Coupled Effect of TPMS Architecture and Actual Fabricated Relative Density on the Compressive and Energy-Absorption Behavior of LPBF-Fabricated Ti-6Al-4V Lattices

Abstract

Additive manufacturing of triply periodic minimal surface (TPMS) lattice structures improves the manufacturability of lightweight components with high energy-absorption capability. However, the relationship between processing conditions, surface morphology, and mechanical performance has not yet been fully correlated. This study presents a framework to correlate the effects of TPMS architecture, actual fabricated relative density, and surface complexity on the compressive and energy-absorption behavior of LPBF-fabricated TPMS lattices, with diffraction-derived microstrain treated as a supplementary process-induced indicator by considering gyroid, Schwarz Primitive, and Split-P structures with relative densities of 15%, 30%, and 45%, respectively. The results show that structural fabrication increases the wall thickness and structural volume relative to the proposed design models, which is primarily ascribed to melt-pool spreading and powder adhesion. Surface morphology using optical profilometry and field-emission scanning electron microscopy (FESEM) reveals distinct characteristics in roughness and porous structures among different TPMSs. In particular, gyroid lattices exhibit higher-amplitude roughness, while Split-P structures show greater surface complexity. Furthermore, the evolution of residual stress predicted by thermomechanical simulation was compared with Williamson−Hall-derived indicative stress estimates, showing qualitative trend-level agreement. Relevant deviations were observed within the compressive stress range. Compression tests reveal that energy absorption is mainly influenced by relative density, while the TPMS architecture and surface characteristics play an important role in deformation behavior and stability. It should be noted that the Split-P structure with the relative density of 45% exhibits the highest energy absorption and load-bearing capacity. The findings in this study provide an insightful guidance to the design and optimization of TPMS lattices for lightweight structures and energy-absorption applications.