Achieving adjustable elasticity with mechanical metamaterials
update: 2021-11-17 08:22:27     

Mechanical systems with broadly adjustable elasticity are highly desired for various engineering and industrial applications, but are difficult to find in nature. Over the years people have strived for mechanical metamaterials with designed structures that respond flexibly to the external environment. Such materials have mostly been achieved by regular combination of identical units. However, disordered jamming structure, which are physically well defined and allow rigorous mathematical analysis, were recently discovered as another promising approach [1].

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Fig.1. By removing the right bonds we can tune system shear modulus (G) and bulk modulus (K) independently; by adding cross bonds in the complete triangulated areas, we can simultaneously raise both G and K with the ratio G/K fixed.


In a recent collaboration between the theoretical group led by Prof. Xinliang Xu at Beijing Computational Science Research Center and Prof. Lei Xu’s experimental group at the Chinese University of Hong Kong, a topology-correlated transition between affine and non-affine regimes in elasticity is discovered, in both two- and three-dimensional packing-derived networks. Based on this transition, a continuous tunability in between solid-like affine response and liquid-like non-affine response can be achieved within a single system, which is then numerically designed and experimentally realized. In specific, the system exhibits a broadly tunable Poisson’s ratio from positive to negative values, and tunable material strength with fixed Poisson’s ratio (figure 1). This study reveals a fundamental connection between elasticity and network topology, and demonstrates its practical potential for designing mechanical systems and metamaterials [2].


[1] J. W. Rocks, N. Pashine, I. Bischofberger, C. P. Goodrich, A. J. Liu, and S. R. Nagel, Proc. Natl. Acad. Sci. USA 114, 2520-2525 (2017).

[2] X. Shen, C. Fang, Z. Jin, H. Tong, S. Tang, H. Shen, N. Xu, J. H. Y. Lo*, X. L. Xu*, and L. Xu*, Nat. Mater. (2021).

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