Characterisation of the edge crack torsion (ECT) test for the measurement of the mode III interlaminar fracture toughness

An experimental and numerical investigation were carried out on a glass/epoxy laminate to evaluate the edge crack torsion (ECT) test to determine its suitability for inducing mode III delamination growth. Two fixtures were used: an original and a modified ECT test which differ from each other in the constraints.The finite element analysis of the original ECT specimens without constraints in the guide pins showed that the propagation of mode III appears in the middle of the sample away from both ends, while with constraints, the propagation in mode III appears in the side of the loading point. For the modified ECT specimens with constraints the mode III distribution is similar to that occurring in the original ECT specimens without constrains.A C’scan analysis of the original and modified ECT specimens showed that delamination grows near the loading point for a load just after initial delamination.