Additive manufacturing of 3D nano-architected metals

Vyatskikh, Andrey; Delalande, Stéphane; Kudo, Akira; Zhang, Xuan; Portela, C.M.; Greer, Julia R.

doi:10.1038/s41467-018-03071-9

Cited by 435 publications

(324 citation statements)

References 49 publications

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“…Engineering parts made from foams or lattices are increasingly used in a large variety of engineering applications over a wide range of length scale, e. g. space frames in civil engineering, the cores of lightweight sandwich structures, and cardiovascular stents [1]. Recent advances in additive manufacturing methods [2,3] have enabled the development of novel two-dimensional (2D) or three-dimensional (3D) architectured structures with high stiffness and strength relative to those of foams [4]. Whilst the compressive behaviour of lattices and foams has been examined extensively [5][6][7][8], only limited studies have been performed on the macroscopic response and failure criteria under tensile loading [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

The role of defects in dictating the strength of brittle honeycombs made by rapid prototyping

Tankasala

Fleck

2019

Acta Materialia

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Rapid prototyping is an emerging technology for the fast make of engineering components. A common technique is to laser cut a two-dimensional (2D) part from polymethyl methacrylate (PMMA) sheet. However, both manufacturing defects and design defects (such as stress raisers) exist in the part, and these degrade its strength. In the present study, a combination of experiment and finite element analysis is used to determine the sensitivity of the tensile strength of PMMA hexagonal lattices to both as-manufactured and as-designed defects. The as-manufactured defects include variations in strut thickness and in Plateau border radius. The knockdown in lattice tensile strength is measured for lattice relative density in the range of 0.07 to 0.19. A systematic finite element (FE) study is performed to assess the explicit role of each type of as-manufactured defect on the lattice strength. As-designed defects such as randomly perturbed joints, missing cells, and solid inclusions are introduced within a regular hexagonal lattice. The notion of a transition flaw size is used to quantify the sensitivity of lattice strength to defect size.in the literature and explores the influence of both as-manufactured and as-designed defects upon tensile strength. As-manufactured defects in lattice materialsThe macroscopic properties of lattice materials are sensitive to the material properties of individual struts. In turn, the properties of the struts depend upon the details of the thermal history imposed by the manufacturing process, such as selective laser melting (SLM) for example. Consequently, a large scale octet-truss lattice made from the SLM technique has a lower yield strength than a smaller lattice of the same relative density [6]. In the present study, we employ a laser-cutting technique to manufacture 2D hexagonal lattices from amorphous polymethyl methacrylate (PMMA) sheets. This manufacturing technique is commonly used for the rapid prototyping of an engineering part, but leads to variability in cell wall material properties analogous to those of additive techniques such as selective laser sintering and 3D printing [12].The sensitivity of modulus and yield strength to imperfections within a lattice has been studied in systematic fashion, see for example [13][14][15][16][17][18][19][20][21][22]. It is generally accepted that a number of types of imperfection, such as missing or wavy cell walls degrade the tensile and compressive properties, although the sensitivity of the dispersion in macroscopic properties to the statistical distribution of imperfections has received limited attention. Further, little is known about the relationship between the macroscopic ductility of a lattice or foam and its underlying topology. One might expect that the ductility of a bending-dominated lattice (such as the hexagonal honeycomb) much exceeds that of the parent solid by the following simple argument.Assume that the macroscopic response of the lattice can be idealised by that of a long slender beam (of length and height t), which is buil...

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Section: Introductionmentioning

confidence: 99%

The role of defects in dictating the strength of brittle honeycombs made by rapid prototyping

Tankasala

Fleck

2019

Acta Materialia

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“…The most notable trend emerging from the review of the most recent state-of-the-art is the increasing and pervasive employment of additive manufacturing solutions for the engineeringoriented application of the large amount of theoretical knowledge about auxetic materials based on tailorable microstructures [35], [36], [37], [38]. Indeed, additive manufacturing is rapidly evolving as one of the most promising manufacturing technologies for designing, optimizing, rapid prototyping and large scale producing three-dimensional architected cellular materials with high-fidelity realization of complex microstructural topologies [39], [40], [41], [42], [43], [44]. Interesting advanced applications for additive manufactured architected materials range across many modern fields in frontier engineering, from micro-electro-mechanical systems to lightweight components for automotive or aerospace industry, from patient-specific medical implants to smart structural elements in parametric engineering and architecture.…”

