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Auxetic materials hold tremendous potential for many advanced applications, but candidates are quite scarce, especially at two dimensions. Here, we focus on two-dimensional (2D) metal dichalcogenides and dihalides with the chemical formula MX2 by screening structures sharing the P 4 ̄ m2 space group among 330 MX2 compounds from the computational 2D materials database. Via high-throughput first-principles computations, 25 stable MX2 (M = Mg, Ca, Mn, Co, Ni, Cu, Zn, Ge, Cd, Sn; X = F, Cl, Br, I, O, S, Se) systems with in-plane negative Poisson's ratios (NPRs) are successfully identified. Within these structures, 2D NiCl2 has the largest NPR value of −0.34, with a magnitude significantly higher than those of black phosphorene (−0.027) and SnO2 (−0.1). The distinct auxetic effect in MX2 originates from both the unique local corner-sharing tetrahedral structural motif under the low-dimensional effect and the strong orbital interaction between the d orbitals of M and the p orbitals of halogen/chalcogen atoms. As a result, Poisson's ratio can be effectively tuned by enhancing the d–p interaction through an external biaxial strain. We reveal that these auxetic materials exhibit rich electronic and magnetic properties, covering nonmagnetic, ferromagnetic, or anti-ferromagnetic metals, semiconductors, and insulators. The extraordinary auxetic behaviors in combination with rich physical properties could lead to multifunctional nanomechanical, optoelectronic, and spintronic applications. [ABSTRACT FROM AUTHOR]

Machine learning is a promising method to model production processes and predict product quality. It is challenging to accurately model complex systems due to data scarcity, as mass customisation leads to various high-variety low-volume products. This study conceptualised knowledge accumulation, extraction, and transfer (KAET) to exploit the knowledge embedded in similar entities to address data scarcity. A sequential cross-product KAET (SeqTrans) is proposed to conduct KAET, integrating data preparation and preprocessing, feature selection (FS), feature learning (FL), and transfer learning (TL). The FS and FL modules conduct knowledge extraction and help address various practical challenges such as changing operating conditions and unbalanced datasets. In this paper, sequential TL is introduced to production modelling to conduct knowledge transfer among multiple entities. The first case study of auxetic material performance prediction demonstrates the effectiveness of sequential TL. Compared with conventional TL, sequential TL can achieve the same test mean square errors with 300 fewer training examples when facing data scarcity. In the second case study, balancing anomaly detection models were constructed for two gas turbines in the same series using real-world production data. With SeqTrans, the F1-score of the anomaly detection model of the data-poor engine was improved from 0.769 to 0.909. [ABSTRACT FROM AUTHOR]

In this study, two innovative unit cell designs were developed by combining different auxetic structures from the literature, and they were fabricated using 3D printers, one of the most popular additive manufacturing methods today. Tensile and compression samples were created based on unit cells produced with various parameters to investigate the mechanical properties of auxetic structures and their viability in the additive manufacturing field. Nowadays, polymer-based materials are widely accepted as the primary materials for 3D printing technology, which is employed in various engineering applications, including additive manufacturing. In this context, the samples were produced using PLA, subjected to tensile and compression tests, and their mechanical properties were analyzed. Additionally, finite element analysis (FEA) was utilized to simulate the tensile and compression tests in a virtual environment, and the results were compared with the experimental data. It was observed that the tensile and compressive strengths of the unit cell increased as the angle between the branches forming the unit cell decreased. Moreover, increasing the thickness of the branches that make up the unit cell also resulted in higher tensile and compressive strength values. [ABSTRACT FROM AUTHOR]

AbstractIn this study, based on star-shaped honeycomb (SSH), a novel auxetic honeycomb metamaterial, i.e. star folded rod honeycomb (SFRH), is proposed to simultaneously improve the load-bearing capacity (i.e. Young’s modulus and Shear modulus) and negative Poisson’s ratio (NPR) performance. The in-plane elastic properties of SFRH are analyzed by combination of theoretical expression derivation, finite element (FE) simulation and experimental validation, and the dependencies between various in-plane elastic properties and different geometrical parameters of SFRH are determined. It is demonstrated that higher load-bearing capacity and NPR effect are exhibited by SFRH as compared to other honeycombs with star-shaped characteristic. [ABSTRACT FROM AUTHOR]

This paper reviews the advancements and potentials in Knitted Negative Poisson Ratio (NPR) materials, including warp-knitted, weft-knitted, and three-dimensional (3D) knitted structures. The review includes 10 sections the following order: a general introduction, defection of the NPR, the auxetic textile fabrics, warp and weft knitted, the 3D, the mechanical properties of auxetic knitted structure, advantages and drawbacks, and the future trends. However, research on knitted textile structures with Negative Poisson Ratio is limited in the literature so far. This type of material with unusual properties and 3D negative stiffness textile structure has been of interest for fundamental research, and engineering applications. Nonetheless, there is a need for a systematic study of their structural design and manufacturing process and their performance for further exploitation. Among different design structures, various structures have been designed and made to show the properties of (NPR). These negative Poisson ratio textiles knitted structures will enable new applications such as vibration isolation for transportation, defense Industries, aerospace, biomedical, sports industries, geotextile, construction, and many more high-value-added and innovative products. [ABSTRACT FROM AUTHOR]

AbstractThis research utilized higher-order shear deformation theory to model and analyze the thermomechanical vibration buckling behavior of auxetic core layered smart sandwich plates. The surface layers of the smart plate consist of magneto strictive CoFe2O4 (Cobalt Ferrite) and electro elastic BaTiO3 (Barium Titanate) materials. The hexachiral auxetic core layer consists of the metal biomaterial Ti-6Al-4V, which includes various auxetic cell parameters. This study analyses the effects of Auxetic core layer parameters on the thermo-mechanical vibration buckling behavior of the smart sandwich plate, along with the influence of external electrical and magnetic potentials applied to the surface plates over a wide range. The findings demonstrate that the thermo-mechanical buckling behavior of the smart sandwich plate can be regulated by appropriately adjusting the Auxetic cell and applying external electric and magnetic potentials. The findings of this study will facilitate the design of smart electromechanical systems suitable for high-temperature environments. [ABSTRACT FROM AUTHOR]

