Thermal–Microstructural–Mechanical Interactions in 3D-Printed PLA/PHA-Wood Composites

This study investigates the interrelation between thermal cycling, microstructural evolution, thermal, and mechanical performance in 3D-printed PLA/PHA-wood composites produced via fused filament fabrication (FFF). Despite the growing interest in bio-based materials for FFF, the coupled effects of thermal processing, microstructural evolution, and resulting functional properties remain insufficiently understood. Understanding these relationships is essential for optimizing printing parameters and enabling the design of sustainable multifunctional components with tailored mechanical and thermal performance. Using high-resolution infrared imaging, synchrotron X-ray micro-tomography, and the transient plane source (TPS) method, we assess the effects of printing parameters such as temperature, base temperature, and layer height on thermal gradients, heat distribution during deposition, effective thermal transport, as well as thermal properties of 3D printed parts. Results indicate that deposition conditions significantly influence microstructural features, with porosity levels ranging from 22 % to 33 %, and pore alignment predominantly following the extrusion direction Tensile testing reveals that mechanical performance is highly dependent on printing angle and infill rate, with peak results (Young’s modulus of 484 MPa and tensile strength of 19.7 MPa) achieved at a 0° angle and 100% infill, where filament alignment maximizes structural integrity. Thermal characterization shows that conductivity (λ) scales with infill density (0.06–0.13 W/m·K), with 20% infill structures meeting high-performance insulation criteria (λ = 0.06 W/m·K). These findings demonstrate that, by strategically modulating printing architecture, these sustainable composites can be multifunctionalized, serving as either lightweight thermal barriers or high-strength structural components in advanced engineering applications.