A micromechanical model for loading and unloading behavior of fiber reinforced plastics under cyclic loading

Abstract The high fatigue resistance and low weight features make the unidirectional‐carbon fiber reinforced plastics (UD‐CFRP) attractive for cyclic loading applications. However, the complex damage mechanisms within the composite hinder the understanding of its fatigue response. An energy‐based fatigue model has been proposed for the fatigue behavior of epoxy polymers. However, this kind of approaches dependent on the accurate description of the material's behavior. Our work aims to build a representative volume element model (RVE) for the simulation of the cyclic shear loading behavior of UD‐CFRP, which could support the later extension of an energy‐based fatigue model. To precisely reproduce the micromechanical stress‐strain distribution within the matrix, a nonlinear viscoelastic model has been implemented and validated against experimental data. As a result, the simulated UD‐CFRP hysteresis, as well as the stiffness and strain energy density were accurately reproduced for two load ratios (R = 0.1 and R = − 1). Additionally, the cyclic strain accumulation observed in the UD‐CFRP can be accurately described by the proposed model.