Fatigue damage evolution in off-axis unidirectional CFRP

Damage mechanisms have been evaluated for a unidirectional carbon fibre reinforced epoxy matrix composite under off-axis cyclic loading. The variation in fatigue life for a given cyclic strain was found to be dependent upon the microstructure and the ease with which coalescence of matrix microcracks took place. When matrix cracks coalesced quickly, the fatigue life was relatively short. On the other hand, when the microcracks were well distributed, coalescence was delayed and the fatigue life was much longer.