Ballistic shields are supported by a user’s arm, placing the upper extremity at close proximity to the back-face of the shield. Although ballistic shields must pass a protective standard that outlines projectile (bullet) penetration; there is no standard that stipulates the amount of acceptable deformation when ballistic shields stop or deflect projectiles. There are no injury criteria developed for the high-rate, short duration and focal loading that is typical of shield back-face deformation from these events. In this research, an anthropomorphic test device (ATD) was modified to allow for additional instrumentation capable of measuring these loads. It was then used in a ballistic testing facility to quantify loading at the hand, wrist, forearm, and elbow. A lightweight projectile was created that matched the shape and stiffness of the deforming ballistic shield and impacts within 5% of the peak force measured in the ballistic testing facility were applied with it to post-mortem human subjects (PMHS) until failure. Eight 50th percentile male PMHS pairs were segmented at the mid-humerus and impacted to failure to determine the fracture threshold of the hand, wrist, forearm, and elbow, confirmed by x-ray imaging. The peak force required to generate fracture varied significantly among anatomical location, indicating boundary conditions influence failure threshold. Further, these injury criteria were substantially different than previously reported criteria for other loading events (e.g., automotive), highlighting the importance of developing injury criteria specific for the intended application. An existing finite element human body model designed for automotive impacts was also assessed for its applicability to predict injury in these high-rate loading scenarios, and performed well for peak force, but not for the force-time curve shape. This is the first study of its kind to assess injury risk resulting from shield behind armour blunt trauma, and results from this work will inform a protective standard to assess ballistic shields. / Thesis / Doctor of Philosophy (PhD) / Ballistic shields used by defence personnel are designed to stop incoming bullets by deflecting or absorbing them. In the process, the back-face of the shield undergoes a rapid deformation that can potentially cause an upper extremity injury to users, an injury mechanism termed behind shield blunt trauma. This work aimed to quantify the injury risk that this mechanism poses at four locations along the upper extremity: the hand, wrist, forearm, and elbow. This was conducted by modifying and employing a crash test dummy upper extremity and measuring loads applied to the upper extremity in a ballistic testing range. Assessment of whether these loads caused injury was conducted using cadaveric specimens and testing them to failure. An existing finite element human body model was also assessed for its applicability to predict injury in these high-rate loading scenarios. Results from this work will inform a protective standard to assess ballistic shields.

Lower leg injuries commonly occur in both automobile accidents and underbody explosive blasts, which can be experienced in war by mounted soldiers. These injuries are associated with high morbidity. Accurate methods to predict these injuries, especially in the foot and ankle, must be developed to facilitate the testing and improvement of vehicle safety systems. Anthropomorphic Test Devices (ATDs) are one of the tools used to assess injury risk. These mimic the behavior of the human body in a crash while recording data from sensors in the ATD. Injury criteria for the lower leg have been developed with testing of the leg in a neutral posture, but initial posture may affect the likelihood of lower leg injury. In this thesis, the influence of initial posture on key injury assessment criteria used in crash testing with ATDs was examined. It was determined that these criteria are influenced by ATD leg posture, but further work is necessary to determine if the changes in outcome correspond to altered injury risk in humans when the ankle is in the same postures. In order to better quantify the forces acting on various areas of the foot and correlate those with injury, allowing for development of new criteria, a purpose built force sensor was created. An array of these sensors was incorporated into a boot and used to instrument an ATD leg during impact testing. The sensors provided useful information regarding the force distribution across the sole of the foot during an impact. A numerical simulation of the active material in the sensor was also created to better understand the effect of shear loading on the sensor. This work furthers the understanding of lower leg injury prediction and develops a tool which may be useful in developing accurate injury criteria for the foot and lower leg. / Thesis / Master of Applied Science (MASc) / This work investigates how the posture of the lower leg of a crash test dummy can influence the interpretation of crash test results. A tool was created to measure forces acting on the foot during testing. The force measurement uses a material which changes resistance when it is compressed.

Injuries to the lower extremity are frequent and severe in frontal automotive collisions, often leading to pain and long-term impairment. Most injury criteria developed for the lower extremity are conducted with the foot and ankle in a neutral posture, do not take into account footwear, and assess injury risk to the entire lower extremity at the tibia. An instrumented boot, designed to address some of these challenges, was calibrated over a range of impact energies expected in frontal automotive collisions. A dynamic calibration method was developed to convert changes in voltage across a piezoresistive polymer to the applied axial force. The instrumented boot was then used to examine the axial impact response of two commonly used Anthropomorphic Test Device (ATD) lower legs, under altered ankle postures. Both posture and ATD model were found to affect the load distribution on the foot, highlighting the need to establish injury limits for non-neutral postures as well as selecting the appropriate ATD model. The instrumented boot provided regional loading information that was not reflected in standard industry metrics, emphasizing the importance of increased instrumentation in this area. A technique was developed for mounting cadaveric feet to ATD tibia shafts, in order to gather industry-relevant load data while examining the impact characteristics of the foot. Load data were collected at the plantar surface of the foot using the instrumented boot, as well as the tibia load cells in the ATD shaft, that highlighted differences in load transmission through cadaveric and ATD feet. Understanding the impact characteristics of ATDs under non-standard ankle postures as well as examining the load transmission through cadaveric feet highlighted some shortcomings with current injury assessment techniques. The results of this work can be used to improve future collision testing practices, in order to reduce the incidence of lower extremity injuries. / Thesis / Master of Applied Science (MASc) / Foot and ankle injuries are common in automotive collisions and often lead to pain and long-term impairment. Experimental work on these types of injuries is traditionally conducted with the foot and ankle positioned in a neutral ankle posture, which does not reflect the range of ankle postures individuals may assume in a car crash. The purpose of this work was to use biomechanical tools to assess foot/ankle injury risk. Impact testing was performed on two commonly used crash test dummy lower legs in conditions relevant to those experienced in car crashes. A technique was developed to mount cadaveric feet to crash test dummy tibias to gather injury information of the foot, while also collecting load data in the tibia shaft – relevant metrics for industry crash testing. The results of this work outline the shortcomings of traditional injury assessment methods and may be used to improve future practices.

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.

An under-body blast (UBB) refers to the use of a roadside explosive device to target a vehicle and its occupants. During Operation Iraqi Freedom, improvised explosive devices (IEDs) accounted for an estimated 63% of US fatalities. Furthermore, advancements in protective equipment, combat triage, and treatment have caused an increase in IED casualties surviving with debilitating injuries. Military vehicles have been common targets of IED attacks because of the potential to inflict multiple casualties. Anthropomorphic test devices (ATDs) are mechanical human surrogates designed to transfer loads and display kinematics similar to a human subject. ATDs have been used successfully by the automotive industry for decades to quantify human injury during an impact and assess safety measures. Currently the Hybrid III ATD is used in live-fire military vehicle assessments. However, the Hybrid III was designed for frontal impacts and demonstrated poor biofidelity in vertical loading experiments. To assess military vehicle safety and make informed improvements to vehicle design, a novel Anthropomorphic Test Device (ATD) was developed and optimized for vertical loading. ATDs, commonly referred to as crash dummies, are designed to estimate the risk of injuries to a human during an impact. The main objective of this study was to develop and validate a Finite Element (FE) model of the ATD lower limb. / Master of Science

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