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    20/5000 Induction welding technology innovation brings thermoplastic composite aircraft a step closer
    With more than 100 years of experience in welding metals, the French Institute of Welding (IS) group IS emerging as a leader in welding thermoplastic composites. IS group has developed the "dynamic induction welding" process used to connect carbon fiber/polyether ketone (PEKK) unidirectional truss band and fuselage skin in the Aero-thermoplastic composites demonstration project at Airbus' STELIA Aerospace.Although the process was successful, the lack of sensors at the interface limited the radius properties of the bonding truss and the global heating of the panels. A sensor is a material placed between two bonded materials in a thermoplastic composite welded joint heated by an induction coil in the welded joint. The receptor may be a resistively heated conductive body or a hysteresis heated magnetic body, melting the substrate at the welding interface and pressing it together to form a welded joint with high strength. Sensors used in induction welding thermoplastic composites are initially a metal screen or mesh, sometimes impregnated with a polymer.The IS Group has formed a partnership with Thermoplastic material supplier Arkema to jointly develop and acquire a patented technology called welding Innovation Solutions.The foundation of innovative welding solutionsThe innovative welding solution is based on the use of sensors to heat the welding interface, but this is a removable sensor connected to the welding joint. The sensor allows the process to perfectly position the heated area of the weld, and the head with the sensor is mobile, so there is no residue in the interface that will not interfere with the performance of the welded structure. In the early iterations of induction welding, the metal mesh receptor remained in the weld, but this was not the desired result. Because carbon fibre in ordinary aerospace laminates is conductive, the latest technology has been able to eliminate the receptors, allowing the use of carbon fibre as a sensor.Another feature of innovative welding solutions is the use of a pure thermoplastic matrix or low fibre layering at the welding interface to increase resin fluidity. The melt temperature and viscosity of the interfacial layer can be adjusted and functionalized to provide electrical conductivity or isolation to prevent electrical corrosion, such as between carbon fiber and aluminum or steel.Results of innovative welding solutionsThe joint coefficient of the solution is 80% ~ 90%. The joint coefficient corresponds to the welding strength. It is used in metals, plastics and composites. In a single lap shear test of two pre-cured plates welded together using the solution, 80 to 90 per cent of the performance of the unwelded, hot-pressed tank cured reference plates was obtained. The trials used unidirectional strips made of carbon fiber by Hextow AS7 and Kepstan 7002 PEKK.Innovative welding solutions can be used to weld any kind of substrate: PE, PA, PEKK, PEEK, and carbon, glass, or array-fiber reinforced thermoplastic composites. Moreover, components with copper grids can be welded to protect against lightning strikes, which are key to the construction of aeronautical structures. Innovative welding solutions are designed to be fully automated, with welding heads mounted on a 6-axis robotic arm.Welding temperature controlA common problem of metal mesh sensors subjected to magnetic field is the uneven temperature distribution of welded parts. The solution controls this by using a sensor to melt the welding interface, sensing the temperature using a laser pyrometer that actually measures the sensor's edge from the side. So you know the exact temperature at the interface. Cooling methods are also used to help control the temperature and ensure that the thermoplastic material is fully crystallized throughout the welding process.Girder skin welding testAirbus's STELIA was one of the first customers for the induction welding process. The IS group and Arkema conducted a special study for STELIA in which seven carbon /PEKK beams were welded to 14 layers of skin and covered with copper mesh to prevent lightning strikes. The ultimate goal is a structure with a welding length of 30 meters and a straight and double bending cross section. Components were fabricated using a 194 GSM unidirectional band consisting of Tenax HST45 carbon fibre and Kepstan 7002 PEKK. STELIA specifies a homogeneous weld with mechanical properties greater than 85% of the reference material solidified in the thermocompression tank, without degradation of the thermal or mechanical properties of the adhesive. STELIA also requested the development of a robust process to change the thickness of the adhesive. The IS group conducted chemical and performance tests on the welded components.The IS group and Arkema were able to meet STELIA's requirements, achieving 85% greater than the single lap shear and interlaminar shear strength performance compared to the thermal tank cured reference laminates. No dispersal or degradation in component laminates or lightning resistant grids. The only downside is speed, STELIA requires welding speed of at least 1 m/min. Currently, the solution has a speed of 0.3 meters per minute. In terms of the thickness of the base material that can be welded, the typical thickness of aerospace structures can be welded and 5 mm thick parts can be welded to 5 mm substrates.Technological opportunities and challengesThe IS Group and Arkema are co-owners of innovative welding Solutions technology and have secured this technology through a reliable patent portfolio that has included five French and international patent applications. Innovative welding solutions can be used in conjunction with any thermoplastic composite substrate and IS demonstrating the technology through a programme of collaboration with European and Us companies. For Arkema, the focus is on PEKK, which has formed a strategic alliance with Hershey in 2018 to develop carbon/thermoplastic belts for future aircraft, focusing on providing customers with lower costs and faster production speeds. As part of the partnership, France will establish a joint research and development laboratory.The €13.5 million, 48-month highly automated integrated composite material project for adaptive structures is a continuation of the Strategic alliance between Arkema and Hershel. The project will optimize the design and manufacture of materials for the production of composite parts in order to achieve competitive costs. It will also develop a more productive composite placement/placement technology and a new system with online quality control to weld the final parts together. The targeted applications include the main structures of aircraft, structural components for the automotive industry and pipelines for the oil and gas industry. The recyclability and sustainability advantages offered by thermoplastic materials are also important to these markets and will be demonstrated and quantified in the project.Compared to the dynamic induction welding process in 2017, one of the benefits that the innovative welding solution can provide is a more than 50% reduction in power requirements. With conventional induction, large power is required to heat the surface, but with sensors at the interface, the surface is much smaller and requires much less energy. This also helps to prevent the beam radius from loosening, as too much heat can soften the material in the radius and allow the fibers to move. However, there are still cooling problems. For flat shapes, thermal control is very simple, but as shape complexity increases, it becomes more challenging. At present, the main objective is to continue to develop and achieve the typical scale of skin beam welding, and the emphasis is still on introducing the technology into the new aircraft development program.
