Nanomodified Carbon/Carbon Composites for Intermediate Temperature

An improved Carbon/Carbon Composite (CCC) with enhanced thermo-oxidative resistant performance at intermediate temperatures (371 to 650 C) is being developed. A nanophase is introduced into the CCC prior to cure for improved and maintained mechanical strength by preventing oxidation of the CCC. Four material systems based on Lonza PT-15 cyanate ester (CE) resin and selected nanoparticles were chosen to produce prepregs. They were fabricated into composites for carbonization and densification to produce nanomodified CCC using CVI process. Two sets of 30.48 by 30.48 by 0.38 cm NCCC panels were fabricated. Ten material systems based on synthetic AR mesophase pitch and silicon carbide nanoparticles in two groups were also selected to produce CCC using the SMJ patented in-situ polymerization method. Two sets of 15.25 by 15.25 by 0.32 cm CCC panels were fabricated for these two groups. A C/C and a C/SiC type composites fabricated by DACC of Korea were included for comparison. Microstructure analyses of pre- and post-test CCC specimens using SEM and optical microscopy provided more fundamental understanding of material behavior. The nanomodified CE CCC (PT15/30B, PT15/Im and PT15/P0SS) are more thermo-oxidative resistant than the baseline CCC (PT15). With TGA for heat soaking in air environment, the DACC C/SiC composite exhibited the best performance and the AR mesophase pitch/SiC impregnated with Ceraset (trademark) exhibited the most thermo-oxidative resistant NCCC. It was followed by the AR mesophase pitch/SiC NCCC. The nanomodified PT-15 CE NCCC is the most unfavorable of the three NCCC groups. The density of the NCCC and the percentage loading of SiC nanoparticles appear to be the most important factors determining the thermo-oxidative properties of NCCC within the same group. Prepared in cooperation with University of Texas at Austin, Dept. of Mechanical Engineering, Austin, TX.