the structural health of components and wider systems (e.g. [1-3]).

On the one hand, this requires the refinement of the manufacturing processes involved in order to ensure both compatibility with the

fibre-reinforced composite and the proper embedding of the networks into the structure without causing damage to them. On the other hand, participating researchers are also de­veloping, simulating and experimentally vali­ dating the data analysis algorithms required (e.g. [15, 16, 17]).

E-mobility Working in cooperation with leading European partners from the worlds of science and industry, the ILK is developing solutions for novel drive and energy transmission systems characterised by a high degree of dependency on component weight as part of research pro­jects MotorBrain, 3CCar, OSEM-EV and eDAS-EV [8-10]. The projects aim to tackle the key challenges facing the e-mobility sector by developing novel lightweight engine concepts and innovative wireless charging mo­ dules.

Process development The widespread use of function-integrative structures is dependent on the availability of efficient, series-ready manufacturing pro­ cesses. It is with this in mind that the TEMAG and SFB/TR39 projects target the development and refinement of manufacturing pro­ cesses for fibre-reinforced thermoplastic composites featuring integrated conducting paths, electronic components and piezoceramic modules [12-14].

Active system adjustment Active vibration damping in both thin-walled structures and moving systems represents an important area of application for functionin­tegrative components. Using the example of a robot-guided tool spindle, the BOSS project demonstrated the use of active vi­ bration damping during the machining of fibre-re­inforced composite components.

The ILK de­veloped and implemented a piezo-driven compensator module which can be installed in series between the tool spindle and robotic hand in order to reduce process-related vibration. Targeted actuator control makes it possible to limit vibration throughout the entire machining system (i.e. tool and robot), thus enhancing both the quality and the producti­vity of the machining process [4].

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Contact

Dr.-Ing. Martin Dannemann Head of Function integration Phone: +49 (0)351 463 38 134 martin.dannemann@ tu-dresden.de

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Technische Universität Dresden

Literature [1] Filippatos, A.; Höhne, R.; Kliem, M.; Gude, M.: A composite-appropriate integration method of thick functional components in fibre-reinforced plastics. Smart Materials and Structures. 01/2016 (accepted for publication).

[2] Kostka, P.; Holeczek, K.; Hufenbach, W.: A new methodology for the determination of material damping distribution based on tuning the interference of solid waves. Engineering Structures, 83 (2015), pp. 1-6.

[3] Holeczek, K.; Kostka, P.; Modler, N.: Dry Friction Contribution to Damage-Caused Increase of Damping in Fiber-Reinforced Polymer-Based Composites. Advanced Engineering Materials, 16 (2014) 10, pp. 1284-1292.

[4] Kostka, P.; Höhne, R.; Holeczek, K.; Krahl, M.; Hufenbach, W.: Multidisziplinäre Entwicklung eines robotergeführten Schwingungskompensators. Konstruktion (2015) 07, pp. 86-90.

[5] Holeczek, K.; Dannemann, M.; Modler, N.: Auslegung reflexionsfreier Dämpfungsmaßnahmen für mechanische Festkörperwellen., in: VDI Wissensforum GmbH (ed.): VDI-Berichte 2261, VDI Verlag GmbH, Düsseldorf, ISBN 978-3-18-092261-4, pp. 155-170, 2015.

[6] Kostka, P.; Holeczek, K.; Filippatos, A.; Langkamp, A.; & Hufenbach, W.: In situ integrity assessment of a smart structure based on the local material damping. Journal of Intelligent Material Systems and Structures, 1045389X12462650, 2012.

[7] Zhakov, A.; Schmidt, Th.; Dannemann, M.; Modler, N.: Einsatz faser- bzw. textilverstärkter Verbundwerkstoffe zur Schwingungsdämpfung bei Hubmasten von Regalbediengeräten. 11th WGTL Colloquium, 30.09.01.10.2015, Duisburg.

[8] Brockerhoff, P.; Burkhardt, Y.; Ehlgen, T.; Lucas, P.: Electrical Drivetrain without Rare Earth Magnets and Integrated Inverter with Inherent Redundancy; 4th International Electric Drives Production Conference and Exhibition 2014, ISBN: 978-1-4799-1102-8, 2013.

