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Rationale: Studies have shown the potential neuroprotective effect of xanthohumol, while whether xanthohumol has the ability of repairing cognitive impairment and its underlying mechanism still remains obscure. Objectives: To unravel the mechanism of xanthohumol repairing cognitive impairment caused by estrogen deprivation. Methods: C57BL/6 J female mice that underwent bilateral ovariectomy to establish cognitive decline model were randomly divided into three xanthohumol-treated groups and a saline-treated model group. For identifying the neuroprotective function of xanthohumol, Morris water maze (MWM) test and open field test (OFT) were conducted. After extracting total RNA of mouse hippocampus of different groups, mRNA-seq and microRNA (miRNA)-seq analysis were performed, and the differentially expressed miRNAs (DEMIs) and their target genes were further validated by qPCR. MiR-532-3p and its downstream gene Mpped1 were screened as targets of xanthohumol. Influence of miR-532-3p/Mpped1 to cognitive ability was examined via MWM test and OFT after stereotactic brain injection of Mpped1 overexpressed adeno-associated virus. The regulation of miR-532-3p on Mpped1 was confirmed in hippocampal neuronal cell line HT22 by luciferase reporter gene assay. Results: Xanthohumol treatment reversed the cognitive decline of OVX mice according to behavioral tests. By comparing miRNA levels of xanthohumol-treated groups with saline-treated group, we found that the main changed miRNAs were miR-122-5p, miR-532-3p, and miR-539-3p. Increased miR-532-3p in OVX mice was suppressed by xanthohumol treatment. Furthermore, the downstream gene of miR-532-3p, Mpped1, was also increased by xanthohumol and showed the capability of relieving cognitive impairment of OVX mice after overexpressed in hippocampus. The 3′ untranslated region of Mpped1 was identified as the target region of miR-532-3p, and agomiR-532-3p remarkably reduced the expression of Mpped1 mRNA. Conclusions: Xanthohumol has the ability of repairing cognitive impairment through removing the inhibition of miR-532-3p on Mpped1 in mouse hippocampus. This finding not only advances the understanding of neuroprotective mechanism of xanthohumol, but also provides novel treatment targets for dementia of postmenopausal women. [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 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]

In this paper, based on our previous study regarding the temperature-dependent yield strength for metallic materials and the existing strengthening theories, a physics-based temperature dependent compressive yield strength model for short fiber reinforced magnesium alloy matrix composites was developed. This model was verified by comparison with the experimental data of seven types of magnesium alloy matrix composites. Good agreement between the model predictions and the experimental data was obtained, which fully validates the reasonability of the present model. Moreover, based on the model and the existing material parameters, the influencing factor analysis for short fiber reinforced magnesium alloy matrix composites was systematically conducted. Some novel insights regarding the control mechanism of their temperature dependent compressive yield strengths were provided. [ABSTRACT FROM AUTHOR]

In this paper, based on the Griffith fracture theory, the slow crack growth theory and the temperature-dependent fracture surface energy model, a temperature and test rate dependent fracture strength model for zirconia and alumina single crystal fibers was established. As a comparison, the other one based on the temperature-dependent free surface energy was also deduced and discussed. These models were verified by comparison with the experimental data of the two types of ceramic single crystal fibers. Good agreement between the model predictions and the experimental data was obtained. Moreover, based on the present model and the existing material parameters, the influencing factor analysis for these ceramic single crystal fibers were systematically conducted. Some new findings regarding their high temperature fracture strengths were provided for the first time. [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]

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]

Tensile strength of brittle fibres exhibits statistical distribution and size dependence. In this work, the average strength of bamboo fibre is found to decrease from 568 to 483 MPa as mean diameter increases from 196.6 to 584.3 μm. The morphologies of bamboo fibres with increasing diameters were investigated through Scanning Electron Microscopy (SEM) to demonstrate variations in the quantity of elementary fibres. The influence of elementary fibre distributions on the fibre strength was also studied. A modified Weibull model based on number of elementary fibres is proposed to perform scaling predictions for the fracture strength of the fibres at different between-fibre diameters. It was shown that the predicted results are in reasonable agreement with experimental data, highlighting the adequacies of the new analytical model for describing the diameter dependence of tensile strength. [ABSTRACT FROM AUTHOR]

