Materials

MATERIALS All projects involve the use of materials. One of the best ways to collect research on materials is to carry out tests or experiments that will reflect their use in your project.

You could devise tests for ‘waterproof’ properties - ‘impact resistance’ - ‘flexibility’ ‘rigidity’ - and many more.

The picture shows the wide range of facts and issues relating to materials research that need to be considered when designing a product. It clearly shows that you have an understanding of facts and issues relating to materials.

MATERIALS PROPERTIES

Different types of forces

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Technology UNIT Materials: wood

When studying materials and especially when selecting materials for a project / design, it is important to understand key properties.

MECHANICAL PROPERTIES strength : The ability of a material to stand up to forces being applied without it bending, breaking, shattering or deforming in any way. elasticity: The ability of a material to absorb force and flex in different directions, returning to its original position. plasticity: The ability of a material to be change in shape permanently. ductility: The ability of a material to change shape (deform) usually by stretching along its length. tensile strength: The ability of a material to stretch without breaking or snapping. malleability: The ability of a material to be reshaped in all directions without cracking toughness: A characteristic of a material that does not break or shatter when receiving a blow or under a sudden shock. hardness: The ability of a material to resist scratching, wear and tear and indentation. conductivity: The ability of a material to conduct electricity.

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Technology UNIT Materials: wood

WOODS

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WOOD (TIMBER)

LA MADERA

Parts of the tree

Partes del รกrbol

Parts of the trunk of a tree

Partes del tronco

Technology UNIT Materials: wood

Wood properties Low density Electrical and thermal insulator Acoustic conductor Ductile and malleable Resistant to mechanical stress Flammable Renewable, recyclable and biodegradable Deformed by moisture

Propiedades de la madera Baja densidad Aislante térmico y eléctrico Conductor acústico Dúctil y maleable Resistente a esfuerzos Inflamable Renovable, reciclable y biodegradable Se deforma por la humedad

WOOD PROCESSING Vocabulary: English LOG LUMBER HARVEST TO FELL A TREE LIMBING Process:

Spanish Leño, tronco tablones, tablas cosecha Talar un árbol

English DEBARKING PLANNING SAWMILL BUCKING

Spanish descortezar cepillado serrería tronzado

desramar

KILN

horno

FELLIN G

LIMBING

BUCKIN G

DRYING

TRANSPORT

PLANIN G

DEBARKING

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Distribución SHIPPING

Explanation: 1.

2.

3.

4.

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After trees are selected for harvest, the fisrt step is felling the trees.

Branches are cut off the trunk. This is known as limbing.

Logs are taken by logging truck, or rail to the sawmill.

Debarking removes bark from the logs.

Technology UNIT Materials: wood

5. A sawyer uses a saw to buck the log into cants (unfinished logs to be further processed) and flitches (unfinished planks).

6. Drying removes naturally occurring moisture from the lumber. This can be done with kilns or air-dried.

7. Planing smooths the surface of the lumber leaving a uniform width and thickness.

8. Shipping transports the finished lumber to market.

PAPER MAKING

FABRICACIĂ“N DEL PAPEL

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Technology UNIT Materials: wood

SOME TIMBER TREES

Pine tree (pino) Oak (roble) Cherry-tree (cerezo)

Fir (abeto) Mahogany (caoba)

Beech (haya)

Holm oak (encina)

Cedar (cedro)

Elm (olmo)

Birch (abedul) Poplar (chopo)

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Almond tree (almendro)

Technology UNIT Materials: wood

CLASSIFICATION OF COMMERCIAL WOODS

NATURAL WOODS Woods are classified into two main groups, softwoods and hardwoods. Trees are either coniferous (bears cones and have needle shaped leaves that stay green all year round) or deciduous (has flat leaves that fall in autumn). The timber that comes from the coniferous tree is known as softwood and the timber that comes from deciduous trees is known as hardwood. Although the terms suggest that softwoods are soft and easy to cut and shape and that hardwoods are hard and more difficult to shape this is not the case. For example, balsa wood which is noted for its lightness and softness, is actually classified as a hardwood.

EXAMPLE OF A SOFTWOOD PINE - Is a relatively cheap wood used in the building

trade and for furniture. It is pale in colour, quite easy to cut and shape, and machines relatively well.

EXAMPLES OF A HARDWOODS MAHOGANY - Is quite expensive and is used for good

quality furniture and hardwood windows. It is light brown in colour and more difficult to use compared to pine.

OAK - This is an expensive material and is used in for

making quality, expensive furniture. Steel fittings such as hinges will stain oak so it is important to use brass ones.

TEAK - A hardwood that contains oils which means it is

resistant to decay. This is often used to make garden furniture or for wood block flooring.

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Technology UNIT Materials: wood

MANMADE BOARDS These are boards that are made in factories from materials such as wood chippings or dust.

BLOCKBARD - This is built up with a core of softwood

strips bonded together with adhesive and covered with a sheet of plywood on either side. Used as a building material and for furniture manufacture including fitted kitchens / bedrooms.

CHIPBOARD - This is made up of small chips of wood

bonded together with resin and formed into sheets by compression. It is not as strong as plywood and block board but it is not expensive. Chipboard is often covered with a plastic laminate or wood veneer and used in furniture.

HARDBOARD - This is made from wood fibres that

have been pulped. The pulp is put under pressure until the fibres bond to produce a tough board that is smooth on one side and rough on the other. It is not as strong as the other boards.

MEDIUM DENSITY FIBRE BOARD (MDF) - A

quality board, relatively cheap. This board is composed of fine wood dust and resin pressed into a board. This material can be worked, shaped and machined easily.

Paint can be applied to it without the need for an undercoat or primer. Used in the building and furniture trades.

PLYWOOD - This is made from veneers (plies) of timber with each grain layer being at right angles to each other and bonded together by resin and pressure.

A number of grades are available, designed to suit a variety of situations.

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