[9] Burkhardt, Y.; Spagnolo, A.; Lucas, P.; Zavesky, M.; Brockerhoff, P.: Design and analysis of a highly integrated 9-phase drivetrain for EV applications, International Conference on Electrical Machines (ICEM), IEEE DOI: 9781-4799-4775-1/14, 2014.

[10] Prengel, S.; Helwig, M.; Modler, N.: Lightweight coil for efficient wireless power transfer: Optimization of weight and efficiency for WPT coils, 10.1109/WPT.2014.6839603, 2014.

[11] Täger, O.; Dannemann, M.; Hufenbach, W.: Analytical study of the structural dynamics and sound radiation of anisotropic multilayered fibre-reinforced composites. Journal of Sound and Vibration (2015), Vol. 342, pp. 57-74.

[12] Hufenbach, W.; Modler, N.; Winkler, A.: Sensitivity analysis for the manufacturing of thermoplastic e-preforms for active textile reinforced thermoplastic composites. Procedia Materials Science 2 (2013), p. 1-9.

[13] Hufenbach, W.; Gude, M.; Modler, N.; Heber, T.; Winkler, A.; Weber, T.: Process chain modelling and analysis for the high volume production of thermoplastic composites with embedded piezoceramic modules. Smart Materials Research (2013), article ID 201631, p. 1-13.

[14] Hufenbach, W.; Modler, N.; Winkler, A.; Ilg, J.; Rupitsch, S.J.: Fibre-reinforced composite structures based on thermoplastic matrices with embedded piezoceramic modules. Smart Materials and Structures 23 (2014) 2, 025011.

[15] Winkler, A.; N. Modler: Online poling of thermoplastic-compatible piezoceramic modules during the manufac­ turing process of active fibre-reinforced composites. Proceedings of the 20th Symposium on Composites (Vienna, 30.06.-02.07.2015), p. 787-794 [16] Winkler, A.; Marschner, U.; Starke, E.; Modler, N.; Fischer, W.-J.; Hufenbach, W.: Linear two-port model of an active thermoplastic composite structure. Proceedings of the ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems - SMASIS2013, Snowbird, Utah, USA, 16-18 September 2013, paper no. 3310. ISBN 978-0-7918-5603-1.

[17] Holeczek, K.; Starke, E.; Winkler, A.; Dannemann, M.; Modler, N.: Numerical and experimental characterisation of fibre-reinforced thermoplastic composite structures with embedded piezoelectric sensor-actuator-arrays for ultrasonic applications. Appl.Sci. 2016 6(3), 55 doi:103390/app6030055.

Institute of Lightweight Engineering and Polymer Technology

�� Novel materials and processes –

Special solutions to special challenges ��

Thomas Behnisch, Daniel Weck, Michel Wolf, Christian Vogel, Daniel S. Wolz, Alexander Rohkamm, Johanna Maier, Andreas Borowski, Eike Dohmen

Modern lightweight engineering solutions go far beyond material substitution alone. The ILK pursues a philosophy of “lightweight engineering using multi-ma­ te­­­rial design”, with the aim of achieving the highest possible level of func­tionality by exploiting each material’s characteristic properties in a targeted way. Novel combinations of materials suitable for function-integrative, adaptive structures can only be identified and refined with the aid of intelligent processes and technologies. The Expert Group “Special Materials and Special Processes” therefore defines its role as that of an engine for innovation, and in particular a developer of solutions that meet the demands placed on the integrated lightweight structures of the future. Novel materials and processes pave the way for enhanced lightweight structures characterized by a high level of resource and cost efficiency.

Special materials, special processes Our objectives Special solutions are the foundation for the innovations of tomorrow. With this in mind, the Expert Group on SPECIAL MATERIALS AND SPECIAL PROCESSES conducts the targeted development and refinement of novel hybrid manufacturing processes and highly loadable smart materials to establish its vision of “Gene­­­­ rative multi-material lightweight engineering” as one of the leading international manufactu­ ring technologies for multi-layered composite structures with load-specific 3D fibre reinforce­ ment. Figure 1 shows our ima­gination including the fundamentals of generative multi-material lightweight engineering and in Figure 2 it is set an example of a topology optimized, additively manufactured lightweight bicycle pedal. In par­ ticular, we drive innovation in the field of light­ weight engineering within the framework of projects carried out in cooperation with other expert groups within the ILK as well as mem­ bers of the research network Dresden Concept.

