Traumatic brain injuries have become the signature injury resulting from the military conflicts in Iraq and Afghanistan. In particular, there is an urgent need to unravel the mechanisms leading to mild traumatic brain injury experienced by the warfighter resulting from blast impact. To that end the current research is investigating the internal pressure loading as well as the shear stress distribution on a surrogate head model impacted by blast waves from an RDX explosive. To carry out our investigation, both numerical simulations and blast experiments were performed on a surrogate head form filled with bio-fidelic gel representative of brain tissue. A finite element model of the surrogate head was developed to provide numerical insights of the pressure wave evolution from the explosive blast to the skull and through the head model. The results from the simulations were validated against history data from the blast experiments where the head form was outfitted with pressure sensors embedded at 5 mm depth into the side, back, front and at the Kocher points of the head form.
The comparison of the simulated results with experiments revealed high compressive blast impact loading to the front of the skull on the order of 300 kPa for a standoff distance of 180 mm. The recorded pressure waves that were transmitted to the anterior region of the surrogate brain produced compressive pressure waves of magnitude 95 kPa and tensile waves of 37 kPa. Similar results were also obtained from numerical simulation on the order of 90kPa compressive loading and 43 kPa tensile loading over a period of 0.55 msec. Further wave propagation into the bio-gel brain simulant revealed a drop in the recorded compressive pressure down to 80 kPa followed by tensile pressure loading of 40 kPa. The combination of the compressive and tensile loading in the bio-gel are strong indicators of tearing and shearing type response in the brain due to blast.