The Reaction of the Head and Neck to Blast Waves: Comparison to Blunt Impact

Due to the relatively large number of exposures to IED blasts in Iraq and Afghanistan, the mechanical effects of blast waves impinging on the head have become an area of high interest. The ways in which the physical aspects of blast loading can cause injury are controversial in some respects but a general consensus is forming that much of the knowledge from closed head injury due to blunt trauma can be applied to injury mechanisms in blast loading [2]. In particular, sudden head rotations are known to be significant, as these are connected to high strains in brain tissue, in much the same way that rotations applied to a jar full of gelatin can induce deformations in the gelatin. High strains induced by sudden rotations of the head are known to be significant in developing injuries to the white matter of the brain [3, 4]. This study used a coupled fluid-structure finite element model to assess the effects of blast over pressure on translation and rotation of the head due to blast wave exposure. A finite element model of a 5^th percentile Hybrid-III dummy was used which was supplied by Livermore Scientific Technlogy Corp. (LSTC) as part of a license for LS-Dyna. The ALE formulation for fluid-structure coupling was used [1]. The sudden increase in head velocity is significant, but the sudden increases in rotation rates are small compared to those for some impacts. The increases in velocity and rotation rate due to the passage of the blast wave on the head of the dummy occur over a few milliseconds, and rotation becomes significant only after the neck loads become active, 15 to 20 milliseconds after blast wave impingement. These results indicate that efforts to modify the rotational velocity of the head in the reaction to a blast wave should act within 15 to 20 milliseconds of the blast.