A fibre-reinforced resin system is a composite material consisting of a network of reinforcing fibres embedded in a matrix of thermosetting resins. Other materials like fillers and pigments may also be present, although they are not an essential part of the composite.
How is the resin used to form a composite material or laminate?
In general, the resin used consists of a syrupy liquid which, when combined with a suitable catalyst or hardener, can be cross linked into a hard infusible solid. The composite material or laminate is formed by impregnating the catalysed resin with fibrous material (usually in the form of a cloth or mat) and allowing the resin to cure. This process is carried out in a mould which may be open or closed. The resultant product is a fully cured moulding which is an exact replica in reverse of the original mould surface.
In general, where glass is used as the reinforcing fibre, the product is referred to as a fiberglass laminate, whereas if carbon fibre is used as reinforcement the product is referred to as a carbon fibre composite.
ADVANTAGES OF FRP
Why use FRP? The answers to this question are many and varied and may be simple or complex, owing to the fact that the family of materials which can be classified as FRP is vast. So we will list the advantages of only glass reinforced polyester resins below:
• Thermoset – does not change shape after heating
• Advantageous strength/weight ratio and rigidity
• Moulding size virtually unlimited.
• Ease of fabrication.
• Wide range of manufacturing techniques
• Low capital outlay – for hand lay-up
• One-off or few-off moulding is possible at reasonable cost.
• Considerable design versatility
• Can be combined with other materials… e.g. foams for buoyancy.
• Excellent water resistance
• Resistant to a wide range of chemicals
• Resistant to weathering and UV exposure.
• Can be coloured to give a maintenance-free finish.
• Fire retardant if required
• Transparent/ translucent if required
• Good electrical and thermal properties
imilar comments apply to glass reinforced epoxide resin systems although cure and handling characteristics and cured properties are a little different.
With carbon fibre reinforced resin systems the composites are, of necessity, black and so some of the advantages above do not apply. However, in this case specific strength and modulus are sufficiently greater than those of most other materials including metals that such composites are highly attractive to designers for applications where wt. is of prime importance.
Costs :
In the case of FRP, since the major resins – polyester and epoxide – are derived from oil, cost is related to crude oil price. In view of the world shortage of crude oil, and the continual price increases, FFRP costs will continue to rise. What long term effect this will have on FRP consumption will depend on a variety of other economic factors. Though in some areas one can foresee FRP being priced out of the market, in general the prospect for the future is unlikely to be as bleak as some would believe.
– From the book FRP Technology by R.G.Weatherhead.
