Crumple zones, crush zones, or crash zones, are a structural safety feature used in automobiles, to absorb the kinetic energy from the impact during a collision by controlled deformation. This energy is much greater than is commonly realized. A 4,409 lb. car traveling at 37 mph.,before crashing into a thick concrete wall, is subject to the same impact force as a front-down drop from a height of 47 ft. crashing on to a solid concrete surface. Increasing that speed by 50% to 56 mph. compares to a fall from 105 ft.- an increase of 125%.
The specifics of crumple zone designs are usually proprietary information that auto makers are reluctant to divulge. They can vary widely, depending on the size and weight of the vehicle. Designers have to strike a balance between too much impact resistance and too little impact resistance. Simple designs can include frame segments built to bend in certain areas or collapse onto themselves. More advanced designs can utilize a variety of metals and other materials carefully engineered to absorb as much kinetic energy as possible. High-performance cars often use a honeycomb design, which offers stiffness under normal conditions, but can collapse and crumple in a crash.
Typically, crumple zones are located in the front part of the vehicle, in order to absorb the impact of a head-on collision, though they may be found on other parts of the vehicle, as well. According to a British Motor Insurance Repair Research Center study of where on the vehicle impact damage occurs: 65% were front impacts, 25% rear impacts, 5% left side, and 5% right side. Some racing cars use aluminum, composite/carbon fiber honeycomb, or energy absorbing foam to form an impact attenuator that dissipates crash energy using a much smaller volume and lower weight than road car crumple zones.
On September 10, 2009, the ABC News programs, Good Morning America and World News, showed a U.S.Insurance Institute for Highway Safety crash test of a 2009 Chevrolet Malibu in an offset head-on collision with a 1959 Chevrolet Bel Air sedan. It dramatically demonstrated the effectiveness of modern car safety design over 1950s design, particularly of rigid passenger safety cells and crumple zones.
The crumple zone concept was invented and patented by the engineer, Bela Barenyi, in 1937, before he worked for Mercedes-Benz. In 1952, he obtained a patent for the design of a car’s front and rear built to deform and absorb kinetic energy in an impact. The 1953 Mercedes-Benz Ponton was a partial implementation of his ideas, by having a strong deep platform to form a partial safety cell. He put the concept to use in 1959 on the Mercedes-Benz W111 Fintail, the first car to use crumple zones.
Crumple zones work by managing crash energy, absorbing it within the outer parts of the vehicle, rather than being directly transferred to the occupants, while also preventing intrusion into or deformation of the passenger cabin. This better protects car occupants against injury. This is achieved by controlled weakening of sacrificial outer parts of the car, while strengthening and increasing the rigidity of the inner part of the body of the car. This turns the passenger cabin into a "safety cell,"by using more reinforcing beams and higher strength steels. Impact energy that does reach the "safety cell" is spread over as wide an area as possible to reduce its deformation.
Low Speed Crash
The front of the bumper is designed, with crash tubes or crash boxes, to withstand low speed collisions (e.g., parking bumps) to prevent permanent damage to the vehicle. This is achieved by elastic elements, such as the front apron. In some vehicles, the bumper is filled with foam or similar elastic substances.
Crumple zones create a buffer zone around the perimeter of the car. Certain parts of a car are inherently rigid and resistant to deforming, such as the passenger compartment and the engine. If those rigid parts hit something, they will decelerate very quickly, resulting in a lot of force. Surrounding those parts with crumple zones allows the less rigid materials to take the initial impact. The car begins decelerating as soon as the crumple zone starts crumpling, extending the deceleration over a few extra tenths of a second.
Crumple zones also help redistribute the force of impact. Bending parts of the frame, smashing body panels, and shattering glass all dissipate energy so it is never transmitted to the occupants.
Absorbing and redirecting impact is great, but it isn't the only safety issue auto designers have to worry about. The passenger compartment of the car has to resist being penetrated by outside objects or other parts of the car, and it has to hold together so the occupants aren't thrown out. You can't make an entire car a crumple zone because you don't want the people inside it to crumple also. That's why cars are designed with a rigid, strong frame enclosing the occupants, with crumple zones in the front and rear. Force reduction and redistribution is accomplished inside the passenger compartment through the use of airbages.
Fuel tanks and battery packs, in electric or hybrid vehicles, need to be protected from impact to prevent fires or exposure to toxic chemicals. They can be designed so that a section of frame protects the tank, but that part of the frame can bend away from the impact. For example, if a car is rear-ended, the frame bends up, lifting the gas tank out of the way and absorbing some impact. Newer cars have systems that cut off fuel supply to the engine during a crash, and the Tesla Roadster, has a safety system that shuts off the battery packs and drains all electrical energy from the cables running throughout the car when it senses an emergency.
We all have seen images of spectacular crashes in which race cars tumble down the track, flinging parts in every direction as it is literally destroyed. Yet miraculously, the driver climbs out of the twisted wreckage and walks away uninjured. While these crashes look horrifying, all that spectacular destruction is spending kinetic energy, thus protecting the driver.
There is an unfortunate counterpoint to the concept, however. From the 1980s to the early 2000s, there were numerous racing fatalities due to overly stiff chassis. Probably the most widely known incident is the death of Dale Rarnhardt, Sr. in the 2001 Daytona 500. The crash didn't initially appear to be severe, and the car didn't seem to suffer extensive damage; however, that was exactly the problem. A great deal of the force of impact was transferred directly to the driver, causing a fatal skull fracture.
Challenger Crash Test Ratings
The NHTSA rated the 2019 Challenger, in its crash test ratings, as follows: