scholarly journals Auxetic structures from 3D printed hybrid textiles

2021 ◽  
Vol 2 (1) ◽  
pp. 91-102
Author(s):  
Subin Shajoo ◽  
David Schmelzeisen ◽  
Christopher Pastore
Keyword(s):  
3D Printing ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Thermal Stimulus ◽  
New Materials ◽  
Textile Materials ◽  
Environmentally Responsive ◽  
Auxetic Structures ◽  
3D Printed

Auxetic structures have been produced using 3D printing and knitted textile materials. A review of other auxetic textiles is presented along with the new materials. A range of configurations were developed, prototyped, and tested to demonstrate significant auxetic response, including Poisson’s ratio up to negative one. The concept of 4D textiles was employed to create environmentally responsive hinges in some structures, allowing the material to change shape in response to thermal stimulus.

scholarly journals Impact Analysis of Auxetic Structures for Military Applications

2021 ◽  
Vol 9 (9) ◽  
pp. 2238-2249
Author(s):  
Rohit De
Keyword(s):  
3D Printing ◽  
Polyvinyl Chloride ◽  
Poisson’S Ratio ◽  
Impact Analysis ◽  
Poisson's Ratio ◽  
Suitable Material ◽  
Auxetic Structures ◽  
Explicit Dynamic ◽  
The Impact ◽  
Auxetic Structure

Abstract: Auxetic structures are special structures which tend to become wider when subjected to longitudinal tension instead of getting compressed, which implies structures having a negative poisson’s ratio. These structures are used in impact pads due to this unique property. In this comparative study were done on different types of materials and structures which are recognized for 3D printing the auxetic structures. The three stages of explicit dynamic analysis involves firstly selecting the most appropriate structures from chiral truss, re-entrant hexagon, arrow head and one non- auxetic structure which is hexagon structure. From this the structure having the least deformation at the impact point is selected which is re-entrant hexagon. Following this, keeping re-entrant hexagon as the structure, the next set of analysis is performed by varying the structure materials. Polycarbonate, polystyrene, polyvinyl chloride and high density polyethylene were studied and the analysis results showed, polyvinyl chloride as the suitable material. Lastly the limiting velocity for the impact is calculated by varying the impact velocity from 800m/s, 1000m/s and 1200m/s beyond which the structure experienced fracture. This study proposes the selection of suitable auxetic structure and material for manufacturing impact pads. Keywords: Auxetic structures, impact pads, indentation resistance, explicit dynamics, 3D printing, FDM, Poisson’s ratio

Behavior of Soft 3D-Printed Auxetic Structures Under Various Loading Conditions

2018 ◽  
Author(s):  
Mahmoud K. Ardebili ◽  
Kerim Tuna Ikikardaslar ◽  
Erik Chauca ◽  
Feridun Delale
Keyword(s):  
Poisson’S Ratio ◽  
Tensile Load ◽  
Geometric Parameters ◽  
Poisson's Ratio ◽  
Impact Loads ◽  
Negative Poisson’S Ratio ◽  
Auxetic Structures ◽  
Circular Holes ◽  
Negative Poisson's Ratio ◽  
3D Printed

Auxetic structures exhibiting non-linear deformation are a prevalent research topic in the material sciences due to their negative Poisson’s ratio. The auxetic behavior is most efficiently accomplished through buckling or hinging of 3d printed structures created with soft or flexible materials. These structures have been hypothesized to have some unique characteristics and may provide advantages over conventional engineering materials in certain applications. The objective of present study is to gain a better understanding of behavior of auxetic structures subjected to tensile, compressive and impact loads and assess geometric parameters affecting these structures in applications such as impact shielding or biomedicine. Analytical and experimental methods were employed to investigate two different types of auxetic structures which were 3d-printed with TPU (thermoplastic polyurethane). The first was based on symmetric re-entrant angles cells patterned to form sheet-like structure. Rotation of members in opposite directions in a cell induces negative Poisson’s ratio when the structure is subjected to tensile loading. The second structure was based on rectangular lattice of circular holes. This structure exhibited auxeticity due to formation of pattern of alternating mutually orthogonal ellipses when subjected to compressive and impact loads. Parameters of interest in this study included hardness of the plastic used in printing the structures, the fill pattern of 3d-printed solid parts, porosity of cylinders in the lattice structure, angles and thickness of members in the re-entrant structure. Preliminary results indicated that per unit weight of material, the re-entrant structure requires less tensile load to strain than a solid structure. This is advantageous in applications where expansion in lateral direction is required. The lattice of circular holes structure exhibited similar trend in impact and compressive loading. The results indicate that geometric parameters influence auxeticity of the structure a great deal. When the porosity of the lattice is too small, positive Poisson’s ratio is observed. The length to height ratio of the re-entrant cell has similar effect on the structure’s Poisson’s ratio. The main advantage gained by employing such structures is their overall ability to resist buckling and withstand impact load without cracking. This study will help to develop 3D-printing techniques in manufacturing better performing structures under similar conditions.

