Tensile and flexural performance of FDM 3D printed Harakeke (NZ Flax) fiber -PLA composites for lightweight structural applications

Abstract

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.