Negative Poisson's Ratio Effect Research Articles

Reliable comparison of multi-directional mechanical properties for biomimetic circle arc honeycombs

Abstract Compared to straight honeycombs, curved honeycombs derived from biomimetic strategies typically exhibit superior mechanical properties and a broader tunable range. Consequently, there has been a surge in research focusing on curved honeycombs. However, few studies have concurrently designed multiple honeycombs for reliable comparisons, and little attention has been given to isotropy. In this study, circle arc walls were introduced to replace the straight walls of five classical honeycombs, thereby creating representative curved honeycombs for analysis. The numerical modeling method in ANSYS software was validated by experimentally testing 3D printed specimens of circle arc honeycombs. At the same mass and under loading conditions in different directions, it was found that the Young's modulus, yield strength, Poisson's ratio, and energy absorption of circle arc hexagon (CAH), circle arc square (CAS), circle arc triangle (CAT), circle arc re-entrant (CAR), and circle arc double-V (CAD) were assessed. Both experimental and numerical results revealed that CAH demonstrates superior energy absorption while maintaining a high degree of isotropy, characterized by all isotropic factors below 0.1 in mechanical properties. Notably, CAD exhibits a Negative Poisson's ratio (NPR) effect across all loading directions. These results provide benchmarks for future studies on curved honeycombs and guide further research in this field.

Quasi-Static and Dynamic Responses of Gradient Hexachiral Auxetics: Experimental and Numerical Analysis

In the current paper, the mechanical responses of polymer gradient hexachiral auxetic metamaterials were experimentally and numerically investigated under quasi-static and intermediate strain rate loadings. Five gradient design strategies were explored, including uniform, positive, negative, center positive, and center negative gradients. The deformation/failure mechanism, Poisson's ratio, and energy absorption capability were experimentally analyzed, together with the effects of impact velocity and gradient distribution. Experimental results revealed that the gradient design can mitigate the shear deformation of hexachiral auxetics, which efficiently remain its negative Poisson's ratio effect under dynamic loading. Compare with the quasi-static loading, earlier failure of auxetics was observed under dynamic loads due to the strain rate and inertial effect, which diluted their negative Poisson's ratio effect and energy absorption capability. Among the designs, auxetics with negative gradient configurations showed the best energy absorption under dynamic loading. Numerical analysis further supported the experimental findings and provided insights into the influence of geometric parameters. It shows that thicker configurations and non-uniform node gradient series with coefficients of 1.15 (positive, center positive) and 0.87 (negative, center negative) provided optimal energy absorption under the dynamic loading. This work offers profound insights into enhanced performance mechanisms and provides avenues for optimizing structural design of auxetic metamaterials.

In‐Plane Energy Absorption Properties of Novel Curved‐Ligaments Auxetic Cellular Structures with Dual‐Platform Performance

To improve the energy absorption capacity of honeycomb, four novel curved‐ligaments auxetic cellular structures (CLACS‐i [i = 1, 2, 3, 4]) based on the Diabolo‐shaped honeycomb (DSH) are introduced in this article. In the simulation results, it is demonstrated that the energy absorption performance of CLACS‐i (i = 1, 2, 3, 4) surpasses that of DSH under low‐, medium‐, and high‐velocity impacts. However, the negative Poisson's ratio effect of novel structures is inferior to that of DSH. With the increase in impact velocity, the inertial effect of the structure is enhanced, and the deformation mode of the structure changes from global deformation to local deformation. Furthermore, different impact velocities and geometric parameters also affect the energy absorption capacity of the structures. Platform stress and specific energy absorption (SEA) of CLACS‐i (i = 1, 2, 3, 4) increase with the increase of velocity. Under medium‐velocity impact loading, the platform stress and SEA of CLACS‐i (i = 1, 2, 3, 4) increase as the geometric parameter θ decreases and the wall thickness t increases. In this study, a reference is provided for the optimal design and application of honeycomb energy‐absorbing components.

