Mechanical behavior and high-temperature performance of a woven Nicalon™/Si-N-C ceramic-matrix composite

A modern ceramic-matrix composite (CMC) has been extensively characterized for a high-temperature aerospace turbine-engine application. The CMC system has a silicon-nitrogen-carbon (SI-N-C) matrix reinforced with Nicalon fibers woven in a balanced eight-harness satin weave fabric Tensile tests have demonstrated that this CMC exhibits excellent strength retention up to 1100 degrees C. The room-temperature fatigue limit was 160 MPa, similar to 80% of the room-temperature tensile strength. The composite reached run-out conditions under cyclic (10(5) cycles at 1 Hz) and sustained tension (100 h) conditions at a stress of 110 MPa, which was similar to 35 MPa above the proportional limits at temperatures up to 1100 degrees C in air. At stress levels >110 MPa, cyclic loading at 1000 degrees C caused a more severe reduction in life, based on time, compared with sustained tension. Further life degradation was observed in the 1000 degrees C fatigue specimens that were exposed to a salt-fog environment, This degradation decreased the fatigue life similar to 85% at the stress levels that were tested.