Mechanical metamaterial

Mechanical metamaterials are artificial structures with mechanical properties defined by their structure rather than their composition. They can be seen as a counterpart to the rather well-known family of optical metamaterials. They are often also termed elastodynamic metamaterials and include acoustic metamaterials as a special case of vanishing shear. Their mechanical properties can be designed to have values which cannot be found in nature.[1]

Examples of mechanical metamaterials

Acoustic / phononic metamaterials

Acoustic or phononic metamaterials can exhibit acoustic properties not found in nature, such as negative effective bulk modulus,[2] negative effective mass density,[3][4] or double negativity.[5][6] They find use in (mostly still purely scientific) applications like acoustic subwavelength imaging,[7] superlensing,[8] negative refraction [9] or transformation acoustics.[10][11]

Materials with negative Poisson's ratio (auxetics)

Poisson's ratio defines how a material expands (or contracts) transversely when being compressed longitudinally. While most natural materials have a positive Poisson's ratio (coinciding with our intuitive idea that by compressing a material it must expand in the orthogonal direction), a family of extreme materials known as auxetic materials can exhibit Poisson's ratios below zero. Examples of these can be found in nature, or fabricated,[12][13] and often consist of a low-volume microstructure that grants the extreme properties to the bulk material. Simple designs of composites possessing negative Poisson's ratio (inverted hexagonal periodicity cell) were published in 1985.[14][15] In addition, certain origami folds such as the Miura fold and, in general, zigzag-based folds are also known to exhibit negative Poisson's ratio.[16][17][18][19]

Metamaterials with negative longitudinal and volume compressibility transitions

In a closed thermodynamic system in equilibrium, both the longitudinal and volumetric compressibility are necessarily non-negative because of stability constraints. For this reason, when tensioned, ordinary materials expand along the direction of the applied force. It has been shown, however, that metamaterials can be designed to exhibit negative compressibility transitions, during which the material undergoes contraction when tensioned (or expansion when pressured).[20] When subjected to isotropic stresses, these metamaterials also exhibit negative volumetric compressibility transitions.[21] In this class of metamaterials, the negative response is along the direction of the applied force, which distinguishes these materials from those that exhibit negative transversal response (such as in the study of negative Poisson's ratio).

Pentamode metamaterials or meta-fluids
SEM image of a pentamode metamaterial (with a size of roughly 300μm)

A pentamode metamaterial is an artificial three-dimensional structure which, despite being a solid, ideally behaves like a fluid. Thus, it has a finite bulk but vanishing shear modulus, or in other words it is hard to compress yet easy to deform. Speaking in a more mathematical way, pentamode metamaterials have an elasticity tensor with only one non-zero eigenvalue and five (penta) vanishing eigenvalues.

Pentamode structures have been proposed theoretically by Graeme Milton and Andrej Cherkaev in 1995 [22] but have not been fabricated until early 2012.[23] According to theory, pentamode metamaterials can be used as the building blocks for materials with completely arbitrary elastic properties.[22] Anisotropic versions of pentamode structures are a candidate for transformation elastodynamics and elastodynamic cloaking.

Cosserat and Micropolar Metamaterials

Very often Cauchy elasticity is sufficient to describe the effective behavior of mechanical metamaterials. When the unit cells of typical metamaterials are not centrosymmetric it has been shown that an effective description using chiral micropolar elasticity (or Cosserat [24]) was required.[25] Micropolar elasticity combines the coupling of translational and rotational degrees of freedom in the static case and shows an equivalent behavior to the optical activity.

Willis materials

In 2006 Milton, Briane and Willis[26] showed that the correct invariant form of linear elastodynamics is the local set of equations originally proposed by Willis in the late 1970s and early 1980s, to describe the elastodynamics of inhomogeneous materials.[27] This includes the apparently unusual (in elastic materials) coupling between stress, strain and velocity and also between momentum, strain and velocity. Invariance of Navier's equations can occur under the transformation theory, but would required materials with non-symmetric stress, hence the interest in Cosserat materials noted above. The theory was given further foundations in the paper by Norris and Shuvalov.[28]

Hyperelastic cloaking and invariance

Another mechanism to achieve non-symmetric stress is to employ pre-stressed hyperelastic materials and the theory of "small on large", i.e. elastic wave propagation through pre-stressed nonlinear media. Two papers written in the Proceedings of the Royal Society A in 2012 established this principal of so-called hyperelastic cloaking and invariance[29] [30] and have been employed in numerous ways since then in association with elastic wave cloaking and phononic media.

