Rate Dependence of Tensile Properties and Stress-Strain Behavior of an Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature and the Effects of Low-Magnitude Sustained Loading on Composite Microstructure
Advanced aerospace structures and components require materials that exhibit high strength at high operating temperatures. Nextel ™ 720/Alumina (N720/A) is an oxide/oxide, porous-matrix ceramic-matrix composite developed for load bearing applications at elevated temperatures. The current research inv...
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AFIT Scholar
2006
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| Online adgang: | https://scholar.afit.edu/etd/3584 https://scholar.afit.edu/context/etd/article/4585/viewcontent/AFIT_GAE_ENY_06_S09_Radzicki_A.pdf |
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| _version_ | 1870451969636696064 |
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| author | Radzicki, Andrew T. |
| author_facet | Radzicki, Andrew T. |
| author_sort | Radzicki, Andrew T. |
| building | US Air Force Institute of Technology (AFIT) |
| collection | AFIT Scholar |
| description | Advanced aerospace structures and components require materials that exhibit high strength at high operating temperatures. Nextel ™ 720/Alumina (N720/A) is an oxide/oxide, porous-matrix ceramic-matrix composite developed for load bearing applications at elevated temperatures. The current research investigates the rate dependence of tensile properties of the N720/A CMC at 1200°C as well as the creep behavior of this composite under applied stresses in the 1-25 MPa range. In addition, influence of prior loading rate on the creep response of N720/A under applied stresses above 50 MPa was evaluated at 1200°C. Tensile tests conducted at loading rate of 0.0025 and 25 MPa/s revealed a strong influence of rate on the ultimate tensile strength, elastic modulus and failure strain. Several samples subjected to additional heat-treatments were tested to ascertain whether the stress-strain behavior observed in the 0-30 MPa stress range in tests conducted at 0.0025 MPa/s was an artifact of incomplete processing of fibers in the as-received material. Additional heat treatment had no effect on stress-strain behavior at 0.0025 MPa/s. Negative creep (i. e. decrease in strain under constant stress) was observed in creep tests conducted with the applied stresses < 30 MPa. Microstructural investigation using scanning electron microscope together with the results of mercury porosimetry suggest that a decrease in matrix porosity and matrix densification may be taking place in the N720/A CMC exposed to loads <30 MPa for prolonged periods of time. Prior loading rate was found to have no appreciable effect on creep behavior at stresses >50 MPa. |
| format | text |
| id | afit-etd-4585 |
| institution | US Air Force Institute of Technology |
| publishDate | 2006 |
| publisher | AFIT Scholar |
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| spelling | afit-etd-4585 Rate Dependence of Tensile Properties and Stress-Strain Behavior of an Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature and the Effects of Low-Magnitude Sustained Loading on Composite Microstructure Radzicki, Andrew T. Advanced aerospace structures and components require materials that exhibit high strength at high operating temperatures. Nextel ™ 720/Alumina (N720/A) is an oxide/oxide, porous-matrix ceramic-matrix composite developed for load bearing applications at elevated temperatures. The current research investigates the rate dependence of tensile properties of the N720/A CMC at 1200°C as well as the creep behavior of this composite under applied stresses in the 1-25 MPa range. In addition, influence of prior loading rate on the creep response of N720/A under applied stresses above 50 MPa was evaluated at 1200°C. Tensile tests conducted at loading rate of 0.0025 and 25 MPa/s revealed a strong influence of rate on the ultimate tensile strength, elastic modulus and failure strain. Several samples subjected to additional heat-treatments were tested to ascertain whether the stress-strain behavior observed in the 0-30 MPa stress range in tests conducted at 0.0025 MPa/s was an artifact of incomplete processing of fibers in the as-received material. Additional heat treatment had no effect on stress-strain behavior at 0.0025 MPa/s. Negative creep (i. e. decrease in strain under constant stress) was observed in creep tests conducted with the applied stresses < 30 MPa. Microstructural investigation using scanning electron microscope together with the results of mercury porosimetry suggest that a decrease in matrix porosity and matrix densification may be taking place in the N720/A CMC exposed to loads <30 MPa for prolonged periods of time. Prior loading rate was found to have no appreciable effect on creep behavior at stresses >50 MPa. 2006-09-01T07:00:00Z text application/pdf https://scholar.afit.edu/etd/3584 https://scholar.afit.edu/context/etd/article/4585/viewcontent/AFIT_GAE_ENY_06_S09_Radzicki_A.pdf Theses and Dissertations AFIT Scholar Ceramic-matrix composites--Creep Oxide ceramics Strains and stresses Composite materials--Creep Engineering Science and Materials |
| spellingShingle | Ceramic-matrix composites--Creep Oxide ceramics Strains and stresses Composite materials--Creep Engineering Science and Materials Radzicki, Andrew T. Rate Dependence of Tensile Properties and Stress-Strain Behavior of an Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature and the Effects of Low-Magnitude Sustained Loading on Composite Microstructure |
| title | Rate Dependence of Tensile Properties and Stress-Strain Behavior of an Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature and the Effects of Low-Magnitude Sustained Loading on Composite Microstructure |
| title_full | Rate Dependence of Tensile Properties and Stress-Strain Behavior of an Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature and the Effects of Low-Magnitude Sustained Loading on Composite Microstructure |
| title_fullStr | Rate Dependence of Tensile Properties and Stress-Strain Behavior of an Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature and the Effects of Low-Magnitude Sustained Loading on Composite Microstructure |
| title_full_unstemmed | Rate Dependence of Tensile Properties and Stress-Strain Behavior of an Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature and the Effects of Low-Magnitude Sustained Loading on Composite Microstructure |
| title_short | Rate Dependence of Tensile Properties and Stress-Strain Behavior of an Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature and the Effects of Low-Magnitude Sustained Loading on Composite Microstructure |
| title_sort | rate dependence of tensile properties and stress strain behavior of an oxide oxide ceramic matrix composite at elevated temperature and the effects of low magnitude sustained loading on composite microstructure |
| topic | Ceramic-matrix composites--Creep Oxide ceramics Strains and stresses Composite materials--Creep Engineering Science and Materials |
| url | https://scholar.afit.edu/etd/3584 https://scholar.afit.edu/context/etd/article/4585/viewcontent/AFIT_GAE_ENY_06_S09_Radzicki_A.pdf |
| work_keys_str_mv | AT radzickiandrewt ratedependenceoftensilepropertiesandstressstrainbehaviorofanoxideoxideceramicmatrixcompositeatelevatedtemperatureandtheeffectsoflowmagnitudesustainedloadingoncompositemicrostructure |