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Influence of the impact velocity on the perforation resistance of a glass-reinforced polypropylene material

The perforation resistance of a thermoplastic woven composite material (Twintex-based) was experimentally investigated. First, the efficiency of the inversed perforation experiment conducted on a Hopkinson bar was used to measure accurately the strain-rate sensitivity at two perforation velocities (0.01 and 45 m/s). The results showed an increase in perforation maximum load and perforation energy. Then, direct tension experiments were performed to obtain the mechanical response and fracture force of the yarns at two different tension velocities 0.05 and 2000 mm/s. Low strain-rate sensitivity was measured and no modification in the fracture process was observed. On the contrary, the use of imaging techniques, from low to highest impact velocities reachable with the perforation experiments, showed that the fracture process was clearly modified from macrocracking at 0.01 mm/s to early fragmentation at 45 m/s, which may contribute to the strain-rate sensitivity of the strength of the material.