Two design principles have prevailed in body design. The body design can either be an integral body-frame or a frame with all attached superstructures. Mixed versions are also possible, with the design significantly increasing the stability of the frame. In all versions, the passenger cell must be preserved in the event of an accident. To this end, the front and rear ends are designed so that they absorb the energy of the impact via crumple zones.
The use of modern design and manufacturing methods, and the use of body panels whose reshaping and strength properties have been finely balanced, mean that despite the reduced weight, all safety-related aspects and requirements can be met.
In the car market, the integral safety body-frame is the result of this technological development and manufacturing technology.
NOTE:Always follow the repair instructions published in the existing workshop literature, particularly for repairs in the crumple zone. All of the specified safety requirements must be met after the work has been carried out.
The integral body-frame is completed with ancillary components, such as doors, hood, bumpers and other components. The advantages of this are:
- Maximum passive safety due to the stable passenger cell.
- Defined deformation behavior at the front and rear.
- High torsional rigidity and high flexural strength.
- Weight reduction.
- Economical manufacturing technology.
The safety of the driver and passengers is paramount for every body design. There are two key safety aspects in the body:
- Safety body cell.
- Crumple zone.
The safety body cell is characterized by the following design features:
- Stable pillars, door sills and door profiles.
- Integrated side impact protection in the doors.
- The doors are designed to open even in the event of extreme deformation.
Deformation behavior
Different materials and design features lead to staged deformation of the front and rear of the vehicle in an accident. The passenger cell remains undamaged, and the driver and passengers are not shut in.
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Bolted sheet metal crash element
NOTE:For more information on types of steel, please refer to the section on body materials.
The bolted crash element is made of high-strength steel. Built-in pre-determined folding points prevent damage to the cross member during gentle impacts. The use of bolts means that this can be quickly and cheaply replaced.
Side members can be manufactured from panels of different thicknesses. These are joined together through laser welding. These panels are called tailored blanks.
NOTE:Please note the model-specific instructions when repairing tailored blanks.
The rear of the vehicle, like the front of the vehicle, has structures which protect the passenger cell through staged deformation in the event of an accident. The design layouts, however, are adapted to the requirements of the rear area.
MPVs
The body of an MPV has largely the same design layout as a passenger car body. However, due to the different requirements of an MPV, the floor pan in particular had to be designed in a more stable manner. It is therefore produced as a frame construction with particularly high torsional rigidity and flexural strength.
If repair is required, the process is similar to the process for a passenger car body.
Convertible
The body of a convertible differs from the principle of the integral body-frame of a saloon due to the lack of a roof construction. To guarantee the high safety requirements, particular design changes are required within the floor pan structure.
These are:
- Reinforcements of the floor pan, in particular in the sill area.
- Reinforcements in the pillar area.
- Due to the lack of a roof construction, the so-called bridge design principle used in saloons cannot be applied here. Longitudinal and torsional rigidity must therefore be provided by other components.
Frame structures
Frame structures are used for off-road vehicles and light commercial vehicles. With these structures, a distinction is made between a separate frame structure, as on an off-road vehicle, and the composite structure of a light commercial vehicle.
The entire body structure of the commercial vehicle body differs fundamentally from that of the saloon car. The requirements of such a body cannot be compared with a passenger car body. The payload is paramount here. Accordingly, the stability requirements must also be taken into account in the body design.
These are:
- Floor pan as frame structure with high torsional rigidity and flexural strength.
- Thicker materials and greater reinforcements in the frame area.
- Partly large surface panels and high volume shaped parts.
- Side panels only make a small contribution to the overall stability of the body.
- Longitudinal crimping, reinforcements and bonded connections prevent the panel surfaces from oscillating during drive mode.
Off-road vehicles
The body designs of off-road vehicles are not subject to the principle of the integral body-frame. Their basic construction corresponds to a chassis frame with an attached body.
This stable chassis structure has significant advantages for off-road vehicles:
- High torsional rigidity for off-road use.
- High payload and large trailer capacity.
- High ground clearance.
- Stable attachment possibilities for all drive assemblies.
If repairs are to be carried out, a different repair technique is required for this body and frame structure.
A deformed frame structure requires high suction power during straightening repairs. Frequently, the body also has to be detached from the frame structure in order to carry out separate repair.
Due to the very stable frame structure, please note that the straightening behavior is completely different to that of a passenger vehicle. The frame and the attached body must be repaired independently of each other.
