High Temp Standoff Dielectric Antenna Windows Based on 3-D Woven Preforms

Supersonic cruise missiles offer the ability to hit a time critical target with precision and lethality from long distances, yet the high speed generates temperatures on the exterior surfaces of the missile that can exceed the limitations of high temperature structural metals like titanium. Also, insulation to protect electronics equipment in the missile is required. One solution that demonstrates promise for high-temperature, structural antenna windows is structural ,low dielectric constant, oxide-oxide ceramic matrix composite (CMC) based on a 3-D woven preform that integrates the thermal protection system. The 3-D preform consists of ceramic fabric skins separated by through-thickness reinforcements, or Z-yarns, woven into each skin. Structures based on oxide-oxide systems have suitable dielectric properties and can withstand the anticipated high temperatures. The 3-D oxide fiber architecture also provides a means for optimizing the overall system performance since many key properties depend primarily on the details of the Z-yarn placement and volume fraction. The Phase I effort successfully demonstrated fabrication of two Nextel 720 preforms infused with alumina matrices. The proposed Phase II program will further develop the design space associated with the integral standoff CMC materials, characterize a matrix of the standoff materials, and resolve remaining manufacturing challenges.