HfB2-filled Braided C/SiC Nozzles for High Performance DACS

"FMI has recently demonstrated that light weight, potentially low cost carbon fiber reinforced silicon carbide ceramic matrix composites can survive simulated DACS environments under 3700F propellant testing. Higher temperature capabilities are sought toattain performance advantages afforded by higher temperature propellants. Ultra High Temperature Ceramics in the composition range ZrB2-HfB2-SiC have been proven in recent years to be highly effective in re-entry body applications. Still, these ceramicshave been shown to be prone to catastrophic failure. Only fiber reinforced ceramic matrix composites are likely to withstand the thermal shock and operational vibration loading present in DACS applications. We propose to examine the potential of anenhanced C/SiC composite that makes use of hafnium diboride particulate additives to a commercial silicon carbide polymer precursor. Thin wall braided carbon fiber preforms will be rigidized with a CVD derived carbon interphase coating. The preform willthen undergo repeated filled polymer impregnation cycles to densify the interstitial space with a composite matrix of HfB2/SiC. A hermetic surface coating will be applied using further liquid phase processing to achieve a higher temperature CMC. A pair ofPhase I optimized DACS nozzle test articles will be made available for testing. Lightweight higher temperature nozzle components for improved DACS systems would allow for increased acceleration a