2: Continuous Fibre Composites
The simplest method of producing continuous fibre composites is through the hand lay-up process. In a similar manner to the spray lay-up process a mould is used to which a gel coat is applied. The continuous fibres are then hand laid onto the mould in the form of cloth, mat, or fibre strands. The fibres stick to the gel coat and follow the contours of the mould surface. Further resin is then poured onto the fibres and impregnated using a roller. Successive layers of fibres are added until the desired thickness is achieved.
Quite often, high pressure gases or vacuums are used to force the plies together in the laminate, thereby creating good adhesion and bonding during the curing process. These pressures can be achieved by placing the laminate in a high pressure chamber, known as an autoclave, or placing the laminate inside a vacuum bag.
A limitation of the hand lay-up process is that it can only produce single components. Quite often continuous components such as rods, tubes, or sheets are required. These designs can be fabricated using the pultrusion process. The pultrusion process is designed to extrude a polymer matrix around continuous fibres to form a product of constant cross-section. The fibres are impregnated by passing them through a polymer resin bath. They are then drawn together to form the desired shape before they are passed through a heated oven to be cured.