Glass-fiber Reinforced Plastics (GRP) in the Marine Industry

Composite materials are relatively new to the marine industry, having only come into use within the last 50 years. Glass-fiber reinforced plastics (GRP), one form of fiber reinforced plastics (FRP), were first introduced in the 1940‘s for use in Navy personnel boats. Since that time, the use of FRP materials have found widespread acceptance in yachts, pleasurecraft, performance craft (i.e. racing boats), and small commercial vessels such as fishing trawlers. The advantages of GRP include improved strength-to-weight ratios, stiffness-to-weight ratios, and corrosion resistance. Interest in the use of composite materials for larger vessels has been increasing in recent years, primarily for high speed passenger craft. However, use of GRP in construction of large ships is limited partly due to problems with hull deflections that may cause problems in propeller shafting and piping arrangements.

The first major interest in commercial FRP vessels was in the fishing industry, Today, approximately 50% of commercial fishing vessels are of FRP construction. As with other initiatives in engineering and technology, the military has led research and development of composite materials sinceWorld War II. The Navy and Army have integrated several applications of composites into their vehicles, namely small boats, submarines, patrol craft, and minesweepers. Other components, ranging from small equipment brackets to propellers have also proven effective.

Composites hulls also offer a number of stealth benefits. Firstly, they are non-magnetic, making them less susceptible to mines and torpedoes. They can be made to absorb radar energy rather than reflect it, rendering the structure with lower radar cross-sections. They have significantly lower harmonic resonance, hence they are markedly quieter in the water. Their thermal properties allow for considerably lower thermal signatures. 

Small boat construction have been done by GRPs for 50 years. Today this industry is dominated by GRPs. The reason is that GRPs allow fast and inexpensive mass production. For large ship hulls, GRPs are not suitable due to flammability of plastics. However, small boats and fishing vessels are good application fields. In some countries, for passenger transport, sandwich construction is used. Composites for commercial ship building have been used by U.S when economically suitable and when they are needed for performance. Cargo ships and tankers are the examples of larger ships where composites are used. For the military applications, GRP usage is limited for larger ships and submarines due to performance requirements and cost. However, a lot of engineering studies are being conducted.

 

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