Influence of layer number and air gap on the ballistic performance of multi-layered targets subjected to high velocity impact by copper EFP

Ballistic performance of monolithic and multi-layered steel targets penetrated by EFP is investigated both experimentally and numerically. Terminal effects of multi-layered targets are summarized to assess the pros and cons of composite structures from a macro perspective. Correspondingly, morphology features of fracture surfaces and microstructure evolution of the craters are analyzed to reveal failure mechanisms of sub-structures. The results show that the monolithic target presents less effective than in-contact or spacing multi-layered targets as the dominant response of multi-layered targets is global plastic deformation and bulging which involved bending and stretching behavior. When the number of layers grows, the local plastic deformation increases rapidly and may lead to the failure of multi-layered targets. Moreover, the air gap increases the ballistic resistance of multi-layered targets especially as the width of air gap is larger than half length of projectile.