Date of Award

3-12-2008

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Marina B. Ruggles-Wrenn, PhD

Abstract

The creep behavior of an oxide-oxide ceramic matrix composite (CMC) was investigated at 1200°C in laboratory air, in steam and in argon. The composite consisted of a porous alumina-mullite matrix reinforced with laminated, woven mullite/alumina (Nextel/720) fibers. The composite had no fiber coating and relied on its porous alumina/mullite matrix for flaw tolerance. Tensile stress-strain behavior was investigated and the tensile properties were measured at 1200°C in laboratory air. Tensile creep behavior of the CMC was examined for creep stress levels of 73, 91, 114 and 136 MPa. Creep run-out, set to 100 h, was achieved for stress levels ≤ 91 MPa in air. The presence of steam or argon accelerated the creep rates the N720/AM composite. Optical and scanning electron microscope (SEM) micrographs were used to examine fracture surfaces and to evaluate failure mechanisms. Fracture surfaces of the N720/AM composite were predominately planar. Limited areas of short fiber pull-out were observed for specimens tested at low creep stress levels in air.

AFIT Designator

AFIT-GAE-ENY-08-M11

DTIC Accession Number

ADA478784

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