Even though delamination is generally acknowledged as one of the main damage mechanisms in ballistically impacted laminates, information on the evolution of delaminations under ballistic conditions is scarce. The research presented in this thesis focuses on the deformation response of materials used in ballistic helmets, for which the impact of the delaminated backplane with the head is considered to be a possible cause of skull fracture and underlying brain damage.

A numerical model was developed as part of this research to gain insight into the parameters governing the penetration and deformation response of laminated composites subjected to ballistic impact. The effects of the various model parameters on the predicted ballistic response were evaluated extensively. Both instantaneous and post-failure approaches were used. It was found that the use of a post-failure approach led to a more realistic and numerically more stable response than when an instantaneous failure model was used. The through-thickness shear properties used in the numerical model were found to have a large effect on the predicted ballistic response.

A number of ballistic impact tests on woven laminated Kevlar-29 composite panels were performed to evaluate the accuracy and limitations of the numerical model. Different types of projectiles with a range of impact velocities were used. The initial quasi-static material properties for the numerical model, obtained from the literature, were “calibrated” for one specific impact condition to obtain close agreement between simulations and measurements. The “calibrated” numerical material properties were then held constant in simulations of the other ballistic impact tests.

For the panels impacted by the four types of projectiles considered in this study, the model predicted the measured maximum backplane displacement accurately. Comparing the measured and predicted responses for all projectiles used in this study, it was found that the maximum backplane displacement increased nearly linearly with increased impact energy, at least within the range of impact energies used in this thesis.