Fatigue life of graphite/epoxy laminates subjected to tension-compression loadings

A recent two-parameter fatigue model, aimed at the prediction of the fatigu e behaviour of composite materials, was applied to fatigue results availabl e in the literature, concerning graphite/epoxy laminates subjected to tensi on-compression loadings. It was found that the model, successfully applied in the case of tension-tension and compression-compression fatigue, also wo rks when the sign of stress is reversed during fatigue. However, the consta nts appearing in the proposed formula must be evaluated anew when the loadi ng mode changes from pure tension to tension-compression. The probability o f failure in fatigue is predicted with reasonable accuracy by the model, wh ich is very conservative in calculating the residual strength after a given number of cycles.