Mechanical responses and microscopic irreversible deformation evolution of thermoplastic fiber-reinforced composites under cyclic loading

This research investigates the mechanical behavior and irreversible deformation mechanisms of thermoplastic fiber-reinforced composites. First, a nonlinear viscoelastic-elastoplastic constitutive model for the thermoplastic matrix was developed within a parallel rheological framework and calibrated using material tests. Subsequently, a three-dimensional representative volume element model, incorporating randomly distributed fibers and periodic boundary conditions, was established to accurately represent the composite microstructure. Composite specimens were fabricated and subjected to cyclic loading tests. By integrating experimental data with numerical simulations, the study analyzed the composite’s mechanical response under various cyclic loading conditions. Results indicate that stress level, stress ratio, and strain rate significantly influence the macroscopic mechanical response. Concurrently, material geometric features and multi-axial stress states substantially affect microscopic stress distributions and the evolution of irreversible deformation.