Fatigue damage and microstructure evolution of soft collagenous tissues

Abstract

Soft collagenous tissues suffer fatigue damage with symptoms of reduced stiffness and residual deformation. Here we use bovine pericardium as a model tissue to study the fatigue damage and microstructure evolution through experiments and modeling. We propose an experimental method to characterize the fiber distribution during cyclic loading, and find that the evolution law satisfies an exponential function. We further establish the fatigue damage model by incorporating the evolution law of fiber dispersion degree, fiber stiffness and residual deformation into the constitutive model of soft tissues. The fatigue damage model can accurately predict the stress-stretch curves of bovine pericardium within 200,000 cycles. It is found that a larger stretch amplitude induces more fatigue damage with more severe fiber reorientation and stiffness reduction. The initial fiber orientation of tissues greatly influences fatigue damage, and microscopic observations are conducted to analyze the effect. This work incorporates the microstructural evolution into the phenomenological framework to quantify the fatigue damage behavior, and may help to understand the damage process of biological tissues.