Creep Rupture and Fatigue Behavior of a Notched Oxide/Oxide Ceramic Matrix Composite at an Elevated Temperature

Abstract

Oxide/oxide ceramic matrix composites (CMCs) have the potential to provide a longer lifetime and better strength when subjected to thermomechanical loads due to their inherent resistance to oxidation. Different notches are usually required during their applications. Their time‐dependent behavior in the presence of a notch must therefore be characterized. This study investigated the creep rupture and fatigue behavior of a woven oxide/oxide CMC (N720/A) consisting of Nextel™720 (metastable mullite) fibers in an alumina matrix with a 0°/90° fiber orientation having a hole diameter to width ratio of 0.33 at 1200°C in a laboratory air environment. Monotonic tensile tests at 1200°C were also conducted. Fracture surfaces were examined to analyze failure and damage mechanisms. Comparisons with unnotched data showed N720/A to be insensitive to the notch (hole) under monotonic tensile, creep, and fatigue‐loading conditions. Deformation under the cyclic loading condition was affected by fatigue and creep; however, the damage mechanisms were the same under creep and fatigue‐loading conditions.