Thermal shock behavior of Nicalon™ fiber SiCN ceramic matrix composites

Ceramic matrix composites consisting of Nicalon™ fiber reinforced SiCN matrix manufactured by the Polymer Impregnation Pyrolysis (PIP) process are subjected to thermal shock by the water quenching technique. Thermal shock behavior is assessed by both destructive and nondestructive techniques. Nondestructive evaluation of damage mechanism was performed using Acoustic Emission (AE) technique. With the aid of AE, it is observed that the degradation in the mechanical properties of the composite due to thermal shock is directly related to the corresponding degradation in constituent properties and associated degradation mechanisms. AE monitoring shows a significant difference in AE signals when this composite is subjected to shocking temperatures beyond the critical thermal shock temperature. The effect of both the temperature and thermal shock cycles on the mechanical properties of this composite has been evaluated. As the temperature and the thermal shock increase, the AE events for the monotonic tensile test increase. The AE signal has been correlated to the load displacement curve in the time domain in order to explain the types of damage in the specimen.