Evaluation of brain tissue responses because of the underwash overpressure of helmet and faceshield under blast loading

Abstract

Head protective tools such as helmets and faceshields can induce a localized high pressure region on the skull because of the underwash of the blast waves. Whether this underwash overpressure can affect the brain tissue response is still unknown. Accordingly, a computational approach was taken to confirm the incidence of underwash with regards to blast direction, as well as examine the influence of this effect on the mechanical responses of the brain. The variation of intracranial pressure (ICP) as one of the major injury predictors, as well as the maximum shear stress were mainly addressed in this study. Using a nonlinear finite element (FE) approach, generation and interaction of blast waves with the unprotected, helmeted, and fully protected (helmet and faceshield protected) FE head models were modeled using a multi-material arbitrary Lagrangian-Eulerian (ALE) method and a fluid-structure interaction (FSI) coupling algorithm. The underwash incidence overpressure was found to greatly change with the blast direction. Moreover, while underwash induced ICP (U-ICP) did not exceed the peak ICP of the unprotected head, it was comparable and even more than the peak ICP imposed on the protected heads by the primary shockwaves (Coup-ICP). It was concluded that while both helmet and faceshield protected the head against blast waves, the underwash overpressure affected the brain tissue response and altered the dynamic load experienced by the brain as it led to increased ICP levels at the countercoup site, imparted elevated skull flexure, and induced high negative pressure regions. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

CFD modeling of the underwash effect of military helmets as a possible mechanism for blast-induced traumatic brain injury

“…They also showed that the underwash overpressure occurred at the opposite side of the incoming waves in front and back directions. Moreover, in another study on the effects of underwash on the brain tissue response, they studied the same blast directions used here using a FEA approach and found similar results in terms of the location and intensity of the underwash overpressure (Sarvghad-Moghaddam et al 2016). The dependence of the underwash on the direction of the blast was also among their results.…”

“…This phenomenon may also affect the performance of these tools under blast compared to their high efficiency under impact (SarvghadMoghaddam et al 2015). Sarvghad-Moghaddam et al (2016) showed that underwash-induced overpressure on the head has the potential of imposing higher risk of brain injury. While parameters such as the blast intensity and direction, as well as the shockwave flow mechanics can affect underwash, the underlying cause for underwash is still a question.…”

“…In terms of assessing the brain injury risk in different blast theatres, many researchers have investigated the mechanical response of the human head and brain to dynamic loads such as blast (Moore et al 2009;Chafi et al 2010;Grujicic et al 2010;Nyein et al 2010;Grujicic et al 2011;SarvghadMoghaddam, Jazi, et al 2014). Sarvghad-Moghaddam et al (2016) performed a comprehensive FEA study on the development and effects of underwash on the dynamics response of the brain. They reported that based on different blast parameters such direction, the underwash-induced overpressure on the head can exceed the one imposed by the primary shockwaves.…”

Brain Tissue Constitutive Material Models and the Finite Element Analysis of Blast-Induced Traumatic Brain Injury

“…Experimental methods impose moral and technical issues before conducting any research. Many FE studies have been conducted to determine brain responses under dynamic loads to study TBIs [1][2][3][4][5][6][7][8][9][10]. Such studies have helped to e ciently develop TBI prediction tools based 1 on the current injury threshold criteria of kinematics, intracranial pressure (ICP), tissue strain, and tissue shear stress [11].…”

“…Such studies have helped to e ciently develop TBI prediction tools based 1 on the current injury threshold criteria of kinematics, intracranial pressure (ICP), tissue strain, and tissue shear stress [11]. Mechanical responses of human head brain and skull have been studied using multi-material FE simulations [5,12]. Representative FE head models, which include major components of the head such as brain, skull bones, and cerebrospinal uid (CSF), have been employed to study the response of the head under di erent loadings.…”