The convergence of 3D printing and auxetic materials is paving the way for a new era of adaptive structures. Auxetic materials, known for their unique mechanical properties, such as a negative Poisson's ratio, can be integrated into 3D-printed objects to enable them to morph or deform in a controlled manner, leading to the creation of 4D-printed structures. Since the first introduction of 4D printing, scientific interest has spiked in exploring its potential implementation in a wide range of applications, from deployable structures for space exploration to shape-adaptive biomechanical implants. In this context, the current paper aimed to develop 4D-printed arterial stents utilizing bioinspired architected auxetic materials made from biocompatible and biodegradable polymeric material. Specifically, three different auxetic materials were experimentally examined at different relative densities, under tensile and compression testing, to determine their mechanical behavior. Based on the extracted experimental data, non-linear hyperelastic finite element material models were developed in order to simulate the insertion of the stent into a catheter and its deployment in the aorta. The results demonstrated that among the three examined structures, the 'square mode 3' structure revealed the best performance in terms of strength, at the same time offering the necessary compressibility (diameter reduction) to allow insertion into a typical catheter for stent procedures. [ABSTRACT FROM AUTHOR]

Auxetic metamaterials, known for their unusual properties, are being explored as cores for sandwich structures to improve impact resistance. This study investigated the low-velocity impact response of sandwich panels with various core designs using finite element method (FEM) and experiments on 3D-printed specimens. These cores include pure honeycomb, pure auxetic, and gradient variations with controlled gradients of Poisson's ratio, transitioning from negative to positive (NTP), positive to negative (PTN), negative-to-positive-to-negative (NTPTN), and positive-to-negative-to-positive (PTNTP). These gradients were achieved by adjusting the unit cell angle within the core. Under quasi-static indentation, the gradient PTN design improved energy absorption by 26% compared to the honeycomb structure, while the gradient NTP structure showed a 9% improvement over the auxetic core. As for the impact tests, the gradient NTP and PTN structures significantly enhanced the indentation resistance of auxetic and honeycomb structures by 21.3% and 6.5%, respectively. Interestingly, while the optimal core for peak energy absorption varied with impact velocity, gradient structures generally provided superior energy absorption, particularly at lower velocities. FEM results at initial impact velocities of 10, 15, 20 m/s confirmed that structures having negative Poisson's ratio at their top layer exhibited the lowest penetration depth. Additionally, gradient structures, particularly NTP and NTPTN, demonstrated superior energy absorption capability compared to purely auxetic or honeycomb structures, especially at lower velocities. The study highlights the benefits of utilizing gradient auxetic metamaterial cores in high-performance sandwich structures for impact resistance applications. These structures showed minimal localized damage, reduced densification risk due to uniform crushing, and lower penetration depth. [ABSTRACT FROM AUTHOR]

This research has been conducted to analyze the free vibration behavior of a five-layered composite plate with a viscoelastic auxetic core. The plate comprises a viscoelastic auxetic core layer, functionally graded carbon nanotube reinforced composite (FG-CNTRC) interior, and magneto-electro-elastic functionally graded porous (MEE–FGP) exterior skins, which is rested on Winkler–Pasternak foundation. According to the magnetic–electric boundary conditions and Maxwell equations, the electric and magnetic potentials of the plate are determined. The macro-mechanical properties of the auxetic core have been derived based on Gibson's model; the three-parameter Zener model has also been utilized to describe its viscoelastic behavior. Additionally, the equations of motion of the plate are obtained and solved by using Reddy's third-order shear deformation theory (TSDT) and the Galerkin method, respectively. Moreover, various aspects of the current research have been validated by comparing the numerical results with those reported in the literature section. Overall, in the numerical result section, the effects of different parameters and conditions such as geometrical parameters, position of the plate's interfaces of layers (thickness of the core and face layers), various distribution patterns and volume fractions of both CNT and porosity, external work parameters of the MEE skins, boundary conditions, Winkler–Pasternak stiffness coefficients, the relaxation time, and other parameters of the viscoelastic core on the natural frequency and loss factor of the composite plate are represented. [ABSTRACT FROM AUTHOR]

Auxetics have emerged recently as an exciting class of mechanical metamaterials that are identified by negative Poisson's ratio. The mechanical properties of rationally designed auxetic metamaterials are mostly influenced by their topological characteristics rather than the material properties of their constituent material. The goal of this paper is to use optimization algorithms to achieve the desired target mechanical properties for reentrant auxetic metamaterials. The GEKKO optimization package in Python is used for optimizing the geometry of auxetic lattice structures. Several mechanical properties including Poisson's ratio, relative Young's modulus, relative yield stress, and relative energy absorption capability, as well as the noted properties normalized with respect to relative density and relative Young's modulus are chosen for being minimized or maximized. ANSYS finite element package is also implemented for validation of the results obtained from the optimization algorithm. According to the results, to achieve the maximum magnitude of Poisson's ratio (positive and negative), the size of the unit cell in the lateral direction must be selected to be maximum and the thickness must become minimum. Moreover, to achieve the maximum value of the relative Young's modulus or energy absorption in any direction, the size of the unit cell in that direction must be maximized. Also, to achieve the maximum amount of relative yield stress in both directions, the unit cell must have a maximum thickness and an internal angle close to zero. [ABSTRACT FROM AUTHOR]

Purpose: Fused filament fabrication (FFF) is a widely used 3D printing technique for the fabrication of mechanical metamaterials with intricate geometries. Gradient strategy is applied to geometric parameters of gradient star re-entrant hybrid auxetic (GSRA) structure. Deformation behaviour is studied under compressive loading. The purpose of this study is to investigate the influence of gradient geometric parameters on mechanical properties, namely, specific strength (SS), specific modulus (SM) and specific energy absorption (SEA). Design/methodology/approach: Response surface methodology (RSM) is implemented for the design of experiments of gradient geometric parameters to minimize the number of experimental tests. Acrylonitrile butadiene styrene material is used for the fabrication of GSRA structures by FFF technique. The best set of gradient parameters has been optimized maximizing all three responses using RSM and artificial neural network optimization technique. Findings: During compressive testing, row-wise deformation is observed with two-stage plateau regions, which results in increase in SEA of the structure. Furthermore, based on analysis of variance and 3D response plots, it is found that height gradient is the most influencing gradient geometric parameter on SS and SM, whereas the wall thickness gradient has maximum influence on SEA. Meanwhile, the interaction effect of wall thickness gradient and height gradient has maximum influence on SS, SM and SEA. Research limitations/implications: This study of applying gradient strategy to geometric parameters is limited to GSRA structure under compressive loading. In addition, findings are valid within the selected range of gradient geometric parameters. These findings are useful for the selection of gradient geometric parameters to maximize SS, SM and SEA of GSRA structure simultaneously. These outcomes pave the way for designing light-weight gradient hybrid auxetic structures in the field of construction, aerospace, automobile and biomedical engineering. Originality/value: Limited experimental study is available on investigating the influence of gradient geometric parameters on mechanical properties, namely, SS, SM and SEA, and deformation behaviours of hybrid auxetic structures. This study directly addresses the above research gaps. [ABSTRACT FROM AUTHOR]

