Effect of PES Sizing on the Properties of 3D ‐Printed Continuous Carbon Fiber/ PEEK Composites

ABSTRACT Addressing the limitations of high cost, complex processes, and poor adaptability for complex structures in traditional manufacturing of continuous carbon fiber‐reinforced polyetheretherketone (CCF/PEEK) composites, this study employed a dual‐nozzle 3D printing process to fabricate two types of composites. Using commercial carbon fiber (ECF) and polyethersulfone (PES)‐sized carbon fiber (PESCF) pre‐impregnated filaments as reinforcements and PEEK resin as the matrix, ECF/PEEK and PESCF/PEEK composites were prepared. A systematic analysis was conducted on their microstructure, mechanical properties, dynamic thermomechanical properties, porosity, and tribological performance. The results demonstrated that PES sizing significantly enhanced the fiber‐matrix interfacial adhesion compared to its commercial counterpart. This improved interface inhibited fiber pull‐out and pore formation, leading to reduced porosity. Consequently, the PESCF/PEEK composite exhibited substantial improvements in tensile strength (257.89 MPa), flexural strength (345.84 MPa), and impact strength (79.88 kJ/m ² ), which increased by 28.77%, 40.98%, and 10.10%, respectively, over the ECF/PEEK composite. The interlaminar shear strength increased by 48.90% to 18.30 MPa. Moreover, the tribological properties were markedly enhanced, with the average friction coefficient decreasing to 0.29 and the wear rate reduced by 10.71%. In conclusion, combining PES‐sized filaments with offline‐impregnated 3D printing proves to be an effective strategy for manufacturing high‐performance CCF/PEEK composites, offering a low‐cost and high‐strength solution for complex structural components in fields such as aerospace.