scholarly journals Design and Evaluation of 3D-Printed 4 Structures Coated By CWPU/Graphene as Strain Sensor: Truss, Honeycomb, Chiral Truss, Re-entrant

2021 ◽  
Author(s):  
Hyeong Yeol Choi ◽  
Eun Joo Shin ◽  
Sun Hee Lee
Keyword(s):  
Poisson’S Ratio ◽  
Thermoplastic Polyurethane ◽  
Strain Sensor ◽  
Dip Coating ◽  
Raw Material ◽  
Poisson's Ratio ◽  
Constant Change ◽  
Potential Applications ◽  
Auxetic Structures ◽  
3D Printed

Abstract A strain sensor characterized by elasticity has recently been studied in various ways to be applied to monitoring humans or robots. Here, 4 types of 3D-printed auxetic lattice structures using thermoplastic polyurethane (TPU) as raw material were characterized: truss and honeycomb with positive Poisson's ratio and chiral truss and re-entrant with negative Poisson's ratio. Each structure was fabricated as a flexible and stable strain sensor by coating graphene through a dip-coating process. The fabricated auxetic structures have excellent strength, flexibility, and electrical conductivity desirable for a strain sensor and detect a constant change in resistance at a given strain. The 3D-printed auxetic lattice 4 type structures coated with CWPU/Graphene suggest potential applications of multifunctional strain sensors under deformation.

scholarly journals Design of Shape Reconfigurable, Highly Stretchable Honeycomb Lattice With Tunable Poisson’s Ratio

2021 ◽  
Vol 8 ◽  
Author(s):  
Le Dong ◽  
Chengru Jiang ◽  
Jinqiang Wang ◽  
Dong Wang
Keyword(s):  
Theoretical Model ◽  
Ambient Temperature ◽  
Shape Memory ◽  
Poisson’S Ratio ◽  
Lattice Structure ◽  
Poisson's Ratio ◽  
Lattice Structures ◽  
Straight Beam ◽  
Highly Stretchable ◽  
3D Printed

The mechanical behaviors of lattice structures can be tuned by arranging or adjusting their geometric parameters. Once fabricated, the lattice’s mechanical behavior is generally fixed and cannot adapt to environmental change. In this paper, we developed a shape reconfigurable, highly stretchable lattice structure with tunable Poisson’s ratio. The lattice is built based on a hexagonal honeycomb structure. By replacing the straight beam with curled microstructure, the stretchability of the lattice is significantly improved. The Poisson’s ratio is adjusted using a geometric angle. The lattice is 3D printed using a shape memory polymer. Using its shape memory effect, the lattice demonstrates tunable shape reconfigurability as the ambient temperature changes. To capture its high stretchability, tunable Poisson’s ratio and shape reconfigurability, a phase evolution model for lattice structure is used. In the theoretical model, the effects of temperature on the material’s nonlinearity and geometric nonlinearity due to the lattice structure are assumed to be decoupled. The theoretical shape change agrees well with the Finite element results, while the theoretical model significantly reduces the computational cost. Numerical results show that the geometrical parameters and the ambient temperature can be manipulated to transform the lattice into target shapes with varying Poisson’s ratios. This work provides a design method for the 3D printed lattice structures and has potential applications in flexible electronics, soft robotics, and biomedicine.

scholarly journals 4D Printing of NiTi Auxetic Structure with Improved Ballistic Performance

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 745
Author(s):  
Hany Hassanin ◽  
Alessandro Abena ◽  
Mahmoud Ahmed Elsayed ◽  
Khamis Essa
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Analytical Model ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
4D Printing ◽  
Auxetic Structures ◽  
Negative Poisson's Ratio ◽  
The Impact ◽  
Auxetic Structure

