Composite model of healthy arterial wall : material identification based on uniaxial traction tests and morphometric analysis

During a cardiac cycle, the radius of an elastic artery may undergo a variationof about 10% so that the arterial wall is subjected to relatively large deformation.This deformation may change the orientation of fibrous componentsincluded in the arterial wall and leads to interaction between the wall microcomponents.Thus the macroscopic properties of the tissue may changeentirely. Hence, in order to describe properly the mechanical behavior ofhealthy arterial wall, we employ the fibre reinforced composite macroscopicmodel. According to the histological analysis of healthy arteries, the solidmechanical properties of the arterial wall are determined primarily by thetunica media and the tunica adventitia. Consequently, we model the elasticartery as a two-layer thick-wall cylindrical tube where each layer is treated as acomposite of two constituents: the passive fibres (representing the collagen orelastin fibres) embedded in the isotropic matrix (representing other constituentsincluding the extracellular substance). This mathematical model involves manyconstitutive parameters which must be identified using experimental results of amacroscopic specimen of the healthy artery. The proportional representation ofthe basic components in terms of volume fractions (also the elastin length density,the diameter of the aorta and the thickness of the wall) were determinedusing both microscopic and macroscopic morphometry of the tissue samples.In order to find the constitutive parameters, quasi-static uniaxial traction testsof samples from porcine aorta were performed. Methods based on optimizationare adopted to the material identification. Finally, we demonstrate the resultsof our numerical tests.