Yarn Pull-Out as a Mechanism for Dissipation of Ballistic Impact Energy in Kevlar KM-2 Fabric, Part I: Quasi-Static Characterization of Yarn Pull-Out

Report No. ARL-CR-537
Authors: Keith M. Kirkwood, John E. Kirkwood, Young Sil Lee, Ronald G. Egres, Jr., Eric D. Wetzel, and Norman J. Wagner
Date/Pages: May 2004; 32 pages
Abstract: 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 forcedisplacement 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.
Distribution: Approved for public release
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Last Update / Reviewed: May 1, 2004