scholarly journals A new tunable elastic metamaterial structure for manipulating band gaps/wave propagation

2021 ◽  
Vol 42 (11) ◽  
pp. 1543-1554
Author(s):  
Zhenyu Wang ◽  
Zhaoyang Ma ◽  
Xingming Guo ◽  
Dongsheng Zhang
Keyword(s):  
Wave Propagation ◽  
Shape Memory ◽  
Structural Parameters ◽  
Shape Memory Polymer ◽  
Band Gaps ◽  
Negative Mass ◽  
Specific Frequency ◽  
Stiffness Variation ◽  
Relationship Of ◽  
The Continuum

AbstractA one-dimensional mechanical lattice system with local resonators is proposed as an elastic metamaterial model, which shows negative mass and negative modulus under specific frequency ranges. The proposed representative units, consisting of accurately arranged rigid components, can generate controllable translational resonance and achieve negative mass and negative modulus by adjusting the local structural parameters. A shape memory polymer is adopted as a spring component, whose Young’s modulus is obviously affected by temperature, and the proposed metamaterials’ tunable ability is achieved by adjusting temperature. The effect of the shape memory polymer’s stiffness variation on the band gaps is investigated detailedly, and the special phenomenon of intersecting dispersion curves is discussed, which can be designed and controlled by adjusting temperature. The dispersion relationship of the continuum metamaterial model affected by temperature is obtained, which shows great tunable ability to manipulate wave propagation.

Investigation of intelligent reversible diaphragm using shape memory polymers

2017 ◽  
Vol 29 (7) ◽  
pp. 1500-1509 ◽  
Author(s):  
Ran Tao ◽  
Qing-Sheng Yang ◽  
Xia Liu ◽  
Xiao-Qiao He ◽  
Kim-Meow Liew
Keyword(s):  
Shape Memory ◽  
Strain Energy ◽  
Structural Parameters ◽  
Shape Memory Polymer ◽  
Three Dimensional ◽  
Nonlinear Finite Element Method ◽  
Three Dimensional Model ◽  
Initial State ◽  
Whole Process ◽  
Propellant Tank

This article describes design and analysis of a novel reversible diaphragm using shape memory polymer. The reversible diaphragm could be applied to space engineering, such as propellant tank of rocket. The shape memory polymer diaphragm can automatically recover to the initial state after the overturning deformation and thus can be used repeatedly. A three-dimensional model is established to study the overturning and recovery behavior of the shape memory polymer diaphragm.The nonlinear finite element method based on the thermodynamic constitutive equations of shape memory polymer is used to obtain pressure -displacement relations and strain energy variation of SMP diaphragm with approximately hemispherical shape in the whole process of the overturning deformation. The influence of structural parameters and temperature on the overturning and recover behavior is discussed.

Multi-Scale Analysis of Thermo-Mechanical Properties of 2.5D Angle-Interlock Woven Shape Memory Polymer Composites

2018 ◽  
Vol 35 (4) ◽  
pp. 475-486
Author(s):  
H. Y. Sun ◽  
J. P. Gu ◽  
Y. Tang ◽  
Z. M. Xie
Keyword(s):  
Mechanical Properties ◽  
Shape Memory ◽  
Polymer Composites ◽  
Shape Memory Polymer ◽  
Small Strain ◽  
Constitutive Relationship ◽  
Nonlinear Fitting ◽  
Multi Scale ◽  
Hereditary Integral ◽  
Relationship Of

ABSTRACTA multi-scale strategy is employed in the paper to investigate the thermo-mechanical properties of 2.5D angle-interlock woven shape memory polymer composites (SMPCs). In the study, the mesoscopic model of 2.5D woven SMPCs and microscopic model of yarns are firstly developed. After that, the themo-viscoelastic constitutive relationship of the yarn is described in the form of hereditary integral and the parameters of relaxation moduli are obtained from nonlinear fitting of Prony series based on the results of finite element method (FEM). Based on the multi-scale models and the constitutive relationship, the effects of warp and weft arranged densities on viscoelastic properties of 2.5D woven SMPCs are studied in detail. Finally, the shape memory behavior along the warp direction in small strain region is also analyzed. The research in the paper lays a foundation for design and application of woven SMPCs in engineering.

