On hyperelastic constitutive modeling of annulus fibrosus

In a recent paper, Peng et. al. [1] developed an anisotropic hyperelastic constitutive model for the human annulus fibrosus in which fiber-matrix interaction plays a crucial role in simulating experimental observations reported in the literature. Later, Goo et. al. [2] used fiber reinforced continuum mechanics theory to formulate a model in which the fiber-matrix interaction was simulated using only composite effect. It was shown in these studies that, the classical anisotropic hyperelastic constitutive models for soft tissue which do not account for this shear interaction cannot accurately simulate the test data on human annulus fibrosus. In this study, we show that the microplane model for soft tissue developed by Caner and Carol [5] can be adjusted for human annulus fibrosus and the resulting model can accurately simulate the experimental observations without accounting for fiber-matrix interaction. A comparison of results obtained from (i) a fiber matrix parallel coupling model which does not account for the fiber-matrix interaction (ii) the same model but enriched with fiber-matrix interaction, and (iii) microplane model for soft tissue adapted to annulus fibrosus with 2 families of fiber distributions is presented.