Our partners in the industrial and research sec­ tors therefore benefit from outstanding interdis­

Figure 1: Our understanding of the funda­ mentals of generative multi-material lightweight engineering.

Figure 2: Lightweight bicycle pedal with opti­ mized topology manufactured addi­ tively with the aid of the selective layer melting technique (SLM).

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Figure 3: Top: Metal matrix composite (MMC) consisting of carbon fibre reinforced magnesium. Bottom: Composite con­ sisting of magnesium, epoxy resin and continuous fibre reinforcement.

ciplinary expertise as well as a comprehensive understanding of material properties and be­ haviour in a variety of systems.

The point at which the potential offered by conventional materials, methods and tech­ niques has been exhausted is the point at which the work of the Expert Group on SPECIAL MATERIALS and special processes starts. Our objective is to intelligently combine favourable material properties and streamlined processes in order to develop tried-and-tested, cost-effective lightweight engineering solu­ tions in accordance with our customers’ re­ quirements. The coupling of highly customi­ zable, additive techniques with high-perfor­ mance fibre-reinforced materials, adaptable bionic structures, metallic materials with pre­ dictable failure behaviour,thermally resistant ceramics and tailored carbon fibres makes it possible to tap into unimagined potential and develop component and system concepts for an increasingly diverse range of applications.

This conscious fusion of technologies and ma­ terial properties is the core strength held by the Expert Group on Special materials and spe­ cial processes, and could be the key to helping your business stand out from the competition.

Fibre reinforced Metal Matrix Composites (MMC) The specific characteristics of light metals such as aluminium and magnesium make them a vital element of almost every application in the automotive and aerospace sectors. They are therefore synonymous with lightweight engi­

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neering. As a result of the increasing demands placed on structural components in terms of their mechanical and physical properties, these conventional materials have nevertheless be­ gun to reach the limits of their potential on a more and more frequent basis. It is against this backdrop that the Expert Group on Special Materials and Special Processes has already been conducting research into metal matrix composites [MMCs] for over 15 years in order to cater to the undiminished demand for integ­ rated lightweight engineering solutions based on light metals [MMC-0]. In view of the enor­ mous potential offered by MMCs where highly loadable lightweight structures are concerned, our scientists focus on light metals reinforced with either metal wires [MMC-9] or fibres. In the latter case, the use of preforms consisting of continuous reinforcing fibres facilitates the achievement of outstanding mechanical pro­ perties when compared with unreinforced light metals. The resultant composites also exhibit greater thermal stability than fibre-reinforced polymers [MMC-1, MMC-2].

Manufacturing and processing The extent to which reinforcing fibres can be wetted with molten metal plays a significant role in the manufacturing of MMCs. Scientists at the ILK use a gas pressure infiltration pro­ cess for this purpose, with the transfer of the gained insights to commercially viable moul­ ding applications defined as another of the institute’s core research and development objectives. The interface between fibre and matrix is the deciding factor in the achieve­ ment of optimum strength and stiffness pro­ perties, and the Expert Group on Special Ma­ terials and Special Processes therefore also conducts research into the targeted functio­ nalization of the fibre surface. Its work in this area draws not only on longstanding expe­ rience gained within the framework of research and development projects, but also on coope­ ration with regional and international partners [MMC-3, MMC-4, MMC-5].

The availability of interface concepts suitable for the joining of materials to other structural components is a prerequisite for the resourceand cost-efficient use of MMCs within light­ weight, multi-material structures. To give an example, the successful development of a load-conform hybridization concept featuring a cross-interface fibre pattern which facilitates the exploitation of the beneficial characteris­

Institute of Lightweight Engineering and Polymer Technology

tics of both fibre and matrix now enables the joining of light metals with continuous fibre reinforcement to fibre-reinforced composites with plastic matrices (Figure 3).

