Interface plasticity and delamination onset prediction

The authors carry out tensile tests on composite multi-layers that display a sliding at the interfaces between layers before delamination detection. At delamination onset, the sliding value at the free edges is almost the same for all of the tested laminates. A delamination criterion involving the measured critical sliding value is then adopted for predicting delamination onset in the tested laminates. A multi-particle model which takes into account the interface sliding is used for evaluating the interfacial stresses. The model equations are determined by means of the Hellinger–Reissner variational formulation in which the sliding is supposed to be a state variable of the system. For a given tensile load, the sliding is then determined by using a plasticity criterion (herein two criteria are studied) and a normal flow rule. The comparison of the theoretical calculations with the experimental data proves that delamination is predicted accurately and that the interface sliding is evaluated correctly.