• A novel harakeke (New Zealand flax) fiber–reinforced PLA composite was developed and fabricated using FDM 3D printing, targeting lightweight and sustainable structural applications. • A Response Surface Methodology (RSM) framework (Central Composite Design) was employed to model and optimize the combined influence of fiber content (0–20 wt.%), raster angle (45–90°), and raster width (0.5–1.0 mm) on mechanical properties. • The optimal printing parameters were identified as 10 wt.% fiber content, 0.5 mm raster width, and a 45° raster angle, producing the best balance of stiffness and strength. • The optimized composite achieved a Young’s modulus of 4453.85 MPa and a flexural stress of 73.395 MPa, outperforming other parameter combinations. • Raster angle was found to be the most influential parameter, with a 45° orientation consistently improving load transfer and stress distribution. • Excessive fiber loading (>10 wt.%) reduced tensile and flexural performance due to fiber agglomeration, increased melt viscosity, and compromised fiber–matrix interfacial adhesion. • Narrow raster widths (0.5 mm) improved interlayer fusion and deposition density, contributing significantly to enhanced composite stiffness. • The study confirms that controlled fiber dispersion and optimized FDM settings are crucial for unlocking the structural potential of PLA–harakeke biocomposites. • Results establish a validated RSM-based predictive model (desirability = 0.91) to guide process optimization for sustainable, high-performance 3D-printed materials. Current research on the shift toward sustainable materials has intensified interest in biodegradable alternatives polymers, with poly-lactic acid (PLA) emerging as a leading candidate. With various advantages, including biodegradability and processability, PLA's tensile and flexural strength can be further enhanced to increase its use in lightweight structural applications. This study introduces a novel integration of harakeke (New Zealand flax) fibers into PLA, a material pairing that has not been comprehensively investigated for additive manufacturing-based components. The research uniquely employs a Response Surface Methodology (RSM)-based optimization framework to systematically analyze and model the combined effects of fiber content (0-20 wt.%), raster angle (45-90°), and raster width (0.5-1.0 mm) on the composite’s tensile and flexural performance. The findings reveal that a raster width of 0.5 mm, raster angle of 45°, and a flax infill of 10% by weight provide the best synergy of stiffness and strength. The maximum values of Young's modulus are 4453.85 MPa, and the flexural stress is 73.395 MPa. Increased fiber loadings above 20 wt.% reduce performance due to fiber agglomeration. Among orientations, the 45° raster is preferable to 90° due to increased load transfer and stress distribution, and narrower raster widths facilitate greater interlayer bonding and deposition density.
Selvamani et al. (Wed,) studied this question.