Bumpers

Bumpers are fixed on the front and rear part of the vehicle for protection. They lessen the risk of collision with other vehicles, objects or fixtures as they limit damage of impact to the bumper system only. For this purpose, they are designed and shaped to be crushed on impact and absorb force during the collision. A bumper cover is usually made of thermoplastic or thermoset plastic that is capable of absorbing energy from impacts. During the collision, it redirects the flow of force into the frame rails whose design and material can manage the impact.

The whole bumper system is composed of different parts: the cover, crushable energy absorbers, piston and mechanical energy absorbers bumper bracket and the bumper reinforcement or bumper bars. The last can be simply called as reinforcements. The shock absorbers are found between the bumper cover and the reinforcement. They may be made of foam or plastic and are usually spring loaded. During low-impact collisions, they allow the bumper to compress and go back to its original position. In this way, damage to the car is avoided.

Mechanical energy absorbers are the parts that crush, collapse and flex during impact; however, they go back to original state during minor collisions. They can still be reused even if they look damaged. These absorbers work as they flex during the impact. As they bend, they convert kinetic energy (the energy of an object in motion) of the car into heat. Bumpers also have brackets located between the car frame and the reinforcement. These bend during the impact; however, unlike the shock absorbers, they can break and thus, need to be replaced when broken.

Reinforcements or bumper bars are usually located behind the crushable energy absorbers. They are made of steel, aluminum, plastic or composite material. Steel reinforcements may range from mild to high strength and ultra high strength depending on the type of vehicle they are used for. Some bumper are designed with no covers and have the reinforcement placed before the mechanical energy absorber while some have the reinforcement bar in between the cover and the brackets. There are vehicles that have only the bumper reinforcement and brackets while others have composite bumpers molded with the reinforcement.