Accession Number : ADA289425

Title :   Fatigue Behavior of a Cross-Ply Metal Matrix Composite at Elevated Temperature Under Strain Controlled Mode.

Descriptive Note : Master's thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s) : Dennis, Leon B.

PDF Url : ADA289425

Report Date : DEC 1994

Pagination or Media Count : 127

Abstract : This research extends the existing knowledge of cross-ply metal matrix composites (MMC) to include fatigue behavior under strain-controlled fully reversed loading. This study investigated fatigue life, failure modes and damage mechanisms of the SCS-6/Ti-15-3, (O/9O)2s, MMC. The laminate was subjected to fully reversed fatigue at elevated temperature (427 deg C) at various strain levels. Stress, strain and modulus data were analyzed to characterize the macro-mechanical behavior of the composite. Microscopy and fractography were accomplished to identify and characterize the damage mechanisms at the microscopic level. Failure modes varied according to the maximum applied strain level showing either mixed mode (i.e. combination of both fiber and matrix dominated modes) or matrix dominated fatigue failures. As expected, higher strain loadings resulted in more ductility of the matrix at failure, evidenced by fracture surface features. For testing of the same composite laminate, the fatigue life under strain controlled mode slightly increased, compared to its load-controlled mode counterpart, using the effective strain range comparison basis. However, the respective fatigue life curves converged in the high cycle region, suggesting that the matrix dominated failure mode produces equivalent predicted fatigue lives for both control modes.

Descriptors :   *METAL MATRIX COMPOSITES, *STRAIN(MECHANICS), *FATIGUE(MECHANICS), *TITANIUM ALLOYS, STRESS STRAIN RELATIONS, FATIGUE LIFE, STRESS ANALYSIS, HIGH TEMPERATURE, LAMINATES, STIFFNESS, DAMAGE ASSESSMENT, FIBER REINFORCED COMPOSITES, THESES, STRENGTH(MECHANICS), FRACTURE(MECHANICS), MICROSCOPY, FRACTOGRAPHY, AEROSPACEPLANES, DUCTILITY, CERAMIC FIBERS, FAILURE(MECHANICS), STRENGTH WEIGHT RATIO, AEROSPACE INDUSTRY, SILICON CARBIDES.

Subject Categories : Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE