Date of Award


Document Type


Degree Name

Master of Science in Aeronautical Engineering


Department of Aeronautics and Astronautics

First Advisor

Marina Ruggles-Wrenn, PhD.


Thermal stability of three oxide-oxide ceramic matrix composites was studied. The materials studied were NextelTM610/aluminosilicate (N610/AS), NextelTM720/aluminosilicate (N720/AS), and NextelTM720/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 (NextelTM720) 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


DTIC Accession Number