In this study, the effect of strain rate on the mechanical behavior of B. mori silk, A. assama silk, A. pernyi silk and A. ventricosus spider silk were systematically investigated. Dynamic tensile tests were conducted for these natural silk fibers to obtain their mechanical properties under five strain rates. Tensile test results indicated that the stiffness, tensile strength, failure strain and rupture energy of A. ventricosus spider silk all increase with increasing strain rates. A. ventricosus spider silk was found to have the highest average Weibull modulus among these silk fibers, showing its excellent reliability. Then, based on Zener model and Weibull statistics, this study theoretically characterized and analyzed the influence of strain rate on their mechanical properties including stress-strain responses, tensile strengths, Weibull parameters, failure strains and rupture energies. Some insights that can be helpful for better understanding their strain rate dependent mechanical behavior were provided. Unlabelled Image • Strain rate dependent mechanical properties of different silk fibers were experimentally investigated. • Theoretical characterizations on their strain rate dependent mechanical properties were developed. • Insights on better understanding their strain rate dependent mechanical behaviors were provided. [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]

Abstract In this study, the stress distribution of fiber axial stress and interfacial shear stress in fiber reinforced polymer (FRP) composites at different temperatures was derived as a function of fiber axial position. The maximum shear stress criterion was extended to be temperature dependent. Based on the extended criterion, the temperature dependent fiber debonding length of FRP composites was predicted, which is indirectly verified by other scholar's experimental study. Then, by introducing the maximum fiber axial stress transferred from the matrix to fiber by their interface including the effect of partial interfacial debonding, we modified the law of mixtures, and finally established the temperature dependent tensile strength model for FRP composites. The model considers the combined effects of temperature, constituents' properties, interfacial properties and residual thermal stress. Reasonable agreement is obtained between the model predictions and available temperature dependent tensile strength of FRP composites. Additionally, the influencing factors analysis for FRP composites is performed in detail. This work provides some important insights on the strength control mechanisms of FRP composites at different temperatures, which are beneficial to the material evaluation, strengthening, and optimization. [ABSTRACT FROM AUTHOR]

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]

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 limited energy storage viewpoint proposed by our team, it is assumed that there is a maximum constant value for the maximum storage of energy per unit volume when dislocation slip starts in a metal. A temperature-dependent critical resolved shear stress (CRSS) model without any fitting parameters is developed for metals in a pure shear mode. The CRSSs of Cu, Cu–Au, Cu–Co and Cu–Au–Co in the pure shear mode are predicted, and are in excellent agreement with the experimental results. This work offers an approach to predict the temperature-dependent CRSS for metals in the pure shear mode. [ABSTRACT FROM PUBLISHER]

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]

In this study, we report a theoretical model for the temperature and size dependent surface energy of metallic nanomaterials. The model is verified by making a comparison with the available simulation and experimental data. Reasonable agreement has been observed between these results. This study reveals that the decrease of surface energy at high temperatures is caused by cohesive energy weakening and bond expansion. With the same nanomaterial size, the sequence of size effects on the surface energy from weak to strong is thin films, nanowires, and nanoparticles. In particular, this work can provide a theoretical basis for the prediction of size dependent surface energy of metallic nanomaterials at different temperatures, which can help in the understanding of the mechanical and thermodynamic properties of metal surfaces. [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]