Experimental behavior and fracture prediction of a novel high-strength and high-toughness steel subjected to tension and shear loading tests

In this study, laboratory testing and numerical simulation methods are used to investigate the mechanical behavior and perform fracture prediction of a novel high-strength and high-toughness steel with a negative Poisson's ratio (NPR) effect under combined tensile-shear loading conditions. A test device capable of meeting different tensile-shear combination test angles is designed and manufactured, wherein the mechanical experiments on the NPR (Negative Poisson's Ratio) steel specimens are carried out at various testing angles. Q235 steel and MG400 steel are used as experimental control groups. The results show that the mechanical deformation of NPR steel is significantly better than that of Q235 steel and MG400 steel. Its tensile-shear test curve has no yield plateau and it has quasi-ideal elastic-plastic mechanical properties. The loading direction gradually changes from tension-dominated to shear-dominated as the tension-shear angle increases, and the strength and deformation of the specimens show a decreasing trend. Based on the laboratory test results, a finite element numerical model of NPR steel is established. A series of numerical simulations are carried out under the conditions of different tension and shear angles and the average stress triaxiality and fracture strain data are obtained. The fracture data of NPR steel are fitted using the Johnson-Cook fracture criterion, and the Johnson-Cook fracture parameters under the tensile-shear test conditions of NPR steel are thus obtained. The numerical simulation verifies that the fracture model can accurately predict the tensile-shear fracture behavior of NPR steel.

Compensation mechanics application of NPR anchor cable to large deformation tunnel in soft rock

NPR anchor cable is a new type of support material with negative Poisson's ratio effect, which is widely used in mine support because of its superb compensating mechanical effect. In order to study more deeply the support effect of NPR anchor cable in soft rock large deformation tunnel, indoor test, numerical simulation and field monitoring were used to study the strong weathering carbonaceous slate tunnel in Min County. The study shows that NPR anchor cable has extraordinary compensating mechanical behavior for soft rock large deformation tunnel, which can control the deformation of tunnel surrounding rock below 300 mm and keep the constant resistance value around 350 kN, which has obvious effect on the control of broken rock. To provide a basis for other research on support for large deformation tunnels in soft rock.

A metamaterial with enhanced effective stiffness and negative Poisson's ratio for frictional energy dissipation

Unlike traditional energy dissipation structures that dissipate energy through irreversible plastic deformation or collapse, metamaterials based on friction energy dissipation have attracted attention due to their reusability. This article proposed a novel energy dissipation metamaterial by integrating friction energy dissipation mechanism into negative Poisson's ratio (NPR) structures. The integration of friction energy dissipation mechanism can simultaneously enhance the effective stiffness and NPR effect. The mechanical properties of the proposed structure were investigated using theoretical analysis, experiments, and finite element (FE) simulations. The influence of variables such as internal concave angle, friction coefficient, and number of reinforcing ribs was discussed. The results indicate that both unit cell and honeycomb structure can repeatedly dissipate energy within the elastic range. Compared with the traditional concave hexagonal structure, the effective stiffness and NPR effect were enhanced. This work provides a novel idea for the design of NPR energy dissipation structures.

Experimental and numerical investigations of an auxetic support structure used for local repair of buried pipelines

Due to the ongoing disasters caused by local damage to underground pipelines in urban areas, a new method has been proposed for local trenchless rehabilitation of pipelines.This method utilizes the auxetic effect of an auxetic pipe structure to create support brackets inside the pipeline for repairing damaged sections, with the aim of reducing overall repair costs and improving efficiency. The main objectives of this study are to demonstrate the feasibility of using auxetic pipes for pipeline repairs and to enhance key parameters of auxetic support pipes. This paper presents a tube with auxetic support - the Surrounding Auxetic Tubular Structure (SATS). Using 3D printing technology, the preparation of SATS specimens was carried out, and the compressive properties of SATS were studied through finite element analysis and quasi-static compression test. The results show that the proposed SATS has a significant negative Poisson's ratio effect during the compression process and exhibits a high structural rebound rate after the load is removed. The size of the structure's boundary is the most influential factor on the auxetic effect. Additionally, the compression displacement of SATS increases with the increase of the elliptical short axis, and decreases with the increase of the elliptical long axis. The compressive load decreases with the increase of the short axis, and increases with the increase of the long axis. This demonstrates the excellent mechanical performance of the proposed auxetic support structure and lays the foundation for the feasibility of local repair work for trenchless rehabilitation.

A novel cylindrical mechanical metamaterial: Design, fabrication, and compressive properties

Mechanical metamaterials exhibit fascinating deformation characteristics and exceptional mechanical properties due to their distinctive unit cell structure and the repetitive development of these units. This research presents the design of a novel cylindrical metamaterial featuring a concave hexagonal structure. This design incorporates an auxetic structure within the outer circular tube in order to enhance radial shrinkage and improve bearing capacity and stability by leveraging the negative Poisson's ratio effect. The specimens were fabricated using 3D printing technology, and their mechanical properties and uniaxial compression deformation characteristics were subsequently investigated through experiments. Additionally, the accuracy of the finite element model was verified by comparing the simulated predictions with the experimental results. The specimens differ in terms of their internal and external structures. The external structures vary based on the combination of single cells and interlayers, resulting in three distinct types. The internal structures differ based on the angle of inward depression. The mechanical properties and deformation characteristics of specimens composed of different internal and external structures were analyzed, revealing that the cylindrical structure can possess adjustable stiffness, high stability, and compressive capacity.

