Development of an Understanding of the Fatigue Phenomena of Bonded and Bolted Joints in Advanced Filamentary Composite Materials. Volume 3. Fatigue Analysis and Fatigue Mode Studies.
LOCKHEED-GEORGIA CO MARIETTA
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This report presents the results of the empirical program undertaken to increase the basic understanding of the fatigue phenomena of advanced composites joints. Four basic design concepts have been evaluated and include both bonded and mechanically fastened joints. A broad spectrum of joint geometry variations and loading conditions are included to identify the significant parameters affecting the fatigue endurance of composite joints. Test data and analyses are included for constant amplitude testing and program fatigue loading. Realistic spectrum and block spectrum data are evaluated using Miners Cumulative Damage Theory. In conjunction with other analyses and evaluations, failure mode studies were conducted on the fracture surface of failed specimens. Scanning electron microscope SEM photomicrographs were used for this failure study. Specific failure modes related to specimen configuration, loading conditions, and fatigue history were defined. Failure modes that have been identified and related to loading conditions include shear in the resin versus load direction and stress ratio R peel in the laminate due to a cleavage load peel or tension fracture due to tension-tension fatigue. Some specimens subjected to complex loading exhibited multiple failure modes.
- Couplers, Fasteners and Joints
- Physical Chemistry
- Laminates and Composite Materials