Unit Cell Configurations Research Articles

Fatigue characterization and life prediction of flexible lattice structures based on DLP processes

This study investigated the effects of cell configuration and relative density on the fatigue performance of truss-like lattice structures. Among the lattice structures examined, simple cube cells exhibited the highest fatigue strength across all relative densities. Numerical simulation results indicated that the S-N curves of the structures demonstrated pronounced power-law behavior as the volume fraction changed. The influence of various geometric factors on the power-law model parameters is discussed in detail. The power-law coefficient is influenced by the unit cell configuration and relative density; however, the power-law index is not affected by relative density and depends solely on the unit cell configuration. A fatigue life prediction model based on the Ashby-Gibson model was proposed. Finally, the reliability of the numerical simulation results was experimentally verified, with the predicted results of the model showing good agreement with the test data.

Click metamaterials: Fast acquisition of thermal conductivity and functionality diversities

In material science, the development of metamaterials is crucial for advancing various technological applications. However, most metamaterial designs are still case by case due to lacking a fundamental mechanism for achieving reconfigurable thermal conductivities, largely hindering design flexibility and functional diversity. Inspired by the principles of click chemistry, known for its modular and efficient approach to creating molecular diversity, here we propose a universal concept of click metamaterials for fast realizing various thermal conductivities and functionalities. Tunable hollow-filled unit cells are constructed as the modified building blocks to change the thermal conductivity locally. Different configurations of unit cells with variable fill fractions can generate convertible thermal conductivities from isotropy to anisotropy, allowing click metamaterials to exhibit environment-free and reconfigurable thermal functionalities. The straightforward structures enable full-parameter regulation and simplify engineering preparation, making click metamaterials a promising candidate for practical use in other diffusion and wave systems.

Characterization of rigid open-cell foams using direct ultrasonic simulation.

An ultrasonic simulation technique based on the direct fluid model is proposed as an alternative to the analogous experimental technique to determine the tortuosity and characteristic lengths for high pore-density foams. It is beneficial as it reduces cost and almost eliminates the signal-to-noise issues encountered in the experiment. The proposed method is demonstrated for periodic microlattices with three different unit-cell configurations, 75%-90% porosity, and a pore size of about 200 microns. The technique is also applicable to high-resolution computed tomography (CT) scans of open-cell foams with a priori unknown microporous structure. An acoustic simulation software, ACTRAN® (Hexagon AB, Stockholm, Sweden), is used to model and perform analysis of the ultrasonic pulse propagation through the foam. Based on through-transmission by foam saturated with two different mediums, the tortuosity, and characteristic lengths are estimated from the high-frequency asymptotic behavior of the square of the propagation index (Nr2) versus the inverse square root of frequency (1/f). The predicted parameters are validated by comparing them with those determined by solving the electric conduction boundary value problem for the same configuration. Further, detailed parametric sensitivity analysis reveals the sensitivity of the Johnson-Champoux-Allard parameters to errors in Nr2 and so the effect of these errors on the acoustic absorption behavior of the rigid porous sample.

Experimental and numerical investigation of PLA based different lattice topologies and unit cell configurations for additive manufacturing

Experimental and numerical investigation of PLA based different lattice topologies and unit cell configurations for additive manufacturing

Effects of the unit-cell size and arrangement on the compressive behaviors of lattice structures in powder bed fusion additive manufacturing

Lattice structures demonstrate a unique compressive behavior wherein the compressive strength increases and converges to a specific value as the number of unit-cell arrangements and overall dimensions of the lattice structure increase. In this study, the effects of the unit-cell size and cell arrangement on the compressive behavior of lattice structures were investigated to determine the convergence of compression characteristics at specific unit-cell configurations. Simple cubic lattice structures were designed and manufactured using powder bed fusion techniques. The lattice structures were characterized using universal testing machines. Experimental results revealed that the convergence of compressive strength was influenced by the size of the unit cell: the number of arrangements at which a specific compressive strength was reached increased as the unit-cell sizes decreased. Furthermore, specific convergence points were determined for different unit-cell sizes, providing valuable insights into the compressive strength behavior of lattice structures. This study emphasizes the significance of considering both unit-cell arrangements and overall dimensions when designing standard specimens for compression testing. Additionally, the methodology developed in this study can be applied to obtain an optimal configuration for desired strength characteristics.

