NASA's Langley Research Center has developed a system that provides both structural support and protection attributes in a failsafe manner. This innovation incorporates the use of a pre-ceramic polymer (PCP) composite structure that when overheated or exposed to fire or plasma will convert to a ceramic matrix composite (CMC), retaining structural integrity and still functioning effectively. When damage causes the thermal protection system (TPS) to fail, the underlying PCP structure converts to a CMC material that has high-temperature structural properties, will not catch fire or melt, and continues to perform its structural function.
State-of-the-art TPSs typically include a support or carrier structure with thermal protection material/elements coupled to the carrier structure and exposed to an ambient, high-temperature environment. The carrier structure is generally made from a low-temperature material such as aluminum, titanium, or one of many polymer matrix composites that functions well as long as the structural integrity of the thermal protection material is maintained. If they fail or are damaged (due to impact, chemical breakdown, etc.), the carrier structure can overheat and fail as the temperature increases in the region of the failure.
The technology developed here incorporates a polymer matrix composite TPS carrier structure fabricated with a carbon-fiber-reinforced PCP matrix containing ceramic particulates. During fabrication, the carbon fibers are coated with an interfacial coating prior to application of the PCP. The structure is then cured using standard polymer matrix composite processing; it is inherently failsafe. If the TPS protecting the structure is damaged or lost, the carrier structure will convert to a CMC material when its temperature reaches 1000 °C. The converted CMC structure will maintain structural integrity, ensuring the safe completion of the mission. Because density is lost during conversion of the PCP, the ratio of polymer to ceramic particulates can be optimized to obtain acceptable densities and strengths.
The system can be used in a variety of vehicles and static structures, such as incorporation into a building to keep it structurally sound during a fire. Used in a re-entry heat shield, it costs less to produce than current heat shield systems.