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A temperature dependent fracture toughness model for whisker‐reinforced ceramic matrix composites was developed in this study, which considers the effects of matrix fracture toughness, residual thermal stress, crack bridging, crack deflection, and their temperature dependence. Its predicted results were compared with the fracture toughness of six types of whisker‐reinforced ceramic matrix composites at different temperatures, and good agreement between predicted results and experimental results is obtained. Furthermore, based on this model, we systematically analyzed the effects of the volume fraction and aspect ratio of whisker, Young's modulus of matrix and whisker, thermal expansion coefficient difference, stress‐free temperature, the ratio between the fracture energy of matrix and that of interface, on their temperature dependent fracture toughness for the first time. Finally, insights and suggestions which could help to optimize and improve the composite fracture toughness at different temperatures are provided. [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]

A novel temperature-dependent fracture strength model for ceramic materials is developed, based on a critical fracture energy density associated with material fracture comprising strain energy, the corresponding equivalent potential energy, and kinetic energy of atoms per unit volume. It relates the fracture strength at high temperatures to that at the reference temperature, the temperature-dependent Young’s modulus, the temperature, and the melting point. The model is verified by comparison with experimental data of ceramic materials. The model predictions and the experimental data are in excellent agreement with each other. As the Young’s modulus can easily be obtained by experiments and the melting point can easily be obtained by materials handbook, the model can easily predict the fracture strength of ceramic materials at arbitrary temperatures. [ABSTRACT FROM AUTHOR]

Abstract Based on the maximum storage energy density criterion of material fracture, a model of temperature-dependent fracture strength for ultra-high temperature ceramic composites is established. The combined impacts of the evolution of damage and thermal residual stress with temperature are considered. The model predictions are highly consistent with available experimental values. Besides, the critical crack sizes of ZrB 2 –30 vol%SiC in air from 1400 to 1600 °C are predicted using the proposed model, which agree well with the total oxidation thickness of the reported literature at 1400 and 1500 °C, and a more reasonable definition of critical crack size at 1600 °C are given. Moreover, the quantitative effect of crack size on the fracture strength is analyzed under different environment temperature, and a useful conclusion is obtained that decreasing crack size is more effective to improve the fracture strength of the composites at low temperatures. This study not only provides a feasible and convenient method to predict the fracture strengths at different temperatures, but also offers a theoretical support for the design of ultra-high temperature ceramic composites. [ABSTRACT FROM AUTHOR]

Abstract The combined effects of temperature, fiber debonding and residual thermal stress on the first matrix cracking stress for fiber reinforced ceramic matrix composites were investigated. We analyzed the temperature-dependent stress fields in the fiber and matrix by using the modified shear-lag model, and developed a temperature-dependent interface debonding criterion. Then, based on the energy balance approach, a temperature-dependent first matrix cracking stress model considering the effects of fiber debonding and residual thermal stress was established. The model predictions were compared with the available experimental results, which shows good agreement between the theoretical predictions and experimental results. Moreover, the quantitative effects of fiber volume fraction, interface debonded energy and interface frictional shear stress on the first matrix cracking stress and fiber debonding length were analyzed in detail at different temperatures. This work not only helps understand the matrix cracking behavior of fiber reinforced ceramic matrix composites with general interfacial properties at high temperatures, but also provides a guidance for the material design. [ABSTRACT FROM AUTHOR]