Weight-saving designs are essential in vehicle manufacturing in order to reduce resource consumption and, ultimately, costs. But the new lightness of automotive life does have its price: noise in vehicle interiors is an undesirable consequence of this trend. With its new Terophon HDF, Henkel has developed a novel and highly efficient acoustic dampening material specifically for the automotive and transport industries.
The name HDF stands for high damping foam. These foams are capable of dampening noise-producing vibrations extremely fast and well, thus “swallowing” the acoustic effects. The idea for developing this material was prompted by the continuing trend toward lightweighting in the automotive industry. To save weight, car design engineers are using ever thinner sheet steel material and turning to alternatives such as aluminum and magnesium. However, these new material grades usually have poorer acoustic performance, which results in noticeably higher driving noise levels inside the car.

Stopping vibrations
Noise is mainly caused by the engine, the transmission and the axles. The acoustic vibrations generated by these sources are propagated throughout the car so that they become audible to the occupants.
Up to now, vehicle designers have tried to combat these effects by installing more and more sound-damping bulkheads. But designing and building these parts is both time-consuming and costly.
The innovative material from Henkel tackles the problem at source instead of fighting the symptoms. The aim was to dampen the sound right at the point where it is generated. This requires a highly efficient material that can eliminate vibrations quickly and completely. Henkel specialists demonstrate how this works by dropping a steel ball onto a flat mat of Terophon HDF foam only a few millimeters thick. Instead of bouncing back off the mat, the ball stops dead upon impact. Trying the same experiment with a conventional sound-damping foam demands a high degree of agility from the experimenter, who has to quickly catch the ball as it bounces up from the foam before it has a chance to rocket off the table onto the floor.

This acoustic foam offers many advantages for car manufacturers. In addition to improving the acoustic driving comfort, it can significantly reduce the weight of the car. In the case of a car door, for example, the standard acoustic damping mat weighing around 500 grams per door can be eliminated by replacing the anti-flutter adhesive with more or less the same weight of new Terophon HDF. In a four-door limousine, this results in an overall weight reduction of about 2 kilograms.
A further advantage is the ease with which the new Henkel product can be installed into the vehicle. Terophon HDF is tailor-made as a drop-in part to customer specifications. All that needs to be done is to integrate the part at the desired place in the vehicle.