Section: Introductionmentioning

confidence: 99%

A novel layered topology of auxetic materials based on the tetrachiral honeycomb microstructure

et al. 2019

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Microstructured honeycomb materials may exhibit exotic, extreme and tailorable mechanical properties, suited for innovative technological applications in a variety of modern engineering fields. The paper is focused on analysing the directional auxeticity of tetrachiral materials, through analytical, numerical and experimental methods. Theoretical predictions about the global elastic properties have been successfully validated by performing tensile laboratory tests on tetrachiral samples, realized with high precision 3D printing technologies. Inspired by the kinematic behaviour of the tetrachiral material, a newly-design bi-layered topology, referred to as bi-tetrachiral material, has been theoretically conceived and mechanically modelled. The novel topology virtuously exploits the mutual collaboration between two tetrachiral layers with opposite chiralities. The bi-tetrachiral material has been verified to outperform the tetrachiral material in terms of global Young modulus and, as major achievement, to exhibit a remarkable auxetic behaviour. Specifically, experimental results, confirmed by parametric analytical and computational analyses, have highlighted the effective possibility to attain strongly negative Poisson ratios, identified as a peculiar global elastic property of the novel bi-layered topology.

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“…We aim to explore the feasibility to electrodeposit a large number of architectured structures such as microlattices, [6,[21][22][23][24] MEMS components, [25] and microfluidic structures. [26][27][28] At the same time, we want to assess the mechanical properties of the deposited material.…”

Section: Introductionmentioning

confidence: 99%

Additive Manufacturing through Galvanoforming of 3D Nickel Microarchitectures: Simulation‐Assisted Synthesis

Schürch

Pethő

Schwiedrzik

et al. 2018

Adv Materials Technologies

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template require homogenous deposition conditions, which can be complex to monitor. In 2D LIGA, a majority of challenges were addressed and simulated. Griffiths et al. [9][10][11] pioneered LIGA simulation and focused on transport limitations occurring in templates. Nilson and Griffiths [12] added a detailed description of natural convection in templates and Chen and Evans [13] optimized moving boundaries in finite element method (FEM) simulation for electrodeposition. Tsai et al. [14] discussed ion concentration gradients in high aspect ratio with a tertiary current distribution model. Pulsed electrodeposition, a frequently used technique to improve homogeneity of the deposits, was used and modeled by Yeh et al. [15] Similar to the 2D LIGA process, 3D LIGA was used to create complex structures. However, previous work was mainly focused on material properties of these structures, not on the study and description of the electrodeposition into the complex 3D templates. In addition to the already existing difficulties in 2D LIGA, deposition in 3D templates offers multiple additional challenges. Large changes of the active area in vertical direction, bottleneck features within the templates, lateral diffusion and migration of the electrolyte constituents have to be considered. [16] Furthermore, 3D templates can shield and deflect electrolyte current density vectors inducing changes in local current density.To understand the aforementioned challenges, this work exploits 3D nanocrystalline nickel electrodeposition simulation built upon the previously mentioned 2D electrodeposition simulation studies. The simulation is verified by nickel electrodeposition from a nickel sulfamate electrolyte [17][18][19] into 3D microprinted electrode arrays. Nickel is a suitable material for electrodeposition as it is thoroughly researched as well as simulated. Nickel sulfamate electrolytes produce low internal stress deposits, crucial for 3D microstructures. Nickel sulfamate can also be used for pulsed electrodeposition, involving long, low current pulses, another instrumental technique to ensure good filling ratio. [18] To display the potential of the process, we present a new variant of a 3D LIGA process using negative-tone photoresist for the creation of electrodeposition templates and the subsequent stripping of the tone resist. Negative-tone photoresist exhibits very high chemical resistance compared to positive tone resist used mainly so far. [3,7] Negative tone resist offers higher resolution enabling the creation of better-defined templates and increases the possible height of the templates. [20] Furthermore, negative-tone Electrodeposition in combination with templates created by two-photon lithography is used to fabricate dense metallic 3D microcomponents. Nanocrystalline nickel microcomponents deposited from nickel sulfamate electrolyte in 3D templates are presented. Using 3D electrodeposition simulation, different template designs for a bridge-like microcomponent are investigated. The influence of the template design on cur...

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Additive manufacturing of 3D nano-architected metals

Cited by 435 publications

References 49 publications

The role of defects in dictating the strength of brittle honeycombs made by rapid prototyping

The role of defects in dictating the strength of brittle honeycombs made by rapid prototyping

A novel layered topology of auxetic materials based on the tetrachiral honeycomb microstructure

Additive Manufacturing through Galvanoforming of 3D Nickel Microarchitectures: Simulation‐Assisted Synthesis

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