A numerical code has been developed to model ballistic impact into a multilayered,nonwoven composite thin plate. The target consists of N unidirectional layersthat are arranged in an alternating, cross-plied configuration. The projectile is either ahard sphere or a right circular cylinder (RCC). Motivation for such a model is thecommercial development of soft and plate-like body armor whose building blocks arethin, nonwoven ultrahigh molecular weight (UHMWPE) fibrous sheets consisting offour bonded unidirectional layers with alternating (0o/90o/0o/90o) orientations. Thematrix is typically a very flexible polyurethane just sufficient to fill the voids betweenthe fibers, so about 17 percent by mass. Our interest is in modeling various featuresseen in ballistic impact into such structures. The code, which was written in MATLABand runs on a PC, involves a forward, finite-difference (FD) scheme of numericalsolution. Layers are sub-divided into multiple elastic ‘yarn’ elements with distributedmasses. Elastic and viscous compression (normal) and shear (transverse) elements areused to model inter-layer yarn couplings. Sliding on the projectile follows a viscousfriction law. Following impact, the evolution of tension and transverse waves in thelayers are modeled, as well as projectile deceleration. Graphical results are presentedfor velocities, displacements, forces and strains versus time, which we interpret.
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