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  • 1
    Electronic Resource
    Electronic Resource
    Interface Design for Oxidation-Resistant Ceramic Composites (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Fiber-reinforced ceramic composites achieve high toughness through distributed damage mechanisms. These mechanisms are dependent on matrix cracks deflecting into fiber/matrix interfacial debonding cracks. Oxidation resistance of the fiber coatings often used to enable crack deflection is an important limitation for long-term use in many applications. Research on alternative, mostly oxide, coatings for oxide and non-oxide composites is reviewed. Processing issues, such as fiber coatings and fiber strength degradation, are discussed. Mechanics work related to design of crack deflecting coatings is also reviewed, and implications on the design of coatings and of composite systems using alternative coatings are discussed. Potential topics for further research are identified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00505.x
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  • 2
    Electronic Resource
    Electronic Resource
    Processing, Microstructure, and Strength of Alumina–YAG Eutectic Polycrystals (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dense polycrystalline eutectics of alumina and yttrium aluminum garnet (YAG) were fabricated by hot-pressing powders of pulverized arc-melted buttons at homologous temperatures of 0.9Teu–0.93Teu (where Teu is the eutectic temperature). The eutectic microstructure of the arc-melted buttons was retained after densification, although the grain boundaries were decorated with equiaxed grains of alumina and YAG ∼1–5 μm in size; possible causes for their formation have been discussed. A comparison of the measured strength of the polycrystalline eutectics (274 ± 61 MPa) with grain size and fracture toughness suggests that the strength-limiting flaws are significantly smaller than the mean grain size and larger than the mean eutectic spacing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01518.x
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  • 3
    Electronic Resource
    Electronic Resource
    High-Temperature Environmental Stability of the Compounds in the Al2O3–Y2O3 System (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Heat treatments in several environments were performed on a series of compounds in the Al2O3 and Y2O3 system: Al2O3Y3Al5O12 eutectic, Y3Al5O12, YAlO3, Y4Al2O9, and Y2O3. The yttrium aluminates were found to be stable at high temperatures under vacuum and in air. However, when they were heat-treated under vacuum in proximity to SiC, degradation was observed. This was found to be primarily a result of carbothermal reduction. In a similarly reducing environment without Si, the yttrium aluminates, and Al2O3 and Y2O3, all exhibited degradation by carbothermal reduction. Based upon the experimental results, a degradation mechanism for yttrium aluminates was proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb02916.x
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  • 4
    Electronic Resource
    Electronic Resource
    Interface Properties in High-Strength Nicalon/C/SiC Composites, As Determined by Rough Surface Analysis of Fiber Push-Out Tests (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Fiber push-out curves generated on high-strength, treated-fiber Nicalon/C/SiC composites indicate behavior that is distinctly different from other composites. These composites have been analyzed using a model that explicitly includes two sets of debond-crack-surface topographies that correspond to two stages of crack propagation. The model successfully duplicates the observed unusual push-out load-deflection behavior by adjusting interfacial toughness and topographical parameters to fit the experimental data. Although the topographical parameters of the debonding cracks are largely unconfirmed, the fitted values are consistent with observations and expectations. This analysis has determined interfacial fracture energies that are unusually high for composites with acceptable mechanical behavior but are consistent with measurements on bulk pyrocarbons. The analysis provides a unifying rationalization of the apparent inconsistencies in results reported for such materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02561.x
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  • 5
    Electronic Resource
    Electronic Resource
    Predicted Effects of Interfacial Roughness on the Behavior of Selected Ceramic Composites (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Potential effects of interfacial roughness in ceramic composites were studied using a model that included the progressively increasing contribution of roughness with relative fiber/matrix displacement during debonding of the fiber/matrix interface. A parametric approach was used to study interfacial roughness in conjunction with other parameters such as the strength, radius, and volume fraction of the fiber. The progressive roughness contribution during initial fiber/matrix sliding caused a high effective coefficient of friction, as well as an increased clamping stress, which led to rapidly changing friction with increasing debond length. Calculated effects implied a potentially significant contribution to the behavior of real composite systems and the necessity for explicit consideration in the interpretation of experimental data to understand composite behavior correctly. In a tension test, the Poisson's contraction of the fiber may negate the effects of roughness, allowing an “effective constant shear stress” (tau) approximation. This was evaluated using a piecewise linear approximation to the progressive roughness model in an analysis of composite stress-strain behavior; for the Nicalon/SiC system, the effective tau value was lower than the values that would be obtained from fiber pushout tests and/or matrix crack spacings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03088.x
