NUMERICAL MODELLING OF LATTICE-CORE SANDWICH METASTRUCTURES WITH QUASI-ZERO-STIFFNESS RESONATORS

Lattice-core sandwich structures are advanced lightweight structures, but they are vulnerable to low-frequency vibrations. Acoustic metamaterial provides a new solution for low-frequency vibration control in lattice-core sandwich structures. However, low-frequency bandgaps are usually obtained by attaching heavy local resonators, which in turn increases the weight of the whole structure. To achieve broadband low-frequency bandgaps in lattice-core sandwich structures with limited additional masses, a novel methodology is proposed in this work, which is achieved by periodically attaching quasi-zero-stiffness (QZS) resonators in the lattice core, which neither hinders the lightweight property of the structure nor occupies additional space. The configuration of QZS resonator consists of folded beams in parallel with tilted beams, where the titled beams act as negative-stiffness elements to partially counteract the positive stiffness of folded beams. The QZS feature is achieved by applying a proper pre-compression displacement to the beams. Numerical simulations based on band structure calculation indicate that the proposed structure can achieve a bandgap in a lower frequency zone compared with that achieved with non-compressed resonators. Moreover, the vibration transmissibility of a finite-length metamaterial beam is analysed using finite element simulations, which confirms the wave attenuation effect.