Date of Award
Master of Science in Aeronautical Engineering
Department of Aeronautics and Astronautics
Marina B. Ruggles-Wrenn, PhD.
Creep behavior of an oxide-oxide ceramic matrix composite (CMC) containing an array of effusion holes was investigated at 1200⁰C in air and in steam. The composite (N720/A) consisted of a porous alumina matrix reinforced with alumina-mullite NextelTM 720 fibers. Test specimens had an array of 17 effusion holes with 0.5-mm diameter. The effusion holes were drilled through the specimen thickness normal to the specimen surface using a CO2 laser. Effect of the effusion holes on tensile properties was evaluated tension tests to failure at 1200°C in air. Creep of specimens with effusion holes at 1200°C was studied for creep stresses ranging from 40 to 100 MPa in air and from 30 to 90 MPa in steam. Creep run-out was defined as 100 h creep stress. Effect of the laser-drilled effusion holes on creep was assessed by comparing the results of the present study with the results from prior work on unnotched N720/A specimens. The presence of laser-drilled holes significantly reduced creep lifetimes in both air and steam. Post-test microstructure of the composite was examined; damage and failure mechanisms were assessed. Dramatic loss of creep resistance in specimens with holes is due to extensive composite degradation caused by laser drilling.
DTIC Accession Number
Minor, Savannah N., "Creep of Nextel 720/a Ceramic Matrix Composite with Laser Drilled Effusion Holes at 1200°C in Air and in Steam" (2018). Theses and Dissertations. 1778.