Melt‐impregnation and sizing optimization for the fabrication of high‐performance 3D printed continuous carbon fiber‐reinforced polyetheretherketone filaments

Abstract Continuous carbon fiber‐reinforced polyetheretherketone (CCF/PEEK) possesses superior mechanical and physicochemical properties, making it highly desirable for engineering applications. While 3D printing offers cost‐effective and efficient manufacturing for CCF/PEEK, current filaments have low fiber content and poor mechanical properties, limiting the performance of printed parts. To improve this, we first investigated the effects of the melt impregnation process parameters on the quality of CCF/PEEK filament. The evolution of the filament properties was examined by conducting mechanical tests, thermal performance characterization, and microscopic morphology observations. The optimized process parameters resulted in a filament tensile strength of 1274.6 MPa. This paper also developed a fiber‐sizing device to improve the filament formation process and investigated the impact of the sizing agent formulation on the tensile strength. Atomic force microscopy, surface element analysis, and surface energy calculations revealed that the sizing treatment enhanced the interfacial bonding properties between CF and PEEK. Specifically, we found that mechanical interlocking, hydrogen bond formation, and wetting behavior enhanced the interfacial bonding between CF and PEEK to yield a post‐sizing filament tensile strength of 1589.6 MPa. These enhancements support further advancement of engineering applications for continuous fiber‐reinforced composite 3D printing technology. Highlights Development of a continuous CCF/PEEK filaments forming device. CCF/PEEK filament tensile strength reached 1589.6 MPa. Fiber‐sizing device for optimal filament formation. Optimization of carbon‐fiber sizing and melt impregnation. High carbon fiber/PEEK interfacial bonding.