The R-curve response of ceramics with microscopic reinforcements: Reinforcement and additive effects
Description: Using direct observations with the scanning electron and optical microscopes, simultaneous measurements of fracture resistance versus crack length (R-curve behavior) and crack interactions with microstructural features at the crack tip and in its wake were made. Selecting whisker-reinforced aluminas and self-reinforced silicon nitrides, one can examine the effects of systematic modifications of microstructure and composition on the R-curve response and the mechanisms giving rise to it. Specifically, increases in whisker content and size can increase the R-Curve response, even for short crack lengths. In the self-reinforced silicon nitrides, changes in alumina: yttria additive ratios also modify the R-curve. Modeling of the R-curve response allows one to verify toughening mechanisms and, with experimental studies, to optimize the R-curve behavior in ceramics containing microscopic reinforcements, e.g., whiskers and elongated grain structures.
Date: May 1, 1996
Creator: Becher, P.F.; Sun, E.Y.; Plucknett, K,P. & Hsueh, C.H.
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