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Characterization of Damage Progression in SCS-6/timetal 21S (0)4 Under Thermomechanical Fatigue LoadingsA detailed experimental investigation was performed at a single maximum cyclic stress (sigma max) level to physically characterize the progression of thermomechanical fatigue (lW) damage in continuously reinforced (0 deg) SCS-6/Timetal 21S, a titanium matrix composite. In-phase (IP) and out of-phase (OP) loadings were investigated at sigma max = 1000 MPa with a temperature cycle from 150 to 6500 C. Damage progression, in terms of macroscopic property degradation, was experimentally quantified through an advanced TMF test methodology which incorporates explicit measurements of the isothermal static moduli at the TMF temperature extremes and the coefficient of thermal expansion (CTE) as functions of the TMF cycles. Detailed characterization of the physical damage progression at the microstructural level was performed by interrupting multiple TMF tests at various stages of mechanical property degradation and analyzing the microstructure through extensive destructive metallography. Further, the extent of damage was also quantified through residual static strength measurements. Results indicated that damage initiation occurred very early in cyclic life (N less than 0.1Nf) for both the IP and OP TMF loadings. IP TMF damage was found to be dominated by fiber breakage with a physical damage progression in the microstructure which was difficult to quantify. OP TMF loadings produced matrix cracking exclusively associated with surface initiations. Here, damage progression was easily distinguished in terms of both the number of cracks and their relative inward progressions toward the outer fiber rows with increased cycling. The point at which the leading cracks reached the outer fiber rows (when localized fiber/matrix de-bonding and matrix crack bridging occurred) appeared to be reflected in the macroscopic property degradation curves.
Document ID
19950009496
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Castelli, Michael G.
(NYMA, Inc. Brook Park, OH, United States)
Date Acquired
September 6, 2013
Publication Date
November 1, 1994
Publication Information
Publisher: NASA
Subject Category
Composite Materials
Report/Patent Number
NASA-CR-195399
NAS 1.26:195399
E-9221
Meeting Information
Meeting: Symposium on Life Prediction Methodology for Titanium Matrix Composites
Location: Hilton Head, SC
Country: United States
Start Date: March 22, 1994
End Date: March 24, 1994
Accession Number
95N15911
Funding Number(s)
PROJECT: RTOP 763-22-41
CONTRACT_GRANT: NAS3-27186
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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