Comparison Between Numerical and Experimental Results on Ballistic Strength of Multi-layer Fabric Body Armors

In this paper, a fiber level micromechanics model is utilized to simulate real scale ballistic tests against multi-layer fabric soft body armors. The bottle-neck obstacle for micro-scale simulation of real scale ballistic tests of fabric body armors is computer capacity limitation. In order to improve efficiency, hybrid digital element meshes are adopted. Two hybrid element mesh concepts are investigated. The first concept is similar to the concept employed in the finite element approach, called the area based hybrid mesh concept. In its application, yarns are discretized into fine digital fibers in the vicinity of the ballistic impact center and into coarse digital fibers in regions far from the impact center. The second hybrid mesh concept is called the yarn based hybrid mesh. In its application, only principal yarns and yarns near principal yarns are discretized into fine digital fibers because high stress only develops within principal yarns after ballistic impact. Other yarns are discretized into coarse digital fibers. Numerical results evidence the yarn based hybrid mesh as being much more efficient than the area based hybrid mesh. Because only a few principal yarns resist load in a typical ballistic impact, the yarn based hybrid mesh technique could improve simulation efficiency up to 90-95% without sacrificing accuracy. This would enable simulation of the perforation process of real scale body armor using a fiber level micromechanics model. In this investigation, the yarn based mesh is applied to simulate real scale ballistic tests of soft body armor systems composed of 4 to 28 piles of 2-D plain woven fabrics. Ballistic limits, V50, derived by numerical simulations are compared to real scale standard ballistic results.