The local reinforcement of light metal struc­ tures with the aid of fibre-reinforced metal inserts – for example by means of recasting or friction stir welding – is also a key area of research focus, and combines material-spe­ cific benefits with commercial advantages [MMC-7]. The embedding of fibre-optic sen­ sors into MMCs represents another applica­ tion-oriented example, and will one day enable the monitoring of components made of fibrereinforced light metal structures [MMC-8].

Fibre-reinforced Ceramic Matrix Composites (CMC) Fibre-reinforced CMCs offer a particularly broad range of potential benefits within the framework of lightweight applications, not least because of their temperature-resistant, consistently high, mass-specific stiffness and strength. The combination of a ceramic matrix with a function- and load-specific fibre rein­ forcement architecture results in directional composite characteristics which can be adjus­ ted as required and adapted to specific appli­ cations. Micromechanical effects and energy dissipation at the interface between fibre and matrix have a predictable influence on the spread of cracks caused by loading, thus en­ abling the engineering of damage-tolerant material behaviour. Fibre-reinforced CMCs are therefore especially suitable for the design

of complexly loaded structural components for high-temperature applications.

High-temperature lightweight engineering plays an increasingly important role in modern mechanical engineering, whether within the context of aerospace applications or the engi­ neering and manufacturing of vehicles, machi­ nes and plants. With this in mind, it is impor­ tant to note that innovative materials are in­ dispensable to the exploitation of new areas of application in the field of high-temperature lightweight engineering [CMC-1 – CMC-7].

It is for this reason that the Expert Group on Special Materials and Special Processes has made ceramic matrix composites (CMCs) a key area of research and development focus.

A Laval nozzle for the acceleration of hot gas as part of industrial processes is one example of the components developed and success­ fully tested in practical scenarios (Figure 4).

Fibre manufacturing & functionalization One of the fundamental prerequisites for the manufacturing of high-performance, fibrereinforced components is the coating of the reinforcing fibres (e.g. with pyrolytic carbon) that is tailored to the matrix system. This functionalization of the surface of the fibre is achieved with the aid of atmospheric pressure chemical vapour deposition (APCVD) using the ILK’s in-house fibre coating system.

Deposition occurs within a cold wall reactor, and sees the layer constituents continuously deposited out of an inert gas atmosphere en­ riched with the elementary carrier bonds and

Figure 4 (left): Shock-resistant, high-temperature de Laval nozzle made of a fibre-reinforced ceramic matrix composite (CMC); designed for use in streams of hot gas with a flow speed of up to Mach 2.

Figure 5 (right): Turbostratic graphite coating (thick­ ness: 250 nm) applied to a carbon-fibre filament using the CVD technique; image taken using a scanning electron microscope (SEM).

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required in order to achieve this, and maintains strong contacts with a comprehensive network of fibre and preform manufacturers able to supply us with tailored semi-finished textiles for research and development projects.

Besides matrix adapted coatings, the tailoring of carbon fibres (CF) for their specific appli­ cation is a key aspect of the Experts Group Special Material and Special Processes. Until now, carbon fibres are used by their available properties, but don´t meet the demands whe­ ther for nowadays or future applications in outstanding lightweight solutions.

Figure 6 (up): Optical inspection of filament quality during manufacture of a tailored carbon fibre grade.

Figure 7 (down): Samples of plastic components with continuous fibre reinforcement manu­ factured by means of fused layer modelling (FLM).

onto the surface of the substrate (Figure 5) [FFKT-1, FFKT-2]. The layer deposited acts as a diffusion barrier between the reinforcing fibres and the matrix during the manufacturing of both MMCs and CMCs. In the case of CMCs in particular, this functionalization at the inter­ face between fibre and matrix also leads to a clear reduction in adhesion, which in turn results in damage-tolerant, quasi-ductile frac­ ture behaviour [FFKT-3].

For all fibre-reinforced materials, the adaptation of the fibre functionalization process to both the fibre and the matrix is of vital importance to fully exploit the potentials of the individual materials.

