Degree

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

Document Type

Dissertation

Abstract

A true understanding of the mechanisms behind most of the brain diseases is still out of reach. For several years, the interest of scientists has been focused on the genetic and biological causes, however, recent studies unraveled the importance of the biomechanics of the brain growth, folding, impact resistance, and deformation on its pathological conditions. While, a wide range of different methods have been used for characterization of the mechanical properties of the brain at the tissue level, the obtained results from different studies are extremely scattered and sometimes in contrast to one another. Since the brain tissue is extremely soft, its mechanical properties are quite a challenge to be obtained. In this study, the accurate analysis of the mechanical heterogeneity of the brain tissue is performed through dynamic and pseudo-static indentation techniques to evaluate the viscoelastic response of the brain and presenting its anisotropy, inhomogeneity, and rate dependence. In addition, this research provides a detailed reference for modeling the nonlinear mechanical behavior of soft tissues, in general, and the brain tissue, in particular, with addressing important considerations for mechanical modeling in uniaxial loading conditions. With thoroughly presenting the physical basis of the modeling procedure, it is shown that if such considerations are neglected, a considerable inaccurate evaluation of the mechanical properties of the tissue can be expected, although the results might mathematically be correct. Moreover, a new model is developed for the mechanical behavior of the brain tissue that addresses the tension-compression asymmetry with taking into account the compressibility of the tissue in different loading conditions. This model is implemented by utilizing a combined analytical and numerical scheme. The results of this research could be used as input variables for computer simulations of the brain tissue in studying the traumatic brain injury, malformation of the brain folds, and other pathobiological conditions associated with the mechanical behavior of the brain.

Date

6-18-2018

Committee Chair

Voyiadjis, George

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