No contact corrosion occurs
Based on the popular concept of lightweight construction, connectors made of lightweight metal and fiber composites represent an ideal combination of materials. However, since the two materials exhibit different electrochemical potentials, there is a danger of contact corrosion in the composite. In the DFG research project, Fraunhofer IFAM (Fraunhofer Institute · Institute of Advanced Materials and Manufacturing Technology) and Faserinstitut Bremen eV (Bremen eV) New technology for carbon fiber materials. By adding a temperature-resistant protective layer on the carbon fiber composite material member, the occurrence of electrochemical corrosion in the composite material can be prevented. At the same time, this protective layer also ensures a strong connection.
The combination of fiber composites and lightweight materials poses new challenges to all existing connection technologies. In addition to the need to maintain high connection strength, the connection itself should not add any additional weight. Both materials must prevent contact corrosion. In addition to the combined connection method of bonding or riveting, the hybrid high-pressure die casting proposed here provides a new method to reduce weight while permanently preventing the problem of contact corrosion.
Connect the components in just a few steps
In the newly developed process, before pouring, the carbon fiber structure is coated with high temperature stable plastic (PEEK), and PEEK does not begin to decompose significantly until it reaches a temperature of about 550 ° C. In the subsequent casting process steps, the carbon fiber composite material component is put into a high-pressure casting mold, and aluminum is cast in a plastic region at a temperature of about 700 ° C. Despite the temperature differences, choosing the right process and material parameters, plastics can be integrated into high pressure casting processes without affecting the performance of the plastic. As a result, a stable connection is established between the two materials during the initial period by casting the aluminum part. Therefore, no time-consuming processing steps or pretreatment of the bonding surface are required. In order to further increase the strength, a cut can be selectively made in the joint area. Compared with the structure of the adhesive connection, the connection strength obtained by this process is 20 MPa.
Development of serial production
In many fields such as automotive, aerospace, wind energy, and sports equipment, as well as traditional mechanical structures, demand for hybrid materials is high. For large-volume production, high-efficiency serial manufacturing is required.
To meet these needs, a large number of mounted brackets were selected from the aircraft manufacturing for feasibility studies. The goal of the development team is to further develop the hybrid casting technology based on this component, in order to provide a new process window for aluminum high pressure casting, so that the hybrid connection between carbon fiber composite materials and aluminum can be realized in large quantities. Achieve serial production.
For research in the field of mixed casting, Fraunhofer IFAM has two high-pressure casting equipment (Bühler, SC N / 66 type, 660t closing force; Frech, DAK250 type, 290t closing force) and industrial series production-scale peripheral equipment. With these facilities, Fraunhofer IFAM claims to be the largest off-campus research institute in the German foundry technology sector.