A Finite Element Study on the Effects of Toughness and Permanent Out-of-plane Deformation on Post- Impact Compressive Strength

This study uses observations of mechanisms from previous work (the “undamaged cone”, toughness and extent of permanent out-of-plane deformation) to examine parametrically their effects on residual compression after impact (CAI) strength using finite element models. In previous experimental work, tougher material systems exhibited up to 30% greater CAI strength for a given damage area. Based on this, it is desirable to understand what other parameters, beyond damage area, contribute to the CAI strength. Finite element models were implemented in ABAQUS explicit. Delamination growth was modelled using the virtual crack closure technique (VCCT). This study found that systems containing an undamaged cone exhibited an increased load prior to buckling, resulting in lower 0° peak compressive stresses and lower strain energy release rates forming at the outer edges of the delamination zone. In certain configurations, delamination growth into the undamaged cone occurred and was shown to affect negatively the post-buckled response. Overall, the effects of both toughness and permanent out-of-plane deformation was shown to affect CAI failure load by up to ~50% for a given damage diameter. It is also apparent that toughness played a more significant influence than the extent of permanent out-of-plane deformation.