Experimental investigation of the damage propagation in composite specimens under biaxial loading

This paper deals with biaxial testing of flat specimens made of graphite–epoxy. Using a dual actuator hydraulic testing machine, combinations of axial and transverse loading are applied to the specimens. The corresponding strain fields are determined from digital image correlation. Two test series were performed with two different graphite–epoxy materials. Half of the specimens were manufactured containing artificial delaminations for the purpose of evaluating the effect of the reduction in the resistance given by the out-of-plane displacements, and of investigating the damage propagation. The results of this study can be used to improve the understanding of the different failure modes of composite structures, and to guide the development of finite element models able to predict their failure mechanism.