Design-dependent mechanical performance of additively manufactured hybrid hierarchical TPMS-based auxetic polymer structures

Abstract Auxetic metamaterials with negative Poisson’s ratios exhibit unusual deformation behavior, making them ideal for energy absorption, biomedical, and protective applications. This study presents hybrid hierarchical polymer structures integrating Triply Periodic Minimal Surface (TPMS) geometries, Diamond (D), Gyroid (G), and Schwarz (S) into the walls of base auxetic lattices. Structures were fabricated using Tough resin via masked stereolithography (MSLA) 3D printing. Mechanical performance was evaluated under uniaxial compression in terms of stiffness, peak force, absorbed energy (AE), and specific absorbed energy (SAE). Additionally, bulk volume and surface area were used to determine the surface-area-to-volume ratio (SA/V). The results demonstrated that hybrid configurations significantly enhanced the SA/V ratio up to eightfold while maintaining auxetic behavior. Among the samples, the hexagonal honeycomb with Schwarz walls (HH–S) achieved the highest first peak force, whereas the square honeycomb rotated with Diamond walls (SHR-D) exhibited the lowest. The triangular honeycomb rotated with Schwarz walls (THR-S) recorded the highest AE, while Gyroid-based designs underperformed. The highest SAE (0.5790 J g −1 ) was observed in HH-D, while SH-D showed the lowest (0.0236 J g −1 ), indicating a 184.33 % difference. These findings highlight the effectiveness of TPMS-based hierarchical designs in improving the multifunctionality of auxetic metamaterials without sacrificing their inherent mechanical characteristics.