A Viscoelastic Anisotropic Model for Soft Collageneous Tissues Based on Distributed Fiber–Matrix Units

Abstract

AbstractIn this contribution, a nonlinear anisotropic model for the viscoelastic behavior of soft biological tissues is presented. The model is based on micromechanical considerations that take into account the interplay between collagen fibers and the surrounding ground substance. To this end, the stretch along a collagen fiber is multiplicatively decomposed into a part relating to the straightening of the crimped fibers and a part describing the stretch in the fiber itself. The current straightening state of the fibers is described by internal variables. Including a nonuniform distribution of the collagen fibers, the anisotropic three-dimensional constitutive equations are obtained by integration over the unit sphere. The model is applicable for large strains, describes both time and rate dependent behavior and allows to account for particular viscoelastic characteristics of various soft tissues. The performance of the model is illustrated by uniaxial tension as well as sinusoidal simple shear tests and compared to recently published experimental data on ligament tissue.KeywordsAnterior Cruciate LigamentCollagen FiberInternal VariableViscoelastic BehaviorStrain Energy FunctionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.