Beyond layered limitations: A novel multi-thermal optimization framework of 3D-printed short carbon fiber-reinforced polyether-ether-ketone (SCF-PEEK)

Short carbon fiber-reinforced polyether-ether-ketone (SCF-PEEK) is a high-performance composite with excellent mechanical and thermal properties, making it a prime candidate for advanced applications in biomedical, aerospace, and automotive. However, fabricating 3D-printed SCF-PEEK using fused deposition modeling (FDM) is hindered by challenges such as poor interlayer adhesion, mechanical anisotropy, and suboptimal process parameters. This study introduces a novel multi-thermal parameter optimization framework leveraging an open-source FDM printer equipped with a direct annealing system (DAS). By systematically optimizing printing temperature, DAS temperature, and post-process heat treatment, the optimal parameters (printing: 440 °C, DAS: 440 °C, heat-treatment: 200 °C) yielded remarkable enhancements in interlayer adhesion and mechanical performance. Compression and tensile testing, along with density and differential scanning calorimetry analyses, confirmed consistent density (1.29–1.31 g⋅cm⁻³) and degree of crystallinity (26–36 %) across all fabrication conditions. DAS transformed the compression failure mechanism from a single shear fracture to a micro-buckling with interlayer and intralayer damage, while upright tensile fractures shifted from smooth to rough surfaces with thicker crystalline spherulites, indicating improved interlayer adhesion. Anisotropic mechanical behavior was evaluated in upright, 45°, and flat orientations under compression and tensile loads. Flat-oriented tensile samples exhibited the highest UTS and elastic modulus, while upright-oriented compressive samples had the highest UCS, and flat-oriented compressive samples showed the highest elastic modulus, attributed to fiber alignment. This study establishes a new benchmark for SCF-PEEK fabrication via FDM, highlighting the critical role of thermal optimization in enhancing mechanical durability and interlayer bonding while providing insights into the effects of orientation and fiber–matrix interactions on failure behavior.