TRI Austin will demonstrate that the volumetric heating response of reinforcing SiC fibers and carbon fibers (CFs) can be utilized for processing SiC-SiC and SiC-C composites using the polymer infiltration and pyrolysis (PIP) method. Volumetric heating methods allow for more uniform and out-of-furnace processing of ceramic matrix composites (CMCs). Although preceramic polymers have low electrical conductivity and poor dielectric properties, the addition of susceptor fillers can enable their volumetric heating. This approach offers uniform volumetric and localized heating and thus better and more uniform mechanical properties of the final products, while at the same time, lowering the cost of CMC manufacturing and reducing processing time, energy consumption and carbon footprint. Volumetric heating can be used to control thermal distribution in composite preforms and prevent cracking or entrapment of gases formed during high temperature reactions. Since this approach can be carried out in an out-of-oven setup, the prospect for repeatable, layered deposition means that this concept could form the basis for an additive manufacturing technology.
Benefit: We expect major reductions in capital cost because the hardware can have a smaller footprint and the heating and cooling times are greatly reduced compared to conventional furnaces. The volumetric heating method can reduce the processing time for PIP as the pre-heating and cooling time required for furnaces are eliminated, and potentially reduce the number of PIP cycles to achieve comparable levels of densification. Also, the energy efficiency of volumetric heating is higher compared to that of conventional furnaces, due to minimized heat loss, elimination of convective heat transfer, and higher temperature ramp rates. In addition, the potential of improving matrix microstructure by enhanced densification with volumetric heating could decrease the rejection rate of mechanically nonperforming fabricated CMC parts. DoD has already recognized the potential impact of selective heating techniques that deliver energy directly where it is needed rather than heating the environment, in lowering energy use, emissions and manufacturing costs, and enabling the manufacture of improved materials. This project will help overcome existing challenges and barriers for implementing these technologies and for achieving technical targets and increasing TRL. Transition efforts will be directed toward development of a robust AM TPS manufacturing process and material resulting in weather-resistant, thermally conductive, and easily fabricated TPS materials for hypersonic vehicles/munitions. Other high temperature missile applications will see a potential for an improved TPS material such as Navy, Air Force, and Army missiles. The HTPS composites will have applicability in heat shielding applications and TPSs. The new class of high temperature composites has many DoD and commercial market/revenue segments from the Navy VLS, rocket nozzles and high temperature atmospheric reentry vehicles. NASA is going to need new lightweight heat shielding materials for planetary exploration missions.
Keywords: Thermal Resistance, Thermal Resistance, Conductive, reentry vehicles, Thermal protection system, SiC-SiC, C-C, Weather-resistant, hypersonic
