Vacancies for controlling the behavior of microstructured three-dimensional mechanical metamaterials

2018 ◽  
Vol 24 (2) ◽  
pp. 511-524 ◽  
Author(s):  
Z Vangelatos ◽  
K Komvopoulos ◽  
CP Grigoropoulos
Keyword(s):  
Strain Energy ◽  
Three Dimensional ◽  
Crystal Lattices ◽  
Mechanical Metamaterials ◽  
Buckling Behavior ◽  
Unit Cells ◽  
Octet Truss ◽  
Topological States ◽  
Energy Dissipated

Mechanical metamaterials are designed to exhibit enhanced properties not found in natural materials or to bolster the properties of existing materials. The theoretical foundations for tuning the mechanical properties have been established, including topological states, controllable buckling behavior, and quasi-two-dimensional mechanical metamaterials with structures containing vacancies. However, the fabrication and experimental procedures to study these structures at the microscale have not been developed yet and the three-dimensional (3D) architectures examined to date are fairly limited. In this study, 3D mechanical metamaterial structures with select unit cells designed to have vacancies were fabricated by multi-photon lithography, having as the principal objective to control (localize) failure and increase the strain energy capacity of the structure. The metamaterial structure from which all the current designs originate is the octet-truss structure, one of the most widely studied 3D metamaterials. The design of the structures was inspired by the role of vacancies in crystal lattices. Vacancies were introduced in the metamaterial structures to allow localized buckling of lattice members to occur in specific unit cells. The significant increase of the strain energy dissipated in these metamaterials is demonstrated by nanoindentation experiments and finite element results. Vacancy effects on the dynamic response of metamaterial structures are also examined in the light of modal analysis simulations. The findings of this study illustrate the importance of strategically placing vacancies in the microlattices of metamaterial structures to control the overall mechanical behavior and greatly increase strain energy dissipation.

Intertwined microlattices greatly enhance the performance of mechanical metamaterials

2019 ◽  
Vol 24 (8) ◽  
pp. 2636-2648 ◽  
Author(s):  
Zacharias Vangelatos ◽  
Vasileia Melissinaki ◽  
Maria Farsari ◽  
Kyriakos Komvopoulos ◽  
Costas Grigoropoulos
Keyword(s):  
Strain Hardening ◽  
Bulk Material ◽  
Three Dimensional ◽  
Structural Complexity ◽  
Structural Principle ◽  
Mechanical Metamaterials ◽  
Unit Cells ◽  
Octet Truss ◽  
Enhanced Strain ◽  
Improved Performance

Mechanical metamaterials demonstrate augmented properties derived from their engineered structure. Advances in three-dimensional (3D) printing technologies have enabled the fabrication of complex metamaterial structures even at the microscale, contributing to the development of light-weight materials with superior mechanical properties. However, understanding of metamaterial strain hardening that is intrinsic to both the structure and arrangement of novel unit cells is sparse and fairly empirical. The main objective of this study was to introduce a new design approach for 3D mechanical metamaterials with enhanced strain hardening and energy absorption, fabricated at the microscale by multiphoton lithography, which is the only fabrication technique that can produce micrometer length scales and high structural complexity. This was accomplished by intertwining simple polyhedra to create more complex geometries in 3D space, using penetration twins as a point of reference, a mechanism of crystal in-growth wherein distinct crystals appear to penetrate each other. This structural principle was used to intertwine the lattice members of the structure and tailor their buckling behavior. The present design is inspired by the first stellation of the rhombic dodecahedron. With this concept, plastic deformation can be controlled through localized buckling of select lattice members. Finite element simulations and nanoindentation experiments demonstrate remarkably improved performance with respect to both strain hardening and energy dissipation of the structure compared to both the bulk material and one of the most thoroughly studied ultralight, ultrastiff mechanical metamaterials, the octet truss.

scholarly journals Dissipation energy in viscoelastic solids under multiaxial loads

2008 ◽  
Vol 15 (1) ◽  
pp. 19-28 ◽  
Author(s):  
Janusz Kolenda
Keyword(s):  
Strain Energy ◽  
Unit Volume ◽  
Static Load ◽  
Three Dimensional ◽  
Viscoelastic Solids ◽  
Dissipation Energy ◽  
Stress Components ◽  
Energy Dissipated ◽  
Periodic Stress

