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Electrical Resistance Changes of Melt Infiltrated SiC/SiC Subject to Long-Term Tensile Loading at Elevated Temperatures

Smith, Craig E
http://rave.ohiolink.edu/etdc/view?acc_num=akron1461690076

Abstract Details

2016, Doctor of Philosophy, University of Akron, Mechanical Engineering.
Melt infiltrated (MI) SiC fiber-reinforced SiC ceramic matrix composites (CMCs) are slowly replacing metals in the hot section components of turbine engines. The increasing application of these composites requires structural health monitoring techniques that are sensitive to transverse matrix cracks which form at elevated temperatures and limit the long-term durability of the material. Previous research has demonstrated a large increase in electrical resistance (ER) in response to transverse matrix cracks that formed in MI SiC/SiC during room temperature tensile loading. In this study, the ER response of slurry cast MI SiC/SiC CMCs at elevated temperatures (815°C and 1315°C), was explored under a wide range of applied tensile stresses. The results showed that the ER increased by up to 300% in response to tensile loading at the intermediate temperature of 815°C. Long-term stressed-oxidation tests at 815°C led to in-situ ER increases of more than 90% prior to sample break. The in-situ ER changes also directly correlated with measured crack density. Similarly, post-test inspection of the samples at room temperature showed ER increases greater than 100% for cracked samples after 100 hours. The room temperature inspection ER also correlated directly with the observed crack density. Thus, for all tests at 815°C, the ER was highly sensitive to the formation of matrix cracks. However, for the test temperature of 1315°C, the ER was less sensitive to damage. Resistance changes of the samples were an order of magnitude lower than they were at 815°C and there was no clear correlation between ER and crack density. The difference in results for the two test temperatures was explained by the decreasing sample resistivity at higher temperatures. Since the resistance was measured from the cold grips, the cooler (higher resistivity) regions had more effect on the sample resistance than the hotter (lower resistivity) regions.
Gregory Morscher, Dr. (Advisor)
Kwek-Tze Tan, Dr. (Committee Member)
Wieslaw Binienda, Dr. (Committee Member)
Erol Sancaktar, Dr. (Committee Member)
Manigandan Kannan, Dr. (Committee Member)
Tirumalai Srivatsan, Dr. (Other)
218 p.
Mechanical Engineering
ceramic matrix composites; damage detection; health monitoring; electrical resistance

Recommended Citations

Citations

  • Smith, C. E. (2016). Electrical Resistance Changes of Melt Infiltrated SiC/SiC Subject to Long-Term Tensile Loading at Elevated Temperatures [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1461690076

    APA Style (7th edition)

  • Smith, Craig. Electrical Resistance Changes of Melt Infiltrated SiC/SiC Subject to Long-Term Tensile Loading at Elevated Temperatures. 2016. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1461690076.

    MLA Style (8th edition)

  • Smith, Craig. "Electrical Resistance Changes of Melt Infiltrated SiC/SiC Subject to Long-Term Tensile Loading at Elevated Temperatures." Doctoral dissertation, University of Akron, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1461690076

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.