Tufan Yeleser

Date of Award

9-2008

Document Type

Thesis

Degree Name

Master of Science in Astronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Marina B. Ruggles-Wrenn, PhD

Abstract

The creep behavior of six oxide-oxide ceramic-matrix composites (CMCs) was investigated at 1100 °C in laboratory air and in steam environments. The six CMC systems had an alumina ( Al2O3 ) matrix reinforced with NextelTM610 fibers. The CMC systems C1, C2 and C3 were reinforced with 10 uni-directional fiber layers in a symmetric cross-ply (0°/90°/0°/90°/0°)s orientation. In the case of composites C2 and C3, monazite (LaPO4) fiber coating was applied to the fibers. Composite C1 contained no fiber coating. In the case of composites C1 and C2, alumina matrix was infiltrated with monazite. The CMC systems C4, C5, and C6 were reinforced with 8 plies of fiber fabric woven in a balanced eight-harness satin weave (8HSW). In the case of composites C4 and C6, monazite (LaPO4) fiber coating was applied to the fibers. Composite C5 contained no fiber coating. In the case of composite C6,alumina matrix was infiltrated with AlOCl. The tensile stress-strain behaviors of the six CMC systems were investigated,and the tensile properties measured at 1100 °C. Different methods used to apply the monazite coating to the uni-tape cross-ply composites, and the woven composites were the likely cause of reduced strength of the woven CMCs. Creep performance of all six CMC systems was noticeably degraded in steam. The presence of steam accelerated creep rates and significantly reduced creep lifetimes. In air, creep run-out, defined as 100 h at creep stress, was achieved for composites C4 and C6. In steam, creep run-out was not achieved. Results reveal that for a given fiber architecture and fiber coating method, the use of the monazite coating resulted in considerable improvement in creep resistance at 1100 °C in both air and steam environments. Composite microstructure, as well as damage and failure mechanisms were investigated.

AFIT Designator

AFIT-GA-ENY-08-S01

DTIC Accession Number

ADA487638

Download

Share

COinS