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Yarn pull-out can be an important energy absorption mechanism during the ballistic impact of woven Kevlar fabric. This study reports the effects of fabric length, number of yarns pulled, arrangement of yarns, and transverse tension on the force-displacement curves for yarn pull-out tests on Kevlar KM-2 fabric under laboratory conditions. A semi-empirical model is presented for predicting the yarn pull-out force and energy as a function of pull-out distance, including both yarn uncrimping and subsequent yarn translation. This model is found to replicate the experimental data to a high degree of accuracy, and should prove useful for understanding ballistic experiments and improving computational modeling of fabrics., The original document contains color images.

The energy absorbed in ballistic fabrics is modeled by assuming yarn pull-out including yarn uncrimping and translation as the primary energy absorption mechanisms. Using a semi-empirical model of yarn pull-out based on laboratory tests predictions for ballistic performance of fabrics are compared to ballistic test results. It is demonstrated that quasi-static pull-out results can be correlated quantitatively with yarn pull-out during ballistic impact.