Determination of Subcritical Crack Growth Parameters in Polymer-Derived SiOC Ceramics by Biaxial Bending Tests in Water Environment
- Author: K.G. Schell, E.C. Bucharsky, R. Oberacker, M.J. Hoffmann
- Source: JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 2010, Band 93, Heft 6, S. 1540-1543
Polymer-derived SiOC ceramics were prepared by field-assisted sintering at 1600 degrees C. In order to characterize this material, X-ray diffractometry, density measurements, and mechanical tests were performed. It was determined that the material is dense and predominantly amorphous with fine crystalline regions of beta-SiC. A fracture toughness of 0.84 MPa center dot m1/2 was determined from single edge, v-notched bending tests. Inert strength and subcritical crack growth parameters were derived from the ball-on-three-balls tests carried out at different loading rates. The inert strength of 212 MPa and the crack growth exponent n of 15 are on a similar level as commonly expected for silica-based glasses. Because of an enhanced crack growth parameter A(0), the crack velocity of the SiOC material at a given stress intensity level is significantly reduced compared with silica glasses.