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Blood flow in an artery is a fluid-structure interaction problem. It is widely accepted that aneurysm formation, enlargement and failure are associated with wall shear stress (WSS) which is exerted by flowing blood on the aneurysmal wall. To date, the combined effect of aneurysm size and wall elasticity on intra-aneurysm (IA) flow characteristics, particularly in the case of side-wall aneurysms, is poorly understood. Here we propose a model of threedimensional viscous flow in a compliant artery containing an aneurysm by employing the immersed boundary-lattice Boltzmann-finite element method. This model allows to adequately account for the elastic deformation of both the blood vessel and aneurysm walls. Using this model, we perform a detailed investigation of the flow through aneurysm under different conditions with a focus on the parameters which may influence the wall shear stress. Most importantly, it is shown in this work that the use of flow velocity as a proxy for wall shear stress is well justified only in those sections of the vessel which are close to the ideal cylindrical geometry. Within the aneurysm domain, however, the correlation between wall shear stress and flow velocity is largely lost due to the complexity of the geometry and the resulting flow pattern. Moreover, the correlations weaken further with the phase shift between flow velocity and transmural pressure. These findings have important implications for medical applications since wall shear stress is believed to play a crucial role in aneurysm rupture.

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Tissue degradation plays a crucial role in vascular diseases such as atherosclerosis and aneurysms. Computational modeling of vascular hemodynamics incorporating both arterial wall mechanics and tissue degradation has been a challenging task. In this study, we propose a novel finite element method-based approach to model the microscopic degradation of arterial walls and its interaction with blood flow. The model is applied to study the combined effects of pulsatile flow and tissue degradation on the deformation and intra-aneurysm hemodynamics. Our computational analysis reveals that tissue degradation leads to a weakening of the aneurysmal wall, which manifests itself in a larger deformation and a smaller von Mises stress. Moreover, simulation results for different heart rates, blood pressures and aneurysm geometries indicate consistently that, upon tissue degradation, wall shear stress increases near the flow-impingement region and decreases away from it. These findings are discussed in the context of recent reports regarding the role of both high and low wall shear stress for the progression and rupture of aneurysms.

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The phase shift between pressure and wall shear stress (WSS) has been associated with vascular diseases such as atherosclerosis and aneurysms. The present study aims to understand the effects of geometry and flow properties on the phase shift under the stiff wall assumption, using an immersed-boundary-lattice-Boltzmann method. For pulsatile flow in a straight pipe, the phase shift is known to increase with the Womersley number, but is independent of the flow speed (or the Reynolds number). For a complex geometry, such as a curved pipe, however, we find that the phase shift develops a strong dependence on the geometry and Reynolds number. We observed that the phase shift at the inner bend of the curved vessel and in the aneurysm dome is larger than that in a straight pipe. Moreover, the geometry affects the connection between the phase shift and other WSS-related metrics, such as time-averaged WSS (TAWSS). For straight and curved blood vessels, the phase shift behaves qualitatively similarly to and can thus be represented by the TAWSS, which is a widely used hemodynamic index. However, these observables significantly differ in other geometries, such as in aneurysms. In such cases, one needs to consider the phase shift as an independent quantity that may carry additional valuable information compared to well-established metrics.

Blood flow in an artery is a fluid-structure interaction problem. It is widely accepted that aneurysm formation, enlargement and failure are associated with wall shear stress (WSS) which is exerted by flowing blood on the aneurysmal wall. To date, most of the computational studies of this problem assume rigid walls. In particular, in the case of side-wall aneurysms, the combined effect of aneurysm size and wall elasticity on intra-aneurysm (IA) flow characteristics is poorly understood. Here we propose a model of three-dimensional viscous flow in a compliant artery containing an aneurysm by employing the immersed boundarylattice Boltzmann-finite element method. This model allows to adequately account for the elastic deformation of both the blood vessel and aneurysm walls. Using this model, we perform a detailed investigation of the flow through aneurysm under different conditions with a focus on the parameters which may influence the wall shear stress. Most importantly, it is shown in this work that the use of flow velocity as a proxy for wall shear stress is well justified only in those sections of the vessel which are close to the ideal cylindrical geometry. Within the aneurysm domain, however, the correlation between wall shear stress and flow velocity is largely lost due to the complexity of the geometry and the resulting flow pattern. Moreover, the correlations weaken further with the phase shift between flow velocity and transmural pressure. These findings have important implications for medical applications since wall shear stress is believed to play a crucial role in aneurysm rupture.

This paper presents an analytical, numerical, and experimental study on the failure behavior of single hat-shaped T-joints made of plain woven carbon fiber polymer (T300/epoxy 618) and subjected to out-of-plane bending. The T-joint is manufactured by vacuum bag molding process at room temperature. An analytical model is developed to analyze the experimental results and to establish the associated failure criteria. Two failure modes: (a) laminate buckling and (b) laminate crushing are considered, and the theoretical relationships for predicting the failure load associated with each of the two modes were developed. The experimental data correlate closely with the analytically predicted behavior, including failure mode and bending stiffness. In particular, both laminate buckling and laminate crushing are observed during the experiment with laminate crushing being the final failure mode, which can be considered to be the most important failure mode of the fabricated T-joint. In addition, numerical simulations based on the finite element method and the Hashin damage criteria also accurately predict the flexural modulus, the peak load, and failure locations of the Tjoint obtained in the test.