Eslaminejad, Ashkan

Blast traumatic brain injury (bTBI) may happen due to sudden blast and high-frequency loads. Due to the moral issues and the burden of experimental approaches, using computational methods such as finite element analysis (FEA) can be effective. Several finite element studies have focused on the effects of TBI to anticipate and understand the brain dynamic response. One of the most important factors in every FEA study of bTBI is the accurate modeling of brain tissue material properties. The main goal of this study is a comparison of different brain tissue constitutive models to understand the dynamic response of brain under an identical blast load. The multi-material FE modeling of the human head has several limitations such as its complexity and consequently high computational costs. Therefore, a spherical head model is modeled which suggests more straightforward observation/understanding of the FE modeling of skull (solid), CSF (fluid), and the brain tissue. Three different material models are considered for the brain tissue, namely hyperelastic, viscoelastic, and hyperviscoelastic. Brain dynamic responses are studied in terms of the head kinematics (linear acceleration), intracranial pressure (ICP), shear stress, and maximum mechanical strain. Our results showed that the hyperelastic model predicts larger ICP and shear than other constitutive brain tissue models. However, all material models predicted similar shear strain and head accelerations.

Skull deformation and vibration has been hypothesized to be an injury mechanism when the human head undergoes an impact scenario. The extent that skull deformation may increase the risk of traumatic brain injury, however, is not well understood. This computational study explains whether skull deformation has any impact on the variation of intracranial pressure (ICP). To this end, a finite element head model including major anatomical components of the human head was employed. The head model has been validated against ICP variations on the brain. The impact simulations were carried out using a rigid cylindrical impactor. The scenarios were frontal impacts with the impactor hitting the forehead of the head model at two impact severity levels. In order to examine the effect of skull elasticity on the stress wave propagation inside the cranium under an external applied force, the skull was also taken as a rigid body with the same density as the elastic one, and the result were compared with those obtained with the deformable skull. For the two cases, the variation of ICPs at the coup and countercoup sites were recorded and compared. The results of the study showed that, for the case studies presented here, the deformation of skull didn’t increase the level of ICP inside the brain. It was concluded that the skull rapid body motion might be responsible for brain injuries.

Blast-induced traumatic brain injury (bTBI), is defined as a type of acquired brain injury that occurs upon the interaction of the human head with blast-generated high-pressure shockwaves. Lack of experimental studies due to moral issues, have motivated the researchers to employ computational methods to study the bTBI mechanisms. Accordingly, a nonlinear finite element (FE) analysis was employed to study the interaction of both unprotected and protected head models with explosion pressure waves. The head was exposed to the incoming shockwaves from front, back, and side directions. The main goal was to examine the effects of head protection tools and the direction of blast waves on the tissue and kinematical responses of the brain. Generation, propagation, and interactions of blast waves with the head were modeled using an arbitrary Lagrangian-Eulerian (ALE) method and a fluid-structure interaction (FSI) coupling algorithm. The FE simulations were performed using Ls-Dyna, a transient, nonlinear FE code. Side blast predicted the highest mechanical responses for the brain. Moreover, the protection assemblies showed to significantly alter the blast flow mechanics. Use of faceshield was also observed to be highly effective in the front blast due to hindering of shockwaves.