Performance Characterization of Polyimide-Carbon Fiber Composites for Future Hypersonic Vehicles.

摘要

The US military has initiated research and development progress to develop hypersonic vehicles in the Mach 5-15 range. Two broad categories are being considered, namely: (i) vehicles that fly at low altitudes for short times (minutes) over distances of hundreds of miles and (ii) flights that are global and cover lower space orbits over periods of hours. Specifically, Air Force future vehicles need to be able to reach anywhere in the world in one hour (Vista 25 program). Aerodynamic heating of the vehicle exterior depends on the altitude, but generally exterior vehicle temperatures are proportional to the square of the Mach number. The primary structures of hypersonic vehicles need to be lightweight, strong and thermally durable. Transition-metal carbides, referred to as ultra-high temperature (UHT) materials, are interesting because they are refractory materials with the highest known melting points (that in many cases exceed 2600 deg. C). Applications for UHT materials challenge the survivability of many known materials currently in use. Unfortunately, the synthesis of the refractory transition-metal carbides requires high temperatures that can exceed 1700 C. The in-situ synthesis of transition-metal carbides, in an argon atmosphere using transition-metal halide salts solution- processed with polymer matrices, is described here as a low temperature method for making UHT carbides. The AFR-PEPA-N polyimide-carbon fiber system is the leading candidate as the starting material. This polymer system is already being processed for leading edge primary structures and engine components for present and future stealth aircraft.