Physico-mechanical and anisotropic performance of robotic large-scale additive manufacturing using sustainable wood-based PLA composites

This research investigates large-scale additive manufacturing of functional components from wood–based polymer composite on polylactic acid, containing 20 wt% cellulose fibres derived from birch. The main physico-mechanical characteristics of the printed specimens were evaluated, including tensile strength, flexural strength, hardness, density, water absorption, deformation, and thermophysical properties, as well as the microstructure using optical and scanning electron microscopy. The study investigates printing orientation-dependent anisotropy, which remains insufficiently characterised for PLA-based wood composites produced by LSAM. The influence of printing strategy was assessed by varying the printing layer orientation at 0°, 30°, 45°, 60° and 90° relative to the loading direction. The results show a strong dependence of mechanical properties on layer alignment: tensile strength decreased from 18.61 MPa (0°) to 5.22 MPa (90°), and flexural strength from 23.98 MPa (0°) to 6.87 MPa (90°), corresponding to reductions of approximately 70–72%. Scanning electron microscopy linked this anisotropy to weak interlayer adhesion and elevated porosity relative to the feedstock granules, supporting the interlayer interface as a dominant factor governing off-axis strength. The results confirm that the studied composite provides sufficient strength and durability for applications in furniture, design elements, tools, and building structures fabricated by large-scale additive manufacturing.