Fibre Engineering Properties.
Basic comparison between the main desirable features of generic fibres.
Notes about the materials.
S-Glass Compared with E Glass, this has higher strength, and high stiffness. As it is glass it is non flammable, resistant to heat, has good chemical resistance and maintains its strengtth over a wide range of conditions. It is more expensive, has relatively low fatigue resistance and higher density compared to carbon and organic fibres.
Aramid, Kevlar Kevlar is the Dupont trade name for Aramid. The bright golden yellow filamentshave high strength and low density which gives very high specific strength. All grades have good resistance to impact, and lower modulus grades are used in ballistic applications. They also offer good resistance to abrasion and thermal degradation, howver UV will slowly cause deterioration.
Carbon Produced by the controlled oxidation (burning) of (usually) polyacrylonitrile fibres. Carbon fibre has the highest stiffness of any commercially available fibre, high strength in tension and compression and high resistance to corrosion, creep and fatigue. Carbon however has lower impact strength than glass and some have particularly brittle characteristics.
Innegra A tough, light weight, high performance fibre. Can often be substituted for other fibres with little re-engineering. It has high tenacity and stiffness, high toughness and energy absorption, great thermomechanical stability, good creep resistance, and good chemical resistance. When carbon fails, it usually does so catastophically. With Inegra it is possible to design for a prgressive failure without compromising other properties. Inegra is being used in automotive applications, aerospace, boating, sporting goods, surfboards, kayaks and canoes, helmets, and ballistioc armor.
Dynel A low density, high tenacity fibre with good impact resistance but low modulus. Its lack of stiffness usually precludes it from inclusion in a composite component, but it is useful where low weight, high impact or abrasion resistance, and low cost is required. It is mainly used as a surfacing material, as it can be very smooth, keeps weight down and works well with most resin types.
Selecting the Correct Fabric Fabrics (or cloths) are usually woven materials with warp and weft at 90°to each other. For general sheathing, isotropic properties are acceptable (same properties in both directions). Fabrics of between 165g/sqm-290g/sqm (or 5oz-8oz/sq.yd) are most common as they are easy to handle and can be used in multiple layers if necessary in areas requiring additional reinforcement. Unidirectional materials and some stitched multiaxial materials can also be used but their use is more specialized. Their specific fibre orientation and flat construction make them ideal for structural sheathing.
Orientation of Fabric Finally, since reinforcing fibres are designed to be loaded along their length, and not across their width, the orientation of the fibres creates highly ‘direction-specific’ properties in the composite. This ‘anisotropic’ feature of composites can be used to good advantage in designs, with the majority of fibres being placed along the orientation of the main load paths. This minimises the amount of parasitic material that is put in orientations where there is little or no load.
Boatcraft Pacific does not hold itself out as an expert in the above matters. The information has been compiled from a number of sources and has not been independently verified. Boatcraft pacific takes no responsibility for its accuracy and will accept no liability no matter how it may arise which flows from reliance on the above information.
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