Composites get their strength from the type, amount, and arrangement of the fibre reinforcement. While over 90% of the reinforcements in use are glass fibres, other reinforcements have established a critical niche.
Arrangement of the glass fibres, or how the individual strands are positioned, determines both direction and level of strength achieved in a moulded FRP/Composite. The three basic arrangements of glass fibre reinforcement are unidirectional, bidirectional and multidirectional.
Unidirectional arrangements provide the greatest strength in the direction of the fibres. Unidirectional fibres can be continuous or intermittent, depending on specific needs determined by part shape and process used. This arrangement permits very high reinforcement loading for maximum strengths.
The fibres in a bidirectional arrangement are in two directions – usually at 90 degrees to each other, thus providing the highest strength in those directions. The same number of fibres need not necessarily be used in both directions. High fibre loading can be obtained in woven bidirectional reinforcements.
Multidirectional or random arrangements provide essentially equal strength in all directions of the finished part.
are supplied in several basic forms to provide flexibility in cost, strength, compatibility with the resin system, and process requirements. Regardless of the final form, all fibre reinforcements originate as single filaments.
A large number of filaments are formed simultaneously and gathered into a strand. A surface treatment is then applied to facilitate subsequent processing, maintain fibre integrity, and provide compatibility with specific resin systems. After this treatment, the strands are further processed into various forms of reinforcements for use in moulding FRP/Composites.
Continuous Strand Roving
This basic form of reinforcement is supplied as untwisted strands wound into a cylindrical package for further processing. Continuous roving is typically chopped for spray-up, preform or sheet moulding compounds. In the continuous form, it is used in pultrusion and filament-winding processes. Woven Roving Woven from continuous roving, this is a heavy, drapable fabric available in various widths, thicknesses and weights.
Woven roving costs less than conventional woven fabric and is used to provide high strength in large structural components such as tanks and boat hulls. Woven roving is used primarily in hand lay-up processing.
Made from fibre yarns, woven fabrics are of a finer texture than woven roving. They are available in a broad range of sizes and in weights from 21/2 to 18 oz./sq. yd. Various strength orientations are also available.
Made from either continuous strands laid down in a swirl pattern or from chopped strands, reinforcing mat is held together with a resinous binder or mechanically stitched. These mats are used for mediumstrength FRP/Composites. Combination mat, consisting of woven roving and chopped strand mat bonded together, is used to save time in hand lay-up operations. Hybrid mats of glass and carbon and aramid fibres are also available for higher-strength reinforced products.
Surfacing mat or veil is a thin fibre mat made of monofilament and is not considered a reinforcing material. Rather, its purpose is to provide a good surface finish because of its effectiveness in blocking out the fibre pattern of the underlying mat or fabric. Surfacing mat is also used on the inside layer of corrosion-resistant FRP/Composite products to produce a smooth, resin-rich surface.
Chopped strands or fibres are available in lengths from 1/8” to 2” for blending with resins and additives to prepare moulding compounds for compression or injection moulding and other processes. Various surface treatments are applied to ensure optimum compatibility with different resin systems.Contact us to discuss your project with one of our experts in the field.