THE BALLISTIC IMPACT CHARACTERISTICS OF ARAMID FABRICS - THE INFLUENCE OF INTERFACE FRICTION

This study reports the effect of the surface friction characteristics of aramid fabrics with respect to their static deformation behaviour and their ballistic capture performance. Various fabric weaves were studied and differing levels of interfibre-interyarn friction within the fabrics were achieved by the removal (Soxhlet extraction) or the addition (polydimethyl-siloxane treatment) of surface lubricants. Simple interyarn friction measurements have been performed, as well as fabric penetration studies, both quasi-statistically and under high speed ballistic conditions. A simple thin elastic plate model was found to described adequately the quasi-static response of the fabrics to a normal indentation deformation. A simulation of the ballistic deformation process in fabrics was devised on the basis of this first-order model of the quasi static indentation process. The predictions of the relative fabric ballistic captive performance, derived from this model, were found to be in reasonable agreement with the results obtained directly from the ballistic studies. The investigation has also shown that the interface frictional work dissipated at the filament-filament and yam-yam junctions is a critical factor in determining the static tensile yarn and (transverse) fabric stiffness. The changes in these static parameters is considered to be the origin of the subtle changes observed in the ballistic performance of the corresponding fabrics.