The Effect of Printing Temperature on the Fused Granular Fabrication Property of Flax/ PP Agro‐Composites at Microscale

ABSTRACT This study investigates the influence of printing temperature on the mechanical behavior and failure mechanisms of flax fiber‐reinforced polypropylene (PP) composites fabricated using fused granular fabrication (FGF). Dog‐bone tensile specimens were printed at temperatures ranging from 170°C to 220°C. As the printing temperature increased, surface defects decreased and interlayer adhesion improved, with the smoothest surface morphology observed at 210°C. At 220°C, however, fiber oxidation and matrix degradation were evident, resulting in microstructural defects and reduced mechanical performance. The highest tensile strength, ~12 MPa, was achieved at 210°C. At this temperature, stress whitening occurred in the PP matrix, indicating enhanced matrix plastic deformation rather than directly signifying fiber–matrix bonding. Scanning electron microscopy (SEM) revealed improved interfacial embedding and matrix continuity at 210°C, whereas lower temperatures exhibited interfacial voids and fiber pull‐out, and higher temperatures led to fiber cracking and thermal damage. Overall, 210°C was identified as the optimal printing temperature, offering a balance between mechanical performance, interfacial quality, and thermal stability. These findings provide valuable guidance for the process optimization of natural fiber‐reinforced thermoplastic composites in sustainable FGF‐based additive manufacturing.