Effect of projectile nose geometry on the critical velocity and failure of yarn subjected to transverse impact

Three different types of yarn have been subjected to transverse impact experiments in efforts to gain an understanding of local yarn failure and to provide input parameters for future transverse yarn impact simulations. DupontTM Kevlar (R) KM2, DSM Dyneema (R) SK76, and AuTx (R) from JSC Kamenskvolokno were selected as representative materials, as the former two are commonly implemented into bullet resistant panels and the latter is a promising material for future impact resistant fabrics. In order to assess the effect of projectile nose shape on the critical rupture velocity range for each yarn type, three missile geometries have been implemented, namely a 0.30 caliber rounded head, a 0.30 caliber chisel nosed fragment simulation projectile (FSP), and a high-carbon steel razor blade. As opposed to one single velocity wherein yarn behavior transitions from transverse wave development to immediate local failure, a range is defined wherein progressive filament failure is detected with increasing impact velocities. Such ranges are determined for all yarn types using the three projectile geometries yielding critical velocity transition regions of increasing value when impacting via razor blade, FSP, and round projectile heads, accordingly. In addition, post-mortem fracture surfaces recovered from impact experiments have been imaged so as to elucidate the mechanism of failure throughout the range of velocities tested for each projectile type and yarn material and said fracture surfaces correlate well with impact velocity and projectile nose geometry.