Abstract Text: There is a need to develop verifiable and validated computational modeling tools to investigate the human response to blast impact. This is especially needed, in investigating occupational training environments where military personnel are repeatedly exposed to low-level blast impact. These blast (shock wave) exposures and their cumulative effects have raised military concerns in terms of overall brain health, particularly as it relates to sub-concussions, mild traumatic brain injury and the subsequent cascading effects. As a first step, the current research is building numerical simulation capabilities to investigate the response behavior of a surrogate brain to shock waves. To that extent, we have validated a finite element model of a human head form filled with bio-fidelic gel representative of brain tissue placed in a Eulerian air domain and subjected to simulated blast waves. The model was validated against laboratory scale experiments using small RDX explosives charges [1]. We are building on our validated model to include more representative brain geometries including CSF, brain stem, gray and white matter. We are describing the material response behavior by employing appropriate equations of state and nonlinear constitutive models that fully characterize the volumetric and deviatoric response behavior under blast loading conditions just below the Bowen curve but above the limit for eardrum rupture [2]. The blast exposure to the head is performed for the anterior, and posterior orientations to capture the appropriate response of blast exposure from the directions in the training environment. The simulated results revealed the complexities of the wave interaction from the air to the skull to the surrogate brain. The early-time wave mechanics showed interacting compressive, tensile, and shear waves experienced in the brain. In particular, contours of intracranial pressure showed elevated compressive waves near the site of impact for the anterior and posterior orientations. The corresponding tensile loadings were also similarly elevated in the contrecoup locations. The deviatoric (shear) stress mapping showed elevated stress distributions along the interface between the brain stem region and the base of the skull. The preliminary results show the potential for shearing/tearing of brain tissue material from blast loading with correlation to specific wave physics variables. Further results from this effort will be shared at the upcoming NCA TBI Research Symposium meeting.
