Energy absorption and indentation resistance of re-entrant arched honeycomb reinforced by circular ribs

Abstract

Driven by the enhancement of mechanical properties while keeping controlled auxetic performance, hybrid design approach is employed to arched cell wall re-entrant honeycomb by incorporating circular reinforced ribs. This leads to the development of a novel circular reinforced re-entrant arched honeycomb (CRRAH) structure. CRRAH specimens were additively manufactured, and quasi-static compression tests were conducted to evaluate their performance. Results demonstrate that superior mechanical performance is presented by comparing to the conventional re-entrant arched honeycomb structures, including a remarkable 208% increase in specific energy absorption (SEA). The finite element model, validated against experimental results, was further used to explore the deformation mechanism and auxetic performance of CRRAH structures with varying thickness ratios (γ) between the walls of the reinforced circular ribs and the re-entrant edges. Results indicated that integrating circular rib within the re-entrant cells effectively restricts the continuous rotational stretching of inclined ligaments, resulting in a two-stage collapse process. This significantly enhances the deformation stability and energy absorption capacity. Moreover, adjusting the thickness ratio γ shifts the deformation mode from localized shear band formation to uniform global deformation with slight lateral expansion. When γ > 1, increasing the wall thickness of the reinforced circular ribs has little effect on improving SEA but significantly influences the dynamic Poisson’s ratio. Conversely, when γ < 1, increasing the wall thickness of reinforced circular ribs effectively enhances SEA, though it has only a minor effect on auxetic performance. In addition, the dynamic indentation behaviour of CRRAH structures under a spherical-ended indenter impacting was examined. The dependence of deformation and the indentation resistance performance on thickness ratio were explored and the underlying mechanism was revealed. These findings provide valuable insights into the design of advanced re-entrant honeycomb structures, combining improved crashworthiness with controlled auxetic effects.