Cohesive Zone Model Analysis, Development, and Application in Mixed-Mode Arterial Dissection

Recent studies have presented evidence that aortic dissection entails mode II and mixed-mode crack growth. In the present chapter we analyze the mixed-mode behavior of two exponentially softening path-dependent cohesive zone models (CZMs). We demonstrate that these models provide physically realistic tractions and positive incremental dissipation during proportional and non-proportional loading paths. In contrast, we demonstrate that potential-based path-independent CZMs can potentially result in the calculation of physically unrealistic repulsive normal tractions and negative incremental dissipation. Our recent experiments suggest that mode II fracture strength of the aorta in the circumferential-axial plane is significantly higher than the mode I strength in the same plane. We demonstrate that such anisotropic interface behavior renders potential-based CZMs unsuitable for simulation of aortic dissection. Using our new non-potential path-dependent CZM we simulate aortic dissection due to the presence of a notch in the radial-axial plane of the aorta. Simulations suggest that significant dissection propagation only occurs in cases of extreme hypertension. Additionally, we demonstrate that blood pressure loading in a false lumen will result in a mixed-mode traction state at the crack tip, with significant crack-tip blunting acting as a toughening mechanism against significant propagation of the false lumen.