| Ceramic materials and newer ceramic matrix composites (CMCs) have now been employed in many high temperature applications. However, tensile strength, toughness, and susceptibility of thermal shock can be limiting factors of these materials. This research program was conducted to characterize the creep behavior of thin Nextel-312{dollar}sp{lcub}rm TM{rcub}{dollar}/Blackglas{dollar}sp{lcub}rm TM{rcub}{dollar} ceramic matrix composites. The testing parameters that varied in this study were: (1) pyrolysis temperature, (2) pyrolysis environment, (3) oxidation time and (4) stress. Testing was done in a 4-point bend configuration in accordance with MIL-STD-1942A. Scanning electron microscopy (SEM) work was utilized to identify and understand the mode of failure. The results of these tests gave conclusive results and indicate that this CMC, with all other conditions the same, has about twice the strain to failure when pyrolyzed at 872{dollar}spcirc{dollar}C as opposed to 982{dollar}spcirc{dollar}C. Test specimens pyrolyzed in ammonia (NH{dollar}sb3{dollar}) tended to have a much greater time to failure than those pyrolyzed in argon. These results demonstrate the importance of the processing of this CMC. |