The Expert Group on Special Materials and Special Processes possesses the expertise

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The need of fulfilling the requirements for future developments like bionic structures or carbon fibre reinforced concrete will further­ more increase the request for tailored CF. To achieve this, the process-structure-propertyrelationship within the CF manufacturing pro­ cess are analysed across all relevant length size scales [CF-1, CF-2]. For this purpose, a cutting-edge manufacturing technology in the carbon fibre research line is used in­ cluding all process steps of the converting process from polymeric precursor fibre spin­ ning to the pyrolised CF. The specialists of the ILK weigh in their Know-How to expand the knowledge and technology reaching novel carbon fibre structures by doing research with a unique stabilisation and carbonisation re­ search line (Figure 6). The stabilisation pro­ cess is hereby the first step of the thermome­ chanical conversion of the polymeric precur­ sor fibre to a CF. The fibres pass during the stabilisation different temperature zones and in order to spe­cifically influence the inner fibre structure the fibre can be drawn depending on the tempe­rature zone. In the subsequent carbo­nisation step within two carbonisation fur­naces the fibre structure is continuously modified for the CF structure to be manu­ factured. Finally, matrix-adapted sizings are applied to the fibres. Therefore carbon fibres with custom-fitted properties for different applications can be manufactured in the car­ bon fibre research line on a laboratory scale.

The hereby achieved fundamental scientific findings can be directly transferred into in­ dustrial applications together with industrial partners.

Furthermore the resultant carbon fibre struc­ ture and properties will be influenced first-time by the spinning processes. Therefore, the com­­

Institute of Lightweight Engineering and Polymer Technology

prehensive approach analysing the processstructure-property-relations overall process steps is carried out within the Research Center Carbon Fibers Saxony (RCCF), a partnership of the ILK and the Institute of Textile Machinery and High Performance Material Technology of the TU Dresden.

Generative multi-material lightweight engineering The Innovation LAB for additive manufacturing is used for research into the tar­ geted application of high-performance mate­ rials and the synergetic combination thereof to create multi-material lightweight structures characterized by resource and cost efficiency.

Particular emphasis is placed on the use of additive manufacturing techniques. Participa­ ting scientists promote and refine the ILK’s philosophy of Generative Multi-Material lightweight engineering as a means of linking bionic, multi-material reinforcement concepts with tailored fibre-reinforced com­ posite technologies.

Innovative systems, series-oriented process chains and reliable process simulations are being used to turn additive manufacturing into a series-ready processing technique for highperformance multi-material composites. In par­ ticular, we aim to combine the production of fibre-reinforced composites with conventional additive manufacturing techniques to form a continuous overall process. The breaking down of highly individualized, complex components into characteristic layers enables them to be manufactured on an automated, highly repro­ ducible basis. Additive manufacturing tech­ niques offer a huge potential in the field of lightweight engineering due to their compati­ bility with components of almost any shape.

A large number of the research activities en­ gaged in by the Expert Group on Special Ma­­ terials and Special Processes in this area focus on the use of fused deposition modelling (FDM) [GEFE-1, GEFE-2, GEFE-3].

Research activities Until now, the use of unreinforced thermo­ plastics has placed significant restrictions on the mechanical properties exhibited by compo­ nents manufactured using additive techniques.

In order to facilitate the additive ma­nufacturing of functionalized structural components in the future, scientists working in the Innovation

LAB for Generative manufacturing have de­veloped a printhead for the 3D printing of thermoplastic materials with continuous fibre reinforcement. The novel printhead is adaptable to both the specific properties of and the demands placed on fibre-reinforced com­ posites. What is more, it is the first to enable the processing of commercial hybrid yarns as part of 3D printing processes, thus paving the way for the manufacturing of three-dimensio­ nal bodies with a high fibre volume ratio.

Figure 8: Research into the parameters influen­ cing the simultaneous processing of multiple thermoplastic tapes with continuous fibre reinforcement.

The ILK expands and enhances the Innovation Lab for Generative Manufacturing on a conti­ nuous basis and engages in joint research into additive manufacturing techniques in coopera­ tion with the Singapore Center for 3D Printing.

