SEDL / STP / STP907-EB / STP19985S

Fatigue Behavior of Continuous-Fiber Silicon Carbide/Aluminum Composites

Johnson, WS
Senior research engineer, NASA Langley Research Center, Hampton, VA

Wallis, RR
Engineer, Foster-Miller, Inc., Waltham, MA
a co-op student, Virginia Polytechnic and State University, Blacksburg, VA

Pages: 15    Published: Jan 1986

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Abstract

Four layups of continuous-fiber silicon carbide (SCS²) fiber/aluminum matrix composites were tested to assess fatigue mechanisms, including stiffness loss, when cycled below their respective fatigue limits. The layups were [0]⁸, [0²/±45]^s, [0/90]^2s, and [0/±45/90]^s. The data were compared with predictions from the first author's previously published shakedown model which predicts fatigue-induced stiffness loss in metal matrix composites. A fifth layup, [±45]^2s, was tested to compare the shakedown and fatigue limits. The particular batch of silicon carbide fibers tested in this program had a somewhat lower modulus (340 GPa) than expected and displayed poor bonding to the aluminum matrix. Good agreement was obtained between the stiffness loss model and the test data. The fatigue damage below the fatigue limit was primarily in the form of matrix cracking. The fatigue limit corresponded to the laminate shakedown limit for the [±45]^2s laminate.