Male-Female Comparison of the Biomechanics of Reclined Occupants in Frontal Impacts

Despite widespread advancements in automotive safety and occupant protection, motor vehicle crashes are still a leading cause of fatalities in the United States and around the world. More recently, increased attention has been brought to field data studies suggesting greater injury risk for females compared to males. Data on the responses of females is vital in determining the reason behind these sex-based differences in injury risk, but few sled tests have been conducted with female subjects, with most cases being of either small (5th percentile) or obese anthropometries. Since numerous sled tests have been conducted using mid-size male post mortem human subjects, anthropometry-based scaling of mid-size male responses is a potential approach to leverage this mid-size male data for a broader range of applicability. However, scaling across large differences in anthropometry has been shown to yield less accurate results, and scaling across sex has been understudied. As a result, this thesis aimed to characterize male-female differences in reclined occupant response, determine if scaling to predict female responses from male responses is suitable for a reclined condition, and evaluate the effectiveness of varying anthropometry-based scaling techniques in predicting female responses from male responses. To accomplish this, frontal impact sled tests were conducted on three mid-size female post mortem human subjects in a reclined posture. These tests were intended to mimic the test condition and occupant environment of a previously run test series using mid-size male subjects. Notable injury patterns in the pelvis and thoracolumbar spine regions were observed in this reclined condition and so comparative analysis focused on these regions. Sex-based variations in the geometry of the pelvis and soft tissue surrounding the pelvis were observed. Nonetheless, the females exhibited similar pre-test spinal curvatures and kinematics to the males, and generally, the female and male subjects exhibited similar kinematic and injury responses in this reclined frontal impact sled test condition. Geometric scaling using dimensional analysis was then implemented on the male data to test the effect various scale factors had on predicting female response. Marginal differences in the predictive capabilities of the different anthropometry-based measures were found, but, in general, the scaled male responses failed to accurately predict the female responses. Overall, this thesis highlighted the need for further whole body sled tests with mid-size female PMHS to further investigate male-female differences in occupant kinematics.