Design and construction of the interphase in SiCf/SiC composites: From mechanical performance requirements to structure-function integration

This paper provides a systematic review of recent advances in the interphase research for silicon carbide fiber reinforced silicon carbide (SiC f /SiC) ceramic matrix composites. The critical role of the interphase as a key transitional layer between the fiber and the matrix is elucidated, specifically in regulating the interfacial bonding strength and enabling crack deflection to impart non-brittle fracture behavior to the composite. Typical interphase materials, represented by pyrolytic carbon and hexagonal boron nitride, are summarized. Furthermore, the advantages, limitations, and fabrication methods associated with various interphase design strategies, including weak interfaces, layered crystalline structures, composite multilayers, and porous architectures, are described. Predominant preparation techniques, such as chemical vapor deposition/infiltration and precursor pyrolysis conversion, are detailed. Additionally, micromechanical characterization techniques at the micro/nano scale, ranging from single-fiber push-out/push-in testing to micropillar compression testing, as well as microstructural and compositional analysis methods utilizing coupled instrumental approaches, are critically reviewed. The application of multiscale numerical simulations, primarily based on molecular dynamics and the finite element method, for revealing interfacial behavior and predicting performance is also discussed. Finally, the trend in interphase research is prospected, highlighting its evolution from a sole load-bearing function toward integrated structure-function capabilities. Notable recent advances in emerging areas, such as load-bearing integrated with electromagnetic property regulation, are emphasized. This review provides a significant reference for the rational design and tailored development of high-performance interphases in SiC f /SiC composites.