Statistical analysis of PPTA fiber strengths measured under high strain rate condition

Single PPTA [poly(p-phenylene terephthalamide)] fiber tensile tests using a Kolsky bar were carried out to investigate the effect of the strain rate on their tensile strengths. Since single fiber tests yield distributions of strengths, a large sample size is needed to get statistically significant results. In this study a new fiber gripping method using direct clamping of a single fiber with PMMA [poly(methyl methacrylate)] plates is introduced to measure fiber strengths under high strain rate test conditions in a high-throughput manner. For comparison purposes, quasi-static tests using the same PMMA plates were also performed. PPTA fiber strengths measured under quasi-static test conditions with 5 mm and 60 mm gauge lengths exhibit length dependency confirmed by statistical analysis. In addition, statistical comparison of PPTA fiber strengths measured under quasi-static and high strain rate test conditions clearly show that this fiber’s strengths are rate-dependent. Furthermore, PPTA fiber strengths obtained by high strain rate tests increase with decreasing fiber diameter, while no such relation appears in quasi-static tests.