Fatigue Life Estimates in Woven Carbon Fabric/Epoxy Composites at Non-Ambient Temperatures

Abstract

The influence of temperature on fatigue resistance of Plain Weave Woven CFRP isexamined. The 8-ply laminateswere obtained from epoxy resin prepreg fabric layers stacked in two different sequences, producing unidirectional [0]8 and angle plied [0, 0, 45, −45]s orientations. The fatigue tests were carried out at −20, 0, 24, 100 and 150°C. It wasfound that there wasno change in sequence of damage eventsbut duration of each event and hence cumulative damage rateswere different at different temperatures. The fatigue life at elevated temperature was found to decrease with increasing temperature but decreasing temperature below ambient conditions caused an increase in fatigue life for both classes of woven laminates. An analytical model based on stiffness degradation during cyclic loading, which isused in fatigue life prediction of CFRP at ambient temperature conditions has been successfully employed to estimate fatigue lives of WCFRP at non-ambient temperatures. A parameter Dcritical, which isa function of testing temperature, and represents the least stiffness value in modulus degradation curve, was introduced. Estimates of fatigue lives were compared with experimentally determined fatigue lives. Reasonably good correlation has been obtained between calculated and experimentally determined values of fatigue at all test temperatures considered in the present investigation.