Possible Operation of Periodically Layered Nanocrystalline Porous Silicon as an Acoustic Band Crystal Device

2004 ◽  
Vol 832 ◽  
Author(s):  
Akira Kiuchi ◽  
Bernard Gelloz ◽  
Akira Kojima ◽  
Nobuyoshi Koshida
Keyword(s):  
Wave Propagation ◽  
Porous Silicon ◽  
Acoustic Wave ◽  
Elastic Constant ◽  
Elastic Properties ◽  
Structural Parameters ◽  
Band Gaps ◽  
Acoustic Wave Propagation ◽  
Calculation Results ◽  
Low Porosity

ABSTRACTIt is shown that the periodic stacked structures of nanocrystalline porous silicon (nc-PS) layers with controlled densities and elastic properties act as an acoustic band crystal (ABC) device. Supposing that the periodic nc-PS layers are formed by conventional modulated anodization technique to fabricate the multi-layered distributed Brag reflection mirror, the acoustic wave propagation modes are investigated theoretically for various structural parameters. According to the calculation results, a significant acoustic band gaps are generated in the ultrasonic regions due to a big contrast in the elastic constant produced between low-porosity and compact nc-PS layers. The propagation of acoustic wave can be completely suppressed in the characteristic band determined from designed parameters. The present result suggests further possibility of the nc-PS layer as a key component of ABC devices.

Study on Thermo-Mechanical Behaviors of Shape Memory Polymer

2009 ◽  
Vol 419-420 ◽  
pp. 497-500 ◽  
Author(s):  
Bo Zhou ◽  
Yan Ju Liu ◽  
Jin Song Leng ◽  
Tao Li
Keyword(s):  
Glass Transition ◽  
Shape Memory ◽  
Material Parameter ◽  
Shape Memory Polymer ◽  
Tensile Tests ◽  
Mechanical Analysis ◽  
New Material ◽  
Strain Relationship ◽  
Relationship Of ◽  
Parameter Function

Dynamic mechanical analysis (DMA) tests are conducted on styrene-based shape memory polymer(SMP) to investigate its glass transition behaviors. The tensile tests at various temperatures are operated to detect the stress-strain relationship of styrene-based SMP. The material elastic moduli and yielding limits at 25oC, 30oC, 40oC, and 50oC are determined according to the results of tensile test. A new material parameter function is supposed to express the glass transition behavior of styrene-based SMP. The shape memory thermo-mechanical cycle of styrene-based SMP is numerically simulated by Tobushi’s constitutive equation coupled with the new material parameter function. Numerical results show the new material parameter function can express the thermo-mechanical properties of styrene-based SMP effectively.

scholarly journals Design of Shape Memory Thermoplastic Material Systems for FDM-Type Additive Manufacturing

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4254
Author(s):  
Paulina A. Quiñonez ◽  
Leticia Ugarte-Sanchez ◽  
Diego Bermudez ◽  
Paulina Chinolla ◽  
Rhyan Dueck ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Shape Memory ◽  
Thermomechanical Processing ◽  
Material Selection ◽  
Shape Memory Polymer ◽  
Fused Filament Fabrication ◽  
Materials Development ◽  
Thermoplastic Material ◽  
Polymer Systems ◽  
Injection Molded

The work presented here describes a paradigm for the design of materials for additive manufacturing platforms based on taking advantage of unique physical properties imparted upon the material by the fabrication process. We sought to further investigate past work with binary shape memory polymer blends, which indicated that phase texturization caused by the fused filament fabrication (FFF) process enhanced shape memory properties. In this work, two multi-constituent shape memory polymer systems were developed where the miscibility parameter was the guide in material selection. A comparison with injection molded specimens was also carried out to further investigate the ability of the FFF process to enable enhanced shape memory characteristics as compared to other manufacturing methods. It was found that blend combinations with more closely matching miscibility parameters were more apt at yielding reliable shape memory polymer systems. However, when miscibility parameters differed, a pathway towards the creation of shape memory polymer systems capable of maintaining more than one temporary shape at a time was potentially realized. Additional aspects related to impact modifying of rigid thermoplastics as well as thermomechanical processing on induced crystallinity are also explored. Overall, this work serves as another example in the advancement of additive manufacturing via materials development.

