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An investigation of theories of failure for ceramic matrix compositesThis final report is comprised of the abstract of a masters thesis research grant. The abstract of the thesis, 'An Investigation of Acoustic Emission Techniques for the Discrimination of Damage Mechanisms in Ceramic Matrix Composites', is as follows: In order to further advance the understanding of the mechanical behavior of ceramic matrix composites (CMS's), acoustic emission (AE) techniques were implemented to monitor and identify damage mechanisms in CMC's under tensile loading. In addition to real-time AE monitoring techniques, a data acquisition system was developed and implemented in order to capture AE waveforms resulting from stress-induced damage. Waveforms were inspected for multiple events, separated in distinct events, and then analyzed to determine waveform characteristics in the time and frequency domains. Waveform characteristics included peak amplitude, event duration, MARSE, energy, and dominant and centroidal frequency. In addition to conventional methods for determining a damage discrimination criteria, a study of the distribution and correlation of the waveform characteristics criteria and a study of the distribution and correlation of the waveform characteristics were performed to aid in the determination of a damage discrimination criteria. The damage discrimination criteria was tested for 'uniqueness', i.e., the effectiveness of the criteria to identify and monitor damage independent of the stress-strain relationship. Insitu radiography was used to substantiate the damage accumulation. A simulation test was also performed over the loading history to study the changes in the waveform characteristics of the system response from a constant excitation. This thesis demonstrates the use of waveform analysis to study the AE activity resulting from stress-induced damage in CMC's in conjunction with other nondestructive evaluation techniques to investigate the mechanical behavior of CMC's.
Document ID
19960011869
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Hemann, John H.
(Cleveland State Univ. OH, United States)
Date Acquired
August 17, 2013
Publication Date
July 21, 1995
Subject Category
Nonmetallic Materials
Report/Patent Number
NAS 1.26:200135
NIPS-96-07896
NASA-CR-200135
Accession Number
96N70754
Funding Number(s)
CONTRACT_GRANT: NCC3-306
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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