Influence of loading frequency on the room-temperature fatigue of a carbon-fiber/SiC-matrix composite

Journal Article · Wed Sep 01 04:00:00 EDT 1993 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1993.tb07772.x· OSTI ID:6081539

Shuler, S F; Holmes, J W; Wu, Xin ^[1]

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1. The Univ. of Michigan, Ann Arbor, MI (United States). Ceramic Composites Research Lab., Dept. of Mechanical Engineering and Applied Mechanics

The influence of cyclic loading frequency on the tensile fatigue life of a woven-carbon-fiber/SiC-matrix composite was examined at room temperature. Tension-tension fatigue experiments were conducted under load control, at sinusoidal frequencies of 1, 10, and 50 Hz. Using a stress ratio ([sigma][sub min]/[sigma][sub max]) of 0.1, specimens were subjected to maximum fatigue stresses of 310 to 405 MPa. There were two key findings: (1) the fatigue life and extent of modulus decay were influenced by loading frequency and (2) the post-fatigue monotonic tensile strength increased after fatigue loading. For loading frequencies of 1 and 10 Hz, the fatigue limit (defined at 1 [times] 10[sup 6] cycles) was approximately 335 MPa, which is over 80% of the initial monotonic strength of the composite; at 50 Hz, the fatigue limit was below 310 MPa. During 1- and 10-Hz fatigue at a maximum stress of 335 MPa, the modulus exhibited an initially rapid decrease, followed by a partial recovery; at 50 Hz, and the same stress limits, the modulus exhibited an initially rapid decrease, followed by a partial recovery; at 50 Hz, and the same stress limits, the modulus continually decayed. The residual strength of the composite increased by approximately 20% after 1 [times] 10[sup 6] fatigue cycles at 1 or 10 Hz under a peak stress of 335 MPa. The increase in strength is attributed in part to a decrease in the stress concentrations present near the crossover points of the 0[degree] and 90[degree] fiber bundles.

• OSTI ID: 6081539
• Journal Information: Journal of the American Ceramic Society; (United States), Journal Name: Journal of the American Ceramic Society; (United States) Vol. 76:9; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
CARBIDES
CARBON COMPOUNDS
COMPOSITE MATERIALS
FATIGUE
FIBERS
MATERIALS
MECHANICAL PROPERTIES
REINFORCED MATERIALS
SILICON CARBIDES
SILICON COMPOUNDS
STRESSES