PDF Publication Title:
Text from PDF Page: 023
Recreational Use of FRP Marine Composites Single-Skin Construction Early fiberglass boat building produced single-skin structures with stiffeners to maintain reasonable panel sizes. Smaller structures used isotropic (equal strenxgathndiny directions) chopped strand mat layed-up manually or with a chopper gun. As strength requirements increased, fiberglass cloth and woven roving were integrated into the laminate. An ortho-polyester resin, applied with rollers, was almost universally accepted as the matrix material of choice. Sandwich Construction In the early 1970s, designers realized that increasingly stiffer and lighter structures could be achieved if a sandwich construction technique was used. By laminating an inner and outer skin to a low density core, reinforcements are located at a greater distance from the panel’s neutral axis. These structures perform exceptionally well when subjected to bending loads produced by hydrodynamic forces. Linear and cross-linked PVC foam and end-grain balsa have evolved as the primary core materials. Resin Development General purpose ortho-polyester laminating resins still prevail throughout the boating industry due to their low cost and ease of use. However, boat builders of custom and higher-end craft have used a variety of other resins that exhibit better performance characteristics. Epoxy resins have long been known to have better strength properties than polyesters. Their higher cost has limited use to only the most specialized of applications. Iso-polyester resin has been shown to resist blistering better than ortho-polyester resin and some manufacturers have switched to this entirely or for use as a barrier coat. Vinyl ester resin has performance properties somewhere between polyester and epoxy and has recently been examined for its excellent blister resistance. Cost is greater than polyester but less than epoxy. Unidirectional and Stitched Fabric Reinforcement The boating industry was not truly able to take advantage of the directional strength properties associated with fiberglass until unidirectional and stitched fabric reinforcements became available. Woven reinforcements, such as cloth or woven roving, have the disadvantage of pre-buckling the fibers, which greatly reduces in-plane strength properties. Unidirectional reinforcements and stitched fabrics that are actually layers of unidirectionals offer superior characteristics in the direction coincident with the fiber axis. Pure unidirectionals are very effective in longitudinal strength members such as stringers or along hull centerlines. The oo most popular of the knitted fabrics is the 4b5y 45 knit, which exhibits superior shear strength and is used to strengthen hulls torsionally and to tape-in secondary structure. Advanced Fabrication Techniques Spray-up with chopper guns and hand lay-up with rollers are the standard production techniques that have endured for 40 years. In an effort to improve the quality of laminated components, some shops have adapted techniques to minimize voids and increase fiber ratios. One technique involves placing vacuum bags with bleeder holes over the laminate during the curing process. This has the effect of applying uniform pressure to the skin and drawing out any excess resin or entrapped air. Another technique used to achieve consistent laminates involves using a mechanical impregnator, which can produce 55% fiber ratios. 10PDF Image | Marine Componsites
PDF Search Title:
Marine ComponsitesOriginal File Name Searched:
MARINE_COMPOSITES.pdfDIY PDF Search: Google It | Yahoo | Bing
Development of a solar powered Electric Ship The Electricship website originally started off as a project to develop a comprehensive renewable, affordable, modular electric ship... More Info
Modular Boat Hull Composite The case for a unsinkable, modular composite hybrid boat hull... More Info
MS Burgenstock Hybrid Electric Catamaran Lake Lucerne Unique shuttle servicing Lucerne to the Burgenstock Resort... More Info
Ground Power Unit GPU Powered by Lithium Ion Batteries The goal of the Ground Power Unit is to provide a readily accessible, modular, ready-to-power solution for remote power... More Info
CONTACT TEL: 608-238-6001 Email: greg@electricship.com (Standard Web Page)