Composites

• 3 categories of composites 


  • fibre based - reinforced with fibres
  • particle based - reinforced with particles
  • sheet based - boards made from wood pulp, chips or layers
• a composite is a mixture of materials combined to enhance their individual properties
• the characteristics of fibre based composites are


  • good strength to weight ratio
  • resistance to corrosion
  • good fatigue resistance
  • low thermal expansion
• fibre based composites


  • glass fibre
  • carbon fibre
  • kevlar
• glass fibre - glass reinforced plastic (GRP)

  • is spun to product a fibre which is then coated to aid bonding to the resin
  • the glass fibres are available in a variety of thicknesses
  • a mould is required for GRP which can be produced cheaply
• carbon fibre - carbon fibre reinforced polymer (CFRP)

  • fibres are woven into a matt which is cut to shape to then be placed in a mould where resin is applied and forced into shape
  • popular in the production of F1 cars
• kevlar

  • is a mixture of aromatic and aramid molecules melted together and spun into fibres
  • has very high strength, high chemical resistance, 5 times stronger than steel but half of fibreglass
  • used for: body protection, sports equipment, sails for windsurfing
• characteristics of particle based composites


  • high strength in compression
  • good stability
  • uniform structure ensuring consistent strength
  • generally free from surface defects
• particle based composites 


  • concrete
  • cerments
• concrete

  • made up of materials known as aggregates as well as sand and cement
  • can be reinforced with GRP to make glass reinforced concrete which allows for more complex shapes
• cerments

  • a mixture of meta and ceramic particles
  • cerments are resistant to high temperatures, are tough and shock resistant
• sheet based composites are generally known as manufactures boards
• kitchen knives, flooring and bicycle frames have all be replaced by composites in some cases as the product has improved with the composite features added
• metal/polymer composites are slowly being introduced as it results in lightweight but durable materials which have good impact resistance

  • ALU has been developed which is a aluminium sheet with a polyethylene core
  • it can be used for vehicle skins as it will reduce weight and noise reduction - also parts in boats