Understanding the Influence of Boundary Condition and Crack Spacing on Impact Analysis of Composite Laminates

This study investigates the combined effects of boundary compliance and progressive damage evolution on the low-velocity impact response of composite laminates. A numerical model validated against experimental data was used to compare rigid and compliant boundary conditions across varying length-to-thickness ratios. The results show that for slender laminates, boundary compliance significantly influences the force–displacement response, leading to over-predicted stiffness and peak force when rigid supports are assumed, especially in thinner laminates, while thicker laminates remain largely unaffected. To understand the sequence of damage mechanisms during impact, the laminate response was studies in five distinct stages: undamaged laminate bending stiffness, damage laminate stiffness, delamination load drop, post load drop stiffness loss, and unloading. Both in-plane cracks and delamination damage modes were modeled using zero thickness cohesive elements. Adjusting the maximum allowable degradation in cohesive elements proved essential for accurately reproducing the experimentally observed load drop. The crack sensitivity study showed that a finer crack density is able to capture more complex damage interactions however it affects the force-displacement curve. The results emphasize that both boundary compliance and damage modeling are critical for achieving realistic numerical predictions of the impact response and damage morphology in composite laminates.