Mechanical performance of triply periodic minimal surface (TPMS) lattices under multiple loading conditions

• G and D structures were tested under multiple loading conditions. • G structure exhibited more uniform load distribution compared to the D structure. • Medium stress triaxiality was the primary cause of damage in both structures. • S-curve-like geometry of G enables uniform stress and stable deformation. Triply periodic minimal surface (TPMS) lattices have attracted significant attention for their lightweight and superior mechanical properties. However, limited research has addressed their performance under multiple loading conditions in practical applications. This study aimed to address this gap by analyzing the mechanical properties, energy absorption capabilities, and fracture mechanisms of two TPMS structures—Gyroid (G) and Diamond (D)—under three-point bending, axial compression, and oblique compression. Experimental results showed that the G lattice consistently outperformed the D structure in energy absorption among all loading conditions. The superior mechanical performance of the G lattice compared to the D structure is attributed to its stable layer-by-layer deformation, which ensures more uniform stress distribution. In contrast, the D structure's grid-like geometry resulted in more localized stress concentrations and reduced energy absorption, particularly under oblique and bending loads. Axial compression provided the highest energy absorption for both structures due to the effective engagement of their periodic units, while three-point bending posed the most severe challenges, with fractures significantly reducing energy absorption efficiency. Simulation results revealed that medium stress triaxiality was the dominant trigger for damage initiation in both structures, with tensile stresses causing higher vulnerability due to lower fracture strain. The G structure exhibited more frequent damage initiation from mixed stress states, reflecting its complex stress interactions and superior load-bearing capabilities compared to the D structure. These findings enhance understanding of TPMS fracture mechanisms and provide valuable insights for optimizing their design to improve mechanical performance in practical applications.