Development and Validation of a 3D Finite Element Model of Advanced Combat Helmet and Biomechanical Analysis of Human Head and Helmet Response to Primary Blast Insult

Blast-induced traumatic brain injury (bTBI) has emerged as a “signature injury” in combat casualty care. Present combat helmets are designed primarily to protect against ballistic and blunt impacts, but the current issue with helmets is protection concerning blasts. In order to delineate the blast wave attenuating capability of the Advanced Combat Helmet (ACH), a finite-element study was undertaken to evaluate the head response against blast loadings with and without helmet using validated finite element (FE) models of the human head and detailed ACH developed for this study. Four levels of overpressures (0.27-0.66 MPa) from the Bowen’s lung iso damage threshold curves were used to simulate blast insults. Effectiveness of the helmet with respect to head orientation was also investigated. The resulting biomechanical responses of the brain to blast threats were monitored and compared for human head with and without the helmet.

For all Bowen’s cases, the peak intracranial pressures in the head ranged from 0.68-1.8 MPa in the coup cortical region. ACH was found to mitigate intracranial pressures (0.62-1.1 MPa) in the head by 10-35%. Helmeted head resulted in 30% lower average peak brain strains and product of strain and strain rate. Among three blasts loading directions with ACH, highest reduction in peak intracranial pressure (44%) was due to backward blasts whereas the lowest reduction in peak intracranial pressures and brain strains was due to forward blast (27%).

The biomechanical responses of a human head to primary blast insult exhibited directional sensitivity owing to the different geometry contours and coverage of the helmet construction and asymmetric anatomy of the human head. Thus, directionspecific tolerances are needed in helmet design in order to offer omni-directional protection for the human head.

A numerical study was also conducted to evaluate the effects of blast overpressure on the brain of a human head model and a physical blast anatomical headform model constructed with simulant materials representing skull and brain of a human head. Biomechanical parameters within the intracranial cavity were monitored and compared between the two models. Results suggested that influence of mechanical properties of the head can affect shock propagation through the brain.

Keywords: Traumatic Brain Injury; Primary Blast; Finite Element Model; Advanced Combat Helmet Model; Human Head Model; Intracranial Pressure; Brain Strain and Strain Rate; Head Protection; Headform

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Year

Entry

2002

Brands DWA, Bovendeerd PHM, Wismans JSHM. On the potential importance of non-linear viscoelastic material modelling for numerical prediction of brain tissue response: test and application. Stapp Car Crash J. 2002;46:103-121. SAE 2002-22-0006.

2005

McCracken PJ, Manduca A, Felmlee J, Ehman RL. Mechanical transient‐based magnetic resonance elastography. Mag Reson Med. March 2005;53(3):628-639.

2000

Brands DWA, Bovendeerd PHM, Peter GWM, Wismans JSHM. The large shear strain dynamic behavior of in-vitro porcine brain tissue and a silicone gel model material. Stapp Car Crash J. 2000;44:249-260. SAE 2000-01-SC17.

2011

Sharma S, Zhang L. Prediction of intracranial responses from blast induced neurotrauma using a validated finite element model of human head. In: Proceedings of the 7th Ohio State University Injury Biomechanics Symposium. May 22-24, 2011; Columbus, OH.

1965

Patrick LM, Lissner HR, Gurdjian ES. Survival by design: head protection. In: Severy DM, ed. Proceedings of the 7th Stapp Car Crash and Field Demonstration Conference. 1963; University of California at Los Angeles. Springfield, IL: Charles C. Thomas; 1965:483-499.