A physics-based theoretical prediction model for high-temperature strength of SiC fibers

Due to their exceptional high-temperature properties, oxidation resistance, and radiation tolerance, SiC fibers have become ideal reinforcing materials for advanced ceramic matrix composites (CMCs). As the main load-bearing constituent, their strength degradation governs the mechanical properties and service life of CMCs under elevated temperatures. However, the corresponding theoretical work is far behind of experimental research. To quantitatively describe the strength evolution in thermo-mechanical-oxidative coupled environments, this study abandons conventional empirical fitting formulas and develops a physics-based theoretical model for the high-temperature strength of SiC fibers by integrating Li’s Principle of Energy Equivalence, the D–G model, Griffith fracture theory, and the Hall–Petch relationship. The model systematically incorporates key factors governing strength-including temperature, high-temperature oxidation, grain growth, and residual thermal stress and requires only easily accessible material parameters. It was validated against extensive experimental data on both high-temperature real-time strength and residual strength after heat treatment of multiple types of SiC fibers, demonstrates good agreement between predictions and experiments over a broad temperature range. Furthermore, the influencing factors analysis regarding the evolution of fracture strength with oxidation temperature/time, Young’s modulus, and grain size are performed. The proposed model not only enhances insight into the failure mechanisms of SiC fibers in multi-field environments but also offers an efficient and practical theoretical tool for predicting their high-temperature strength.