Shape-Morphing Space Frame (SMSF) Using Quadrilateral Bistable Unit-Cell Elements

2016 ◽  
Author(s):  
Ahmad Alqasimi ◽  
Craig Lusk
Keyword(s):  
Unit Cell ◽  
Design Stage ◽  
Proof Of Concept ◽  
Space Frame ◽  
Initial Shape ◽  
Shape Morphing ◽  
Disk Structure ◽  
Lower Hemisphere ◽  
Unit Cells ◽  
Shape Sphere

This paper presents a new concept: a Shape-Morphing Space Frame (SMSF) using quadrilateral bistable unit-cell elements. The unit-cells are composed of either eight-bar or seven-bar mechanisms in which design constraints, system of elimination and graph theory are used to design, as a proof of concept, a disk like structure with the ability to morph into a sphere. Or specifically, the circumference of a disk structure is approximated by a ten-sided polygon that would then morph into a hollow sphere structure that is approximated by 60-sided polyhedron. The disk-to-sphere structure is tessellated into ten sides for the latitudes circles and 12 sides for the longitude circles; the disk’s thickness and radius are chosen at the design stage. The strategy in morphing the initial shape of the structure (disk) into its final shape (sphere) is that the radial lines on the surface of the disk bend but do not stretch, whereas the circumferential lines compress. Moreover, the radial lines on the disk become longitude lines on the sphere and the circumferential lines become latitude lines on the sphere. The disk’s thickness splits in half, the upper half becomes the thickness of the upper hemisphere and the lower half becomes the thickness of the lower hemisphere. The concept was successfully prototyped and actuation forces were measured.

An Antagonistic Flexural Unit Cell for Design of Shape Morphing Structures

Aerospace ◽  
2004 ◽  
Author(s):  
Aarash Y. N. Sofla ◽  
Dana M. Elzey ◽  
Haydn N. G. Wadley
Keyword(s):  
Shape Memory ◽  
Unit Cell ◽  
External Energy ◽  
Full Characterization ◽  
Shape Morphing ◽  
Cyclic Operation ◽  
Unit Cells ◽  
External Forces ◽  
Reversed Cyclic

An antagonistic flexural unit cell (AFC) concept for the design and fabrication of novel 2-D and 3-D lightweight shape morphing structures is introduced. A fully reversible flexural shape changing cell utilizing opposing one-way shape memory alloy (SMA) actuators is shown to require no spring-like bias elements. The SMA actuating elements are arranged such that the actuation (contraction) of one of them stretches the other one in the cell, preparing it to be actuated later to reverse a flexural displacement. This antagonistic operation allows fully reversed cyclic operation. The focus of this paper is an assessment of performance at the single cell level. The cell logically provides four possible configurations in different stages of its cycle. Two of them are of particular interest because they provide two different fixed shapes for the cell that can be maintained without the continuous supply of external energy. The final deformations of the cell and equilibrium stresses in the SMA elements depend on the amount of stored shape memory strain in each element, external forces and cell geometry. A model is developed, which allows a full characterization of the AFC. The model is used to study NiTi SMA-based AFCs and the results are therefore directly applicable to the design of shape morphing structures using such unit cells.

Fabrication and Testing of Kirigami-Inspired Multi-Stable Composites

2018 ◽  
Author(s):  
Aditya Lele ◽  
Oliver J. Myers ◽  
Suyi Li
Keyword(s):  
Composite Laminates ◽  
Adaptive Systems ◽  
Unit Cell ◽  
Proof Of Concept ◽  
Stable States ◽  
Shape Morphing ◽  
Powerful Approach ◽  
Simple Deformation ◽  
Multiple Stable States ◽  
Adaptive Composites

This paper aims at highlighting the fabrication procedures and proof-of-concept tests of a Kirigami inspired multi-stable composite laminate. Bistable composites consisting of asymmetric fiber layout have shown great potentials for shape morphing and energy harvesting applications. However, a patch of such a bistable composite is limited to very simple deformation when being snapped between its two stable equilibria (or states). To address this issue, this study investigates the idea of utilizing Kirigami, the ancient art of paper cutting, into the design and fabrication of bistable composite laminates. Via combining multiple patches of laminates and cutting according to prescribed Kirigami pattern, one can create a structure with multiple stable states and sophisticated deformation paths between them. This can significantly expand the application potentials of the multi-stable composites. This paper details the fabrication procedures for an elementary unit cell in the envisioned Kirigami composite and the results of proof-of-concept experiments, which measure the force required to switch the Kirigami composite between its different stable states. Preliminary results confirm that the Kirigami unit cell possesses multiple stable states depending on the underlying fiber layout. Each patch in the Kirigami composite could be snapped independently between stable states without triggering any undesired snapping in other patches. Moreover, a transient propagation of curvature change is observed when a patch in the Kirigami composite is snapped between its stable states. Such a phenomenon has not been reported in the bistable composite studies before. Results of this paper indicate that Kirigami is a powerful approach for designing and fabricating multi-stable composites with a strong appeal for morphing and adaptive systems. This paper highlights the feasibility and novelty of combining Kirigami art and bistable adaptive composites.

