“Rohacell Hero” is a structural foam that has been developed by German chemical producer Evonik (Essen; www.evonik.com) for applications in the aircraft industry. The lightweight material can withstand extreme changes in temperature and high mechanical stress and can be used in external aircraft components where safety is a significant factor. Previously, honeycomb composites were used in these applications. Evonik recently opened a new facility in Shanghai / China for the production of Rohacell – see Plasteurope.com of 24.09.2014.

Rohacell foams are made from polymethacrylimide (PMI) and are already used in many landing flaps, winglets, and fairings on airplanes. PMI is often used as a core material in sandwich structures, which consist of a lightweight core and two thin layers of fibre-reinforced composite material. It is the only foam that is able to withstand the processing conditions found in the production of sandwich components, which sees temperatures of up to 180°C and pressures of up to seven bar.

The fine-pore foam has an elongation at break that is three times higher than standard materials and is mechanically resilient at temperatures down to -55°C and below. If damage is caused, for example, by foreign objects being thrown up from the runway, sandwich structures made with this foam exhibit visible dents, which remain local and do not spread. Tests on the material, including fatigue tests, were conducted by the German Fraunhofer Institute for Mechanics of Materials (Halle; www.en.iwm.fraunhofer.de).

A weight and cost comparison that Evonik carried out together with an Airbus parts supplier and the Airbus subsidiary CTC (Stade / Germany; www.ctc-gmbh.com), concluded that components made from the new structural foam are, on average, around 10% lighter and cost approximately 20% less to produce than equivalent honeycomb structures. At Airbus, tests on the material have been carried out for two years and the aerospace group expects the first components in the material to be produced in series in 2015.