Influence of fiber orientation on the ballistic performance of needlepunched nonwoven fabrics

The influence of the initial fiber orientation distribution on the ballistic performance of a needlepunched nonwoven polyethylene fabric was analyzed. To this end, ballistic tests were carried out in specimens pre-deformed along the machine or the transverse directions and the influence of pre-deformation on the fiber orientation was measured by means of wide angle X-ray diffraction. It was found that pre-deformation along the machine direction (the soft orientation of the fabric) led to more isotropic in-plane mechanical response and to a marked increase in the specific ballistic limit and in the energy dissipated by unit weight while the opposite behavior was found after stretching the fabric along the transverse direction. These differences were accompanied by changes in the penetration mechanics from extensive fiber pull-out to slippage between fibers in the network. These results highlight how the nature of the nonwoven microstructure (connectivity of the entanglement points and fiber orientation distribution) can be tailored to improve the impact performance.