Material Extrusion of <scp>PLA</scp> /Recycled Short Flax Fiber Biocomposites

ABSTRACT Biocomposites are sustainable alternatives to conventional composites due to their biodegradability and renewability. This study investigates the mechanical properties of 3D‐printed flax fiber‐reinforced polylactic acid (PLA) composites with fiber weight fractions ranging from 0% to 5%, and examines the effects of a 2% (w/v) sodium hydroxide solution treatment on the composite properties. Adding untreated fiber reduces the mechanical properties of single filaments, while the addition of treated fiber improves tensile strength by 16% and tensile modulus by 14% with up to 5 wt.% flax fiber content in the biocomposite. The treated fibers significantly increase the stiffness of the 3D‐printed samples, with an 81% rise in Young's modulus. Compared to pure PLA samples, a 41% improvement is observed with 2.5 wt.% content of treated flax fiber. However, tensile strength decreases by 35% across all samples, with greater reductions following treatment. Compression tests show a 23% strength increase for samples with untreated fibers, but performance declines with chemical treatment. Microscopic images reveal voids that impact mechanical properties, while Fourier‐transform infrared spectroscopy confirms the effects of fiber surface modification. These findings highlight the trade‐offs between improving stiffness and reducing strength when pre‐treatment of flax fibers are used, and underscore the potential of flax fiber‐reinforced PLA biocomposites in sustainable additive manufacturing for environmentally‐benign a advanced material production.