Importance

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Abstract

The invention provides improvements to a composite member that has a plurality of plies. The improved composite member has (1) an interior ply which functions to dampen or resist sudden forces exerted on the composite member, (2) an intermediate load-carrying ply, and (3) an exterior abrasion-resistant ply. These plies have multiple, often intertwined fiber components disposed or imbedded with a matrix material, preferably Nylon-6 thermoplastic, to inhibit sharp edges during breakage. One or more of the plies typically has 'bi-axial' or 'tri-axially' braided fiber geometries wherein one or more fibers are helically wound about the circumference of the member. The helically oriented fibers are oriented at a selectively variable angle which influences the overall bending strength of the composite material. In one aspect, the angles of the fiber components and other factors are used to maintain substantially uniform cross-sectional area over the length of the tubular member while simultaneously varying the bending stiffness. In another aspect, the intermediate ply is constructed with two or more sub-plies. Such sub-plies can include tri-axially extending plies, and circumferentially-wound plies. The circumferentially-wound plies are often wound more tightly at the ends of the composite member to increase resistance to stresses caused by objects within the tubular shaft. A composite member constructed according to the invention resists sudden or impact forces and has high, selectively variable bending strength, high impact resistance, and safe failure modes.

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First Claim