Finite Element Modeling of Blast-Induced Traumatic Brain Injury

Human exposure to a blast wave itself without any fragment impact can still result in primary blast-induced traumatic brain injury (bTBI). To investigate the mechanical response of human brain to primary blast waves and to identify the injury mechanisms of bTBI, a three-dimensional finite element head model consisting of the scalp, skull, cerebrospinal fluid, nasal cavity, and brain was developed from the imaging data set of a human head. The finite element head model was implemented with material models and was partially validated against a published cadaveric experiment. This study included three scenarios of blast-head interaction simulations using the same five TNT doses: the simulations of head exposures to the blast waves coming from three horizontal orientations (anterior, right lateral, posterior), to the blast waves generated from the explosives laid on the ground, and to the blast waves within a small room. For the horizontal blast-head simulations, the influences of the blast levels and exposure orientations on the pressure and shear stress responses of brain were analyzed. For the simulation scenarios of the ground blasts and the room blasts, the influences of the blast levels and the blast wave reflections on the pressure and shear stress responses of brain were assessed. The patterns of intracranial pressure waves and the high-pressure locations were investigated. Based on a published pressure-based injury criterion of cerebral contusion, the locations and injury severities of cerebral contusion for every simulation scenario were predicted. High von-Mises stresses were found on the cortex, brainstem, and spinal cord in every simulation. However, it was predicted that diffuse axonal injury (DAI) did not occur in any simulation using a DAI criterion based on von-Mises stress. The mechanical properties of human bridging vein in an anisotropic, hyperelastic constitutive model were obtained by fitting the data of an inflation test of a real human bridging vein to the analytical equation of the inflation test. The obtained mechanical properties were implemented in the finite element analysis of bridging vein rupture to predict the blast-induced subdural hemorrhage by using the peak CSF pressures at the SSS of the anterior blast-head simulations as the loading conditions