Fatigue Life of Graphite/epoxy Laminates Subjected to Tension- Compression Loadings

A recent two-parameter fatigue model, aimed at the prediction of the fatigue behaviour of composite materials, was applied to fatigue results available in the literature, concerning graphite/epoxy laminates subjected to tension-compression loadings. It was found that the model, successfully applied in the case of tension-tension and compression-compression fatigue, also works when the sign of stress is reversed during fatigue. However, the constants appearing in the proposed formula must be evaluated anew when the loading mode changes from pure tension to tension-compression. The probability of failure in fatigue is predicted with reasonable accuracy by the model, which is far conservative in calculating the residual strength after a given number of cycles.