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As a promising high‐temperature material, MAX phases have attracted much attention owing to their combined merits of metals and ceramics. In this study, a temperature‐dependent analytical model for prediction of the strength of MAX phases considering high‐temperature oxidation and plastic deformation was proposed. A relationship among the strength, Young's modulus, strain‐hardening exponent, crack size, and temperature was established. The accuracy of the model was verified by a comparison between the model predictions and available experimental data. The proposed analytical model can provide a straightforward and effective way to predict the strength of MAX phases over a wide range of temperatures. Moreover, the quantitative effects of oxidation time, strain‐hardening exponent, and Young's modulus on the strength, as well as their evolution with temperature, were analyzed. The findings of this study would be useful for the high‐temperature strength prediction and design of MAX phase materials. [ABSTRACT FROM AUTHOR]

With the rapid development of aerospace technology, the application of fiber/polymer composites in extreme environments especially at high temperature gets more and more extensive, the tensile properties of fiber/polymer composites in different temperatures environment have become a critical issue of concern. In this work, a temperature and damage dependent tensile strength (TDDTS) model for fiber/polymer composites was presented based on the force‐heat equivalence energy density principle and the damage failure analysis. The TDDTS model considers the combined effects of temperature, the evolution of constituents' properties and damage with temperature. Meanwhile, the TDDTS model has advantages from the aspects of prediction accuracy and convenience by comparison with our previous model and the Curtin's model. Further on, the influencing factors analysis of fiber/polymer composites concerning the tensile properties and damage evolution with temperature was conducted. This study offers a reliable model for predicting the TDDTS of fiber/polymer composites, and provides important insight for the strength degradation mechanism and the damage evolution. [ABSTRACT FROM AUTHOR]

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]

In this work, a simple hand lay‐up technique was employed to fabricate bamboo fiber reinforced epoxy resin composites, and subsequently composites with different fiber volume fractions (0%, 30%, 50%, and 70%) were prepared. To investigate the composite thermal properties, differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, and dynamic mechanical analysis (DMA) were used. DSC demonstrates a decrease of glass transition temperature when fibers are incorporated into epoxy resin. TG results reveal that the degradation temperature increases with increasing the fiber content, and then a better thermal stability is achieved. The thermal results indicate that bamboo fibers provide a good resistance for heat insulation, suppressing the epoxy thermal decomposition. DMA shows that both storage modulus and loss modulus increase with increasing the fiber volume fraction in the temperature range of 30–200°C. Tensile tests and scanning electron microscopy (SEM) were also conducted on the specimens to investigate the material mechanical behavior. Compared with epoxy resin, the composites incorporated with bamboo fibers exhibit an improved tensile strength and modulus. The detailed analysis reveals that bamboo fibers have a positive effect on the thermo‐mechanical properties of epoxy resin, providing a feasibility to using natural composites in a specific construction. POLYM. COMPOS., 40:3929–3937, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

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]

Tensile strength is a key mechanical property of fibers used as sustainable reinforcements for advanced fiberreinforced composites. This study aims to conduct experimental investigation on the fracture strength of bamboo fibers of different dimensions subjected to longitudinal tensile loading. The statistical distributions of the fracture strength in bamboo fibers are correlated with the effects of fiber length and diameter variation. These are described according to Weibull statistics, which exhibit the random nature of fiber strength. The Weibull function parameters used for strength prediction are obtained from the test specimens. A comparison of predicted results and experimental data is presented to assess the accuracy of using weak-link scaling. Furthermore, the findings of this study also indicate that fiber strength statistics dominate size dependence of tensile strength. [ABSTRACT FROM AUTHOR]

The stress transfer from broken to its unbroken adjacent neighboring fibers in unidirectional fibrous composites under a tensile loading applied in the fiber axis is analyzed using a two-dimensional (2D) shear lag model. The numerical solutions to the governing equations is greatly simplified by the assumptions that the displacements perpendicular to the fiber direction can be ignored, and the axial displacements are uniform over the cross section of any fiber. Using an influence function superimposition technique, closed-form analytical expressions are used to predict stress profiles in both the fiber and matrix because of any number and arbitrary array of fiber breaks in the presence of matrix shear failure. These are compared to stress concentrations predicted using the finite element analysis (FEA). It is shown that the 2D modeling presented here does generalize the governing equations to include interactions with multiple damage events. The micromechanical model is vital to develop the basic mechanics that are necessary to understand failure behavior of the composite produced by the failure of one or more of its components. POLYM. COMPOS., 2013 © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this study, a temperature‐dependent bulk modulus model without any adjustable parameters for solids single crystals is developed based on an equivalent relation between deformation energy and heat energy. This model uncovers the quantitative relation between the temperature‐dependent bulk modulus, heat capacity, boiling point, enthalpy of solid‐state phase transition, enthalpy of fusion, enthalpy of vaporization, and volume coefficient of thermal expansion. As examples, the temperature‐dependent adiabatic bulk moduli of α‐Al2O3, MgO, Si, Ti, SrF2, CaF2, and MgF2 are predicted, and are in good agreement with the available experimental results. This study provides a new and practical method to quantitatively characterize the temperature‐dependent bulk modulus of solid single crystals. A temperature‐dependent bulk modulus model without any adjustable parameters is developed for solids single crystals. The quantitative relation between the temperature‐dependent bulk modulus and heat capacity, boiling point, enthalpy of solid‐state phase transition, enthalpy of fusion, enthalpy of vaporization, and volume coefficient of thermal expansion is found. This study can help to quantitatively characterize their temperature‐dependent bulk modulus. [ABSTRACT FROM AUTHOR]