Bodyshell and passive safety: Light, rigid and safe

Sep 13, 2016

Lower weight, outstanding rigidity for optimum handling, low noise and vibration levels as well as a high level of crash safety – the bodyshell forms the basis for all of these on account of its high proportion of diecast aluminium components and ultra-high-strength and hot-formed steel panels.

Thanks to intelligent lightweight construction, the body is some 70 kilograms lighter than a conventional steel body. The front wings, bonnet, boot lid and large sections of the front and rear ends are made of sheet or cast aluminium. As in the front end structure, the spring strut mounts at the rear are made of diecast aluminium to optimise weight and enhance function.

The rear-end assembly is likewise based on an aluminium hybrid design: here the stable rear-end structure comprises diecast aluminium longitudinal member and cross member components, aluminium panels, and high-strength-steel components. Another feature worthy of mention is the material combination of aluminium for the stiff structural areas and steel for the deformation zones.

The E-Class is the first volume-produced model in this vehicle segment to feature diecast aluminium longitudinal members. Their design was inspired by bionics in the areas that need to be particularly rigid and strong. The effectiveness of the organic looking reinforcements was tested rigorously after preconfiguration by computer. In this way the designers were able to reduce weight and at the same time improve introduction rigidity in the axle link area as well as enhance the torsional stiffness of the entire rear-end structure.

In many areas, several components have been integrated and merged into a single diecast component. In conventional constructions, several steel components would have had to be assembled here. This approach cuts costs and also makes the aluminium bodyshell an interesting economic proposition. Alongside conventional joining techniques and the use of structural adhesive, the one-sided accessibility necessitates the use of "ImpAcT nails" - in these areas the cast aluminium parts are not joined by welding.

Stable passenger cell: the security of a Mercedes-Benz

The body is configured to offer a high level of crash safety. The E-Class Estate not only meets all current national and international laws, but also all rating requirements as well as the more stringent internal Mercedes-Benz safety requirements, which are based on what actually happens in real-life accidents.

A high-strength safety passenger compartment forms the core of this concept. It consists primarily of high-strength and ultra-high-strength sheet steel and panels with graduated wall thicknesses designed to withstand specific local stresses. Many segments consist of hot-formed steels.

The exceptionally dimensionally stable safety cell is surrounded by precisely calculated and tried-and-tested deformation zones which, thanks to optimised load paths and a combination of cast aluminium parts with ultra-high-strength materials, can deliver top results in the crash tests and ensure a high level of occupant safety.

An important contribution to pedestrian safety is the active bonnet on the new E‑Class. The technical basis is a comprehensive sensor system in conjunction with intelligent algorithms in the airbag control unit, which decides when to trigger. After the pyrotechnical actuators have fired, the bonnet lifts by a noticeable amount at the hinge in fractions of a second to create additional space between the bonnet and the components in the engine compartment.

All-round protection: PRE-SAFE® Impulse Side

For years Mercedes-Benz has been protecting car occupants with its PRE-SAFE® concept in a host of accident situations as, even prior to a crash, PRE-SAFE® can initiate various measures to move the passengers into a position in which they are best prepared for an imminent impact. Mercedes-Benz has continuously further developed this system based on the findings from in-house accident research.

Furthermore, for the first time the new E-class is equipped with the new subsystem PRE-SAFE® Impulse Side (optional extra). Together with the familiar PRE-SAFE® protection concepts for frontal and rear impacts, it allows a kind of virtual crumple zone on the side of the car, too. This zone therefore stretches right around the vehicle – in other words PRE-SAFE® 360°.

Compared to a front impact, only a limited crumple zone is available in the case of a side impact. PRE-SAFE® Impulse Side can move the affected driver or front passenger as far away as possible from the acute danger zone before the actual side impact. To do this, as soon as the system detects that a side collision is immediately imminent, air chambers in the side bolsters of the front seat backrests are inflated in fractions of a second. Consequently, the impulse is imparted moderately to the occupant, lessening the forces acting on them during the side impact. This can reduce the forces to which the occupant's rib cage is subjected during a side collision. The system is optionally available for the driver and front passenger as part of the Driving Assistance package Plus.

Three-point seat belts with pyrotechnical belt tensioners and belt force limiters are installed for driver, front passenger and passengers on the outer rear seats. The middle rear seat is equipped with a standard 3-point belt system. In addition, a host of airbags can be activated to provide occupant protection in an accident:

  • Front airbags for the driver and front passenger
  • Kneebag for the driver to protect the knees and stabilise the upper body, which can positively influence occupant movement in an accident
  • Windowbags in the roof area between the A-, B- and C-pillars to protect the head area of the driver, front passenger and rear passengers sitting in the outer seats
  • Combined thorax/pelvis sidebags for driver and front passenger, which are able to provide additional protection in the event of a side impact
  • Sidebags as optional extras for the outer rear seats