Biphasic poroviscoelastic simulation of brain injury under high-speed impact

Traumatic brain injury (TBI) occurs very frequently in modern societies. It is highly fatal and usually has serious cognitive, physical and emotional consequences for survivors. The effective prevention, diagnosis, and treatment of TBI demand precise understanding of the underlying injury mechanisms.; Brain tissue is a soft, gel-like, adhesive material. Mathematically, it can be described as a continuum mixture of an incompressible viscoelastic solid matrix and an incompressible inviscid fluid phase. The mechanical behavior of brain tissue is thus determined by both fluid flow-dependent and fluid flow-independent viscoelasticity. The biphasic poroviscoelastic (BPVE) model, accounting for both of these viscoelastic mechanisms, was adopted in the current dissertation to study the dynamic response of brain tissue under high-speed impact.; Based on the linear BPVE model, a mixed finite element formulation was developed via Galerkin weighted residual method. The numerically stable Q2-P1 element, which applies a biquadratic and a linear interpolation function to the displacement and pressure variables respectively, was adopted. The time integration of dynamic problems was implemented using Newmark's method. The resulting governing equations were then solved using a segregated solution scheme.; The current dynamic finite element formulation was validated against the closed-form analytical solutions of one-dimensional free-vibration problems. Numerical simulations were conducted on a model based on the simplified para-sagittal brain section. The effects of boundary conditions, hydraulic permeability, and reduced relaxation function were investigated under various loading conditions.