Recent Developments in Polyester Matrices and Reinforcements for Marine Applications, in Particular Polyester/Kevlar Composites

Abstract

Since their acceptance into the marine world, reinforced plastics—and, in particular, glass-reinforced polyester resins—have been used for the fabrication of boats and other marine structures. In the early learning days over design made it possible to use inexpensive systems, which were not necessarily the best for the job. However, in recent years, as composite marine structures have increased in size (the largest, at present, being the 55 m ‘Brecon’ class of mine countermeasure vessel) or where performance is the major criterion (as in power boats and racing yachts) a move has been made towards the use of improved material for construction.

On the resin side, isophthalic acid and isophthalic-neopentyl glycol based unsaturated polyester resins have been developed to give improved water resistance, blister resistance, toughness and long-term retention of mechanical properties. These systems also form the basis of many successful gelcoats, which afford the first barrier to protect the structural laminate. In recent years it has been recognised that sensible practice would be to use these types of resin throughout the structure to provide a material with the best possible performance.

On the reinforcement side there have been developments in size technology for E-glass to provide improved fibre I resin bonding. Also, many types of glass mat have been developed to provide maximum reinforcing action in any direction. However, glass is rather dense compared with polyester resin and, for applications where weight and performance are paramount, lightweight reinforcements are being developed which are currently receiving careful consideration as alternatives to glass fibre.

In particular, polyaramid fibres are strong contenders to partially or completely replace glass in such applications because of their low density, high strength and high stiffness.

Data obtained from composites constructed using Crystic* polyester resins and Kevlar poly ar amid fibres are discussed in detail in this chapter and the possibility of combining glass and Kevlar fibres to give optimum laminate and structural performance is investigated.

Kevlar is Du Pont’s registered trade mark.