Hot powder bed compaction of additively manufactured lattice sandwich structures with truss-aligned fiber reinforcement

Fused deposition modeling (FDM) of lattice sandwich structures (LSS) enables components with tailored fiber orientation for improved structural behavior. However, traditional FDM suffers from inherent defects such as insufficient fusion bonding and high porosity. This study considers applying Hot Powder Bed Compaction (HPBC) to FDM-printed fiber-reinforced PA6 LSS structures with relative density of 0.7 g/cm³ to eliminate the processed defects and improve bending performance. HPBC preserved the lattice features with controlled shrinkage while reducing void content from 16.8% to 2.3%, as quantified by microscopy of cross-sections, resulting in more than 2.2× increase in bending stiffness and 154% improvement in bending strength compared to the as-printed part. The post-HPBC failure mode changed from truss buckling with widespread skin-yielding in the pristine part to localized skin yielding post-HPBC. The SEM fracture analysis showed a transition from fiber pull-out failure in pristine FDM part to a monolithic fracture in the HPBC part. The structural performance post-HPBC was analyzed using multi-scale finite element analysis based on the microstructural composition that was used for formulating an anisotropic constitutive material model. The progressive failure analysis was performed using continuous damage mechanics framework, which captured stiffness, strength, and failure progression that was observed experimentally in HPBC-treated LSS.