Reinforced Polymers

Abstract Polymers are sometimes reinforced with stiff, strong fibres (often glass fibres or carbon fibres) or other particles, and their resulting properties can be estimated using an approximate micromechanical analysis. The matrix can be a thermoset (often epoxy resin) or a thermoplastic. Several forming processes are available, including pultrusion and filament winding and (for small particles in thermoplastics) the usual processes for thermoplastics. All elastic constants are predicted for a representative volume element, for the case of aligned, continuous fibres. A consistent three-dimensional analytical approach is followed, by approximating mean stresses in the matrix: stiffnesses predicted are then lower bounds. For short fibres, the shear-lag model is incorporated. Axial tensile strength can also be estimated, allowing for finite interfacial shear strength in the case of short fibres. Elastomers are usually reinforced by microscopic carbon black particles. Under cyclic loading, they characteristically exhibit the Mullins effect, caused by damage at particle–matrix interfaces.