Validation of material-invariant mechanical models for triply periodic minimal surface structures

Their dual functionality makes triply periodic minimal surface (TPMS) sheet networks an ideal candidate for permeable, load-bearing cellular structures. The present study investigates Gyroid and Primitive structures in quasi-static compression. Cubic polymeric TPMS specimens of 90 mm edge length with a relative density between 0.1 and 0.7 are manufactured additively by means of selective laser sintering and stereolithography. Aiming at material-invariant findings, the authors test solid specimens to normalize cellular properties with the printed solid‘s properties. The resulting relative stiffness, strength, and energy absorption are modeled as a function of relative density. Mechanical models are obtained from tests with sintered Nylon 11 specimens. The relative compressive properties of Gyroid and Primitive structures differ marginally. A linear function describes their material utilization in approximation. Additionally, this study identifies and quantifies the constraints that selective laser sintering and stereolithography impose on the manufacturability and mechanical performance of TPMS specimens, emphasizing their relevance to application-related research using industry-oriented methods. A comparison with previous studies confirms that experimentally obtained results align more closely with the findings of FE analysis as the influence of defects diminishes. The modeled relative modulus found in this study corresponds with the work of other authors on different base materials in overlapping relative density intervals and underlines the material-independent mechanical characteristics of TPMS structures.