Numerical study on debris cloud and channeling effect of honeycomb sandwich shields under hypervelocity impact

In this study, the finite element and smoothed-particle hydrodynamics adaptive method was used to reproduce experiments on honeycomb sandwich shields impacted by spherical projectiles at hypervelocities, which can provide phenomena that are difficult to observe experimentally. The simulation results clearly reproduced the formation, development, and stabilization processes of the debris cloud as well as the damage and response processes of the honeycomb sandwich shield. The petal-shaped multicellular internal structure of the debris cloud was proposed by combining the formation and development of the debris cloud with its experimentally observed morphology. The damage and response processes of the honeycomb sandwich shield can be divided into two stages, namely, the crushing and inertial motion stages, to elaborate the varying failure modes of the honeycomb sandwich shield in different stages. The crushing stage represents the response of the material, whose failure modes include penetration, bending, buckling, tensile fracture, and compression failure. The inertial motion stage represents the structural response (bending and buckling of foils), which, at different positions, leads to folding and compaction of the honeycomb core layer by layer along the radial direction. The factors influencing the channeling effect were investigated, and the influences of the projectile diameter and impact position on the channeling effect and protection performance of the honeycomb sandwich shield were analyzed. The envelope analysis method for damage areas, which can predict the damage to the honeycomb core and rear plate at any impact position using an envelope diagram, was proposed. It was shown that the foil at different positions works by blocking or partitioning, which seriously affects the channeling effect. This study provides new ideas for optimizing the design of Whipple shields.