Fluid/Structure Interaction Computational Investigation of Blast-Wave Mitigation Efficacy of the Advanced Combat Helmet

Abstract

To combat the problem of traumatic brain injury (TBI), a signature injury of the current military conflicts, there is an urgent need to design head protection systems with superior blast/ballistic impact mitigation capabilities. Toward that end, the blast impact mitigation performance of an advanced combat helmet (ACH) head protection system equipped with polyurea suspension pads and subjected to two different blast peak pressure loadings has been investigated computationally. A fairly detailed (Lagrangian) finite-element model of a helmet/skull/brain assembly is first constructed and placed into an Eulerian air domain through which a single planar blast wave propagates. A combined Eulerian/Lagrangian transient nonlinear dynamics computational fluid/solid interaction analysis is next conducted in order to assess the extent of reduction in intra-cranial shock-wave ingress (responsible for TBI). This was done by comparing temporal evolutions of intra-cranial normal and shear stresses for the cases of an unprotected head and the helmetprotected head and by correlating these quantities with the three most common types of mild traumatic brain injury (mTBI), i.e., axonal damage, contusion, and subdural hemorrhage. The results obtained show that the ACH provides some level of protection against all investigated types of mTBI and that the level of protection increases somewhat with an increase in blast peak pressure. In order to rationalize the aforementioned findings, a shockwave propagation/reflection analysis is carried out for the unprotected head and helmet-protected head cases. The analysis qualitatively corroborated the results pertaining to the blastmitigation efficacy of an ACH, but also suggested that there are additional shockwave energy dissipation phenomena which play an important role in the mechanical response of the unprotected/protected head to blast impact.

Experimental Characterization and Material-Model Development for Microphase-Segregated Polyurea: An Overview

“…In other words, a vast body of experimental studies pertaining to the blast/ballistic-protection performance of various polyurea bearing protective structures was not the subject of the present investigation. An overview of the latter investigations can be found in our prior work (Ref [16][17][18][19][20][21].…”

Ballistic helmets – Their design, materials, and performance against traumatic brain injury

“…For both 5.2 atm and 18.6 atm blast intensities, no shear-induced mTBI was observed, while there was a possibility of contusion type TBI. For a head protected by a helmet, the findings obtained by Grujicic et al [62] were contradictory to those reported in Moore et al [93] and Nyein et al [104]. For the helmeted head, the load transfer path to the skull was found to be different.…”

“…In the absence of information about the currently used suspension pad material in the ACH, Ethylene-Vinyl-Acetate (EVA) was chosen as a second material (other than polyurea). The material models and the pressure intensities were taken to be the same as those used in their earlier study [62]. High peak axial stresses and peak particle velocities were chosen as parameters for comparison.…”

Modelling the Presence of Diffuse Axonal Injury in Primary Phase Blast-Induced Traumatic Brain Injury

“…The precise mechanisms by which bTBI occurs are still unknown. Grujicic et al [10] propose that rotational motion and acceleration/deceleration are not applicable in blast-induced trauma scenarios. Conversely, an investigation by Dagro et al [11] supports the notion that rotational loading is relevant to blast events.…”

“…Axonal damage, cerebral contusion and subdural haemorrhaging are the three most common forms of mild TBI (mTBI), or concussion as it is known in common language [10]. Of these three forms of mTBI, DAI is the most difficult to detect by conventional means such as computed tomography (CT) scan or magnetic resonance imaging (MRI).…”