Exploiting self-contact in mechanical metamaterials for new discrete functionalities

Schwarz, David; Felsch, Gerrit; Tauber, Falk; Schiller, Stefan; Slesarenko, Viacheslav

doi:10.1016/j.matdes.2023.112468

Cited by 6 publications

(3 citation statements)

References 53 publications

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“…The results demonstrate that as the triaxial orthogonal compression ratio increases, the Poisson's ratio of the structure gradually decreases and reaches NPR. Then as the triaxial orthogonal compression ratio continues to increase, Poisson's ratio begins to gradually increase due to the self-contact between the interior of the structure [53]. The minimum Poisson's ratio of model I after triaxial orthogonal compression was −0.26, while the minimum Poisson's ratio of model III after triaxial orthogonal compression was −0.01.…”

Section: Resultsmentioning

confidence: 99%

A two-step modeling method for constructing 3D negative Poisson’s ratio materials with high specific strength based on common lattice structures

Lv,

2024

Smart Mater. Struct.

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The traditional negative Poisson's ratio (NPR) structure was basically designed based on concave or rotational mechanisms, resulting in relatively low specific strength and limiting its application. This paper proposed a two-step modeling method to establish a connection between the common lattice structures and NPR structures, which can obtain NPR structures with high specific strength. The models with different triaxial compression ratios were obtained through triaxial compression FE simulation to the selected initial configuration. Then, the mechanical properties of these models were studied through uniaxial compression FE simulation and experiments. In the research scope of this paper, the results demonstrate that the lattice structure can get NPR through the two-step modeling method when the Maxwell's number is less than or equal to zero. The specific strength of the NPR structure obtained through the two-step modeling method was at most 1.5 times higher than that of the traditional 3D star-shaped NPR structure. Due to the high designability and excellent mechanical properties of lattice structures, this work provides a novel method for the manufacture of NPR structures with high specific strength.

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Section: Resultsmentioning

confidence: 99%

A two-step modeling method for constructing 3D negative Poisson’s ratio materials with high specific strength based on common lattice structures

Lv,

2024

Smart Mater. Struct.

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“…Mechanical metamaterials are artificial materials with unconventional mechanical behavior originating from their internal architecture. , Macroscopic responses to applied forces such as negative Poisson’s ratio, − shape matching, and shape morphing can be programmed by unit cell design. Approaches for strain-stiffening metamaterials have focused on harnessing self contact between metamaterial elements under compression or the integration of structural elements that show a transition from bending- to stretching-dominated under tension . In these examples, the mechanical response is “hard-coded” during metamaterial manufacturing.…”

Section: Introductionmentioning

confidence: 99%

Hard- and Soft-Coded Strain Stiffening in Metamaterials via Out-of-Plane Buckling Using Highly Entangled Active Hydrogel Elements

Skarsetz,

Mathes,

Schmidt

et al. 2024

ACS Appl. Mater. Interfaces

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Metamaterials show elaborate mechanical behavior such as strain stiffening, which stems from their unit cell design. However, the stiffening response is typically programmed in the design step and cannot be adapted postmanufacturing. Here, we show hydrogel metamaterials with highly programmable strainstiffening responses by exploiting the out-of-plane buckling of integrated pH-switchable hydrogel actuators. The stiffening upon reaching a certain extension stems from the initially buckled active hydrogel beams. At low strain, the beams do not contribute to the mechanical response under tension until they straighten with a resulting step-function increase in stiffness. In the hydrogel actuator design, the acrylic acid concentration hard-codes the configuration of the metamaterial and range of possible stiffening onsets, while the pH soft-codes the exact stiffening onset point after fabrication. The utilization of out-of-plane buckling to realize subsequent stiffening without the need to deform the passive structure extends the application of hydrogel actuators in mechanical metamaterials. Our concept of out-of-plane buckled active elements that stiffen only under tension enables strain-stiffening metamaterials with high programmability before and after fabrication.

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“…21,22 This was achieved by introducing redundancies within the microstructure in order to create two sets of functioning microstructures therein so that when the loading direction is reversed the functional and redundant parts of the microstructure become redundant and functional, respectively, or by creative design of metamaterials to induce different deformation mechanisms. [23][24][25][26][27][28][29] Mechanical metamaterials take advantage of geometrical properties and mechanism theories to produce more precise microstructural deformation in order to attain the desired effective properties, [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] which include taking inspiration from ancient motifs and cultural objects. 47,48 The negativity of Poisson's ratio has many applications, and this includes the decrease of in-plane stresses of a plate undergoing synclastic deformation.…”

Section: Introductionmentioning

confidence: 99%

Metamaterials with step function Poisson's ratio at original state

Lim

2024

Proceedings of the Institution of Mechanical Engineers, Part L:

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Two mechanical metamaterials based on fragmentation-reconstitution (FR) deformation mechanism are designed herein not only to establish the condition of Poisson's ratio discontinuity but also to offer a simpler, and hence a technically more feasible, FR metamaterial. Each metamaterial consists of interconnected rigid rhombi with slits within every rhombus such that prescription of on-axis strain would fragment each rhombus unit into six sub-units, while a reversal of the strain would reconstitute every six sub-units into a single rhombus. By geometrical construction, the Poisson's ratio expressions of both metamaterials were developed for infinitesimal and finite deformations. Results show that each metamaterial has no unique Poisson's ratio at the original state, but instead has two distinct Poisson's ratio, with a consolidated value of −1 under compression but abruptly jumps to other values under tension. The observations made for these metamaterials suggest that each of them can behave as two different materials under tension and compression, thereby enabling them to function in ways that cannot be achieved by other materials and metamaterials.

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Exploiting self-contact in mechanical metamaterials for new discrete functionalities

Cited by 6 publications

References 53 publications

A two-step modeling method for constructing 3D negative Poisson’s ratio materials with high specific strength based on common lattice structures

A two-step modeling method for constructing 3D negative Poisson’s ratio materials with high specific strength based on common lattice structures

Hard- and Soft-Coded Strain Stiffening in Metamaterials via Out-of-Plane Buckling Using Highly Entangled Active Hydrogel Elements

Metamaterials with step function Poisson's ratio at original state

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