Loading rate and temperature dependence of flexural behaviour of unidirectional pitch-based CFRP laminates

The mechanical behaviour of polymer resins heavily depends on time and temperature, in a manner which is termed viscoelastic behaviour. It is therefore presumed that the mechanical behaviour of fibre-reinforced plastics (FRPs) also depends on time and temperature because of the viscoelastic behaviour of the matrix resin. The flexural static and fatigue behaviour of three kinds of unidirectional pitch-based CFRP laminates, which are a combination of two types of resin and two types of fibre, were evaluated at several levels of loading rates and constant temperatures. The flexural static and fatigue behaviour was found to be remarkably dependent on time and temperature. The time-temperature superposition principle of the mechanical behaviour of the matrix resin held for the flexural fatigue strength as well as the flexural static strength of the CFRP laminates. Clearly, the flexural static and fatigue behaviours of the CFRP laminates were dominated by the viscoelastic behaviour of the matrix resin.