Influence of L-PBF Process Anisotropy on the Isotropic Behaviour of TPMS Structures

Triply Periodic Minimal Surfaces (TPMS) structures, such as the Gyroid, can exhibit nearly isotropic mechanical behaviour over specific relative density ranges, as predicted by the Zener anisotropy ratio. In contrast, the Laser Powder Bed Fusion (L-PBF) process may induce anisotropy in the material due to thermal gradients and residual stresses, potentially influencing the overall structural response. This work investigates how the anisotropy generated by the L-PBF process interacts with the inherent isotropy of Gyroid architecture. Gyroid lattices in 316L stainless steel were produced with varying unit cell sizes and wall thickness. Quasi-static compression tests were performed along directions parallel and perpendicular to the build axis to evaluate orientation effects. Numerical simulations, using both isotropic and anisotropic material properties, were employed to estimate the effective elastic response and the Zener anisotropy ratio. The combined experimental and numerical study aims to assess whether and to what extent the Gyroid architecture partially mitigates the transmission of process-induced anisotropy to the effective elastic response, contributing to a better understanding of the mechanical behaviour of additively manufactured metallic lattices. In particular, the study clarifies whether the theoretically isotropic Gyroid architecture is able to attenuate or transfer L-PBF-induced material anisotropy at the lattice scale.