Synergistic Continuous and Short Fiber Reinforcement in Additively Manufactured Poly(Ether Ether Ketone) Composites

ABSTRACT Enhancing the mechanical properties of 3D‐printed thermoplastic composites has become a critical focus in advanced manufacturing, particularly for high‐performance materials like PEEK. To address limitations in strength, this study investigates a synergistic reinforcement strategy combining both continuous and short carbon fibers in PEEK‐based composites. A novel filament structure was developed, with a continuous fiber‐reinforced core wrapped by a short fiber‐reinforced shell. The resulting synergistic carbon fiber‐reinforced thermoplastic (S‐CFRTP) filaments contained 5.11% chopped fibers and 23.76% continuous fibers. These filaments were then used in a fused filament fabrication (FFF) printer to manufacture composite specimens. Mechanical properties were evaluated through filament tensile and printed sample three‐point bending tests. The S‐CFRTP has shown an increase in the elasticity modulus; however, it showed premature failure that caused a decrease in the maximum flexural stress values, which indicated that further improvements should be made for interlayer bonding performance. Optical microscopy was employed to examine fracture surfaces and fiber distribution. This study shows that the synergistic reinforcement method can enhance some mechanical performance, append additional properties depending on synergistic materials, offering a promising approach for expanding the capabilities of continuous fiber additive manufacturing.