Car accident investigations have shown that the head, the chest and the abdomen are the three most vulnerable body regions in side impacts, when serious-to-fatal (MAIS 3-6) injuries are considered. Injuries are much more common to occupants seated on the struck side than to those on the non-struck side. The development of new side impact protection systems has therefore been focused on struck side occupants.
The first airbag system for side impact protection, jointly developed by Volvo and Autoliv, was introduced on the market in 1994. The SIPS bag is seat-mounted and protects mainly the chest and the abdomen, and also to some extent the head, since the head's lateral relative displacement is reduced by the side airbag, thereby keeping the head inside the car's outer profile. However, if an external object is exposed in the head area, for example in a truck-to-car side impact or in a single car collision into a pole or a tree, there is a need for an additional head protection device.
Such a device, called the Inflatable Curtain (IC), jointly developed by Volvo and Autoliv, is described in this paper. The IC is an additional improvement to Volvo's unique SIPS and SIPS bag systems. It consists of two layers of fabric in what is known as one-piece woven technology. The IC is folded into a thin package, and is attached to the roof rail and the upper part of the A-pillar. When inflated, it covers the upper half of the side window, from the A to the C pillars, thereby substantially increasing head protection for both front- and rear-seat occupants. The performance and effects of the IC, in car-to-car and single car side impacts, are presented and discussed in the paper.