Zero Poisson's Ratio Research Articles

Hydrogel-Based Network Metamaterials with Biological Tissue-like Poisson's Ratio Behavior and Stress Response.

Soft network metamaterials are widely used in fields such as flexible electronics, tissue engineering, and biomedicine due to their superior properties including low density, high stretchability, and high breathability. However, the prediction and customization of the nonlinear mechanical behavior of soft network metamaterials remain a challenging problem. In this study, a family of hydrogel-based network metamaterials with biological tissue-like mechanical properties are developed based on a machine learning-driven optimization design method. Numerical and experimental results explain the relationship between the mechanical properties of the designed metamaterials and their microstructural features and stretching ratios. The results indicate that the hydrogel-based network metamaterials exhibit J-shaped stress-deformation (σ-λ) behavior similar to biological tissues. This phenomenon arises from the transition of the deformation mode of metamaterials from bending-dominated to stretching-dominated as the stretching ratio increases. Based on the proposed design scheme, the Poisson's ratio of metamaterials can be adjusted within a remarkably wide range of -1.06 to 1.34. Furthermore, through optimizing the design parameters of the metamaterial, the customization of network metamaterials with biological tissue-like zero Poisson's ratio behavior and stress response is achieved. The potential applications of hydrogel-based network metamaterials are demonstrated through artificial skin and LED integrated device. This research offers novel insights into predicting, designing, and fabricating the mechanical behavior of soft network metamaterials.

Origami Morphing Surfaces with Arrayed Quasi-Rigid-Foldable Polyhedrons.

Artificial morphing surfaces, inspired by the high adaptability of biological tissues, have emerged as a significant area of research in recent years. However, the practical applications of these surfaces, constructed from soft materials, are considerably limited due to their low shear stiffness. Rigid-foldable cylinders are anisotropic structures that exhibit high adaptability and shear stiffness. Thus, they have the potential to address this issue. However, changes in shape and area at both ends during folding can lead to collisions or gaps on the morphing surface. Here, a quasi-rigid-foldable (QRF)rate is first introduced to quantify the rigid-foldability of a foldable structure and validate it through experiments. More importantly, a QRF polyhedron is then proposed, which is not only notably anisotropic, similar to a rigid-foldable cylinder, but also exhibits a zero-Poisson's ratio property, making it suitable for arraying as morphing surfaces without any collisions or gaps. Such surfaces have a myriad of applications, including modulating electromagnetic waves, gripping fragile objects, and serving as soles for climbing robots.

Discovering chiral auxetic structures with near-zero Poisson's ratio using an active learning strategy

In this paper, a set of hexachiral auxetic structural designs with near zero Poisson's ratio (ZPR) characteristics is discovered via the combination of machine learning and experimentally validated finite element simulation. An active learning-enhanced Gaussian process model is utilized to generate multiple designs with near-ZPR properties and discover the boundary of the positive and negative Poisson's ratio. The results show that active learning successfully constructs a probabilistic estimation of the ZPR boundary. A comprehensive analysis of the identified ZPR contour is performed to extract crucial design insights. The findings indicate that the near-ZPR characteristic can be attained through various combinations of geometric parameters. This offers users the flexibility to select the configuration that best aligns with their specific requirements. Additionally, an investigation of the various ZPR configurations that have been discovered is carried out to understand the mechanism that yields near-ZPR property. One discovered near-ZPR design was subsequently fabricated using 3D printing for validation purposes. The experimental outcomes demonstrated a good agreement with the numerical predictions, underscoring the effectiveness of the active learning strategy in uncovering designs that closely approach ZPR conditions.

