High Modulus
The High Modulus Company of New Zealand is a world-leading supplier of composite technology and structural engineering services to the marine industry. I asked Michael Eaglen, Vice President of Engineering about recent projects they’re working on that involve carbon fibers. “The first is a 37m (121') 60-knot vacuum infused carbon/epoxy/foam motoryacht. The designer is Rob Humphreys Yacht Design in England; the builder is McMullen and Wing in New Zealand. This project used quite a bit of ultra high modulus fiber for very light inside skin of deck panels and the like.
“The second is a 40m (130') luxury day-sailor in prepreg carbon with foam and honeycomb cores. The designer is Javier Soto Acebal in Argentina; the builder is Wally in Italy. The project uses quite a bit of intermediate-modulus fiber in the hull and deck shells for global stiffness. It also has a combination of standard, intermediate and high modulus fiber in the rudder stock.
“Finally we are currently doing a lot of work with Rhebergen Composites in Amsterdam on mast structures for very large (80-120m) motoryachts. These are primarily governed by their vibrational behavior, so we use increasingly high modulus carbon fibers (mostly M46J and HS40) to lift stiffness without increasing weight in order to tune the natural frequencies of the structure.”
The most f common aramid fiber is Kevlar® developed by DuPont. This is the predominant organic reinforcing fiber, whose use dates to the early 1970s as a replacement for steel belting in tires. The outstanding features of aramids are low weight, high tensile strength and modulus, impact and fatigue resistance, and weaveability.
Compressive performance of aramids is not as good as glass, as they show nonlinear ductile behavior at low strain values. Water absorption of un-impregnated Kevlar® 49 is greater than other reinforcements, although ultra-high modulus Kevlar® 149 absorbs almost two thirds less than Kevlar® 49. The unique characteristics of aramids can best be exploited if appropriate weave style and handling techniques are used.
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