High TechNology Keflar And Fibers Make Patrol Boat With WarShip

The Taiwan-based shipbuilder has constructed six patrol boats to date, all of which use a combination of Kevlar®/E-glass in all main structures including hill and wheelhouse. Use of Kevlar® fiber/e-glass hybrid in these boats to strengthen hulls and other structures in order to reduce speed-sapping weight. “There has never been any fault with advanced composites; just a lack of understanding how to get the best out of them,” says Ken Raybould, the British consultant to DuPont that helped launch Kevlar® into the marine industry.

In his crusade for Kevlar®, Raybould scientifically addressed each of the perceived shortcomings of the fiber, such as wet-out, compression strength, water absorption, UV resistance, and handling (cutting and machining). The wet-out issue goes away with the use of E-glass/Kevlar hybrids. This also reduces overall material cost by optimizing Kevlar®’s advantages with the lower-cost E-glass in a hybrid weave. Water uptake is mostly a function of resin performance. Coatings can handle the UV issue and tools have been developed to cut Kevlar® before and after its laminated. Figure 7 shows a fast Customs boat from Spain made with Kevlar®.

Sails and High Tech Fibers
Newer sails on racing sail boats are another place where high strength fibers are becoming more prevelant. According to Doug Stewart, Production Manager at Quantum Sailmakers, “Fiber currently being used in high end sails is Carbon and Twaron. Currently in the highly competitive TP 52 class sails are 100% carbon. Low modulus carbon has great strength to weight and is very flexible fiber as long as it is not saturated in the lamination process. At this point in the process of high end sails the key is the perfect mix of fiber, pressure and heat. Not enough fiber, you have a sail that is light but will not hold its desired shape. Not enough glue, you have a sail that is light but will probably delaminate long term.

“What will the next sail making revolution bring? There is no doubt that there is another super fiber like carbon right around the corner! Mylar, the outer skin of the sail which is really used to hold the fiber and glue in place probably is the next area where we will see changes. Films will get stronger which means sailmakers will be less reliant on fiber. My opinion is that within 10 years we will see a sail just made of film. Initially very expensive and not very durable but in the high end arena of America’s Cup (AC) and TP 52s, money certainly is not the issue.”

HIGH TECH FIBERS
Other high-tech fibers have yet to establish themselves in the marine market. Basalt was investigated by High Modulus, but they concluded from their testing that “ The Basalt unidirectional material was not significantly stronger or stiffer than the E-glass unidirectional.” The M-5® fiber development effort received a boost when DuPont bought a majority share of the company making the fibers marketed as having potential as an ultra-high strength, ultra-high thermal and flame resistant alternative to products currently available in the advanced fibers market.

Nova Craft Canoe has developed a laminate that combines a leading edge Kevlar®/Carbon material combined with Spectra® and applied through an infusion process. The result is a tough, rigid canoe that’s surprisingly light and easy to handle. Once plasma-treated surfacing helped improve resin adhesion, Spectra® has mostly been limited to canoe applications. So although carbon and Kevlar® have made significant inroads into the marine composites world, E-glass remains the workhorse of the industry. Certainly when weight
is at a premium, Kevlar® or carbon fiber laminates can be justified. For stiffness-limited designs, carbon unidirecitonals can help optimize a laminate.