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Proceedings Paper

High-temperature strength of sapphire
Author(s): Daniel C. Harris
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Paper Abstract

The Sapphire Statistical Characterization and Risk Reduction Program tested approximately 1500 4-point flexure bars with different crystal orientations at different temperatures to establish a mechanical strength database for engineering design. Sapphire coupons were selected to represent surfaces on two different missile windows and a missile dome. Sapphire was obtained from the same suppliers used for the windows or dome and, as much as possible, coupons were fabricated in the same manner as the corresponding part of the window or dome. Perhaps the most interesting result was that sapphire from one fabricator was 50% stronger than sapphire made to the same specifications from the same blanks by another fabricator. In laser heating tests, sapphire performed better than predicted from flexure tests. When a compliant layer of graphite was used as a pad between the test specimens and the load fixture, sapphire in which the principal axis of tension and compression was parallel to the c-axis increased in apparent strength by a factor of 2 - 3. Strengths of other crystal orientations were not significantly affected by the graphite pads, but the incidence of twinning at 883 K was reduced by graphite.

Paper Details

Date Published: 25 October 2000
PDF: 12 pages
Proc. SPIE 4102, Inorganic Optical Materials II, (25 October 2000); doi: 10.1117/12.405288
Show Author Affiliations
Daniel C. Harris, Naval Air Warfare Ctr. (United States)

Published in SPIE Proceedings Vol. 4102:
Inorganic Optical Materials II
Alexander J. Marker III; Eugene G. Arthurs, Editor(s)

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