LIU Wenguang, QU Shengwen, YANG Lihua, XU Zuquan, WANG Xingguo, FENG Hao

(Jingdezhen Ceramic University, Jingdezhen 333403, Jiangxi, China)

Extended abstract:[Significance] Ceramic matrix composites (CMCs), especally continuous riber reinforced CMCs (CFRCMCs), overcome the brittleness of monolithic ceramics, offering exceptional strength, fracture toughness and thermal stability, for demanding aerospace, energy and automotive applications. This is reflected in a growing market, projected to rise from $7.83 billion in 2024 to $15.83 billion by 2030. However, manufacturing complex-shaped components is hindered by traditional methods, such as chemical vapor infiltration (CVI), polymer impregnation and pyrolysis (PIP) and liquid silicon infiltration (LSI), which are multi-step, time-consuming and costly. Additive manufacturing (AM) emerges as a revolutionary solution. The layer-by-layer fabrication process enables unparalleled design freedom, allowing for rapid and cost-effective production of complex CFRCMC components that cannot be achieved by using the traditional techniques, thus overcoming a critical manufacturing bottleneck.[Progress] This review was aimed to systematically chronicle the significant progress in AM of CFRCMCs, with research currently dominated by material extrusion (ME) processes, due to their relative simple in integrating continuous fibers. There are two primary ME techniques: fused deposition modeling (FDM) and direct ink writing (DIW). The FDM involves the co-extrusion of a thermoplastic filament (often blended with ceramic or precursor powders) and a continuous fiber to create a composite green body. This polymer-rich structure is subsequently transformed into a ceramic component through critical post-processing techniques, primarily PIP or LSI. Successes include the fabrication of C_f/SiC, C_f/SiOC and Cf/ZrB₂-SiC composites. In DIW method, the most prevalent for CFRCMCs, employs the co-extrusion of a ceramic slurry with continuous fibers, typically through a coaxial nozzle. Innovations include optimized nozzle designs guided by finite element simulation, core-shell printing for multi-filament structures and thermal-assisted systems for high-precision printing. To overcome the limited fiber volume fractions, alternative strategies, such as separate fiber placement and even vertical fiber layup, have been developed. Beyond ME, preliminary explorations using stereolithography (SLA), powder bed fusion (PBF) and laminated object manufacturing (LOM) have demonstrated the potential for a broader AM toolkit. Substantial research has been dedicated to overcoming two core challenges: slurry rheology and printability. Successful co-extrusion hinges on tailored rheological properties. Strategies include formulating shear-thinning slurries using nanoparticles (e.g., nano-SiO₂) or adjusting binder content (e.g., carboxymethyl cellulose) to enhance viscosity and adhesive drag forces. Concurrent optimization of nozzle geometry (diameter, insertion angle) and printing parameters (layer height, pressure) is essential for stable extrusion and dimensional accuracy. In terms of fiber-matrix interface design, the interface is critical for activating toughening mechanisms. Research has been focused on the precise deposition of nano-scale interphases, such as pyrolytic carbon (PyC) or SiC via CVI or colloidal deposition. It has been systematically shown that an optimal interphase thickness (e.g., ~110 nm for PyC) promotes crack deflection and fiber pull-out, dramatically enhancing fracture toughness and transforming the composite's failure from brittle to non-catastrophic. For densification and pore control, the inherently porous AM green bodies require extensive post-processing. PIP is widely used, with multiple cycles progressively reducing open porosity to below 10%. Alternatively, LSI has proven highly effective, infiltrating a carbonized preform to form a dense SiC matrix, achieving final porosities of as low as 10%–20% or even below 1%. Managing the pre-infiltrated carbon density is crucial for optimizing LSI outcomes. Furthermore, AM enables the precise control and study of key toughening mechanisms, interfacial debonding, fiber bridging and pull-out, crack deflection and plastic deformation of ductile phases, which collectively enable a graceful, damage-tolerant failure mode. This control has also facilitated the fabrication of multifunctional CFRCMCs, including components for ultra-high-temperature ablation protection (e.g., C_f/ZrB₂-SiC), electromagnetic wave absorption/transparency, thermal insulation, fireproofing and biocompatible bone scaffolds, showcasing the technology's vast potential beyond structural applications.[Conclusions and prospects] In summary, AM has established itself as a viable and transformative route for fabricating continuous fiber-reinforced ceramic matrix composites (CFRCMCs), enabling the production of complex high-performance components beyond the capabilities of the traditional methods. Progress in material extrusion techniques and a deeper understanding of post-processing have laid a solid foundation for future development. However, key challenges must be addressed to realize the full potential of AM. Future research needs to focus on: (1) achieving true 3D fiber reinforcement with innovative print-head designs to minimize interlayer defects, (2) advancing multi-material integration with novel precursors and systems for functionally graded components and (3) implementing intelligent manufacturing via digital twins and AI for real-time process monitoring and optimization, ensuring reliability and cost-effectiveness. By addressing these challenges through interdisciplinary efforts, AM for CFRCMCs is poised to transition from a laboratory innovation to a mainstream high-reliability manufacturing technology, enabling a new generation of engineering systems for extreme environments.

Key words: additive manufacturing; continuous fiber reinforced ceramic matrix composites; material extrusion; stereo lithography appearance; powder bed fusion