Abstract
A one-dimensional mechanical lattice system with local resonators is proposed as an elastic metamaterial model, which shows negative mass and negative modulus under specific frequency ranges. The proposed representative units, consisting of accurately arranged rigid components, can generate controllable translational resonance and achieve negative mass and negative modulus by adjusting the local structural parameters. A shape memory polymer is adopted as a spring component, whose Young’s modulus is obviously affected by temperature, and the proposed metamaterials’ tunable ability is achieved by adjusting temperature. The effect of the shape memory polymer’s stiffness variation on the band gaps is investigated detailedly, and the special phenomenon of intersecting dispersion curves is discussed, which can be designed and controlled by adjusting temperature. The dispersion relationship of the continuum metamaterial model affected by temperature is obtained, which shows great tunable ability to manipulate wave propagation.
Highlights
As significant advances in advanced materials and engineering structures, periodic structures, such as phononic crystals (PCs) and metamaterials[1], have drawn more and more attention to applications in manipulating wave propagation and noise reduction. Advantages of these materials/structures come from their special properties, such as effective negative mass/elastic modulus and negative refraction[2,3,4,5], which cannot be found in the natural world
A structure with multiple frequency band gaps is designed in this work, and a shape memory polymer[33] material is used in this structure
The results of η = 0.5, 1, and 3 are compared, a band gap disappears in the case of η = 1, which means that the on/off of this band gap can be controlled by adjusting the stiffness ratio η, and it is of great value in manipulating elastic wave propagation
Summary
As significant advances in advanced materials and engineering structures, periodic structures, such as phononic crystals (PCs) and metamaterials[1], have drawn more and more attention to applications in manipulating wave propagation and noise reduction. Researchers have designed different structures to generate multiple frequency band gaps and widen band gaps to improve acoustic materials’ vibration isolation and noise reduction capabilities. To broaden band gaps further and satisfy vibration isolation in a different frequency environment, researchers seek to improve vibration isolation capabilities by introducing tunable metamaterials, which can adjust band gaps with the change of noise frequency Many mechanisms, such as circuit control[26], magneto fluid[27,28], and structural deformation[29], are introduced to realize adjusting resonance frequency of local resonators, which results in tunable band gaps when subjected to different external environments. A structure with multiple frequency band gaps is designed in this work, and a shape memory polymer[33] material is used in this structure The modulus of this material will decrease with temperature increasing in a specific range.
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