Influence of Annealing Temperature on the Thermomechanical Properties and Dimensional Stability of <scp>FFF</scp> ‐Printed <scp>PET</scp> ‐ <scp>CF</scp>

ABSTRACT This study systematically investigates the influence of annealing temperature () on the thermomechanical behavior and dimensional stability of carbon fiber‐reinforced polyethylene terephthalate (PET‐CF) components manufactured via fused filament fabrication (FFF). Test specimens were subjected to thermal post‐processing at temperatures ranging from 145°C to 225°C. Differential scanning calorimetry (DSC) was used to analyze the melting behavior and degree of crystallinity. To evaluate thermal softening behavior, Vicat softening temperature (VST) measurements were performed. The DSC analysis revealed the formation of a secondary endothermic melting peak at the lower melting temperature that exhibits a linear correlation with the annealing temperature. While the total crystallinity remained largely unaffected, annealing significantly shifted the onset of softening to higher temperatures compared to untreated samples. Furthermore, the thermal post‐processing significantly improved the repeatability of the VST measurements. However, the improvements in thermal resistance were accompanied by increased longitudinal and transverse shrinkage, with the most pronounced dimensional shrinkage occurring in the build direction ( Z ‐axis). The results demonstrate that while annealing is an effective strategy for enhancing the heat resistance and reliability of FFF‐printed PET‐CF components, industrial applications must balance the gains in thermal stability against the corresponding loss in dimensional precision.