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  • 6
    Electronic Resource
    Electronic Resource
    Fiber—Matrix Interface Properties of Single-Fiber Microcomposites as Measured by Fiber Pushin Tests (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Fiber pushin tests have been performed on single-fiber microcomposite specimens embedded in glass. The interface properties determined were in agreement with those previously determined by two methods from tensile tests on microcomposites. The uncertainties in the interface properties calculated from the microcomposite pushin tests were not found to benefit from the superior alignment of the microcomposite specimens, as compared to literature results from composite specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb02859.x
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  • 7
    Electronic Resource
    Electronic Resource
    Reduction of Thermal-Gradient-Induced Stresses in Composites Using Mixed Fibers (2004)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 87 (2004), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The possibility of using fibers of varying thermal expansivities to reduce stresses generated from thermal gradients in service was explored. Laminates of aluminosilicate- and alumina-matrix composites were fabricated using a combination of Nextel 610™ and Nextel 720™ fibers. The composites were tested for mechanical behavior and thermomechanical behavior in comparison to control composite specimens which contained a single type of fiber. Mixed-fiber composites show strength and fracture behavior similar to those of single-fiber-type composites. Their thermomechanical behavior is consistent with 2D laminate models, making it possible to design composites using such models. Interlaminar shear stress is a key, but sole limitation and the use of gradation in fiber mixture is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.00617.x
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  • 8
    Electronic Resource
    Electronic Resource
    Effective Fiber Properties to Incorporate Coating Thermoelastic Effects in Fiber/Matrix Composite Models (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A method to incorporate the thermoelastic effects of fiber coatings into models of fiber/matrix composites was deter-mined. The coated fiber was replaced by an “effective” transversely isotropic fiber so that the properties of this effective fiber could be used in composite models. This ap-proach was used to determine the magnitude of errors re-sulting from neglect of the coatings in modeling fiber/matrix debonding and sliding and in reduction of data from real composites. The effects of carbon and BN coatings in the Nicalon/SiC system were found to be significant. It was found that significant errors could be expected from fitting models to experimental data if the compliance and coeffi-cient of thermal expansion of the coatings were ignored, even when the coatings were thin. Wide use of the approach required revision of composite models to allow inclusion of a transversely isotropic fiber. Such a revision was de-rived for a popular model of matrix cracking stress, and significant effects again were found to result from neglect of coatings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01804.x
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  • 9
    Electronic Resource
    Electronic Resource
    Validity of Using Average Diameter for Determination of Tensile Strength and Weibull Modulus of Ceramic Filaments (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Strengths and Weibull moduli for alumina/yttrium aluminum garnet eutectic (AYE) filaments and for Si-C-O (Nicalon TM) filaments were calculated using measured and average filament diameters. The strengths agreed closely. Thus an average filament diameter could be used instead of the measured filament diameter in calculating strengths. The Weibull modulus obtained from an average filament diameter approximates the Weibull modulus obtained using the measured filament diameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03188.x
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  • 10
    Electronic Resource
    Electronic Resource
    A Model for Transitions in Oxidation Regimes of ZrB〈sub〉2〈/sub〉 (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 595-598 (Sept. 2008), p. 823-832 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A mechanistic model that interprets the transition in oxidation behavior of zirconiumdiboride as the temperature is varied from 600°C to 2500°C is presented. Available thermodynamicdata and literature data for vapor pressures, oxygen permeability in boria, and viscosity of boriawere used to evaluate the model. Three regimes and the temperatures of transition between themwere identified. In the intermediate temperature regime, viz., 1000ºC to 1800ºC, goodcorrespondence was obtained between theory and experiments for weight gain, recession, and scalethickness as functions of temperature and oxygen partial pressure. In this regime, the rate-limitingstep is the diffusion of dissolved oxygen through a film of liquid boria in capillaries at the base ofthe oxidation product. At lower temperatures, an external boria scale forms, but it was not found tocontribute significantly to oxidation resistance. Comparison with literature data on recession is verygood, but weight gain is predicted to be higher than experimentally observed unless flow of viscousboria is included. At higher temperatures, the boria is lost by evaporation, and the oxidation rate islimited by diffusion of molecular oxygen through the capillaries between nearly columnar blocks ofthe oxide MO2.; this regime is soon followed by a rapid acceleration of recession due tovaporization of the oxide MO2 itself
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/20/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.595-598.823.pdf
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