Dissipation energy in viscoelastic solids under multiaxial loads On the basis of the three-dimensional constitutive equations for strains resulting from the Kelvin-Voigt's model and modified Hooke's law for multiaxial stress in viscoelastic solids, the formulae for the energy dissipated in a given time per unit volume have been derived. It is shown that after application or removal of triaxial static load there is no difference in the time functions governing the dissipation of strain energy of volume change and the dissipation of strain energy of distortion. Harmonic in-phase stress and harmonic out-of-phase stress as well as multiaxial periodic stress are also considered. It is demonstrated that in the process of energy dissipation due to normal and shear stress components the role of the latter is dominant.

scholarly journals Divergent Design of Mechanical Metamaterials Clan Deducted from Arc-serpentine Curve

2021 ◽  
Author(s):  
Shengli Mi ◽  
Hongyi Yao ◽  
Xiaoyu Zhao ◽  
Wei Sun
Keyword(s):  
Thick Plate ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Design Strategies ◽  
Shape Morphing ◽  
Mechanical Metamaterials ◽  
Unit Cells ◽  
Combinatorial Principles ◽  
Composite Curve ◽  
Typical Design

Abstract The exotic properties of mechanical metamaterials are determined by their unit-cells' structure and spatial arrangement, in analogy with the atoms of conventional materials. Companioned with the mechanism of structural or cellular materials1–5, the ancient wisdom of origami6–11 and kirigami12–16 and the involvement of multiphysics interaction2,17,18 enrich the programable mechanical behaviors of metamaterials, including shape-morphing8,12,14,16,19, compliance4,5,8,17,20, texture2,18,21, and topology11,18,22−25. However, typical design strategies are mainly convergent, which transfers various structures into one family of metamaterials that are relatively incompatible with the others and do not fully bring combinatorial principles3,10,26 into play. Here, we report a divergent strategy that designs a clan of mechanical metamaterials with diverse properties derived from a symmetric curve consisting of serpentines and arcs. We derived this composite curve into planar and cubic unit-cells and modularized them by attaching magnetics. Moreover, stacking each of them yields two- and three-dimensional auxetic metamaterials, respectively. Assembling with both modules, we achieved three thick plate-like metamaterials separately with flexibility, in-plane buckling, and foldability. Furthermore, we demonstrated that the hybrid of paradox properties is possible by combining two of the above assembles. We anticipate that this divergent strategy paves the path of building a hierarchical library of diverse combinable mechanical metamaterials and making conventional convergent strategies more efficient to various requests. Main

scholarly journals Non-Auxetic Mechanical Metamaterials

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 635 ◽  
Author(s):  
Christa de Jonge ◽  
Helena Kolken ◽  
Amir Zadpoor
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Fatigue Behavior ◽  
Analytical Data ◽  
Three Dimensional ◽  
Mechanical Metamaterials ◽  
Macro Scale ◽  
Unit Cells ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

The concept of “mechanical metamaterials” has become increasingly popular, since their macro-scale characteristics can be designed to exhibit unusual combinations of mechanical properties on the micro-scale. The advances in additive manufacturing (AM, three-dimensional printing) techniques have boosted the fabrication of these mechanical metamaterials by facilitating a precise control over their micro-architecture. Although mechanical metamaterials with negative Poisson’s ratios (i.e., auxetic metamaterials) have received much attention before and have been reviewed multiple times, no comparable review exists for architected materials with positive Poisson’s ratios. Therefore, this review will focus on the topology-property relationships of non-auxetic mechanical metamaterials in general and five topological designs in particular. These include the designs based on the diamond, cube, truncated cube, rhombic dodecahedron, and the truncated cuboctahedron unit cells. We reviewed the mechanical properties and fatigue behavior of these architected materials, while considering the effects of other factors such as those of the AM process. In addition, we systematically analyzed the experimental, computational, and analytical data and solutions available in the literature for the titanium alloy Ti-6Al-4V. Compression dominated lattices, such as the (truncated) cube, showed the highest mechanical properties. All of the proposed unit cells showed a normalized fatigue strength below that of solid titanium (i.e., 40% of the yield stress), in the range of 12–36% of their yield stress. The unit cells discussed in this review could potentially be applied in bone-mimicking porous structures.

