Enhanced compressive performance and energy absorption in SLM-fabricated 316L arrowhead auxetics via tendon and stuffer geometry modification

Abstract

This study systematically investigates how tailoring the geometry of double-arrowhead auxetic lattice structures — specifically by reducing tendon dimensions while enlarging stuffers — impacts their compressive behavior and energy absorption capabilities. Specimens were fabricated from 316L stainless steel using Selective Laser Melting (SLM) at target relative densities of 5%, 10%, and 15%. We compare the performance of a baseline configuration with equal-sized tendons and stuffers (Lat1 N) against a modified configuration featuring smaller tendons and larger stuffers (Lat1 S). The mechanical response was characterized through a combination of experimental testing, including quasi-static and dynamic (Split Hopkinson Pressure Bar, SHPB) compression, and validated Finite Element Modeling (FEM) analyses, focusing on deformation mechanisms, energy absorption efficiency, Poisson's ratio evolution, and failure modes. Results confirm that increasing relative density significantly enhances the mechanical properties of both auxetic lattice designs. Critically, the geometrically modified Lat1 S configuration consistently demonstrated superior mechanical performance over the baseline Lat1 N, particularly at higher relative densities. For instance, at 15% relative density, Lat1 S exhibited a quasi-static plateau stress of 42MPa (21% higher than Lat1 N's 35MPa) and a dynamic plateau stress of 48MPa under P=0.25MPa impact (24% higher than Lat1 N's 38.5MPa). Correspondingly, the yield stresses for Lat1 S were 42.49MPa (quasi-static) and 48.98MPa (dynamic at P=0.25MPa), exceeding the respective Lat1 N values (36.5MPa and 41.24MPa). Furthermore, the enhanced design (Lat1 S) achieved superior energy management, reaching an energy absorption per volume (W) of 10.67MJ/m3 and a specific energy absorption (SEA) up to 32J/g, approximately 20% greater than Lat1 N at higher densities. Both configurations exhibited significant strain rate sensitivity, with the dynamic increase factor (DIF) ranging from 1.15 to 1.85 across the tested rates. The improved compressive resistance and energy absorption in Lat1 S are attributed to the enhanced load distribution facilitated by the larger stuffers, highlighting a promising strategy for optimizing auxetic metamaterials for protective applications.