Influence of Loading Frequency on the Fatigue Behavior of Fiber-Reinforced Ceramic Composites
Final rept. 1 Mar 97-31 Aug 97
MICHIGAN UNIV ANN ARBOR CERAMIC COMPOSITES RESEARCH LAB
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The AFOSR funded two year project which expires March 1, 1997 addresses the effect of loading frequency and friction heating on the ambient temperature fatigue life of continuous fiber ceramic matrix composites CFCMCs. The project, which involves mechanics modeling, mechanical testing and microscopy, examined several composite systems and has provided details concerning the damage mechanisms that occur during high frequency fatigue. The current research effort of high-frequency fatigue has been performed at the Ceramic Composites Research laboratory, in the Mechanical Engineering and applied Mechanics Department at the University of Michigan. 1. Soft matrix composites with strong interface bonding were shown to provide superior resistance to high frequency fatigue damage. 2. thick fiber coatings were more effective in reducing the amount of fiber wear and damage which occur during high frequency fatigue. 3. The effect of laminate stacking sequence has a profound effect on high frequency fatigue behavior of CFCMCs. 4. Surface roughness in Nicalon fibers can be determined using Atomic force Microscopy AFM. 5. Elongated crystalline grains and a small volume fraction of whiskers in the matrix can improve the high frequency fatigue behavior of CFCMCs. 6. Loading rate was found to significantly effect monotonic tensile behavior of CFCMCs.
- Laminates and Composite Materials