Rate-dependent behavior of connective tissue through a micromechanics-based hyper viscoelastic model

In this paper, a micromechanical study on rate-dependent behavior of connective tissues is performed. To this end, a hyper viscoelastic constitutive model consisting a hyperelastic part for modeling equilibrium response of tissues and a viscous part using a hereditary integral is proposed to capture the time-dependent behavior of the tissues. With regard to the hierarchical structure of the tissue, strain energy function are developed for modeling elastic response of the tissue constituents i.e. collagen fibers and ground matrix. The rate-dependency is incorporated into the model using a viscous element with rate-dependent relaxation time. The proposed constitutive model is implemented into ABAQUS using the UMAT subroutine. Results of the presented micromechanics model are compared and validated with the available experimental data and also the quasi-linear viscoelastic (QLV) theory at different strain rates. It was found that the proposed model could well predict the behavior of the connective tissues in wide range of strain rates. Results show that, the presented model contains less constitutive parameters and leads to more accurate results in comparison with the QLV.