Sequential metamaterials with alternating Poisson’s ratios

Abstract

Mechanical metamaterials have been designed to achieve custom Poisson’s ratios via the deformation of their microarchitecture. These designs, however, have yet to achieve the capability of exhibiting Poisson’s ratios that alternate by design both temporally and spatially according to deformation. This capability would enable dynamic shape-morphing applications including smart materials that process mechanical information according to multiple time-ordered output signals without requiring active control or power. Herein, both periodic and graded metamaterials are introduced that leverage principles of differential stiffness and self-contact to passively achieve sequential deformations, which manifest as user-specified alternating Poisson’s ratios. An analytical approach is provided with a complementary software tool that enables the design of such materials in two- and three-dimensions. This advance in design capability is due to the fact that the tool computes sequential deformations more than an order of magnitude faster than contemporary finite-element packages. Experiments on macro- and micro-scale designs validate their predicted alternating Poisson’s ratios.

Programming Soft Shape-Morphing Systems by Harnessing Strain Mismatch and Snap-Through Bistability: A Review

“…Mechanical metamaterials are a class of artificial materials with unconventional mechanical properties, such as negative Poisson’s ratio [ 91 ], negative swelling ratio [ 92 ], energy absorption [ 93 ], reconfigurable deployment [ 94 ], and a tunable phononic response [ 95 ]. These extraordinary functionalities are not directly related to the intrinsic properties of their constituent materials, but are dependent upon the elaborately designed microstructures as the basic building blocks.…”

3D Auxetic Metamaterials with Elastically‐Stable Continuous Phase Transition

“…[6,7,[41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] Unfortunately, despite the large literature on auxetic mechanical metamaterials, very few papers report mechanical phase transitions. [57][58][59] In chemistry, thermodynamics, and generally physical sciences, phase transitions are the physical processes of transition between states corresponding to different properties. [60] They typically correspond to a change in the order of parameter that is defined depending on the investigated phenomenon and system.…”

“…For instance, in phasetransforming structures with magnetic inclusions, [58] it was shown that the resulting metamaterial can exhibit different static and dynamic mechanical properties, before and after being subjected to the external stimulus. Furthermore, in the case of nonmagnetic mechanical metamaterials, Farzaneh et al [57] studied sequential metamaterials with alternating Poisson's ratios under both compressive and tensile loads. Other examples include the work by Janbaz et al [59] where a strain-induced phase transition of Poisson's ratio was observed for a system consisting of a combination of stiff and soft bi-beams.…”

“…[ 6,7,41–56 ] Unfortunately, despite the large literature on auxetic mechanical metamaterials, very few papers report mechanical phase transitions. [ 57–59 ]…”

“…Furthermore, in the case of nonmagnetic mechanical metamaterials, Farzaneh et al. [ 57 ] studied sequential metamaterials with alternating Poisson's ratios under both compressive and tensile loads. Other examples include the work by Janbaz et al.…”