Belted Occupant Kinematics and Head Excursion During the Airborne Phase of Vehicle Rollover: Evaluation of the Effects of Rollover-Deployed Curtain Airbags 2014-01-0527

It is well known from field accident studies and crash testing that seatbelts provide considerable benefit to occupants in rollover crashes; however, a small fraction of belted occupants still sustain serious and severe neck injuries. The mechanism of these neck injuries is generated by torso augmentation (diving), where the head becomes constrained while the torso continues to move toward the constrained head causing injurious compressive neck loading. This type of neck loading can occur in belted occupants when the head is in contact with, or in close proximity to, the roof interior when the inverted vehicle impacts the ground. Consequently, understanding the nature and extent of head excursion has long been an objective of researchers studying the behavior of occupants in rollovers. In evaluating rollover occupant protection system performance, various studies have recognized and demonstrated the upward and outward excursion of belted occupants that occurs during the airborne phase of a rollover, as well as excursion from vehicle-to-ground impacts. These studies have demonstrated the challenges of minimizing head excursion and preventing head-to-roof contact in high-severity rollover events, which involve multiple rolls, multiple roof-to-ground impacts, and often high roll rates. The purpose of the current study was to examine belted occupant kinematics and head excursion during the airborne phase of a rollover in a vehicle with rollover-deployed seatbelt pretensioners and side curtain airbags, with a focus on the effects of the curtain airbag. The test methodology of the current study was similar to prior studies and involved the use of a controlled, multi-revolution rotation of a vehicle about a fixed, longitudinal axis through the vehicle center of mass. Instrumented Hybrid III Anthropomorphic Test Devices (ATDs) were seated in the front outboard seating positions. Static inversion head excursions were measured prior to and following pretensioner deployment. Curtain airbags were inflated to a pressure consistent with that measured at 1.5 seconds following deployment and this pressure was maintained throughout the spin test. Each test involved spinning the vehicle up to a roll rate of approximately 270 degrees per second while constraining occupant motion and posture, then releasing the ATD and increasing the vehicle roll rate up to 720 degrees per second with dwells at approximately 90 degrees per second increments. Occupant motion, head excursion, head accelerations, neck loads, and resulting loading on the head were evaluated, and the effects of the presence of the curtain airbag and different initial occupant-to-seatbelt geometries were examined and documented.