Computational methods for predicting impact damage in composite structures

This paper describes recent progress in materials modelling and numerical simulation of the impact response of fibre-reinforced composite structures. A continuum damage-mechanics (CDM) model for fabric-reinforced composites is developed as a framework within which both in-ply and delamination failure may be modelled during impact loading. Damage-development equations are derived and appropriate materials parameters determined from experiments. The CDM model for in-plane failure has been implemented in a commercial explicit finite element (FE) code, and new techniques are used to model the laminate as a stack of shell elements tied by contact interface conditions. This approach allows the interlaminar layers to be modelled and strength reduction due to delamination to be represented; it also provides a computationally efficient method for the analysis of large-scale structural parts. The code is applied to predict the response of carbon-fabric-reinforced epoxy plates impacted at different velocities by a steel impactor. A comparison of structural response and failure modes from numerical simulations and impact tests is given which shows a good agreement for the prediction of delamination damage at low impact energies and fracture and penetration at higher impact energies.