Experimental and finite element analysis of tubular auxetic structures with varying cross-sectional geometries

Tubular auxetic metamaterials are attractive for lightweight protection and energy absorption because their deformation can be regulated through structural design. However, the effects of different cross-sectional configurations on the compressive behavior of tubular auxetic lattices remain insufficiently compared within a unified framework. In this study, two tubular auxetic lattice metamaterials with square and circular cross sections, denoted as XATL and XATLC, were designed using the same unit-cell arrangement. Baseline XATL specimens were fabricated by powder bed fusion and tested under quasi-static axial compression to validate the finite element framework, which was subsequently used for numerical comparisons of XATL and XATLC and for the parametric analyses. The numerical model reproduced the main experimental deformation process, including inward contraction, progressive folding, local contact, and post-peak collapse. XATL exhibited a higher peak load, reaching 370 N, whereas XATLC showed slightly higher total energy absorption and higher specific energy absorption, reaching 2.6 J and 319 J/kg, respectively. Parametric analysis indicated that increasing height alters the deformation path and affects mass-specific energy absorption differently for the two cross-sectional configurations, whereas increasing wall thickness improves stiffness, peak load, and energy absorption while shortening the stable auxetic stage.