scholarly journals 3D Printing of Auxetic Shape-Memory Metamaterial Towards Designable Buckling

2021 ◽  
Vol 13 (01) ◽  
pp. 2150011
Author(s):  
Zhenghong Li ◽  
Yuheng Liu ◽  
Yafei Wang ◽  
Haibao Lu ◽  
Ming Lei ◽  
...  
Keyword(s):  
Shape Memory ◽  
Poisson’S Ratio ◽  
Influence Factors ◽  
Maxwell Model ◽  
Thermomechanical Properties ◽  
Poisson's Ratio ◽  
Rate Dependent ◽  
Generalized Maxwell Model ◽  
3D Printed ◽  
Thermomechanical Processes

As one of the most popular 3D printed metamaterials, the auxetic structure with its tunable Poisson’s ratio has attracted huge amount of attention recently. In this study, we designed an auxetic shape-memory metamaterial, which showed designable buckling responses by using the thermomechanically coupled in-plane instability. The influence of viscoelasticity on in-plane moduli and Poisson’s ratios of shape-memory auxetic metamaterial was experimentally investigated. Based on the generalized Maxwell model and finite-element method, the buckling behaviors and their main influence factors were studied. The analytical results and experimental ones showed a good agreement. Thermomechanical properties of the printed metamaterials govern the temperature and strain rate-dependent buckling, and a controllable transition from the negative to positive Poisson’s ratio in the metamaterials can be achieved. Based on the shape memory effect, the buckled state and the Poisson’s ratio of the metamaterials can be tuned by programmed thermomechanical processes. This study provides a simple and efficient way to generate morphing structures using the designable buckling effect.

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.

Effect of Fiber Orientation and Strain Rate on the Nonlinear Uniaxial Tensile Material Properties of Tendon

2003 ◽  
Vol 125 (5) ◽  
pp. 726-731 ◽  
Author(s):  
Heather Anne Lynch ◽  
Wade Johannessen ◽  
Jeffrey P. Wu ◽  
Andrew Jawa ◽  
Dawn M. Elliott
Keyword(s):  
Stress Relaxation ◽  
Strain Rate ◽  
Material Properties ◽  
Poisson’S Ratio ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Poisson's Ratio ◽  
Fiber Direction ◽  
Linear Region ◽  
Rate Dependent

Tendons are exposed to complex loading scenarios that can only be quantified by mathematical models, requiring a full knowledge of tendon mechanical properties. This study measured the anisotropic, nonlinear, elastic material properties of tendon. Previous studies have primarily used constant strain-rate tensile tests to determine elastic modulus in the fiber direction. Data for Poisson’s ratio aligned with the fiber direction and all material properties transverse to the fiber direction are sparse. Additionally, it is not known whether quasi-static constant strain-rate tests represent equilibrium elastic tissue behavior. Incremental stress-relaxation and constant strain-rate tensile tests were performed on sheep flexor tendon samples aligned with the tendon fiber direction or transverse to the fiber direction to determine the anisotropic properties of toe-region modulus E0, linear-region modulus (E), and Poisson’s ratio (ν). Among the modulus values calculated, only fiber-aligned linear-region modulus E1 was found to be strain-rate dependent. The E1 calculated from the constant strain-rate tests were significantly greater than the value calculated from incremental stress-relaxation testing. Fiber-aligned toe-region modulus E10=10.5±4.7 MPa and linear-region modulus E1=34.0±15.5 MPa were consistently 2 orders of magnitude greater than transverse moduli (E20=0.055±0.044 MPa,E2=0.157±0.154 MPa). Poisson’s ratio values were not found to be rate-dependent in either the fiber-aligned (ν12=2.98±2.59, n=24) or transverse (ν21=0.488±0.653, n=22) directions, and average Poisson’s ratio values in the fiber-aligned direction were six times greater than in the transverse direction. The lack of strain-rate dependence of transverse properties demonstrates that slow constant strain-rate tests represent elastic properties in the transverse direction. However, the strain-rate dependence demonstrated by the fiber-aligned linear-region modulus suggests that incremental stress-relaxation tests are necessary to determine the equilibrium elastic properties of tendon, and may be more appropriate for determining the properties to be used in elastic mathematical models.

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.

scholarly journals Blocked Shape Memory Effect in Negative Poisson’s Ratio Polymer Metamaterials

2016 ◽  
Vol 8 (31) ◽  
pp. 20319-20328 ◽  
Author(s):  
Katarzyna Boba ◽  
Matteo Bianchi ◽  
Greg McCombe ◽  
Ruben Gatt ◽  
Anselm C. Griffin ◽  
...  
Keyword(s):  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Negative Poisson’S Ratio ◽  
Negative Poisson's Ratio

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.

Sign in / Sign up

Export Citation Format

Share Document