Numerical and experimental investigation of inertia amplified dual helix metamaterial beam with low frequency flexural wave band gaps

Spiral structures are widely observed in natural systems, from the galaxy and the seashell to the DNA structures, which inspired intelligence structures with high-performance static/dynamic properties. In this paper, we proposed a novel antisymmetric dual helix metamaterial inspired by the natural helix structures and focused on its flexural wave propagations. Two kinds of elastic metamaterials with different unit micro-structures, namely, dual helix metamaterial beam (HMB) and dual helix metamaterial beam with inertia amplification (HMBI), were designed. One-dimensional refined finite elements based on the Carrera Unified Formulation (CUF) were developed to analyze the dual helix metamaterials with complex spatial geometry. Using CUF models, the flexural wave propagations of the two metamaterials (i.e., HMB and HMBI) were investigated. The commercial software COMSOL Multiphysics® 6.1 was used to verify the results based on CUF. Finally, the experiment validated the vibrational response of dual helix metamaterials from CUF and COMSOL. The results show that the consistency between the three methods is significant. It should be emphasized that the first band gap frequency result calculated by CUF is closer to the experimental result than that estimated by COMSOL. The results also show that HMBI has a lower frequency band gap than HMB. The findings in this paper provide an adequate basis for using CUF to investigate the elastic wave propagations of helix metamaterials with complex geometry.