Prouduct Design (Composites)

- Composites mix together two or more materials so that the properties of each material are enhanced and used.

- For example – Adding strands of glass (fibres) to polyester resins, a very tough, rigid, lightweight, material is formed – GLASS REINFORCED PLASTIC – GRP – FIBREGLASS.

1) Fibre Reinforced Composites

- Natural woods

- Polymers mixed with fibres

- GRP – Plastic Laminates – Carbon Fibre

- Elastomers mixes with fibres

- Concretes mixed with fibres

2) Particle Based Composites

- Cermet’s (ceramic & metal)

- Tungsten and Titanium carbide

- Concrete & Tarmac

- Plywood

- MDF

- Chipboard

- Blockboard

- Hardboard

Advantages of man-made boards

- Increased stability against warping

- Equal strength in all directions – unlike natural wood

- Available in large sheets

- A strong, lightweight and weatherproof material (Drawing below)

- Kevlar has long chain molecules which run parallel along the length of the fibres

Arrangement of Kevlar Fibres

- This makes it very strong.

- Weight for weight Kevlar is x5 stronger than steel

- And is ½ the density of fibreglass

- Kevlar fibres are woven into a ‘cloth’

- Made into protective clothing it works like a net absorbing the force of a football on impact

- Uses include bullet proof vests – skis – helmets – racquets – windsurfing sails – run flat tyres – cut proof gloves

Pre-Tensioned Reinforced Concrete -

- Ordinary concrete is strong under compression. Foundation beams may crack under tension.

- The surface may crack with ordinary reinforced concrete.

- Pre tensioned reinforcing bars will greatly reduce any cracking.

- A mixture of metal & ceramics

- Tungsten Carbide

- A mix of the ceramic tungsten carbide & the metal cobalt

- Used for cutting tools, both hand & machine.

- Keeps its sharp edge very well