Dynamic behaviors of sandwich panels with 3D-printed gradient auxetic cores subjected to blast load

This study experimentally and numerically investigated the blast resistance of sandwich panels composed of steel face sheets and 3D-printed gradient auxetic chiral core. Five gradient strategies were utilized in the design of auxetic core, including uniform gradient, positive gradient, negative gradient, center positive gradient and center negative gradient. Varying blast loadings were applied by adjusting the masses of explosive charges. The deformation/failure modes of sandwich panels were obtained in the experiments, in terms of the face sheets and gradient auxetic core. The effects of impulse and gradient type of auxetic core on dynamic responses of specimens were examined. In addition, the numerical simulation was employed to clarify the deformation process of sandwich panel, and to analyze the deformation mode of auxetic cores under sufficient compression. It was shown that higher impulse was associated with increased plastic deformation in the face sheet and more serious shear and tensile tearing within the auxetic core. The auxetic cores of varying gradient types displayed distinct compress deformation behaviors. Among them, the negative gradient variant exhibited the least permanent deflection, and the superior negative Poisson's ratio effect, indicating enhanced blast resistance. This work not only contributes to a strategy for designing gradient auxetic cores with enhanced blast resistance, but also provides valuable insights into experimentally understanding the response of complex auxetic configurations under blast loads.

Bottom-up strategy: A typical way to create multi-directional auxeticity in Si2O-based layered material

Layered auxetic materials have an acute demand for the in-plane negative Poisson's ratio (NPR) due to dimensional restrictions. Yet, it is not yet apparent and developed where the auxeticity in nanomaterials origins from. Aimed at inserting in-plane auxeticity, in this letter, we theoretically propose a series of Si2O-based layer-stacking materials using a bottom-up strategy. As a result of the materials' chemical O absorption, which causes the Pauli repulsion of inter-layer orbits to shift in the direction of the plane, a newly found multi-directional NPR effect is finally realized in II-BK-Si2O. Furthermore, the multilayer structures preserve dispersion of the SL-Si2O while breaking the semi-Dirac semi-metallic conditions and gapped, endowing the materials semiconducting characteristics and strong carrier mobilities. For Si2O-based materials, the aforementioned benefits open up a wide range of application possibilities and research potential.

Mechanical properties of bionic lattice and its hybrid structures based on the microstructural design of pomelo peel

Bionic design has been widely used in real life, while providing ideas for innovative design of structures. In this work, a bionic lattice structure (Y-structure) with negative Poisson's ratio effect is obtained based on the principle of bionic design by taking design inspiration from the microstructure of pomelo peel. Meanwhile, in order to reduce the fabrication difficulty, the Y structure is combined with the BCC structure to obtain four overall lattice structures containing the Y structure. The required samples are prepared by additive manufacturing technique using PA2200 as the matrix material. Quasi-static compression tests are performed on the specimens at room temperature, and the mechanical properties and energy absorption capacity of the bionic lattice structure are examined under different compression directions, considering the anisotropy of the structure. Through the experimental results, it can be found that, compared with the traditional BCC structure, the four lattice structures containing the bionic lattice show obvious anisotropy, and exhibit good mechanical properties in different directions, while the energy absorption capacity is also generally improved. However, the change in the occupancy ratio of the BCC structure has a significant effect on the mechanical properties of the mixed lattice structure. The results obtained in this study can provide valuable references for further creative new developments of lattice structures based on bionic principles.

Seismic response and failure mechanism of ordinary concrete and UHTCC short columns reinforced with negative Poisson's ratio steel bars

The replacement of ordinary steel bars by negative Poisson's ratio (NPR) steel bars to improve the seismic performance of short columns is investigated in this study. NPR steel bars is a new type of reinforcement with negative Poisson's ratio effect and high strength and ductility. In this paper, six short column members were designed. Among them, P-RC1 and P-UHTCC1 short columns were used as controls, and the remaining four specimens were reinforced by NPR steel bars. The failure mode, cracking pattern, hysteresis characteristics, plastic deformation capacity, shear strength, stiffness degradation and energy dissipation capacity of the specimens were investigated through lateral cyclic loading tests. The experimental results showed that the shear capacity of short concrete columns reinforced with NPR steel bars increased by 20.91%−22.64% and the cumulative energy dissipation capacity increased by 45.7%−63.3%. The short UHTCC columns reinforced with NPR steel bars showed an increase in shear capacity of 23.08%−35.48% and an increase in cumulative energy consumption capacity of 17.3%−28.5%. And the RC columns shear strength prediction model based on GB50010–2010 specification is relatively reasonable to be used for the evaluation of shear strength of short columns reinforced with NPR steel bars.