A lightweight AuxHex zero Poisson's ratio pressure-resistant sandwich cylindrical shell and its load-bearing and sound insulation behaviors: Design, simulation and experiment

Pressure-resistant hulls are critical components in underwater vehicles and submersible systems. Exploring novel materials and structures has been a growing trend to overcome conventional structural limitations and achieve multifunctionality. Mechanical metamaterials with tunable physical properties can offer promise. Therefore, this study focuses on designing and fabricating a pressure-resistant sandwich cylindrical shell using AuxHex zero Poisson's ratio (ZPR) mechanical metamaterials. Structural optimization is employed to develop a lightweight AuxHex ZPR unit cell to withstand deep-sea pressure. Mechanical and acoustic experiments were then conducted on a 3D-printed Titanium alloy specimen, and the rationality of numerical modeling was validated by the experimental results. Load bearing and sound insulation properties of the designed ZPR sandwich cylindrical shell have been numerically analyzed and compared with its geometrically similar positive Poisson's ratio (PPR) and negative Poisson's ratio (NPR) shells. The designed ZPR structure that yields a mass density ratio of 0.569 g/cm³ can withstand hydrostatic pressure at 1000 m depths without strength or buckling damage, while adequate reserve buoyancy can be maintained. The submerged ZPR shell structure can provide superior protection for inner spaces and its average sound transmission loss (STL) is more than 5 dB higher than the PPR and NPR shells.

In-plane crushing behavior and energy absorption of sponge-inspired lattice structures

Novel energy-absorbing structures were a crucial requirement for the structural crashworthiness design in the automotive and aerospace industries. Inspired by the unique double-diagonal reinforced configuration of deep-sea glass sponge, we proposed a bionic lattice structure (BLS) fabricated by additive manufacturing (AM). In-plane quasi-static compression tests and numerical simulations were conducted on BLS with varying wall thicknesses (t), and two distinct deformation modes were observed: layer-by-layer mode with zero Poisson's ratio (ZPR) and uniform deformation mode with negative Poisson's ratio (NPR). The effects of structural parameters on the crushing behavior of BLS were investigated by numerical method. It was found that BLS with wall thickness (t) of 1.2 mm exhibited better energy absorption performance than 0.45 mm, with the energy absorption (EA), specific energy absorption (SEA), and mean crushing force (Pm) increased by 745.0%, 216.5%, and 744.3%, respectively. The change in crushing mode was caused by the ‘+’ shaped joints changing from buckling to rotation, and the crushing behaviors of BLS could be effectively controlled by adjusting unit size and unit number. Finally, theoretical prediction models were developed using simplified super folding element (SSFE) theory to gain deeper insights into crushing behavior and performance of BLS. The present study provided valuable insights into the in-plane crushing and energy absorption capabilities of BLS. Moreover, it highlighted the potential of the double-diagonal reinforcement design in developing innovative energy-absorbing structures.

Flexible sensors with zero Poisson's ratio.

Flexible sensors have been developed for the perception of various stimuli. However, complex deformation, usually resulting from forces or strains from multi-axes, can be challenging to measure due to the lack of independent perception of multiaxial stimuli. Herein, flexible sensors based on the metamaterial membrane with zero Poisson's ratio (ZPR) are proposed to achieve independent detection of biaxial stimuli. By deliberately designing the geometric dimensions and arrangement parameters of elements, the Poisson's ratio of an elastomer membrane can be modulated from negative to positive, and the ZPR membrane can maintain a constant transverse dimension under longitudinal stimuli. Due to the accurate monitoring of grasping force by ZPR sensors that are insensitive to curvatures of contact surfaces, rigid robotic manipulators can be guided to safely grasp deformable objects. Meanwhile, the ZPR sensor can also precisely distinguish different states of manipulators. When ZPR sensors are attached to a thermal-actuation soft robot, they can accurately detect the moving distance and direction. This work presents a new strategy for independent biaxial stimuli perception through the design of mechanical metamaterials, and may inspire the future development of advanced flexible sensors for healthcare, human-machine interfaces and robotic tactile sensing.

