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Sapphire Statistical Strength Characterization



D R. McClure, R W. Cayse, S Goodrich, D McCullum, D C. Harris, K Lagerlof, C E. Patty, D H. Platus, Robert S. Polvani, David R. Black


Approximately 1400 4-point flexure specimens were tested at 300 K to 873 K to establish an engineering database for the strength of sapphire. Coupons represented material used for two missile windows and one missile dome. For one window, coupons were fabricated by two different polishing shops using identical blanks from one material supplier. Flexure specimens from one shop were 50 % stronger than specimens from the other shop, even though materials were finished to the same specifications. Thirty window coupons were taken to failure by rapid heating with a laser to compare their performance with predictions from 4-point flexure tests. The predicted median time to failure was 2.85 s, but the observed median time was 4.05 s, indicating that the 4-point flexure strength provides a conservative estimate of performance in the thermal shock test. A set of 39 4-point flexure specimens could be divided into 2 groups based on the appearance or lack of appearance of grinding damage seen in x-ray topography. The group that did not exhibit grinding damage was 50 % stronger than the group that was damaged. The damage in question was not observed by other nondestructive techniques.
Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing


characterization, fracture, sapphire, strength


McClure, D. , Cayse, R. , Goodrich, S. , McCullum, D. , Harris, D. , Lagerlof, K. , Patty, C. , Platus, D. , Polvani, R. and Black, D. (2001), Sapphire Statistical Strength Characterization, Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing (Accessed June 20, 2024)


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Created September 6, 2001, Updated October 12, 2021