Shock resistance of a bio-inspired double corrugated sandwich panel impacted by a graded cellular projectile

Abstract

Sandwich structures with a thin-walled core layer exhibit remarkable shock resistance, but most of them suffer from high initial peak stress, limiting their load mitigation ability. Inspired by the S-shaped corrugated wall of the cuttlefish bone and the herringbone corrugation of $Odontodactylus$ $syllabus$ dactyl, a sandwich panel with a bio-inspired double corrugated (BDC) core is proposed to enhance the shock resistance. Impact simulations and experiments using graded cellular projectiles were conducted to analyze the effects of core layer configuration on the shock resistance performance of the sandwich panels and to validate the necessity of well-designed graded cellular projectiles in simulating blast loads. It is found that compared to hexagonal honeycomb and bio-inspired single corrugated sandwich panels of the same density, the BDC sandwich panels exhibit superior shock resistance performance, with a reduction of 97.9% and 40.7% in maximum transmission stress and maximum deformation, and an increase of 38.0% in crushing force efficiency. The maximum transmission stress of the BDC sandwich panel is mitigated by the herringbone corrugations, and higher plateau stress is achieved. The underlying mechanism is that herringbone corrugations change the deformation mode, causing less plastic deformation at impact onset to attenuate peak stress, and later generating more wrinkles to increase plateau stress. A stable plateau stress and deformation during impact are guaranteed by the non-hermetic corrugated walls because they permit air to escape, avoiding strain hardening. The present findings provide a new inspiration and method for novel protective structure design and testing.