New sandwich elements with quality surfaces are learning from nature
According to Bayer MaterialScience, the automotive body of the future is lightweight, helping to reduce energy consumption in traffic, but these materials have to be very stiff to give a vehicle the necessary stability
Bayer MaterialScience will present a new concept at K 2013 plastics trade fair (October 16 – 21, 2013) in Düsseldorf (D). It is for designing a vehicle’s exterior skin and is fulfilling the dream of drivers for smooth, quality surfaces. The company is breaking new ground in the development of parts with a sandwich structure and allows automakers to increase productivity. At the show, the company is showcasing a sample trunk lid, the development of which was modelled on nature, not in one, but two ways.
The sandwich material has a lightweight core but a hard shell. The outer layer, continuous glass fibre mats are impregnated with a thermoplastic polymer formulated from polycarbonate. All the fibres are wetted and fully coated by the plastic matrix. This is the key to the high stiffness of the edge layers in a sandwich structure, states Ulrich Grosser, team leader for advanced technologies at Bayer MaterialScience. Polycarbonate blends such as Makroblend® shrink only very minimally, and the process results in a very smooth, high quality surface. It can subsequently be coated to achieve the desired appearance, for example with coatings based on polyurethane raw materials from Bayer MaterialScience.
In a second step, the top and bottom of the trunk lid are joined and the resulting hollow space is filled with Baysafe® polyurethane foam. It is the very low density of the foam making the component so lightweight. Since the foam is also very stiff, and adheres to the entire outer surface, the component is extremely resistant to minor damage.
In the event of a collision, the foam absorbs energy, enhancing the safety of passengers and pedestrians. It is an excellent thermal insulator, meaning it makes major contribution to energy management inside a vehicle, meaning that the air conditioning and heating can run at low settings and consume less energy. In turn this reduces fuel consumption and CO2 emissions. Drivers do not have to stop as frequently to refuel. In electric cars, these advantages save battery power and increase a vehicle’s range. Thanks to its good sound insulation properties, the foam further ensures a quiet cockpit.
Also antennas can be embedded in the foam very efficiently and permanently. Unlike metal components, polymers permit undisrupted reception across a wide frequency range. Additional functions up to and including lighting, can be integrated into the sandwich component.