Residual strain energy in composites containing particles

1996 ◽  
Vol 11 (2) ◽  
pp. 483-494 ◽  
Author(s):  
Toshiaki Mizutani
Keyword(s):  
Strain Energy ◽  
Crystal Lattices ◽  
Composite Systems ◽  
Surrounding Matrix ◽  
Dispersed Particles ◽  
First Approximation ◽  
Bulk Stress ◽  
The Matrix ◽  
Unit Cells ◽  
Physical Validity

Selsing's formula for radial tension at the particle-matrix interface is extended into a general formula which includes the effects of the amount of dispersed particles. A relationship is derived between individual volumes of strained unit cells in the crystal lattices of the particles and of the surrounding matrix. These relationships are used to predict the effect of the particles (2H−TiB2, 2H−ZrB2, and t−WB) on their unit cells and on the unit cell of the surrounding 6H–SiC matrix. The precision of these predictions was 7.1% or better. Hence, in principle, it is possible to investigate the distributions of residual bulk stress/strain. Estimates of characterizing values of the three composite systems are attempted on the rough basis of the elastic constants of the SiC matrix, confirming the physical validity of this approach as a first approximation. Further, the residual bulk strain energies of the particles and the matrix are discussed in connection with the elastic term involved in the fracture energy of such composites.

Synthesis, structure and characterization of five new organically templated metal sulfates with 2-aminopyridinium

2016 ◽  
Vol 72 (5) ◽  
pp. 432-441 ◽  
Author(s):  
Tamara J. Bednarchuk ◽  
Vasyl Kinzhybalo ◽  
Adam Pietraszko
Keyword(s):  
Materials Science ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Hydrogen Bond Formation ◽  
Unit Cells ◽  
Science Community ◽  
Type 3

The chemistry of organically templated metal sulfates has attracted interest from the materials science community and the development of synthetic strategies for the preparation of organic–inorganic hybrid materials with novel structures and special properties is of current interest. Sulfur–oxygen–metal linkages provide the possibility of using sulfate tetrahedra as building units to form new solid-state materials. A series of novel organically templated metal sulfates of 2-aminopyridinium (2ap) with aluminium(III), cobalt(II), magnesium(II), nickel(II) and zinc(II) were obtained from the respective aqueous solutions and studied by single-crystal X-ray diffraction. The compounds crystallize in centrosymmetric triclinic unit cells in three structure types: type 1 for 2-aminopyridinium hexaaquaaluminium(III) bis(sulfate) tetrahydrate, (C5H7N2)[Al(H2O)6](SO4)2·4H2O, (I); type 2 for bis(2-aminopyridinium) tris[hexaaquacobalt(II)] tetrakis(sulfate) dihydrate, (C5H7N2)2[Co(H2O)6]3(SO4)4·2H2O, (II), and bis(2-aminopyridinium) tris[hexaaquamagnesium(II)] tetrakis(sulfate) dihydrate, (C5H7N2)2[Mg(H2O)6]3(SO4)4·2H2O, (III); and type 3 for bis(2-aminopyridinium) hexaaquanickel(II) bis(sulfate), (C5H7N2)2[Ni(H2O)6](SO4)2, (IV), and bis(2-aminopyridinium) hexaaquazinc(II) bis(sulfate), (C5H7N2)2[Zn(H2O)6](SO4)2, (V). The templating role of the 2ap cation in all of the reported crystalline substances is governed by the formation of characteristic charge-assisted hydrogen-bonded pairs with sulfate anions and the presence of π–π interactions between the cations. Additionally, both coordinated and uncoordinated water molecules are involved in hydrogen-bond formation. As a consequence, extensive three-dimensional hydrogen-bonding patterns are formed in the reported crystal structures.

scholarly journals Harnessing the anisotropic multistability of stacked-origami mechanical metamaterials for effective modulus programming

2018 ◽  
Vol 29 (14) ◽  
pp. 2933-2945 ◽  
Author(s):  
Sattam Sengupta ◽  
Suyi Li
Keyword(s):  
Adaptive Systems ◽  
Three Dimensional ◽  
Unit Cell ◽  
Effective Modulus ◽  
Stable States ◽  
Mechanical Metamaterials ◽  
Principal Axes ◽  
Unit Cells ◽  
Multiple Unit ◽  
Parametric Analyses

This study examines a three-dimensional, anisotropic multistability of a mechanical meta material based on a stacked Miura-ori architecture, and investigates how such a unique stability property can impart stiffness and effective modulus programming functions. The unit cell of this metamaterial can be bistable due to the nonlinear relationship between rigid-folding and crease material bending. Such bistability possesses an unorthodox property: the arrangement of elastically stable and unstable equilibria are different along different principal axes of the unit cell, so that along certain axes the unit cell exhibits two force–deformation relationships concurrently within the same range of deformation. Therefore, one can achieve a notable stiffness adaptation via switching between the two stable states. As multiple unit cells are assembled into a metamaterial, the stiffness adaptation can be aggregated into an on-demand modulus programming capability. That is, via strategically switching different unit cells between stable states, one can control the overall effective modulus. This research examines the underlying principles of anisotropic multistability, experimentally validates the feasibility of stiffness adaptation, and conducts parametric analyses to reveal the correlations between the effective modulus programming and Miura-ori designs. The results can advance many adaptive systems such as morphing structures and soft robotics.

