Effects of load interruption on the fatigue life of GFRP composites

The effect of cyclic loading interruption on the fatigue behavior of angle-ply (±45)2S glass/epoxy composite laminates was investigated by comparing the obtained results of continuous- and interrupted loading patterns. Continuous fatigue experiments were performed by applying a sinusoidal cyclic loading pattern with maximum cyclic stresses at six different stress levels. For interrupted fatigue experiments, the cyclic loading was interrupted for two hours at regular intervals, corresponding to 20% of the fatigue life under continuous loading at the same maximum cyclic stress level. It was observed that the distribution and the severity of the fatigue damage was a function of loading pattern and stress level. Damage was more uniform when interrupted fatigue loading was applied. This loading pattern decelerated damage growth and increased the specimen’s capacity to accumulate damage. The specimens loaded under interrupted fatigue exhibited longer fatigue lives than those continuously loaded. This enhancement of fatigue was more pronounced at high stress levels.