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 Study on a Chiral Structure with Tunable Poisson’s Ratio

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3338
Author(s):  
Yanming Fu ◽  
Tianbiao Yu ◽  
Xin Wang
Keyword(s):  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Thermoplastic Polyurethane ◽  
High Energy ◽  
Poisson's Ratio ◽  
Chiral Structure ◽  
Hollow Circle ◽  
3D Printed ◽  
High Energy Absorption ◽  
Circle Diameter

A chiral structure with a negative Poisson’s ratio containing a hollow circle with varying diameters was designed, and the finite element method was used to investigate the variation in the Poisson’s ratio when the hollow circle diameter was varied (d = 0, 1, 2, 3, and 4 mm). The simulation results showed that the Poisson’s ratio was sensitive to the hollow circle diameter, and the minimum Poisson’s ratio was −0.43. Three specimens with different hollow circle diameters (d′ = 0, 1, and 3 mm) were 3D-printed from thermoplastic polyurethane, and the Poisson’s ratio and equivalent elastic modulus were measured. In the elastic range, the Poisson’s ratio increased and the equivalent elastic modulus decreased as the hollow circle diameter increased. The simulation and experimental results showed good agreement. The proposed structure is expected to be applicable to protective sports gear owing to its high energy absorption and the fact that its properties can be modified as required by adjusting the geometric parameters of the unit cell.

scholarly journals Charaterizations of 3D printed re-entrant pattern/aramid knit composite prepared by various tilting angles

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Imjoo Jung ◽  
Hyelim Kim ◽  
Sunhee Lee
Keyword(s):  
Tensile Properties ◽  
Poisson’S Ratio ◽  
Fused Deposition Modeling ◽  
Bending Strength ◽  
Thermoplastic Polyurethane ◽  
Poisson's Ratio ◽  
Fused Deposition ◽  
Initial Modulus ◽  
3D Printed ◽  
Composite Fabrics

AbstractThis study intended to compare and analyze the Poisson's ratio and mechanical properties of aramid knit (ARNT), 3D printed auxetic re-entrant pattern (3DP-RE), and 2 types of composite fabrics manufactured with ARNT and 3DP-RE. Specimens were manufactured by 3D printing the re-entrant pattern with a CFDM (conveyor fused deposition modeling) 3D printer and TPU (thermoplastic polyurethane) filament, combining with aramid knit in 2 ways. Then, Poisson's ratio, bending, compression, and tensile properties were tested. As a result of Poisson's ratio, 3DP-RE and its 2 types of composite fabric showed negative Poisson's ratio at all angles and deformed stable at 0° and 90° than the bias direction. The bending strength confirmed that the composite fabric showed a lower value. But, the strain at max bending strength was greater than a substrate fabric. At the compression properties, it has been confirmed that compression strength and toughness are improved when manufacturing composite fabrics. As a result of tensile properties, 3DP-RE and composite fabrics were significantly more initial modulus, elongation and toughness than ARNT and were shown to be the largest in gradient 90°. Therefore, it is confirmed that the performance is excellent when fabricated as a 3DP-RE/ARNT composite fabric, and based on the results of studies, we intend to use it as the basic data for composite fabrics of auxetic structure suitable for shoe uppers.

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 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.

Metamaterials with enhanced mechanical properties and tuneable Poisson’s ratio

2021 ◽  
Author(s):  
Amer Alomarah ◽  
Syed Masood ◽  
Dong Ruan
Keyword(s):  
Poisson’S Ratio ◽  
Structural Modification ◽  
Mechanical Response ◽  
Good Alternative ◽  
Poisson's Ratio ◽  
Polyamide 12 ◽  
Loading Direction ◽  
Wide Range ◽  
Potential Applications ◽  
Parametric Studies

Abstract This paper reports a structural modification of an auxetic metamaterial with a combination of representative re-entrant and chiral topologies, namely, a re-entrant chiral auxetic (RCA). The main driving force for the structural modification was to overcome the undesirable properties of the RCA metamaterial such as anisotropic mechanical response under uniaxial compression. Additively manufactured polyamide 12 specimens via Multi Jet Fusion (MJF) were quasi-statically compressed along the two in-plane directions. The experimental results confirmed that the modified structure was less sensitive to the loading direction and the deformation was more uniform. Moreover, similar energy absorptions were obtained when the modified metamaterial was crushed along the two in-plane directions. The energy absorptions were improved from 390 to 950 kJ/m³ and from 500 to 1000 kJ/m³ compared with the RCA when they were crushed along the X and Y directions, respectively. The absorbed energy per unit mass (SEA) also improved from 1.4 to 2.9 J/g and from 1.78 to 3.1 J/g compared with that of the RCA under the axial compression along the X and Y directions. Furthermore, parametric studies were performed and the effects of geometric parameters of the modified metamaterial were numerically investigated. Tuneable auxetic feature was obtained. The energy absorption and Poisson’s ratio of the modified metamaterial offer it a good alternative for a wide range of potential applications in the areas such as aerospace, automotive, and human protective equipment.

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.

Retracted Article: 3D printed highly flexible strain sensor based on TPU–graphene composite for feedback from high speed robotic applications

2019 ◽  
Vol 7 (16) ◽  
pp. 4692-4701 ◽  
Author(s):  
Jahan Zeb Gul ◽  
Memoon Sajid ◽  
Kyung Hyun Choi
Keyword(s):  
High Speed ◽  
Thermoplastic Polyurethane ◽  
Three Dimensional ◽  
Strain Sensor ◽  
Graphene Composite ◽  
Retracted Article ◽  
3D Printed ◽  
Resistive Type ◽  
Flexible Strain Sensor ◽  
Robotic Applications

A novel, highly flexible and electrically resistive-type strain sensor with a special three-dimensional conductive network was 3D printed using a composite of conductive graphene pellets and flexible thermoplastic polyurethane (TPU) pellets.

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.

Investigation Into the Biphasic Properties of a Hydrogel for Use in a Cushion Form Replacement Joint

1998 ◽  
Vol 120 (3) ◽  
pp. 362-369 ◽  
Author(s):  
A. A. J. Goldsmith ◽  
S. E. Clift
Keyword(s):  
Articular Cartilage ◽  
Material Properties ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Biphasic Model ◽  
Aggregate Modulus ◽  
Curve Fit ◽  
Potential Applications

A hydrogel with potential applications in the role of a cushion form replacement joint bearing surface material has been investigated. The material properties are required for further development and design studies and have not previously been quantified. Creep indentation experiments were therefore performed on samples of the hydrogel. The biphasic model developed by Mow and co-workers (Mak et al., 1987; Mow et al., 1989a) was used to curve-fit the experimental data to theoretical solutions in order to extract the three intrinsic biphasic material properties of the hydrogel (aggregate modulus, HA, Poisson’s ratio, νs, and permeability, k). Ranges of material properties were determined: aggregate modulus was calculated to be between 18.4 and 27.5 MPa, Poisson’s ratio 0.0–0.307, and permeability 0.012–7.27 × 10−17 m4/Ns. The hydrogel thus had a higher aggregate modulus than values published for natural normal articular cartilage, the Poisson’s ratios were similar to articular cartilage, and finally the hydrogel was found to be less permeable than articular cartilage. The determination of these values will facilitate further numerical analysis of the stress distribution in a cushion form replacement joint.

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