Equivalent protection factor of bi-layer ceramic metal structures

With increasing ballistic threat levels, there is ever more demand on developing ceramic armor designs with improved performance. This paper presents finite element simulations that investigate the performance of silicon carbide ceramic with steel 4340 backing material and titanium alloy, graphite as buffer layers when subjected to normal and oblique impacts by a tungsten alloy long rod projectile (LRP). Depth of penetration from experimental measurements is compared with simulations to confirm the validity of constitutive, failure model parameters. Titanium alloy cover plate and graphite interface weak layer laterally spread the impact shock away from the SiC tile and reduces the amplification of the stress accumulation at the front surface of the SiC tile. The dwelling time increases before it penetrates into ceramic armor. Further, using AUTODYN® numerical simulations detailed parametric study is carried out to identify the minimum areal density armor for a given ballistic limit velocity. The equivalent protection factor for the bi-layer armor is a simple function of the cosine of the angle of impact.