The role of folding in the degradation of ballistic fibers

Abstract Research has indicated that the folding of ballistic fibers comprising soft body armor may be a factor in the performance deterioration that has been observed. To quantify the impact of this failure mechanism on body armor performance, an apparatus was designed and built to simulate the folding that may occur in the ballistic fibers while the vest is in use. This device systematically folds woven fabric and yarns of ballistic fibers to enable an assessment of the impact of folding on ballistic fiber properties. After cycling a piece of woven poly(benzoxazole) (PBO) fabric for 80,000 cycles, a 41% reduction in both the ultimate tensile strength and strain to failure of the PBO fibers was observed. These effects were also observable in data obtained from small angle x‐ray scattering (SAXS) where the long range order of the fiber structure is changed by the folding process. Preliminary failure analysis using scanning electron microscopy (SEM) on tested fibers also revealed changes in failure morphology. POLYM. COMPOS., 2010. Published 2010 by the Society of Plastics Engineers