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In this study, a temperature‐dependent fracture strength model for whisker‐reinforced ceramic composites was developed. This model considers the strength degradation of both whisker and ceramic matrix at elevated temperatures, as well as the evolution of residual thermal stress with temperature. It was verified by comparison with the available flexural strengths of five types of whisker‐reinforced ceramic composites at different temperatures, and good agreement between the model predictions and the experimental data is obtained. Moreover, based on the established model, we systematically analyzed the effects of six influencing factors, including the volume fraction and the aspect ratio of whisker, the Young's modulus of matrix and whisker, the thermal expansion coefficient difference and the stress‐free temperature, on the temperature‐dependent flexural strengths of whisker‐reinforced ceramic composites. Some new insights which could help optimize and improve the temperature‐dependent fracture strength of whisker‐reinforced ceramic composites are obtained. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a temperature‐dependent model for predicting the tensile strength of 2D woven fiber reinforced ceramic matrix composites. The model takes into account the combined effects of temperature, temperature‐dependent residual thermal stress, temperature‐dependent matrix strength, and fibers strength on the tensile strength of composites. To verify the model, the tensile strengths of 2D woven fiber reinforced ceramic matrix composites available are predicted at different temperatures. The model predictions agree well with the experimental data. This work could provide a practical technical means for predicting the temperature‐dependent tensile strength of 2D woven fiber reinforced ceramic matrix composites and uncovering the dominated mechanisms leading to the change of tensile strength and their evolution with temperature. [ABSTRACT FROM AUTHOR]

In this paper, two physics-based temperature-dependent strength models for ceramic fibers were presented based on a critical failure energy density theory. These models included the combined effects of temperature, phase composition and oxidation on ceramic fiber strength. Good agreement between the model predictions and the experimental results was obtained. Based on the above models and the Cao and Thouless’s theory, a new temperature-dependent strength model for unidirectional ceramic fibers reinforced ceramic-matrix composites was developed. The good agreement between the predicted results and the experimental data fully validates the reasonability of this model. Compared with the Cao and Thouless’s model, the model is more practical and convenient to predict the temperature-dependent tensile strengths of the composites. The influencing factor analysis for ceramic fibers and their unidirectional composites were systematically conducted. Some new findings regarding their temperature-dependent tensile strengths were provided for the first time. [ABSTRACT FROM AUTHOR]

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]

Based on a kind of equivalence between heat energy and fracture energy, assuming that there is a constant maximum storage of energy that includes both heat energy and fracture energy, a new temperature dependent fracture surface energy model is developed. Using the new model and the classical ACK theory, a temperature dependent first matrix cracking stress model is obtained for the fiber reinforced ceramic composites. According to the model, the temperature dependent first matrix cracking stress of materials can be easily predicted using some basic material parameters such as matrix fracture surface energy and Young’s modulus. The model is verified by comparison with experimental data of SiC fiber reinforced reaction-bonded Si 3 N 4 composites at different temperatures. Good agreement is obtained between predicted and experimental data of first matrix cracking stress. The dependency of first matrix cracking stress on fracture surface energy and interfacial shear strength is systematically analyzed. [ABSTRACT FROM AUTHOR]

In this paper, based on a temperature-dependent fracture strength model and the theory of composite materials, two temperature-dependent fracture strength models for unidirectional and short random fiber reinforced ceramic matrix composites are developed. The effects of temperature, fiber content, fiber distribution, and matrix strength on the strength of fiber-reinforced ceramic matrix composites are included in the models. Furthermore, considering the effects of oxidation reaction for some kinds of fiber and size effect of unidirectional fiber on the strength of composites, a new temperature-dependent fracture strength model considering size effect and oxidation of reinforcing fiber is established. And good agreement between model predictions and experimental data indicates the applicability and rationality of our models. So the models can be used to predict the temperature-dependent fracture strength of fiber-reinforced ceramic matrix composites. [ABSTRACT FROM AUTHOR]