Aramid fabric surface treatment and its impact on the mechanics of yarn’s frictional interaction

Aramid textiles are widely used in protective armor structures (vests, helmets, etc.). The most important problem of the development of such structures is to reduce the fraction of the bullet's kinetic energy transmitted to the object located behind the armor panel. The reduction of the kinetic energy results to decrease a dynamic deflection of the back surface of the armor panel. Researches show that a significant part of the energy absorbed by the armor panel is linked to frictional forces of pulled yarns. In this paper, we present an effective method for controlling of dry friction between yarns - surface treatment by PVA suspension, rosin or silicone grease with a slight overweighting of the fabric. In the experimental part of the paper, the results of quasi-static yarn pull-out tests from an aramid fabric SVM P110 with a plane structure (with different types of surface treatment) are presented. The relationships between force and displacement are also obtained. It can be noticed that the surface treatment of fabrics with addition of only 6 wt. % leads to increase frictional interaction between the yarns by 4 times. Elastic and strength properties of aramid yarns are obtained from quasi-static tensile tests. The dry friction coefficient between yarn and neat fabric is determined by experiments. The numerical part of the paper is devoted to development of low-parametric FE model of a yarn pull-out test for P110 fabric performed in explicit FE code LS-DYNA. It is shown that different surface treatment can be effectively substitute during calculations by variation of dry friction coefficient (and increase/decrease yarn pull-out force). The calculated “force -displacement” curves are obtained by pulling out a yarn from a fabric with and without surface treatments, which imposed within the corresponding scatter band of the experimental data.