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  • 1
    Publication Date: 2011-08-24
    Description: Nicalon silicon carbide 3D yarn with silicon carbide matrix composites made through a chemical vapor infiltration (CVI) process were investigated under tensile and flexural loading at 23, 1200 and 1550 C in air. The effectiveness of a chemical vapor deposition (CVD) SiC surface coating was also evaluated in severe oxidizing environment. Acoustic emission sensors and in situ optical microscopy were used at room temperature to monitor the failure mechanisms. It is shown that the level of tensile stress at which nonlinear behavior begins is not drastically reduced at 1200 and 1550 C when composites were protected by a SiC surface coating. Extensive fiber pull-out was observed only in the 1550 C specimen. Similar behaviors were also found in flexural specimens.
    Keywords: COMPOSITE MATERIALS
    Type: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 13; 7-8,
    Format: text
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  • 2
    Publication Date: 2019-07-13
    Description: Three-dimensional Nicalon SiC/SiC matrix composites made through a chemical vapor infiltration process were studied under tensile and flexural loading at 23, 1200, and 1550 C in air. In situ damage accumulation monitoring NDE techniques were utilized to identify failure mechanisms in these materials. The effectiveness and durability of a chemical vapor deposition SiC surface coating were also evaluated in severe oxidizing environment. Results show that the failure response was very similar for the 23 and 1200 C specimens, while at 1550 C there were significant changes in both the composite mechanical behavior and the matrix microstructure. Extensive fiber pull-out was observed only in the 1550 C specimen. It is also found that the SiC surface coating can protect the composite up to the critical matrix cracking strength.
    Keywords: COMPOSITE MATERIALS
    Type: AIAA PAPER 92-2492 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 13, 1992 - Apr 15, 1992; Dallas, TX; United States
    Format: text
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  • 3
    Publication Date: 2019-07-13
    Description: High temperature ceramic matrix composites (CMC) are being explored as viable candidate materials for hot section gas turbine components. These advanced composites can potentially lead to reduced weight and enable higher operating temperatures requiring less cooling; thus leading to increased engine efficiencies. There is a need for convenient design tools that can accommodate various loading conditions and material data with their associated uncertainties to estimate the minimum predicted life as well as the failure probabilities of a structural component. This paper presents a review of the life prediction and probabilistic analyses performed for a CMC turbine stator vane. A computer code, NASALife, is used to predict the life of a 2-D woven silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) turbine stator vane due to a mission cycle which induces low cycle fatigue and creep. The output from this program includes damage from creep loading, damage due to cyclic loading and the combined damage due to the given loading cycle. Results indicate that the trends predicted by NASALife are as expected for the loading conditions used for this study. In addition, a combination of woven composite micromechanics, finite element structural analysis and Fast Probability Integration (FPI) techniques has been used to evaluate the maximum stress and its probabilistic distribution in a CMC turbine stator vane. Input variables causing scatter are identified and ranked based upon their sensitivity magnitude. Results indicate that reducing the scatter in proportional limit strength of the vane material has the greatest effect in improving the overall reliability of the CMC vane.
    Keywords: Composite Materials
    Type: NASA/TM-2007-214975 , E-16136 , ASME Turbo Expo 2007, Power for Land, Sea and Air Conference; May 14, 2007 - May 17, 2007; Montreal; Canada
    Format: application/pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 11 (1975), S. 409-429 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé On applique la méthode d'analyse par lignes aux équations d'équilibre élastique de Navier-Cauchy pour calculer la distribution des déplacements dans divers corps comportant des fissures. L'application de la méthode à ces équations conduit à des couples d'équations différentielles ordinaires, dont les solutions sont obtenues pour des séries de lignes disposées dans une région discrète. Lorsqu'il n'est pas possible de découpler les équations et leurs conditions aux limites, le recours à une procédure d'approximation successive permet de trouver une solution analytique aux équations différentielles ordinaires. Les résultats obtenus montrent les possibilités remarquables de l'emploi de la méthode pour l'analyse tridimensionnelle de solides à géométrie finie, et suggèrent des extensions possibles à l'étude du comportement des matériaux non linéaires.
