Hyper-Viscoelastic Behavior of Healthy Abdominal Aorta

The aim of the present study was to define biomechanical parameters of the healthy human abdominal aorta, usable to develop materials for the aortic phantom production. Such phantoms used in the training of endovascular treatment must describe the same morphology and mechanical behavior properties as the patient's aorta. To accurately identify these biomechanical parameters, ex vivo experiments in uniaxial tensile and dynamic simple shear tests were performed on six human healthy abdominal aortas (6 males, between 12 and 69 years old). A solid generalized Maxwell model including Yeoh expression for the elastic part was used to describe the hyper-viscoelastic behavior of the aorta. The results obtained from uniaxial tensile tests show an exponential-like increase in stiffness, which can be described by three hyperelastic parameters (C-1, C-2 and C-3). From dynamic shear experiments, the viscous part of the global biomechanical behavior was expressed in a specific angular-frequency range (1 to 315 rad/s). Three Maxwell elements (beta(1), beta(2), and beta(3)) put on three constant times (tau(1) = 0.003 s, tau(2) = 0.03 s, and tau(3) = 0.3 s) respectively, were necessary to describe it. As this relatively high number of viscoelastic parameters may be difficult to control in the development of materials, we suggest defining the viscous behavior with the global viscosity eta(0) that combines the viscoelastic contributions of each Maxwell element. In conclusion, four biomechanical parameters: C-1, C-2, C-3 and eta(0), must be considered for the development of materials used in the aortic phantom production. (C) 2016 AGBM. Published by Elsevier Masson SAS. All rights reserved.