Rational design of soft mechanical metamaterials: Independent tailoring of elastic properties with randomness

Mirzaali, Mohammad J.; Hedayati, Reza; Vena, Pasquale; Vergani, L.; Strano, Matteo; Zadpoor, Amir A.

doi:10.1063/1.4989441

Cited by 80 publications

(49 citation statements)

References 18 publications

(16 reference statements)

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“…Recent studies have shown that rational distribution of auxetic and conventional could give rise to novel properties and functionalities. 29 We considered five graded designs to demonstrate the presented "action-at-a-distance" concept, namely linear, radial gradient negative to positive (NTP), radial gradient positive to negative (PTN), checkered, and striped (Fig. 1).…”

confidence: 99%

Action-at-a-distance metamaterials: Distributed local actuation through far-field global forces

et al. 2018

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Mechanical metamaterials are a sub-category of designer materials where the geometry of the material at the small-scale is rationally designed to give rise to unusual properties and functionalities. Here, we propose the concept of “action-at-a-distance” metamaterials where a specific pattern of local deformation is programmed into the fabric of (cellular) materials. The desired pattern of local actuation could then be achieved simply through the application of one single global and far-field force. We proposed graded designs of auxetic and conventional unit cells with changing Poisson’s ratios as a way of making “action-at-a-distance” metamaterials. We explored five types of graded designs including linear, two types of radial gradients, checkered, and striped. Specimens were fabricated with indirect additive manufacturing and tested under compression, tension, and shear. Full-field strain maps measured with digital image correlation confirmed different patterns of local actuation under similar far-field strains. These materials have potential applications in soft (wearable) robotics and exosuits.

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confidence: 99%

Action-at-a-distance metamaterials: Distributed local actuation through far-field global forces

et al. 2018

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“…Random elastic networks are widely studied [36][37][38] , but there are still large gaps between theoretical investigations and practical purposes such as real solid materials. Mechanical meta-materials with increasing degree of disorder are just emerging [39][40][41][42][43] . Whether disorder is merely the price to pay for self-assembly or whether it provides some advantage is still an open issue.The structural behaviour of lattice based metamaterials, made up of beams with non-hinged nodes, is generally divided into two regimes: stretching-dominated and bending-dominated 44 .…”

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confidence: 99%

Density scaling in the mechanics of a disordered mechanical meta-material

Rayneau-Kirkhope

Bonfanti

Zapperi

2019

Applied Physics Letters

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Nature provides examples of self-assemble lightweight disordered network structures with remarkable mechanical properties which are desirable for many applications purposes but challenging to reproduce artificially. Previous experimental and computational studies investigated the mechanical responses of random network structures focusing on topological and geometrical aspects in terms of variable connectivity or probability to place beam elements. However for practical purposes an ambitious challenge is to design new materials with the possibility to taylor their mechanical features such as stiffness. Here, we design a two dimensional disordered mechanical meta-material exhibiting unconventional stiffness-density scaling in the regime where both bending and stretching are relevant for deformation. In this regime, the mechanical meta-material covers a wide interval of the Young modulus -density plane, simultaneously exhibiting high critical stress and critical strain. Our results, supported by finite element simulations, provides the guiding principles to design on demand disordered metamaterials, bridging the gap between artificial and naturally occurring materials.The mechanical properties of lattice materials of many types, such as foams 1 , cellular solids 2-4 , microlattices 5 , trusses 6 , made of connected elements, have been intensively studied mainly due to their lightweight structures and remarkable mechanical properties 7,8 . The high strength to weight ratio of bone 9,10 or balsa 11 , the elastic properties of spider silk 12,13 and the fracture resistance of nacre 14,15 are just few of the naturally occurring structures that derive their mechanical properties from their underlying geometry. These types of materials attract growing interest in many fields ranging from commercial products such as those related to food industry, to architectural applications such as energy absorption and management 1 and in modern technologies where their geometrical features are exploited to achieve a myriade of performances.In the recent years composite structures started to be rationally architected with the aim to achieve targeted properties 16 , and emerging significant breakthroughs 17 are favoured alongside with the advances in digital manufacturing technologies i.e. 3D printing and automated assembly. Artificially designed materials are recently termed meta-materials 18-22 , specifically, mechanical meta-materials indicate a class of structures whose mechanical properties are a consequence of their underlying geometry rather than their constituent material 23-25 . Through the prudent choice of a meta-materials underlying architecture, it is possible to create geometries whose structural performance far exceeds that of the material from which it is made 24 . These structures can be designed to exhibit a wide range of beneficial properties, including high strength to weight ratio 26,27 , auxetic behaviour 16,28-30 , energy trapping 20,31 and fracture resistance 32,33 , among many others 23 .Typically artificil meta-...

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“…17 While batch-size-indifference directly translates to the feasibility of producing patient-specific biomaterials, implants, and surgical instruments [18][19][20][21][22] that exactly match the complex and highly variable anatomy 23 of individual patients, complexity-for-free enables designers to use complex geometries that give rise to favorable properties and advanced functionalities. [24][25][26][27][28][29] One particularly useful class of geometrically complex biomaterials is the class of topologically ordered porous biomaterials that are designed by repeating one or more regular unit cells in different spatial directions to create a lattice (cellular) structure (Fig. 1).…”

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confidence: 99%