Comparative Numerical Studies of the Mechanical Efficiency of Sandwich-panels with Different Non-/auxetic Prismatic and Lattice Cores Subjected to Ballistic Loading

Civil as well as military facilities, vehicles and applications must increasingly meet higher safety standards to ensure the highest possible protection against extraordinary stresses such as ballistic and/or air-blast loading. The use of lightweight sandwich constructions is considered an efficient and promising measure for enhancing passive safety and maintaining structural integrity. In addition to increased bending stiffness compared to monolithic plates of the same weight, they also exhibit a more favorable behavior under dynamic loading scenarios. The influence of open and closed auxetic core geometries on the relevant mechanical parameters under impact loads of spherical rigid projectiles (rsph = 15 mm, msph = 10 g) with velocities of 200 ms−¹ will be analyzed in the present study in order to be able to draw principal conclusions on the auxetic mechanisms and their effectiveness. A new performance indicator is suggested in this context. Numerical studies were performed using the commercial finite element code ABAQUS/Explicit. This included a validated material model for the aluminum alloy EN AW-7108 T6, which considers strain-rate dependent plastic material behavior and typical failure criteria. A comparison with a monolithic reference plate of the same mass and conventional non-auxetic core topologies allows a final efficiency assessment of the sandwich designs with a modified internal structure. The displacements of the rear face surfaces as well as the resulting stresses on supporting structures can be reduced by up to 90 percent and the plastically dissipated energy can be increased by up to 15 percent for some core variants.