Page 187 - Plastics Engineering

170 Mechanical Behaviour of Composites

Strain (%)
Fig. 3.2 Qpical tensile behaviour of fibres

3.3 wpes of Matrix
The matrix in a reinforced plastic may be either thermosetting or thermoplastic.

(a) Thermosets
In the early days nearly all thermosetting moulding materials were compos-
ites in that they contained fillers such as woodflour, mica, cellulose, etc to
increase their strength. However, these were not generally regarded as rein-
forced materials in the sense that they did not contain fibres.
Nowadays the major thermosetting resins used in conjunction with glass
fibre reinforcement are unsaturated polyester resins and to a lesser extent epoxy
resins. The most important advantages which these materials can offer are that
they do not liberate volatiles during cross-linking and they can be moulded
using low pressures at room temperature. Table 3.1 shows typical properties of
fibre reinforced epoxy.