A Device for Mechanically Folding Yarns and Woven Fabrics of Ballistic Fibers

A device was designed and built that attaches to servohydraulic machines that typically perform material fatigue testing. The device was designed to systematically fold woven fabric and yarns of ballistic fibers to assess the impact of mechanical folding, such as may occur during use, on ballistic fiber properties. Initial tests indicate that the device repeatedly folds a piece of woven fabric at the same location. However, when the device is in the open position, a consistent 1 cm movement of the fabric was observed. A slight modification of the device is required to eliminate this movement. After cycling a piece of woven poly(benzoxazole) (PBO) fabric for 5500 cycles, an 18% reduction in the ultimate tensile strength and strain to failure of the PBO fibers was observed. Research is continuing to determine a relevant and optimized testing protocol.