Elevated shock resistance of all-metallic sandwich beams with honeycomb-supported corrugated cores

Abstract

Sandwich structures with cellular cores are favored in shock resistance, due mainly to advantages in fluid-structure interaction, energy absorption via core compression, and overall bending strength. To further enhance the shock resistance, this study proposes lightweight sandwich beams with honeycomb-supported corrugated cores. Firstly, dynamic responses of fully-clamped sandwich beams with such honeycomb-corrugation hybrid cores, including deformation/failure modes and beam deflections, were experimentally measured under simulated shock loading via foam projectile impact, and were compared with those of corresponding corrugated sandwich beams without honeycomb insertions. Secondly, the finite elements (FE) method was used to simulate the shock experiment. FE simulation results were validated against experimental measurements, with good agreement achieved. Subsequently, the FE model was employed to explore further how impact velocity, relative density of honeycomb, and honeycomb orientation in hybrid core affect beam deflection, and to reveal the underlying physical mechanisms. It was demonstrated that combining honeycombs with folded plates (corrugations) to create a hybrid core for sandwich construction led to significant enhancement in shock resistance, especially at relatively low projectile momentum where more than 50% enhancement could be achieved. Such superiority of the hybrid-cored sandwich beam was mainly attributed to its high specific compressive/shear strength as a result of the beneficial interaction effect between honeycomb insertions and folded plates, thus enabling smaller core crushing/deformation and higher bending strength of the impulsively loaded sandwich beam. At sufficiently high impact momentum, however, the interaction effect vanished as deformation of the fully-clamped sandwich beam is now dominated by stretching rather than bending.