Improved compressive strength of PBF-LB Al7050 lattice structures via PA12–epoxy infiltration

High-strength Al7050 lattice structures were fabricated using laser powder bed fusion (PBF-LB) to investigate the influence of lattice topology and polymer infiltration on compressive behavior. Four geometries—gyroid (P1), planar hexagonal (P2), strut-based three-dimensional lattice (P3), and diamond lattice (P4)—were produced and subsequently infiltrated with recycled PA12 and epoxy. Surface morphology and infill distribution were evaluated using digital microscopy, while quasi-static compression tests were conducted to assess mechanical performance. The results show that the gyroid structure exhibits more uniform deformation and relatively higher compressive strength, whereas strut-based geometries display localized buckling and collapse. Polymer infiltration enhances the mechanical response across all topologies, with epoxy-filled samples consistently outperforming PA12-filled ones due to more effective infiltration and improved load transfer. Although strut-based lattices absorb greater amounts of polymer, the resulting improvement in strength is not directly proportional to the mass increase. Notably, the epoxy-filled P3 structure shows a significant increase in peak stress, from 45 to 138 MPa. These findings highlight the importance of considering both lattice topology and infiltration behavior when designing lightweight structures with improved mechanical performance.