TPMS and plate-based AlSi10Mg lattice structures: geometries parametrization and fatigue tests design

The growing demand for sustainability across the industrial and transportation sectors is driving the development of efficient and lightweight structural solutions. Among these, lattice structures based on triply periodic minimal surfaces (TPMS), such as Gyroid and Primitive, and lattices based on plate-like architectures, such as body-centred cubic (BCC) and face-centred cubic (FCC), have demonstrated significant potential for impact energy absorption and heat exchange applications. However, the absence of standardized procedures for the structural and multi-physical characterization of lattice materials limits an organized comparison of research progresses. While compression-compression and bending fatigue tests have been more commonly investigated by the academic community, static tensile tests and fatigue analysis under tension-compression cycles have not yet been explored to a comparable extent. This thesis aims to establish the fundamentals of tensile experimental characterization of TPMS- and plate-based lattice unit cells, providing reference data and modelling strategies for future fatigue investigations. Sixteen configurations were analysed, all manufactured in AlSi10Mg by laser powder bed fusion (L-PBF) using an EOS M290 system. Four unit-cell topologies—Primitive, Gyroid, BCC, and FCC—were studied at four relative densities: 10%, 15%, 20%, and the minimum achievable with the employed printer, constrained by a minimum wall thickness of 120 μm to ensure printability with the available system. For BCC and FCC lattices, a complete parametric formulation was developed to define cut-outs for unmelted powder removal and to establish relationships between geometry and target relative density, enabling straightforward design adjustments. A tensile-compression fatigue specimen geometry was also proposed, adapted from the ASTM E8/E8M-25 standard, with necessary modifications to accommodate lattice integration. Finite element methods (FEM) simulations under imposed displacement conditions were performed to design the specimens. Results indicated that square cross-section samples are not significantly affected by edge effects, and a general transition-zone design methodology, adaptable to different lattice topologies, was developed. Fracture initiation was predicted to occur within the specimen core, sufficiently distant from both the transition region and the gripping areas. For each lattice shape and density, the numerical simulations with imposed-displacement provided the reaction forces, corresponding to the onset of 50% and 90% of the ultimate tensile stress (UTS). These thresholds were approximated, within an uncertainty range, to the fatigue limit (σ_D) and to the stress limit at 1000 cycles (σ_1000), respectively. From these data, Wöhler (S–N) and Haigh diagrams were generated to estimate the samples fatigue failure under specified mean-alternate stress values. This will support the planning of future experimental campaigns. The results of this work establish a methodological and computational framework for the tensile characterization of lattice materials, contributing to the standardization of mechanical testing procedures for additively manufactured TPMS and plate-based structures.