The Effect of Weaving on the Strength of Kevlar KM2 Single Fibers at Different Loading Rates
Final rept. Apr-Aug 2012
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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Understanding the mechanical behavior of woven Kevlar fibers at high loading rates is needed to develop material models that mathematically represent the deformation and failure for computer codes that are being developed or used to simulate high loading-rate events such as impact on fiber-based protective items. When fibers are woven into fabric, they may get damaged, thus reducing their strength. In order to understand the effect of weaving on the strength of Kevlar fabric, individual fibers from both the warp and weft directions must be studied. In this experimental study, the strengths of warp and weft fibers from plain-woven Kevlar KM2 fabric, as well as unwoven virgin fibers, are measured and compared to quantify any damage due to weaving. The fiber responses are evaluated at low, intermediate, and high strain rates, with 5-mm-gauge-length samples. Low- and intermediate-rate mechanical deformation experiments are conducted using the Bose ElectroForce test system, and the corresponding high-rate experiments are conducted using a split Hopkinson tension bar modified for fiber characterization. This report presents a comparison of strengths of woven fibers with that of unwoven fibers to determine the possible degradation of strength at different loading rates due to weaving.