Numerical and experimental characterization of damping properties of SMA composite beam for vibration control systems

Shape memory alloys (SMAs) are very interesting smart materials due to their significant damping properties during transformation phase and especially in the martensitic phase. The combination of these properties of SMAs with the mechanical properties and the light weight of glass fiber reinforced polymer (GFRP) is a promising aspect in order to produce an innovative composite material for vibration control in structural applications.

A SMA sheet, after to be laser patterned with different geometries, was introduced in a laminated composite between a thick GFRP core and two thin outer layers with the aim of enhancing the damping capacity of a GFRP beam through passive vibration suppression. The selected SMA was a Cu-Zn-Al alloy sheet, obtained from an induction melted ingot, further hot and cold rolled down to 0.2 mm thickness. The choice of a copper alloy is related to some advantages in comparison with Ni-Ti-Cu SMA, which was tested for the presented application in a previous work: lower cost, higher storage modulus and consequently higher damping properties.

The patterning of the SMA sheets was performed by means of a pulsed fiber laser, commonly used for micromachining. After the laser processing, the SMA sheets were heat treated in order to obtain the desired shape memory properties. The transformation temperatures were measured by differential scanning calorimetry (DSC). The damping properties were determined at room temperature on full scale sheet, using a universal testing machine (MTS), with cyclic tensile tests at different deformation amplitudes as well as in function of temperature on miniature samples with a dynamical mechanical analyser (DMA) at different deformation amplitudes and frequencies.