New technology for developing carbon fiber composite aluminum lightweight materials in Germany

Based on the concept of popular lightweight construction, connectors made of lightweight metal and fiber composites represent the ideal combination of materials. However, since the two materials exhibit different electrochemical potentials, there is a risk of contact corrosion in the composite. In the DFG research project, the Fraunhofer Institute for Advanced Materials and Manufacturing Technology in Germany collaborated with the German Fassel Institute to develop a series of new technologies for joining aluminum and carbon fiber materials. By adding a temperature-resistant protective layer to the carbon fiber composite member, it is possible to prevent the occurrence of electrochemical corrosion in the composite material. At the same time, this protective layer also ensures a strong connection.

The combination of fiber composites and lightweight materials presents new challenges to all existing joining technologies. In addition to the need to maintain a high joint strength, the joint itself should not add any extra weight, both materials must prevent contact corrosion. In addition to the combined connection of bonding or riveting, the hybrid high pressure die casting proposed herein provides a new way to reduce weight while permanently preventing contact corrosion problems.

In the newly developed process, the carbon fiber material structure was coated with high temperature stable plastic (PEEK) prior to casting, and PEEK began to decompose significantly until it reached a temperature of approximately 550 °C. In a subsequent casting process step, the carbon fiber composite component is placed in a high pressure casting mold and aluminum is cast in the plastic zone at a temperature of about 700 °C. Despite the temperature differences, plastics can be integrated into the high pressure casting process without compromising the performance of the plastic by selecting the appropriate process and material parameters. Therefore, a stable connection between the two materials is established during the initial period of casting the aluminum part. Therefore, no time consuming processing steps or pre-treatment of the joint surfaces are required. In order to further increase the strength, the slit can be selectively produced in the joint region. This process achieves a joint strength of 20 MPa compared to the structure to which the adhesive is attached.

In many areas, such as automotive, aerospace, wind and sports equipment, as well as traditional mechanical structures, the demand for mixed materials is high. For large-volume production, high-efficiency serial manufacturing is required.

To meet these needs, the development team selected a large installed rack from the aircraft manufacturing for feasibility studies. The goal of the development team is to further develop hybrid casting technology based on this component, providing a new process window for aluminum high pressure casting, in order to achieve a large number of hybrid connections between carbon fiber composites and aluminum for serial production.

For the research in the field of mixed casting, the Fraunhofer Institute of Advanced Materials and Manufacturing Technology in Germany studies all two high-pressure casting equipment as well as industrial-scale production-scale peripheral equipment. With these facilities, the Fraunhofer Institute for Advanced Materials and Manufacturing Technology will be the largest off-campus research institution in the field of foundry technology in Germany. Article Source: