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The Evolution of Interfacial Sliding Stresses During Cyclic Push-in Testing of C- and BN-Coated Hi-Nicalon Fiber-Reinforced CMCsInterfacial debond cracks and fiber/matrix sliding stresses in ceramic matrix composites (CMCs) can evolve under cyclic fatigue conditions as well as with changes in the environment, strongly affecting the crack growth behavior, and therefore, the useful service lifetime of the composite. In this study, room temperature cyclic fiber push-in testing was applied to monitor the evolution of frictional sliding stresses and fiber sliding distances with continued cycling in both C- and BN-coated Hi-Nicalon SiC fiber-reinforced CMCs. A SiC matrix composite reinforced with C-coated Hi-Nical on fibers as well as barium strontium aluminosilicate (BSAS) matrix composites reinforced with BN-coated (four different deposition processes compared) Hi-Nicalon fibers were examined. For failure at a C interface, test results indicated progressive increases in fiber sliding distances during cycling in room air but not in nitrogen. These results suggest the presence of moisture will promote crack growth when interfacial failure occurs at a C interface. While short-term testing environmental effects were not apparent for failure at the BN interfaces, long-term exposure of partially debonded BN-coated fibers to humid air resulted in large increases in fiber sliding distances and decreases in interfacial sliding stresses for all the BN coatings, presumably due to moisture attack. A wide variation was observed in debond and frictional sliding stresses among the different BN coatings.
Document ID
Document Type
Eldridge, J. I.
(NASA Lewis Research Center Cleveland, OH United States)
Bansal, N. P.
(NASA Lewis Research Center Cleveland, OH United States)
Bhatt, R. T.
(NASA Lewis Research Center Cleveland, OH United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1998
Subject Category
Composite Materials
Meeting Information
Ceramic Engineering and Science Proceedings Conference(Cocoa Beach, FL)
Funding Number(s)
PROJECT: RTOP 523-21-13
Distribution Limits
Work of the US Gov. Public Use Permitted.
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