Architecture Design of High‐Performance Piezoelectric Energy Harvester with 3D Metastructure Substrate

AbstractPiezoelectric energy harvesters (PEHs) have drawn considerable attention due to their unique ability to convert ambient mechanical energy to electrical energy. These devices are widely implemented in numerous applications such as wearable technology, structural health monitoring, and renewable energy systems. In this work, a novel approach that seamlessly integrates arbitrary metastructures into the substrate layer of cantilever beam‐based PEHs is presented. The corresponding performance of each PEH design is evaluated via an experimentally validated finite element model. This is the first systematic study to explore 3D metastructures with various unit cell configurations, unit cell numbers, and porosity levels. Compared with the existing PEH designs, implementation of a 3D auxetic metastructure with 85% porosity single unit cell design can demonstrate a substantial enhancement in output power, reaching 48.16 mW, and a high normalized power density (NPD) of 2.1131 µW mm−3 g−2 Hz−1. Results show that there are competing requirements for improving the performance of PEHs. On one hand, low metastructure stiffness is preferred to achieve high power output at low resonant frequency. On the other hand, metastructures designs with low stiffness may induce excessive distortion in the substrate layer, leading to mechanical energy loss. This deformation mechanism adversely affects the mechanical to electrical energy conversion efficiency. Detailed guidelines for designing and manufacturing high‐performance PEHs are discussed in this work.

The axially-loaded behaviours of Schwarz Primitive (SP)-based structures: An experimental and DEM study

This study delves into the axial responses of Schwarz Primitive (SP) structures. Emphasising on bearing capacity, force distribution, cracking phenomena, load-displacement curve and energy absorption. Discrete element method (DEM) is adopted to analyse the axial load-bearing behaviour and fracture mechanics of Main SP and Secondary SP structures under various unit cell configurations after validated by experimental tests. The results indicates that despite sharing the same 1/8th cell structure, the axially-loaded behaviours of the Main SP and Secondary SP structures are not identical, particularly in scenarios involving a large unit cell size and a small number of unit cells. The Main SP structures display an axial load-bearing behaviour that is largely unaffected by variations in the number of unit cells along the x and y axes, while Secondary SP structures show a more pronounced improvement in average strength and energy absorption capacity when the number of unit cells increases. Main SP structures offer superior axial load-bearing capabilities and energy absorption efficiency, which is a significant consideration for their application in scenarios demanding high structural integrity. This distinction underlines the importance of tailored design and selection of SP configurations based on specific engineering requirements.

CVT grown CuSe single crystals: Unveiling photodetection advancements and thermoelectric promise

Over the past few decades, transition metal chalcogenides garnered global recognition for their noteworthy contributions to the modeling and engineering of electronic, optoelectronic, and thermoelectric devices to improve overall device performance. In the current investigation, the first ever growth of CuSe single crystals is achieved utilizing the chemical vapor transport technique with iodine serving as a transporting medium. The ascertainment of the hexagonal unit cell configuration in the grown CuSe crystals with the P63/mmc space group is substantiated via powder X-ray diffraction examination. The micro-surface characteristics exhibited planar facets outlined by layer boundaries, signifying crystal development through a mechanism reliant on layer growth. The direct optical bandgap of 1⋅64 eV for CuSe single crystals is unveiled by optical reflectance spectrum, demonstrating its aptitude for incorporation into photodetectors. The Raman spectrum manifested a prominent peak at 259 cm−1, aligning to Ag1 vibrational mode. The exploration of temperature-induced fluctuations in the power factor and figure of merit unveiled a progressive increase with rising temperatures. The optimal ZT parameter for the CuSe single crystals attains 0⋅058 at 523 K. The thermogravimetric patterns of CuSe single crystals exhibited singular step decomposition, exemplified by an average weight reduction of 25⋅49 % across the temperature spectrum from ambient to 813 K. The current−voltage (I–V) features of the fabricated CuSe single crystal photodetector are assessed under biasing voltage set at 20 mV at ambient temperature. Under a bias voltage of 20 mV and a polychromatic light intensity of 50 mW/cm2, the achieved responsivity is 4335⋅57 μA/W and a detectivity of 135 × 106 Jones. The photoresponse and thermoelectric examination of CuSe crystals alludes to their potential utility in innovative applications on the horizon.

