Scale-dependent mechanical performance variations in polylactic acid lattice structures fabricated via additive manufacturing

The objective of this research is to explore the scale effect on the mechanical properties of sheet-based triply periodic minimal surface (TPMS) uniform lattice structures fabricated with PLA (polylactic acid) under quasi-static loading conditions. The scale dependency was evaluated by two additional breakdown categories, namely, wall thickness effect and unit cell size effect. Deformation mechanisms and failure modes as well as mechanical properties including stiffness, yield strength, first peak stress, and energy absorption based on the categories of wall thickness, unit cell size, and scale were evaluated experimentally. The assessment of the scale effect involved considering the combined influence of wall thickness and unit cell size. In addition, numerical analysis was also performed to investigate the stress distributions and compare with the experimental results for certain geometries. Ultimately, the relation between the normalized mechanical properties and relative density is evaluated and categorized, which can be used as an indication for future design practices.