Mechanical and Dynamic Analysis of <scp>PLA</scp> ‐ <scp>PBS</scp> Biocomposites Reinforced With Flax Fibers: A Comparison Study of Injection Molding and <scp>FGF</scp> ‐ <scp>3D</scp> Printing

ABSTRACT This study investigates the mechanical, thermal, and dynamic behavior of polylactic acid (PLA)/poly(butylene succinate) (PBS) biopolymer blend processed by injection molding (IM) and fused granular fabrication (FGF 3D printing), with and without 20 wt% short flax fibers. Morphological analysis, fiber length distribution, differential scanning calorimetry, and dynamic mechanical analysis were conducted to highlight how processing methods affect fiber integrity and the resulting biocomposite properties. The results show that the incorporation of 20 wt% flax fibers significantly increases the melting enthalpy from 30.75 to 45.30 J/g and the degree of crystallinity from 41.33% to 60.92%. In addition, PLA‐PBS pellets containing 20 wt% short flax fibers were successfully processed and printed via FGF. The average fibers length was higher in injection‐molded samples (930 μm) than in 3D‐printed ones (659 μm), indicating that injection molding better preserves fiber integrity and thus provides more efficient reinforcement. IM‐FF/PLA‐PBS retained a higher proportion of long fibers, with 30% exceeding 1 mm, compared to only 16% in 3D‐FF/PLA‐PBS samples. Consequently, IM‐FF/PLA‐PBS specimens showed enhanced mechanical performance, with higher stiffness ( E = 4.90 GPa) and tensile strength ( σ = 42.4 MPa) than their 3D‐FF/PLA‐PBS counterparts ( E = 2.22 GPa, σ = 11.5 MPa). Furthermore, DMA results revealed higher storage moduli for IM‐FF/PLA‐PBS (3620 MPa) compared to 3D‐FF/PLA‐PBS (800 MPa), confirming increased stiffness and improved fiber–matrix adhesion. However, 3D‐FF/PLA‐PBS and 3D‐PLA‐PBS yielded lighter components, advantageous for weight‐critical applications. Overall, these findings highlight the significant influence of processing techniques on biocomposite performance.