Application of Scaled Deflection Injury Criteria to Two Small, Fragile Females in Side Impact Motor Vehicle Crashes 2018-01-0542

Thoracic injury criteria have been previously developed to predict thoracic injury for vehicle occupants as a function of biomechanical response. Historically, biomechanical testing of post-mortem human surrogates (PMHS) for injury criteria development has primarily been focused on mid-sized males. Response targets and injury criteria for other demographics, including small females, have been determined by scaling values from mid-sized males. The objective of this study was to explore the applicability of scaled injury criteria to their representative population. Two PMHS were subjected to a side-impact loading condition which replicates a near-side, MDB-to-vehicle impact for the driver. This was accomplished using the Advanced Side Impact System, or ASIS, on a HYGE sled. The sled acceleration matched the acceleration profile of an impacted vehicle, while the four pneumatic cylinders of the ASIS produced realistic door intrusion. Subjects were elderly females ages 61 and 83 years, approximately 5^th percentile in height and weight. Each subject was placed in a mass-production driver seat equipped with a side airbag, and was restrained with a 3-point belt. Instrumentation measured sled pulse, door intrusion, airbag pressure, seatbelt tension, occupant chest deflection, rib strain, and accelerations of the spine and pelvis. A full anatomical dissection was performed subsequent to each impact and AIS injury codes were assigned to the observed injuries. Fracture timings were identified using the strain gage outputs. Observed injuries were primarily rib fractures, located either near the sternal end of the rib or near the vertebral end of the rib. Both subjects experienced AIS = 3 injury severities, but their response values at the time of reaching AIS = 3 corresponded to p(AIS ≥ 3) ranging from 5% to 15%, depending on the selected criterion, thus demonstrating the need for data representing vulnerable populations. Injury mechanisms, as determined through fracture timings and high speed video, included interactions with the intruding door and the side airbag, and potential influence from the belt pretensioner. Further inquiry into the role of these vehicle components on small female PMHS response is recommended.