Large-area structural part in thin-wall design


PHOTO: Blanks made of Tepex dynalite (left); shaped and overmoulded blanks with numerous integrated functions (right). The flat areas of the module rack are only one millimeter thick, thanks to Tepex dynalite

WITH the help of continuous-fibre-reinforced, semi-finished thermoplastic composites, structural parts with a large surface area can be designed to be very thin and therefore lightweight.

They can also be equipped with numerous functions, as demonstrated by a new module rack, only one millimetre thick, for the S-Class convertible from Mercedes-Benz. Various controllers are mounted on this component. The rack is fabricated in a hybrid moulding process from Tepex dynalite 102-RG600(2)/47%, a continuous-fibre-reinforced, semi-finished polyamide 6 composite from Lanxess subsidiary Bond-Laminates GmbH, based in Brilon, Germany.

“The result is a component that weighs about 50% less than its aluminium predecessor. What’s more, the low weight and integrated functions simplify assembly, which is an additional cost advantage,” said Julian Haspel, key account manager at Lanxess.

The module rack measures 0.5 x 0.5 meters and is installed under the trunk. It was developed by Mercedes-Benz Cars Development together with several partners. Lanxess engineered the concept for the mechanical design of the component and calculated various load scenarios. The mould is manufactured by Georg Kaufmann Formenbau.

“The rack could also have been fabricated in a simple injection moulding process. But because of the part’s large surface area, that would have required thicker walls in order to keep the injection pressure sufficiently low. Although this would already have reduced the weight significantly compared to a part made of aluminium, there was still room for improvement,” explained Haspel.

To go even lighter, the hybrid moulding process was selected. It involves a Tepex dynalite blank, which is heated, plasticized and shaped in a one-shot process, and then overmoulded with Durethan BKV 30 H2.0, a glass fibre reinforced polyamide 6 from Lanxess.