Shape-Morphing Space Frame (SMSF) Using Linear Bistable Elements

2015 ◽  
Author(s):  
Ahmad Alqasimi ◽  
Craig Lusk
Keyword(s):  
Cylindrical Shell ◽  
Single Layer ◽  
The Other ◽  
Design Parameters ◽  
Cylindrical Shape ◽  
Space Frame ◽  
Initial Shape ◽  
Initial Height ◽  
Shape Morphing ◽  
Space Frames

This paper presents a new concept: a Shape-Morphing Space Frame (SMSF), which is a novel application utilizing the Linear Bistable Compliant Crank-Slider Mechanism (LBCCSM). The frame’s initial shape is constructed from a single-layer grid of flexures, rigid links and LBCCSMs. The grid is bent into the space frame’s initial cylindrical shape, which can morph because of the inclusion of LBCCSMs in its structure. The design parameters consist of the frame’s initial height, its tessellation pattern (including bistable elements’ placement), its initial diameter, and the final desired shape. The method used in placing the bistable elements is a novel contribution to this work as it considers the principle stress trajectories. This paper will present two different examples of Shape-Morphing Space Frames, each starting from a cylindrical-shell space frame and morphing, one to a hyperbolic-shell space frame and the other to a spherical-shell space frame, both morphing by applying moments, which shear the cylindrical shell, and forces, which change the cylinder’s radius using Poisson’s effect.

Variations of In-Plane Mechanical Properties of Cellular Structures With Different Hierarchical Organizations

2020 ◽  
Author(s):  
Souvik Chakraborty ◽  
Dylan Hebert ◽  
Tanvir Rahman Faisal
Keyword(s):  
Mechanical Properties ◽  
Cell Wall ◽  
Hierarchical Structure ◽  
Unit Cell ◽  
Cellular Structures ◽  
Initial Shape ◽  
Unit Cells ◽  
Cell Topology ◽  
Homogeneous Cell ◽  
Hierarchical Organizations

Abstract Inspired by the nature, this study analyzes in-plane compressive responses of different modes of hierarchical architected structures with varying topologies. Architected cellular structures with two different unit cell topologies — square and kagome are considered, both having a relative density of 0.25. Each unit cell topology is designed with three different configurations. The base structure is the primitive one with solid homogeneous cell wall. The nested hierarchical structure is derived from the primitive one with cellular structuring in the cell wall. The third and final one is the fractal-like hierarchical structure, where same unit cells appear on different length scales. 3D printed structures were subjected to uniaxial compression to characterize their in-plane mechanical properties. The compressive stress-strain behaviors reveal that all the structures demonstrate the classical behavior of cellular structures followed by significant recovery of their initial shape upon load withdrawal. The energy absorptions demonstrated by the plateau regions before densification are not only governed by their structural topologies, but also largely governed by the configurations of hierarchical organizations. Hence, this study suggests the application specific design of hierarchical architected structures for defined loading conditions.

Bayesian removal of noise for increased sensitivity in vector pattern recognition lattice imaging of interfaces

1993 ◽  
Vol 51 ◽  
pp. 994-995
Author(s):  
L. Fei ◽  
P. Fraundorf
Keyword(s):  
Pattern Recognition ◽  
Perfect Crystal ◽  
Unit Cell ◽  
Ion Milling ◽  
Beam Radiation ◽  
Major Interest ◽  
Unit Cells ◽  
Mapping Process ◽  
Increased Sensitivity ◽  
Electron Microscopes

Interface structure is of major interest in microscopy. With high resolution transmission electron microscopes (TEMs) and scanning probe microscopes, it is possible to reveal structure of interfaces in unit cells, in some cases with atomic resolution. A. Ourmazd et al. proposed quantifying such observations by using vector pattern recognition to map chemical composition changes across the interface in TEM images with unit cell resolution. The sensitivity of the mapping process, however, is limited by the repeatability of unit cell images of perfect crystal, and hence by the amount of delocalized noise, e.g. due to ion milling or beam radiation damage. Bayesian removal of noise, based on statistical inference, can be used to reduce the amount of non-periodic noise in images after acquisition. The basic principle of Bayesian phase-model background subtraction, according to our previous study, is that the optimum (rms error minimizing strategy) Fourier phases of the noise can be obtained provided the amplitudes of the noise is given, while the noise amplitude can often be estimated from the image itself.

