Session: 07-01-01: Injury Risk Assessment due to Blunt Impact

Paper Number: 173285

Biomechanical Analysis of Surrogate Headforms Equipped With Ballistic Helmets Under High Velocity Bullet Impact 

High velocity bullet impact (bullet velocity: 700 ± 15 m/s) pose a critical threat to head and neck safety in modern combat scenarios, often resulting in severe traumatic injuries. Despite this fact, ballistic helmets designed explicitly to counter such a threat are either unavailable, or their effectiveness has not been evaluated. In this work, we have investigated the ballistic performance of two newly developed ballistic helmet configurations under high velocity bullet impact: (a) Patka helmet, constructed from hardened steel, and (b) advanced helmets incorporating a ceramic-polymer sandwich plate integrated onto a Kevlar and UHMWPE shell.

To evaluate the protective performance of aforementioned ballistic helmets, the helmets were mounted on three different instrumented surrogate headforms, where each headform was selected for its capability to capture distinct biomechanical parameters. The following headforms were considered: Flexible headform with cruciform cavity, Hybrid-III, and GHBMC head model based headform. All these headforms were coupled with the Hybrid III neck. Various biomechanical parameters, such as back face deformation (BFD), head kinematics (linear acceleration, angular velocity, angular acceleration), neck loads (neck force, neck moment), and brain simulant pressures (coup and contrecoup), were experimentally measured.

Experimental results revealed that the all the ballistic helmets were capable in stopping the bullet. We obtained minimal BFD (<1 mm) using Patka helmet, however, despite low BFD, the biomechanical parameters such as angular acceleration (~5800 rad/s²), and neck force (~250 N) exceeded the injury thresholds associated with a 50% risk of mild traumatic brain injury (mild TBI). Also, they exhibited significant bullet fragmentation upon impact. The shattered fragments traveling at considerable velocities, pose an additional safety concern due to their potential to generate secondary injuries.

The advanced helmets showed BFD values between 7-9 mm. These BFD values were within the acceptable thresholds specified by current ballistic standards. However, the biomechanical parameters such as angular acceleration (~6500 rad/s²), and neck force (~2000 N), and coup pressure (~300 kPa) were much higher than the injury threshold corresponding to mild TBI and it may pose serious to severe injury to the head and neck.

Overall, these findings highlight a crucial limitation in current ballistic helmet evaluation protocols that BFD alone does not reliably indicate injury risk. A comprehensive assessment must incorporate multiple biomechanical metrics to fully characterize helmet performance under high velocity bullet impact, with implications in the design and evaluation of futuristic ballistic helmets.

Keywords: high velocity bullet impact, ballistic helmet, biomechanical parameters, headforms

Presenting Author: Shailesh Ganpule IIT Roorkee

Presenting Author Biography: Prof. Ganpule is an associate professor at IIT Roorkee India. His research interests are in injury biomechanics and injury mitigation under extreme loading environments. He is actively working in head injury biomechanics.

Authors:

Atul Harmukh IIT Roorkee
Praveen Kumar IIT Roorkee
Shailesh Ganpule IIT Roorkee