References
  1. Surjadi, James Utama; et al. (4 January 2019). "Mechanical Metamaterials and Their Engineering Applications". Advanced Engineering Materials. 21 (3): 1800864. doi:10.1002/adem.201800864.
  2. Lee, Sam Hyeon; Park, Choon Mahn; Seo, Yong Mun; Wang, Zhi Guo; Kim, Chul Koo (29 April 2009). "Acoustic metamaterial with negative modulus". Journal of Physics: Condensed Matter. 21 (17): 175704. arXiv:0812.2952. Bibcode:2009JPCM...21q5704L. doi:10.1088/0953-8984/21/17/175704. PMID 21825432. S2CID 26358086.
  3. Lee, Sam Hyeon; Park, Choon Mahn; Seo, Yong Mun; Wang, Zhi Guo; Kim, Chul Koo (1 December 2009). "Acoustic metamaterial with negative density". Physics Letters A. 373 (48): 4464–4469. Bibcode:2009PhLA..373.4464L. doi:10.1016/j.physleta.2009.10.013.
  4. Yang, Z.; Mei, Jun; Yang, Min; Chan, N.; Sheng, Ping (1 November 2008). "Membrane-Type Acoustic Metamaterial with Negative Dynamic Mass" (PDF). Physical Review Letters. 101 (20): 204301. Bibcode:2008PhRvL.101t4301Y. doi:10.1103/PhysRevLett.101.204301. PMID 19113343.
  5. Ding, Yiqun; Liu, Zhengyou; Qiu, Chunyin; Shi, Jing (August 2007). "Metamaterial with Simultaneously Negative Bulk Modulus and Mass Density". Physical Review Letters. 99 (9): 093904. Bibcode:2007PhRvL..99i3904D. doi:10.1103/PhysRevLett.99.093904. PMID 17931008.
  6. Lee, Sam Hyeon; Park, Choon Mahn; Seo, Yong Mun; Wang, Zhi Guo; Kim, Chul Koo (1 February 2010). "Composite Acoustic Medium with Simultaneously Negative Density and Modulus". Physical Review Letters. 104 (5): 054301. arXiv:0901.2772. Bibcode:2010PhRvL.104e4301L. doi:10.1103/PhysRevLett.104.054301. PMID 20366767.
  7. Zhu, J.; Christensen, J.; Jung, J.; Martin-Moreno, L.; Yin, X.; Fok, L.; Zhang, X.; Garcia-Vidal, F. J. (2011). "A holey-structured metamaterial for acoustic deep-subwavelength imaging". Nature Physics. 7 (1): 52–55. Bibcode:2011NatPh...7...52Z. doi:10.1038/nphys1804. hdl:10261/52201.
  8. Li, Jensen; Fok, Lee; Yin, Xiaobo; Bartal, Guy; Zhang, Xiang (2009). "Experimental demonstration of an acoustic magnifying hyperlens". Nature Materials. 8 (12): 931–934. Bibcode:2009NatMa...8..931L. doi:10.1038/nmat2561. PMID 19855382.
  9. Christensen, Johan; de Abajo, F. (2012). "Anisotropic Metamaterials for Full Control of Acoustic Waves". Physical Review Letters. 108 (12): 124301. Bibcode:2012PhRvL.108l4301C. doi:10.1103/PhysRevLett.108.124301. hdl:10261/92293. PMID 22540586.
  10. Farhat, M.; Enoch, S.; Guenneau, S.; Movchan, A. (2008). "Broadband Cylindrical Acoustic Cloak for Linear Surface Waves in a Fluid". Physical Review Letters. 101 (13): 134501. Bibcode:2008PhRvL.101m4501F. doi:10.1103/PhysRevLett.101.134501. PMID 18851453.
  11. Cummer, Steven A; Schurig, David (2007). "One path to acoustic cloaking". New Journal of Physics. 9 (3): 45. Bibcode:2007NJPh....9...45C. doi:10.1088/1367-2630/9/3/045.
  12. Xu, B.; Arias, F.; Brittain, S. T.; Zhao, X.-M.; Grzybowski, B.; Torquato, S.; Whitesides, G. M. (1999). "Making Negative Poisson's Ratio Microstructures by Soft Lithography". Advanced Materials. 11 (14): 1186–1189. doi:10.1002/(SICI)1521-4095(199910)11:14<1186::AID-ADMA1186>3.0.CO;2-K.
  13. Bückmann, Tiemo; Stenger, Nicolas; Kadic, Muamer; Kaschke, Johannes; Frölich, Andreas; Kennerknecht, Tobias; Eberl, Christoph; Thiel, Michael; Wegener, Martin (22 May 2012). "Tailored 3D Mechanical Metamaterials Made by Dip-in Direct-Laser-Writing Optical Lithography". Advanced Materials. 24 (20): 2710–2714. doi:10.1002/adma.201200584. PMID 22495906.
  14. Kolpakovs, A.G. (1985). "Determination of the average characteristics of elastic frameworks". Journal of Applied Mathematics and Mechanics. 49 (6): 739–745. Bibcode:1985JApMM..49..739K. doi:10.1016/0021-8928(85)90011-5.