The presented study illustrates the use of photoelasticity as an effective tool for validating the results of finite element method (FEM) simulations of auxetic structures. This research focuses on comparing stress distributions in planar auxetic models under symmetrical and asymmetrical loading conditions. Experimental measurements, conducted using an optically sensitive material (PSM-1), were found to align closely with FEM predictions, with deviations within 5%. This agreement highlights the accuracy of both methods, though discrepancies were noted in areas with lower stress levels due to fringe order reading precision. The experimental process makes it possible to take into account real conditions and inaccuracies in production, while numerical modelling is based on ideal conditions. The findings affirm the value of photoelasticity for stress field analysis in complex geometries, particularly for auxetic structures, and underscore its role in verifying and refining computational models. The study concludes that photoelasticity can be a valuable tool for designers and engineers in verifying FEM simulations, even without the use of digital processing and the evaluation of measured data. [ABSTRACT FROM AUTHOR]

AbstractThe transportation industry is under increasing pressure to reduce weight and volume while enhancing safety to meet evolving standards. One effective solution is the adoption of lightweight structures in vehicle design. Cellular structures, known for their lightweight and energy absorption properties, are highly applicable in this context. Auxetic metamaterials, a new class of cellular materials with a negative Poisson’s ratio (NPR), expand under tensile load and densify under compressive load. This unique behavior improves performance and crashworthiness compared to conventional materials. This study examines the crushing performance and crashworthiness of the reentrant diamond auxetic (RDA) metamaterial, a previously unstudied type. Using the design of experiments (DOE), the study explores how structural parameters influence dynamic crushing and crashworthiness. Response surface-based surrogate models and multi-objective optimization are used to balance injury-based and energy-based crashworthiness metrics, which often conflict. The optimized structure achieves an energy absorption of 2669 J and a specific energy absorption (SEA) of 10.5 J/g, representing improvements of 71% and 22% over regular reentrant auxetic metamaterials and 230% and 42% over hexagonal honeycomb structures of the same unit cell size, respectively. [ABSTRACT FROM AUTHOR]

This study addresses a critical gap in the literature by investigating the static and natural frequency characteristics of functionally graded (FG) auxetic metamaterial annular plates reinforced with graphene origami (GOri), a novel area previously unexplored in the context of composite constructions, particularly for circular plates. The governing equations are derived utilizing higher-order shear deformation theory along with Hamilton’s principle, and solved using the finite element approach. For the first time, a comprehensive parametric study including the folding degree and mass fraction, and distribution pattern of GOri, is investigated on the static and natural frequency properties of annular plates. It is found that the natural frequency generally increased with higher mass fractions and decreased with greater folding degrees, though the X and V patterns at a 3% mass fraction showed an atypical increase in frequency with higher folding degrees. The impact of distribution patterns varied with weight fraction: the X-pattern caused the highest deflection at 1% weight fraction but the lowest at 3%, while the O-pattern caused the least deflection overall. [ABSTRACT FROM AUTHOR]

AbstractThis study examines the free vibration and nonlinear transient response of functionally graded graphene origami-enabled auxetic metamaterial (GOEAM) cylindrical shells under thermal conditions. The multilayered shells feature GOri distributions across their thickness, introducing distinct auxetic and thermal properties. Material properties are modeled using micromechanical models optimized via genetic programming. Employing Reddy’s third-order shear deformation theory and von Kármán’s nonlinear geometric assumptions, nonlinear kinematic relationships are formulated and solved using Galerkin method. A novel contribution is the analysis of Winkler-Pasternak elastic foundations in two configurations: centrally distributed along the shell length and concentrated at both ends. Foundation effects are quantified by integrating stiffness coefficients across contact areas, offering insights into foundation-shell interactions. Artificial Neural Networks (ANNs) are developed to predict natural frequencies with high accuracy. Trained using the Levenberg-Marquardt algorithm and tan-sigmoid transfer function, these models demonstrate robust performance through metrics like validation performance plots, regression analysis, and error histograms. Validation against literature confirms the reliability of both ANN and analytical approaches. Key findings reveal that increased GOri folding enhances the negative Poisson’s ratio but reduces Young’s modulus, decreasing shell stiffness, natural frequencies, and increasing vibration amplitudes. Additionally, centrally concentrated elastic foundations yield higher natural frequencies and smaller vibration amplitudes compared to foundations distributed at the shell ends. By integrating advanced analytical techniques with state-of-the-art ANN modeling, this study not only provides a comprehensive understanding of the dynamic behavior of FG-GOEAM cylindrical shells but also offers valuable insights for the design, optimization, and application of auxetic metamaterial structures in thermal environments. [ABSTRACT FROM AUTHOR]

Lattice structures (LSs) are increasingly celebrated for their lightweight characteristics and superior mechanical performance. In this research, a strut reinforcement technique was employed to enhance the energy absorption capacities of 3D re-entrant auxetic (Aux), hexagonal (Hex), and hybrid auxetic-hexagonal (AuxHex) lattice structures. The investigation involved finite element analysis (FEA) to delve into the mechanical and energy absorption properties of these novel designs during quasi-static compression testing. To accurately simulate the mechanical behavior of the 3D-printed lattice structures, the mechanical properties of the PA2200 matrix material—manufactured via 3D printing—were utilized. The results from the uniaxial loading tests of the reinforced designs were then compared with those from traditional 3D hexagonal and re-entrant auxetic lattice structures. The elastic modulus of the reinforced designs was improved by 130% for hexagonal structure, 85.78% for auxetic structure, and 168.26% for hybrid auxetic-hexagonal structure at a 2 mm strut diameter. Similarly, the reinforced designs showed a significant increase in volumetric energy absorption (W). Reinforced Hex structure had a 153% improvement in W, whereas reinforced Aux and AuxHex structures showed an increase in W by 162.4% and 119.09%, respectively. Comparing energy absorption properties of all structures at the same relative density, the W of the reinforced hexagonal structure was found to be the highest. The experimental validation of the compression responses of the 3D-printed lattice structures demonstrated good agreement in terms of elastic modulus, yield stress, peak stress, and deformation modes. Finally, the deformation patterns of the reinforced auxetic and hexagonal structures were identified to be a combination of bending and stretching dominating, resulting in increased stiffness, load-bearing capacity, and weight efficiency. [ABSTRACT FROM AUTHOR]

