| Abstract: |
Poly (p-phenylene benzobisoxazole) (PBO) fibers have been used in soft body armor (SBA) because of their high mechanical strength. However, there was an unexpected failure of a first responder’s SBA which was composed of PBO fiber that was in service for only a few months. As folding during use may be a possible reason for mechanical property degradation, the effects of folding on the mechanical properties and structures of PBO and poly (p-phenylene terephthalamide) (PPTA) fibers were investigated. PBO fibers showed significant mechanical property degradation whereas PPTA fibers effectively maintained their mechanical strength. Structural changes in PBO fibers were detected using the small angle x-ray scattering (SAXS) technique. Reinforcing the results from SAXS, confocal microscopy showed extensive kink banding in the PBO fibers but no signs of internal damage in the PPTA fibers. Interestingly, no surface damage was seen in either PBO or PPTA fibers when they were examined using environmental scanning electron microscopy. |
