Mechanisms of Blast-induced Mtbi

Blast-induced traumatic brain injury (TBI) has become a major issue as a consequence of deployment of military personnel under the Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF) in Iraq and Afghanistan, respectively. Threats during missions of the (Dutch) troops in these recent operations are not comparable with threats experienced formerly. They now have to deal with Improvised Explosive Devices (IEDs), e.g. road side bombs and suicide attacks. Especially long term consequences for personnel being exposed to less severe, non life threatening blast loads are diagnosed frequently in military hospitals. Research on blast induced mild Traumatic Brain Injury (mTBI) is mainly related to the clinical diagnosis and therapy. Diagnostic tools and therapy monitoring are the main focus in these mTBI research programs. Victims suffer from cognitive deficiencies. Blast experiments with laboratory rats revealed changes in behavior in combination with axonal injuries. However, the physics of the injury mechanisms are not well understood. Actually, the physics of transfer of external blast through the skull into the brain is not known in such detail to develop injury criteria which allow for quantification of the risk on brain injury. TNO aims at developing knowledge to assess the mitigation of the blast load to the brain by a variety of protective measures, e.g. helmets or operational instructions on location. The mechanisms of shock wave propagation in air and human head have been investigated by conducting accurate measurements and computer simulations. Recently used numerical models, composed of uncoupled Computational Fluid Dynamic (CFD) and Finite Element (FE) models gave limitations in reliability and adaptation. Proposed is a model that consists of a Multi-Material Arbitrary Lagrangian Eulerian (MMALE) model for the air blast and a Lagrangian model for the simplified head structure, coupled by a penalty function. In this final MSc project, focus will be on numerical modeling of exposure to blast of a skull/brain structure in a shock tube environment. In the literature survey presented here, recent findings in experimental studies on both animal and (simplified) human head surrogate models, as well as findings from numerical studies will be reviewed. This survey gives an overview of stateof-the-art knowledge about injury mechanisms for blast-induced traumatic brain injury, and furthermore, it will state the missing aspects that will be addressed in the numerical study.