Negative Poisson's Ratio Materials Research Articles

Study on re-entrant hierarchical honeycombs in-plane impact

The introduction of hierarchical structure in cell materials can further improve their energy absorption effect, and negative Poisson's ratio materials have excellent energy absorption capacity and special deformation mode. In this paper, augmented double arrow honeycomb structures is introduced into the re-entrant honeycomb with negative Poisson's ratio as a substructure (RHA) to improve the mechanical properties of the first-order re-entrant honeycomb and enhance the energy absorption effect of the structure. The analytical formula of the collapse stress of honeycomb under quasi-static compression was derived by the two-scale method. The failure stress of RHA under different relative densities and impact velocities is discussed, and the analytical formula of RHA stress in dynamic crushing is derived by combining momentum conservation. Due to the special substructure, the secondary honeycomb discussed in this paper has two plateau periods. In this paper, the second plateau stress of the honeycomb structure is calculated innovatively. The numerical simulation results show that the collapse stress of RHA in the first plateau period is similar to that of the first-order re-entrant honeycomb, and the collapse stress in the second plateau period is increased by 332%. The research in this paper shows that the honeycomb with the second plateau period has a better energy absorption effect, which is an effective strategy for improving the energy absorption effect of the honeycomb. It can be further explored to improve the impact resistance of the honeycomb.

Study on the Static and Dynamic Performance of Concave Triangular Honeycomb Sandwich Panels

Negative Poisson's ratio (NPR) material perform well in shear resistance, impact resistance, and fracture resistance. In this study, a novel honeycomb sandwich panel is introduced, named Concave Triangular Honeycomb Sandwich Panel (CTHSP), which employs a concave triangle structure with NPR effect as the core layer. The study on the static and dynamic performance of CTHSPs are conducted through numerical simulation. Specifically, the influence of main geometric parameters (single cell size a, core layer thickness t, face-plate core layer thickness ratio h/H, concave angle α) on the bending stiffness, buckling critical load and natural frequency of CTHSPs are studied. Moreover, a new index of specific stiffness is introduced to evaluate the advantages of lightweight and high strength of the sandwich panels. The above research can provide a basis for the selection of CTHSPs in practical application.

Dynamic mechanical properties, interface structure evolution and deformation behaviors of PVA-carbon fiber reinforced concrete with negative Poisson’s ratio design

Based on the advantages of negative Poisson's ratio (NPR) materials in controlling deformation and absorbing energy, this paper combines NPR design with the preparation of fiber reinforced concrete (FRC) to optimize the anti-dynamic load performance of FRC. In this paper, a helical auxetic yarn (Hay) with NPR effect is obtained by wrapping carbon fiber (CF) on polyvinyl alcohol fiber (PVAF) at a certain angle, and it is mixed into concrete in different forms to obtain auxetic fiber concrete. In order to explore the influence of auxetic fiber on the anti-dynamic load performance of concrete, split Hopkinson pressure bar (SHPB) test and dropping ball impact test are carried out on different FRC. The impact resistance of FRC under different impact velocities is tested, and the impact resistance behavior of FRC is analyzed by digital speckle correlation method (DSCM). The results show that in SHPB test, the anti-impact strength of the layered auxetic fiber concrete is 19.1 % higher than that of the plain concrete (PC), and its fracture energy is increased by 25.8 %. In the dropping ball impact test, its fracture energy is 5 ∼ 9 times that of PC. In addition, the results of scanning electron microscopy (SEM) and DSCM test show that the incorporation of auxetic fiber has a positive effect on improving the generation and development of internal cracks in concrete, which is expected to provide a reference for the application of NPR materials in explosion resistance, penetration resistance and impact resistance of building structures.

