Orbital Ultrasonic Welding of Ti-Fittings to CFRP-Tubes

Abstract

Hybrid structures are important for the automotive and aeronautical industry as they have the potential to reduce vehicle or aircraft weight and to improve fuel efficiency. Continuous ultrasonic metal welding is a promising technique for hydraulic applications in aircraft to realise tubular metal/fiber reinforced polymer (FRP) hybrids. Fluid proof connections between dissimilar components can be joined by continuous welding seams. Tubular metal/FRP hybrids, produced by a new advanced variant of ultrasonic metal welding, are investigated as a potential substitute for metallic hydraulic tubes. The oscillating welding system moves around the tubular joining partners to generate a sealed orbital connection. Homogeneous joint quality is required to assure the requested component strength. Therefore, the amplitude of sonotrode displacement and the welding force are controlled to keep the induced welding energy constant and the joint quality uniform. High mechanical strength is required for a safe application in the 5000 psi hydraulic system of current and future aircraft concepts. For this study metal injection molded (MIM) titanium fittings (TiAl6V4) and carbon fiber reinforced PEEK (CF-PEEK) tubes were investigated. Process parameters for metal/FRP hybrid joining were evaluated considering their mechanical and technological properties, as well as the microstructure of the hybrid interfacial area. The entire joining area of tubular joining partners has to be in close contact before welding to assure a continuous tight joint. Hence, the titanium fitting is thermally shrunk onto the CFRP tube before ultrasonic welding. The presented orbital ultrasonic welding technology was developed for prospective industrial use and future applications of ultrasonically welded tubular multi-material-components.