Fraunhofer IWS

Pre-treatment-free coatable demonstrator of a rotor blade shell segment protected by the PeelPlas release film. Photo Credit, all images: Fraunhofer IFAM Within the joint project OptiBlade, researchers at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM (Fraunhofer IFAM, Germany), in collaboration with Olin Blue Cube Germany and Infiana Germany, have pioneered a release agent-free process and material systems that have the potential to transform rotor blade production for wind turbines. This development is poised to propel the expansion of wind turbines in alignment with the Energy Concept 2050. As part of this project, Fraunhofer IFAM initiated the operation of a state-of-the-art low-pressure plasma plant tailored for web material and devised plasma processes capable of applying an ultrathin plasma polymeric release layer to polymer film half-tubes up to 2.4 meters wide. The resulting flexible and stretch-formable PeelPlas release film, an evolution of the Fraunhofer IFAM FlexPlas release film, expands to a width of up to 4.8 meters when unfolded. Moreover, this release film can be seamlessly welded for even wider molds used in fiber-reinforced plastic (FRP) rotor blade production without any complications. Furthermore, through a specialized process, a 4.2-meter PeelPlas release film half-tube was applied onto an 18-meter segment mold at Fraunhofer IWES, in cooperation with Olin Blue Cube Germany, creating a 40-meter-long FRP rotor blade demonstrator. The plasma-coated PeelPlas release film facilitated transfer-free demolding of the large FRP component, eliminating the need for traditional release agents. Subsequently, the epoxy resin matrix of the component was coated with a repair coating for rotor blades without additional pre-treatment, showcasing optimal adhesion even after exposure to a condensation water test for 1,000 hours. The flexible vacuum stretch-formed PeelPlas release film fits like a second skin into the 18-meter-long rotor blade segment mold and enables release agent-free demolding of the large FRP component after production. The Plasma Technology and Surfaces experts and Automation and Production Technology experts at Fraunhofer IFAM developed the plasma-coated flexible PeelPlas release film based on a thermoplastic elastomer. This release film, tailored to specific industry and customer requirements, substitutes conventional release agents, ensuring carryover-free and reliable component demolding, thereby ensuring consistently high component quality for contamination-free, large FRP components. The processes developed by Fraunhofer IFAM under OptiBlade using the PeelPlas release film are reported to significantly enhance value addition throughout the process chain. Notably, these innovations optimize rotor blade surface quality, eliminate labor- and time-intensive manual tasks in tool molds and reduce mold loading time, thereby extending mold service life. The successful culmination of the OptiBlade project’s first phase has spurred plans for a new plasma-coated multilayer film under the “Sustainable and efficient rotor blade production with emission-reduced processes for the formation of surfaces” (NEOFOIL) cooperation project as part of the 7th Energy Research Program of the German Federal Ministry for Economic Affairs and Climate Action (BMWK). This new film aims to serve as a semi-permanent release film affixed to molds, enabling multiple demoldings of FRP components, thereby reducing waste and optimizing work requirements and mold occupation time. Moreover, the knowledge and technologies derived from OptiBlade are poised for transfer to diverse industries such as aircraft, spacecraft, rail vehicle, commercial vehicle, automotive, shipbuilding and sports equipment manufacturing, promising increased efficiency in their production processes. Following a duration of more than four years, the first phase of the sub-project “Release film technology for optimized rotor blade production” under the OptiBlade joint project has concluded, with gratitude extended by Fraunhofer IFAM to the project partners and funders for their invaluable support.

In February, thermoplastic honeycomb core producer ThermHex Waben GmbH (Halle, Germany), a licensee of EconCore (Leuven, Belgium), announced a €1 million capital increase and plans for process optimization and production expansion; in June, the company announced 12% growth in turnover over the past business year, as well as increased efforts toward quality certification. ThermHex credits much of last year’s growth to the success of its Organosandwich semi-finished product, launched in 2019, which combines a polypropylene (PP) honeycomb core with glass fiber/PP skins. ThermHex’s Organosandwich panels are currently used by customers in the automotive industry, for applications such as the trunk floor of the 2020 Hyundai Creta. According to ThermHex, advantages of Organosandwich include high stiffness and strength, reduced weight and costs, reduced raw material usage, recyclability, short cycle times and the ability to use with injection molding. The company’s PP honeycomb cores are also used in vehicle roofs for Volkswagen and Ford, motorhome components, swimming pools and doors. ThermHex’s polypropylene honeycomb core is sandwiched between glass mat thermoplastic (GMT) skins for the trunk floor of the 2020 Hyundai Creta. The floor panels are manufactured in a one-step compression molding process and include a finished edge closure and hinge. The company is now working with the Fraunhofer Institute for Microstructure of Materials and Systems (Fraunhofer IMWS, Halle) on technology for production of hybrid sandwich components based on Organosandwich semi-finished products via forming and injection molding. According to ThermHex, the technology will enable mass production of functionalized parts with very short cycle times. According to Mona Boche-Würfel, marketing and communications manager at ThermHex, the company is targeting sales of 1 million kilograms of PP honeycomb cores and Organosandwich this year, and yearly growth of 10-20% over the next few years. This finished demonstrator panel was built using ThermHex and Fraunhofer IMWS’ automated production process. Additional R&D projects for ThermHex include work funded by BMWi to develop honeycomb cores specific to aerospace applications, production of hierarchical sandwich honeycomb cores for higher load-bearing applications and development with automotive partners Daimler Truck AG (Stuttgart, Germany) and Elring Klinger (Stuttgart) of a hybrid sandwich material consisting of PP honeycomb core and a metallic outer layer. ThermHex says it is also working with AZL Aachen (Germany) on the development of a production line for injection molded sandwich panels. Recycled PET and high-performance thermoplastic honeycombs In addition, ThermHex’s parent company, EconCore, has also recently invested in large-scale production line development. The company says it has been seeing increased market demand for more sustainable materials and a shift in focus toward thermoplastic solutions for high-end aerospace and automotive applications. The thermoplastic honeycomb cores that EconCore and its licensees produce are already said to be recyclable, and in the case of ThermHex, produced with green power, leading to reduced carbon emissions. “Lightweighting, strength, stiffness, resistance to chemicals and moisture: These are properties that are needed more today than ever. Together with our customers, we develop new ideas for old and new applications that drive growth while reducing CO2 emissions,” says Dr. Jochen Pflug, CEO of ThermHex. An illustration of EconCore’s automated, continuous production process, which will be used to produce rPET and HPT materials as well as ThermHex’s Organosandwich products. The continuous production line enables core and skins to be layered via an automated assembly line (pictured), which is followed by infrared (IR) preheating, transfer into a mold for forming or injection molding and then demolding. In an effort to increase its sustainability goals further, EconCore is progressing its technology for producing recycled PET (rPET) and high-performance thermoplastic (HPT) honeycombs, focusing similarly on cost-efficient and continuous production of sandwich panels for each of these technologies. Currently, the company is producing rPET at a prototype- or lab-scale, with plans to produce the material commercially by the end of 2022. EconCore’s current technology processes PP granulates to produce an easily recyclable core product. The next generation of this technology will process rPET flakes for an even greener solution, while still exhibiting high mechanical properties and high temperature stability. EconCore sees increased opportunities on the horizon for rPET in the automotive market in particular, and says that the use of rPET honeycomb cores provides a sustainable solution with good life cycle assessment and a low carbon footprint.