Tensile tests on Polydimethylsiloxane (PDMS) materials were conducted to illustrate the effects of mixing ratio, definition of the stress-strain curve, and the strain rate on the elastic modulus and stress-strain curve. PDMS specimens were prepared according to the ASTM standards for elastic materials. Our results indicate that the physiological elastic modulus depends strongly on the definition of the stress-strain curve, mixing ratio, and the strain rate. For various mixing ratios and strain rates, true stress-strain definition results in higher stress and elastic modulus compared with engineering stress-strain and true stress-engineering strain definitions. The elastic modulus increases as the mixing ratio increases up-to 9:1 ratio after which the elastic modulus begins to decrease even as the mixing ratio continues to increase. The results presented in this study will be helpful to assist the design of in vitro experiments to mimic blood flow in arteries and to understand the complex interaction between blood flow and the walls of arteries using PDMS elastomer.

In this model of chronic type B aortic dissection, diastolic false lumen pressure was the highest in the setting of smaller proximal tear size and the lack of a distal tear. These determinants of inflow and outflow may impact false lumen expansion and rupture during the follow-up period.

This study demonstrates the anisotropy of the aortic wall in ATAA and provides data on the mechanical behaviour in the physiological range of pressure.

This study provides new data on the elastic modulus in the physiologic and hypertensive range that can be used in computational analysis and the design of bench-top models. The accuracy of computational analysis and bench-top models strongly depends on the knowledge of the elastic properties of the aortic wall. The mechanical properties presented in this study, with specific values for 2 locations (greater and lesser curvature) and 2 directions (circumferential, longitudinal), will increase our understanding of the mechanisms that precede rupture of an ascending aortic aneurysm.

It is important to consider which stress-strain definition is employed when analysing soft tissues. Although the true stress-true strain definition exhibits a non-linear relation, we favour it in tissue mechanics because it gives more accurate measurements of the material's response using the instantaneous values.

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Objective: The aim of this investigation was to validate our numerical model of type B aortic dissection with our experimental results from a bench-top-model. Methods:Various numerical meshes were constructed using a finite-volume based computational fluid dynamics (CFD) solver (ANSYS Fluent 15) to simulate pulsatile flow and pressure in dissected aorta models. The κ-ω Shear Stress Transport (SST) turbulence model was imbedded. All simulations were carried out for four cardiac cycles to achieve a periodic solution, and the results obtained in the fourth cycle were used in the validation. Results:We validated the numerical results, for several tear size and location, with our experimental data. CFD results of type B aortic dissection with various tear size and location were strongly correlated with the in vitro results.Conclusions: CFD tools have a potential role in evaluating different scenarios and aortic dissection configurations.

The elastic modulus of a pulsatile aortic model may be measured by electrocardiographically-gated multi-detector CTA protocol. This preliminary study suggests the possibility of determining non-invasively the elastic properties of a living, functioning aorta using CTA data.