MECHANICS OF TRANSPARENT POLYMERIC MATERIAL ASSEMBLIES UNDER PROJECTILE IMPACT: SIMULATIONS AND EXPERIMENTS

Abstract

Abstract : Polymeric materials exhibit a wide range in all aspects of mechanical behavior including elastic stiffness, yield stress, crazing versus yielding, post-yield deformation, and failure mechanisms. Recent developments to further manipulate the microstructure of polymers by the incorporation of nanoscale particles further expand the ability to tailor mechanical behavior. Exploitation of the differences in mechanical response of different polymers provides the potential to design multiscale heterogeneous material assemblies that provide dramatic enhancements in energy absorption of projectile impacts while maintaining the light weight of the homopolymer. This paper presents recent research conducted at the MIT Institute for Soldier Nanotechnologies on a study of the high rate deformation and projectile impact behavior of two amorphous polymers which exhibit significantly contrasting deformation and failure behavior: polycarbonate (PC) and polymethylmethacrylate (PMMA). Projectile impact tests were conducted on 6.35 mm thickness plates using a single stage gas-gun. Small (1.4 gm) round-nosed projectiles (5.46 mm diameter) made of 4340 AISI steel were projected into the polymeric plates at velocities ranging from 300 to 550 m/s. High-speed photography was used to visualize the sequence of dynamic deformation and failure events.