Mechanical Behavior and High‐Temperature Performance of a Woven Nicalon™/Si‐N‐C Ceramic‐Matrix Composite

Abstract

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°C. The room‐temperature fatigue limit was 160 MPa, ∼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 ∼35 MPa above the proportional limits at temperatures up to 1100°C in air. At stress levels >110 MPa, cyclic loading at 1000°C caused a more severe reduction in life, based on time, compared with sustained tension. Further life degradation was observed in the 1000°C fatigue specimens that were exposed to a salt‐fog environment. This degradation decreased the fatigue life ∼85% at the stress levels that were tested.