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Steve G. Roberts - One of the best experts on this subject based on the ideXlab platform.

  • Microstructure and mechanical properties of cubic zirconia (8YSZ)/SiC nanocomposites
    Journal of The European Ceramic Society, 2000
    Co-Authors: Lise Donzel, Steve G. Roberts
    Abstract:

    Abstract The mechanical properties of cubic zirconia (8YSZ)/SiC “nanocomposites” were studied. These properties were found to be strongly dependent on the microstructure and processing conditions. For nanocomposites with SiC particles mostly inside the zirconia grains the bending strength, toughness and hardness were similar to that of monolithic 8YSZ. For nanocomposites with SiC particles located mainly on the grain boundaries, an improvement of the strength and an increase of the toughness were observed. The increase in strength is strongest at room temperature and decreases with rising temperature; the strengths of all materials are identical at ∼750°C. The higher strength cannot be completely accounted for by the observed increase in toughness, implying a reduced Critical Flaw Size in the stronger material.

  • Microstructure and mechanical properties of cubic zirconia (8YSZ)/SiC nanocomposites
    Journal of the European Ceramic Society, 2000
    Co-Authors: Lise Donzel, Steve G. Roberts
    Abstract:

    The mechanical properties of cubic zirconia (8YSZ)/SiC 'nanocomposites' were studied. These properties were found to be strongly dependent on the microstructure and processing conditions. For nanocomposites with SiC particles mostly inside the zirconia grains the bending strength, toughness and hardness were similar to that of monolithic 8YSZ. For nanocomposites with SiC particles located mainly on the grain boundaries, an improvement of the strength and an increase of the toughness were observed. The increase in strength is strongest at room temperature and decreases with rising temperature; the strengths of all materials are identical at ~750°C. The higher strength cannot be completely accounted for by the observed increase in toughness, implying a reduced Critical Flaw Size in the stronger material. (C) 2000 Elsevier Science Ltd. All rights reserved

Lise Donzel - One of the best experts on this subject based on the ideXlab platform.

  • Microstructure and mechanical properties of cubic zirconia (8YSZ)/SiC nanocomposites
    Journal of The European Ceramic Society, 2000
    Co-Authors: Lise Donzel, Steve G. Roberts
    Abstract:

    Abstract The mechanical properties of cubic zirconia (8YSZ)/SiC “nanocomposites” were studied. These properties were found to be strongly dependent on the microstructure and processing conditions. For nanocomposites with SiC particles mostly inside the zirconia grains the bending strength, toughness and hardness were similar to that of monolithic 8YSZ. For nanocomposites with SiC particles located mainly on the grain boundaries, an improvement of the strength and an increase of the toughness were observed. The increase in strength is strongest at room temperature and decreases with rising temperature; the strengths of all materials are identical at ∼750°C. The higher strength cannot be completely accounted for by the observed increase in toughness, implying a reduced Critical Flaw Size in the stronger material.

  • Microstructure and mechanical properties of cubic zirconia (8YSZ)/SiC nanocomposites
    Journal of the European Ceramic Society, 2000
    Co-Authors: Lise Donzel, Steve G. Roberts
    Abstract:

    The mechanical properties of cubic zirconia (8YSZ)/SiC 'nanocomposites' were studied. These properties were found to be strongly dependent on the microstructure and processing conditions. For nanocomposites with SiC particles mostly inside the zirconia grains the bending strength, toughness and hardness were similar to that of monolithic 8YSZ. For nanocomposites with SiC particles located mainly on the grain boundaries, an improvement of the strength and an increase of the toughness were observed. The increase in strength is strongest at room temperature and decreases with rising temperature; the strengths of all materials are identical at ~750°C. The higher strength cannot be completely accounted for by the observed increase in toughness, implying a reduced Critical Flaw Size in the stronger material. (C) 2000 Elsevier Science Ltd. All rights reserved

Il -mo Sung - One of the best experts on this subject based on the ideXlab platform.