  15. Almgren, R.F. (1985). "An isotropic three-dimensional structure with Poisson's ratio=-1". Journal of Elasticity. 15 (4): 427–430. doi:10.1007/bf00042531. S2CID 123298026.
  16. Schenk, Mark (2011). Folded Shell Structures, PhD Thesis (PDF). University of Cambridge, Clare College.
  17. Wei, Z. Y.; Guo, Z. V.; Dudte, L.; Liang, H. Y.; Mahadevan, L. (2013-05-21). "Geometric Mechanics of Periodic Pleated Origami". Physical Review Letters. 110 (21): 215501. arXiv:1211.6396. Bibcode:2013PhRvL.110u5501W. doi:10.1103/PhysRevLett.110.215501. PMID 23745895. S2CID 9145953.
  18. Eidini, Maryam; Paulino, Glaucio H. (2015). "Unraveling metamaterial properties in zigzag-base folded sheets". Science Advances. 1 (8): e1500224. arXiv:1502.05977. Bibcode:2015SciA....1E0224E. doi:10.1126/sciadv.1500224. ISSN 2375-2548. PMC 4643767. PMID 26601253.
  19. Eidini, Maryam (2016). "Zigzag-base folded sheet cellular mechanical metamaterials". Extreme Mechanics Letters. 6: 96–102. arXiv:1509.08104. doi:10.1016/j.eml.2015.12.006. S2CID 118424595.
  20. Nicolaou, Zachary G.; Motter, Adilson E. (2012). "Mechanical metamaterials with negative compressibility transitions". Nature Materials. 11 (7): 608–13. arXiv:1207.2185. Bibcode:2012NatMa..11..608N. doi:10.1038/nmat3331. PMID 22609557. S2CID 13390648.
  21. Nicolaou, Zachary G.; Motter, Adilson E. (2013). "Longitudinal Inverted Compressibility in Super-strained Metamaterials". Journal of Statistical Physics. 151 (6): 1162–1174. arXiv:1304.0787. Bibcode:2013JSP...151.1162N. doi:10.1007/s10955-013-0742-8. S2CID 32700289.
  22. Milton, Graeme W.; Cherkaev, Andrej V. (1 January 1995). "Which Elasticity Tensors are Realizable?". Journal of Engineering Materials and Technology. 117 (4): 483. doi:10.1115/1.2804743.
  23. Kadic, Muamer; Bückmann, Tiemo; Stenger, Nicolas; Thiel, Michael; Wegener, Martin (1 January 2012). "On the practicability of pentamode mechanical metamaterials". Applied Physics Letters. 100 (19): 191901. arXiv:1203.1481. Bibcode:2012ApPhL.100s1901K. doi:10.1063/1.4709436. S2CID 54982039.
  24. Rueger, Z.; Lakes, R. S. (8 February 2018). "Strong Cosserat Elasticity in a Transversely Isotropic Polymer Lattice". Physical Review Letters. 120 (6): 065501. Bibcode:2018PhRvL.120f5501R. doi:10.1103/PhysRevLett.120.065501. PMID 29481282.
  25. Frenzel, Tobias; Kadic, Muamer; Wegener, Martin (23 November 2017). "Three-dimensional mechanical metamaterials with a twist". Science. 358 (6366): 1072–1074. Bibcode:2017Sci...358.1072F. doi:10.1126/science.aao4640. PMID 29170236.
  26. Graeme W Milton; Marc Briane; John R Willis (2006-10-24). "On cloaking for elasticity and physical equations with a transformation invariant form". New Journal of Physics. 8 (10): 248. doi:10.1088/1367-2630/8/10/248. ISSN 1367-2630.
  27. Willis, J. R. (1981-01-01). "Variational principles for dynamic problems for inhomogeneous elastic media". Wave Motion. 3 (1): 1–11. doi:10.1016/0165-2125(81)90008-1. ISSN 0165-2125.
  28. Norris, A. N.; Shuvalov, A. L. (2011-09-01). "Elastic cloaking theory". Wave Motion. Special Issue on Cloaking of Wave Motion. 48 (6): 525–538. arXiv:1103.6045. doi:10.1016/j.wavemoti.2011.03.002. ISSN 0165-2125.
  29. Parnell, William J. (2012-02-08). "Nonlinear pre-stress for cloaking from antiplane elastic waves". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 468 (2138): 563–580. arXiv:1203.3246. Bibcode:2012RSPSA.468..563P. doi:10.1098/rspa.2011.0477. S2CID 51681026.
  30. Norris, A. N.; Parnell, W. J. (2012-10-08). "Hyperelastic cloaking theory: transformation elasticity with pre-stressed solids". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 468 (2146): 2881–2903. arXiv:1204.4655. Bibcode:2012RSPSA.468.2881N. doi:10.1098/rspa.2012.0123. S2CID 53619286.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.