Application of fiber bridging models to fatigue crack growth in unidirectional titanium matrix composites
Several fiber bridging models were reviewed and applied to study the matrix fatigue crack growth behavior in center notched (0)(sub 8) SCS-6/Ti-15-3 and (0)(sub 4) SCS-6/Ti-6Al-4V laminates. Observations revealed that fatigue damage consisted primarily of matrix cracks and fiber matrix interfacial failure in the (0)(sub 8) SCS-6/Ti-15-3 laminates. Fiber-matrix interface failure included fracture of the brittle reaction zone and cracking between the two carbon rich fiber coatings. Intact fibers in the wake of the matrix cracks reduce the stress intensity factor range. Thus, an applied stress intensity factor range is inappropriate to characterize matrix crack growth behavior. Fiber bridging models were used to determine the matrix stress intensity factor range in titanium metal matrix composites. In these models, the fibers in the wake of the crack are idealized as a closure pressure. An unknown constant frictional shear stress is assumed to act along the debond or slip length of the bridging fibers. The frictional shear stress was used as a curve fitting parameter to available data (crack growth data, crack opening displacement data, and debond length data). Large variations in the frictional shear stress required to fit the experimental data indicate that the fiber bridging models in their present form lack predictive capabilities. However, these models provide an efficient and relatively simple engineering method for conducting parametric studies of the matrix growth behavior based on constituent properties.
- Research Organization:
- National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center
- OSTI ID:
- 6906077
- Report Number(s):
- N-92-33900; NASA-TM--107588; NAS--1.15:107588; CNN: RTOP 763-23-41-85
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360603* -- Materials-- Properties
ALLOYS
ALUMINIUM ALLOYS
BRITTLENESS
CARBIDES
CARBON COMPOUNDS
CARBON FIBERS
COMPOSITE MATERIALS
CRACK PROPAGATION
CRYSTAL STRUCTURE
FATIGUE
FIBERS
FRACTURE MECHANICS
FRACTURING
FRICTION FACTOR
MATERIALS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
MECHANICS
MICROSTRUCTURE
NOTCHES
SHEAR PROPERTIES
SILICON CARBIDES
SILICON COMPOUNDS
STRESS INTENSITY FACTORS
TITANIUM ALLOYS
VANADIUM ALLOYS