Hybrid lightweight design concept for the vehicle floor
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By presenting the Integrated Sandwich Floor, Röchling Automotive showcasesa vehicle floor concept featuring a hybrid design based on low weight reinforced thermoplastics. The structurally integrated load-bearing component allows weight and space savings and meets highest standards in terms of thermal management, rigidity and acoustics.
Lightweight and Safe Components
For the reasons stated above, globally active OEMs are interested in solutions in the field of lightweight design which can be used in series production. Accordingly, the basic development of the ISF took place in the research project “Light eBody”, a joint development effort by automakers, suppliers and research facilities around the world that was also sponsored by the German Federal Ministry for Education and Research. The goal for the cooperation was the development of a resource-efficient, lightweight and ready-for-production multi-material car body for electric vehicles. In the field of materials and manufacturing technology, Röchling Automotive was responsible for the development of the frontal inner floor.
Innovative Lightweight Materials
Optimizing Materials and Broadening the Concept
Röchling Automotive systematically expanded the expertise it gained during the Light eBody project with regard to the integration of various functionalities for complex applications in the floor of vehicles — both with conventional and alternative propulsion architectures — and made it usable for series production, consequently, it is possible to adjust the sandwich construction to suit the individual requirements of any application. In order to keep the necessary development process as efficient as possible, an early definition of the goals regarding integrated capabilities and material properties is helpful. Form, structure and material thickness of the vehicle floor component are then optimized according to these predetermined requirements and application-specific conditions. In this way, Röchling Automotive achieves the bonding of different layers into a multifunctional hybrid lightweight design component.
Lightweight Construction for New Propulsion Architectures
On the basis of Stratura, Röchling Automotive expanded the material range for the ISF further by developing Statura Hybrid. This solution features scalable physical properties that make it especially desirable for hybrid and pure electric vehicles. Depending on the individual demand, it includes one or several layers of aluminum foil to reinforce the material and, in turn, the resulting component. At the same time, Stratura Hybrid has a high electromagnetic compatibility (EMC), meaning that it provides protection against electromagnetic fields (so-called induction fields), which are generated whenever an electrical circuit is opened or closed. In pure electric vehicles in particular, these fields occur naturally and unavoidably when sudden load changes occur, for instance when an emergency stop is initiated at full speed. If no countermeasures are taken, induction fields generate potentially harmful electrical currents in neighboring electric components. Highly conductive materials like silver, copper and gold achieve an almost perfect shielding performance. However, in order to provide a cost-efficient floor solution with the highest possible EMC protection for hybrids and electric vehicles, Röchling Automotive integrates one or more microperforated aluminum layers into Stratura. The result is a high degree of protection — a shielding effect of over 110 dB can be realized with a sheet of aluminum just 0.1 mm thick.
Comprehensive Integration of Functionalities
After conclusively testing the concept using prototypes and demonstrators, Röchling Automotive currently focuses on the execution of specific vehicle projects. The various material approaches and the use of a sandwich design not only allow excellent thermal and acoustic characteristics to be combined in a single, very lightweight component — they also allow the complete substitution of vehicle floor systems. Compared to conventional floor modules, therefore, the ISF offers the potential to reduce weight by up to 30 kg, or 50 %. As a result, the integrated car floor concept meets the industry trend towards ever more clean and fuel-efficient vehicle designs.
Load-bearing Safety-relevant Component
Individual Manufacturing Optimization
The ISF’s flexible structure and high plasticity allow the integration of additional technical components such as wiring harnesses or conduits and provide several other benefits. The possibility of adding hollow profiles when using Stratura Hybrid shows one of these advantages: the concept’s individually adjustable geometry. Even in later stages of development, the solution’s properties can be changed to suit different requirements. Thus, Stratura Hybrid offers development engineers a significantly higher degree of flexibility compared to other pressed materials such as sheet molding compounds (SMC), and it is made possible by combining a more detailed material setup with Röchling’s so-called Softlofting process. By gently lofting the base materials within the press, this process generates a three-dimensional network of glass fibers bound in polypropylene. This allows mechanical and acoustic parameters to be adjusted individually and improves the acoustic absorption capabilities of the finished component significantly.
Readiness of a product for series production requires not only materials and development concepts — it needs realistic lean production processes too. This is why Röchling Automotive employs a time-saving and cost-efficient continuous molding process for its latest car floor system. Using the so-called One Shot concept, all materials including (if necessary) the aluminum hollow profiles and microperforated aluminum layers are pressed together simultaneously. This advanced production method was optimized in parallel with the material and structural development.
Components for the powertrain or for a wireless inductive battery loading infrastructure could be added in the future.
Application and Further Development
Following its holistic approach, Röchling Automotive developed the ISF much further than originally planned during the Light e-Body research project. The integrated vehicle floor concept is ready to save fuel and weight not just in cars with conventional propulsion, but also in vehicles with alternative propulsion architectures from hybrids to pure electric cars.
Moreover, thanks to its high potential for functional integration and minimal thickness, the ISF offers additional freedom regarding vehicle design and production. The concept thus opens up new and far-ranging perspectives for the development of clean, efficient and safe cars for tomorrow.
Röchling’s Integrated Sandwich Floor is a holistic approach to the development of low-weight, crash-resistant lightweight design components. As a hybrid vehicle floor, the ISF is highly flexible and can be structurally adjusted to suit a variety of applications. It consistently utilizes the potential of lightweight design components and shows that they can do much more than just act as substitutes for single components: They can also make complex structures lighter or allow entirely new ones to be built. Developed from the ground up as a multifunctional part, the ISF offers OEMs a space-saving weight-reduced solution for practically all propulsion architectures. In this way, Röchling Automotive demonstrates the potential of hybrid floor systems and supports customers in the implementation of lightweight design measures for enhancing efficiency and reducing emissions.