The deformation associated with a ballistic shield defeating a projectile can interact with the user’s upper extremity, resulting in the release of the shield, placing those behind the device at risk. This injury mechanism is known as behind-shield blunt trauma (BSBT). Previous studies investigating these interactions have used testing conditions not representative of those present during these behind-shield events and lacked sufficient testing to determine statistically relevant outcomes. In the present work, the loading present during ballistic shield deformation was characterized through testing using an Anthropomorphic Test Device (ATD) upper extremity placed behind a level III ballistic shield. Digital image correlation (DIC) and post-impacting X-ray imaging were used to assess the ballistic shield’s deformation. The data collected from ballistic testing informed the development of a projectile used with a pneumatic impactor for the application of BSBT in a lab-based setting. Using the projectile, ballistic impacts were replicated on the ATD upper extremity and translated to 5th and 95th percentile cadaveric arms. Load data were collected for the hand and forearm using piezoelectric force sensors embedded in the projectile. Similarly, PMHS were impacted in a stepwise fashion of increasing energy until fractures were identified using X-ray imaging. A novel scaling technique was developed where Partial Least Squares (PLS) was used to determine critical variables relating donor anthropometrics to peak impact force. The scaling equations generated using this technique offer future researchers the opportunity to employ a larger range of specimens when determining injury thresholds for the hand and forearm. Through the characterization of the conditions present during BSBT, the injury thresholds to these mechanisms were assessed for understudied populations. Additionally, this work presents scaling techniques that could reduce the number of specimens required to determine future upper extremity injury limits. The information presented within this work provides an important step in developing new standards for ballistic shields to better protect users from BSBT. / Thesis / Master of Applied Science (MASc) / The deformation of a ballistic shield associated with stopping a bullet can interact with the user’s arm, causing them to drop the shield and placing the user in further danger. This work aimed to assess the risks to the hand and forearm over a range of male sizes using mechanical and biomedical tools. Ballistic loading was characterized using a crash test dummy arm to understand the conditions present during the event. The injuries associated with this loading were assessed using cadaveric specimens and a custom projectile for replicating the impacts. Mathematical techniques were used to translate the injury thresholds to the exact user sizes – providing relevant metrics for future ballistic shield standards. The results of this work present methods for recreating ballistic testing in a lab-based setting and for scaling forces associated with the hand and forearm, allowing future researchers to use a broader range of specimens for injury assessment.

Ballistic shields are used by defense teams in dangerous situations as protection against threats such as gunfire. When a ballistic shield is struck, the shield material will deform to absorb the kinetic energy of the incoming projectile. The rapid back-face deformation of the shield can contact the arm, which can impart a large force over an extremely short duration. This work modified an Anthropomorphic Test Device (ATD) to be used for the characterization of behind ballistic shield blunt impact loading profiles. The modified ATD was instrumented to measure impacts at the hand, wrist, forearm, and elbow to compare the force transfer at different locations of impact. A custom jig was designed to support the ATD behind a ballistic shield, provide a high degree of adjustability, and be subjected to impact testing. Two ballistic shield models, both with the same protection rating, were tested and showed to have statistically different responses to the same impact conditions, indicating further need for shield safety evaluation. To apply these loading profiles to future injury criteria development tests, a pneumatic impacting apparatus was re-designed that will allow the high energy impact profiles to be re-created in the McMaster Injury Biomechanics lab. Understanding the ballistic impact conditions, as well as the response of different ballistic shield models provided insight into the possible methods available to reduce upper extremity injury risk. This work has provided essential data for informing a future standard for shield safety evaluation. / Thesis / Master of Applied Science (MASc) / When a ballistic shield is impacted by a bullet it deforms to absorb the incoming energy. The high-speed deformation of the shield material can impact the arm leading to fracture and possible life-threatening risks if the shield is dropped due to this injury. At the time of this work, there were no standards that limited the amount of allowable back-face deflection or tools available that could measure the force transferred to the arm in this scenario. The purpose of this work was to develop a measurement device that could measure the force transferred to the arm from the behind shield impact. An existing crash test dummy arm was modified to provide measurement capabilities for this loading scenario. Ballistic shield testing was conducted where two different ballistic shield models were impacted to observe how the impact force changed with shield design, as well as the distance the device was placed behind the shield. A pneumatic impacting apparatus was then re-designed in the McMaster Injury Biomechanics lab that will allow the ballistic impact conditions to be re-created for evaluating the injury tolerance of the arm. The results of this work will be used to inform the future development of a ballistic shield evaluation standard.