An improved model of fatigue life for stitched carbon fiber composites considering stiffness degradation

摘要

In industrial production, carbon fiber composite laminates are stitched to improve the delamination resistance of materials. In the service process of parts, fatigue damage caused by cyclic load is one of the important reasons for failure of parts. How to predict the fatigue life of stitched composites simply, efficiently and accurately is the focus of research. In this paper, the residual stiffness model of stitched composites is established by introducing the concept of fatigue stiffness and stitching strengthening coefficient. The fatigue life of unstitched carbon fiber composites under complex cyclic stress is predicted by using the tensile fatigue properties of unstitched carbon fiber composites. The tensile fatigue test and three-point bending fatigue test of unstitched T300 carbon fiber composite are carried out, and the fatigue life of the same kind of carbon fiber composite is estimated according to the proposed model. The reliability of the proposed model is verified by comparing the calculated results with the experimental data. The analysis shows that the proposed model could well predict the fatigue life of the same kind of composites after suturing by using the fatigue properties of the unstitched carbon fiber composites. The fatigue stiffness model based on suture strengthening coefficient can effectively predict the fatigue life of suture laminates, which provides a theoretical analysis method for the life prediction of suture composite materials.