A new, multi-functional preforming system is set to enable scientists to manufacture com­ plex 3D structures from thermoplastics with continuous fibre reinforcement (Figure 7). The system facilitates the rapid, simultaneous lay­ ing of multiple fibre-reinforced, thermoplastic tapes. Each tape is laid onto the forming struc­ ture in a way which ensures precise adherence to both application-specific loading and the shape of the target component (Figure 8). One goal pursued in this area is the one-step, was­

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Institute of Lightweight Engineering and Polymer Technology

Figure 9: Inspection of an omega tube manu­factured using the resin powder moulding technique (RPM).

te-free manu­facturing of an entire side panel for a car – including all necessary connection points for elements such as seatbelts, hinges and windows as well as functional components such as loudspeakers and lighting [GEFE-4].

Magnetic hybrid materials (MHMs)

contact

Dipl.-Wi.-Ing. Thomas Behnisch Head of Special materials and special processes Tel.: +49 (0)351 463 42 503 thomas.behnisch@ tu-dresden.de

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Magneto- and electrorheological materials have yet to find widespread technological application despite being a well-established topic of scientific research. One constraint is the lack of suitable design methods and con­ cepts for the efficient, beneficial integration of these active components into structures. As a result, almost none of the potential offered by the combination of magnetorheological fluids (MRFs) or magnetorheological elastomer (MREs) with fibre-reinforced composites or foams to create so-called MAGNETIC HYBRID MATERIALS (MHMs) has been exploited to date. The properties exhibited by these smart composites – for example their damping be­ haviour – can be adjusted on an infinitely varia­ ble, touch-free basis using a magnetic or elec­ trical field. The almost instantaneous change triggered in the material makes MHMs suit­ able for a range of highly dynamic system control applications [MHM-1, MHM-2].

Powder moulding processes for largescale series production (A.S.SET) Industrial companies are dependent on innova­ tion as a means of meeting the increasing de­ mands placed on them by both customers and

legislators. Researchers at the ILK therefore use their experience to provide you with targe­ ted support as you develop new, streamlined, more cost-effective processing technologies and integrate lightweight materials into your components and systems. Two tailored manu­ facturing techniques – Resin Powder Moulding (RPM) und Thermoset Sheet Forming (TSF) – have already been developed in cooperation with LZS GmbH for the A.S.SET powder tech­ nology developed by the Polish firm New Era Materials [ASSET-1, ASSET-2]. These two tech­nologies enable the production of light­ weight, fibre-reinforced preforms (Figure 9) in medium and large batches, which in turn facili­ tates the efficient manufacturing of high-qua­ lity components at reduced production costs.

The resin used is based on epoxy but comes in the form of a powder which can be repea­ tedly melted and moulded. The matrix material is combinable with all known reinforcement materials and therefore predestined for the production of multi-material components.

The resin powder processing technologies com­ bine the production efficiency of ther­moplastic materials with the superior mechanical and ther­ mal properties of thermosetting materials. They represent not only a mini-revolution in the field of additive composite manufac­turing, but also an alternative to expensive series production techniques such as high-pressure resin trans­­fer moulding (HP-RTM). Research in this area currently focuses on the use of A.S.SET resin powder in combina­tion with commercially viable 3D printing techniques such as selective laser melting (SLM).

Fazit The researchers who make up the ILK’s Expert Group on Special Materials and Special Pro­ cesses are characterized by extensive expertise in the field of material behaviour, outstanding creativity and a highly interdiscipli­nary approach.

Close cooperation with other expert groups within the ILK, members of the Dresden Con­ cept network and international partners en­ sures that every single detail is properly taken into account – even when tackling highly com­ plex development projects. Whether you wish to develop multi-material lightweight compo­ nents and tailored system concepts or carry out innovative, application-oriented research, the Ex­ pert Group represents an ideal strategic partner.

Institute of Lightweight Engineering and Polymer Technology

Literature [MMC-0] Hufenbach, W.; Andrich, M., Langkamp, A., Czulak, A.: Precision moulds of graphite for fabrication of carbon fibre reinforced magne­ sium. Proceedings of the 12th International Scientific Conferences AMME’2003, p. 381-384. 2003.

[MMC-1] Hufenbach, W.; Gude, M.; Czulak, A.; Gruhl, A.; Wolf, M.: Mikrostrukturanalyse und werkstoffmechanische Charakterisierung von Kohlenstofffaserverstärkten MMC. Presented at the “46. DGM Tagung Metallographie”. Rostock, 2012.