Background and Purpose: Increased high-mobility group box 1 (HMGB1) levels were found in patients after acute ischemic stroke. The aim of this study was to examine whether the circulating HMGB1 levels could predict the 3-month post-stroke depression (PSD).Methods: The subjects were first-ever ischemic stroke patients who were hospitalized during the period from July 2020 to December 2020. HMGB1 concentrations were measured by enzyme-linked immunosorbent assay after admission. A 24-item Hamilton Depression Rating Scale was performed to evaluate PSD at 3 months after stroke.Results: The analyses included 324 participants (mean age, 63.7 years; 171 male). Ninety-four patients (29.0%) were diagnosed as having PSD at 3 months. The median serum HMGB1 levels at admission was 7.5 ng/mL (IQR, 4.4-11.3 ng/mL). The PSD distribution across the HMGB1 quartiles ranged between 17.5% (first quartile) and 57.5% (fourth quartile). After covariate adjustments, the fourth quartile of HMGB1 was found to be associated with a higher risk of PSD (as compared with first HMGB1 quartile, odd ratio, 1.26; 95% confidence interval [CI], 1.17-1.35; P < 0.001). The area under the receiver operating characteristic curve of HMGB1 was 0.726 (95% CI 0.660-0.792) for PSD. Similar results were found when HMGB1 was analyzed as continuous variable. Furthermore, the optimal cutoff point of circulating HMGB1 levels was 8.6 ng/mL, with a sensitivity of 69.2% and a specificity of 73.9%.Conclusions: This study demonstrated that higher HMGB1 levels in the acute phase of ischemic stroke were associated with increased risk of PSD. [ABSTRACT FROM AUTHOR]

In contemporary developments across automotive, aerospace, and military industries, there is an ever-growing demand for lightweight and robust polymer composites. In this study, a ductile epoxy resin, carbon nanotubes (CNTs), cellulose nanofibers (CNFs), and silica nanoparticles were used to fabricate nano-fillers/epoxy composites and nano-fillers/silk fibers/epoxy hybrid composites through solution casting and hot pressing. Their mechanical properties and thermal characteristics were analyzed and compared, which show that: these nano-fillers can dramatically enhance the strength and stiffness of the ductile epoxy resin; however, this is achieved at the expense of its toughness and extensibility. CNT/silk fiber/epoxy hybrid composite has the highest tensile strength (81.10 MPa), Young's modulus (3.76 GPa) and impact strength (103.7 kJ/m2), while the CNFs-reinforced one exhibits the highest breaking energy (9.96 MJ/m3). These nano-fillers almost do not affect the thermal stability of the epoxy resin and silk fiber composites. In addition, the fracture modes of their reinforced composites were revealed by macroscopic and microscopic observations. • Reveal how different nano-fillers affect the mechanical behaviors of ductile polymer matrix. • Explore the optimal content of these nano-fillers in the polymer matrix. • Indicate nano-fillers do not affect the thermal stability of their reinforced composites. • Elucidate the composites' fracture modes introduced by silk fibers and different nano-fillers. [ABSTRACT FROM AUTHOR]

Knowledge of vacancy formation energy (VFE) for metallic materials at different temperatures is of fundamental importance. In the present study, following Brook's method and cohesive energy theory, two temperature dependent VFE models of metallic materials are developed based on our previous studies. The developed models are validated using the available experimental and simulation results. Agreement is good between model predictions and corresponding available experimental and simulation results. This study indicates that the VFE firstly remains approximately constant and then goes down almost linearly with increase of temperature. Furthermore, this work can provide simple and effective methods to calculate VFE of metallic materials at different temperatures, and can help understand the fundamental mechanisms which control the decrease of VFE at high temperatures. [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]

Highlights • A new strength criterion is proposed for BMGs for the whole range of stress states. • A temperature dependent compressive strength model is established for BMGs. • The tension-compression asymmetry can be characterized well by the new criterion. • The temperature dependent tensile fracture angle can be explained by the new criterion. Abstract In this paper, the different fracture mechanisms of bulk metallic glasses in tension and compression are investigated through combining its macroscopic fracture behaviors and unique atomic structure. It is found that the compressive fracture process of metallic glasses should be mainly controlled by the shear progress. In addition, both local shear process and local quasi-cleavage will happen under tensile loading due to the normal stress. Based on the analysis, a new strength criterion is proposed for metallic glasses from the viewpoint of energy, which is suitable for the whole range of stress states. The proposed criterion can give a good description of the experiment data of Zr-based metallic glasses in a wide normal stress range. Moreover, a temperature dependent compressive strength model is established based on the temperature dependent shear modulus model and the proposed strength criterion. The temperature dependence of tensile fracture angle can also be explained reasonably by the new criterion. [ABSTRACT FROM AUTHOR]

