Date of Award

6-2007

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Marina Ruggles-Wrenn, PhD

Abstract

This research investigated the interlaminar shear performance of an oxide/oxide ceramic matrix composite consisting of Nextel™ 720 fibers in a high purity, porous alumina (Al2O3) matrix. The interlaminar shear performance was observed in both tension and compression of double notched specimens (DNS) at 1200 °C. Interlaminar shear creep behavior was examined in both laboratory air and in steam environment at 1200 °C. In air, the creep stress was -6.5 MPa. In steam creep stresses included -4.0, -5.0, and -6.5 MPa. Primary and secondary creep regimes were observed in all air creep tests and the creep test in steam at -4.0 MPa. Tertiary creep was also observed in the creep tests in steam at -5.0 and -6.5 MPa. The specimens tested in creep at -6.5 MPa in air achieved run-out, defined as 100 hours at creep stress. The residual strength increased after 100 h of creep in air at 1200 °C. In the presence of steam, creep performance deteriorated rapidly and run-out was achieved only at ~50% the interlaminar shear strength. The fracture surfaces and the matrix of all samples were examined in order to determine the failure and environmental degradation mechanisms behind the reduced creep performance of the matrix in steam.

AFIT Designator

AFIT-GAE-ENY-07-J11

DTIC Accession Number

ADA470171

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