    The 111m blade of 14MW fan adopts carbon glass composite main beam to reduce the cost
    In order to lay a technical foundation for the development of 11-15 MW wind turbines, German aerodyn company has preliminarily designed a 14MW wind turbine, which will adopt 111m TC1B fan blade. The main beam of the blade is made of carbon fiber and glass fiber mixed reinforced composite material, which will reduce the consumption of high cost carbon fiber to the minimum.Modern structural design concepts, coupled with aerodyn's over 30 years of experience in fan blade development, have resulted in the development of TC1B fan blades for 14 MW fans. The blade can be adjusted and optimized according to rated power, fan type, wind farm environment and other specific conditions. The blade was developed using the most advanced materials and manufacturing techniques.At a power rating of 14 MW, aerodyn's fan blades can achieve a impeller diameter of 228 m, a speed rating of 7.54 RPM, and a tip speed of 90 m/s. Meanwhile, the maximum chord length of 14MW fan blade is 7.018 m, and the tip is pre-bent 4 m. In addition, the diameter of the blade root bolt circle (the diameter of the root pitch circle) reaches 5050 mm.At present, the company is focusing on the development of 10 MW fans, which will be put into production next year. Next, more powerful turbines, about 15 MW, could be on the market around 2025. Right now, supply chains and the necessary infrastructure are the big challenges to implementing future plans.
    A new high pressure hydrogen storage system with composite material for integrated vehicle was developed in Germany
    BRYSON (Baurauffiziente HYdrogenSpeicher Optimierter Nutzbarkeit) project is funded by the Federal Ministry of Economy and Energy of Germany, meaning "a space-efficient hydrogen storage system with optimized availability". The main participants of the BRYSON project are German enterprises, including BMW AG, The Institute of Light Engineering and Polymer Technology (ILK) of Dresden Polytechnic University, Leichtbauzentrum Sachsen (LZS), the composite engineering and development company, The composite distributor WELA Handelsgesellschaft and the University of Munich Applied Sciences.The objective of the BRYSON project was to develop a new high-pressure hydrogen storage system designed to be easily integrated into a common vehicle architecture, so the project focused on building a flat design hydrogen storage system.ILK, LZS and Composite Design have worked closely with manufacturer Herone GmbH to develop a hydrogen storage system consisting of chain tubular tanks. The storage tank is made of braided fabric reinforced thermoplastic composite material. The rapid production advantage of braided and thermoplastic composite material can effectively reduce the production cost of fuel cell vehicle hydrogen storage tank and make the recovery of the tank structure easier. The design of the new hydrogen storage system not only improves the product competitiveness, but also realizes better sustainability.Alexander Rohkamm, co-founder of Herone GmbH and director of the BRYSON project, said: "The goal of the BRYSON project is to develop modular storage systems that can adapt to a given vehicle design space." The machining properties of thermoplastic composites make part design more integrated, reducing manufacturing costs and improving energy efficiency. Improves the ratio of performance to cost compared to traditional metal and thermosetting composite solutions."Alternative transport concepts also need to be rethought at every step of the development and manufacturing chain," Rohkamm points out. In the current internal combustion engine vehicle architecture, gasoline and diesel engines share the same installation space, and significant cost savings can be achieved by using the same architecture. Similarly, in order to achieve maximum flexibility and economy in future ev architectures, hydrogen storage systems can be designed in areas where high voltage batteries would otherwise be. Integrating the two types of energy (hydrogen and batteries) into the same installation space reduces costs and enables more flexible production."