Every area of a vehicle comes with its own challenges for manufacturers and suppliers. The underbody is one which has been a focus of attention in recent years.
New technology developed by companies such as Röchling Automotive is redefining the underbody by combining the floor interior, underbody and chassis into one component. This development arises from automotive manufacturers’ desire to reduce weight and improve aerodynamics. While the overall construction of vehicles has changed very little over a long period of time, the materials used and their degree of integration has seen much more rapid innovation.
The introduction of alternative drive concepts is also behind the reconceptualization and design of the floor plate or underbody. Low-weight reinforced thermoplastics have proven to be very flexible. Typically based on a non-woven material, new properties can easily be introduced into the material by combining glass fibers with thermoplastic fibers such as polypropylene or polyester.
Through the use of its Stratura material for electric vehicles, for example, Röchling Automotive aims to achieve the optimum: lower weight, better comfort, safety, and lower costs. A functional multi-layered construction unifies in a single component functions which were previously fulfilled by the carpeting, the metal car body, and the underbody panel. The thermal insulating properties of the Stratura material keep the interior warm while the acoustically efficient material structure ensures a pleasant atmosphere in the interior. The integration of the new sandwich approach by using Stratura can save up to 50% of the weight versus steel. Stratura is used for thermoacoustic structural components with waterproof dividing layer, interior decorative surfaces, and an exterior gravelproof coating.
Staying up to date with the latest development of the technologies and assembly of the vehicles is not always easy for suppliers. The integration of metallic foils and structural metallic elements requires additional skills such as the calculation and simulation of stresses, or the development of appropriate assembly and connection concepts. The main goals, to reduce weight and to enhance NVH characteristics and therefore the comfort of the driver, will remain the key drivers of further activities in this field. Röchling Automotive can combine the functions of the interior floor, underbody, and chassis by using floor elements made of Stratura. Röchling Automotive is also working on the integration of metallic elements.
Spotlight on electric vehicles
A special focus is being placed on the evolution of lightweight electric cars of the future. With these cars every kilogram counts. Röchling Automotive has a number of prototype products which are already in field tests. The company was a participant in the Light e-Body project, for instance. As part of this project, which focused on sustainability and efficiency, multiple supplier companies and automotive manufacturers worked on the development of an industrial-scale lightweight body for an electric vehicle. Röchling’s floor element made from Stratura combines the interior carpeting, acoustic insulation material and the chassis floor plate.
A number of concepts for the improvement of aerodynamics, such as active guidance of the air by active speed lips, were developed in parallel. Active speed lips bring an improvement of the cd-value of up to ten points according to Röchling Automotive. Small design modifications can enhance the underbody air flow and therefore also have an effect on the fuel consumption. In addition, underbody components can positively influence the driving performance, particularly in critical situations such as high speed runs or regarding the uplift at the rear wheel axle. Under these circumstances optimally shaped underbody parts help to improve the safety of the vehicle.
The underbody also serves as the area in which batteries are best positioned in the car. One particular aspect holding back the acceptance of low-emission vehicles by the market to date is their limited range. This has resulted in a flood of investments into innovations and technological developments aimed at improving batteries. Röchling Automotive has for several years been among the suppliers developing new solutions related to batteries. The focus has been in the area of cell frames with integrated cooling function and insulating sheets. Special solutions for the cooling and encapsulation of batteries have been developed.
Last but not least, inductive charging and fuel cell components have been part of the Röchling Automotive approach to new business and green cars. Conductivity within plastics is as difficult as it is fascinating. The limits in terms of functionality and safety have been redefined. This included the development of the ion exchanger needed in fuel cell cars. Here, Röchling Automotive has developed an elegant solution that the company says meets all technical and commercial requirements.
Inspiration from Mother Nature
Writing in the Röchling 2014 magazine Klaus Pfaffelhuber, Röchling Automotive Manager Advanced Development Aerodynamics & Acoustics says lightweight metals make it possible to combine the respective advantages brought by the properties of different plastics – “just like Mother Nature”.
Nature literally provides many constructive examples of how and where stable structures can be reinforced to be able to withstand even stronger forces, he writes. Spaces that have no impact on strength can be used for thermo-acoustic insulation purposes.
Röchling tests and evaluates multi material systems as part of a comprehensive approach to lightweight construction. An example is the Stratura family of materials created through participation in the StreetScooter project of RWTH Aachen university. The project was aimed at eliminating the need for sheet metal and combining carpet, floor, and underbody cover into one component.
Founded in mid-2010, StreetScooter has been developing new mobility concepts for cities and high population density areas. At the request of Deutsche Post StreetScooter has developed a special vehicle for the joint delivery (letters and parcels). In collaboration with a team of RWTH Aachen also a pedelec for delivery has been developed.
Röchling Automotive is also active in the light e-body project, which focuses on the lightweight chassis for e-vehicles. This is how new specializations are created and form the basis for the solutions of tomorrow, writes Pfaffelhuber.