An Analysis of the System Effects in Woven Fabrics under Ballistic Impact

Following a brief review of prior work on fabric-based armor systems, the system effects that occur during the ballistic impact of woven fabric body armor materials are discussed from a conceptual framework developed to relate single yarn impact mechanics to fabric impact mechanics. The consequence of assembling yarns into single-ply fabric structures is discussed from this perspective. A steep strain gradient along yarns in the region of the transverse deflection of the fabric is related to the constraint imposed on them by neighboring yarns. Striking and residual velocity data, collected for single-ply fabric systems of Spectra®, Kevlar® 29, and nylon with various different yarn deniers and weave types, are used to establish the response of spaced armor systems. The system effects of assembling fabric plies into body armor systems are determined by comparing the response of spaced armor systems to actual multiple-ply systems. There is a pronounced decrease in energy absorption capacity for the Spectra and nylon systems; this deleterious effect is ascribed to increased transverse stresses and possible interference of the deflection characteristics of fabric plies by subsequent plies.