A micromechanical study on shear performance of unidirectional composites with randomly distributed fibers in the transverse cross‐section

AbstractThe properties of unidirectional (UD) composites has been investigated by analyzing their elastic and strength characteristics under shear loading. The UD fiber‐reinforced polymer (FRP) composites usually consist of fibers randomly dispersed throughout the cross‐section in the transverse direction which is generally not accounted for. A micromechanical model based on finite element analysis (FEA) approach is utilized here to examine these properties. The study begins by identifying micro scale unit cells or repetitive unit cells (RUCs) at the micro scale, as well as representative volume elements (RVEs). The distribution of fiber volume fraction (Vf) varies among various micro scale unit cells positioned in the transverse cross‐section. The elastic properties and strength are estimated by considering the properties of the matrix and fibers, and the configuration of micro scale unit cells, which feature a fiber arrangement which is categorized as hexagonal and varying Vf at different locations (from 0.35 to 0.75). However, the overall Vf for the UD composite remains constant at 0.65. Studies are also carried out with the random distribution of fibers at micro scale unit cells. The findings reveal that the random distribution of fibers significantly impacts the shear behavior of the composite. This investigation provides valuable insights into how the mechanical properties of the UD composite are subjective by the distribution of fiber, thereby contributing to the design and development of this light weight high‐performance material.Highlights Elastic and strength analysis of UD composites is presented. Emphasis is on fiber dispersion in transverse plane. Microscale unit cells, RUCs and RVE are identified. Studies are carried out based on micromechanical model. Influence of fiber distribution on shear behavior is investigated.

Buckling and free vibration of grid-stiffened composite conical panels using Extended Kantorovich Method

This paper develops very accurate closed-form solutions for buckling and free vibration of grid-stiffened composite conical panels using a semi-analytical method. On the base of first-order shear deformation theory (FSDT), the governing formulations are derived while an appropriate unit cell is used to derive the material properties of the lattice from their bulk properties. Multiple systems of ordinary differential equations (ODEs) are obtained by applying the Extended Kantorovich Method (EKM) to solve the governing system of partial differential equations (PDEs). The resulting ODEs are then solved using semi-analytical closed-form solutions to study buckling and free vibration of grid-stiffened panels. It is interesting to note that due to the general formulation of the conical panel, it is very easy to obtain other useful geometries including cylindrical panels, and even rectangular plates with general unit cell configurations. Regarding stability, fast convergence, and very low computing cost, the effectiveness of the proposed technique is investigated. The accuracy of the critical buckling loads and natural frequencies for various cases is studied which shows very good agreement in comparison with results obtained from the commercial finite element code ANSYS.

Theoretical insights into the electronic and optical properties of lithium-based perovskite for solar cell applications

This study explores the influence of central metals and halide anions on the structural, electronic, and optical properties of LiBX3 perovskites (B = Ge, Sn, Pb, X = F, Cl, Br, I) in both unit cell and supercell configurations, aiming for potential applications in photovoltaic devices. Density functional theory calculations reveal that increasing the atomic radius of halogens and central metals directly affects the lattice parameters. Our research indicates that Ge and Sn-based perovskites (except for unit cell LiSnF3) exhibit semiconductor properties with direct band gap energies, while Pb-based perovskites in the unit cell configuration display an indirect band gap. Key factors contributing to the reduction of the band gap energy in most materials include the expansion of the atomic radius of halogens and the examination of perovskites in their supercell state, such that perovskites like LiGeI3, LiSnI3, and LiPbI3 represent a band gap value of 0.001 eV in their supercell configuration. Furthermore, the light absorption characteristics of these perovskites demonstrate a high absorption coefficient ranging from 105 to 106. Among the studied compounds, I-based perovskites exhibit the highest static dielectric constant, surpassing other perovskite variants, with for example, unit cell and supercell of LiSnI3 having static dielectric constant values of 38 and 70, respectively. Additionally, the investigation of perovskites in their supercell form suggests that the number of atoms in the network does not significantly impact their optical properties. In conclusion, based on various analyses, I-based perovskites are proposed as ideal candidates for application in Photovoltaic Solar Cells (PSCs).

