The Mercedes S-class features a rear polyamide transmission

The Mercedes S-class features a rear polyamide transmission
Friday, October 16, 2015Description :
The world's first plastic transmission transaxle for an automotive rear cradle was developed by ContiTech Vibration Control and BASF for the Mercedes S-Class.

This innovation is made from the technical plastic Ultramid® A3WG10 CR, a specialty polyamide from BASF reinforced with glass fibers and optimized to withstand high mechanical loads. Compared to the old molded aluminum crosspiece, this highly durable component allows a 25% lightening, improves the acoustic and mechanical properties even at high temperatures and respects the latest standards in terms of collision. The expert capabilities of BASF Ultrasim® simulation software also played a key role in optimizing these properties.

The polyamide structural structural component fulfills all static and dynamic stress requirements to which a transmission beam is exposed: as a central component of the rear axle it absorbs the forces and moments transferred from the engine to the transmission and takes up Loads a constant part of the differential. This is why the Ultramid® crossbar is used on all Mercedes-Benz 4-wheel-drive models, with the exception of the AMG range.

In order to replace aluminum in this complex application potentially exposed to collisions, plastic must meet high mechanical requirements: the Ultramid® A3WG10 CR grade (CR = crash-resistant, which means impact-proof) is reinforced at 50% fiberglass so as to offer optimal strength and stiffness and have a low tendency to creep under constant stress. In addition, the material must withstand high bending torques. The component has an excellent acoustic profile NVH (NVH = noise, vibration, harshness in English or noise, vibration, jerk in French).

"The new transaxle for the rear axle marks a key milestone in the use of polyamides in automotive chassis. It has the potential to create a new trend in the automotive industry, "said Kai Fruehauf, Head of Commercial Division at ContiTech Vibration Control. "In order to replace the metal with high performance plastics, it is necessary to make optimum use of it and to adapt it to the particular stress situations, as BASF demonstrated by developing the grade Ultramid® for the crossbar of transmission. "

BASF used its Ultrasim® simulation software in the preliminary phase of development of the new cross member in order to determine the dimensions of the component, optimize its geometry and predict its potential behavior during injection molding and in operation: Simulation of loads Ultimate forces, dynamical loading forces and collision safety has very well reflected the actual behavior of the component.

ContiTech Vibration Control used Integrative Ultrasim® simulation to model the entire production chain, enabling it to define the geometry of the component at an early stage and to limit the number of prototypes.
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