A mechanical model for delamination growth under cyclic compression

The paper illustrates a mechanical model for describing the fatigue-driven, mixed-mode delamination growth fostered by local instability phenomena in composite laminates subjected to cyclic compressive loads. The laminate is modelled as the union of two sublaminates partly bonded together by an elastic interface, in turn, represented by a continuous array of linear elastic springs acting in directions normal and tangential to the interface plane. The model allows for determining the explicit expressions for the normal and tangential interlaminar stresses exerted between the sublaminates at the delamination front, as well as their peak values. It thus enables evaluating the individual contributions of modes I and II to the potential energy release rate as well as the value of the mode-mixity angle. Based on the results obtained, a mode-dependent fatigue growth law can then be applied to take into account the simultaneous actions of the two different crack propagation modes. Thus, for any load level, predictions can be made on the number of cycles needed for a delamination to extend to a given length. The results shed light on the mechanisms underlying some very insidious failures and seem able to help explain some experimentally observed phenomena of delamination growth and arrest.