ORAL: xxxxx EFFECT OF MICROSTRUCTURAL CHANGE ON THE R-CURVE BEHAVIOR OF AN ALUMINA MATRIX COMPOSITE REINFORCED WITH SILICON CARBIDE WHISKERS Takashi AKATSU, Yasuhiro TANABE and Eiichi YASUDA Materials and Structures Laboratory, Tokyo Institute of Technology 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan ABSTRACT The R-curve of an Al2O3 matrix composite reinforced with SiC-whiskers typically comprises two stages in response to crack face bridging processes. The microstructural change in the composite strongly affected the bridging processes, and resulted in a significant change in the R-curve. KEYWORDS R-curve, ceramic matrix composite, whisker, crack face bridging INTRODUCTION Tailoring the microstructure of ceramic matrix composites reinforced with ceramic whiskers to govern the rising R-curve behavior is important, because the initial rising gradient of the curve strongly affects their mechanical properties. A numerical simulation based on a series of probable crack face whisker bridging processes with a sound physical basis may be quite efficient to elucidate the dependence of microstructural change in the composite on the R-curve behavior. In this paper, the rising R-curve behavior of an alumina matrix composite reinforced with silicon carbide whiskers has been experimentally examined. On the other hand, an analytical simulation for a crack face whisker bridging model has been carried out. Comparison between the experimental and the simulated R-curves has been made to confirm the validity of the model. Analysis to derive crack closure stress σb from the observed R-curve has been accomplished to examine the effect of microstructural change on the R-curve. EXPERIMENTAL Two kinds of SiC whiskers named as TWS-400 of rather large size and as TWS-100 of relatively small size, respectively, were used as the reinforcement of alumina matrix composites. The
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