A strategy for improving negative-Poisson's-ratio constraint effect and shape accuracy of metamaterials by regulating mechanical properties of elastomer with facile filler incorporation

Negative Poisson's ratio (NPR) metamaterials are widely used for their light weight and good shear resistance. However, the essential concave hollow structures in NPR materials may easily distort irregularly when the constraint effect of their solid materials is weak, especially for elastomer-based materials. Here, we introduced nano-scale carbon black (CB) particles into the NPR material based on thermoplastic polyurethane (TPU) elastomers to control the static and dynamic mechanical deformation behavior of the material, improving their constraint effect on the NPR structure. The results show that the modulus of the NPR structure is improved by 269% by adjusting the unit and rigid particle load. The Poisson's ratio of the NPR structure reaches as great as −1.3 via controlling the thickness/width ratio (TWR) of the unit. Meanwhile, finite element analysis verifies that when TWR is less than 0.5, increasing the modulus and yield strength of the composites can enhance the constraint on the NPR unit. Theoretical calculation shows that CB introduced into TPU can improve the shape accuracy of NPR structure. Therefore, the work could offer a new mechanical enhancing strategy for NPR materials, and its application potential is verified as a form of exoskeletons.

Design, microstructure, and mechanical property of negative Poisson's ratio porous structure fabricated by LPBF of AlCoCrFeNi2.1 eutectic high-entropy-alloy

Negative Poisson's ratio (NPR) materials are a type of structural materials that show an atypical deformation response. In general, metal-based porous materials with NPR do not have good mechanical properties due to the substrate's limited yield strength and plasticity, as the NPR behavior is unlikely to play a continuous role in the deformation. AlCoCrFeNi2.1, a eutectic high-entropy alloy (EHEA) with high yield strength and high ductility was used to fabricate the NPR structures by laser powder bed fusion (LPBF) to enhance the structures mechanical properties and NPR behavior. Structures with four different sets of structural parameters were designed for this study. The microstructure and mechanical properties of AlCoCrFeNi2.1 EHEA, synthesized by LPBF were studied, and the strength and energy absorption effect of NPR porous structure materials were investigated by static and dynamic compression experiments. Research showed the large number of inter-phase interfaces provided by the nano-scale cellular eutectic microstructure effectively restrict dislocation movement, thereby enhancing the strength and toughness of this EHEA alloy, endowing it with superior impact resistance, fracture resistance, and mechanical energy absorption. The compressive performance and the mechanical energy absorption capacity of the 3D EHEA-based NPR porous structure strongly depend on the inclination angle Ф between the thick rod and the horizontal direction in the 2D single-body model design. The strength and energy absorption of the structure with a high inclination angle of 75° material are both higher than those of the structure with a low inclination angle of 45° by almost a factor of two.

Analysis and optimization of impact energy absorption performance of mine refuge chamber filled with concave triangular negative poisson's ratio material

Analysis and optimization of impact energy absorption performance of mine refuge chamber filled with concave triangular negative poisson's ratio material

Research and defence application progress of negative poisson's ratio materials

In contrast to traditional materials, materials and structures with negative Poisson's ratio (NPR) transverse shrinkage (expansion) occurs under uniaxial pressure (tension). This characteristic makes NPR materials have many excellent advantages. Shear capacity and indentation resistance of NPR materials are introduced in this paper. According to these two characteristics, the paper also introduces the defence application of NPR materials.

Negative Poisson's ratio effect of P2/m phosphine

Negative Poisson's ratio materials have the advantages of good shear resistance, dent resistance, and fracture resistance. Thus, they have great application potential in the manufacturing field with high requirements for material mechanical flexibility. However, negative Poisson's ratio materials are relatively rare. In this paper, the first principles calculation is used to study the single-layer P2/m-P phosphorene. It is found that when −5% to 5% strain is applied along the zigzag (Y) direction, there is a negative Poisson's ratio effect along the Z direction, and Poisson's ratio is −0.288, which is about ten times that of the single-layer black phosphorus (the negative Poisson's ratio of the single-layer black phosphorus is −0.027). Compared with black phosphorene, it has more potential applications in wearable and impact resistant equipment.