  • Fractographic analysis of vitreous calcia-alumina eutectic fibres produced by inviscid melt spinning (IMS)
    Journal of Materials Science, 1996
    Co-Authors: Yun Mo Sung, Il -mo Sung
    Abstract:

    The mechanical properties of inviscid melt spun (IMS) CaO-Al_2O_3 (46.5 wt % CaO-53.5 wt % Al_2O_3) eutectic fibres were examined by fractographic analysis as well as four-point bending and micro-indentation. The averaged fracture strength and elastic modulus values of the IMS Calcia-Alumina (CA) fibre were determined to be 460 MPa and 99.8 GPa, respectively by using four-point bending tests. The inner mirror constant ( M ) was determined to be 2.39 MPa·m^1/2 by using the plot of the fracture strength (σ_f) obtained from the bending tests as a function of r ^−1/2, where r is the inner mirror radius measured from scanning electron microscopy (SEM) on the fractured CA fibres. The Flaw-to-mirror ratio ( c/r ) for the CA fibre was calculated to be 1∶11.24. Also, the Critical Flaw Size ( c ) of the CA fibre was estimated to be 2.35 μm. The averaged elastic modulus value from Knoop micro-indentation was determined to be 102.5 GPa which is in good agreement with that from the four-point bending tests.

  • Fractographic analysis of vitreous calcia-alumina eutectic fibres produced by inviscid melt spinning (IMS)
    Journal of Materials Science, 1996
    Co-Authors: Yun Mo Sung, Il -mo Sung
    Abstract:

    The mechanical properties of inviscid melt spun (IMS) CaO-Al_2O_3 (46.5 wt % CaO-53.5 wt % Al_2O_3) eutectic fibres were examined by fractographic analysis as well as four-point bending and micro-indentation. The averaged fracture strength and elastic modulus values of the IMS Calcia-Alumina (CA) fibre were determined to be 460 MPa and 99.8 GPa, respectively by using four-point bending tests. The inner mirror constant ( M ) was determined to be 2.39 MPa·m^1/2 by using the plot of the fracture strength (σ_f) obtained from the bending tests as a function of r ^−1/2, where r is the inner mirror radius measured from scanning electron microscopy (SEM) on the fractured CA fibres. The Flaw-to-mirror ratio ( c/r ) for the CA fibre was calculated to be 1∶11.24. Also, the Critical Flaw Size ( c ) of the CA fibre was estimated to be 2.35 μm. The averaged elastic modulus value from Knoop micro-indentation was determined to be 102.5 GPa which is in good agreement with that from the four-point bending tests.

R. Stevens - One of the best experts on this subject based on the ideXlab platform.

  • The influence of whisker dimensions on the mechanical properties of cordierite/SiC whisker composites
    Journal of the European Ceramic Society, 1992
    Co-Authors: I. Wadsworth, R. Stevens
    Abstract:

    Abstract Three batches of silicon carbide whiskers of different, but known, dimensions have been incorporated into a cordierite matrix. It was found that the aspect ratio of the whiskers and their physical Size had a significant effect on the mechanical properties of the composites they constituted. Fracture toughness was governed by the relative contributions of the mechanisms of crack deflection, crack bridging and load transfer (pullout was not observed to occur in this system under the conditions used). Fracture strength was determined by the net, opposing, effects of an increase in fracture toughness and an increase in Critical Flaw Size of the composites.

  • Strengthening and toughening of cordierite by the addition of silicon carbide whiskers, platelets and particles
    Journal of Materials Science, 1991
    Co-Authors: I. Wadsworth, R. Stevens
    Abstract:

    Cordierite containing silicon carbide of different morphologies has been fabricated to produce composites with superior properties to the unreinforced cordierite. It has been demonstrated that the morphology of the silicon carbide affects the densification and the mechanical properties of the composites they constitute. The densification process was controlled by the degree of mutual contact of the silicon carbide phase within the cordierite matrix and by the rigidity of the resulting networks. The operative toughening mechanisms and their relative contributions were also dependent on the morphology of the silicon carbide. Fracture strength of the composites was governed by the relative contributions of an improvement in fracture toughness and by the magnitude of the Critical Flaw Size.

Ruzhuan Wang - One of the best experts on this subject based on the ideXlab platform.

  • Temperature dependence of the fracture strength of porous ceramic materials
    Ceramics International, 2020
    Co-Authors: Ruzhuan Wang, Shu Wang, Chuanzeng Zhang
    Abstract:

    Abstract In spite of the extensive use of porous ceramic materials in high-temperature applications, there are very few experimental and no theoretical studies on analyzing their temperature-dependent fracture behavior. In this work, in order to fill this research gap, a novel theoretical model for the characterization of fracture strength of porous ceramic materials with respect to temperature is proposed. The model considers the effects of the Young's modulus, specific heat capacity, volume fraction of pores, Sizes of pore and Flaw (Critical Flaw Size). Further, through simplification the model can be used for the characterization of the strength of the dense ceramic materials. The models are verified by the obtained excellent agreements between the predictions and measurements. The experimentally observed phenomena are analyzed and explained according to the predicted results. Our analysis indicates that the temperature dependence of the fracture strength of the porous ceramic materials in vacuum is controlled by the Young's modulus and volume fraction of pores. While on high temperature oxidation the Critical Flaw Size with respect to temperature should be considered. Furthermore, the temperature dependence of the strength of the dense ceramics is governed by the Young's modulus.

