A synchronised blast wave and fragment impact test: a novel approach for evaluating aramid fabric performance against explosions

This paper discusses the development of a consistent and controllable test method for evaluating the response of materials and structures to combined blast wave and fragment impact. The experimental setup enables the synchronised arrival of a planar blast wave and a single fragment impact, with both loads controlled independently. An explosive-driven shock tube used to generate repeatable blast loads is combined with a weapon system accelerating a 1.102 g NATO STANAG Fragment Simulating Projectile. The two loads are synchronised to simulate an explosive event corresponding to a specific charge and stand-off distance from a target. The method is demonstrated on aramid fabrics to evaluate their fragment-impact resistance in the presence of a blast wave. A total of 55 samples, 15 layers each, are tested across a range of overpressures (4–10 MPa), fragment velocities (396–637m/s), and time intervals between the arrival of the blast wave and the fragment (–210 to +516 μs). The results are compared to reference single impact tests on 23 samples. Initially, the blast wave accelerates the fabric while stress waves propagate from its edges towards the centre point. At short time intervals an impacting fragment requires 18% higher impact velocity in order to perforate when compared to ballistic single-impact tests, as the fragment’s relative impact velocity is reduced. At longer time intervals, the blast wave-loaded fabric reaches its maximum out-of-plane displacement which increases the accumulated strain energy and reduces the fabric’s impact resistance by 14.5%.