High temperature composites utilizing ceramic fibers (e.g. SiC or AI2O3) and high melting point metals, intermetallics, and ceramics are being developed for applications in aircraft turbine engines, air frames, and the skins of hypersonic vehicles [1]. In order to achieve the strength necessary for these applications, single crystal AI2O3 (sapphire) reinforcing fibers are used because of their combination of very high modulus (∼450 GPa), low density (∼3.7 g cm-1), excellent low temperature strength (3–4 GPa), exceptionally good creep strength, and chemical stability in oxidizing environments.