Composites

Question 1

What is a composite?

Answer 1

• two or more chemicals combined by bonding
• improved mechanical, functional, aesthetic properties
• usually have excellent strength to weight ratios

Question 2

Give an overview of glass fibre (GRP)

Answer 2

• polyester of epoxy resin reinforced by glass fibres in a woven matting
• plastic resins are strong in compressive strength but weak in tensile strength
• glass fibres are strong in tensile strength but have no compressive stgrength
• combined GP has both compressive and tensile strength
• resin is a liquid requiring harderner or catalyst to harden
• glass fibres provbied basic structure
• resin bonds fibres together
• glass may be placed specifically in places with high tensile loads
• smooth finished achieved by polished mold + gel coat
• one side is highly polshed , one side is very rough

Question 3

How is GRP hand layed up?

Answer 3

1. mould checked for defects
2. mould polished with wax
3. thin film of release agent added to inside mould
4. gel coat applied to mould - causes resin to cure
5. layer of fibre added then resin rolled into the layer
6. repeated
7. when product is fully cured, GPR removed from mold
8. any blemishes in the mould are reproduced in final moulding