Effect of fiber hybrid mode on fatigue life and failure mechanism of C/GFRP hybrid rod

Fatigue load is one of the main factors leading to the brittle failure of fiber reinforced polymer (FRP) composites and their reinforced structures, systematic research on fatigue performance is essential to ensure the safe service of FRP composites. In the present paper, the effects of fiber hybrid mode and stress level on fatigue performances of carbon/glass fiber reinforced polymer (C/GFRP) hybrid rod are investigated experimentally. The fatigue limit and damage evolution are obtained to evaluate the fatigue resistance of hybrid rod, the influence mechanism of fiber hybrid mode on the fatigue failure of hybrid rod is revealed. The fatigue design parameter of hybrid rod with a 95% confidence level is obtained for the engineering application. The results show that the carbon fiber in the shell of fiber coating rod (CGH) bears the main fatigue loading, which significantly improves the fatigue limit about 19.7% and 113.5% compared with fiber uniformly hybrid rod (UDH) and fiber coating rod (GCH), respectively. Moreover, the bridging effect of glass fiber effectively improves the ductility of UDH during fatigue failure process. The fatigue failure mode of hybrid rod at high stress levels is similar to that of static failure, and the fatigue damage originates from the fracture of carbon fiber. The hybrid rod presents progressive damage failure mode at low stress level, and the fatigue damage originates from the interfacial debonding. S-N curve with probability distribution is established based on probabilistic tools of Weibull distribution, which provides the fatigue design parameter with 95% confidence for the engineering application.