Recent Developments for Laser Beam Joining of CFRP-aluminum Structures

Abstract

Modern lightweight structures including dissimilar materials allow an improvement of the weight-specific properties. However, novel joining concepts are necessary to exploit the potential and to enable efficient manufacturing. The DFG research group “Schwarz-Silber” (FOR1224) aims to develop and investigate transition structures for advanced CFRP-aluminum connections. In five interdisciplinary projects novel concepts are under development considering textile, welding, brazing and casting techniques. Within their work the research group focuses on three approaches realizing the transition: the usage of wires (titanium), foils (titanium) and fibers (glass fiber) as transition elements between CFRP and aluminum. The “wire concept” represents a parallel arrangement of miniaturized loop connections. Carbon fibers are threaded through titanium wire loops which are joined to an aluminum component by a combined laser welding-brazing process. The “foil concept” is based on titanium laminates. This concept is characterized by joining a Ti-CFRP laminate to an aluminum sheet. This hybrid laminate, in which CFRP-layers alternate with titanium foils, has been fabricated. The titanium side of the laminate is joined to the aluminum sheet. In this paper, the joint configurations based on titanium wires and foils are presented. First specimens are discussed with respect to their properties. It is shown that the novel approaches are principally suitable to produce advanced CFRP-aluminum structures by using laser beam processes.