Progressive fatigue damage model for FRP wires under longitudinal cyclic tensile loading

This paper develops a progressive fatigue damage model to study the initiation and progression of fiber damage in the unidirectional FRP considering the boundary effect. A characteristic representative volume element is proposed and a damage indicator describing the loss of load carrying capacity of fiber elements is introduced and combined with the principle of superposition to realize the stress redistribution caused by fiber breakage; the maximum fatigue stresses of the neighboring fiber elements affected by fiber breakage are updated. Monte Carlo simulation is conducted to study the fatigue behavior of FRP wires considering the effect of variabilities in the static strength and the fatigue life of single fibers. Results indicate that the proposed model can predict the fatigue life and stiffness degradation of FRP wires well compared with the experimental data. Specifically, the cluster sizes of critical damage for FRP wires during the fatigue process can be determined, which provides quantitative information for the fatigue mechanism of the FRP wires.