Enhancing mechanical properties of environmentally friendly and renewable polymers by the introduction of natural fibers not only paves the way for developing sustainable composites but also enables new opportunities in advanced additive manufacturing (AM). In this paper, wood fibers, as a versatile renewable resource of cellulose, are integrated within bio-based polylactic acid (PLA) polymer for the development and 3D printing of sustainable and recycle green composites using fused deposition modeling (FDM) technology. The 3D-printed composites are comprehensively characterized to understand critical materials properties, including density, porosity, microstructures, tensile modulus, and ultimate strength. Non-contact digital image correlation (DIC) technology is employed to understand local stress and strain concentration during mechanical testing. The validated FDB-based AM process is employed to print honeycombs, woven bowls, and frame bins to demonstrate the manufacturing capability. The performance of 3D-printed honeycombs is tested under compressive loads with DIC to fully evaluate the mechanical performance and failure mechanism of ultra-light honeycomb structures. The research outcomes can be used to guide the design and optimization of AM-processed composite structures in a broad range of engineering applications.

Additive manufacturing has enabled the fabrication of complex, bioinspired lattice structures, such as Triply Periodic Minimal Surfaces (TPMSs), for use in lightweight structural applications. To assess their engineering viability, this study benchmarks the compressive properties of isotropic Gyroid and Primitive TPMS lattices against those of the conventional, anisotropic Honeycomb structure, which is widely used in the aerospace industry. We employed a combined computational and experimental approach, using Finite Element Analysis (FEA) for initial evaluation followed by mechanical compression testing of stereolithography (SLA)-printed polymer samples. Full-field strain was measured using Digital Image Correlation (DIC) to validate the simulations. The results show that the Gyroid has a strength-to-density of 5.692, the Primitive has a ratio of 5.182, the Honeycomb in the axial direction has a ratio of 26.144, and the Honeycomb in the transverse direction has a ratio of 1.008, all in units of $\mathrm{N}·{\mathrm{k}\mathrm{g}}^{-1}{\mathrm{m}}^3$. These results clearly indicate that the Honeycomb is best when uniaxially loaded. For other applications where the load paths will vary in multiple directions, the Gyroid is the better option.

Minor variations in print parameters are an inherent aspect of modern additive manufacturing (AM) processes. This study investigated the impact of 3 distinct print parameter variations in 21 combinations on the mechanical properties, as well as 2 print parameter variations in 9 combinations on the surface roughness properties, of as-built Ti-6Al-4V Grade 23 tensile specimens. The samples were fabricated using a Colibrium Additive M2 Series 5 laser powder bed fusion (L-PBF) printer with once-recycled and once and twice-recycled powder. The parameters examined included laser power, scan speed, and gas flow rate, with nominal conditions including a laser power of 370 W, a scanning speed of 1700 mm/s, a gas flow rate of 2.05 m/s, a hatch spacing of 0.11mm, and a layer thickness of 60 µm. Results indicated a statistically significant, yet minimal, effect on most mechanical properties. Specifically, ultimate tensile strength (UTS) exhibited a significant difference with a 21.7 MPa difference between the highest and lowest condition means, corresponding to 1.8% of the overall mean. Yield strength showed a significant difference and varied by 22.1 MPa, representing 2.0% of the overall mean, while fracture strength showed no significant differences across conditions. The significant differences found in surface roughness measurements are likely due to poor splatter removal causing melt pool instabilities. These findings suggest that printers calibrated within 10% of nominal laser power and scan speed, and within 5% of the nominal gas flow rate, are capable of producing components with consistent mechanical properties, despite minor statistically significant variations.