Finite element analysis of low-velocity impact damage in composite laminates

This paper investigates the low-velocity impact behaviour and impact-induced damages in graphite/epoxy composite laminates. A three-dimensional finite element and transient dynamic analysis is performed to calculate the time-varying displacements, forces, strains and stresses throughout the laminate resulting from transverse impact. A layered version of an eight-noded isoparametric brick element with incompatible modes is used to model the laminate. Transient dynamic equilibrium equation is integrated step-by-step with respect to time using Newmark direct time integration method. Modified Hertzian contact law is used to model the local contact behaviour. Appropriate three-dimensional failure criteria are used for predicting the occurrence of matrix cracking and the extent of delamination after impact.