Date of Award

6-2008

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Shankar Mall, PhD

Abstract

The inherent resistance to oxidation of oxide/oxide ceramic matrix composites makes them ideal for aerospace applications that require high temperature and long life under corrosive environments. The ceramic matrix composite (CMC) of interest in the study is the Nextel™720/Alumina (N720/A) which is comprised of an 8-harness satin weave of Nextel™ fibers embedded in an alumina matrix. One of the top applications for N720/A is in the combustion section of a turbine engine. This will require mounting and shaping the material with rivets and possibly sharp edges thereby introducing geometry based stress concentration factors. Sullivan’s research concentrated on the effects of central circular notches with a notch to width ratio (2a/w) of 0.33. This study expands upon his research to include the creep and fatigue response to double edge notch geometry with the same notch to width ratio of 0.33. In short, 12.0 mm wide rectangular specimens with two edge notches of 2 mm depth and 0.15 mm width were subjected to creep and fatigue loading conditions in 1200°C of air. All fracture surfaces were examined by an optical microscope and a scanning electron microscope. Sullivan’s research concluded that specimens with a central circular notch were insensitive to creep but slightly more sensitive to fatigue than unnotched specimens. In contrast, this study showed significant creep and fatigue life reductions for double edge notch specimens.

AFIT Designator

AFIT-GAE-ENY-08-J01

DTIC Accession Number

ADA482828

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