Compressive Creep Behavior of Nextel TM 720/Alumina Ceramic Matrix Composite at 1200 Degrees C in Air and in Steam Environment

The aerospace community continues to push the envelope in engineering aircraft that fly higher, faster, and safer while operating with a greater degree of efficiency. To meet these operational requirements innovative aerospace components must be designed to operate in aggressive environments. The effects of creep loading history on the tensile and compressive material behavior will also be examined. The primary strengths of the N720/A composite are its oxide/oxide composition which inherently resists oxidation and a porous matrix which enables crack deflection producing enhanced matrix damage tolerance. Mechanical testing showed a significant decrease in the compressive performance of N720/A when exposed to steam environment. Conversely, N720/A specimens tested in compressive creep in air experienced an increase in compressive performance. SEM analysis showed that densification of the -alumina matrix occurred in both test environments. In air densification sinters the matrix resulting in a strengthening effect. Whereas, in steam environment analysis shows the addition of hydrogen induces hydrothermal softening of the matrix resulting in a significant loss of the compressive performance of N720/A.