Modelling and simulation of coupled fluid transport and time-dependent fracture in fibre-reinforced hydrogel composites

Physicochemical and mechanical stimuli can trigger fluid transport and inelastic solid deformations in the fracture process of anisotropic hydrogel composites. The underlying mechanisms for the time-dependent deformation and fracture behaviour of hydrogel composites remain elusive and poorly understood. The present work develops an anisotropic poro-visco-hyperelasticdamage model based on the theory of porous media (TPM) to analyse the relationship between the coupled time-dependent behaviours, i.e. visco-hyperelasticity and fluid transport, and the fracture behaviour of hydrogel composites. The viscohyperelasticity of the polymer networks resulting from the breaking and reforming kinetics of physical bonds is described by introducing internal variables based on the multiplicative decomposition of the deformation gradient tensor into elastic and inelastic parts. The fluid transport through the porous polymer networks is governed by Darcy's law. A continuum damage model is proposed to describe the mechanical degradation of the anisotropic hydrogel composites, e.g., the crosslink unzipping and chain scission in polymer networks as well as the damage and breaking of embedded nanofibres. An integral-type nonlocal averaging algorithm is employed in the proposed damage model to eliminate the mesh dependence of numerical simulations. Furthermore, an operator split integration algorithm and an exponential mapping algorithm are applied to integrate evolution equations for internal variables and stresses. The resulting exponential tensor function is computed via spectral decompositions. The consistent tangent operators for an implicit finite element procedure are derived in detail in this contribution. Three representative numerical examples are used to validate the proposed model and investigate the mechanisms of the time-dependent fracture behaviour of anisotropic hydrogel composites. The computational results demonstrate that the proposed model can capture the fracture behaviour of hydrogel composites with different fibre orientations. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study develops an anisotropic poro-visco-hyperelastic-damage model to analyze the time-dependent fracture behavior of hydrogel composites. The model includes the coupling relationship between visco-hyperelasticity and fluid transport and describes the visco-hyperelasticity of the polymer networks and the fluid transport through the porous polymer networks. In addition, a continuum damage model is proposed to describe the mechanical degradation of hydrogel composites. The proposed model is validated through numerical simulations.