Motor vehicle crashes claim thousands of lives each year in the US, and injure millions more. The thorax is the region of the body at greatest risk for serious injury, and thus is of interest for increased protection. In order to improve systems providing occupant protection, a better understanding of the thorax is required, particularly for vulnerable occupants. The work of this dissertation is focused on increasing understanding of the thorax, and does so by examining instrumentation commonly used on the thorax, by introducing a novel analysis technique for understanding thoracic characteristics, and finally by presenting response and injury data for side impact loading.

The first study presented here provides an answer to the question, “Do chestbands alter thoracic response to impact?” This was accomplished by conducting a series of repeated impacts on two post-mortem human surrogates (PMHS), at the same impact velocity with 0, 1, and 2 chestbands. This was done for various impact speeds for a total of 22 impacts on the two subjects. `Response’ was divided into global response, defined as chest deflection and thoracic stiffness, and local response, defined as the individual rib strain. Results showed no significant difference in global or local response, thus providing support for the commonly held assumption that chestbands do not alter thoracic response to impact.

The second study introduces an analysis method, looking at rib strain as a function of chest deflection. An understanding of this relationship is intended to help bridge the gap between existing deflection-based injury criteria and strain-based injury prediction in finite element human body models. To this end, the strain-deflection (S-D) relationship was explored by rib level, fitting five different models to the data and constructing response corridors. It was additionally observed that the S-D relationship, or curve trajectory, tends to remain consistent across impacts on the same subject, even when those impacts are conducted at different velocities.

The final study of this work begins an examination of thoracic response and injuries occurring in small, fragile, elderly females involved in side impact vehicle crashes. The testing methodology is described, which includes a door intrusion and lateral underbody motion applied to a subject who is placed on a mass-production driver seat equipped with a side airbag, belted (with pretensioner), and interacts with a mass-production door liner. Rib fractures were the most common injury observed, with the first fractures occurring anteriorly on the struck side, followed by fractures anteriorly on the non-struck side and fractures posteriorly on the struck side. Spinal acceleration values, chest deflections, airbag pressures, and seatbelt tensions are reported. While this study does provide a valuable understanding of the injuries in the employed impact mode, it is intended that future tests similar to these may be conducted and that the combined dataset may be used to produce response corridors and a thoracic injury criterion specific to small, fragile females.