Prouduct Design (Composites)

Overview of Composites

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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 formedGLASS REINFORCED PLASTIC – GRP – FIBREGLASS.

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Two main groups of composites

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

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Wooden Composite Materials

- 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

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Fibre reinforced composite materials

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

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Kevlar

- 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

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Particle Based Composites

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.

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Cermets

- 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

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