Vibration damping and cyclic loading behavior of aluminium foam filled tubes

Among the scientific and industrial realities, metal foams are unanimously considered as interesting and competitive materials. Indeed, thanks to their porous structure, these innovative materials can boast of having very interesting mechanical and physical properties compared to bulk materials. Foam filling of hollow structures is a clever solution that confers improvements both in stiffness to weight ratio and absorption of energy to the host material, so that automotive and aerospace industry are progressively making use of this solution. The principal aim of this work is investigating on the damping properties and the cyclic loading behavior of foam filled titanium tubes. In order to determine the influence of these factors in damping capacity, tubes with two level of density in foam and two kind of interface (natural and bonded) between tube and foam will be studied. A modal analysis due to impact excitation will be performed on each tube, mainly to investigate the damping. Furthermore, displacement, energy and acoustic emission (AE) evolution during cyclic bending loading will be monitored and investigated. Finally, a comparison between the two kind of interfaces in both the damping and fatigue behavior will be proposed. In addition to this, a vibration test will be designed and performed on foam filled steel tubes, in order to question the damping capacity of foam filling at 30 Hz. A structure designed to vibrate at this frequency will be excited and the damping computed through a modal analysis. This topic has been pushed by the interest of Bell Textron Canada in making use of foam-filled tubes as structural components in helicopters whose rotor excitations’ frequency are indeed close to 30 Hz. By the way, the whole study has been developed in partnership between Politecnico di Milano, MUSP laboratory of Piacenza and ÉTS (École de technologie Superiéure) of Montréal.