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Techniques for increasing boron fiber fracture strainImprovement in the strain-to-failure of chemical-vapor-deposition boron fibers is shown possible by contracting the tungsten boride core region and its inherent flaws. Results of three methods are presented in which etching and thermal-processing techniques were employed to achieve core flaw contraction by internal stresses available in the boron sheath. After commercially and treatment-induced surface flaws were removed from 203-micron (8-mil) fibers, the core flaw was observed to be essentially the only source of fiber fracture. Thus, fiber strain-to-failure was found to improve by an amount equal to the treatment-induced contraction on the core flaw. To date, average fracture strains and stresses greater than 1.4% and 5.5 GN/sq m (800 ksi), respectively, have been achieved. Commercial feasibility considerations suggest as the most cost-effective technique that method in which as-produced fibers are given a rapid heat treatment above 700 C. Preliminary results concerning the contraction kinetics and fracture behavior observed with this technique are presented and discussed for both high-vacuum and argon-gas heat-treatment environments.
Document ID
19770065112
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
March 1, 1977
Subject Category
Nonmetallic Materials
Meeting Information
Meeting: Annual Meeting
Location: Atlanta, GA
Start Date: March 6, 1977
End Date: March 10, 1977
Sponsors: American Institute of Mining, Metallurgical and Petroleum Engineers
Accession Number
77A47964
Distribution Limits
Public
Copyright
Other

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