Materials

toc = The Selection of Materials = Designers have an almost endless range of materials to choose from. One of the most important considerations to be made when designing a product is the choice of materials. It is necessary that students understand the different categories of materials, in order to idenftify quickly the most suitable materials for the product. Before investigating individual materials, the following points should be considered: In many cases different materials can be used for the same product, therefore other considerations such as cost and the processing capabilities of materials, and availability are factored into the choice of materials. = Properties of Materials =
 * 1.1 Wood**
 * 1.2 Metals**
 * 1.3 Plastics**
 * **Service** - What does the product need to be able to do?
 * **Properties** - What are the characteristics the material will need to have? Will it need to be strong? Is the weight an issue?
 * **Environment** - What sort of surroundings will the product be used in?
 * **Aesthetics** - What will the product look like? Is it important that it has a particular look, colour or feel?
 * **Mechanical properties** ||
 * Strength || The ability of a material to withstand an applied force ||
 * Hardness || A measure of how easily a material is scratched or indented. Very hard materials such as glass or cast iron are often brittle (they have low impact resistance) ||
 * Toughness || How well the material absorbs impact - the opposite to brittleness ||
 * Stiffness || The ability to resist bending ||
 * Ductility || The ability of a material to be worked. Ductile materials can be formed easily into shapes, e.g. pressing deep shapes into steel such as car body panels. ||
 * Compressive strength || The ability to withstand pushing forces ||
 * Tensile strength || Tha ability to withstand pulling forces ||

= Wood = Woods can be divided into 3 categories: Softwoods and Hardwoods (solid wood) and Manufactured Board (wood product) Working properties, advantages/disadvantages of the following wood and manufactured board used in the manufacture of electronic product cases: It is a softwood, comes from trees that are cone bearing (coniferous) they have needles and are evergreens. It is a fast growing tree (20-30 years to mature) Open grain Pale brown or yellow in colour. Pronounced grain often with knots ||  ||  ||   || Inexpensive. Readily available. Easy to shape. Easy to achieve a good finish. Relatively light wieght for smaller objects. ||  || Pronounced grain. Hard knots, Splits easily. Can warp in humid and wet conditions. || (MDF) ||  || MDF is a type of manufacture board, mid brown in colour. Which is made from wood fibres glued under heat and pressure. MDF contains a substance called urea formaldehyde, which may be released from the material through cutting and sanding. Proper ventilation is required when using it and facemasks are needed when sanding or cutting MDF with machinery. Very large sheets can be manufactured (far greter then natural timber ||  ||  ||   || Inexpensive It is dense, flat, stiff, has no knots and is easily machined. Uniform texture. Easily joined together with glue. Once sealed provides an excellent surface for painting. ||   || Urea formaldehyde may cause irritation to the eyes and lungs. MDF contains glue, the cutting edges of tools will blunt very quickly. When joining with screws/nail may split. Not water resistant - will swell. ||
 * **Physical properties** ||
 * Thermal conductivity || How well a material conducts heat, e.g. aluminium is a very good conductor of heat ||
 * Resistance to corrosion || How slowly the material oxidises - ferrous metals have a low resistance to corrosion ||
 * Electrical conductivity || How well the material conducts electricity - copper is a very good conductor. Materials that do not conduct electricity are called insulators, e.g. plastics ||
 * Optical properties || How easily light passes through the material ||
 * Appearance || Considerations such as aesthetics, colour, brightness and texture ||
 * Joining properties || The ability of the material to be joined to itself or other materials - some woods, e.g. teak, are oily and therefore do not accept adhesives well ||
 * pine
 * medium density fibreboard (MDF)
 * **Material** ||  || **Properties** ||   || **Photo** ||   || **Advantages** ||   || **Disadvantages** ||
 * Pine ||  || A naturally occurring timber.
 * Medium density fibreboard

Glossary - Wood

 * Grain: ** The direction or pattern of the wood fibres found in wood.
 * Softwood: ** Wood from a coniferous tree (evergreen). E.g. Pine, Spruce, Redwood, and Douglas Fir.
 * Hardwood: ** Wood from a deciduous tree. E.g. Oak, Beech, Mahogany, Ash, Teak, Balsa wood, and Elm.
 * Manufactured Board: ** A wood product made by pulping or processing wood particles or pieces. A by product / waste from the timber industry. E.g. Medium Density Fibreboard (MDF) and Plywood.

