Damage characteristics of foamed aluminum/fiber sandwich structure under the combined loading of near-field blast shock wave and fragments

In the near-field explosion of improvised explosive device, the protective structure is often subjected to the combined action of blast wave and fragments. To improve the protection performance of the structure, a composite structural material containing foamed aluminum/fiber sandwich was designed and prepared. The explosion and penetration experiment was carried out to study the failure mode of the composite structure under the combined action of explosion shock wave and high-speed fragments. In the experiment, the time for the explosive shock wave to reach the surface of the composite plate and the pressure attenuation before and after passing through the material were tested by installing PVDF pressure gauges on the upper and lower surfaces of the composite plate. Meanwhile, the time for the shock wave to reach the surface of the composite plate was measured by piezoelectric probes for the purpose of verification. The time for fragments to reach the surface of the composite plate was tested using a comb-shaped target, and the velocity attenuation of fragments after penetrating the target plate was obtained. The influence of the two loading’s timing sequence of explosion shock wave and fragment on the failure mode was discussed, and the energy absorption mechanism of different materials was analyzed. The results show that the change of detonation distance directly affects the timing sequence of the action of explosion shock wave and fragment. In the conditions discussed in this paper, when the detonation distance is greater than 600 mm, the fragment acts before the shock wave. Under the combined action of shock wave and fragment, the aluminum plate is accompanied by local sag deformation in addition to the penetration failure of fragments. The cellular structure of foamed aluminum was crushed and deformed under the impact load. The fibers at the bullet hole are stretched and fractured under the penetration of fragments, and are accompanied by high temperature failure. Under the two sequential effects, the existence of bullet holes weakens the effect of shock wave on the front aluminum plate, and the deformation and damage degree of the later sandwich structural material and the rear aluminum plate are more serious than that of the previous material. This research provides a technical basis for the application and functional design of lightweight composite structural materials in the field of near-burst protection in limited space.