Direct comparison of the primary blast response of a physical head model with post-mortem human subjects

As the gathering of information on the prevalence of blast-induced traumatic brain injuries (bTBI) continues, there is a need for the development and validation of a physical model (headform) reproducing the mechanical response of the human head to the direct loading from a blast wave. The chain of events leading to an injuries following direct exposure to a blast wave is very complex and its full determination is still the topic of several research efforts. The first step in the injury cascade is necessarily the mechanical insult of the blast wave to the human head. With a combination of representative anatomical features, adequate material selection and careful instrumentation, a validated physical model could measure real external pressure field history and predict resulting intra-cranial pressures (ICP) for any blast loading scenario. In addition, a physical model has the unique ability to measure quantitatively the effect of protective headwear. The following article discusses the validation of the BIPED (Blast-Induced Brain Injury Protection Evaluation Device) response against postmortem human subjects (PMHS). Previously reported PMHS blast wave generator tests were methodically replicated in the same facility using the BIPED. Loading conditions, instrumentation type and position as well as the head mounting technique were reproduced to ensure that the only difference between the two series of experiments was the model itself. A direct comparison of measured ICP histories is presented for two loading orientations and three loading magnitudes. It is demonstrated that the physical model response is in good agreement with that of the PMHS response. From signal analysis, additional evidences supporting skull deformation as the main contributor to ICP variations are discussed. Finally, external pressure fields from the blast wave generator experiments are compared to full scale free-field tests.