Fracture morphology and deformation characteristics of repeatedly impacted thermoplastic matrix composites

Deformations of thermoplastic matrix composites during impact fatigue loading were investigated by instrumented impacts tester and scanning electron and optic microscopy (SEM). Curves of damage evolution against the number of repeated impacts to fracture the composites revealed three distinct zones: fibre micro buckling and shear fracture of fibres (1st region), initiation and propagation of delaminations and matrix deformations (2nd region), propagation of delaminations and fibre cracking and pull out especially in tensile area (3rd region). Intensive deformations observed primarily in compression region during impact-fatigue loading can be explained by lower compressive strength of composites compared to their tensile strength.