Type of Document	Dissertation
Author	Elahi, Mehran
URN	etd-06062008-154429
Title	Fatigue behavior of ceramic matrix composites at elevated temperatures under cyclic loading
Degree	PhD
Department	Engineering Mechanics
Advisory Committee	Advisor Name Title Reifsnider, Kenneth L. Committee Chair Duke, John C. Jr. Committee Member Johnson, Eric R. Committee Member Kriz, Ronald D. Committee Member Mook, Dean T. Committee Member
Keywords	life prediction ceramic matrix composites fatigue elevated temperature strength prediction life remaining strength
Date of Defense	1996-12-19
Availability	restricted
Abstract To achieve satisfactory levels of strength, fracture toughness, and reliability for man-rated systems such as jet engines, fiber reinforced ceramic matrix composites are needed. An elevated temperature axial testing system is developed to investigate and characterize fatigue behavior of Nicalon fiber reinforced enhanced silicon carbide matrix. composites at 1800 of under fullyreversed cyclic loading. Notch effect on quasi-static tensile response is also considered. Quasi-static and fatigue damage mechanisms and failure modes are examined using various specimen geometries, load levels, fatigue ratios, and laminates stacking sequences by employing a number of NDE techniques. Issues such as damage tolerance and durability are addressed by conducting interrupted fatigue tests at various stages of life for different load levels. Results are compared to the predictions of remaining strength and life, obtained using a performance simulation code. Initial results indicate existence of a threshold stress value which limits the use of the material system.
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