Variational Viscoelastic-Damage Model for Fiber Reinforced Soft Tissues

Connective soft tissues have a pronounced anisotropic mechanical behavior due to their internal structure, consisting of a quasi isotropic ground substance and anisotropic reinforcement based mostly in elastin and collagen fibers. The objective of this paper is to extend previously proposed model for viscoelastic materials with fiber reinforcement making it capable to represent two important phenomena: the so-called Mullins effect and the softening at excessive strains. The model is based on a variational, thermodynamical consistent framework based on an incremental potential that allows for the representation of different dissipative material by simply changing the expression of potential functions and for the obtention of symmetric constitutive tangent matrices. Numerical examples show the capability of the proposed model to mimic with appreciable accuracy the experimentally observed mechanical behavior of soft tissues.