A novel metamaterial with instantaneously sign-switchable coefficient of thermal expansion and Poisson's ratio

Most materials expand when heated and contract when cooled. In contrast, negative thermal expansion materials exhibit the opposite behavior. In this paper, we present a metamaterial that expands both when heated and cooled. The unit cell configuration is crafted by embedding two isosceles triangular structures composed of high thermal expansion materials within a re-entrant hexagonal honeycomb framework. Initially, the bases of the two isosceles triangles are in contact. The metamaterial exhibits two deformation states under different external loads. Analytical formulas for the equivalent parameters were derived based on classical beam theory within the regime of small deformation. Finite element simulations were conducted to validate the accuracy of these analytical formulas. The influence of geometric parameters on the metamaterial is discussed in detail. The results demonstrate that the metamaterial can exhibit excellent multi-functional properties within a small range of deformation, including instantaneous sign-variable coefficients of thermal expansion and Poisson's ratios, along with significantly distinct tensile and compressive stiffnesses. This metamaterial consistently exhibits expansive characteristics regardless of variations in ambient temperature. Additionally, the material always expands laterally regardless of the sign of uniaxial loads. Based on these properties, the metamaterial can be applied to fasteners in the aerospace industry that require permanent locking, ensuring stability in various temperature and mechanical load conditions.

Hierarchical coiled phononic crystals: Reflectionless interfaces by duality

Duality has previously been demonstrated in twisted Kagome lattices, which are composed of a 2-D unit cell whose configuration can be transformed smoothly by varying a particular unit cell parameter. In the Kagome lattice, the twist angle defines the orientation of two triangular structures comprising the unit cell. In this case, duality expresses the fact that dispersion curves are identical for twist angles that are + /− δψ away from the self-dual configuration at ψ;c. The term self-dual refers to a certain unit cell configuration where dispersion curve families become degenerate, and thus, overlap. In this talk, a 1-D phononic crystal (PnC), composed of rotation-locked nodes linked by flexible bars modeled by continuum elements, is studied as a function of a twist angle. Interestingly, we demonstrate that a 1-D bar-based PnC also exhibits duality, when subjected to periodic rotation locking at the nodes. We show that particular segments of dual unit cells, having a + /− 90o difference in their wave propagation axes may be connected together without reflection and that this enables hierarchically coiled PnC (HCPnC), is contrasted with topologically protected metamaterials that also enable reflectionless wave propagation around a corner.

Coupling of Surface Plasmon Polaritons and Hyperbolic Phonon Polaritons on the Near-Field Radiative Heat Transfer Between Multilayer Graphene/hBN Structures

ABSTRACT Near-field radiative heat transfer (NFRHT) between multilayer graphene/hBN heterostructures has been demonstrated to exceed the blackbody limit due to the coupling mechanism of surface plasmon polaritons and hyperbolic phonon polaritons, opening the door to applications in thermal management, thermophotovoltaics, and nanoscale metrology. Recent studies have shown that adding vacuum layers within multilayer structures can effectively promote surface modes and thus enhance NFRHT. However, the influence of vacuum layers on NFRHT between multilayer graphene/hBN heterostructures has not been investigated. Moreover, the influence of vacuum layers on coupled resonance modes excited in multilayer structures is worth discussing. In this work, we study the NFRHT based on multilayer graphene/vacuum/hBN/vacuum structures. The results show that as the gap distance increases from 20 nm to 100 nm, the NFRHT of three-cell and six-cell configurations is enhanced, while that of unit-cell configuration is suppressed. The potential mechanism can be identified as the excitation of surface plasmon-phonon polaritons (SPPPs) and hyperbolic plasmon-phonon polaritons (HPPPs) in multilayer structures. The enhancement factor of the six-cell configurations is up to 4.82 when the gap distance is 80 nm. Moreover, the influences of the chemical potential of graphene and the layer thickness on the NFRHT are discussed. The interesting results in this work indicate the perspectives for future near-field research involving coupling of SPPPs and HPPPs, and shed new light on high-performance devices introducing vacuum layers based on near-field radiative heat transfer.