  • A novel and convenient temperature dependent fracture strength model for the laminated ultra-high temperature ceramic composites
    Journal of Alloys and Compounds, 2019
    Co-Authors: Ruzhuan Wang, Xiaorong Wang
    Abstract:

    Abstract At present, no suitable and convenient model has been developed to predict variation tendencies of fracture strength of laminated ceramic composites with temperature. In this paper, a novel and quite simple temperature dependent fracture strength model for the laminated ultra-high temperature ceramic composites was developed based on energy theories–the Griffith energy criterion and a concept of energy storage capacity. The complicated problems of characterization of combined effects of temperature, change in Critical Flaw Size and laminated structure parameters on fracture strength are solved by using primary and simple method. The model prediction agreed well with the experimental value. The novel model can be used to determine both fracture strength and change in Critical Flaw Size of laminated composite at elevated temperature. It should be noted that the model has no any fitting parameter, which is an easy-to-use method for the engineering.

  • Temperature dependent fracture toughness of the particulate-reinforced ultra-high-temperature-ceramics considering effects of change in Critical Flaw Size and plastic power
    Composites Part B: Engineering, 2019
    Co-Authors: Ruzhuan Wang, Xiaorong Wang
    Abstract:

    Abstract The fracture toughness of particulate-reinforced ultra-high-temperature-ceramics changes but does not decrease by a constant gradient with the increase of temperature. The change in microstructure and the occurrence of brittle-ductile transition affect the fracture toughness of materials at high temperature. In this paper, a novel temperature dependent fracture toughness model for the particulate-reinforced ultra-high-temperature-ceramics was developed based on the Griffith energy theories and the concept of the maximum storage of energy associated with fracture. The effect of change in microstructure was considered by introducing a non-dimensional value, the ratio of Critical Flaw Sizes of materials at room temperature and high temperature. The effect of plastic power was included in the model. It should be noted that the model has no any fitting parameter and which only needs some basic material parameters such as Young's modulus and specific heat capacity. The predictions of the fracture toughness of the composites in argon or air agreed well with the experimental measurements.

  • Temperature and Critical Flaw Size evolution dependence of fracture strength of the concretes
    Theoretical and Applied Fracture Mechanics, 2018
    Co-Authors: Ruzhuan Wang
    Abstract:

    Abstract The fracture strength of concretes at elevated temperature has attracted increasing attention owing to the great risk of exposing them to elevated temperatures. However, there are few theoretical studies on high temperature fracture strength of the concretes. In this paper, a novel and simple temperature dependent fracture strength model for the concretes was developed by using the Griffith energy method and a concept of energy storage capacity. The effect of Critical Flaw Size evolution is considered by this temperature dependent model based on primary and simple method. It should be noted that this model has no any fitting parameter and can be used simply just with some basic material parameters which have the clear physical meaning. Excellent agreement was achieved between model prediction and experimental measurement.

  • A Theoretical Model for Predicting Fracture Strength and Critical Flaw Size of the ZrB 2 -ZrC Composites at High Temperatures
    Applied Composite Materials, 2017
    Co-Authors: Ruzhuan Wang, Li Xiaobo, Jing Wang, Bi Jia
    Abstract:

    This work shows a new rational theoretical model for quantitatively predicting fracture strength and Critical Flaw Size of the ZrB2-ZrC composites at different temperatures, which is based on a new proposed temperature dependent fracture surface energy model and the Griffith criterion. The fracture model takes into account the combined effects of temperature and damage terms (surface Flaws and internal Flaws) with no any fitting parameters. The predictions of fracture strength and Critical Flaw Size of the ZrB2-ZrC composites at high temperatures agree well with experimental data. Then using the theoretical method, the improvement and design of materials are proposed. The proposed model can be used to predict the fracture strength, find the Critical Flaw and study the effects of microstructures on the fracture mechanism of the ZrB2-ZrC composites at high temperatures, which thus could become a potential convenient, practical and economical technical means for predicting fracture properties and material design.