A Biomechanical Composite Model to Determine Effective Elastic Moduli of the CNS Gray Matter

Brain tissue is a heterogeneous material with complicated microstructural features. Models based on microstructure can lead to more accurate and physically realistic predictions of mechanical characteristics of brain tissue. A two-step Mori-Tanaka/Voigt homogenization procedure is implemented into a 3D microstructurally-based multi-phase composite model, composed of randomly-oriented elastic axons, dendrites and neuronal cell bodies surrounded by an elastic matrix. The effects of microstructure-related scale on the effective elastic moduli of the cerebral cortex are analyzed by comparing the predictions from classical and micropolar continuum theories. For the first time, composite material rules and micropolar continuum theory have been utilized to investigate brain biomechanics. These findings can assist future efforts to be directed towards relating the microstructural aspects of the brain tissue to its macroscopic behavior.