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

Abstract

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.

Hybrid micromechanical-phenomenological modelling of anisotropic damage and anelasticity induced by micro-cracks in unidirectional composites

“…ii) The evolution equations can be enriched or/and modified in order to account for time dependent behaviours such as visco-damage (Shahsavari et al, 2016), as well as for fatigue analyses (Hochard et al, 2006;Nouri et al, 2009). Moreover, viscoelastic mechanisms could be eventually added through a coupled formulation (Krairi and Doghri, 2014;Krasnobrizha et al, 2016;Praud et al, 2017).…”

Three-dimensional FE2 method for the simulation of non-linear, rate-dependent response of composite structures

“…The constitutive law of the matrix material is defined through a thermodynamically based phenomenological model for viscoplasticity and ductile damage in semi-crystalline polymers [33,34,11]. These materials exhibit a dissipative behavior that combines solid and fluid properties with some apparent stiffness reduction.…”

“…The linear spring and the viscoplastic branch are positioned in series. The model is formulated within the thermodynamics framework [33,11]. The state laws are obtained by differentiation of the Helmholtz potential with respect to the state variables.…”

“…4. It should be mentioned that these material parameters are motivated by the work of [11], but they do not consider the viscoelastic response, which is taken into account in that article. Thus, the material properties are related to viscoplastic behavior coupled to damage in polymeric media.…”

“…Several authors have proposed constitutive models that integrate various rheologies and deformation mechanisms, i.e. viscoelasticity [1,2], viscoplasticity [3,4,5], coupled viscoelasticity and viscoplasticity [6,7], or even both coupled viscoelasticity, viscoplasticity and damage [8,9,10,11];…”