Abstract For describing the temperature-dependent yield strength (TDYS) of precipitation strengthening Ni-base superalloys, a temperature-dependent model of Anti-Phase Boundary (APB) energy was developed in this study firstly. And then combining the proposed temperature-dependent APB energy model with the classical particle shearing theory, two temperature-dependent critical resolved shear stress models were developed for the weak and strong coupled dislocation pairs, respectively. Furthermore, the transition of dislocation motion mode from shearing to by-passing with increasing temperature was described theoretically by defining a temperature-dependent probability function of by-passed precipitate particles. In this way, a TDYS model for precipitation strengthening Ni-base superalloys was developed. The model contains the contributions of the precipitates, the grain boundary, the solid solution and the base metal at different temperatures, and their corresponding variations of the strengthening mechanisms with temperature. Moreover, the TDYS of seven typical precipitation strengthening Ni-base superalloys was predicted, and good agreement is obtained between the predicted results and the experimental data. The contribution of each mechanism to TDYS with increasing temperature was analyzed in this study. It indicates that the transition of dislocation motion mode from shearing to by-passing with increasing temperature will weaken the high-temperature yield strength of precipitation strengthening superalloys. Both grain refinement and solid solution strengthening are effective methods to reduce the probability of transition from particle shearing to by-passing, which can help maintain the high-temperature yield strength of superalloys. Using the proposed TDYS model, the optimal precipitate size to achieve maximum strength at different temperatures was analyzed. As temperature increases, the optimal precipitate size of superalloys decreases. And the optimal precipitate size at the most dangerous service temperature of the alloy can be determined by our model when designing a new superalloy. Highlights • Quantitatively characterize the temperature-dependent anti-phase boundary energy. • Develop a temperature-dependent yield strength model for nickel-base superalloys. • Define a probability function of by-passed volume fraction of particles. • The optimal precipitate size at different temperatures is analyzed. [ABSTRACT FROM AUTHOR]

Abstract In this study, we report a temperature-dependent prediction model without arbitrary parameters for the coefficient of surface tension of homogeneous liquid, and then validate it by the available experimental data of fifteen kinds of pure liquids. Very small maximum deviation or absolute average deviation between predicted and experimental results has been obtained. The prediction model uncovers the inherent relationship between the coefficient of surface tension, boiling point, heat of evaporation, heat capacity, and coefficient of linear expansion. Furthermore, it reveals that the decrease of cohesion energy determines the decline of coefficient of surface tension and can analyze the variation of coefficient of surface tension with increasing temperature. Graphical abstract Image 1 Highlights • A new temperature-dependent surface tension prediction model is developed. • The model does not contain any arbitrary parameter. • The model correlates surface tension with certain thermophysical properties. • It reveals the law governing the variation of surface tension with temperature. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a theoretical model for predicting the longitudinal tensile strength of unidirectional fiber reinforced polymer (FRP) composites at different temperatures is established. This model considers the combined effects of temperature, matrix strength, fiber size, fiber volume fraction, and the fiber strength scatter on the tensile strength of unidirectional FRP composites. The model is verified by comparison with available experimental data of carbon fiber and glass fiber reinforced polymer composites at different temperatures. The agreement between the theoretical model and experimental results is found to be satisfactory, which indicates the applicability and reasonability of the model. Particularly, the model has advantages compared with Curtin's model, Gao-Reifsnider's (G-R's) model and Subramanian-Reifsnider's (S-R's) model from the aspects of accuracy and convenience. Furthermore, the influencing factor analysis for unidirectional FRP composites regarding their temperature dependent tensile strength was systematically conducted, which provide better understanding on the strength control mechanism and material design. [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]

