Mode III fracture of composite laminates with elastic couplings in edge ring crack torsion test

In this work, the distribution of the strain energy release rate (SERR) at the crack front of carbon fiber-reinforced polymer laminates with elastic coupling is analyzed using the edge ring crack torsion (ERCT) test configuration. The SERR at the delamination front is calculated by virtual crack closure technique (VCCT). Elastic coupling laminates, including bending-extension (BE) and bending-torsion (BT) ones with different stacking sequences are studied. The effect of two different loading boundary conditions on the SERR distribution of laminates is also investigated. The results demonstrate that the distribution of SERR is significantly affected by the elastic coupling and stacking sequence. In addition, elastic coupling introduces mode I and mode II components in the ERCT configuration. However, their contribution is negligible. In comparison to unidirectional laminates, better uniformity of SERR distribution can be obtained in the BE and BT laminates. Pure mode III fracture without non-uniformity is achievable by designing the elastic coupling of laminates. The obtained results can provide guidance for the standardization of the ERCT configuration used for the measurement of mode III fracture toughness.