Autonomous Off‐Equilibrium Morphing Pathways of a Supramolecular Shape‐Memory Polymer

2021 ◽  
pp. 2102473
Author(s):  
Wenjun Peng ◽  
Guogao Zhang ◽  
Qian Zhao ◽  
Tao Xie
Keyword(s):  
Shape Memory ◽  
Shape Memory Polymer

scholarly journals Plasmonic hot-electron photodetection with quasi-bound states in the continuum and guided resonances

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wenhao Wang ◽  
Lucas V. Besteiro ◽  
Peng Yu ◽  
Feng Lin ◽  
Alexander O. Govorov ◽  
...  
Keyword(s):  
Bound States ◽  
Structural Parameters ◽  
Hybrid Structure ◽  
Fine Tuning ◽  
Hot Electrons ◽  
Hot Electron ◽  
Perfect Absorption ◽  
High Loss ◽  
Guided Mode ◽  
The Continuum

Abstract Hot electrons generated in metallic nanostructures have shown promising perspectives for photodetection. This has prompted efforts to enhance the absorption of photons by metals. However, most strategies require fine-tuning of the geometric parameters to achieve perfect absorption, accompanied by the demanding fabrications. Here, we theoretically propose a Ag grating/TiO2 cladding hybrid structure for hot electron photodetection (HEPD) by combining quasi-bound states in the continuum (BIC) and plasmonic hot electrons. Enabled by quasi-BIC, perfect absorption can be readily achieved and it is robust against the change of several structural parameters due to the topological nature of BIC. Also, we show that the guided mode can be folded into the light cone by introducing a disturbance to become a guided resonance, which then gives rise to a narrow-band HEPD that is difficult to be achieved in the high loss gold plasmonics. Combining the quasi-BIC and the guided resonance, we also realize a multiband HEPD with near-perfect absorption. Our work suggests new routes to enhance the light-harvesting in plasmonic nanosystems.

scholarly journals Pressure Orientation-Dependent Recovery of 3D-Printed PLA Objects with Varying Infill Degree

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1275 ◽  
Author(s):  
Guido Ehrmann ◽  
Andrea Ehrmann
Keyword(s):  
Shape Memory ◽  
Fused Deposition Modeling ◽  
Static Load ◽  
Shape Memory Polymer ◽  
Applied Pressure ◽  
Poly Lactic Acid ◽  
Fused Deposition ◽  
Deposition Modeling ◽  
Load Tests ◽  
3D Printed

Poly(lactic acid) is not only one of the most often used materials for 3D printing via fused deposition modeling (FDM), but also a shape-memory polymer. This means that objects printed from PLA can, to a certain extent, be deformed and regenerate their original shape automatically when they are heated to a moderate temperature of about 60–100 °C. It is important to note that pure PLA cannot restore broken bonds, so that it is necessary to find structures which can take up large forces by deformation without full breaks. Here we report on the continuation of previous tests on 3D-printed cubes with different infill patterns and degrees, now investigating the influence of the orientation of the applied pressure on the recovery properties. We find that for the applied gyroid pattern, indentation on the front parallel to the layers gives the worst recovery due to nearly full layer separation, while indentation on the front perpendicular to the layers or diagonal gives significantly better results. Pressing from the top, either diagonal or parallel to an edge, interestingly leads to a different residual strain than pressing from front, with indentation on top always firstly leading to an expansion towards the indenter after the first few quasi-static load tests. To quantitatively evaluate these results, new measures are suggested which could be adopted by other groups working on shape-memory polymers.

scholarly journals Loading Performance of a Novel Shearer Drum Applied to Thin Coal Seams

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 358
Author(s):  
Kuidong Gao ◽  
Xiaodi Zhang ◽  
Liqing Sun ◽  
Qingliang Zeng ◽  
Zhihai Liu
Keyword(s):  
Rotational Speed ◽  
Production Efficiency ◽  
Loading Rate ◽  
Positive Impact ◽  
Structural Parameters ◽  
Helix Angle ◽  
Structure Design ◽  
Coal Seams ◽  
Coal Particles ◽  
Relationship Of

The poor loading performance of shearer drums restricts the development and production efficiency of coal in thin coal seams. Changing operation and structural parameters can improve the drum’s loading performance to some extent, but the effect is not obvious. A two-segment differential rotational speed drum (TDRSD) was proposed after analyzing the drum’s influence mechanism on coal particles. To further reveal the drum’s coal loading principle, the velocity, particles distribution, and loading rate were analyzed. The effect of the matching relationship of the rotational speed and helix angle between the front and rear drum are also discussed. The results show that a lower front drum rotational speed had a positive impact on improving the loading performance, and the loading rate first increases and then decreases with the increase in rear drum rotational speed. The optimal loading performance was obtained in the range 60–67.5 rpm. The front drum’s helix angle had no evident effect on loading performance, and the loading rate increase with the increase in the rear drum’s helix angle. The results provide a reference and guidance for operation parameters selection, structure design, and drum optimization.

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