Modelling the interaction between matrix cracking and delamination in carbon–epoxy laminates under low velocity impact

The use of interface finite elements and a damage model are proposed to predict damage due to low velocity impact in carbon–epoxy (04, 904)s laminates. Experimentally, some impact tests were performed using a drop weight testing machine and a damage characterisation was done using X-rays. Impact-induced delamination and matrix cracks were found to be the most detrimental damage modes in laminated composites. The numerical model developed is based on an interface finite element compatible with three-dimensional solid elements, which allows to model delamination between layers and matrix cracking inside layers. The damage model is based on the indirect use of fracture mechanics considering a softening stress-relative displacements equation and permits to simulate the initiation and propagation of damage avoiding the definition of initial flaws. The progressive damage model successfully simulated the interaction between the crack due to bending and delamination. Good agreement between experimental and numerical analysis for shape, orientation and size of the delamination was obtained.