Creep-Rupture and Fatigue Behaviors of Notched Oxide/Oxide Ceramic Matrix Composite at Elevated Temperature

摘要

Oxide/oxide composites are being considered for use in high temperature aerospace applications where their inherent resistance to oxidation provides for better long life properties at high temperature than most other ceramic matrix composites (CMCs). One promising oxide/oxide CMC is Nextel 720/A (N720/A) which uses an 8-harness satin weave (8HSW) of Nextel 720 fibers embedded in a porous alumina matrix. Possible aerospace applications for N720/A will likely require inserting holes into the material for mounting and cooling purposes. The notch characteristics must be understood to ensure designs using the material are sufficient for the desired application. This research effort examined the fatigue and creep-rupture characteristics of N720/A with a 0 /90 fiber orientation and notch to width ratio (2a/w) of 0.33. Specifically, 12.0 mm wide rectangular specimens with a 4.0 mm center hole were subjected to axial fatigue and creep-rupture loads in 1200 C laboratory air. Monotonic tensile tests at 1200 C were performed on unnotched specimens to provide a baseline for comparison with previous research. Fracture surfaces were examined under microscope to observe microstructure and damage mechanisms. Comparisons to previous unnotched research results at 1200 C show N720/A to be primarily insensitive to 0.33 notch ratios.