A Constitutive Model for Anisotropic Soft Biological Tissue Subject to Mechanical Damage

Many soft biological tissues have the important task of transmitting necessary forces to control movements, hold organs in place or ensure a relatively continuous flow of fluids. Examples of these tissues are ligaments, tendons, skin and blood vessels. Biological tissues can be seen as composite materials whose constituents are assembled into a hierarchical structure. At a macroscopic structural level, the main structural elements of such tissues are the bundles of fibers that provide mechanical resistance and viscoelastic anisotropic behavior. This paper intends to extend a previously proposed anisotropic viscoelastic model in order to include mechanical damage that may be experimentally observed on biological tissues subject to large strains. The material model is based on a variational thermodynamically consistent framework, in which a local minimization provides the internal variables updates for each load increment. The main advantage of this model is its capability to represent the mechanical behavior of different materials depending on the choice or construction of potential functions. Numerical examples are presented in order to illustrate the features of the proposed model.