Piezoelectric ceramics are widely used in a wide range of applications. In the development to enhance their application performance, designing special structures is considered as a potential strategy. However, piezoelectric ceramics with complex structures are difficult to realize due to their hard and brittle nature. In this work, a negative Poisson's ratio structure (auxetic) is introduced into preparing a lead zirconate titanate (PZT) ceramic using the 3D printing method. The 3D-printed complex structural ceramics show expected piezoelectric and ferroelectric properties as well as good vibration performance. After encapsulation, the device possesses ultrasonic sensing properties and shows 5–8 times better mechanical sensing performance compared to conventional block ceramics. These results indicate that the 3D-printed auxetic structure improves the deformability and sensitivity of piezoelectric ceramic pieces, which opens up more possibilities for the fabrication of new and excellent piezoelectric devices. [ABSTRACT FROM AUTHOR]

AbstractThe perforated auxetic tube with peanut-shaped perforations (PHT) are proposed and its mechanical responses are investigated by three-point bending experiment and validated finite element simulation. Compared to the auxetic tube with elliptical perforations (EHT) under the same porosity, the PHT exhibits significant improvement of up to 100%, 49%, 34%, and 148% in peak force, bending stiffness, ductility and energy absorption capacity, respectively. Additionally, a parametric analysis is performed to identify the role of each design parameter and provide optimal solutions for the PHT design. This study provides valuable guidance for enhancing the bending mechanical properties of perforated auxetic tubes. [ABSTRACT FROM AUTHOR]

The introduction of 3D printing technology has broadened manufacturing possibilities, allowing the production of complex cellular geometries, including auxetic and curved plane structures, beyond the standard honeycomb patterns in sandwich composite materials. In this study, the effects of cell design parameters, such as cell geometry (honeycomb and auxetic) and cell size (cell thickness and width), are examined on acrylonitrile butadiene styrene (ABS) core materials produced using fusion deposition modeling (FDM). They are produced as a result of the epoxy bonding of carbon epoxy prepreg composite materials to the surfaces of core materials. Increasing the wall thickness from 0.6 mm to 1 mm doubled the elastic modulus of the re-entrant structures (5 GPa to 10 GPa) and improved compressive strength by 50–60% for both geometries. In contrast, increasing cell size from 6 mm to 10 mm significantly reduced compressive strength by 80% (from 2.5–2.8 MPa to 0.5–0.6 MPa) and elastic modulus by 70–78% (from 9–10 GPa to 2–3 GPa). Flexural testing showed that the re-entrant cores, with a maximum load capacity of 148 N, exhibited more uniform deformation, while the honeycomb cores achieved a higher load capacity of 273 N but were prone to localized failures. These findings emphasize the directional anisotropy and specific advantages of auxetic and honeycomb designs, offering valuable insights for lightweight, high-strength structural applications. [ABSTRACT FROM AUTHOR]

This paper presents, for the first time, an effective numerical approach based on the isogeometric analysis (IGA) and the six-variable quasi-three dimensional (3D) higher-order shear deformation theory (HSDT) to study the free vibration characteristics of functionally-graded (FG) graphene origami (GOri)-enabled auxetic metamaterial (GOEAM) plates submerged in a fluid medium. The plate theory incorporates the thickness stretching and the effects of transverse shear deformation without using any shear correction factors. The velocity potential function and Bernoulli's equation are used to derive the hydrodynamic pressure acting on the plate surface. Both horizontally and vertically immersed plate configurations are considered here in the form of inertia effects. The plates are composed of multilayer GOEAMs, with the GOri content varying through the plate's thickness in a layer-wise manner. This design results in graded auxetic growth. The material properties are evaluated by mixing rules and a genetic programming (GP)-assisted micromechanical model. The governing equations of motion for the FG-GOEAM plates immersed in a fluid medium are derived by Hamilton's principle. After validating the convergence and accuracy of the present model, a comprehensive parametric study is carried out to examine the effects of the GOri content, GOri distribution pattern, GOri folding degree, fluid level, immersed depth, and geometric parameter on the natural frequencies of the FG-GOEAM plates. The results show that the natural frequencies for the four GOri distribution patterns increase with the increase in the layer number when the lay number is fewer than 10, and then stabilize after the layer number reaches 10. Besides, in general, the natural frequency of the FG-GOEAM plate in a vacuum or fluid increases when the GOri content increases, while decreases when the GOri folding degree increases. Some additional findings related to the numerical results are presented in the conclusions. It is believed that the present results are useful for the precise design and optimization of FG-GOEAM plates immersed in a fluid medium. [ABSTRACT FROM AUTHOR]

This study investigates the high-impact behaviour of auxetic materials, recognised for their negative Poisson’s ratio and exceptional energy absorption, when combined with shape memory alloys to enhance impact resistance. Using finite element analysis in Abaqus, 42 unique auxetic models were developed with variations in angles, thicknesses, heights, and lengths to examine structural response under high-velocity impacts. The findings reveal that modifications to the height-to-length ratio, thickness-to-length ratio, and cell design angle significantly affect residual projectile velocity – reducing it by up to 17%, fully eliminating it in some cases, or increasing it by 34% depending on the configuration. These adjustments also influence energy absorption rates and specific energy absorption during collision events. Poisson’s ratios, derived through both analytical and numerical methods, showed strong agreement, validating the accuracy of the models. Overall, the study ident ifies optimal design configurations that maximise energy absorption and minimise projectile velocity upon impact. These findings have practical implications for industries requiring durable materials in high-impact applications, and the integration of auxetic structures with shape memory alloys suggests promising directions for innovative material design. [ABSTRACT FROM AUTHOR]

