Investigating the tensile and bending properties of triply periodic minimal surface structures as protective buffer structure

Homogeneous and functionally graded triply periodic minimal surface (TPMS) structures (Schwarz P, Gyroid, Diamond) were fabricated from thermoplastic polyurethane (TPU)/polylactic acid (PLA) composites via 3D printing to develop advanced protective buffer components. The designed internal architectures were successfully confirmed via computed tomography (CT). Macroscopic mechanical properties were systematically investigated through tensile and three-point bending tests, coupled with finite element analysis (FEA). Results revealed that Diamond and Gyroid topologies utilize highly efficient shear- and bending-dominated mechanisms to dissipate stress, whereas the Schwarz P structure suffers from tension-dominated localized yielding. Targeted graded designs exponentially improved flexural performance in well-interconnected topologies. For instance, the graded Diamond structure achieved a remarkable specific peak load of 23.22 N/g and a bending stiffness of 252.1 × 10 3 N/mm 2 , outperforming its homogeneous counterpart by 92.5% and 157.5%, respectively. Conversely, the graded Schwarz P structure performed worse than its uniform counterpart due to localized collapse of upper thinned struts. Consequently, this work demonstrates that Diamond-based graded TPMS structures offer a highly optimized, data-supported balance of mechanical resilience and energy absorption, highlighting their exceptional value for advanced impact-protection engineering.