Speaker
Description
When fibre-reinforced soft biological tissues undergo biaxial tension, it is generally assumed that both in-plane stretches will increase monotonically with the applied stress. However, under specific combinations of fibre architecture and loading biaxiality, a counterintuitive kinematic phenomenon of stretch reversal may occur, where one principal stretch reaches a local maximum and subsequently decreases, even as the applied biaxial loads continue to grow.
We develop a unified analytical framework to define the specific conditions under which this reversal occurs in anisotropic hyperelastic materials. Our findings indicate that stretch reversal arises from a fundamental geometric competition between the compliant isotropic matrix, the anisotropic fibre reinforcement, and the incompressibility constraint. Specifically, using an exponential constitutive model, we identify a critical fibre stiffness threshold that separates a regime of immediate transverse contraction from one permitting stretch reversal.
To bridge theoretical predictions with experimental testing, we implement a finite element formulation for cruciform specimens and compare our computational predictions with experimental biaxial testing data from soft tissues. Finally, we demonstrate how the high sensitivity of this reversal phenomenon to fibre architecture can be actively exploited to formulate a robust, sequential parameter-identification strategy.