Ballistic Penetration of Compressively Loaded Composite Plates

Abstract

The effects of ballistic penetration on woven E-glass fiber-reinforced epoxy laminates subjected simultaneously to in-plane compressive loading were investigated. A portable hydraulic press and fixture was designed to apply compressive preloads during ballistic penetration. A civilian version of the US Army ’s M4 carbine was used for the ballistic tests where penetration velocities were well above the ballistic limit for 5.56 mm projectiles. Compression-only data were initially obtained to characterize the various modes of damage. Samples without simultaneous compressive preload were subjected to ballistic penetration alone and then compressively loaded to failure. Finally, samples that had previously undergone ballistic testing at varying levels of compressive preloads were loaded in compression to determine the residual compressive failure strength. For simultaneous loading, samples were subjected to a specified compressive preload while a projectile was fired through the center of the sample. This study finds that the effect of simultaneous preload and ballistic penetration results in a greater extent of damage propagation than for ballistic penetration alone, increasing the possibility of initiating buckling failure of the loaded plate. The equivalent ballistic limit velocity for a given laminate and thickness is also likely to be reduced with increasing preload in composite laminates.