Role of Inelastic Transverse Compressive Behavior on Kevlar KM2 Single Fiber Transverse Impact

摘要

Kevlar® KM2 fibers used in high velocity impact applications exhibits a nonlinearinelastic behavior in transverse compression with an elastic limit less than 1.5% strain.The effect of this transverse behavior on a single KM2 fiber subjected to a cylindricaland a fragment-simulating projectile (FSP) transverse impact is studied with a 3Dfinite element model. The inelastic behavior results in a significant reduction of fiberbounce velocity and projectile-fiber contact forces by 40% compared to an elasticbehavior. The inelastic dissipation and reduced bounce leads to an inelastic collisionrather an elastic collision. The fiber experiences multi-axial stress states during impactincluding transverse compression, axial tension, axial compression and interlaminarshear at the location of failure. In addition, for a FSP impact, significant multi-axialstrain concentrations are predicted. Thus, the experimentally measured yarn breakingspeeds are lower than classical Smith theory and may be attributed to the multi-axialloading stress concentration and property degradation mechanisms.