  Arterial tissue failures lead to a number of clinical conditions that develop
rapidly and unpredictably in vivo. Structural components and their interfacial
mechanical strength of arterial tissue play a critical role in the process of
arterail delamination. Therefore, there is a pressing need to understand the
micromechanical mechanisms of arterial delamination. The objective of this
study was to investigate various failure mechanisms (e.g. failure of collagen
fibers) responsible for arterial interfacial delamination. In-situ tensile
tests of fibers were performed on a micro-tester in the scanning electron
microscope. A 3D unit cell model containing an individual fiber bridging two
arterial tissue layers was constructed. An exponential cohesive zone model
(CZM) was used to assess the stiffening and softening mechanical behaviors of
collagen fiber bundles between the two arterial layers. An anisotropic
constitutive model was implemented for characterizing the mechanical properties
of the amorphous matrix which includes the fibrous cap and the underlying
plaque tissue and a nonlinear elastic model was adopted for characterizing the
mechanical properties of the fibers. The CZM and elastic parameter values of
fibers were identified through an inverse boundary value approach that matches
the load-displacement curves from simulation predictions of tensile test of
collagen fibers with experimental measurements. The identified parameter values
were then used as input in the 3D unit cell model, through which
micromechanical factors affecting the resultant traction-separation relation
for the unit cell were investigated via a parametric analysis. Results of the
parametric analysis showed the applicability of the 3D unit cell model approach
for evaluating the micromechanical mechanisms of arterial tissue failure
processes.
