Modelling and simulation of a novel nitinol-aluminium composite beam to achieve high damping capacity

Alloys demonstrating non-linear hyperelastic hysteretic behaviour, such as Nitinol, attract a lot of attention in the aerospace and other industries due to their high damping capacity. To overcome limitations due to the high cost and density of Nitinol, we explore its use in combination with aluminium alloys to produce an affordable lightweight composite structure with high damping capacity. The challenge is that Nitinol should operate in its hyperelastic range at strains well over the yield point of aluminium, often at large vibration amplitudes, while aluminium should remain well below its elastic limit. To overcome this limitation, this paper proposes a novel beam topology with two Nitinol skins connected with transversal strips made from aluminium alloy, which acts as a lightweight core to the composite structure. A numerical parametric study is conducted to estimate the stiffness, load capacity and loss factor of the material with varying design parameters, including the thickness of the skins and that of the core. Analytical models are also developed as a preliminary design guideline from the fundamental principles of the theory of bending, based on which non-dimensional design parameters are established, and their results are compared. From the study, it is shown that at specific configurations of the design parameters, there is a potential to achieve not only high damping capacity at the skins even at small vibration amplitudes while keeping the core in its elastic region, but also high system stiffness at the same time.