Background, Description and Evaluation of a New Side Airbag System
Published September 26, 1994 by Automotive Technology Group, Inc. in United States
Side impacts give rise to relatively more severe injuries than frontal impacts. A Swedish study has shown that the neck and the legs of the struck side occupant need to be better protected due to a risk of permanent disabilities. The head, chest and abdomen/pelvis need to better protected from a risk of life threatening injuries.
Improved protection in side impacts can be achieved with car body/door reinforcements and compliant bolstering (padding and/or airbag) on the inside of the door. A study has shown that a ventilated airbag of about 12 liter in volume, covering both the chest and the abdomen down to the armrest level, improves the protection in side impacts better than 50 mm of compliant chest padding. A suitable initial bag (over) pressure was found to be about 40 kPa. The 12 liter ventilated airbag resulted in 30-40% lower chest deflection and about 60% lower VC than the 50 mm padding in sled tests simulating full-scale tests. The airbag during its compression must be softer than the corresponding human body segment. The TTI was 30-45% lower with the bag. The deflection based criteria were found to be very sensitive to the door velocity. Pelvis padding (75 mm thick) effectively reduced the pelvic loads. The head ejection through the side window frame was reduced by an average of 30 mm by the side airbag and the neck load was also reduced.
The paper describes a door mounted side airbag system (including sensor) as well as a seat mounted system. The latter system has been developed by Autoliv together with Volvo and is the first side airbag system installed in serial produced cars for the 1995 model year.
To further improve the protection of the head/neck in side impacts a supplementary protective device, the "curtain", at the side window has been proposed.