Date of Award

12-1994

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

Abstract

This research extends the existing knowledge of MMC fatigue damage mechanisms by studying the tension-compression fatigue behavior of a notched cross-ply laminate MMC at elevated temperature. A [0-90]2S SCS-6-Ti-15-3 laminate with a center hole was subjected to tension-compression fatigue at 427 °C (800 °F). Stress and strain data was taken to evaluate macro-mechanic behavior of the material. Microscopy and fractography were performed to characterize the damage on a micro-mechanical level. Crack initiation and progression was monitored using acetate face replicas. Four cracks were found to develop around the periphery of the hole, two of which became dominant and proceeded through to the end of the specimen. On a maximum applied stress basis, tension-compression notched specimens had shorter fatigue lives than tension-tension notched specimens. Also, tension-compression adds more damage due to the compressive portion of the loading, and tension-compression loading increased the time to crack initiation for a given maximum stress and increased the rate of crack propagation over tension-tension cases.

AFIT Designator

AFIT-GAE-ENY-94D-8

DTIC Accession Number

ADA291479

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