Enhanced energy absorption of a novel skeletal-united tubular metamaterial exhibiting negative Poisson’s ratio

The study introduces a novel approach to balancing energy absorption (EA) and negative Poisson's ratio (NPR) in metamaterial design, which typically present desired properties and conflicting objectives. This is achieved by developing a skeletal-united tubular metamaterial (SUTM), created by splitting and reconstituting a central in-line skeleton within the unit structure of a traditional re-entrant tubular metamaterial (RETM). The innovation design from unit to tubular structure enables SUTM to achieve a compromise between high EA and improved NPR by leveraging the generated re-entrant skeleton. Experimental and numerical comparisons demonstrate that the SUTM outperforms the RETM in both EA and auxetic properties. Additionally, the tube adopts an uncommon out-plane configuration of metamaterials, so the study investigates the effects of various tubular geometric parameters, including tube thickness, diameter, and height, on EA and NPR. Furthermore, a series of SUTM variants are proposed and examined, highlighting the advantageous role of the skeleton generated from the corner of the unit cell in enhancing EA.