Geometric deviations and their effects in thin-plate lattice structures fabricated via LPBF

The fabrication of lattice structures through laser powder bed fusion (LPBF) has the potential to create architected materials with exceptional mechanical properties at low densities, with plate-lattice structures demonstrating the highest stiffness and strength to weight ratios. However, geometric deviations and defects introduced by the LPBF process result in plate-lattice geometries deviating from their intended ideal design, potentially compromising mechanical properties and increasing density without a proportional increase in strength. The intersecting and inclined thin-plate features that enable the high performance of plate-lattices are especially prone to compromising deviations, since plate-lattice features are fabricated at scales approaching the resolution limits of LPBF. This study presents a comprehensive analysis of geometric deviations and defects in AlSi10Mg LPBF plate-lattice structures, focusing on understanding the influence of both processing conditions and geometric features on deviation formation, and determining their detrimental effect on compression mechanics. Micro-CT scanning is used to examine the as-fabricated morphology of plate-lattice unit cells and identify trends in defect severity among different lattice topologies and volume fractions. Finite element analysis (FEA) of the ideal and as-fabricated unit cell geometry under compressive strain is performed to evaluate differences in strain energy density distribution and resultant lattice stiffness. FEA results show that deviations contribute to a 4.4-28.0% increase in minimally load-bearing lattice mass, reducing the specific stiffness of the lattice by 11.8-31.7% compared to ideal geometries. Minimally load-bearing mass arises from protruding surface variations and dross formations around powder drainage holes and overhanging features, while underprinting at critical plate intersections introduces stress concentrations. This work provides insight into how plate-lattice design and LPBF fabrication strategy impact as-fabricated lattice geometry and resulting mechanical performance.