Effect of Prior Exposure at Elevated Temperatures on Tensile Properties and Stress-Strain Behavior of Three Oxide/Oxide Ceramic Matrix Composites

Author

Christopher J. Hull

Date of Award

3-26-2015

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Marina Ruggles-Wrenn, PhD.

Abstract

Thermal stability of three oxide-oxide ceramic matrix composites was studied. The materials studied were Nextel^TM610/aluminosilicate (N610/AS), Nextel^TM720/aluminosilicate (N720/AS), and Nextel^TM720/Alumina (N720/A), commercially available oxide-oxide ceramic composites (COI Ceramics, San Diego, CA). The N610/AS composite consists of a porous aluminosilicate matrix reinforced with laminated woven alumina N610 fibers. The N720/AS and N720/A composites consist of a porous oxide matrix reinforced with laminated, woven mullite/alumina (Nextel^TM720) fibers. The matrix materials are aluminosilicate in N720/AS and alumina in N720/A. All three composites have no interface between the fibers and matrix, and rely on the porous matrix for flaw tolerance. The N610/AS and N720/AS CMCs were heat treated in laboratory air for 100 h at 1100°C and for 10, 20, 40 and 100 h at 1200°C. The N720/A CMC was heat treated in laboratory air for 100 h at 1200°C and for 10, 20, 40 and 100 h at 1300°C. The room-temperature tensile properties of all composites were measured after each type of heat treatment. Effects of prior heat treatment on tensile strength were evaluated. Heat treatment at 1100°C had little effect on tensile strength of the N610/AS and N720/AS composites, while heat treatment at 1200°C caused dramatic loss of tensile strength. Poor strength retention after heat treatment at 1200°C is attributed to degradation of the aluminosilicate matrix. The N720/A composite exhibited excellent thermal stability, retaining about 90% of its tensile strength after heat treatment at 1300°C. Results indicate that the aluminosilicate matrix is considerably more susceptible to localized densification and coarsening of the porosity than the alumina matrix.

AFIT Designator

AFIT-ENY-MS-15-M-228

DTIC Accession Number

ADA616079

Recommended Citation

Hull, Christopher J., "Effect of Prior Exposure at Elevated Temperatures on Tensile Properties and Stress-Strain Behavior of Three Oxide/Oxide Ceramic Matrix Composites" (2015). Theses and Dissertations. 170.
https://scholar.afit.edu/etd/170