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Based on fracture mechanics theory and a temperature-dependent interfacial shear strength model established by the authors, this paper develops a temperature-dependent theoretical model for the non-steady state first matrix cracking stress of fiber ceramic matrix composites. The model unifies the combined effects of temperature, crack length and thermal residual stress on the first matrix cracking stress into a single theory. The model predictions for the first matrix cracking stress of silicon carbide fiber reinforced zircon matrix composite agree well with the experimental results. Compared with the classical models proposed by Danchaivijit and Shetty, Thouless and Evans, and Marshall et al., our model has obvious advantages from the aspects of applicability, convenience and accuracy. Moreover, the analysis of influencing factors for the first matrix cracking stress is conducted systematically. Some new insights into improving the first matrix cracking stress of fiber ceramic matrix composites are obtained. [ABSTRACT FROM AUTHOR]

In this study, the temperature-dependent antiphase boundary energy is established from a view of energy conservation. Subsequently, a theoretical model for yield strength anomaly of Ni-base superalloys at elevated temperature is developed on the basis of pre-existing yield strength model and traditional precipitation strengthening theories. The model is verified at different temperatures by comparison with experimental data of several Ni-base superalloys. The excellent agreement between predictions and experiments shows a good prediction ability of this model. This study provides a quantitatively theoretical characterization method for yield strength anomaly of Ni-base superalloys at elevated temperature. [ABSTRACT FROM AUTHOR]