A semi-analytical model for failure analysis of delaminated composites under fatigue loading

Relative to static conditions, fatigue damage prediction of delaminated composites is widely recognized as a much more challenging problem, due to the gradually considerable reduction of mechanical characteristics and the delamination propagation, which further leads to catastrophic failure of laminates. To completely evaluate failure behaviors of delaminated composites under fatigue loadings, a semi-analytical model was established based on the residual stiffness theory and brittle damage mechanics. A stiffness degradation model was presented to describe the reduction of stiffness properties of composites, a residual strength model was found to predict the delamination propagation and strength degradation during cyclic loadings, and a failure evaluation criterion was proposed to judge the ultimate fatigue failure of laminates. Stiffness degradation tests and compressive fatigue tests were designed and conducted. Predicted results were highly consistent with experimental outcomes, which validated the effectiveness and accuracy of the semi-analytical model for the evaluation of fatigue failure behaviors of delaminated composites. Based on the proposed model, the strength degradation processes of delaminated composites in this work can be determined, and a safety load region can be additionally presented, which can provide significant guidance for the safety design of delaminated composites under fatigue loadings.

Automated summary

Compared to static conditions, predicting fatigue damage of delaminated composites is more challenging due to the gradual reduction in mechanical characteristics and delamination propagation, leading to catastrophic failure. A semi-analytical model was developed based on residual stiffness theory and brittle damage mechanics to evaluate failure behaviors of delaminated composites under fatigue loadings. The model included a stiffness degradation model, a residual strength model, and a failure evaluation criterion. Experimental tests validated the effectiveness and accuracy of the model. The proposed model provides important guidance for the safety design of delaminated composites under fatigue loadings.