[MMC-2] Hufenbach, W.; Gude, M.; Czulak, A.; Gruhl, A.; Wolf, M.; Malczyk, P.: Microstructure analysis and characterization of material proper­ ties of CFR light metal composites manufactured via GPI-method.

Proceedings of the Archives of Civil and Mechanical Engineering.

Wroclaw, 2012.

[MMC-3] Krug, M.; Abidin, A.Z.; Höhn, M.; Endler, I.; Sobczak, N.; Czulak, A.; Malczyk, P.; Michaelis, A.: Al2O3 protective coatings on carbon fiber-based 3D-textile preforms prepared by ALD for application in metallic composite materials. 13th AUTEX World Textile Conference Dresden, May 22nd to 24th 2013.

[MMC-4] Abidin, A.Z.; Kozera, R.; Höhn, M.; Endler, I.; Knaut, M.; Boczkowska, A.; Czulak, A.; Malczyk, P.; Sobczak, N.; Michaelis, A.: Preparation and characterization of CVD-TiN-coated carbon fibers for applications in metal matrix composites. Thin Solid Films. June 16th 2015.

[MMC-5] Gude, M.; Boczkowska, A.: Textile reinforced carbon fibre/alumi­ nium matrix composites for lightweight applications. Foundry Research Intitute. ISBN 978-83-88770-97-5. 2014.

[MMC-7] Gude, M.; Wolf, M.; Czulak, A.; Mühle, U.; Lewandowska, M.; Zschech, E.: Friction Stir Welding and Inlay Manufacturing: Innovative Methods for Joining Novel Material Combinations for Lightweight Structures. 19th International Dresden Lightweight Engineering Symposium. Dresden, 2015.

[MMC-8] Malczyk, P.; Gude, M.; Kaleta, J.; Szczurek, A.: Multifunctional fibrereinforced metal matrix composites with integrated optical fibre sensors. 20th International Conference on Composite Materials.

Copenhagen, July 19th-24th 2015.

[MMC-9] Hufenbach, W.; Ullrich, H.; Gude, M.; Czulak, A.; Malczyk, P.; Geske, V.: Manufacture studies and impact behaviour of light metal matrix composites reinforced by steel wires. Archives of Civil and Mechanical Engineering, Volume 12, Issue 3, p. 265-272. ISSN 1644-9665. September 2012.

[CMC-1] BNP-Media: GE Tests Rotating Ceramic Matrix Composite Material for Next-Gen Combat Engine. http://www.ceramicindustry.com/ articles/94584-ge-tests-rotating-ceramic-matrix-composite-materialfor-next-gencombat-engine, 2015. [online; retrieved on December 21st 2015] [CMC-2] Chrost, W.; Bathe, C.; Wiebus, R.; Leyens, M.; Vogtmeier, G.; Wirth, T.; Dongre, C.; Bachmann, P.; Weiß, R.; Henrich, M.; Feltin, D.; Preussier, S.; Hufenbach, W.; Richter, H.; Weck, D.; Pintsuk, G.: Entwicklung kohlenstoffbasierter ultraschnell rotierender Anoden für Hochleistungsröntgenröhren. Proceedings of the “19. Sympo­ sium Verbundwerkstoffe und Werkstoffverbunde DGM”, p. 212217. Karlsruhe, 2013.

[CMC-3] Hufenbach, W.; Behnisch, T.; Richter, H.; Langkamp, A.; Janschek, P.; Bauer-Partenheimer, K.; Turley, F.: Development of hybrid CMC forming dies for high temperature precision forging of titanium alu­ minide based alloys. High Temperature Ceramic Materials and Composites AVISO, p. 531-536. Berlin, 2010.

[CMC-4] Lee, R.: GE sees ceramics improving jet engine performance. http://www.ctpost.com/news/article/GE-sees-ceramics-improving-

jet-engineperformance-4544281.php, 2013. [online; retrieved on December 21st 2015] [CMC-5] Neubrand, A.: Hochtemperaturwerkstoffe mit attraktivem Eigenschaftsprofil. Konstruktion – Zeitschrift für Produktentwicklung und Ingenieur-Werkstoffe 7/8, p. IW8-IW10. 2014.

