Interlaminar shear fatigue of pultruded graphite fibre-polyester composites

The effect of cyclic loading on the interlaminar shear strength of pultruded graphite fibre-polyester was determined. Two fibre volume fractions, 0.5 and 0.33, were studied. The results indicate that the deterioration in the interlaminar shear strength with cycling is significantly greater than in flexural fatigue. The higher volume fraction material showed a greater drop in the interlaminar shear strength than the lower volume fraction material. Unlike the monotonic strengths, the effect of the fibre volume fraction on interlaminar shear fatigue strength at high cycles is small, indicating that there is little advantage in increasing the fibre volume fraction to improve the interlaminar shear strength in high cycle fatigue environments. A critical stress was determined above which interlaminar shear fatigue failure did not occur within 10⁷ cycles for the materials tested.