Microstructure evolution and anisotropic mechanical performance of CF/PEEK composites fabricated by LPBF additive manufacturing

Abstract

Laser Powder Bed Fusion (LPBF) has emerged as a promising additive manufacturing technique for fabricating high-performance carbon fiber-reinforced polyetheretherketone (CF/PEEK) composites. This study systematically investigates their processability, microstructural evolution, and anisotropic behavior. Angle of repose (AOR) measurements confirmed that composites containing up to 15 wt%CF maintained good flowability suitable for LPBF. Thermal analysis revealed that CF incorporation had little effect on the melting behavior of PEEK, while enhancing thermal stability and narrowing the crystallization window. Mechanical testing demonstrated that optimal performance was achieved at a laser power of 25 W, where the 15 wt%CF/PEEK composite exhibited a tensile strength of 119.8 MPa and an elastic modulus of 8.0 GPa, accompanied by reduced porosity (2.12 %) that reflects effective densification. XRD analysis further revealed strong correlations between lattice parameter variations and mechanical performance, highlighting the role of crystalline structure. Pronounced anisotropy was observed due to fiber alignment induced by the recoating process: tensile strength followed the order x- > xy- > y- orientation, while thermal conductivity of the 15 wt% composite increased by 343 % and 109 % along the X and Y directions, respectively, compared with pure PEEK. These findings contribute to a clearer understanding of the relationships between processing conditions, microstructural features, and performance in LPBF-fabricated CF/PEEK composites.