Design of a Composite Combat Helmet Liner for Prevention of Blast- Induced Traumatic Brain Injury

Air blast-induced traumatic brain injuries (TBIs) represent a significant percentage of military personnel injuries observed in Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF). Prevalence of blast-induced TBIs is attributed to several factors, including improved body armor, improved diagnostic techniques, greater awareness, and the increased threat of attack by improvised explosive devices (IEDs). Though the mechanisms of blast-induced TBIs are not fully understood, this is a serious problem that needs to be addressed. The overall goal of the work presented in this report is to explore a possible improvement to the Advanced Combat Helmet (ACH) liner increasing the protection against blast-induced TBIs. The essential new element is the inclusion of moveable or deformable materials sandwiched within foam to dissipate the blast energy, reduce the peak transmitted pressure, and stretch the blast waveform before it reaches the brain. Filler materials explored in this work include glass beads, aerogel, glycerin, and water. To contribute to this goal, the description and validation of a model of the dynamic response of a (modified) helmet and head surrogate to an air blast event is presented in this report. An initial prototype for a liner incorporating the filler material technology is designed and manufactured. The response characteristics of this prototype are then assessed experimentally by collecting pressure data during air blast loading provided by an explosive drive shock tube. Experimental work is carried out at Purdue University. A nonlinear finite element model is then developed using the commercial code ABAQUS® to describe the response observed experimentally. Consistency between results obtained numerically and results obtained experimentally indicates the model accurately describes the physics of a blast event impinging on a helmet and head. Several suggestions are then provided for how the model may be used to optimize the design of a helmet liner providing the maximum protection against airblasts. Thesis Supervisor: Laurence R. Young Apollo Program Professor of Astronautics Professor of Health Sciences and Technology