Topology optimization design of microstructures with zero Poisson's ratio

Mechanical metamaterials are materials that possess unconventional mechanical properties that are not found in homogeneous materials, achieved through specific artificial microstructures. Topology optimization is an effective design method for such materials. In this paper, a topology optimization-based method for designing zero Poisson's ratio mechanical metamaterials is proposed. Firstly, a zero Poisson's ratio topology optimization objective function is constructed based on the energy homogenization method, and the optimal microstructure topology configuration and elastic coefficient matrix under different initial topologies and volume fractions are obtained through the boundary density evolution topology optimization method. To improve the saw tooth effect of the boundaries, the node density level set method is used to smooth the boundaries of the microstructure. Then, in finite element simulation analysis, it is demonstrated that the proposed method can effectively design microstructures with zero Poisson's ratio properties. It is also shown that microstructures with expected stiffness and zero Poisson's ratio properties can be obtained by changing the volume fraction and selecting materials with different stiffnesses. Finally, the unit cell is periodically arranged to form a multi-lattice metamaterial, and its zero Poisson's ratio mechanical performance in both X and Y directions is verified.

Crashworthiness and dimensional stability analysis of zero Poisson's ratio Fish Cells lattice structures

The present article introduces Zero Poisson's Ratio (ZPR) Fish Cells metamaterial and investigates the effects of Poisson's ratio on the crashworthiness of Positive (PPR), Negative (NPR), and Zero Poisson's ratio lattice structures. High-fidelity Finite Element (FE) models of the proposed sandwich structures are built, based on identical domains for unit cells. Impact performances of lattice structures are addressed for low (2 m/s) and high (5 m/s) impact velocities in three orthogonal directions. The parameters investigated for crashworthiness include impactor's penetration depth, von Mises stress distribution, edges deformation and dimensional stability. Numerical results demonstrate that, unlike PPR and NPR models, the Fish Cells ZPR model possesses greater lateral stability and structural integrity with minimal edge deformations in all three directions. This leads to reduced lateral impact transfer to adjacent components and localised damaged zones, increasing the life span of structural components while reducing maintenance and repair downtime. Experimental analyses are conducted on the Fish Cells metamaterial through a drop tower test for demonstrating agreement with simulations and validation of the proposed modelling approach.

An isotropic zero Poisson's ratio metamaterial based on the aperiodic ‘hat’ monotile

Metamaterials are synthetic materials, engineered to have desirable mechanical properties. This paper is concerned with a class of cellular metamaterials that minimise the Poisson's ratio, a metric that characterises the deformation behaviour of materials according to their orthogonal response to applied force. This secondary deformation is usually visually apparent as a sideways “bulge”, and can limit the longevity of multi-material components, from aircraft parts to medical implants, because of the interference shear stresses that arise between different materials due to deformations in different directions by different amounts. As a result, low Poisson's ratio can be a desirable mechanical property and the challenge of producing cellular metamaterials that have reduced Poisson's ratio has received significant research attention. However, solutions that have been proposed tend to be limited in their applicability, either because they are anisotropic, so behaviour varies greatly according to direction of the applied force, or because they are very low in relative density, so have low stiffness. Here we introduce a new cellular metamaterial, a honeycomb based on the recently discovered aperiodic ‘hat’ monotile, which offers nominally zero Poisson's ratio. Results from compression testing and computational modelling show that the behaviour of this metamaterial is isotropic, and is consistent across a range of relative densities, leading to the exciting conclusion that zero Poisson's ratio is possible for different stiffnesses. We envisage that this metamaterial will facilitate otherwise unfeasible technologies, such as morphing wing structures and medical devices that better mimic the behaviour of tissues such as cartilage.

