Mechanical and microstructural characterization of aluminium micro-pins realized by cold metal transfer

Abstract Advanced and reliable joining technologies for ultra-light weight structures combining aluminium with carbon fibre reinforced plastics (CFRP) are of great interest for aerospace industries. The combination of superior mechanical properties and low density offer a wide range of possible application. The European collaborative research project ADALFIC (Advanced Aluminium Fittings in CFRP tubes) focuses on the design, analysis, manufacturing and testing of ultra-lightweight CFRP tubes with integrated aluminium end fittings. These aluminium end fittings are equipped with very small, minimum-mass, spike-head pins realized by Fronius' cold-metal-transfer (CMT) Print welding technology. These pins are optimized for form-locked joints between aluminium and CFRP components. In this work the aluminium pins are characterized on a macroscopic and microscopic level using light optical microscopy and hardness testing. To evaluate the behavior of the pins under mode II load conditions a new shear testing method for pins was developed and implemented. With this test equipment the maximum shear force and ultimate shear strength of individual pins was measured at different temperatures and heat treatment conditions. The failure modes and fracture surfaces were analyzed via scanning electron microscopy. The results demonstrate that CMT aluminium pins are a viable, flexible and lightweight option for form-locked aluminium-CFRP joints.