Polymer derived ceramic coatings on carbon fibers for interface customization of thixoforged aluminium matrix composites (Cf/Al-MMCs)

• Applicants: Professor Dr. Frank Kern; Professor Dr.-Ing. Mathias Liewald; Professor Ralf Riedel
• Subject Area: Coating and Surface Technology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 518575506

The aluminum carbide formation at the fiber-matrix interface and the associated reduction of longitudinal strength is a major technical problem of the production of carbon fiber reinforced aluminum (Cf/Al). Carbide formation can be reduced, for example, by reducing the forming temperature, using suitable matrix alloys or conditioning the interface by deposition of fiber coatings. In this project, the production of Cf/Al prepregs by thermal spraying of aluminum on coated fibers and their manufacturing via semi-solid forming technology at reduced process temperature is to be pursued. Through the deposition of ceramic protective layers, which are applied to fiber strands by continuous liquid phase coating (CLPC process) based on preceramic precursors, the fiber-matrix interface shall be optimized especially for fiber-reinforced light metals. The fiber coating is intended to improve the adhesion of the matrix material to the reinforcing fibers, which leads to a better stress transfer between matrix and fibers. For this purpose, the functional layer must influence the wetting behavior of the metal on the fiber during the production process of the composite, prevent chemical reactions such as possible carbide formation and ensure the thermal resistance of the fibers, both during production and later use of the composite material. PAN-based carbon fibers will be investigated as fiber reinforcement. The approach of using economically viable fiber types, which are tailored for a metallic composite material through an – in comparison with state-of-the-art coating technologies - inexpensive fiber coating, offers great potential for reinforcement of composite materials. The aim of the research project is to gain a fundamental understanding of carbide formation in C/Al and its influence on the failure behavior of the composite. For this purpose, a correlation of the process parameters of the CLPC process and the semi-solid forming process as well as the micro- and macromechanical properties of the composite will be developed. Based on the results, a model-based description of the fiber-matrix interface and the fiber-matrix connection as a function of the process parameters is planned. The investigations serve to establish a suitable process field for the production of carbon fiber reinforced aluminum with optimal interface adjustment and quasi-ductile failure behavior.

• DFG Programme: Research Grants