Cycle deformation behavior of 3D‐printed CF/PEEK honeycomb metamaterials with zero Poisson's ratios

AbstractTo realize the one‐dimensional deformation of morphing wings, zero Poisson's ratio (ZPR) honeycomb metamaterials have become a popular research topic due to their lightweight, low in‐plane modulus, and high out‐of‐plane strength. A ZPR honeycomb metamaterial is designed and prepared from short‐cut carbon fiber‐reinforced polyetheretherketone (CF/PEEK) by a 3D printer. The mechanical properties of ZPR honeycomb metamaterials were tested to determine their tensile and bending stiffness. The results show that the metamaterial can achieve 62.3% ± 3.3% in‐plane elastic deformation after optimized structure design. At the same time, metamaterial has a certain bending resistance to keep the airfoil from normal buckling deformation. Moreover, a new test method for evaluating the cycle deformation behavior of flexible morphing wings is proposed. The high‐speed cyclic tension‐compression test showed that H22‐t0.6‐CT has the best stability, which may be related to its lower porosity (2.15% ± 0.12%). These results indicate that ZPR honeycomb metamaterials have great application prospects in the field of morphing wings.Highlights The printed CF/PEEK wire is treated as a transversely isotropic material. ZPR honeycomb metamaterial allows for more than 50% in‐plane deformation. A new test method to evaluate the cyclic deformation behavior.

Load carrying capacity analysis and gradient design of new 3D zero Poisson's ratio structures

Mechanical metamaterials offer a wide range of potential applications in the load-bearing structures of deformed wings due to their characteristics like light weight and high stiffness. In this paper, four 3D zero Poisson’s ratio structures are proposed. The modified concave hexagon structure is verified by quasi-static compression experiment, which shows that the finite element analysis is correct. The load-bearing capacity of the four structures is compared using experiments and finite elements, the concave hexagonal structure with oblique bar embeddings (CHSO) has a higher load-bearing capacity. The effect of cell wall thickness on the energy absorption capacity is investigated, the larger the wall thickness, the higher the energy absorption capacity of the structure, but there is the disadvantage of excessive peak stress. Therefore, a gradient design is carried out for CHSO. The effects of the number of gradient layers, gradient rate and gradient distribution mode on the peak stress, plateau stress and specific energy absorption of the structure are also investigated. The optimal gradient design mode is finally obtained by comparison with the goal of increasing the plateau stress and specific energy absorption of the structure and reducing the peak stress. It provides a good design idea for the design of the load-bearing structures of deformed wings to meet lightweight requirements.

Zero-Poisson's-Ratio Honeycomb-Filled Braided Textile Reinforced Conical Tubes: Designing, Manufacturing and Testing

Zero-Poisson's-Ratio Honeycomb-Filled Braided Textile Reinforced Conical Tubes: Designing, Manufacturing and Testing

Underwater cylindrical sandwich meta-structures composed of graded semi re-entrant zero Poisson's ratio metamaterials with pre-strained wave propagation properties

Zero Poisson's ratio (ZPR) mechanical metamaterials can yield no transverse displacements when unidirectionally compressed, and cylindrical sandwich meta-structures composed of semi re-entrant (SRE) ZPR metamaterials are thus explored for applications on cylindrical shells of underwater equipment or submersible structures. A group of ZPR unit cells with specified pre-strained wave propagation characteristics and adequate load-bearing capabilities is optimally designed based on the periodic boundary condition (PBC) and Bloch's Theorem. The sound transmission and pressure-resistant performance of cylindrical sandwich meta-structures comprising the homogeneous and graded SRE ZPR unit cells are then investigated. The results show that the designed meta-structures can perfectly yield better vibroacoustic attenuation behavior within the specified frequency regions corresponding to the pre-strained band gaps and safely bear the hydrostatic pressure equivalent to 1000 m depth with low weight-bulk ratios. In addition, the functionally graded metamaterial core can boost vibroacoustic performance within broader frequency ranges.

