Experimental investigation on mean crushing stress characterization of carbon–epoxy plies under compressive crushing mode

A challenge in numerical simulation of crashworthiness study is to be able to predict the crush damage modes, their evolution during crushing and the energy absorption in any composite structure from elementary material characterisation data. Therefore, it is important to know the behavior of one ply subjected to crushing load, and especially to determine the mean crushing stress that could be used for simulation. For that purpose, quasi-static crushing tests are performed for different configurations of two CFRP materials, UD and fabrics to determine the mean crushing stress of plies alone and inside a laminate. This study shows there is a linear relationship between crushing load and the contact surface of the plies being crushed on a metallic base which enables actually to define a mean crushing stress for a ply. The method to calculate this value is presented in this paper, based on image analysis of specific crushing tests. Experimental results show that for the UD material, the mean crushing stresses in 0° and 90° plies are very close. The value for a balanced fabric is also similar, approximately 270 MPa.