MULTI-SCALE FINITE ELEMENT MODELING OF MULTI-PLY WOVEN FABRICS UNDER BALLISTIC IMPACTS
Abstract
High-strength fiber reinforced woven fabrics are broadly utilized for their high strength-to-weight ratios and good flexibility to provide ballistic protection in security applications such as soft body armor equipment or protective layering of military vehicles. Experimental, numerical and analytical studies have been conducted in literature to understand and improve the ballistic impact response of woven fabrics. Many of the existing studies dealt with the application of single-ply fabrics, though real-world applications of woven fabrics, such as soft body armor equipment, e.g., combat helmets or vests, consist of multi-ply fabrics.In this dissertation, a state-of-art finite element (FE) modeling technique (i.e., multi-scale FE modeling) is developed to create a FE model of woven fabrics that could be used for investigating ballistic impact responses of multi-ply fabrics. The multi-scale model (i.e., at meso- and macro-scales) created in this study improved the coupling between the interface of meso- and macro-scale regions without using contact definitions, resulting in improved propagation of ballistic shock wave between the two regions of different scales. The multi-scale FE model of a single-ply Kevlar woven fabric was first created and validated with experimental data on out-of-plane displacements of the fabric and residual velocities of the projectiles. The validated single-ply multi-scale model was then used to create a FE model of multi-ply fabrics that were subsequently validated using test data, on the projectile’s residual velocities.To study the effects of the total number of plies on the ballistic impact performance of multi-ply woven fabrics, the multi-scale FE models of three-, five-, seven-, and ten-ply woven fabrics were created. The ballistic limit velocities of the four multi-ply fabrics were first determined under impacts of a NATO specified 1.1 gr fragment simulating projectile. The V100 ballistic limit, energy transitions between the projectile and fabrics, displacements of the fabrics, and post-damage patterns of the four multi-ply fabrics were analyzed and discussed in detail. Finally, the multi-scale FE model of ten-ply woven fabric was used to study the effects of projectile characteristics on its ballistic responses. Six different projectiles, which were in two sizes (.22 and .30 cal.) and three nose shapes (flat, pointed, and spherical), were used to obtain the ballistic responses of the ten-ply woven fabric under impacts at the ballistic limit velocity for each projectile. Energy transitions, out-of-plane displacements, and post-damage patterns of the fabric were then evaluated in detail.