A novel star-shaped honeycomb with enhanced energy absorption

To obtain a structure with excellent energy-absorbing ability, based on the traditional star-shaped honeycomb (SSH), a crossed star-shaped honeycomb (CSSH) was designed via evolving the horizontal and vertical walls of the honeycomb into crossed inclined walls. In this paper, the Poisson's ratio and Young's modulus of honeycomb under axial load are theoretically deduced, and a method is proposed to evaluate the deformation stability of honeycomb with the maximum deviation of unilateral horizontal strain (MDUHS). Numerical simulation is employed to verify the theoretical solution, and the in-plane mechanical properties and deformation behavior of CSSH are investigated in detail. The numerical simulation method in Abaqus software was verified by using quasi-static crush test data of 3D printed CSSH specimens. It is found that by changing the inclined angle θ2, CSSH can evolve into a positive Poisson's ratio(PPR), zero Poisson's ratio(ZPR), or negative Poisson's ratio structure(NPR), and Young's modulus is very sensitive to the difference between the opened angle θ1 and the inclined angle θ2; increasing θ1 or decreasing θ2 not only significantly improves the energy absorption capacity of the honeycomb but also facilitates the generation of a more pronounced double plateau region on the stress-strain curve; by changing the length of the crossed inclined wall, three improved CSSHs(ICSSH) can be obtained. Among them, by adjusting the length of the crossed inclined wall in the horizontal direction, the structure with the superior energy absorption capacity can be obtained. The structure with excellent deformation stability can be obtained through adjusting the length of the crossed inclined wall in the vertical direction. Results show that the performance of CSSH is better than that of SSH, with a specific energy absorption (SEA) of 245% higher than that of SSH. This work is expected to guide the design of new auxetic honeycombs with better energy absorption properties, and can also provide a reference for the optimization of honeycombs.

Improved lightweight corrugated network design to auxetic perforated metamaterial

Auxetic metamaterials with peanut-shaped perforations are superior for durable morphing control applications due to its extremely low stress concentration level and controllable auxetic capability. However, there are some issues to be concerned for such metamaterials with complex cellular features, including (1) improving structure topology for higher material efficiency, (2) tunable Poisson's ratio from positive to negative, (3) characterization of full elastic properties. To this end, an improved lightweight design with orthogonal corrugated beams is proposed in this study to approximate the perforated auxetic structure and then its full anisotropic elastic constants are characterized by a distinctive computational homogenization model based on the eigenfunction expansion variational theory with simple implementation technique of periodic displacement constraints. The numerical model is verified by the experimental tests of three specimens with different geometrical topologies. Subsequently, the dependence of structural elastic responses on the microstructural configuration is highlighted towards an elevated understanding of cell-structure-property relationship. It is demonstrated that the local in-plane rotation of interconnected regions in unit cell under uniaxial loading contributes to the structural auxetic behavior. Also, it is feasible to achieve tailorable mechanical properties through flexible microstructural adjustment and a design criterion of the crucial zero Poisson's ratio is given by a polynomial in terms of the normalized amplitude and thickness of the curved beam. The results pave a way to the design and analysis of novel metamaterials with tunable mechanical properties.

Covalent three-dimensional carbon nanotube and derived B-C-N polymorphs with superhardness and zero Poisson's ratio.

Carbon is one of the most versatile atoms and fosters a wealth of carbon allotropes with superior mechanical and electronic properties. A three-dimensional covalent carbon nanotube, named CCN, with a hexagonal honeycomb-like crystalline structure is proposed theoretically. CCN consists of sp 3 bonded coaxially teamed (6,0) carbon nanotubes, and the tube walls possess intrinsic wrinkles, which trigger miraculous physical properties. The mechanical and thermal dynamic stabilities are confirmed, and molecular dynamics simulations indicate high temperature thermal stability up to 1500 K. CCN has an unusual cork-like zero Poisson's ratio along the axial direction of the nanotubes, and the axial/radial stretching or compression rarely effects the radial/axial dimensions of the nanotubes. CCN is superhard with Vickers hardness of 82.8 GPa, matching that of cubic boron nitride. Substitution B and N atoms for C atoms result in superhard CCN-B12N8 and CCN-C8N12 with quasi-zero Poisson's radio along both axial and radial directions.

