Special Topic: Welded Metal/CFRP‐Structures

Abstract

In autumn 2004 the research unit for 524 entitled “Joining, properties, and simulation of welded metal/CFRP lightweight structures” was established by the German Research Foundation (DFG) to enable alternative joining methods for future multi-material design concepts by understanding the basics of mechanical and microstructural performance. In this joint research different aluminum alloys, steels, and carbon fiber reinforced thermoplastic composites were studied. To realize metal to composite joints three different welding techniques were investigated: ultrasonic welding, induction welding, and thermal impact welding. Different characterization and experimental techniques were combined in order to establish a thorough understanding of the microstructure–property relationships in welded hybrid joints. Their mechanical, physical, and technological properties were investigated with respect to the specific characteristics of the different joining zones by high resolution microscopy and surface analysis. The results provide essential input parameters for modeling and simulation of the welding processes themselves as well as the mechanical behavior of metal/CFRP-structures. By the crosslink of experiment, modeling, and simulation microstructure-based as well as property-based models were developed for prediction of the performance of future multi-material components. Finally the synergy of all FOR 524 projects led from a scientific view on coupon level to advanced welded hybrid structures. A closed hybrid Al/CFRP demonstrator shows the potential of the alternative joining techniques for future applications in structural automotive and aircraft design concepts. Parts of the results were presented during the FOR 524 colloquium at the University of Kaiserslautern in summer 2012 as well as during an international symposium at the TMS 2013 annual meeting in San Antonio (TX, USA). This issue of Advanced Engineering Materials presents full papers, which address different aspects relevant for welded metal/CFRP-joints. Two reviews on ultrasonic and induction welding provide a basic overview about alternative joining techniques for dissimilar materials, especially of metals to thermoplastics. Further communications cover all remaining aspects of the research unit 524: Joining, properties, and simulation of welded metal/CFRP-structures. Finally we would like to thank DFG, in particular Dr. Xenia Molodova and Dr. Burkhard Jahnen, for their on-going interest and financial support of our work. Without the financial support of DFG these unique joint research projects would not have been possible. Last but not least we hope that the selected contributions will stimulate future research activities and we wish enjoyable reading. Frank Balle Dietmar Eifler Frank Balle and Dietmar Eifler Institute of Materials Science and Engineering (WKK) University of Kaiserslautern (Germany)