Development and Fabrication of 3D-Printed Foam-Filled PLA/PCL Lattice Structures With Tunable Shape Memory and Mechanical Performance

This study presents the development of foam-filled polylactic acid (PLA)/polycaprolactone (PCL) lattice structures fabricated via fused deposition modeling (FDM) to achieve tunable mechanical strength and thermal shape memory performance. Three lattice geometries (hexagonal, triangular, grid) were produced at 0%, 10%, and 20% infill densities and subsequently filled with polyurethane (PUR) foam. The printed lattice provided geometric stability, while the foam core enhanced damping, energy absorption, and recovery support. Mechanical tests showed that higher infill densities, particularly with hexagonal patterns, significantly increased flexural strength and impact resistance through improved foam confinement and load transfer. Shape memory tests revealed consistently high fixation ratios (> 91%) but recovery ratios ranging from 33% to 89%, with low density exhibiting faster and more complete recovery due to greater matrix mobility. PUR foam played a passive stabilizing role, aiding recovery in open architectures but slightly constraining it in dense designs. The results demonstrate that careful tuning of lattice geometry and infill density enables the design of lightweight, multifunctional composites suitable for reusable protective gear, energy-absorbing components, and thermally responsive adaptive systems.