Mechanical Characterization of CNT / PLA Parts via FFF Additive Manufacturing

Fused filament fabrication (FFF) enables the production of complex thermoplastic components but is often limited by internal porosity and insufficient mechanical performance for structural applications. This study investigated how heating cycles, CNT concentration, and infill density jointly influenced the rheological and mechanical behavior of FFF‐printed CNT/PLA composites. PLA and CNT/PLA filaments were fabricated by melt mixing and extrusion and printed under controlled conditions. The effects of heating rounds, CNT content (0–1.0 wt%), and infill density (60%–100%) were evaluated using melt flow index measurements, tensile testing, scanning electron microscopy, and micro‐computed tomography. The results show that repeated heating increases melt flow index and reduces both stiffness and ductility due to polymer degradation. CNT addition significantly enhanced stiffness, with elastic modulus increasing by up to 53%, while tensile strength and elongation at break increased by up to 27% and 8% under optimal conditions. Moreover, specimens printed at 60% infill density exhibited elastic moduli comparable to fully dense parts because over‐extrusion partially filled internal gaps. These results demonstrate that coordinated control of CNT reinforcement, thermal history, and infill design enables the fabrication of lightweight, mechanically efficient CNT/PLA components for high‐performance FFF applications.