Composites

Composites

1. Glass reinforced plastics

   • from thermosetting plastic resin that has been reinforced using very fine glass
   • Resin has strong compressive strength but weak tensile strength
   • Glass improves tensile strength of of the final product
   • good strength to weight ratio
   • resistant to corrosion
   • resin brittle on its own and can shatter
   • used a lot in boat building but can be prone to osmosis

2. Carbon Fibre

   • carbon fibres in carbon fibre composites are set onto polymer matrix
   • much stronger and ideal for structual applications such as aircraft, sports equipment and racing car manufacture
   • able to take tensile loads as well as compressive loads

3. Medium density fibreboard

   • mainly made from wood waste or specially grown softwoods
   • wood chips subjected to heat and pressure to soften fibres in the wood and produce a fine wood pulp
   • the pulp is then mixed with synthetic resins to bond the fibres of pulp together
   • this is then heated to produce a sheet material with a fine textured finish. After cooling the material is trimmed
   • can be laminated to improve strength or aesthetic qualities
   • when MDF is cut or sanded it produces very fine fibres or dust. Care must be taken and dust extraction systems should be used as well as dust masks
   • E.g. furniture or kitchen units or worktops
   • disadvantage is weight- very heavy
   • usually veneered with a thin layer of high quality wood or formica

4. Chipboard

   • wood particles glued together under heat and pressure
   • comes in normal, medium and high density form
     • normal is relatively soft
     • high is solid and hard
   • only suitable for indoor applications such as work surfaces in kitchens where it is veneered to give it an attractive finish
   • if it gets wet it becomes waterlogged, starts to swell and breaks down

5. Laminates

   • is produced by bonding together two or more layers of materials
   • Usually very stable
   • do not warp or misshape
   • easier to work than solid woods
   • although cheaper than solid woods they're not as aestetically attractive and need to be finishedby veneering or even painting

6. Blockboard

   • strips of softwood 25mm wide and positioned edge-to-edge
   • covered with veneer, usually beech, the glued together under very high pressure
   • usually waterbased therfore only suitable for indoor use
   • good resistance to warping
   • when blockboard is cut the edges sometimes do not match the hardwood veneer of the upper and lower surfaces

7. Plywood

   • layers of veneers bonded together using glue
   • thin sheets of wood (1mm think) obtained from timber using the rotary cut process
     • (log paced on lathe and turned against a broad cut knife)
   • does not warp or distort
   • very strong and stable sheet material due to each layered grain at 90 degrees
   • when wet layers can delaminate and layers can come apart
   • E.g. marine ply with waterproof glues used in the manufacture of boats