A Comparative Study on Impact Resistance of Cylindrical Structures with Cushioning Energy Absorbing Rings under Double Impact Loading.

In this paper, the impact resistance of a cylindrical structure with a buffer ring and an energy-absorbing ring under double impact loads is studied. Based on ABAQUS 2023 finite element software, a simulation model of a buffer ring structure with three different sibs was established, and the specimens were subjected to double impact loading. The results show that the impact resistance of the structure decreases with the increase in curvature radius. The increase in the thickness of the panel can effectively reduce the deformation difference between the center point of the panel and the maximum displacement point. The buffer ring composed of cell structure with negative Poisson's ratio effect has better shock resistance under explosion load, while the buffer ring with hexagonal cellular structure has excellent kinetic energy shock resistance.

Crushing performance of a novel tetra-missing rib honeycomb: Experimental and numerical studies

Based on the unique monoclinic characteristics of the plastic deformation of the tetra-missing rib honeycomb, the symmetrical design of the whole and subunits of the tetra-missing rib honeycomb was carried out in this paper, and two new types of tetra-missing rib honeycomb with symmetrical structural characteristics were obtained. First, quasi-static compression was performed on three structures, including a conventional tetra-missing rib honeycomb, and the experimental results showed that both symmetrical designs could effectively improve the plastic deformation of the conventional tetra-missing rib honeycomb. At the same time, round holes were introduced into the three honeycomb structures, and the mechanical properties and deformation modes of the three structures under quasi-static loads were explored. The results of two sets of experiments were compared, and it was found that the introduction of round holes could improve the structural stiffness of the honeycomb. Second, Abaqus/Explicit was used to construct a finite element numerical model in the later stage, and the accuracy of the model was verified. The number of honeycomb cells was determined for the three honeycomb structures, and finally, the dynamic Poisson's ratio of the honeycomb structure in plastic deformation was determined, and the negative Poisson's ratio (NPR) effect of the three honeycombs was compared.

On in-plane crushing behavior of an improved double-arrow auxetic metamaterial with two-step deformation mode

An improved double-arrow auxetic honeycomb metamaterial (MDAH) with two-step deformation mode was proposed and manufactured, and its in-plane crushing behavior was studied experimentally, numerically and theoretically. Quasi-static compression experiments were carried out to obtain the deformation modes and stress-strain response. The reliability of the numerical simulation was verified by experimental results. Experiments and numerical simulations have shown that MDAH exhibits a two-step deformation mode of first buckling deformation and then shrinkage deformation, with double-plateau stress characteristics. The provided theoretical results of plateau stresses are in good agreement with experimental and numerical simulation results. The effects of geometric parameters on the in-plane crushing behaviors of MDAH were further discussed through numerical simulation and theoretical analysis. The results indicate that the multi-step deformation mode of MDAH is related to the thickness and angle design of inclined rod. A suitable design can result in a stable two-step deformation mode and exhibit a negative Poisson's ratio effect. The MDAH structure has the characteristic of Poisson's ratio from positive to negative. The deformation mode and mechanical response can be regulated by changing the geometric parameters of MDAH. Compared to traditional double-arrow structures, MDAH has better energy absorption capacity. The present research can provide a new design strategy of auxetic metamaterial with deformation mode conversion and improved energy absorption efficiency.

Alloying enhanced negative Poisson's ratio in two-dimensional aluminum gallium nitride (AlxGa1-xN).