Design of quadrilateral zero-Poisson's ratio metamaterial and its application in ship explosion-proof hatch door

Most structures with Zero Poisson's Ratio(ZPR) are two-dimensional structures, and three-dimensional zero Poisson's ratio structures are few. In this paper, a new three-dimensional zero Poisson's ratio structure was designed and applied to ship explosion-proof cabin doors. The proposed quadrilateral zero-Poisson's ratio structure exhibits zero-Poisson's ratio effect in both directions. The influence of geometric dimensions on the mechanical properties of the structure was analyzed by finite element software. The results show that with the decrease of B-bar length, the structural volume decreases, but the stiffness and strength increase. The maximum total deformation of the structure decreases from 3.58 mm to 0.14 mm. At the same time, the frame position of the structure also affects the mechanical properties of the structure. The results show that under the same external load, the stiffness and strength of the upper quadrilateral structure increase when the volume decreases, and the maximum value of total deformation differs by 44%. The designed quadrilateral zero Poisson's ratio structure was applied to the explosion-proof door, and compared with the foam aluminum door with the same quality. The results show that the strain energy of the core layer with zero Poisson's ratio was 5.6 times that of the aluminum foam core layer. Considering the clogging and sealing of the door body, zero Poisson's ratio structure is more suitable for the application of explosion-proof hatch doors on ships.

Manufacturing and testing of CFRC sandwich cylinder with zero-Poisson's-ratio Kevlar meta-honeycomb core layer

A carbon fiber reinforced composite (CFRC) sandwich cylinder with over-expanded honeycomb core (OHC) layer was designed and manufactured to get a lightweight sandwich cylinder meanwhile remaining a relatively simpler fabrication process, as the meta-honeycomb with zero-Poisson's-ratio can be freely curled into a cylindrical structure without saddle warping. Uniaxial compression and free vibration experiments were performed to reveal the strength and stiffness of the cylinder. Due to the rapid stiffness change at the ends, the damage occurs near the end with a horizontal crack. Skin fracture controls the final failure of the cylinder, and the load carrying capability (LCC) is a bit stronger than the referenced cylinder. Material validation analysis, theoretical formulas and imperfection FEM simulation methods were carried out to characterize the failure process. Although the LCC is affected by the local failure at the end, this cylinder shows a much easier manufacturing process and excellent stiffness.

4D Metamaterials with Zero Poisson's Ratio, Shape Recovery, and Energy Absorption Features

4D Metamaterials with Zero Poisson's Ratio, Shape Recovery, and Energy Absorption Features

A novel constitutive stress-strain law for compressive deformation of the gas diffusion layer

Substantial compressive deformation occurs in the gas diffusion layer (GDL) under the pressure applied during the fuel cell assembly. The GDL deformation has a direct impact on the efficiency and performance of the fuel cell since it leads to the alteration of the GDL microstructure and porosity. This makes the accurate characterization of the GDL compressive behavior crucial for analyzing the fuel cell performance and its optimal design. In this paper, analytical, experimental, and numerical methods have been employed to comprehensively study the constitutive law of the GDL under compression. Starting from the recently developed stress-density relations, the constitutive stress-strain equations are derived for the GDL and the relation between the stress-density and stress-strain laws are revealed. Experimental compression tests have been performed on GDL samples and the capability of the proposed constitutive law in capturing the real behavior of the material has been proved. It has been observed that the simplifying assumption of constant zero Poisson's ratio in the through-plane direction made in many previous studies cannot accurately represent the GDL material behavior and a modification is proposed. The developed constitutive law has been successfully implemented in a finite element model of the GDL-bipolar plate assembly in the fuel cell structure and the variations of the GDL porosity, density, and through-plane Young's modulus and Poisson's ratio have been investigated for different vertical displacements of the bipolar plate.