A penetration model for semi-infinite composite targets

A penetration model for composites reinforced with high tenacity fibres like ultra-high molecular weight polyethylene (UHMW-PE) is proposed based on the modified Bernoulli theory typically used for metallic targets. The model describes penetration by tensile failure of the composite material through compression loading in an infinitely thick target and includes consideration for projectile deformation. The predicted projectile velocity and axial interface loads shows good agreement with numerical simulations for a deforming and rigid projectile condition against two grades of UHMW-PE composite. The model can also be used to predict transient projectile velocity and interface loads during the first phase of penetration (which acts over most of the penetration event) for a target of finite thickness. It was shown that transition to bulging occurs upon the arrival of the rarefaction wave, generated from the back of an unsupported target, at the projectile-target interface. The stress relief can lead to a change in penetration mode when the magnitude of release is sufficient to reduce the load at the interface below that of the target strength. This change in mode occurs late in the penetration event, and the model developed in this work is demonstrated to be valid up to this point.