A Versatile Methodology for the Fatigue Life Prediction of Unidirectional Carbon Fiber-reinforced Plastic Specimens by the Micro-stress Analysis of Resins

Abstract

A versatile methodology for the fatigue life prediction of unidirectional carbon fiber-reinforced plastic (CFRP) specimens is presented to enable the optimal use of the high specific stiffness and strength of CFRP. We assumed that the fatigue life of CFRP is governed by that of its matrix resin, and employed a microscopic approach to evaluate the resin stress using a micro model, which considered the carbon fibers and resin separately. Fatigue tests were performed on the resin and unidirectional CFRP specimens by making the direction of the reinforcement to deviate 30º, 45º, 60º, and 90º from the loading axis. Fatigue life prediction was successfully performed using the interfacial normal stress (INS), which is the normal stress on a plane perpendicular to the line segment connecting the center axes of two carbon fibers. The inadequate test results for fatigue life prediction by microscopic evaluation of the first principal stress, Tresca stress, or von Mises stress demonstrate the suitability of the proposed methodology.