Mechanical metamaterials exhibit special properties that cannot be realized in traditional materials. To enable a metamaterial with a sequential Poisson's ratio and controllable expansion, a 2D-graded hybrid re-entrant honeycomb is designed in this work by coupling graded re-entrant unit cells with negative and positive Poisson's ratios. The correlation between Poisson's ratio and structural location under tension is studied by finite element analysis and experiments. The influence of microstructural parameters, including base angle, height ratio, and internal angle, on the relationship between the Poisson's ratio and structural location is systematically analyzed. The theoretical analysis shows that the 2D-graded hybrid metastructures exhibit auxetic behavior with a linearly declined Poisson's ratio along the tensile direction due to the introduction of a height ratio, resulting in gradual expansion and elongation. Furthermore, adjusting the variation of internal angles at a small height ratio can enhance the negative Poisson's ratio of the 2D-graded hybrid re-entrant honeycomb. Finally, a 3D-graded conical metastructure exhibiting linear auxeticity is constructed based on the 2D-graded lattice. Considering their designed linearity of deformation under tension, the 2D- and 3D-graded metastructures can facilitate the design of conical profiles for an extendable rocket nozzle and other deployable devices. [ABSTRACT FROM AUTHOR]

This article investigates the static and dynamic buckling behavior of a double-curved sandwich shell composed of two layers via improved first-order shear deformation theory without using the shear correction is utilized to model the sandwich shell. The sandwich two-layer shell are held together by elastic pins, each layer made from an ultra-light auxetic honeycomb core layer (negative Poisson's ratio) and is reinforced by a layer of tri-phase polymer, graphene nanoplatelets (GNP), and fiber. The double-curved sandwich shell is supported by a Kerr elastic medium in hygro-thermal environment assuming that temperature and humidity only cause forces to be applied tangentially to the shell and do not change the mechanical properties of the shell material. The motion equations of sandwich two-layer shell are derived by Hamilton's principle, then the finite element method and Bolotin method are used to derive the dynamic instability region of sandwich two-layer shell. The accuracy of these results is confirmed by a comparison with established statements within the specific conditions of the problem model. The influence of inputs on the static and dynamic stability of sandwich two-layer shell is fully explored and discussed. Additionally, this serves as a crucial foundation for the calculation and design of structures that can integrate a variety of materials with different properties with low cost and simplification. [ABSTRACT FROM AUTHOR]

This paper is dedicated to the analysis of a foot prosthesis optimization process, with a particular focus on the application of optimization algorithms and unconventional materials, such as auxetic materials. The study aims to enhance prosthesis performance by minimizing the difference between the ground reaction force generated by the prosthetic foot and that of a natural limb. In the initial part of the study, the basic topics concerning the parameterization of the foot prosthesis geometry and the preparation of a finite element model for human gait are discussed. In the subsequent part of the study, the focus is on the optimization process, in which algorithms were applied to adjust the prosthesis structure to the patient's individual needs. The optimization process utilized a finite element method gait model. After validating the FEM, an algorithm generating the prosthesis geometry based on the given parameters was developed. These parameters were optimized using the VOA, comparing FEM gait model data on vertical ground reaction force with experimental results. The results of the foot prosthesis optimization are presented through a comparison of different structural models. The study also demonstrates the application of auxetic materials, which, due to their unique mechanical properties, can enhance foot prosthesis efficiency. Simulations were performed using multi-material topology optimization. The results obtained for different gait phases were compared. [ABSTRACT FROM AUTHOR]

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A re‐entrant honeycomb structure stands out as one of the most prevalent auxetic metamaterials, characterized by its negative Poisson's ratio. While re‐entrant auxetic structures are capable of achieving tunable Poisson's ratios, they tend to vary with the magnitude of applied strain, thereby exhibiting nonlinear auxetic behaviors. This study proposes a novel re‐entrant structure aimed at achieving linear auxetic behavior by mathematically modifying the shape of a re‐entrant cell. To achieve this objective, a sigmoid‐based shape morphing function is introduced to modify the morphology of the hinge connections within the re‐entrant honeycomb cell. The deformation behavior of the shape‐morphed re‐entrant cell is investigated using finite element analysis (FEA), with variations in the morphing parameter. Two FEA models, namely the unconstrained and constrained models, are developed for fundamental analysis of cell deformation and experimental validation, respectively. Compared to the pure re‐entrant honeycomb structure, the proposed shape morphing reduces the relative variation of Poisson's ratio by 70%, while maintaining its magnitude higher than 1.0. This achievement of linear auxetics with a high Poisson's ratio has the potential to broaden the applications of the proposed auxetic structures to various functional components, including sensors with high linear sensitivity and soft actuators with tunable deformation characteristics. [ABSTRACT FROM AUTHOR]

Using novel materials, including auxetic structures, has witnessed significant growth. Consequently, a comprehensive examination of their mechanical behavior becomes imperative. This study delves into the free vibration characteristics of a three-layer cylindrical shell containing liquid. The central layer of this structure features a re-entrant honeycomb auxetic pattern, while the inner and outer layers are assumed to be isotropic and constructed from aluminum. The liquid within the shell is considered ideal and incompressible, with no consideration for wave effects on its free surface. To model this problem, we employ a modified high-order shear deformation theory (HSDT). By applying Hamilton's principle, we derive fundamental equations and solve them using the Galerkin weighted residual method. We compare our findings with results published in authoritative articles and outcomes obtained from finite element analysis in ABAQUS to validate them. Our investigation explores the impact of various parameters on the natural frequencies of the cylindrical body. These parameters include the geometrical dimensions of the sandwich cylindrical cover, adjustable auxetic core parameters, and liquid characteristics. Given the widespread use of cylindrical sandwich shells across diverse industries, our study provides valuable insights into the phenomenon of free vibration in these structures. Remarkably, previous studies have not investigated the free vibration of a three-layered cylindrical shell with an auxetic structure and liquid interaction. [ABSTRACT FROM AUTHOR]

Based on Euler-Bernoulli beam theory, the equivalent elastic properties of auxetic cellular structure with irregular configurations are derived by using the representative unit cell element approach and multi-step bottom-up approach. Meanwhile, the effect of cell height and inclination angle on the in-plane linear elastic properties is explored. In addition, the Mechanical properties of the auxetic cellular structure with gradient cell height are analyzed under quasi-static compressive loading. The results show that the theoretical derivation results agree well with the results from available literature. The failure of all structures is the layer-by-layer collapse of cellular structural cells. The gradient cell size has little effect on the elastic phase of stress-strain behavior and energy absorption performance. The bidirectional gradient structure has higher platform stress compared with the unidirectional gradient structure. The homogeneous small size structure has the strongest load-bearing capacity as well as energy-absorbing performance. The structure, unidirectional gradient from large to small size, has the weakest load bearing capacity. [ABSTRACT FROM AUTHOR]