Auxetic structures have attracted attention in energy absorption applications owing to their improved shear modulus and enhanced resistance to indentation. On the other hand, four-dimensional (4D) printing is an emerging technology that is capable of 3D printing smart materials with additional functionality. This paper introduces the development of a NiTi negative-Poisson’s-ratio structure with superelasticity/shape memory capabilities for improved ballistic applications. An analytical model was initially used to optimize the geometrical parameters of a re-entrant auxetic structure. It was found that the re-entrant auxetic structure with a cell angle of −30° produced the highest Poisson’s ratio of −2.089. The 4D printing process using a powder bed fusion system was used to fabricate the optimized NiTi auxetic structure. The measured negative Poisson’s ratio of the fabricated auxetic structure was found in agreement with both the analytical model and the finite element simulation. A finite element model was developed to simulate the dynamic response of the optimized auxetic NiTi structure subjected to different projectile speeds. Three stages of the impact process describing the penetration of the top plate, auxetic structure, and bottom plate have been identified. The results show that the optimized auxetic structures affect the dynamic response of the projectile by getting denser toward the impact location. This helped to improve the energy absorbed per unit mass of the NiTi auxetic structure to about two times higher than that of the solid NiTi plate and five times higher than that of the solid conventional steel plate.

scholarly journals One-click preparation of 3D print files (*.stl, *.wrl) from *.cif (crystallographic information framework) data using Cif2VRML

2014 ◽  
Vol 29 (S2) ◽  
pp. S42-S47 ◽  
Author(s):  
Werner Kaminsky ◽  
Trevor Snyder ◽  
Jennifer Stone-Sundberg ◽  
Peter Moeck
Keyword(s):  
3D Printing ◽  
Three Dimensional ◽  
New Materials ◽  
3D Print ◽  
3D Printed ◽  
Information Framework

Ongoing software developments for creating three-dimensional (3D) printed crystallographic models seamlessly from Crystallographic Information Framework (CIF) data (*.cif files) are reported. Color versus monochrome printing is briefly discussed. Recommendations are made on the basis of our preliminary printing efforts. A brief outlook on new materials for 3D printing is given.

scholarly journals Tensile and bending properties of flexible auxetic re-entrant honeycomb structures made by 3D printing

2020 ◽  
Vol 71 (02) ◽  
pp. 174-179
Author(s):  
DU ZHAOQUN ◽  
XU QIAOLI ◽  
ZHENG DONGMING ◽  
WANG QICAI
Keyword(s):  
3D Printing ◽  
Poisson’S Ratio ◽  
Shape Change ◽  
Thermoplastic Polyurethane ◽  
Special Property ◽  
Functional Materials ◽  
Poisson's Ratio ◽  
Printing Technology ◽  
Honeycomb Structures ◽  
3D Printing Technology

The main content dealt with in the paper was to present a flexible auxetic re-entrant honeycomb fabric, which was made of a formulated thermoplastic polyurethane material PolyFlex with super elastic properties by 3D printing technology. The auxetic fabric shows perpendicular expansion under tension and is flexible. So, its special property makes auxetic fabric have great potential in future functional materials. Wherein, the honeycomb cell angle is a key factor affecting Poisson’s ratio of fabric. In this paper, flexible re-entrant honeycomb structures with different cell angle are manufac- tured using 3D printing technology. The shape change under tension of two directions were investigated. The re-entrant honeycomb structures presented negative Poisson’s ratio immediately when stretched. The shape change consisted of three stages in X 1 -direction, the same as that in X 2 -direction. A noticeable discovery was that the shape change in X 1 -direction posed an out-plane change after the first shape change stage, while the shape change in X 2 -direction always remained in-plane in the whole tension process. The tensile modulus tested was consistent with the tendency of theoretical analysis of previous work. The bending rigidities were tested and similar to fabrics of poplin and denim. The results indicate that the auxetic fabric is suitable for special clothing.

A 3D-printed stretchable structural supercapacitor with active stretchability/flexibility and remarkable volumetric capacitance

2020 ◽  
Vol 8 (27) ◽  
pp. 13646-13658 ◽  
Author(s):  
Peng Chang ◽  
Hui Mei ◽  
Yuanfu Tan ◽  
Yu Zhao ◽  
Weizhao Huang ◽  
...  
Keyword(s):  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Negative Poisson’S Ratio ◽  
Negative Poisson's Ratio ◽  
3D Printed ◽  
Volumetric Capacitance

3D-printed stretchable negative Poisson's ratio structural CoNi2S4/NiCo-LDHs-based supercapacitor with active stretchability/flexibility and remarkable volumetric capacitance are built.

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