Composite materials are recognized as difficult to connect materials, and researchers are currently focusing on mechanical connection technologies such as crimping, bonding, riveting, or screwing. From November 6th to 8th this year, the European Composites Exhibition in Stuttgart, Germany also announced that it will focus on showing the advantages and disadvantages of each joining process.
Because each connection process is different, the factors considered are also different. For example, during the riveting process, the fiber layer was damaged in layers during trial drilling. Drilling can also weaken components. In addition, the strength transfer between the parts to be connected is very limited locally. In addition, the gap width also causes various problems in the adhesive member. However, because the strength transfer of fiber composites is evenly distributed, riveting is a standard process for connecting fiber composites, so that the material properties can be used to the maximum. RWTH Aachen's Institute for Welding and Connection Technology (ISF), Oxford Advanced Surfaces and Weiss Chemie Technik, the three major exhibitors will showcase their respective processes at the European Composites Exhibition.
BMW focuses on bonding technology for electric vehicles
BMW will completely use bonding technology to make carbon fiber reinforced plastic (CFRP) bodies for its i3 and i8 electric vehicles. This method avoids mechanical damage to the carbon fiber parts, thereby improving the stability of the parts and saving costs.
The adhesion of the glue is determined by the surface initiator. The priming effect varies depending on the matrix and the fibers used. In addition, process parameters and materials can also affect the bonding quality and durability of the bonded connection. In view of this complexity, the research and evaluation of the process and new technologies of combining fiber composites and other mixtures will be the focus of many scientific studies.
Hot connection
Researchers at Karlsruhe Institute of Technology (KIT) have developed a novel, robust and low-cost bonding technology for structural parts. This hybrid process combines inorganic and organic adhesive layers, thus greatly reducing costs and increasing abrasion resistance. Therefore, this connection technology is particularly suitable for connecting structural components, such as applications in wind power generation, construction and other fields. Can also be applied to the fields of automotive and mechanical engineering.
The Fraunhofer Institute for Materials and Beam Technology (IWS) in Dresden has developed the Heat Press Cool-Integrative (HPCI) process, which is expected to completely replace the bonding process. This thermal direct joining process presses the laser-textured metal together with the thermoplastic part and applies local heating. After the thermoplastic melts, it will penetrate the texture and attach to the surface for connection. Researchers have also developed a glue gun for this purpose, which can produce strong connectivity in seconds.
Contactless connection of fiber laser
In order to connect fiber-reinforced thermoplastics (organic sheets) with metals, the IWS Institute has also proposed a slot-web guideline. Organic flakes are used as webs, metal plates are used as slot plates, and fiber lasers are used for bonding. This process can very effectively adjust the heat input, and it can also accurately heat the web-non-contact part of the fiber-reinforced mesh. At the same time, the process can also use the 2D high-frequency beam deflection of the scanner lens to make the plastic uniformly heated.
The Fraunhofer Institute of Manufacturing Engineering and Applied Materials (IFAM) collaborated with CFK-Valley Stade to develop an automated bonding test line for aircraft structural fiber composite panels. This process is more cost-effective than traditional methods and is suitable for all industries that require lightweight, dimensionally stable, and low-cost components.
The combination of 3D printing and organic plates
Through this initiative, project partners have fully implemented automated fill connections, replacing the current manual framework connections. For mass production in the future, they also provided the required driving intelligence. With the help of this decentralized concept, a large number of drives can be concentrated in a small footprint, and adjusted and effectively controlled in a modular manner with very little wiring.
In the LightFlex project, scientists from the Fraunhofer Institute of Production Technology (IPT) in Aachen focused their research on the combination of 3D printing and unidirectional semi-finished organic flakes. In order to optimize the carrying capacity, 3D printed parts are combined with fiber composite parts. To this end, they will use near-net-shape technology to produce custom organic sheets on a line called PrePro. Considering the high energy consumption involved in carbon fiber production, this method can minimize the loss of materials and greatly save production costs.