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 study, a temperature-dependent longitudinal tensile strength model for short-fiber-reinforced polymer composites (SFRPCs) is established based on the sensitivities of thermal-physical properties of polymer materials to temperature and our previous work. The effects of temperature, fiber orientation distribution, fiber length distribution and residual thermal stress are considered in this model. The theoretical model is verified by comparison with tensile strength of glass SFRPCs at different temperatures. Good agreement between the model predictions and experimental results is obtained, which indicates the reasonability of the proposed models. Furthermore, the comparisons between the present models and the classical models are discussed, and the influencing factors analysis for SFRPCs is also conducted in detail. This study can not only provide a potential convenient means for predicting the temperature-dependent tensile strength of SFRPCs, but also offer useful suggestions for the material evaluation, strengthening and design. [ABSTRACT FROM AUTHOR]

This study reports new temperature-dependent yield strength models for solid solution strengthening binary and multi-component alloys. The models take into account the contributions of base metal, solid solution strengthening, and grain boundary strengthening at different temperatures. Comparisons for different Nickel-based alloys are made between experimental and predicted data with all parameters obtaining from literatures and handbooks and they are in good agreement in a wide range of temperature. This study points out that the yield strength of solid solution strengthening alloys is very sensitive to the lattice misfit. It is not suitable to cursorily estimate the lattice misfit by the atomic radius of solute and solvent. In addition, the variation with temperature of the contribution of each mechanism to the yield strength of solid solution strengthening Nickel-based alloys is firstly made in this study. The study also provides some useful suggestions to improve the temperature-dependent yield strength of solid solution strengthening Nickel-based alloys in the manufacturing. [ABSTRACT FROM AUTHOR]

In this study, a thermal shock resistance model over a wide range of cooling environment temperatures for fiber reinforced brittle matrix composites is developed. The model takes into account the combined effects of cooling environment temperature and temperature-dependent material parameters. The critical temperature difference causing matrix cracking of SiC fiber reinforced reaction bonded Si 3 N 4 composite and Nicalon fiber reinforced borosilicate composite are predicted over a wide range of cooling environment temperatures. The results show that the thermal shock resistance of composites is strongly dependent on the cooling environment temperature. Moreover, the quantitative influences of matrix Young's modulus, thermal expansion coefficient of matrix, and interfacial shear stress on thermal shock resistance with increase of cooling environment temperature are studied in detail. And some insights into improving the thermal shock resistance of fiber reinforced brittle matrix composites are obtained. [ABSTRACT FROM AUTHOR]

In this paper, a physics-based temperature dependent yield strength model for stainless steel is developed based on a kind of equivalence between the deformation energy and the heat energy. A critical yield energy which comprises the deformation energy and the corresponding heat energy is then introduced. Meanwhile, the nonlinear behavior of stainless steel before the yielding of materials and the effect of phase transition are considered in the theoretical model without any fitting parameters. These stainless steels studied in this paper are from European brands, Japanese brands and interior brands. Excellent agreement between the theoretical model predictions and the experimental results of austenitic stainless steel and ferritic stainless steel fully validates the reasonability of this model. The theoretical model is convenient and practical to predict the temperature dependent yield strength of stainless steel, which is expected to be applied for the appropriate assessment of fire resistance of stainless steel. [ABSTRACT FROM AUTHOR]

A model of temperature dependent shear modulus and Young's modulus in bulk metallic glasses is established. The inherent relationship between the glass transition temperatures, the Debye temperature and shear modulus of bulk metallic glasses is revealed. The temperature dependent shear modulus can be predicted by our model without any fitting parameter. The model is presented based on a critical energy density criterion for plastic yielding which is derived from fundamental thermodynamics. This critical energy density consists of two parts: the heat added to the system and the input of mechanical energy, which are not completely equivalent. The agreement between theoretical results and experimental results is striking. And it is found that the temperature dependent Young's modulus could also be predicted pretty well by our model. [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]

