Fibre-reinforced polymer composites (FRPs) have been used successfully in marine applications for several decades in areas such as radomes and mass structures, super yachts, work boats and leisure craft. More recently FRPs have been used in less well known applications such as bearings, propellers, commercial hatch covers, exhausts and topside structures. The use of glass-fibre composites (GRP) in marine applications was one of the first significant areas of GRP use. It has revolutionised the capability to design and manufacture large composite structures in several sectors. Vessels are made in the UK by a variety of processes, including hand-lay GRP, resin-infusion, thermoplastics and high performance carbon fibre prepreg for racing yachts.
The main advantages of GRP for marine applications are:
- Environmental resistance, including freedom from rotting, corrosion, etc.
- Ability to mould seamless, complex shaped structures
- Ability to tailor strength to suit loading conditions
- Excellent strength to weight characteristics – GRP marine structures generally half the weight of equivalent steel structures.
- Low maintenance and ease of repair
- Excellent durability
Racing yachts use composites more extensively than any other marine structure. The materials used are not typical of marine construction because of special requirements. Minimal weight and maximum stiffness are crucially important in their design so that they can sail with maximal speed and resistance to the impact of waves and other elements in marine environments. Carbon fibre reinforced epoxy composites are usually used in boat hulls cored with honeycomb or foam, frames, keels, masts, poles and boom, carbon winch drums and shafting. The use of FRPs can contribute to improved performance and minimise the danger of sailing drawbacks and failure in the different international sailing conditions.
The main subsea application of composites has been as protection structures for subsea wellheads and valves. The advantage of using composites is weight saving which can give substantial savings in installation cost through the use of lower cost lift vessels. The cost of manufacture is competitive with that of conventional steel and concrete technology.