Ceramic Composite Windows and Radomes for Hypersonic Vehicles

Conventional dielectric materials for hypersonic radome and window applications exhibit a number of performance limitations including inadequate thermal shock resistance, variations in electrical (dielectric constant and loss) and structural performance (mechanical strength) with temperature, and difficulty in fabrication to the desired shape. We propose to develop high strength, high toughness, high temperature stable, low dielectric constant continuous fiber-reinforced ceramic composites with wide band-pass in the L band (1-2 GHz) for GPS navigation and guidance, S-Ku (2-18 GHz) band for wrap-around antenna, and W band (94 GHz) for terminal homing for hypersonic window and radome applications. The Phase I program will fabricate a fiber-reinforced ceramic composite with the required electrical and mechanical properties for hypersonic windows and radomes. Equibiaxial flexural strength and thermal shock resistance of the composite disks will be measured up to 1500ºC, and Weibull parameters will be calculated to determine their reliability. Free-space microwave dielectric properties, dielectric constant and loss tangent, between 75 GHz and 100 GHz will be measured up to 1500ºC.