The fracture toughness of Schwarz Primitive triply periodic minimal surface lattice

Triply periodic minimal surface (TPMS) lattices have recently been shown to exhibit extraordinarily low den-sities and multi-functionalities. Nevertheless, the dependence of their fracture toughness KIc on relative density rho, unit cell size l and the number of unit cells ahead of the crack tip suggest a lack of understanding of the governing parameters. This also extends to the adequacy of using the current conventional fracture testing protocols. Therefore, the objective of this work is threefold: (i) extract the minimum Schwarz Primitive unit cells for ac-curate toughness measurement, (ii) estimate KIc of polylactic acid Schwarz Primitive TPMS applying linear elastic fracture mechanics (LEFM) conditions, (iii) investigate the effect of relative density rho and unit cell size l on the fracture toughness. With 18 cells along the specimen width, KIc is shown to increase linearly with rho and with the square root of l. Outcomes from this work is aimed toward understanding the damage tolerance of TPMS lattices, and hence the reliability of such new emerging lightweight materials.

Automated summary

Triply periodic minimal surface (TPMS) lattices have shown low densities and multi-functionalities, but there is a lack of understanding of the governing parameters, including fracture toughness and the use of conventional fracture testing protocols. This work aims to extract accurate toughness measurements, estimate KIc using LEFM conditions, and investigate the effect of relative density and unit cell size on fracture toughness. Results show that KIc increases linearly with relative density and with the square root of unit cell size. The outcomes contribute to understanding the damage tolerance of TPMS lattices and the reliability of lightweight materials.