Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Optimal carbon fiber content transforms FDM-printed PET composites. At 15 wt% CF, tensile strength increases by 92% and elastic modulus by 283% versus the neat matrix. Post-printing annealing boosts heat deflection temperature by 147%. The combination of tailored reinforcement and simple thermal treatment delivers engineering-grade performance, making FDM-printed parts viable for automotive and aerospace applications.

ABSTRACT
Fused deposition modeling (FDM) of high-performance thermoplastics is limited by the trade-off between mechanical reinforcement and processability. Here, we address this gap by investigating the influence of short carbon fiber (SCF) content (5–20 wt%) on FDM-printed PET composites, with linear low-density polyethylene (LLDPE) and polyethylene grafted with maleic anhydride (PE-g-MA) incorporated to enhance toughness and interfacial compatibility. Rheological analysis indicates that an increase in CF content markedly enhances both the storage modulus and melt strength. Differential scanning calorimetry (DSC) analysis reveals a significant heterogeneous nucleation effect induced by CF. Micro-morphological assessments confirm uniform fiber distribution and robust interfacial adhesion at 15 wt% CF, whereas fiber agglomeration and more defects emerged at 20 wt% CF. Mechanical testing demonstrates that tensile strength, elastic modulus, and notched impact strength peak at 15 wt% CF, achieving increases of 92%, 283%, and 115%, respectively, relative to the matrix without CF. Notably, a post-printing annealing treatment further improves tensile strength by 18.1% and heat deflection temperature (HDT) by 146.7%. These results establish that 15 wt% CF is the optimal formulation for balancing processability and performance, providing a practical and scalable pathway for manufacturing high-performance carbon fiber reinforced polyethylene terephthalate (CF/PET) composites via FDM.