Fully auxetic and multifunctional of two-dimensional δ -GeS and δ -GeSe

Auxetic materials, with negative Poisson's ratio (NPR), exhibit enhanced fracture toughness and shear resistance, due to their unusual mechanical behavior. Although a considerable number of two-dimensional (2D) NPR materials have been predicted theoretically, most of these materials have only in-plane or out-of-plane NPR. In this paper, using first-principles calculations, we found that monolayer $\ensuremath{\delta}$-GeS and $\ensuremath{\delta}$-GeSe show fully auxetic behaviors with both in-plane and out-of-plane NPRs at the same time. Meanwhile, monolayer $\ensuremath{\delta}$-GeSe has a direct bandgap and strong absorption in the blue and violet ranges. Owing to the large spontaneous polarization and strong dipole interaction, they can maintain the ferrielectric properties even at room temperature. Further, they have a considerable piezoelectric coefficient about one order of magnitude larger than recently studied 2D $\mathrm{MoS}_{2}$ and $h$-BN, due to small elastic stiffness constants. The rare fully auxeticity combined with various properties of monolayer $\ensuremath{\delta}$-GeS and $\ensuremath{\delta}$-GeSe could lead to novel multifunctional applications.

Excavation compensation method and key technology for surrounding rock control

The change in the stress state of the underground rock caused by excavation is the root cause of the deformation instability. Compensating for the stress change is one of the keys to effectively control the instantaneous deformation of rockbursts and the slow deformation of soft rocks in deep underground engineering. At present, the Platts pressure arch theory and the New Austrian Tunneling Method are commonly used in ground control, but their applicability to high-stress deep rock masses is limited. The strength and elongation of the traditional support materials are insufficient, the prestress is low, and it is difficult to effectively control the large deformation of deep rock masses. In this work, the excavation effect and support compensation effect of the rock are analyzed from the mechanics perspective, and an excavation compensation method suitable for controlling large deformation of deep rocks is proposed. The excavation effect verification experiments are carried out to examine the large deformation failure characteristics. Based on the excavation compensation method, a high prestress excavation compensation control technology is developed by using a new Negative Poisson's ratio (NPR) material. This technology is successfully applied to deep buried hard rocks and soft rocks to realize the effective control of the large deformation, which proves the applicability of the excavation compensation method and technology.

Investigation on micro-mechanism of strain-induced and defect-regulated negative Poisson's ratio of graphene

The Poisson's ratio of the in-plane pristine armchair and zigzag graphene under uniaxial tensile loading is studied by molecular dynamics simulations, which indicates that Poisson's ratio strongly depends on the tensile strain. At the critical strain, the Poisson's ratio will transform from positive to negative, and the critical strain of the zigzag is far less than that of armchair. The study on the representative cell of graphene shows that the intrinsic nature of strain-induced negative Poisson's ratio (NPR) is the competition between the variation rates of bond length and bond angle. Meanwhile, the critical strain that induces NPR has significant size effects, which depends on the proportion of representative cells at the width boundary in the whole graphene. What's more, 5-8-5 defect has a significant effect on the NPR phenomenon of graphene. By introducing 5-8-5 defects into in-plane graphene, the critical strain value that induces NPR can be effectively regulated by adjusting the distribution modes and percentage of defects. The distributions of 5-8-5 defects adjacent to each other in the X-direction and Y-direction can significantly reduce the critical strain value. Furthermore, by increasing the percentage of 5-8-5 defects in graphene, the critical strain value can be reduced to about 50%, and the 5-ring defect plays a vital role in reducing the critical strain value. Based on this, a penta-graphene consisting entirely of 5-rings is constructed, and its Poisson's ratio is studied. The results confirm that the critical strain that induces NPR is 0. In a word, the NPR of in-plane pristine graphene can be induced by tensile strain, 5-8-5 defects can regulate the critical strain value of NPR, and penta-graphene is a perfect NPR material.

Longitudinal and shear waves propagation in a periodic foundation with negative Poisson's ratio

The introduction of negative Poisson's ratio materials in engineering has opened new possibilities in materials science, acoustics, and civil engineering. Isotropic elastic foam with a negative Poisson's ratio of -0.7 has been produced which expands laterally when stretched, in contrast to ordinary materials. In this work, a new arrangement of seismic isolation foundation containing a unit cell of concrete - anti rubber and concrete/steel layers is proposed. The novelty lies in application of anti-rubber material as one of the three different layers periodically placed to form a periodic foundation. The auxetic material inclusion in this new arrangement broaden the no pass band of the periodic foundation compared to the earlier investigations. To demonstrate the effectiveness of this metamaterial foundation, an axially loaded column placed under three different foundations are numerically investigated. It is observed that the response of the metamaterial foundation with auxetic inclusion attenuated the elastics waves greatly compared to the foundations with rubber and traditional foundations. The results of the study could be used in developing new foundation materials for vibration attenuation for seismic waves which may cause destruction to engineering structures.

