Development of a failure criterion for kevlar fabrics under transverse indentation
Abstract
Kevlar fabrics are extensively used in ballistic protection applications. A primary area of research involves enhancing the performance of these fabrics while reducing the weight of the armor so as to ensure battlefield mobility. Silica nano-particle impregnated Kevlar fabrics exhibit significantly enhanced ballistic performance while retaining flexibility. Although individual yarns exhibit rate dependent, nonlinear elastic behavior in tension, the behavior of the fabric itself is complicated because of the interaction of the two distinct media of yarns. A homogenized continuum constitutive model for plain woven Kevlar fabrics was developed previously. Numerical simulations based on this model have yielded good agreement with experimental results. The present study investigates the response and failure of neat and nano-particle impregnated Kevlar fabric under transverse deformation. Static indentation tests were performed on neat and treated K706 (medium weave) Kevlar fabric. The combined deformation behavior of fabric with a deformable backing material was also examined. Compression tests were done to determine a suitable foundation material. The failure mechanisms were found to depend on multiple factors. Based on these observations, three failure modes – yarn breakage, yarn sliding and indentor slip-through – were identified. A stress based criterion to predict the failure for the uniaxial case was introduced. This criterion was implemented in numerical simulations in conjunction with the constitutive model via a UMAT subroutine in ABAQUS. A comparison of the experimental and simulated load-displacement.
Degree
M.S.E.
Advisors
Sun, Purdue University.
Subject Area
Mechanics|Aerospace engineering|Textile Research
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