Fraunhofer and Partners Develop Light, Recyclable Blades

Researchers at the Fraunhofer Institute for Chemical Technology ICT have partnered with industry experts to develop thermoplastic foams and composites that make the offshore wind turbine blades lighter and recyclable.

The new materials are expected to help operators expedite and simplify the transportation, installation, disassembly and disposal of the ever-increasing offshore wind rotor blades, according to Fraunhofer.

Since the length of the blades is limited by their weight, it is essential to develop lightweight systems with high material strength, Fraunhofer said. The lower weight makes the wind turbines easier to assemble and disassemble, and also improves their stability at sea.

In the EU’s WALiD (Wind Blade Using Cost-Effective Advanced Lightweight Design) project, scientists at the Fraunhofer Institute for Chemical Technology ICT in Pfinztal, Germany,  are working with ten industry and research partners on the lightweight design of rotor blades. By improving the design and materials used, they hope to reduce the weight of the blades and thus increase their service life.

These days, rotor blades for wind turbines are largely made by hand from thermosetting resin systems. These, however, don’t permit melting, and they aren’t suitable for material recycling. At best, granulated thermoset plastic waste is recycled as filler in simple applications, according to the researchers.

“In the WALiD project, we’re pursuing a completely new blade design. We’re switching the material class and using thermoplastics in rotor blades for the first time. These are meltable plastics that we can process efficiently in automated production facilities,” said Florian Rapp, the project coordinator at Fraunhofer ICT. The goal is to separate the glass and carbon fibers and to reuse the thermoplastic matrix material.

For the outer shell of the rotor blade, as well as for segments of the inner supporting structure, the project partners use sandwich materials made from thermoplastic foams and fiber-reinforced plastics. In general, carbon-fiber-reinforced thermoplastics are used for the areas of the rotor blade that bear the greatest load, while glass fibers reinforce the less stressed areas. For the sandwich core, Rapp and his team are developing thermoplastic foams that are bonded with cover layers made of fiber-reinforced thermoplastics in sandwich design. This combination improves the mechanical strength, efficiency, durability and longevity of the rotor blade.

“We’re breaking new ground with our thermoplastic foams,” said Rapp.

The researchers will be presenting a miniature wind turbine made from the new foams and composites at the K 2016 trade fair in Düsseldorf from October 19 to 26.