scholarly journals Planar Mechanical Metamaterials with Embedded Permanent Magnets

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1313 ◽  
Author(s):  
Viacheslav Slesarenko
Keyword(s):  
Mechanical Characteristics ◽  
Design Space ◽  
Permanent Magnets ◽  
Three Dimensional ◽  
Three Dimensional Printing ◽  
Numerical Studies ◽  
Mechanical Metamaterials ◽  
Unit Cells ◽  
Post Buckling ◽  
Dimensional Printing

The design space of mechanical metamaterials can be drastically enriched by the employment of non-mechanical interactions between unit cells. Here, the mechanical behavior of planar metamaterials consisting of rotating squares is controlled through the periodic embedment of modified elementary cells with attractive and repulsive configurations of the magnets. The proposed design of mechanical metamaterials produced by three-dimensional printing enables the efficient and quick reprogramming of their mechanical properties through the insertion of the magnets into various locations within the metamaterial. Experimental and numerical studies reveal that under equibiaxial compression various mechanical characteristics, such as buckling strain and post-buckling stiffness, can be finely tuned through the rational placement of the magnets. Moreover, this strategy is shown to be efficient in introducing bistability into the metamaterial with an initially single equilibrium state.

scholarly journals Liquid repellency enhancement through flexible microstructures

2020 ◽  
Vol 6 (32) ◽  
pp. eaba9721 ◽  
Author(s):  
Songtao Hu ◽  
Xiaobao Cao ◽  
Tom Reddyhoff ◽  
Debashis Puhan ◽  
Sorin-Cristian Vladescu ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Type System ◽  
Laser Lithography ◽  
Topological Features ◽  
Mechanical Metamaterials ◽  
Direct Laser ◽  
Flexible Supports ◽  
Recent Developments ◽  
Liquid Repellency

Artificial liquid-repellent surfaces have attracted substantial scientific and industrial attention with a focus on creating functional topological features; however, the role of the underlying structures has been overlooked. Recent developments in micro-nanofabrication allow us now to construct a skin-muscle type system combining interfacial liquid repellence atop a mechanically functional structure. Specifically, we design surfaces comprising bioinspired, mushroom-like repelling heads and spring-like flexible supports, which are realized by three-dimensional direct laser lithography. The flexible supports elevate liquid repellency by resisting droplet impalement and reducing contact time. This, previously unknown, use of spring-like flexible supports to enhance liquid repellency provides an excellent level of control over droplet manipulation. Moreover, this extends repellent microstructure research from statics to dynamics and is envisioned to yield functionalities and possibilities by linking functional surfaces and mechanical metamaterials.

Fabrication defects and limitations of AlSi10Mg lattice structures manufactured by selective laser melting

2021 ◽  
pp. 146442072110127
Author(s):  
Enrico Ossola ◽  
Andrew A Shapiro ◽  
Andre Pate ◽  
Samad Firdosy ◽  
Eugenio Brusa ◽  
...  
Keyword(s):  
Process Parameters ◽  
Cross Sections ◽  
High Surface ◽  
Three Dimensional ◽  
Lattice Structures ◽  
Unit Cells ◽  
Octet Truss ◽  
Overhang Length ◽  
Fabrication Defects

Additive manufacturing has enabled the production of lattice structures with tailored mechanical properties. However, process limitations still exist, affecting the quality of the struts, practically limiting sizes and types of printable unit cells. Typically, long, thin, unsupported horizontal struts exhibit large deviations from ideal geometries, due to high surface roughness and internal porosity. AlSi10Mg specimens were designed and fabricated by laser powder bed fusion to investigate the role of strut orientation, size, and overhang length using different sets of process parameters. Visual inspection, three-dimensional scanning, and metallographic inspection of the cross-sections were performed. A quality control methodology based on dimensional and geometric tolerances has been defined in order to quantitatively characterize the quality of the struts. Optimized process parameters were selected and used to fabricate octet-truss specimens which were then characterized by compression testing.

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