You need to consider the following points: = = = Plastic = Working properties, advantages/disadvantages of the following plastics used in the manufacture of electronic product cases: also known as High Density Polystyrene (HDP) ||   || Available in a range of thicknesses and a wide range of colours. Thermoplastic - soften when heated and can be shaped when hot. ||  ||  ||   || Very suitable for vacuum forming Good resistance to moisture and impact. Non conductive. Good insulator Lightweight. Low cost. Wide range of colours available. Can be transparent. ||  || Not weather resistant. Becomes brittle due to UV light. Large forms/casing not very strong. || Available in a variety of forms e.g. as sheets, rods, and tubes. Glossy finish. Thermoplastic - soften when heated and can be shaped when hot. Ideal for cutting using laser cutter Shaped using oven and moulds, Bent using line bender ||  ||  ||   || High gloss finish. Available in transparent, textures, and mirrored. Low cost. Can be cut using laser cutter - requires very little finishing. Join using Tensol acrylic cement ||  || Brittle. Heavy. Scratches easily || You need to consider the following points:
 * Extension Task**
 * Natural wood
 * Softwoods and hardwoods
 * Manufactured timbers
 * Laminated boards
 * Particle boards
 * Fibreboards
 * Properties of wood
 * Commercial stock of material
 * Recycling
 * The source of plastic
 * high impact polystyrene (HIPS) also know as high density polystyrene (HDP)
 * acrylic.
 * **Material** ||  || **Properties** ||   || **Photo** ||   || **Advantages** ||   || **Disadvantages** ||
 * High Impact Polystyrene (HIPS)
 * Acrylic ||  || Available in a wide range of colours.
 * Extension Task**
 * Plastics manufacture
 * Thermoplastics
 * Thermosets
 * Elastomers
 * Composites
 * Properties of plastic
 * Commercial stock of material
 * Recycling

= Metal = Working properties, advantages/disadvantages of the following metals used in the manufacture of electronic product cases: and many other preformed profiles. Lightweight. Non-ferrous. Low melting point. Pale silvery colour. ||  ||  ||   || Good strength-to-weight ratio. Aesthetic appeal: polishes well - mirror finish. Can be recycled econimically. Corrosion resistant
 * aluminium
 * brass
 * copper
 * mild steel
 * **Materials** ||  || **Properties** ||   || **Photo** ||   || **Advantages** ||   || **Disadvantages** ||
 * Aluminium ||  || Available in sheets, tubes rods,

Malleable and ductile. Strong and durable. Impenetrable to air, light, and moisture. ||  || Difficult to join. Good conductor of electricity and heat - making it unsuitable for electronic product cases. Expensive raw material. Cheap as recycled material ||
 * Brass ||  || Alloy (mixture of copper & zinc)

Non-ferrous. Available in sheets, wire, tubes rods, and many other preformed profiles.

Malleable and ductile.

Low melting point. Gold. ||  ||  ||   || Corrosion resistant Harder than copper Cheaper than copper Polishes well ||  || Good conductor of electricity and heat - making it unsuitable for electronic product cases. || and ductile.
 * Copper ||  || Non-ferrous, malleable

Available in sheets, wire, tubes rods, and many other preformed profiles.

High corrosion resistance. Low melting point. Copper - red colour, very shiny ||  ||  ||   || Easy to shape. Easily joined. Polishes Well. ||  || Excellent conductor of electricity and heat - making it unsuitable for electronic product cases. Expensive. Tarnishes, effected by air and moisture. || Ferrous
 * Mild Steel ||  || Tough, ductile and malleable.

Available in sheets, wire, tubes rods, and many other preformed profiles.

Dull dark grey colour - discolours easily due to corrsoion ||  ||  ||   || Very strong Easily joined Can be heated to very high temperatures. ||  || Heavy. Poor resistance to corrosion. Cannot be hardened to tempered.

Excellent conductor of electricity and heat - making it unsuitable for electronic product cases. Expensive. || You need to consider the following points: = Task - Materials = Using the link below - complete the tutorial task @http://www-materials.eng.cam.ac.uk/mpsite/tutorial/default.html Check your learning by completing the following quizzes @http://www.the-warren.org/quiz/materials.htm @http://www.the-warren.org/quiz/usesofmaterials2.htm = Extension Task = You may wish to investigate further information contained in the above site about materials - This information will be studied for all DT options at IB = Resources = @http://www.bbc.co.uk/schools/gcsebitesize/design/resistantmaterials/materialsmaterialsrev_print.shtml @http://www.the-warren.org/rmcontents.html **The Main Families of Materials** Use the zoom and magnify 75% to see closer details.
 * Extension work**
 * Metals manufacture
 * Ferrous metals
 * Non-ferrous metals and alloys
 * Commercial stock of materials
 * Properties of metals
 * Changing the properties of metals
 * Recycling

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