Fehrer and Aunde: Collaboration on lightweight roof with a soft look

The Smart automobile brand stands for innovation. Automotive supplier Fehrer is also good at finding new opportunities and turning the ordinary into something a little bit different. Together with its sister company Aunde, Fehrer has discovered new synergies that also benefit Smart.

The Smart’s innovative textile roof went into series production in September 2016: some 10,000 roofs have since rolled off the assembly line. This textile innovation was made by the Aunde Group companies.

Photo 1 caption: The customisation options in the textile area are countless. Moreover, the new surface of the lightweight roof is dirt and oil repellent, UV resistant and waterproof. Photo: FEHRER

Ode to the tried and tested: sandwich construction
The first generation of the lightweight roof was made in the Fehrer factory. The sandwich construction was considered an innovation and convinced with weight and technical design freedom. Like its predecessor, the new lightweight roof with a soft look is also made of a mixture of polyurethane, glass fibre and paper honeycomb. And yet there is a big difference between the two: the latest version has shed its thermoplast outer skin. The fabric is now the most important component in the roof’s outer surface.

New convinces: fabric that looks soft

The fabric used in the outer skin of the new lightweight roof is not only convincing, it is also versatile: The roof’s cover is dirt and oil repellent, UV resistant and waterproof. But that’s not all. The fabric shows just how resilient it is already during the manufacturing process: it perfectly withstands the high mechanical stresses it is subjected to during back compression moulding.


AUNDE Group adds manufacturing depth
“It was clear that we would collaborate with our sister company Aunde when we got this order. They’re the experts in technical textiles. Aunde’s experience with and knowledge of textiles are what enabled us to realise this project,” explained Wolfgang Ehnert, PU Product Development Manager at Fehrer Group. The manufacturing depth is optimal for customers. The Aunde Group did all of the work on the lightweight roof in-house – from the development of all of the parts to the production of the lightweight roof with a soft look itself.


Photo 2: The lightweight roof with thermoplastic outer skin already led to a 50 % weight reduction compared to a conventional steel roof construction.

The benefits of the textile roof convince
The benefits of the new generation of the lightweight roof with a soft look are the same as its predecessor, but their intensity has increased. “We were able to reduce the weight of this new version by another kilo,” said Tobias Freitag, developer and project manager. An intelligent combination of textile skin, load-bearing PUR fibre composite layers and a honeycomb core in a sandwich construction has made the lightweight roof 60 percent lighter than a steel roof – with the same rigidity and considerably higher bending strength. In contrast to the traditional composite components, the individual layers are not glued in a complex, multi-step process but are manufactured in a single operation. This means that the component can be produced a lot more efficiently.

Source: Daimler AG

The customisation options have also increased in the textile area. “You can have any color you want – the sky’s the 
limit – in any quantity,” said the project manager about the color design.

Aunde specialises in spun-dyed, textured polyester thread. The textile specialist from Mönchengladbach used sustainable materials and manufacturing processes to make the textile outer skin of the lightweight roof. In addition to the existing color palette, custom colors can also be quickly developed and produced.