Auxetic metamaterials are a class of material with tunable Poisson's ratio. Nonetheless, most auxetics have weak mechanical properties, thus, implementing graphene origami (GOri) as a strong reinforcement can overcome this deficiency. This review explores the burgeoning field of auxetic metamaterials enhanced through the integration of graphene origami. This study also presents an in-depth investigation of the background of negative Poisson's ratio auxetic metamaterials, most importantly, graphene origami. Furthermore, it focuses on the notable mechanical characteristics such as increased flexibility, strength, and dynamic response of GOri-reinforced composites. Leveraging Hamilton's principle and other theoretical frameworks, this paper collates and examines the equation of motion derivations and the impact of various parameters on GOri behaviour. [ABSTRACT FROM AUTHOR]

This work introduces a quasi-3D refined theory for assessing the transient dynamic reactions of a sandwich annular sector plate subjected to mechanical shock loading. The sandwich structure has two facesheets composed of graphene origami (GOri)-enabled auxetic metal metamaterials (GOEAMs) and a core composed of carbon fiber reinforced polymer. The auxetic quality of the annular plates is mainly determined by the quantity of graphene and the level of folding in the GOri material. The elements are assessed layer by layer across the thickness of the plates. Micromechanical models supported by genetic programming may be used to predict the position-dependent Poisson's ratio and other material parameters. The concept of Hamiltonian is used to deduce the governing equations of the structure. The equations of motion, which vary with time, are solved using the numerical solution process and the Laplace transform. A comprehensive parametric study is carried out to examine the influence of various geometric and physical parameters on the time-dependent behavior of annular sector plates. The current mathematical modeling results are being compared to the findings of previous works, as well as a machine learning technique. By using this machine learning methodology, it is feasible to computationally solve differential equations at a reduced expense, while simultaneously surmounting the challenge of formulation. To use machine learning techniques, a dependable dataset acquired from either experimental or numerical analysis is necessary. The dataset was created using the quantitative findings of the investigation. Furthermore, the machine learning technique demonstrates its capacity to provide very precise outcomes when predicting the transient behavior of the existing structure under novel loading and boundary circumstances. [ABSTRACT FROM AUTHOR]

Thin-walled tubes are widely used as energy absorbers to increase the crash resistance and safety while maintaining lightness. There has been an increase in interest in the integration of auxetic structures into these tubes. This is due to the better mechanical strength displayed by auxetic structures with negative Poisson's ratio, particularly in terms of compressive behavior and energy absorption. In this study, a group of square-section tubes with different types of cell structures on their side faces was examined. Under quasi-static compression, the behaviors of thin-walled square tubes with reentrant auxetic and conventional honeycomb were examined numerically and experimentally. In addition, geometric optimization of reentrant cell shape was performed to maximize the compressive loading of the square tubes. First, the compression behaviors of thin-walled square tubes made of polylactic acid (PLA) were examined; these tubes' side surfaces have both conventional and reentrant auxetic honeycomb cellular patterns. The reentrant auxetic and conventional honeycomb cell architectures were applied together and separately on the side faces of the thin-walled tube, with the identical cell parameters. In order to better understand the deformations, force-displacement curves were examined for four different types of thin-walled square tubes, including tubes with reentrant auxetic and honeycomb cell structures on all side faces and tubes with these structures on opposite sides and adjacent. Using the ANSYS finite element software package and Digimizer image processing programs, the Poisson's ratio of the reentrant auxetic and conventional honeycomb configurations as well as the maximum compression force of the tubular structures were determined numerically and experimentally. After obtaining the result that the use of the reentrant auxetic structure on the side surfaces of the square tube significantly increased the compression resistance and energy absorption capability of the tube, the optimization of the square tube with the reentrant auxetic structure on all surfaces was examined. The effect of the geometrical parameters such as ligament length, reentrant angle, and cell thickness of the unit-cell on the compression load of the square tube was investigated using an integrated methodology combining numerical simulation and DoE (Design of Experiments) method. The findings show that the tubes combined reentrant auxetic structure exhibits better energy absorption than the conventional honeycomb tubes. It also reveals that the optimum geometric parameters of the reentrant auxetic unit cell are to be the ligament length of 16.358 mm, the ligament angle of 80°, and the ligament thickness of 3 mm. [ABSTRACT FROM AUTHOR]

Vibrational behavior of a shear deformable cylindrical shell is studied in this article based on Hamilton's principle. The shell is manufactured by a Copper (Cu) core reinforced with graphene origami auxetic metamaterial and subjected to mechanical and thermal loads. The constitutive relations are developed based on the shear deformable model where the effective modulus of elasticity, Poisson's ratio, and density are evaluated using micromechanical models including volume fraction and folding degree of graphene origami auxetic metamaterial, geometric characteristics of graphene, material properties of matrix, and reinforcement and local temperature. The natural frequencies are obtained based on Navier's and Galerkin's approaches for simply supported, clamped-simply, and clamped-clamped boundary conditions. The formulation, solution procedure, and numerical results are confirmed through comparison with the available results of the literature. The complete numerical results are presented in terms of volume fraction and folding degree of graphene origami auxetic metamaterial, thermal loading, and various types of boundary conditions. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of a sandwich structure featuring an auxetic core, manufactured through Vacuum Assisted Resin Transfer Molding (VARTM) using carbon-aramid hybrid fibers. The core was 3D printed with polylactic acid (PLA). Experimental testing of the structure provided results for validating a cost-effective numerical model. The response surface methodology identified results for different sandwich panel configurations, revealing that auxetic behavior depends on the core's adopted configuration. Increasing the fiber-core contact area induces auxetic behaviors. The structure underwent optimization using the Lichtenberg algorithm, yielding models with 40.32% higher failure load, 36.36% higher natural frequency, and over 20% mass reduction. [ABSTRACT FROM AUTHOR]

This work introduces the novel analysis of the bending behavior of a composite doubly curved panel made of graphene origami (GOri)-enabled auxetic metal metamaterials (GOEAMs) subjected to external mechanical force. The motivation for this study stems from the many applications of such structures in the field of aeronautics. These materials have mechanical and structural properties that continuously vary. This study is the first to examine the effects of an instantaneous external shock on the bending response of a composite doubly curved panel made of GOEAMs due to the extraordinary properties of these advanced materials. The mathematical governing equations are obtained from the higher-order shear deformation theory and are solved using the Laplace transform method (LTM) and the analytical solution procedure (ASP). After solving the equations, the results of the current system are compared to those of a previously published work, revealing a significant level of concurrence between the two sets of data. This study presents a machine learning approach that utilizes a deep neural network (DNN) with input, hidden, and output layers, as well as independent variables and other relevant factors. The aim is to provide an efficient computational technique for solving engineering issues. This is achieved by the use of mathematical modeling and the verification of the current output's outcomes. Additionally, a database is supplied for an in-depth examination of this structure's suitability for aeronautical purposes. The database contains comprehensive bending information, including normal, shear, and displacement fields in various directions, specifically for the GOEAMs subjected to external shock loading. [ABSTRACT FROM AUTHOR]

