Smart metamaterials with tunable auxetic and other properties

Abstract

Auxetic and other mechanical metamaterials are typically studied in situations where they are subjected solely to mechanical forces or displacements even though they may be designed to exhibit additional anomalous behaviour or tunability when subjected to other disturbances such as changes in temperature or magnetic fields. It is shown that externally applied magnetic fields can tune the geometry and macroscopic properties of known auxetics that incorporate magnetic component/s, thus resulting in a change of their macroscopic properties. Anomalous properties which are observed in such novel magneto-mechanical systems include tunable Poisson's ratios, bi-stability or multi-stability, depending on the applied magnetic fields, and other electromagnetic-mechanical effects such as strain dependent induced electric currents and magnetic fields. The properties exhibited depend, amongst other things, on the relative position and orientation of the magnetic insertion/s within the structure, the geometry of the system and the magnetic strength of the magnetic components, including that of the external magnetic field.

Homogenization of 1D and 2D magnetoelastic lattices

“…It is also generalized for arbitrarily complex elastic structures, but is not presented for use in systems exhibiting non-nearest neighbor interactions, such as magnetic interactions, and must therefore be extended for application to magneto-elastic lattices. In contrast to the work by Grima et al [13], the structures discussed in this publication contain magnetic dipole moments perpendicular to the lattice plane, and mechanical properties including stiffnesses are presented. The changes Poisson's ratio in this publication are not brought about solely by geometric orientation as in reference [13], but also through changes in interaction stiffnesses, which are caused by the included magnets.…”

“…In contrast to the work by Grima et al [13], the structures discussed in this publication contain magnetic dipole moments perpendicular to the lattice plane, and mechanical properties including stiffnesses are presented. The changes Poisson's ratio in this publication are not brought about solely by geometric orientation as in reference [13], but also through changes in interaction stiffnesses, which are caused by the included magnets. Furthermore, this publication focus specifically on the multistability and bistability of the studied lattices and how reconfiguration effects properties.…”

“…Related work has been presented [13] in which finite magneto-elastic structures show that their Poisson's ratio can be tuned with the application of a non-uniform external magnetic field and through changes in constituent dimensions. The magnetic dipole moments in the 2D structures discussed therein are oriented in the plane of the system and the changes in Poisson's ratio are a result of the re-orientation of the system's rigid entities under the constant application of the external magnetic field.…”

Nano‐ and Micro‐Auxetic Plasmonic Materials

“…Mater. 2016, 28, 5176-5180 www.advmat.de www.MaterialsViews.com Micro-and nano-auxetic metamaterials combined with actuation mechanisms of reconfi gurable terahertz and photo nic metamaterials [ 30,31,33,34 ] promise a class of tunable nano mechanical metadevices with fi xed optical anisotropy. In contrast to conventional materials and metamaterials, where stretching or compression necessarily changes the anisotropy of the structure, auxetics provide an opportunity where both the aspect ratio of the unit cell and its corresponding optical anisotropy (or isotropy) can in principle remain unchanged with actuation.…”

Colossal magnetocaloric effect in magneto-auxetic systems

“…The first papers on auxetic materials and structures appeared more than 20 years ago [5,[7][8][9][10] however only recently were they studied for their magnetic properties. Such studies include investigations on the magnetic properties of auxetic foams [11,12], magnetic ferrogels [13,14], CoFe 2 O 4 epitaxial thin films [15], magnetostrictive iron-gallium alloys galfenol [16] and MASs [17]. Wave propagation was also investigated in magneto-elastic lattices [18].…”