Modeling of surface oxidation and oxidation induced damage in metal matrix composites
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abstract
Surface oxidation in metal matrix composites (MMC's) is modeled by Fickian diffusion of oxygen in both the oxide layer and metal matrix. The oxidation process and the resulting immobilized oxygen at the interface is accounted for by the introduction of a jump discontinuity in the oxygen concentration across the interface. The problem of a uniformly growing oxide layer from the surface of a semi-infinite solid is considered a benchmark problem and its closed form solution is used for the comparison with a finite element formulation of the moving interface problem. In addition to the surface oxidation formulation, a one-way coupled thermomechanical analysis of a unidirectional SiC/Ti-15-3 composite undergoing transverse tension is performed and the critical applied load for surface crack formation in the oxide layer is evaluated. Both analytical and finite element techniques are currently being developed for modeling oxidation in MMC's. These techniques take into account complex geometries and model typical thermomechanical loading conditions. In addition, thermomechanical testing and SEM analysis are being carried out for unidirectional laminates with Ti based matrix material and SiC fibers such as Sigma/Ti-15-3 and SCS-6/21s.
