NASA LogoNTRSNTRS - NASA Technical Reports ServerSearchmore_vertCollectionsAboutNewsHelpLogin Back to ResultsModeling of Time-Dependent Strength Degradation of SiC/SiC Ceramic Matrix Composites via MAC/GMC Computer CodeSilicon carbide fiber reinforced silicon carbide (SiC/SiC) ceramic matrix composites (CMCs) display time-dependent strength degradation at intermediate temperatures (600 to 900 degrees Centigrade). This is generally believed to be an oxidation induced phenomenon. The understanding of the effect of temperature with environment (oxidation) is key towards development of SiC/SiC CMCs with a reliable load carrying capacity. Various theories have been proposed to explain the strength degradation. One suggests that the boron nitride (BN) coating deposited on the fibers oxidizes causing fusion of fibers. Another theory proposes that the SiC fibers are oxidized forming a silica scale leading to premature fiber failure. A more recent theory suggests that SiC fiber strength is intrinsically time-dependent due to slow crack growth of flaws in the fibers. An empirical model, termed as a "fiber classic model," which is based on a standard slow crack growth type power-law, has been implemented within NASA's micromechanics-based MAC/GMC computer code as a user routine. Model parameters for this "classic model" were calibrated from stress-rupture data of Hi-Nicalon (TM) monofilaments using the maximum likelihood estimation (MLE) technique. This new capability in the MAC/GMC computer code was then used to predict the stress-rupture behavior of Hi-Nicalon (TM) tows as well as 2-D SiC/SiC composites reinforced with Hi-Nicalon (TM) fibers. Results demonstrate that the MAC/GMC with this new capability successfully predicts the time-to-failure vs. applied stress within the intermediate temperature range at various scales as well as laminated composites in an oxidizing environment.Document ID20180006436Acquisition SourceGlenn Research CenterDocument TypeTechnical Memorandum (TM)AuthorsMital, Subodh K.*(Toledo Univ. Toledo, OH, United States)*Arnold, Steven M.*(NASA Glenn Research Center Cleveland, OH, United States)*Murthy, Pappu L. N.*(NASA Glenn Research Center Cleveland, OH, United States)*Bednarcyk, Brett A.*(NASA Glenn Research Center Cleveland, OH, United States)*Pineda, Evan J.*(NASA Glenn Research Center Cleveland, OH, United States)*Date AcquiredOctober 18, 2018Publication DateAugust 1, 2018Subject CategoryComposite MaterialsReport/Patent NumberE-19553NASA/TM-2018-219939GRC-E-DAA-TN56873Funding Number(s)CONTRACT_GRANT: NNC13BA10BWBS: WBS 109492.02.03.01.30Distribution LimitsPublicCopyrightPublic Use Permitted.KeywordsEnvironmental degradationstatic fatigueOxidationAvailable DownloadsNameType20180006436.pdfSTIcloud_downloadcontent_copyvisibilityRelated RecordsThere are no records associated with this record.visibility_offNo Preview Available
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