scholarly journals Prediction of Effective Thermal Conductivities of Four-Directional Carbon/Carbon Composites by Unit Cells with Different Sizes

2021 ◽  
Vol 11 (3) ◽  
pp. 1171
Author(s):  
Chang Xu ◽  
Zhihong Sun ◽  
Guowei Shao
Keyword(s):  
Carbon Fiber ◽  
Longitudinal Direction ◽  
Unit Cell ◽  
Carbon Composites ◽  
Temperature Boundary ◽  
The Matrix ◽  
Unit Cells ◽  
Experimental Values ◽  
Different Diameters ◽  
Thermal Conductivities

Two-unit cells developed to predict the effective thermal conductivities of four-directional carbon/carbon composites with the finite element method are proposed in this paper. The smaller-size unit cell is formulated from the larger-size unit cell by two 180° rotational transformations. The temperature boundary conditions corresponding to the two-unit cells are derived, and the validity is verified by the temperature and heat flux distributions at specific positions of the larger-size unit cell and the smaller-size unit cell. The thermal conductivities of the carbon fiber bundles and carbon fiber rods are measured firstly. Then, combined with the properties of the matrix, the effective thermal conductivities of the four-directional carbon/carbon composites are numerically predicted. The results in transverse direction predicted by the larger-size unit cell and the smaller-size unit cell are both higher than experimental values, which are 5.8 to 6.2% and 7.3 to 8.2%, respectively. In longitudinal direction, the calculated thermal conductivities of the larger-size unit cell and the smaller-size unit cell are 6.8% and 6.2% higher than the experimental results, respectively. In addition, carbon fiber rods with different diameters are set to clarify the influence on the effective thermal conductivities of the four-directional carbon/carbon composites.

scholarly journals A Multiband Antenna Stacked with Novel Metamaterial SCSRR and CSSRR for WiMAX/WLAN Applications

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 113
Author(s):  
Rajiv Mohan David ◽  
Mohammad Saadh AW ◽  
Tanweer Ali ◽  
Pradeep Kumar
Keyword(s):  
Split Ring Resonator ◽  
Unit Cell ◽  
Ring Resonators ◽  
Split Ring ◽  
Medium Theory ◽  
High Frequency Structure Simulator ◽  
Dimension Analysis ◽  
Unit Cells ◽  
Coaxial Feed ◽  
Triple Band

This paper presents an innovative method for the design of a triple band meta-mode antenna. This unique design of antenna finds application in a particular frequency band of WLAN and WiMAX. This antenna comprises of a square complimentary split ring resonator (SCSRR), a coaxial feed, and two symmetrical comb shaped split ring resonators (CSSRR). The metamaterial unit cell SCSRR independently gains control in the band range 3.15–3.25 GHz (WiMAX), whereas two symmetrical CSSRR unit cell controls the band in the ranges 3.91–4.01 GHz and 5.79–5.94 GHz (WLAN). This design methodology and the study of the suggested unit cells structure are reviewed in classical waveguide medium theory. The antenna has a miniaturized size of only 0.213λ0 × 0.192λ0 × 0.0271λ0 (20 × 18 × 2.54 mm3, where λ0 is the free space wavelength at 3.2 GHz). The detailed dimension analysis of the proposed antenna and its radiation efficiency are also presented in this paper. All the necessary simulations are carried out in High Frequency Structure Simulator (HFSS) 13.0 tool.

scholarly journals Dynamic crushing behavior of closed-cell aluminum foams based on different space-filling unit cells

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
S. Talebi ◽  
R. Hedayati ◽  
M. Sadighi
Keyword(s):  
Surface Area ◽  
Dynamic Behavior ◽  
Energy Absorption ◽  
Peak Stress ◽  
Absorption Capacity ◽  
Unit Cell ◽  
Lattice Structures ◽  
Energy Absorption Capacity ◽  
Closed Cell ◽  
Unit Cells

