Street Shark 4.0, Cooperative Project with Innovative Rear Wings

Functionally integrated PU sandwich design in 3D format

The use of a sandwich design consisting of a lightweight core and outer layers made up of a fiber-reinforced composite material for structural components is not a new concept. However, in the past, the higher costs of this method often led to turning to aluminum solutions, which are heavier but more cost-efficient. FRIMO took on the challenge of developing clever, economic lightweight construction solutions in this multi-sandwich design which are also suitable for large-scale production.

The latest development, the Street Shark 4.0, is a spoiler on a Corvette from cooperation partner Callaway, who specializes in car body manufacturing, vehicle repairs, and modifications for racing. As part of the ADAC GT Masters, Team Callaway employs a 600 HP Corvette C7 GT3-R with a 6.2-liter V8 engine. The spoiler on this Corvette features an innovative three-dimensional PU sandwich construction (picture 1) fitted with a bionic surface structure modeled after shark skin (picture 2) in certain areas. An important cooperative partner in this project is the company Eschmann Textures. The optimized Corvette was showcased on Eschmann’s stand at the K Trade Fair in Düsseldorf this year and aroused big interest among the expert visitors.

In the past, a variety of core materials have been used for the different sandwich structures, such as PET, PP or PU foams, as well as balsa wood or bamboo in the form of plates or sheets. (pictures 3 and 4) Because of continued developments by FRIMO, it has become possible to directly produce more complex three-dimensional sandwich structures from polyurethane using molded foams. For this purpose, a test tool was designed in which the three-dimensional core was first produced using hard PUR foam. In addition to the tool and mold carriers, the FRIMO TechCenter also features a PURe mix metering unit (picture 5) specially designed for matrix materials. Even while manufacturing the lightweight core, it is possible to integrate additional functions, such as taking fixation points or electronic elements into account.

Once the three-dimensional core is produced, the RTM process follows. The first step is to insert the lower layer of the preform made from reinforced fibers (carbon, glass, natural) into an RTM tool. After that, the molded foam core and then the upper fiber layer are inserted. After inserting the upper fiber layer, the RTM tool is closed and the low-viscosity PU matrix system is introduced. The low viscosity of the PU system enables rapid entry into the tool, and due to the snap cure, the start and duration of the hardening process can be adjusted relatively precisely in terms of timing. The process releases a relatively low amount of heat with a maximum reaction temperature of well below 100°C. For this reason, the concept is significantly more efficient for certain applications in large-scale productions and also sturdier than classic matrix materials. Because of the low tool temperatures (less than 100°C) and the low internal tool pressures, the foam core remains undamaged. Because only low clamping forces are required for the tool, ceramic tool inserts can be used. Unlike most processes typical on the market, more complex, large volume, three-dimensional structural components can also be directly produced in the desired geometry.

The equipment in the FRIMO TechCenter is designed to discharge components up to ca. 700 x 800 mm. Larger systems are currently being developed at FRIMO, some of which are already under construction or installed, including a system for component dimensions of up to 2 x 2 m. This makes it possible to manufacture larger three-dimensional components, such as the spoiler for the Street Shark 4.0, or for tests, prototypes, pilot projects or pre-series.

Picture 1 - Corvette with spoiler in 3D PU sandwich design

Picture 2 - Bionic surface modeled after a mako shark skin

Picture 3 - Sandwich sample of balsa wood

Picture 4 - Sandwich sample of natural fiber knittings

Picture 5 - FRIMO PURe Mix metering machine

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