When a car crashes and its protective airbags are inflated, where do the airbag covers go to stop them breaking your nose?
Airbag covers are formed from moulded plastic and have lines built into them that are much thinner than the rest of the cover. When the airbag inflates, it forces its way through the covers, which fracture along these very thin lines. Obviously, it is important that the cover does not become a projectile, so it also has other thin sections which act as hinges. These hinges ensure that the fractured sections of the cover rotate harmlessly away from the occupant, rather like a pair of barn doors swinging open. These thin hinge lines and fracture lines are often visible, sometimes looking like a large 鈥淗鈥� (especially in older or less expensive cars).
Airbag engineers pay particular attention to the design and fixing of any logos or manufacturers鈥� badges which are fitted to the cover in the centre of the steering wheel to ensure that the badge remains attached to one of the doors formed by the opening of the cover, instead of coming loose and causing injury. In the case of side-impact airbags contained within the seat, a similar effect is achieved by providing a weakened seam of stitching in the seat cover, immediately alongside the airbag. This is one good reason not to fit seat covers.
Advertisement
Airbag engineers also have to ensure that the rapidly unfolding envelope of the bag moves straight towards the person it is supposed to protect, rather than across the driver鈥檚 or passenger鈥檚 face and chest. This involves very careful analysis of folding patterns, predictive software and analysis of high-speed photography from test firings. Engineers have also learned a great deal from origami.
Ian Gordon, Carlisle, Cumbria, UK
Airbag technology is one of the most important improvements in car safety, but an improperly used airbag can do more than break your nose. Cover flaps are made of light plastic, ductile at working temperatures and designed to rupture to let the bag through as it expands. Fragments have been known to cause injuries, especially to the face, but these are usually mild. Nearly all airbag injuries result from the victim being too close to the airbag, or wearing a seat belt improperly. Some of the worst injuries result from putting a child in an improperly placed seat, or carrying them on an adult鈥檚 lap, which in some countries is now a criminal offence.
鈥淎irbag technology is one of the most important improvements in car safety, but an improperly used airbag can do more than break your nose鈥�
Remember that an airbag deploying is like a bomb going off in your vehicle. If you are too close to the explosion, you may be harmed by impact, blast, fragments or even caustic residues. If you are at least 25 centimetres away from the cover flap, properly seated, with your seat belt taut and correctly placed over your hips and shoulder, airbags are excellent. In this case, airbag injuries should be the least of your worries in an accident.
鈥淩emember that an airbag deploying is like a bomb going off in your vehicle, so you may be harmed by impact, blast, fragments or caustic residues鈥�
Jon Richfield, Somerset West, South Africa
You can see a picture of an already deflated airbag, with the split in the covers clearly visible, at:
Simeon Verzijl, McKinnon, Victoria, Australia