    Notes: Abstract The line method of analysis is applied to the Navier-Cauchy equations of elastic equilibrium to calculate the displacement distributions in various bodies containing cracks. The application of this method to these equations leads to coupled sets of simultaneous ordinary differential equations whose solutions are obtained along sets of lines in a discretized region. When decoupling the equations and their boundary conditions is not possible, the use of a successive approximation procedure permits the analytical solution of the resulting ordinary differential equations. The results obtained show a considerable potential for using this method in the three-dimensional analysis of finite geometry solids and suggest a possible extension of this technique to nonlinear material behavior.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 1989-03-01
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Wiley on behalf of American Ceramic Society.
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  • 6
    Publication Date: 2018-08-01
    Print ISSN: 0273-1177
    Electronic ISSN: 1879-1948
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Elsevier
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  • 7
    Publication Date: 2011-12-09
    Description: The mechanical behavior of continuous fiber reinforced SiC/RBSN composites with strong and weak interface characteristics is evaluated. Both catastrophic and noncatastrophic failures are observed in tensile specimens. Effects of fiber/matrix interface debonding (splitting) parallel to the fibers are discussed. Micromechanical models incorporating residual stresses to calculate the critical matrix cracking strength, ultimate strength and work of pull-out are reviewed and used to predict composite response. Experimental results are compared to analytical predictions.
    Keywords: COMPOSITE MATERIALS
    Type: In: Mechanics of composites at elevated and cryogenic temperatures; Proceedings of the Symposium, ASME Applied Mechanics Conference, Columbus, OH, June 16-19, 1991 (A93-32451 12-39); p. 217-229.
    Format: text
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  • 8
    Publication Date: 2011-08-24
    Description: A series of tensile tests were conducted on SiC/RBSN composites using different methods of strain measurement. The tests were used to find the optimum strain sensing device for use with continuous fiber reinforced ceramic matrix composites in ambient and high temperature environments. Bonded resistance strain gages were found to offer excellent performance for room temperature tests. The clip-on gage offers the same performance but significantly less time is required for mounting it to the specimen. Low contact force extensometers track the strain with acceptable results at high specimen temperatures. Silicon carbide rods with knife edges are preferred. The edges must be kept sharp. The strain measuring devices should be mounted on the flat side of the specimen. This is in contrast to mounting on the rough thickness side.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Testing and Evaluation (ISSN 0090-3973); 20; 4, Ju
    Format: text
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  • 9
    Publication Date: 2011-08-23
    Description: Strength of three continuous fiber-reinforced ceramic composites, including SiC/CAS-11, SiC/MAS-5 and SiC/SiC, was determined as a function of test rate in air at 1100 - 1200 C. All three composite materials exhibited a strong dependency of strength on test rate, similar to the behavior observed in many advanced monolithic ceramics at elevated temperatures. The application of the preloading technique as well as the prediction of life from one loading configuration (constant stress-rate) to another (constant stress loading) suggested that the overall macroscopic failure mechanism of the composites would be the one governed by a power-law tyw of damage evolution/accumulation, analogous to slow crack growth commonly observed in advanced monolithic ceramics. It was further found that constant stress-rate testing could be used as an alternative to life prediction test methodology even for the composite materials at least for the short range of lifetime.
    Keywords: Nonmetallic Materials
    Type: Ceramic Engineering and Science Proceedings; Volume 22; 597-606
    Format: text
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  • 10
    Publication Date: 2011-08-24
    Description: One of the primary pacing items for realizing the full potential of ceramic-based structural components is the development of new design methods and protocols. The focus here is on low temperature, fast-fracture analysis of monolithic, whisker-toughened, laminated, and woven ceramic composites. A number of design models and criteria are highlighted. Public domain computer algorithms, which aid engineers in predicting the fast-fracture reliability of structural components, are mentioned. Emphasis is not placed on evaluating the models, but instead is focused on the issues relevant to the current state of the art.
    Keywords: COMPOSITE MATERIALS
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