An efficient approach for predicting low-velocity impact force and damage in composite laminates

An efficient approach is presented to predict the critical impact force and corresponding damage in composite laminates subjected to low-velocity impact. In developing such approach, stress analysis was conducted first for a 4 mm thick quasi-isotropic laminate to determine the potential failure modes and locations under the critical impact force. Three finite element models were subsequently built to simulate the damage in the upper, middle and lower interfaces and investigate the effect of each damage mode on the laminate stiffness. It is found that delamination adjacent to the impact point is suppressed by the high compressive through-thickness stress resulting in negligible reduction of the laminate stiffness. Both the delamination in interfaces adjacent to the mid-thickness plane and matrix fracture on the lower face can cause the first load drop, which corresponds to the critical impact force. The former is the main causative mechanism for the laminate studied in this paper. A simplified and efficient finite element model, which takes account of the delamination damage adjacent to the mid-thickness plane and the lower face, is developed that is computationally affordable and delivers acceptable prediction of the critical impact force, damage shape and size, by both quasi-static load and dynamic impact analyses.