What it is and what it does
The crumple zone is a crash protection feature. It is usually located at the front of a vehicle (see section A on diagram on right), but many cars have an additional crumple zone on the rear (section B). Crumple zones are often made of lightweight plastics and polymer fibre so that they can easily crush if need be.
How it works
Crumple zones are designed to crush in a gradual way during a crash in order to absorb majority of the car’s impact energy and keep it away from the passengers. This process is called a “controlled crush”. Some of the energy the crumple zone absorbs from the crash is then given out in the form of heat and sound.
The shorter the time the car takes to stop once having crashed, the greater the force of impact. Crumple zones decrease the force inflicted onto the passengers, in effect adding time to the crash, by absorbing the crash’s energy. This relates directly to Newton’s Second Law.
Development
Before 1959, it was believed that the stronger a car’s structure, the safer it was. However, it was found that having too strong a structure was dangerous because the front of the car would not absorb any of the impact’s force, instead it would be inflicted onto the passengers. Also, early crumple zones were not constructed to crush in a predictable way like the ones made today are. Instead, they would end up crushing on top of passengers, causing serious injuries.
Today, cars are designed so that the engine is pushed under the main body of the car during a crash so that the crumple zone can be used to its maximum ability without damaging it. Crumple zones are now standard in every car, with their main structure centred in the middle 50% of the front bonnet. They are also made of materials that will absorb some of the impact of a crash and minimise the likelihood of injury.