Efforts such as the one proposed here contribute to the development of more physically-realistic lifetime models, which are ultimately needed to extend the use CMCs. While these materials are slowly being introduced for use in more mainstream applications such as power generation turbines and commercial jet engines, frequently they are not used to their full temperature or strength capability. However, with more accurate modeling, CMCs could be used more aggressively, for both stationary and rotating turbine components, and in more severe environmental conditions (steam, salt fog, etc.). These materials can allow higher operating temperatures than are possible with superalloys, which can significantly decrease system weight and increase system efficiency. In general, the proposed effort would significantly improve currently-available CMC durability models, which will ultimately be valuable for any company which manufactures CMCs or uses them in their products. The proposed effort would directly support all future durability modeling of CMCs, enhance model accuracy, which ultimately enables wider use of CMCs. This would contribute to NASA's goals in hypersonic vehicles and other advanced aircraft, for both structural and propulsion components. Currently, CMCs are primarily niche materials not only because of cost, but also because their long-term behavior in aggressive environments is not thoroughly understood or characterized. As such, it is quite difficult to make lifetime predictions without use of relatively large safety factors. The proposed program would provide significant enhancement to current modeling capability, which could readily be expanded to model tortuosity (another material property which controls oxidation).