Proper consideration should be given to the stability of new concrete in order to assure the quality of building engineering, while also demanding its excellent flowability. The inadequate initial state stability negatively impacts the long-term durability of reinforced concrete structures, although this issue has not been well addressed. This work focuses on assessing the aerodynamic response of concrete ceilings reinforced with advanced functionally graded nano-materials. As the reinforcement of the current concrete structure, graphene oxide powders (GOPs) are used with improved material properties than other types of reinforcement. For mathematical modeling of the current structure, Reddy's Higher-order Shear Deformation Theory is used to model the current work's displacement fields. Also, the perturbation aerodynamic force is mathematically described using the Bernoulli equation for potential flow. After that using a method that involves separating variables, we may get the answer for the aerodynamic pressure in its ultimate form. Haber-Schaim foundation made of auxetic material in the Cartesian coordinate system is used to model the foundation of the current work with high accuracy. After obtaining the governing equations and associated boundary conditions, a meshless approach with weighted orthogonal basis and Kronecker delta-based shape functions are used to solve the equations. Finally, some suggestions for improving the aerodynamics and flutter velocity of airflow of the presented concrete plate reinforced by GOPs are presented for related aerodynamics industries. [ABSTRACT FROM AUTHOR]

For the first time, in the current work, the quasi-3D new refined theory (Q3D-NRT) is used to analyze the dynamic reactions of functionally graded (FG) annular sector plates made of graphene origami (GOri)-enabled auxetic metal metamaterials to the mechanical shock loading. The auxetic property of the annular plates is effectively controlled by graphene content and GOri folding degree that is graded across the thickness direction of the annular plates in a layer-wise manner, as Poisson's ratio and other material properties are position-dependent and can be estimated by genetic programming-assisted micromechanical models (MM). Hamilton's concept is used to find the structure's governing equations. The differential quadrature technique and the Laplace transform are used at design sites to solve the time-varying equations of motion. The system response is translated from the Laplace domain to the time domain using a modified version of the Dubner and Abate approach. To investigate the impact of different geometrical and physical factors on the dynamic reactions of the annular sector plates, thorough parametric research is conducted. The findings of the present mathematical modeling are compared with those of the earlier publications and also with those of the machine learning approach. Utilizing this learning strategy, differential equations may be solved with very cheap computer costs while also overcoming formulation complexity. It needs a valid dataset from experimental or numerical analysis to use machine learning techniques. This dataset was compiled using the study's numerical findings. Additionally, the machine learning approach demonstrates the capacity to deliver findings with a high degree of accuracy when predicting the mechanical characteristics of the existing structure under novel loading and boundary circumstances. [ABSTRACT FROM AUTHOR]

Split thickness skin grafting is one of the common skin transplantation techniques employed in treating severe burn injuries. Recent experimental studies have shown that the expansions offered by split thickness skin grafts are much lower than what is claimed by the graft manufacturers. To date, limited studies have investigated the effect of slit patterns on the expansions and the possibility of material innovation. This work has experimentally tested novel auxetic slit patterns on a biofidelic skin simulant to evaluate their effect on skin graft expansion. A wide range of variants of alternating slit (AS), I-shaped (IS), and Rotating Triangle (RT) based auxetic patterns were tested. A biaxial testing device was employed to simulate realistic skin stretching during graft implementation. The deformation, expansion, stress-strain response, void area, and maximum gap size were estimated, and the material behavior was also modeled using hyperelastic curve fit coefficients. The key design parameters were determined, which would produce high expansion with minimal voids. The findings of this study are anticipated to throw light on the possibility of using auxetic slit patterns for generating higher expansions in split thickness skin grafts. [ABSTRACT FROM AUTHOR]

Sandwich structures have been a subject of intense scrutiny and utilization in engineering applications. However, there has been a limited understanding of the mechanical behaviors of novel sandwich structures composed of auxetic metamaterials. This study aims to contribute to the body of knowledge by examining the buckling responses of sandwich beams or wide plates with an orthotropic anti-tetra chiral lattice (ATCL) aluminum cores and symmetric angle-ply carbon-fiber/epoxy face sheets, both of which can exhibit highly negative Poisson's ratios or extreme auxeticity. The linear stability analysis of the sandwich structures under axial compression is conducted by applying the minimum potential energy principle and solving the eigenvalue problem using a numerical method. To achieve an accurate representation of arbitrary two-dimensional buckling morphologies, the first- and fifth-order shear and normal deformation models are employed to simulate the transverse kinematics of the face sheets and cores, while the finite-element model is utilized to discretize the longitudinal displacement of all constituents. The investigation reveals new insights into the interrelationship between global buckling, facial wrinkling, and shear crimping in conventional sandwich structures. The effects of material auxeticity on buckling responses are analyzed across an extensive range of geometrical configurations for the first time, unveiling five unprecedented buckling mode shapes, sophisticated buckling mode landscapes, and Poisson's ratio-sensitive buckling criteria. These findings lay a crucial foundation for designing and optimizing auxetic sandwich structures, bringing diverse possibilities in lightweight constructions, acoustic insulation, energy absorption, and dynamic and shock mitigation. [ABSTRACT FROM AUTHOR]

Over the years, researchers have investigated active metamaterials because of controllability of their geometry and mechanical properties. However, despite the undeniable appeal and significance of this direction of studies from the perspective of many industries, researchers have struggled to systematically design such structures in an easily reproducible and scalable manner. Herein, it is shown that this can be achieved by harnessing the potential of foldable magnetomechanical metamaterials controlled via the external magnetic field. To this aim, two different configurations of the system with one of them being constrained so that it acts similarly to a linear actuator while the other one allows to fully control its expandability and mechanical properties in all directions are presented. Finally, the possibility of stacking the considered structures to create large systems that may exhibit auxetic properties in multiple planes will be discussed. The magnetomechanical metamaterials discussed are very interesting as they offer multidirectional and finely controlled movement which could be untethered. This is particularly promising for use in actuators, vibration dampers as well as scaffolds in deployable structures and impact resistive materials as the mechanical properties can be fine‐tuned by simply adjusting the external magnetic field and reconfiguring the structure. [ABSTRACT FROM AUTHOR]

