Side impacts with intrusion close to the occupant are much more severe than those without intrusion. Different accident investigations have found intrusion to the passenger compartment in 90~IOO % of side collisions with serious to fatal (AIS 3+) injuries. It has also recently been found that the optimum position for the location of a sensor for a side airbag system is the rear lower quadrant of the front door - a sensor located in this sector would cover almost 90% of the impacts with (risk of) AIS 3+ injuries. These injuries occur above a 15-25 km/h velocity of the impacting car in car-to~car side collisions. A sensor for a side airbag should therefore trigger above this level of impact speed.

A sensor for a side airbag system can not be centrally located as a sensor for frontal airbags. An undeformed part of the car will not start to move until l0 ms after the first car—to-car Contact in atypical 50 km/h (30 mph) side impact. The side airbag must be fully inflated within 10-12 ms, while there is still about 100 mm of clearance between the door inner wall and the occupant’s chest. The sensor must therefore be located close to the outer surface of the car to trigger in time. This paper describes the evaluation of a door mounted side airbag sensor (developed by Electrolux Autoliv) by a new pendulum subsystem test method. The sensor element is a percussion cap that fires above a certain impact speed. The sensor is located in the rear lower part of the door at a certain distance from the door outer surface.

Full-scale tests with one car model and with mobile barrier front faces simulating rectangular (car-to-car impacts at right angle) as well as triangular (oblique car-to-car) side impacts were run at speeds around 20 km/h. Based on these full-scale tests a large pendulum test rig was developed, consisting of an impactor and a partial and reinforced car body of the same type as that used in the low speed full-scale tests. The rig rested on four rubber pads to simulate wheel tire contacts. Only the door had to be exchanged between each test. With pendulum weights of 550 and 620 kg (for rectangular and triangular barrier fronts respectively) and with a car body rig weight of 470 kg, the initial deformations of the door outer and inner panels were in good agreement with the corresponding full-scale tests.

The pyrotechnical side airbag sensor was evaluated by the pendulum test method. The sensor was located 200 mm above the door lower edge and 250 mm in from of the door rear edge A component. called a contact plate. hinged at its lower edge and covering impacts to the lower rear quadrant of the door was located close to the sensor and at a distance of 40 mm from the outer surface. The sensor triggered for impacts at three different areas covering the rear bottom quadrant of the front door at 6 m/s (22 km/h) with the rectangular barrier front and at 4 m/s (14 km/h) with the triangular barrier front (impacts at these two speeds but with the different barriers resulted in the same maximum deformation of the door). Some of the tests simulated higher bumper levels (vans, trucks). The sensor did not trigger for impacts at 2 m/s (7 km/h). It was also demonstrated that the sensor did not trigger for “kicking” (at 5 m/s) to the door.