
Composites 339
Figure 16.3 Wood, cellulose fibres in a lignin matrix
3 Dispersion strengthened, e.g. precipitation hardened aluminium-copper
alloy.
16.2 Fibre-reinforced materials
The main functions of the fibres in a composite are to carry most of the load
applied to the composite and provide stiffness. For this reason fibre materials
have high tensile strength and a high tensile modulus. Ceramics are frequently
used for the fibres in composites. Ceramics have high values of tensile strength
and tensile modulus, and also a useful asset of low density. However, ceramics
are brittle and the presence of quite small surface flaws can markedly