Lanxess (Cologne, Germany) says its Tepex dynalite composite material is being used in the RANGE X-ALPS paraglider reclining harness manufactured by skywalk GmbH & Co. KG (Marquartstein, Germany). The competition challenges the athletes to cross the Alps by paraglider and on foot. The material is a high-performance, continuous fiber-reinforced and polypropylene-based composite. The harness’ footboard is made of a sandwich composite just one centimeter thick, comprising thin Tepex facings measuring just 0.5 millimeters and a polypropylene honeycomb core from EconCore N.V. (Leuven, Belgium).
To control a paraglider, the pilot must shift his body weight, while maintaining muscle tension. This is achieved by pushing the feet against the harness’ footboard. In extreme situations, such as sudden turning maneuvers when approaching a steep rock face, very high forces are applied to the footboard, comparable to fully depressing the brake pedal in a car to avoid an accident. “The footboard can easily withstand these loads. The flexural rigidity and flexural strength of such sandwich structures can be higher than that of sheet steel or aluminum depending on the thickness of the facings and the honeycomb core – but they have a much lower weight per unit area,” said Harri Dittmar, an applications engineer for Tepex.
The tough Alpine course requires pilots to have a high level of physical fitness, but also the lightest possible equipment. “We tested the sandwich sheets extensively and are very pleased with the low weight combined with the high rigidity and strength,” says Manfred Kistler, general manager of skywalk. The sheets are 20% lighter than earlier versions made from a carbon fiber-reinforced epoxy resin. The harness therefore weighs just slightly more than one kilogram. Another advantage is the low costs: the new component costs 25% less than the epoxy system, according to Lanxess.
Additional applications in automotive engineering
Lanxess says it sees major opportunities for sandwich composites of this kind in lightweight automotive construction, particularly in larger parts requiring rigidity, such as trunk floors, fuel tank covers, range extender housings, structural battery housings and seat components. “The composites could serve as an alternative to glass fiber mats or polyurethane spray foams for manufacturing trunk floors in passenger vehicles. One advantage for processors: they would no longer have to deal with reactive chemical systems and could eliminate considerable costs for equipment and safety systems,” said Martin Klocke, manager for lightweight construction business development at the Lanxess high performance materials business unit.
Fuel tank covers, which form part of the trunk space, are another conceivable application. They would be significantly lighter than their counterparts made of sheet steel or aluminum. Furthermore, functions such as slots, guides or mounts can be integrally molded in the covers in a single processing step to further cut costs.
Automated production of honeycomb composites
EconCore N.V. has developed a fully automated production system called ThermHex to manufacture honeycomb sandwich panels with Tepex composite skins. “Thanks to this technology, we can produce these ultra-strong sandwich structures cost-efficiently and in high, reproducible quality,” said Tomasz Czarnecki, technology manager of the company.