Article

Hybrid elastic solids

Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Nature Material (Impact Factor: 36.43). 06/2011; 10(8):620-4. DOI: 10.1038/nmat3043
Source: PubMed

ABSTRACT Metamaterials can exhibit electromagnetic and elastic characteristics beyond those found in nature. In this work, we present a design of elastic metamaterial that exhibits multiple resonances in its building blocks. Band structure calculations show two negative dispersion bands, of which one supports only compressional waves and thereby blurs the distinction between a fluid and a solid over a finite frequency regime, whereas the other displays 'super anisotropy' in which compressional waves and shear waves can propagate only along different directions. Such unusual characteristics, well explained by the effective medium theory, have no comparable analogue in conventional solids and may lead to novel applications.

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Available from: Pai Peng, Jun 12, 2014
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    • "Meanwhile, the concept of metamaterials has been extended to acoustic and elastic media. Much effort has been focused on negative index of refraction [15] [16] [17] [18] [19], sub-wavelength imaging [20] [21], and transformation acoustic [22] [23] [24] [25] [26] [27] [28]. Recently, acoustic ZIM have also drawn intense attention and various schemes have been proposed to realize them, such as acoustic waveguides loaded with membranes and/or Helmholtz resonator [29] [30] [31], coiling up space with curled channels [32] [33], and 2D acoustic crystals with Dirac-like cones [34] [35] [36] [37]. "
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    ABSTRACT: We theoretically investigate the unusual transmission property of in-plane elastic waves through systems of isotropic elastic zero-index-metamaterials (ZIM) slab embedded with solid defects. Both double-zero-index-metamaterials (DZIM) and single-zero-index-metamaterials (SZIM) are examined. Particularly, mode conversion does not occur when either longitudinal (P) wave or transverse (S) wave is scattered by the defects in a specific type of DZIM possessing near zero reciprocal of shear modulus and near zero mass density . Thus, P wave and S wave can be controlled independently by simply adjusting the parameters of the defects to achieve high transmission (cloaking) and total reflection (blocking). And an analytic model is proposed to explain the mechanisms of the total reflection. On the other hand, enhanced transmission is observed for the SZIM systems. Our analysis shows that the enhanced transmission is due to resonant modes arisen in the defects. In addition, we suggest a two-dimensional (2D) phononic crystal (PC), which has effective double-zero-index, to provide the possibility of achieving the intriguing transmission properties experimentally.
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    • "This model provided richer applications than other model reported so far but the microstructure is more complex due to the lack of symmetry. In this letter, we follow the same concept [17] to propose an alternative design of anisotropic elastic metamaterials with simpler constituents but better functionality. Numerical method is performed to analyze the effective parameters and wave propagation characteristics through the text. "
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    ABSTRACT: In this paper, we introduce an alternative model of elastic metamaterial by following the conceptual design of hybrid elastic solid reported by Lai and colleges [17]. The proposed model is comprised of build-in resonant microstructures which are made of three kinds of conventional materials. Under specific incident frequencies, it behaves seemingly as a medium with negative mass density and elastic modulus so that a few novel wave propagation properties can be observed. We utilize finite element simulation to analyze the effective material parameters as well as the wave transmission properties. Comparing to the literatures, the proposed model appears larger band of practical application, and furthermore the required material is reduced which may be more easy to fabricate.
    Procedia Engineering 12/2014; 79. DOI:10.1016/j.proeng.2014.06.389
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    ABSTRACT: We firstly present a kind of acoustic metamaterial (AM) with resonant microstructure of double split hollow sphere (DSHS). Simulation and experimental results show that the DSHS AM has a transmission dip and accompanied phase advance near the resonant frequency. Effective properties extracted by homogenized-media theory show that the negative modulus of the DSHS AM occurs near the dip frequency. With the increase of the diameter of the double holes in the DSHS, the resonant intensity will be stronger which leads to a greater negative modulus. By adjusting the double holes of DSHS structure with different diameter or angle, the negative-modulus band of the AMs with the modified unit cells will become tunable. Furthermore, we extend the DSHS AMs to the AMs with multi-split hollow sphere (MSHS), which still possess the property of negative modulus. This concept may pave a theoretical way to study the micro-sized and nano-sized MSHS AMs fabricated by chemical manufacturing techniques, which have potential application in the future.
    Applied Physics A 09/2013; 112(3). DOI:10.1007/s00339-013-7785-1 · 1.69 Impact Factor
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