High-Tech Fibers Glass And Carbon For M-Ship Applications

The majority of improvements in marine composite construction over the last fifty years have been through better resin chemistry. However, fibers have also played an important roll in the development of advanced composite laminates for marine applications. Specifically, weight, strength and stiffness optimization can be enhanced by using fibers with properties superior to E-glass. However, what we’ve found is that often a judicious use of high strength and/or modulus materials in combination with E–glass can often result in an efficient, cost-effective composite structure.

GLASS
Glass fibers account for over 90% of the fibers used in reinforced plastics because they are inexpensive to produce and have relatively good strength to weight characteristics.  Additionally, glass fibers exhibit good chemical resistance and processability. The excellent tensile strength of glass fibers, however, may deteriorate when loads are applied for long periods of time E-glass (lime aluminum borosilicate) is the most common reinforcement used in marine laminates because of its good strength properties and resistance to water degradation. S-glass (silicon dioxide, aluminum and magnesium oxides) exhibits about one third better tensile strength, and in general, demonstrates better fatigue resistance. Because the cost for this variety of glass
fiber is about three to four times that of E-glass we don’t see it used too much in the marine industry.

CARBON
The terms “carbon” and “graphite” fibers are typically used interchangeably, although graphite technically refers to fibers that are greater than 99% carbon composition versus 93 to 95% for PAN-base fibers. All continuous carbon fibers produced to date are made from organic precursors, which in addition to PAN (polyacrylonitrile), include rayon and pitches, with the latter two generally used for low modulus fibers. Carbon fibers offer the highest strength and stiffness of all commonly used reinforcement fibers. The fibers are

not subject to stress rupture or stress corrosion, as with glass and aramids. High temperature performance is particularly outstanding. The major drawback to the PANbase fibers is their relative cost, which is a function of high precursor costs and an energy intensive manufacturing process.

Carbon fiber use for marine structures is most useful for designs that are limited by how stiff we can make them, such as long, slender bodies that don’t have much Section Modulus. That’s why catamarans and trimarans often use carbon. Vessels with a lot of surface area, such as hovercrafts or the M-Ship concept also can benefit from sandwich laminates with carbon skins. Carbon is also used exclusively for composite masts,
rudder posts, and other sailboat hardware as well as in the caps of stringers when height of the stringer is limited.

Earthrace
The Earthrace project was established to break the outright world record for circumnavigating the globe in a powerboat, which currently stands at 75 days, but has a loftier goal of promoting the use of renewable fuel. Circumnavigating the globe is the world’s longest race at 24,000 nautical miles, and represents the pinnacle of powerboat challenges. The Earthrace team plans to make this trip in 65 days using only bio-diesel fuel made from renewable sources such as canola and rape, hoping that the high profile nature of the project will significantly raise awareness about the use of sustainable resources.

M-Ship
M-Ship has built The carbon fiber Stiletto, a Twin M hull vessel that is 80 ft in length with a 40 ft beam. The vessel's draft fully loaded is 3 ft and is designed for a speed of 50-60 kts. Its superior performance is based on M Ship Co.'s proprietary, globally-patented technology that recaptures the bow wave to create an air cushion for more efficient planning. The M80 Stiletto is also notable because it is the largest U.S. Naval vessel
built using carbon fiber composite and epoxy building techniques, which yields a very light, but strong hull. Figure 2 shows the M80 underway with a low radar cross signature.