Research on the progressive damage model and trigger geometry of composite waved beam to improve crashworthiness

A nonlinear progressive damage model is proposed to predict the failure response of composite waved beam subjected to quasi-static axial crushing. To predict the failure model, both of the intra-laminar failure and delamination are considered. Based on continuum damage mechanics(CDM), the in-plane damage initiation is modeled with the maximum-stress failure criterion. To simulate the failed material, a stiffness degradation method combined with exponential damage evolution laws is adopted. A fracture-energy approach in conjunction with the characteristic element length is chosen to predict the damage evolution. The delamination initiation is given by a quadratic nominal-stress criterion. Considering the progressive delamination failure process, a cohesive stiffness degradation method and an exponential softening law based on a mix-mode fracture criterion are presented to predict the delamination propagation. To achieve better crashworthiness of composite waved beam, the wedge-trigger, two types of W-triggers and bevel-triggers with hybrid angles are proposed. Additionally, effect of the angle of chamfer-trigger on crashworthiness is investigated. Numerical results show that predictions correlate well with experimental results. Moreover, the present damage model can accurately capture intra-laminar and inter-laminar failure mechanisms. The proposed bevel-triggers perform significant effect in decreasing the peak load, and angles of chamfer-trigger make little difference in the crashworthiness.