The effects of off-axis transverse deflection loading on the failure strain of various high-performance fibers

Abstract

Single filaments are subjected to a transverse deflection loading environment in efforts to gain insight into the failure strain of soft-body armor systems experiencing transverse impact. The fiber types utilized for all such experiments are Kevlar® KM2, Spectra® 130d, Dyneema® SK62, Dyneema® SK76, and Zylon® 555. In order to understand the effect of indenter shape, three different indenter geometries are utilized, namely a 0.30 caliber rounded head, a 0.30 caliber fragment simulation projectile (FSP), and high-carbon steel razor blades. The angle at failure is also varied in order to evaluate the presence of a stress concentration developed around such indenters through angles that would be produced during the transverse impact of single fibers/yarns. Loading with the rounded indenter yields failure strain values similar to pure longitudinal tensile experiments. Fibers loaded via a razor blade show a drastic reduction in failure strain, although the demonstrated failure strains are reasonably similar for all tested angles. Most interestingly, fibers loaded with the FSP show a reduction in failure strain with increasing loading angles, with low angle and high angle failure strains being similar to failure strains of fibers loaded with the rounded indenter and razor blade, respectively. In efforts to gain further insight into the method of fiber failure due to different loading configurations, post-mortem fracture surfaces are imaged for Kevlar® KM2 and Dyneema® SK76.