Elastic Wave Propagation of Two-Dimensional Metamaterials Composed of Auxetic Star-Shaped Honeycomb Structures

Chang, Shu Yeh; Chen, Chung De; Yeh, Jia Yi; Chen, Lien Wen

doi:10.3390/cryst9030121

Cited by 20 publications

(5 citation statements)

References 34 publications

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“…The structure, also, exhibits auxetic or zero Poisson’s ratio for mechanical applications (Mizzi et al , 2018, Fong et al , 2023) and for reversible energy absorption (Hamzehei et al , 2022). The star-shaped structures have also been demonstrated to exhibit negative refraction and self-collimation for applications in phononic crystals (vibration isolation and elastic waveguide) (Chang et al , 2019, Zhang et al , 2023), as well as tunable high and low frequency plane wave attenuation properties (Xin et al , 2021). These metamaterials have been fabricated through 3D printing technology such as FFF and their structural properties strongly depend on the 3D printing conditions (Chen and Lee, 2022).…”

Section: Introductionmentioning

confidence: 99%

Optimisation of printing parameters of fused filament fabrication and uniaxial compression failure analysis for four-point star-shaped structures

Wambua,

Mwema,

Akinlabi

et al. 2024

RPJ

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Purpose The purpose of this paper is to present an optimisation of four-point star-shaped structures produced through additive manufacturing (AM) polylactic acid (PLA). The study also aims to investigate the compression failure mechanism of the structure. Design/methodology/approach A Taguchi L9 orthogonal array design of the experiment is adopted in which the input parameters are resolution (0.06, 0.15 and 0.30 mm), print speed (60, 70 and 80 mm/s) and bed temperature (55°C, 60°C, 65°C). The response parameters considered were printing time, material usage, compression yield strength, compression modulus and dimensional stability. Empirical observations during compression tests were used to evaluate the load–response mechanism of the structures. Findings The printing resolution is the most significant input parameter. Material length is not influenced by the printing speed and bed temperature. The compression stress–strain curve exhibits elastic, plateau and densification regions. All the samples exhibit negative Poisson’s ratio values within the elastic and plateau regions. At the beginning of densification, the Poisson’s ratios change to positive values. The metamaterial printed at a resolution of 0.3 mm, 80 mm/s and 60°C exhibits the best mechanical properties (yield strength and modulus of 2.02 and 58.87 MPa, respectively). The failure of the structure occurs through bending and torsion of the unit cells. Practical implications The optimisation study is significant for decision-making during the 3D printing and the empirical failure model shall complement the existing techniques for the mechanical analysis of the metamaterials. Originality/value To the best of the authors’ knowledge, for the first time, a new empirical model, based on the uniaxial load response and “static truss concept”, for failure mechanisms of the unit cell is presented.

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Section: Introductionmentioning

confidence: 99%

Optimisation of printing parameters of fused filament fabrication and uniaxial compression failure analysis for four-point star-shaped structures

Wambua,

Mwema,

Akinlabi

et al. 2024

RPJ

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“…Ellipse and square shapes of inclusions are designed and optimized to achieve the self‐collimation PnCs, 17,18 and the influences of aspect ratio and tilt angle of inclusions on the self‐collimation effect are also studied 18 . Some other novel configurations, such as the star‐shaped honeycomb type, 19 are also studied for realizing the self‐collimation characteristics. Jo et al 16 studied the material property requirement for self‐collimation of S 0 Lamb waves and designed the self‐collimating PnCs over a broad range of frequencies which is verified by simulation and experiment.…”

Section: Introductionmentioning

confidence: 99%

Topology optimization for realizing tailored self‐collimation in phononic crystals

Jia

Luo

Takezawa

et al. 2022

Numerical Meth Engineering

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Self‐collimation is a phenomenon that the waves propagate through a narrow channel in phononic crystals (PnCs) without diffusion. Although different self‐collimation PnCs configurations have been proposed with heuristic methods, it is still challenging to achieve a frequency‐specified self‐collimation. We propose a systematic topology optimization method to find the material distribution in PnCs for realizing a frequency‐specified self‐collimation within a wider incident wave angle range. To achieve the self‐collimation effect, the weighted slope index of equi‐frequency contours (EFCs) that effectively measures whether the wave propagation has a self‐collimation effect is introduced as the objective function of the optimization model. The material‐field series expansion (MFSE) technique is used to describe the complicated topologies of the unit cell with a low number of design variables. Then, the Kriging‐based optimization algorithm with a self‐adaptive strategy is adopted for solving the optimization problem. Numerical examples show that the optimized unit cell designs have flat EFCs within larger incident wave angle ranges and also demonstrate that the expected nondiffraction propagation characteristics can be achieved through optimization.

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“…Unsurprisingly, many mechanical metamaterials can be considered as successors of cellular materials [ 14 , 15 ]. Indeed, the unconventional properties of mechanical [ 16 , 17 , 18 ], elastic [ 19 , 20 , 21 , 22 , 23 ], and acoustic metamaterials [ 24 , 25 ] originate in their intrinsic periodicity, along with the rational design of unit cells.…”

Section: Introductionmentioning

confidence: 99%

The Emergence of Sequential Buckling in Reconfigurable Hexagonal Networks Embedded into Soft Matrix

2021

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The extreme and unconventional properties of mechanical metamaterials originate in their sophisticated internal architectures. Traditionally, the architecture of mechanical metamaterials is decided on in the design stage and cannot be altered after fabrication. However, the phenomenon of elastic instability, usually accompanied by a reconfiguration in periodic lattices, can be harnessed to alter their mechanical properties. Here, we study the behavior of mechanical metamaterials consisting of hexagonal networks embedded into a soft matrix. Using finite element analysis, we reveal that under specific conditions, such metamaterials can undergo sequential buckling at two different strain levels. While the first reconfiguration keeps the periodicity of the metamaterial intact, the secondary buckling is accompanied by the change in the global periodicity and formation of a new periodic unit cell. We reveal that the critical strains for the first and the second buckling depend on the metamaterial geometry and the ratio between elastic moduli. Moreover, we demonstrate that the buckling behavior can be further controlled by the placement of the rigid circular inclusions in the rotation centers of order 6. The observed sequential buckling in bulk metamaterials can provide additional routes to program their mechanical behavior and control the propagation of elastic waves.

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Elastic Wave Propagation of Two-Dimensional Metamaterials Composed of Auxetic Star-Shaped Honeycomb Structures

Cited by 20 publications

References 34 publications

Optimisation of printing parameters of fused filament fabrication and uniaxial compression failure analysis for four-point star-shaped structures

Optimisation of printing parameters of fused filament fabrication and uniaxial compression failure analysis for four-point star-shaped structures

Topology optimization for realizing tailored self‐collimation in phononic crystals

The Emergence of Sequential Buckling in Reconfigurable Hexagonal Networks Embedded into Soft Matrix

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