In-plane impact behavior of 3D-printed auxetic stainless honeycombs.

• Auxetic energy absorption structures with re-entrant configurations manufactured by 3D-printed superior elastic-plastic stainless steel. • High speed drop hammer impact tests conducted under varying input impact energies. • Comparison results with a convex honeycomb structure indicate excellent energy absorption performance of auxetic specimens. • Different crushing modes verified for the auxetic specimens with different impact energies and side length-to-thickness ratios. • The side length-to-thickness ratio was found to have a significant effect on the anti-impact performance of auxetic specimens. In order to fully comprehend dynamic responses of metallic auxetic honeycombs, drop hammer impact tests and corresponding finite element (FE) analyses were conducted. The three-dimensional (3D) printing technology was adopted to manufacture stainless steel specimens with varying cell side length-to-thickness ratios and cell configurations. The specimens were crushed under three distinct energy inputs, and the deforming process and relevant mechanical parameters, e.g., the Poisson's ratio, failure mode, plateau stress and energy absorption capacity were studied. The FE results can generally compare well with the experimental ones and facilitate clarifying the impact mechanisms of the experimental results. Improvements of the auxetic specimens in energy absorption were verified through comparison with that of the corresponding convex honeycomb. The results reveal that the specimen with an auxetic honeycomb has higher plateau stress and specific energy absorption with less deformation when the geometric size is the same. A small side length-to-thickness ratio and input impact energy can lead to greatly improved energy absorption efficiency. [ABSTRACT FROM AUTHOR]