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 work, we proposed a novel temperature dependent yield strength model for metallic materials which has no fitting parameters. The temperature dependent yield strength at arbitrary temperatures can be predicted. And a critical yield energy density with material yield is introduced, which comprises the distortional strain energy, potential energy and kinetic energy of atomic motion. A kind of quantitative relationship between the yield strength, temperature, elastic modulus and Poisson’s ratio is presented. The agreement between theory and experiment is of good satisfaction. Moreover, a temperature dependent yield strength model considering the precipitation strengthening is introduced to predict the yield stress of precipitation strengthened superalloy. Based on the proposed temperature dependent model, a new temperature and strain rate dependent yield strength is established. The good agreement between theory and experiment is found at the temperatures and strain rates considered. [ABSTRACT FROM AUTHOR]

Mechanical shock often exists in quenching experiments and service processes of ceramic materials. In this study, a series of experiments are designed and developed to study the effects of mechanical shock on thermal shock behavior of ceramic materials. It indicates that the pattern and length of cracks on specimens are significantly affected by mechanical shock in quenching experiments. Furthermore, the existence of mechanical shock will affect the stress field in ceramic specimens, and then the evaluation of thermal shock resistance by critical rupture temperature difference as well as service performance of ceramics can be easily affected by mechanical shock. This study provides suggestions that mechanical shock in quenching tests should be avoided or considered to shed light on the actual thermal shock resistance of ceramic materials. [ABSTRACT FROM AUTHOR]

The tensile properties of superalloy GH4033 have been evaluated at temperatures ranging from room temperature to 1000 °C. Fracture surfaces and precipitation were observed using a field-emission scanning electron microscope (FE-SEM). The alloy mainly consisted of γ ’ precipitate particles homogeneously dispersed in the γ matrix interior. The effects of dynamic strain aging and precipitation on the strength were verified. A temperature-dependent yield strength model was developed to describe the temperature and precipitation effects on the alloy's yield behaviour. The model is able to consider the effect of precipitation strengthening on the yield strength. The yield behaviour of the precipitation-strengthened superalloy was demonstrated to be adequately predictable over a wide range of temperatures. Note that this model reflects the quantitative relationship between the yield strength of the precipitation-strengthened superalloy and the temperature, the elastic modulus, the specific heat capacity at constant pressure, Poisson's ratio, the precipitate particle size and the volume fraction of the particles. [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]

Topical use of antimicrobial agents to treat wounds to inhibit bacterial invasion and facilitate wound healing is an effective strategy. In this work, an antibacterial xerogel film for potential applications in wound dressings was developed. First, a natural antibacterial agent, quercetin (Qu), was made into water-soluble quercetin-borate (QuB) nanoparticles by merging a solvent exchange method with the borate esterification reaction. QuB nanoparticles were then employed as the cross-linking agent to achieve gelation of poly(vinyl alcohol) (PVA) to obtain antimicrobial QuB-PVA composite microgels. Furthermore, QuB-PVA microgels were utilized as raw materials to produce xerogel films via an electrospray technique. The as-prepared QuB-PVA xerogel films exhibited excellent bacteriostasis, antioxidation, biocompatibility, self-healing, accelerated skin regeneration and functional restoration, and promoted skin wound healing. The QuB-PVA films significantly facilitated the in vivo healing speed of full-thickness skin wounds compared to commercial dressings. We believe that the present multifunctional QuB-PVA xerogel film is an excellent candidate for the wound dressings. [Display omitted] • A QuB-PVA xerogel film was prepared as the bioactive wound dressing. • The QuB-PVA film possessed good antibacterial and antioxidant performances. • The QuB-PVA film exhibited excellent self-healing ability and low cell cytotoxicity. The QuB-PVA film could accelerate skin regeneration and promote skin wound healing. • The QuB-PVA film as the wound dressing has better effect compared to commercial film. [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]