Influence of boundary conditions and impact velocity on the ballistic behavior of aramid fabrics

This paper explores the ballistic impact behavior of a 1/1 fabric composed of aramid yarns using numerical simulations in ANSYS Explicit Dynamics. The main objective is to analyze the influence of boundary conditions applied to the yarns and the impact velocity on the structural response of the material under the action of a 9 mm FMJ (Full Metal Jacket) projectile. The fabric is modeled at the meso scale, where the structure of the yarn fabric is represented explicitly, without detailing the individual filaments in the composition of each yarn. The yarns are defined as elastoplastic materials with bilinear isotropic behavior, using parameters obtained from the literature for Kevlar or Twaron aramid fibers. Four fastening scenarios were analyzed: four-edge fastening, two-edge fastening by blocking the transverse faces of the yarns, and fastening applied over a length of 1.5 mm at the ends of the yarns. Five impact speeds were investigated: 430 m/s (according to the NIJ standard), 330 m/s, 320 m/s, 220 m/s, and 120 m/s. The results obtained include the maximum deformation of the fabric, the distribution of stresses, and the analysis of projectile penetration. The simulations indicate a clear correlation between impact velocity, fastening type, and the fabric's ability to dissipate energy and resist penetration. The study contributes to the understanding of the protective mechanisms of ballistic textiles and supports the development of more effective configurations. The results obtained are validated with papers from the specialized literature.