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Mechanisms of boron fiber strengthening by thermal treatmentThe fracture strain for boron on tungsten fibers can be improved by heat treatment under vacuum or argon environments. The mechanical basis for this improvement is thermally-induced axial contraction of the entire fiber, whereby strength-controlling core flaws are compressed and fiber fracture strain increased by the value of the contraction strain. By highly sensitive measurements of fiber density and volume, the physical mechanisms responsible for contraction under both environments was identified as boron atom diffusion out of the fiber sheath. The fiber contracts because the average volume of the resulting microvoid was determined to be only 0.26 + or - 0.09 the average atomic volume of the removed atom. The basic and practical implications of these results are discussed with particular emphasis on the theory, use, and limitations of heat-induced contraction as a simple cost-effective secondary processing method.
Document ID
19790046383
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Dicarlo, J. A.
(NASA Lewis Research Center Cleveland, Ohio, United States)
Date Acquired
August 9, 2013
Publication Date
January 1, 1979
Subject Category
Composite Materials
Meeting Information
Meeting: American Ceramic Society, Annual Conference in Composites and Advanced Materials
Location: Merritt Island, FL
Start Date: January 21, 1979
End Date: January 24, 1979
Sponsors: American Ceramic Society
Accession Number
79A30396
Distribution Limits
Public
Copyright
Other

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