Evaluation of the effect of the ballistic damaged area on the residual impact strength and tensile stiffness of glass-fabric composite materials

The mechanical performance of a resin matrix composite after suffering ballistic impact is analyzed. The residual values of the impact strength and tensile modulus were determined as a function of the delaminated area produced by the ballistic impacts. The delaminated areas were measured by digital image analysis, and the implemented procedure used is outlined. The results obtained show that the delaminated area does not have any relevant influence on the tensile stiffness, but shows an important effect on the residual impact strength of the composite. A threshold value of around 50% was determined for the delaminated area using an S-shaped saturation function. Above this figure, the impact mechanical performance of the composite is seriously compromised and the residual impact energy level presents a significant reduction.