Phenomenological multi-mechanisms constitutive modelling for thermoplastic polymers, implicit implementation and experimental validation

In this work, a phenomenological model for thermoplastic polymers involving several mechanisms is proposed. The constitutive equations lie within the framework of thermodynamics and account for both viscoelasticty, viscoplasticity and ductile damage. An implicit numerical scheme utilizing the “return mapping algorithm” is provided along with the formulation of the tangent operator. The parameters of the developed model are experimentally identified through a gradient-based inverse method using three strain-controlled configurations. The model validation is achieved by comparing numerical results with experimental data obtained on a cyclic loading configuration test. Finally, the capabilities of the proposed model are demonstrated with a series of numerical simulations where complex cyclic and non-proportional loading conditions are applied as well as with a structural FE application.