Fatigue life prediction for composite materials based on the S-N-φ model

The strength degradation law of composite materials is very important to fatigue life prediction. However, establishing existing residual strength models requires various experimental data to confirm the parameters involved in the models. Sometimes, experimental data on the residual strength of composite materials are not available because of limitations on experimental cost and project progress. To solve these issues, a new fatigue life prediction model named the S-N-φ model is proposed. The S-N-φ model does not require the experimental data of residual strength, and the residual strength is only reflected in the theoretical deduction process. The S-N-φ model can clearly explain the probability characteristic of fatigue life because both initial strength and cyclic stress are considered. The S-N-φ model is verified by a set of experimental data of composite laminates. The results show that the S-N-φ model is more accurate than the widely used classical S-N curve model, and the probability characteristic of fatigue life predicted by using the S-N-φ model agrees well with the experimental data.