SEDL / STP / STP580-EB / STP32324S

Frequency Effects on Flawed-Composite Fatigue Reliability

Reifsnider, KL
Associate professor, assistant professor, and graduate students, Virginia Polytechnic Institute and State University, Blacksburg, Va.

Stinchomb, WW
Associate professor, assistant professor, and graduate students, Virginia Polytechnic Institute and State University, Blacksburg, Va.

Williams, RS
Associate professor, assistant professor, and graduate students, Virginia Polytechnic Institute and State University, Blacksburg, Va.

Turgay, HM
Associate professor, assistant professor, and graduate students, Virginia Polytechnic Institute and State University, Blacksburg, Va.

Pages: 18    Published: Jan 1975

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Abstract

Variations in the degradation and subsequent fatigue reliability of laminated composite plate specimens with a center hole due to changes in cycle frequency have been identified and investigated. Boron-epoxy and boron-aluminum specimens were examined, principally for stiffness and strength variations. Various combinations of stiffness and strength changes were observed as a function of cycle frequency and specimen material, including a mode wherein stiffness decreased significantly while residual strength increased. A kinetic damage model was developed and combined with a Weibull extreme value expression to attempt to represent the stochastic aspects of the fatigue process. The model shows some promise, especially from the standpoint of representing widely varying fatigue behavior, including the unusual situation of stiffness drop with strength increase. Frequency dependence is included in the model.