This study addresses the main challenges in manufacturing large-scale metallic auxetic structures, characterised by a negative Poisson's ratio, focusing on achieving suitable geometry control, surface finish, and structural integrity using Wire Arc Additive Manufacturing (WAAM). Specifically, the research employs the Cold Metal Transfer (CMT) process to fabricate 2D and 3D carbon steel auxetic cells. The primary objective is to address the challenges associated with the production of these structures. A comprehensive experimental and numerical analysis was conducted to investigate the influence of various factors, such as internal defects or geometric irregularities, such as pores and surface waviness, on the mechanical behaviour of the 2D and 3D auxetic cells under tensile and compressive loads, respectively. The compression tests revealed that despite minor defects and geometric imperfections, the manufactured cells consistently exhibit a negative Poisson's ratio. This suggests that the WAAM-produced auxetic structures are viable and capable of maintaining their unique mechanical properties. Furthermore, the study emphasises the significance of parameters such as orientation and the number of auxetic cells in governing the overall auxetic behaviour of the components. [ABSTRACT FROM AUTHOR]

Additive manufacturing is widely used to fabricate metamaterials. The mechanical properties of these are tailored by modifying topological parameters to meet desired performance. Here, an auxetic metamaterial composed of arc-shape elements is presented. The directional dependency of the apparent stiffness was characterized through finite element analysis and tensile and compressive tests on additively manufactured samples with fused filament fabrication in thermoplastic polyurethane. Poisson's ratio was measured with computational vision. The effective Young's modulus resulted with a nonlinear relation to the wall thickness. The orientation sensibility exposed the relevance of rotational symmetry in a lattice architected metamaterial. [ABSTRACT FROM AUTHOR]

Metamaterials feature extraordinary physical properties that break the cognitive limitations of human beings on traditional materials. Auxetic materials and liquid crystal elastomers (LCEs) are representative of typical mechanical and thermal metamaterials. Their combination may introduce some unconventional and counterintuitive performances. Nevertheless, studies on LCEs with negative Poisson's ratio (v) are still rare. Herein, a liquid crystal vitrimer (Poly‐LCE) is developed that is a polydomain main‐chain LCE containing dynamic ester bonds. Its orientation process to monodomain (Mono‐LCE) is greatly simplified by transesterification reaction‐induced topological network rearrangement under mechanical alignment. By optimizing geometric parameters of re‐entrant (R) structures and orientation of liquid crystal units, all samples of R‐Poly‐LCE, R‐Mono‐LCE (//), and R‐Mono‐LCE (⊥) show negative Poisson's ratio (NPR) below 2% elongation (v = −0.22–0 for R‐Poly‐LCE, v = −0.12–0 for R‐Mono‐LCE (//) and v = −0.16–0 for R‐Mono‐LCE (⊥)). Interestingly, R‐Poly‐LCE presents v > 0 within 2%–10% axial elongation, while R‐Mono‐LCE (//) and R‐Mono‐LCE (⊥) exhibit v ≈ 0 under the same elongation. Materials with negative and zero Poisson's ratios are interesting in niche applications. This work develops a simple method to prepare these materials by liquid crystal vitrimers. [ABSTRACT FROM AUTHOR]

The significance of this paper is an investigation into the design, development, and optimization of a new polymeric hybrid auxetic structure by additive manufacturing (AM). This work will introduce an innovative class of polymeric hybrid auxetic structure by the integration of an arrow-head unit cell into a missing rib unit cell, which will be fabricated using fused filament fabrication (FFF) technique, that is, one subset of AM. The auxetic performance of the structure is validated through the measurement of its negative Poisson's ratio, confirming its potential for enhanced energy absorption. A chain of regression, linear, and quadratic polynomial machine learning algorithms are used to predict and optimize the energy absorption capability at variant processing conditions. Amongst them, the polynomial regression model stands out with an R-squared value of 92.46%, reflecting an excellent predictive capability for energy absorption of additively manufactured polymeric hybrid auxetic structure. The optimization technique revealed that the printing speed of 80 mm/s and layer height of 200 µm were the critical values to achieve a maximum amount of energy absorption at 5.954 kJ/m2, achieved at a printing temperature of 244.65 °C. Such results also contribute to the development of AM, since they show not only the potential for energy absorption of polymeric hybrid auxetic structures but also how effective machine learning is in the optimization of the AM process. [ABSTRACT FROM AUTHOR]

In the proposed study, the fatigue analysis of an axisymmetric chiral cellular structure and its modified form, made of stainless steel 316L, is carried out. The main goal of the original structure geometry was to absorb as much mechanical energy as possible with its auxetic behaviour. However, it was found through testing that its response could be improved by modifying the thickness of the struts through the structure. Representative models for the original and modified geometries were generated using a script adapted for this numerical simulation. Three different types of displacement in the shape of sine waves were used to load the structures. A hexagonal mesh was assigned and determined by convergence analysis. An existing material model with the necessary LCF parameters was assigned in the computational analyses. The data from multiple simulations were recorded and presented in graphs that showed how the fatigue life of the structures changed depending on the level of strain. We also analysed stresses and plastic deformations that occur in the structures. The results showed that, despite a better stress distribution, the fatigue life of the optimised structure was shorter in all cases. [ABSTRACT FROM AUTHOR]

This study explores the potential of periodic open cellular structures (POCS) that combine the auxetic and the shape memory effect (SME) with the aim of enhancing heat transfer in catalytic tubular reactors. On the one hand, these structures exhibit a negative Poisson's ratio, contracting perpendicular to the load axis under compression, driven by the rotation of nodes generating complex stress fields. On the other hand, the shape memory alloy (SMA) Nitinol (NiTi) with a reversible strain of up to 8% produced via electron beam powder bed fusion (PBF‐EB) shows extraordinary material properties with a high degree of freedom in structure design. The study conducts finite element method simulations and experiments to design POCS with tailored properties. Compression tests on less expensive Ti‐6Al‐4V POCS compared to NiTi POCS validate the simulative parameter study applied to fabricate novel auxetic hexagonal reentrant structures from NiTi with a unique stacking order and curved struts. The aim of this part of the study is to offer a pathway to design a NiTi auxetic POCS based on validated simulations. Further, it explains the interactions between geometrical parameters and mechanical properties of cellular reentrant NiTi structures. An optimized auxetic NiTi POCS achieved a Poisson's ratio of −1. [ABSTRACT FROM AUTHOR]