The negative Poisson's ratio (NPR) effect usually endows materials with promising ductility and shear resistance, facilitating a wider range of applications. It has been generally acknowledged that alloys show strong advantages in manipulating material properties. Thus, a thought-provoking question arises: how does alloying affect the NPR? In this paper, based on first-principles calculations, we systematically study the NPR in two-dimensional (2D) GaN and AlN, and their alloy of AlxGa1-xN. It is intriguing to find that the NPR in AlxGa1-xN is significantly enhanced compared to the parent materials of GaN and AlN. The underlying mechanism mainly originates from a counter-intuitive increase of the bond angle θ. We further study the microscopic origin of the anomalies by electron orbital analysis as well as electron localization functions. It is revealed that the distribution and movement of electrons change with the applied strain, providing a fundamental view on the effect of strain on lattice parameters and the NPR. The physical origin as revealed in this study deepens the understanding of the NPR and shed light on the future design of modern nanoscale electromechanical devices with fantastic functions based on the auxetic nanomaterials and nanostructures.

Curve beam for strengthening the negative Poisson's ratio effect of rotating auxetic metamaterial: Experiments and simulations

This article described a three-dimensional lattice design method for customizing the negative Poisson’s ratio effect in a rotating rigid structure. By using bent beams as the basic building blocks of the lattice, a new class of curved beam rotating auxetic (CBRA) lattice was proposed. Through a combination of numerical simulations and experimental tests, the mechanical responses of representative three-dimensional auxetic lattice structures under compressive load were systematically studied, including Poisson’s ratio, energy absorption, and a multi-stage deformation mode that facilitated the tuning of mechanical properties. Additionally, the influence of structural geometric parameters on the elastic performance was discussed in detail. Unlike most rotating auxetic materials that could only achieve the negative Poisson’s ratio effect within a small strain range, the results demonstrated that the uniform Poisson’s ratio of the proposed three-dimensional lattice structure could achieve positive and negative adjustment within a strain range of 0–0.5. The design flexibility would contribute to making it a promising candidate for industrial and biomedical applications, such as scaffolds and skin grafts. The acceleration of the application of new three-dimensional expandable lattice structures in engineering applications made this system more versatile than similar non-graded systems.

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.

On in-plane crushing behavior of a combined re-entrant double-arrow honeycomb

A novel re-entrant double-arrow honeycomb (RDAH) has been proposed and investigated by combining re-entrant hexagonal honeycomb and double-arrow honeycomb. Quasi-static compression experiments of 3D printed samples in different loading directions were carried out. Deformation modes and stress–strain response have been explored and identified. The corresponding finite element (FE) models were established and verified, and the dynamic crushing behaviors of RDAH were further investigated by FE simulations. The results show that RDAH has three typical deformation modes under different impact velocities. When subjected to quasi-static loading and low-velocity impact along the horizontal wall, two stress plateau regions of the stress–strain curves can be observed, while there is only one stress plateau when loaded perpendicular to the horizontal wall. Based on deformation modes, theoretical models of plateau stresses of RDAH under low-velocity and high-velocity impact were further established. The theoretical results of the plateau stresses agree well with the FE simulation results. The effects of impact velocity and geometric parameters on densification strain, Poisson's ratio and energy absorption were also discussed. The results show that the RDAH exhibits obvious negative Poisson's ratio effect in both directions. The energy absorption of RDAH is higher when loaded along the horizontal wall and can be 29.45 % higher than the traditional RH structure. The energy absorption of RDAH increases with the decrease of inclined wall l1, the decrease of inclined angle θ (perpendicular the horizontal wall), and the increase of inclined angle θ (along the horizontal wall).

Bioinspired Integrated Auxetic Elastomers Constructed by a Dual Dynamic Interfacial Healing Strategy.

Auxetic materials are appealing due to their unique characteristics of transverse expansion while being axially stretched. Nevertheless, current auxetic materials are often produced by the introduction of diverse geometric structures through cutting or other pore-making processes, which heavily weaken their mechanical performance. Inspired by the skeleton-matrix structures in natural organisms, this study reports an integrated auxetic elastomer (IAE) composed of high-modulus cross-linked poly(urethane-urea) as a skeleton and low-modulus non-cross-linked poly(urethane-urea) as a complementary-shape matrix. Benefiting from disulfide bonds and hydrogen-bond-promoted dual dynamic interfacial healing, the resulting IAE is flat, void-free, and has no sharp soft-to-hard interface. Its fracture strength and elongation at the break are increased to 400% and 150%, respectively, of the values of corrugated re-entrant skeleton alone, while the negative Poisson's ratio (NPR) reserves within a strain range of 0%-104%. In addition, the advantageous mechanical and auxetic properties of this elastomer are further confirmed by finite element analysis. The concept of combining two dissimilar polymers into an integrated hybrid material solves the problem of the deterioration in mechanical performance of auxetic materials after subtractive manufacturing, while preserves the NPR effect in a large deformation, which provides a promising approach to robust auxetic materials for engineering applications.