Topology optimisation for vibration bandgaps of periodic composite plates using the modified couple stress continuum

We propose a topology optimisation approach that can effectively account for the size effect of periodic composite plates to determine the optimal material distribution for achieving the largest bandgap width. The approach is based on the modified couple stress continuum and uses the relative bandgap width as the objective function, with volume constraints defined as the constraint function. The material properties are represented by the solid isotropic material with penalisation (SIMP) interpolation model, and the optimality criteria (OC) algorithm is employed to update the design variables. To address the significant size effect of the microplate structure, we use the modified couple stress continuum to model the dynamic behaviour of the unit cell. The Melosh–Zienkiewicz–Cheung (MZC) finite element is employed to ensure nodal C 1 continuity and achieve high-order elasticity with respect to inter-element continuity. Our results demonstrate that the proposed topology optimisation methodology is capable of effectively designing optimal unit cell configurations that account for size effect and significantly improve the bandgap width. We also investigate the impact of thickness and volume limitations on the optimised unit cell configuration. The obtained results suggest that the proposed topology optimisation framework is a promising approach for designing unit cell geometries with the account for size effect.

A Ku/K band dual linearly polarized Reflectarray for earth exploration satellite services

ABSTRACT A novel single-layer dual-band, dual-polarised reflectarray was designed, developed, and tested in this paper. This Reflectarray is a vital component to use, in Earth exploration sensor systems and remote sensing satellites for measuring water levels and cryosphere research. The proposed antenna is employed in dual frequency bands from 12.5–16 GHz to 23.5–26 GHz covering Ku/K bands. The corrugated semi-circular rings enclosed with quad delay line structures attached to the outer ring constitute the Ku band unit cell with periodicity (0.55 λ 0 ) resonating at 14.5 GHz. The K band unit cell with periodicity (0.78 λ 0 ) is constructed similarly to the Ku band unit cell but with a horizontal slot that provides vertical polarisation and resonates at 24.5 GHz. This integrated unit cell configuration results in dual linear, reduced cross-polarisation and allows independent phase optimisation at each frequency band. Phase variation of 770° and 811° at the operating frequencies of 14.5 GHz and 24.5 GHz is achieved by varying the element sizes. A centre-fed RA constructed on a square aperture (12.34 λ 0 ) comprising 23 × 23 elements for each frequency band gives the measured results of 1 dB bandwidth of 24% and 10.2% and peak gain of 28.2 dB and 27.6 dB at Ku/K bands, respectively.

Design and Fabrication of Flexible Woodpile Structured Nanocomposite for Microwave Absorption Using Material Extrusion Additive Technique

The explosive growth of electronics and the widespread use of transient power sources have given rise to an undesirable and uncontrolled consequence of electromagnetic interference (EMI). It is crucial to address and mitigate the issues caused by EMI by developing effective shielding techniques. The material extrusion additive technique provides a solution through its versatile 3D printing of polymeric ink, offering advantages such as design flexibility, structural complexity, and environmental sustainability. The primary objective of this study is to investigate the rheological properties, electromagnetic properties, and thermal stability of nanocomposites consisting of Polydimethylsiloxane (PDMS) and Multi-Walled Carbon Nanotubes (CNTs). The aim is to utilize these findings for the design and 3D printing of a microwave absorber with high efficiency. Composite inks containing 50 vol% (C50) and 60 vol% (C60) of CNTs exhibit favorable shear-thinning behavior and shape retention. On the other hand, lower CNT percentages result in inconsistent viscosity, rendering the inks non-printable. Thermogravimetry analysis reveals that an increase in CNT vol% leads to a decrease in the thermal stability of 3D-printed PDMS-CNT nanocomposites. Higher CNT proportion enhances electric polarization, and attenuation capacity, as evidenced by measurements of complex permittivity and dielectric loss tangent. X-Ray Diffraction analysis was employed to examine the effect of CNT inclusion in the composites. A woodpile-structured metamaterial microwave absorber based on gradient index (GWMMA) was designed by manipulating geometric parameters and CNT vol%. Fifteen unit cell configurations were generated and subsequently chosen based on their exceptional attenuation capabilities, low impedance, and narrower filament width for simulations. The GWMMA demonstrates exceptional absorption performance, surpassing reflection loss values of −10dB. Incorporating a third filament stacking into the woodpile structure augments its efficacy, yet further additions of stackings result in diminishing returns. Experimental validation of a selected 3D-printed GWMMA structure of C60 with a width of 0.75 mm confirms its absorption capabilities, closely aligning with the simulated results. The GWMMA exhibits promising performance for microwave absorption, with absorption values exceeding 90%. Simulations indicate the adjustability of the GWMMA's bandwidth and absorption capabilities through alterations in array periodicity and cell size. Its spatial scale aligns with sub-wavelength structures, establishing it as a representative Metamaterial Absorber (MMA).

