Fracture behavior of sustainable wood and PLA composites fabricated by fused deposition modeling using essential work of fracture

The integration of additive manufacturing (AM) and green composites has wide potential for designing sustainable and eco-friendly structures. Green composites, made of natural fibers and bio-matrix matrices, balance mechanical performance against environmental responsibility. However, their structural reliability is based on fracture toughness, a field poorly developed for AM-manufactured materials. Fused Deposition Modeling (FDM), an extrusion-based AM process, enables the manufacture of low-cost fiber-reinforced thermoplastics with intricate geometries. This study investigates the essential work of fracture in a green wood-reinforced PLA composite fabricated by FDM. In this study, double-edge notch tension (DENT) specimens were evaluated under tension, and in addition to determining the specific work of fracture, the unnecessary work and the material ductility level were also evaluated. The DENTs were printed with three build orientations, 100% infill density, and a steel nozzle to evaluate process-induced anisotropy and inherent fracture resistance. Specific fracture work ranged from 11.62 to 76.06 kJ/m², with a maximum value in on-edge orientations. Ductility level ranged from 0.11 to 0.32, indicating medium deformability before failure. Morphology of the fracture surface was examined by Field Emission Scanning Electron Microscopy (FE-SEM) to understand failure mechanisms, where microstructural features controlling crack growth were seen. This integrated experimental research, using commercial filaments, highlights the importance of build direction to anisotropic fracture behavior and warrants the use of sustainable composites in engineering systems demanding mechanical performance and environmental sustainability.