Underwater impulsive response of a metallic negative Poisson's ratio assembled composite structure

The traditional negative Poisson's ratio structures have the unique advantages of high shear strength and specific energy absorption, but they usually lack load-bearing units in the transverse direction, resulting in relatively weak load-bearing capacity during the large deformation stage. In this paper, two types of metallic negative Poisson's ratio assembled composite structures are designed by assembling re-entrant honeycomb cells and double-arrow cells with deflection: the re-entrant double-arrow assembled composite structure and the asymmetrical re-entrant double-arrow assembled composite structure. Single-layer and double-layer metallic NPR assembled composite structures were fabricated using bending-vacuum brazing technology. Meanwhile, an experimental method was used to study the deformation mechanism of assembled composite structures under underwater impulsive loading by utilizing flying plate to strike pistons in a water tank, thereby generating shock wave pulses similar to those produced by explosive detonations. The impact process was numerically simulated using the Euler-Lagrange coupled method, and the simulation results agreed well with the experimental data. The results show that the deformation of the assembled structure's back plate is significantly reduced compared to the conventional re-entrant hexagonal honeycomb. Moreover, foam filling of the assembled structure greatly enhances its impact resistance. The research findings can provide valuable insights for the design of novel protective structures.