Locally resonant metamaterials damped by particles embedded through additive manufacturing

Damping properties in elastic metamaterials are essential for enhancing vibration suppression within frequency ranges known as bandgaps. However, fabricating metamaterials with high-damping materials through additive manufacturing presents challenges, limiting the design freedom of metamaterials. This study proposes locally resonant metamaterials damped by particles, embedded using powder bed fusion of metals with a laser beam. Particles that remain unfused in the powder bed fusion process are retained as particle dampers, adding damping through friction and collisions between particles. Unlike traditional viscoelastic damping materials, metal particles offer advantages in terms of thermal durability. To investigate the damping effect on wave propagation within the metamaterials, we identified the frequency- and acceleration-dependent damping properties of the particle dampers through vibration testing. These properties were then used to define analytical models for the interaction between the metamaterials and the transition of damping via dispersion analysis. The dispersion analysis indicates that wave attenuation occurs over wider frequency ranges. Additionally, the vibration suppression capability of the proposed metamaterials was experimentally demonstrated through vibration testing of fabricated specimens, resulting in the suppression of vibration responses in the out-of-band gaps frequencies by more than 10 dB. The findings of this study enable the fabrication of elastic metamaterials with damping properties via additive manufacturing, offering a method to suppress vibrations across a wide range of frequencies.