[CMC-6] Tamura, T.; Nakamura, T.; Takahashi, K.; Araki, T.; Natsumura, T.: Research of CMC Application to Turbine Components. IHI Engineering Review 38 No.2, p. 58-62. 2005.

[CMC-7] Trimble, S.: GE unveils newest fuel-saving material for aircraft en­gines. https://www.flightglobal.com/news/articles/geunveils-newest-fuelsaving-material-for-aircraft-391206/, 2013. [online; retrieved on December 21st 2015] [FFKT-1] Than, E.: Herstellung und Anwendung beschichteter Kohlenstoff- und Siliciumcarbidfasern. Technische Textilien 42 [3], p. 185-187. 1999.

[FFKT-2] Than, E.: Beschichtung keramischer Fasern mit CVD-Verfahren – Stand der Technik und Wirtschaftlichkeit. Keram. Z. 54 [1], p. 12-18.

2002.

[FFKT-3] Evans, A.G.; Zok, F.W.: The physics and mechanics of fibre-rein­ forced brittle matrix composites. In: Journal of Materials Science 29, p. 3857-3896. 1994.

[CF-1] H. Jäger, H.; Cherif, C.; Kirsten, M.; Behnisch, T.; Wolz, D. S., Böhm, R.; Gude, M.: Influence of processing parameters on the properties of carbon fibres –the review. Material Science and Engineering Vol. 11, 2016 [CF-2] Jäger, H.; Behnisch, T.; Wolz, D. S.; Gude, M.; Böhm, R.: Effect of material properties and process parameters on the structure and properties of carbon fibres. Advanced Textile Fibres and Materials, Autex Journal, 2016 [GEFE-1] Modler, N.; Kaufhold, J.; Vogel, C.; Roitzsch, C.: Fused Deposition Modelling of Short Fibre Reinforced Structures. Lecture at EUROMAT, 20.-24.09.2015. Warsaw, 2015.

[GEFE-2] Modler, N.; Vogel, C.; Dohmen, E.; Kaufhold, J.; Albert, M.: Additive Manufacturing of Medical Implant Structures via FLM. Lecture at EUROMAT 20.-24.09.2015. Warsaw, 2015.

[GEFE-3] Modler, N.; Vogel, C.; Dohmen, E.; Kaufhold, J.; Breite, C.: Verarbeitung von PEEK im Fused-Deposition-Modeling Verfahren.

Werkstoffwoche 2015. Dresden, 2015.

[GEFE-4] Vogel, C.; Zichner, M.: SuperTooler – Integrierte FDM/FräsHybridfertigungszelle zur effizienten Herstellung großformatiger Formwerkzeuge. FOREL Colloquium. Dresden, 2015.

[MHM-1] Dohmen, E.; Boisly, M.; Borin, D.; Kästner, M.; Ulbricht, V.; Gude, M.; Hufenbach, W.; Heinrich, G.; Odenbach, S.: Advancing Towards PU-Based MR Composites. Advanced Engineering Materials. 2014.

[MHM-2] Kozlowska, J.; Boczkowska, A.; Czulak, A.; Przybyszewski, B.; Holeczek, K.; Stanik, R.; Gude, M.: Novel MRE/CFRP sandwich structures for adaptive vibration control. Smart Materials and Structures. 2016.

[ASSET-1] Czulak, A.; Geller, S.; Hufenbach, W.; Jarkowski, M.; Lepper, M.; Pilawka, R.; Renner, O.: 1-component system, products derived from same and method for the production of fibre compound semifinished products and components with the 1-component system.

EP2851182, New Era Materials. 2015.

[ASSET-2] Jorkowski, M.; Urban-Pilawka, E.: Composition of reactive epoxy resins and method for producing products preimpregnated with the composition of reactive epoxy resins. PL405405-A1, New Era Materials. 2015.

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�� Imprint �� in focus: Germany´s Elite-Institutes Excellence in Lightweight Design at TU Dresden Published by: Institut für wissenschaftliche Veröffentlichungen (IWV)

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