Experimental and numerical investigation to elucidate the fluid flow through packed beds with structured particle packings

The present paper presents an experimental and numerical investigation of the dispersion of the gaseous jet flow and co-flow for the simple unit cell (SUC) and body-centred cubic (BCC) configuration of particles in packed beds. The experimental setup is built in such a way that suitable and simplified boundary conditions are imposed for the corresponding numerical framework, so the simulations can be done under very similar conditions as the experiments. Accordingly, a porous plate is used for the co-flow to achieve the uniform velocity and the fully developed flow is ensured for the jet flow. The SUC and BCC particle beds consist of 3D-printed spheres, and the non-isotropy near the walls is mostly eliminated by placing half-spheres at the channel walls. The flow velocities are analysed directly at the exit of the particle bed for both beds over 36 pores for the SUC configuration and 60 pores for the BCC configuration, for particle Reynolds numbers of 200, 300, and 400. Stereo particle image velocimetry is experimentally arranged in such a way that the velocities over the entire region at the exit of the packed bed are obtained instantaneously. The numerical method consists of a state-of-the-art immersed boundary method with adaptive mesh refinement. The paper presents the pore jet structure and velocity field exiting from each pore for the SUC and BCC packed particle beds. The numerical and experimental studies show a good agreement for the SUC configuration for all flow velocities. For the BCC configuration, some differences can be observed in the pore jet flow structure between the simulations and the experiments, but the general flow velocity distribution shows a good overall agreement. The axial velocity is generally higher for the pores located near the centre of the packed bed than for the pores near the wall. In addition, the axial velocities are observed to increase near the peripheral pores of the packed bed. This behaviour is predominant for the BCC configuration as compared to the SUC configuration. The velocities near the peripheral pores can become even higher than those at the central pores for the BCC configuration. It is shown that both the experiments as well as the simulations can be used to study the complex fluid structures inside a packed bed reactor.

Compression property and energy absorption capacity of 4D-printed deformable honeycomb structure

Honeycomb structures exhibit outstanding mechanical properties with specific unit cell configurations. We introduce a novel honeycomb structure that can enhance the compression property and energy absorption capacity by utilizing four-dimensional (4D) printing technology with polylactic acid (PLA) materials. In the designed honeycomb structure, the walls of the adjacent unit cells are independent, and the shape of the unit cells can be transformed between a hexagon and triangle under external loading and temperature stimulus. 4D printing technology is employed to prepare the honeycomb specimens, and the deformation processes of the innovative honeycombs are implemented. Structure I (a novel hexagonal honeycomb structure) and Structure II (a semi-triangular honeycomb structure) can be transformed into each other. Uniaxial quasi-static compression and impact tests are conducted to investigate the compression property and energy absorption capacity of the designed honeycomb structures. The results indicate that the novel honeycomb had a high compression property with Structure II, and had high energy absorption capacity with Structure I; thus, the developed honeycomb structures have broad application prospects for the multifunctional applications of honeycomb structures in the future.

Compressive and tensile behaviours of 3D hybrid auxetic-honeycomb lattice structures

Lattice structures have the potential for application in tensile conditions. However, limited studies have addressed tensile behaviours of such structures and compared them with their compressive behaviours. In this paper, re-entrant structure as the foundation was selected to develop new 3D hybrid auxetic honeycomb lattice structures, each characterized by a unique unit cell configuration that features interconnected centre auxetic honeycomb, differentiating it from 2D hybrid auxetic honeycomb structures. A series of uniaxial quasi-static tensile and compressive tests, followed by simulations were conducted on these structures to investigate and compare their energy absorption characteristics. The results show that there were significant differences between these structures in terms of their mechanical behaviours under tension and compression. Especially, the smallest value of energy absorption under tensile load was 86% higher than the largest value under compressive load. The stiffnesses of these lattice structures under tensile loading were about 84–122 times of those of the identical corresponding structures when they were compressed. Meanwhile, the progressive stretching, buckling and collapse mechanisms observed in these structures exhibited excellent stiffnesses and energy absorptions under tensile and compressive load compared to traditional 3D auxetic as the basic structure. The outer frame structure of lattice structures had a direct influence on Poisson's ratio. The work indicates that the stiffness and energy absorption of the traditional 3D auxetic structure can be enhanced by embedding auxetic and honeycomb umbrella shaped elements.