Abstract
In order to clarify S-N properties of carbon fiber, fatigue tests were investigated over a range of stress ratio, R, from 0.1 to 0.7Hz. The carbon fibers used were standard T300 fibers produced from polyacrylonitrile precursors by Toray Industries, Japan. It was found that the S-N properties of the carbon fibers clearly show the fatigue behavior, depending on the stress ratio R. It was also found that fatigue strength of carbon fiber is governed by two parameters such as the maximum stress σ_<max> and the stress amplitude σ_a, and that the combined stress parameter σ_<max>^<1-α>×σ_a^α is useful to describe the fatigue strength behaviors of the different stress ratios. Mirror-mist-hackle features were clearly observed on the fracture surface of specimens. It was confirmed that the relation σ_<max>・A^<1/4>=const. holds between the mirror or mist area, A, and the maximum stress, σ_<max>.
