Carbon Fiber Present

Application of Carbon Fiber for Large Structural Components

Application of Carbon Fiber for Large Structural Components Primary Goals •Allow thin panel fabrication with liquid molding •Provide increased stiffness to offset loss of thickness •Develop full structural capability using multiple fibers •Achieve Class A (truck) surface quality

Other Goals •Provide durability necessary to prevent reverse impact damage •Process cycle times better than open molding and comparable to liquid molding into preforms 1

Accomplishments Class “A” finishes Improved impact Thin walled RTM 2.5 mm Optimized filler loads for class “A” Mechanical Properties tests on various panel types New tooling systems for improved thermodynamic control New materials that provided very low resistance to flow and robust processing 3

Where Does 20% Weight Savings Come From?

Typical hood and fairing weights of 500-1000 lbs Weight savings of up to 50% Comparable material costs Lower tooling cost compared to SMC Alternative manufacturing methods to SMC or wet molding Improved impact properties 4

Fiber Selection Stiffness Offset z z

z

z

Required carbon fiber to address h3 stiffness decrease Materials only needed in specific areas and orientations Carbon necessary to meet local flat panel stiffness criteria Shape and form determine stiffness as much as panel t

5

Resin System Selection Key Criteria z z z z

Excellent neat resin impact properties Capability to bond to multiple fiber systems Capability to liquid mold structures (not SRIM) Rapid process cycle times

Secondary criteria z z

Low cost Compatible with fillers

Resin Type Epoxies Vinylesters Polyesters Urethanes Blended PU/PE

Impact

Adhesion

Liquid Molding

Cycle time

+ +/++ ++

+ ? + +

+/+ + ? (+)

+ + + +

Cost/Fillers

++ +

/ / / / /

+ ++ + + 6

Hybrid Fiber Interactions Processing z z z z

Injection/compression molding Compatible binders required to hold materials in place Molding pressures to 65 psi Cycle times limited by flow as much as resin kinetics, 12 minutes achieved

co

z

ca rb on

z

High-fiber densities achieved Excellent adhesion to glass and carbon phases Fiber loft factors were key determinant in molding gla ss

z

Su rf at ace

Panel Quality

Fiber 48.12% Matrix 49.93% Porosity 1.88% 7

Mechanical Performance Results Impact Energy z z z

Key determinant of panel durability (in-plant damage of thin panels) Excellent performance as compared to SMC (automotive grade hiimpact) and glass/preform technology No degradation seen with carbon fiber systems

Fatigue Performance z z

Minimal loss of strength over test Samples ran over 7 million cycles with under 5% loss 4-point Flexural Fatigue Testing 235 Mpa Flexural Strength

Impact Energy - first crack (J)

100%

Percent of Flexural Strength

90%

3 2.5 2 1.5

80% 70% Filled System

60%

Unfilled 20041216_1_1 200412161_2_3

50% Filled System 40% Unfilled System

30% 20% 10%

1

E+ 06 00

50

E+ 06 5.

00

E+ 06 4.

50

E+ 06 4.

3.

00

E+ 06

E+ 06 3.

50 2.

2.

00

E+ 06

E+ 06

E+ 06

50 1.

00 1.

00 5.

0.

00

0.5

E+ 05

E+ 00

0%

Cycles

0 n bo ar /C id br Hy ss la /g id br rm Hy fo re /P id qu Li

C SM

Typical Fatigue Curves Over 80% loss with glass

Dramatic improvement in fatigue of hybrid system 8

Mechanical Performance Results - Cont ’d Cont’d Design Capability z z z

Developed methods to design and model strength/stiffness of components Excellent correlation with test panels Near full property translation for carbon and glass fractions with blended hybrid resins Flexural Testing on Hybrid System 300

Flexural Stress (MPa)

250

200 20031215-1 150

100

50

0 0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Strain (mm/mm)

Discontinuous Carbon Composite

Discontinuous Carbon Hybrid Composite

Flexural stress results on hybrid composite with blended urethane resin system 9

Lessons Learned Key Developments z z z

Thin walled RTM <2.5mm thickness RTM polyurethane systems Large lightweight RTM tools

10

Conclusions Modeled properties and developed effective designs using discontinuous fibers with blended hybrid resins Excellent adhesion is achieved with various fiber phases Resin systems significantly improve hybrid fiber composites Very rapid cycle times for molding Use of carbon and glass fiber combinations with class A finish Developed and performed process trials with a new tooling system

11