Accurate Tension-Tension Fatigue Testing of Unidirectional Composites

Abstract

The fatigue behavior of composites is generally described by the S-N curve of unidirectional (UD) composites. However, obtaining reliable fatigue data hinges on a test method that guarantees uniform stress distribution over the gauge section. The standard methods introduce stress concentrations close to the end tab edge and hence lead to premature failure. To find the method yielding the highest fatigue life, the current work examines different specimen configurations. The standards and two well-known configurations as well as a novel arrow-shape one are studied. The standard configuration, rectangular specimens with rectangular and tapered end tabs, yielded the highest fatigue life. Moreover, the effect of the test setup on fatigue life is investigated. The results show a considerable effect of specimen configuration and test setup on the fatigue life of UD composites. The results of this study assist reliable fatigue tests.