Reducing occupant injury in rear-end collisions through the implementation of energy-absorbing foam to the seat base

• Main Author: Mansour, Rami
• Language: English
• Published: University of British Columbia 2011
• Online Access: http://hdl.handle.net/2429/30537

Rear-end collisions account for approximately $9 billion in medical and damaged property costs annually in the United States alone. These types of collisions account for nearly 30% of all vehicle impacts, making them the most common collision type. Soft tissue injury to the neck (i.e., “whiplash”) is typically associated with this type of collision. The vehicle seating system is the predominant safety device employed to protect the occupant during a rear-end collision. Currently, designers focus predominantly on seat base strength, seat back stiffness/compliance, and head restraint size and position as a means of mitigating injury. While all of these aspects are important and have increased the crashworthiness of the seat, the concept of utilizing the seat base as a component to further assist in whiplash protection has remained relatively unexamined. The addition of a supplemental safety system to the seat base may offer the potential for reducing injuries in higher severity collisions. This thesis examines the potential for deformable materials, (in this study energy-absorbing foam), to absorb transmitted energy to the vehicle seat in order to reduce the dynamic loading experienced by the occupant. The relationships between the type and geometry of the foam and occupant dynamics, and how they affect potential occupant injury (as assessed using selected neck injury criteria) are assessed and reported. Several energy-absorbing foams currently available have been investigated in order to determine the best foam type and geometry for a range of collision speeds. The results indicate that the time to completely crush the foam, dictated by foam relative density, stress vs. strain behavior, foam geometry, and acceleration pulse, can affect the degree to which injury potential is reduced for a large range of collision speeds. Further discussions of design considerations for implementation of such a supplemental system are also provided in this thesis. Reducing rear-end collision severity with the implementation of this device can potentially lead to a decrease in rear-end collision induced injury and fatality.