Factors affecting the negative Poisson's ratio of black phosphorus and black arsenic: electronic effects.

Negative Poisson's ratio (NPR) materials (when stretched longitudinally, the thickness of these materials increases along the lateral direction) are widely used in engineering because of their good resistance to shear, denting, and fracture. Observance of a negative Poisson's ratio (NPR) in two-dimensional (2D) single-layer materials presently has two explanations. The first, from mechanical principles, is that it derives from the presence of a special structure (hinge structure), such as in single-layer black phosphorus (BP) or black arsenic (β-As). The second, from electronic effects, is that it derives from (non-hinge-like) planar honeycomb structures and transition-metal dichalcogenides, MX2. Through first-principle calculations, we show that 2D single-layer materials with a hinge structure also have distinct electronic effects, similar to those observed from 2D planar honeycomb materials. Under strain, electronic effects of Px orbitals lead to the inherent NPR of the 2D single-layer material with a hinge structure. We discuss the influencing factors of the hinge structure on the NPR and demonstrate that the electronic effects inside the hinge structure are the fundamental factor in determining the inherent NPR.

Effect of negative poisson's ratio on the axially compressed postbuckling behavior of FG-GRMMC laminated cylindrical panels on elastic foundations

Auxetic materials are one of the metamaterials that have potential applications in many scientific and engineering fields. In this paper, an investigation is presented on the postbuckling responses of axially loaded graphenereinforced metal matrix composite (GRMMC) laminated cylindrical panels with in-plane negative Poisson's ratio (NPR). The panels are made of GRMMC laminates and rest on an elastic foundation in thermal environments. The graphene volume fraction in GRMMC layer may vary across the panel thickness in order to achieve a piece-wise functionally graded (FG) pattern. The GRMMC layers have in-plane NPR and temperature dependent material properties. The governing differential equations for the GRMMC laminated cylindrical panels are formulated based on the Reddy's third order shear deformation shell theory and are solved by using a singular perturbation technique along with a two-step perturbation approach. Numerical investigation is carried out to study the influence of the in-plane NPR, the FG patterns, the thermal environmental conditions and the foundation stiffness on the postbuckling responses of the GRMMC laminated cylindrical panels under axial compressive load. The results reveal that the in-plane NPR can lead to a substantial change of the postbuckling behaviors of the GRMMC laminated cylindrical panels.

Switchable acoustic metamaterial design through instability-driven microstructure transformations in soft composites

Soft materials can sustain large deformations, and, thus, can be used as a platform for tunable and switchable systems capable of wave manipulations. The fascinating elastic instability phenomenon in soft materials can be used to design new (meta-) materials with switchable microstructures, properties, and functions. Examples include the emergence of tunable band gaps at low-frequency ranges, the appearance of negative group velocity, and extreme wave slowing-down. Here, we investigate the elastic instability phenomenon in soft heterogeneous materials, and the applications of the phenomenon to design of soft acoustic metamaterials. The deformable composites typically combine soft matrix and stiffer phases (such as fibers or inclusions). We will start by considering the effect of experimentally observed wrinkling on elastic waves band-gaps in soft laminates. Next, we will discuss the emergence of the negative group velocity in 3-D fiber composite brought to the “marginally stable” state. Then, we will turn to the so-called auxetic or negative Poisson's ratio materials comprising of soft- matrix-void-stiff-inclusion systems, and illustrate the mechanisms leading to the emergence of low-frequency band gaps. Finally, a new type of instabilities giving rise to anti-symmetric domain formations will be illustrated on the examples of 3-D printed soft composites.