AbstractClosed-cell metal foams are cellular solids that show unique properties such as high strength to weight ratio, high energy absorption capacity, and low thermal conductivity. Due to being computation and cost effective, modeling the behavior of closed-cell foams using regular unit cells has attracted a lot of attention in this regard. Recent developments in additive manufacturing techniques which have made the production of rationally designed porous structures feasible has also contributed to recent increasing interest in studying the mechanical behavior of regular lattice structures. In this study, five different topologies namely Kelvin, Weaire–Phelan, rhombicuboctahedron, octahedral, and truncated cube are considered for constructing lattice structures. The effects of foam density and impact velocity on the stress–strain curves, first peak stress, and energy absorption capacity are investigated. The results showed that unit cell topology has a very significant effect on the stiffness, first peak stress, failure mode, and energy absorption capacity. Among all the unit cell types, the Kelvin unit cell demonstrated the most similar behavior to experimental test results. The Weaire–Phelan unit cell, while showing promising results in low and medium densities, demonstrated unstable behavior at high impact velocity. The lattice structures with high fractions of vertical walls (truncated cube and rhombicuboctahedron) showed higher stiffness and first peak stress values as compared to lattice structures with high ratio of oblique walls (Weaire–Phelan and Kelvin). However, as for the energy absorption capacity, other factors were important. The lattice structures with high cell wall surface area had higher energy absorption capacities as compared to lattice structures with low surface area. The results of this study are not only beneficial in determining the proper unit cell type in numerical modeling of dynamic behavior of closed-cell foams, but they are also advantageous in studying the dynamic behavior of additively manufactured lattice structures with different topologies.

scholarly journals TOWARDS A VERIFICATION AND VALIDATING TESTING FRAMEWORK TO DEVELOP BESPOKE MEDICAL PRODUCTS IN RESEARCH-FUNDED PROJECTS

2021 ◽  
Vol 1 ◽  
pp. 3199-3208
Author(s):  
Emanuel Balzan ◽  
Pierre Vella ◽  
Philip Farrugia ◽  
Edward Abela ◽  
Glenn Cassar ◽  
...  
Keyword(s):  
Medical Devices ◽  
Early Stage ◽  
Design Stage ◽  
Concept Design ◽  
Proof Of Concept ◽  
Detailed Design ◽  
Testing Framework ◽  
Medical Products ◽  
Manufacturing Technologies ◽  
Validation Testing

AbstractResearch funded projects are often concerned with the development of proof-of-concept products. Consequently, activities related to verification and validation testing (VVT) are often not considered in depth, even though various design iterations are carried out to refine an idea. Furthermore, the introduction of additive manufacturing (AM) has facilitated, in particular, the development of bespoke medical products. End bespoke products, which will be used by relevant stakeholders (e.g. patients and clinicians) are fabricated with the same manufacturing technologies used during prototyping. As a result, the detailed design stage of products fabricated by AM is much shorter. Therefore, to improve the market-readiness of bespoke medical devices, testing must be integrated within the development from an early stage, allowing better planning of resources. To address these issues, in this paper, a comprehensive VVT framework is proposed for research projects, which lack a VVT infrastructure. The framework builds up on previous studies and methods utilised in industry to enable project key experts to capture risks as early as the concept design stage.

The Influence of Multiple Inclusions on the Cauchy Stress of a Spherical Particle-Reinforced Composite Under Uniaxial Loading

2014 ◽  
Author(s):  
Ke Niu ◽  
Armin Abedini ◽  
Zengtao Chen
Keyword(s):  
Spherical Particle ◽  
Single Particle ◽  
Volume Fraction ◽  
Unit Cell ◽  
Spherical Particles ◽  
Uniaxial Tensile ◽  
Cauchy Stress ◽  
Particle Volume ◽  
Volume Fractions ◽  
Unit Cells

This paper investigates the influence of multiple inclusions on the Cauchy stress of a spherical particle-reinforced metal matrix composite (MMC) under uniaxial tensile loading condition. The approach of three-dimensional cubic multi-particle unit cell is used to investigate the 15 non-overlapping identical spherical particles which are randomly distributed in the unit cell. The coordinates of the center of each particle are calculated by using the Random Sequential Adsorption algorithm (RSA) to ensure its periodicity. The models with reinforcement volume fractions of 10%, 15%, 20% and 25% are evaluated by using the finite element method. The behaviour of Cauchy stress for each model is analyzed at a far-field strain of 5%. For each reinforcement volume fraction, four models with different particle spatial distributions are evaluated and averaged to achieve a more accurate result. At the same time, single-particle unit cell and analytical model were developed. The stress-strain curves of multi-particle unit cells are compared with single-particle unit cells and the tangent homogenization model coupled with the Mori-Tanaka method. Only little scatters were found between unit cells with the same particle volume fractions. Multi-particle unit cells predict higher response than single particle unit cells. As the volume fraction of reinforcements increases, the Cauchy stress of MMCs increases.

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