Abstract
In this study, we aimed to form band gaps in a periodically aligned beam consisting of two different internal structures with a single metallic material. First, dispersion analysis was carried out to investigate the bandgap frequency changes and the bandwidth when the composite beam's cross-sectional properties and the unit cell's length were varied. Then a composite beam having the first bandgap of less than 1 kHz with considerable frequency bandwidth was designed. The numerical parameter studies by changing the combinations of the cross-sectional properties showed that the bandwidth of the first bandgap becomes wider according to the physical difference of the unit cell. In addition, investigations of composite beams by changing the length of the unit cell showed a trend that the bandgap frequency shifts toward lower, and the bandwidth becomes smaller as the cell length is increased. Frequency response analyses using a finite element software Ansys for the above-designed composite beam were also carried out with different numbers of the unit cell, and the numerical results confirmed the formation of a bandgap as predicted by the dispersion analysis regardless of the unit cell numbers. Moreover, composite beams, having cross-sectional properties and length of the unit cell corresponding to the numerical studies, with different cell numbers were fabricated using a metal 3D printer. Vibration measurement tests were conducted, and the numerically predicted bandgap formation was demonstrated.