Enhanced output performance of flexible piezoelectric energy harvester by using auxetic graphene films as electrodes

We demonstrate an effective approach to enhance the output performance of a flexible piezoelectric energy harvester by using flexible electrodes with negative Poisson's ratio (NPR). The relationship between open-circuit voltage and Poisson's ratio of electrodes is established theoretically by deriving the analytical expression. It reveals a continuous increasing trend in open-circuit voltage with the decrease in Poisson's ratio of the electrodes. Further, graphene-assembled macro-film (GAMF), an NPR material with excellent flexibility and high conductivity, is used as the electrodes to fabricate flexible piezoelectric energy harvesters. Compared with the energy harvesters using silver electrode, the harvesters made by GAMF electrodes, with an NPR of −0.39, achieve nearly 1.7-times enhancement in open-circuit voltage and 1.6-times in short-circuit current for output performance. The experimental results are highly consistent with the simulation results, indicating that the GAMF has great prospects in developing flexible piezoelectric energy harvesters with enhanced electrical output performance.

A novel design method for 3D positive and negative Poisson's ratio material based on tension-twist coupling effects

In recent years, as the development of additive manufacturing technology, 3D negative Poisson’s ratio (NPR) materials attract many researchers’ interest. In this paper, a novel 3D NPR material design method based on the tension-twist coupling effect has been proposed. A novel category of 3D NPR and positive Poisson’s ratio (PPR) materials by linking multilayer 2D NPR materials through 3D chiral chains are proposed. The sign of the Poisson’s ratio depends on the linkage pattern of the 3D chiral chain. Based on this method, 11 types of novel 3D NPR and PPR materials are presented. Experimental and numerical methods are adopted to study the mechanical properties of the proposed novel 3D NPR and PPR materials. Results show that the novel 3D materials present desirable NPR and PPR as we expected, which proved the effectiveness of the proposed design method.

Elastic constants and phonon dispersion relation analysis of graphene sheet with varied Poisson's ratio

Through the achievement of elastic parameter equivalence by the structural mechanics method, the beam–truss space frame model for graphene sheet has been simplified; moreover a representative unit cell of the periodic graphene structure has been extracted. On this basis, the Bloch theorem is combined with the finite element method to determine the phonon dispersion relation of graphene. For the widely used thickness values of the carbon–carbon (C–C) bond, the aspect ratios (thickness/length) are so large that the shear deformation should be considered such that as a result, the negative Poisson's ratio (NPR) characteristic of the C–C bond is observed. Analytical expressions for the elastic constants of graphene sheet have been obtained with varied C–C bond Poisson's ratios. The reasonable coherence with previous results reveals the effectiveness of the structural mechanics method for analysing the mechanical properties of nanostructures. The effect of deformation modes on the phonon dispersion relation of graphene sheet is further discussed; it is concluded that the acoustic phonon modes are sensitive to the deformation modes of the C–C bond, whereas these deformation modes negligibly influence the optical phonon modes. The numerical results also reveal that the shear deformation and the resulting NPR effect play an important role in the mechanical property analysis of graphene sheet. To summarise, the interrelation between NPR materials and nano materials has stimulated a wide field of research; moreover, numerous novel phenomena have been observed.

Auxetics and Other Systems of Anomalous Characteristics

Auxetics and Other Systems of Anomalous Characteristics

An Accurate Design Equation for the Maximum Deflection in a Class of Auxetic Sectorial Plates

Auxetic materials are solids that exhibit negative Poisson's ratio. The effect of material auxeticity (i.e., negativity of Poisson's ratio) is investigated herein on the maximum deflection of sectorial plates with Simply‐Supported straight edges and Free curve edge (SSF). To aid the designer, an accurate and conveniently executable semi‐empirical model has been developed herein, which is valid for the entire range of Poisson's ratio of isotropic solids and for the plate's sectorial angle from 30 to 90 degrees. Results from exact solution reveal that the maximum deflection reduces sharply with the reduction of Poisson's ratio from positive to mildly negative, but deflection reduction is marginal when the sectorial plate's Poisson's ratio changes from moderately negative to highly negative value. It is therefore suggested that (a) the use of auxetic materials is useful to limit the extent of SSF sectorial plate deflection, and that (b) the use of the developed semi‐empirical model herein as a design equation gives greatly simplified but highly accurate maximum deflection prediction for SSF plates made from both conventional (positive Poisson's ratio) and auxetic (negative Poisson's ratio) materials.