3D printing of continuous fiber-reinforced ceramic matrix composites: Influence of process parameters on microstructure and tensile strength

Ceramic Matrix Composites (CMCs) are materials in which ceramics are reinforced with fibers or other materials, providing enhanced functionalities, such as damage tolerance, in addition to their inherent heat resistance. This study investigates a manufacturing method for continuous alumina-mullite fiber-reinforced alumina CMCs using a commercial Fused Deposition Modeling (FDM) 3D printer, demonstrating a flexible and practical route for continuous fiber-reinforced CMC fabrication. The process utilizes a pre-impregnated filament, which serves as the fundamental component for depositing both the ceramic matrix and continuous reinforcement. The 3D printing filament was fabricated by melting a mixture of alumina, serving as the matrix material, and a thermoplastic resin to impregnate the alumina-mullite mixed fibers. Filaments with a diameter of 0.4 mm exhibited fewer cracks compared to those with a diameter of 0.6 mm. Moreover, a filament with fewer voids was produced when the heating temperature during impregnation was 230 °C. Using the fabricated filament, simple three-layered rectangular test specimens, with a length of 110 mm and a width of 10 mm, were successfully printed. A tensile strength of approximately 250 MPa was achieved along the fiber direction. The observed fracture behavior indicates that improving the interlaminar strength would likely further enhance the tensile strength. The impact of this research is introducing a new manufacturing method that will expand the design freedom and accessibility of complex-shaped CMCs. This pioneering achievement provides a foundational baseline for researchers and engineers to transition 3D printed continuous fiber-reinforced CMCs from laboratory-scale prototypes to structural components.