Re-entrant Angles Research Articles

Design, fabrication and mechanical properties of a 3D re-entrant metastructure

A 3D re-entrant honeycomb structure was designed in a simple configuration by introducing a spatial angular design parameter. Mechanical responses under uniaxial compression of it at constant spatial angle (α) and different re-entrant angles (θ) were investigated both experimentally and theoretically. Designed lattice auxetic structures with high shape fidelity were fabricated using selective laser sintering (SLS) of PA 2200 powder. The produced samples exhibited negative, zero, and positive Poisson's ratios depending on a selected θ value, and their mechanical properties varied over a wide range. Bend- and buckling-dominated deformation mechanisms of the struts have been observed under compression. Additionally, the analytical models of re-entrant honeycomb structures effectively illustrated the quantitative relationships between their mechanical properties (Young’s modulus (E) and Poisson’s ratio) and the design parameter θ. The results presented in this study would provide a reference to the customized design of the porous auxetic structures with unique mechanical properties.

Capability of auxetic femoral stems to reduce stress shielding after total hip arthroplasty.

Stress shielding​(SS) is considered the main mechanical cause of femoral stem loosening after total hip arthroplasty (THA). This study introduces an auxetic lattice femoral stem structure with negative Poisson's ratio that can expand laterally, with the intent of transferring more load to surrounding bone and thereby reducing SS. This study aims to evaluate how the geometry profile of different femoral stems with auxetic structures affects the level of SS. Different re-entrant angles for the auxetic unit cells were also evaluated. This study assessed three commercial femoral stem designs (Mayo, CLS and Fitmore) and three re-entrant angles for the auxetic structures (60°, 70° and 80°). Nine auxetic femoral stems (three M-type, three C-type and three F-type) and three solid femoral stems (control group) were designed. All femoral stems were implanted into a finite element model of the human femur to compare levels of SS between the auxetic stems and their traditional solid counterparts. The results showed that incorporating an auxetic structure into the stem design caused less SS of the surrounding bone than the control models. The M-type stems had the lowest level of SS, followed by the C-type and F-type stems. A re-entrant angle of 70° for the M-type stem, 80° for the C-type stem and 60° for the F-type stem were the designs most capable of reducing SS. This study found that femoral stems with an auxetic lattice structure caused less SS after THA than comparable solid femoral stems. A femoral stem based on the M-type geometry profile is recommended when designing auxetic femoral stems to minimize SS of surrounding bone. The novel solution provided in this study may serve to increase the survival rate of femoral stems by reducing SS after THA.

Adaptive FEM for Helmholtz Equation with Large Wavenumber

A posteriori upper and lower bounds are derived for the linear finite element method (FEM) for the Helmholtz equation with large wavenumber. It is proved rigorously that the standard residual type error estimator seriously underestimates the true error of the FE solution for the mesh size h in the preasymptotic regime, which is first observed by Babuška et al. (Int J Numer Methods Eng 40:3443–3462, 1997) for a one dimensional problem. By establishing an equivalence relationship between the error estimators for the FE solution and the corresponding elliptic projection of the exact solution, an adaptive algorithm is proposed and its convergence and quasi-optimality are proved under the condition that \(k^3h_0^{1+\alpha }\) is sufficiently small, where k is the wavenumber, \(h_0\) is the initial mesh size, and \(\frac{1}{2}<\alpha \le 1\) is a regularity constant depending on the maximum reentrant angle of the domain. Numerical tests are given to verify the theoretical findings and to show that the adaptive continuous interior penalty finite element method (CIP-FEM) with appropriately selected penalty parameters can greatly reduce the pollution error and hence the residual type error estimator for this CIP-FEM is reliable and efficient even in the preasymptotic regime.

Relationship of Building Form with Damage Pattern and Damage Level

The level of damage to the building is influenced by the configuration of the building plan with the angle of re-entrant and the pattern of damage. Architects need to know and understand the pattern of building damage and the configuration of hospital plans with an architectural approach. A certain level of damage has an impact on the safety of the lives of patients and health workers. The method used is a quantitative method with 2 steps, namely literature study and correspondence. The technique used is a visual identification technique from photographs in 28 earthquake-related journals with 108 cases. There is a significant relationship between the shape of the re-entrant angled building and the level of damage caused by the earthquake. The configuration of the building plan with re-entrant angles U and L is closely related to the level of heavy structural damage (level 4). The pattern of structural damage in the configuration of the re-entrant corner plan U, L, H occurs in the re-entrant corner and the outside of the building. The hospital as a vital building must use a floor plan configuration without a re-entrant angle.

Numerical and theoretical analysis of crushing strength of 3D re-entrant honeycomb

Auxetic structures with negative Poisson’s ratio (NPR) have been widely studied because of their great potentials in energy absorption. In order to further understand the 3D auxetic structures, especially the 3D re-entrant honeycombs, the crushing response of metallic 3D re-entrant honeycomb (3D-RH) is theoretically studied in this paper. First, the finite element (FE) model of the 3D-RH was built and validated. The numerical simulation results show that the 3D-RH exhibits different deformation modes under low- and high-speed crushing. Secondly, a set of numerical simulations was used to determine the critical velocity that distinguishes the two deformation modes. Based on the predicted deformation profile, the crushing strength of 3D-RH under low- and high-speed crushing was derived in the form of theoretical equations. The relative errors between the theoretical and numerical results are less than 10%. Thirdly, the structural parameters were studied to reveal their effects on the crushing strength of 3D-RH. The results showed that the oblique wall length and cell wall thickness have significant effects on the crushing strength, while the cross length and cell wall width have little effect on the crushing strength. In addition, the re-entrant angle has no obvious effect on the low-speed crushing strength, but has a significant effect on the high-speed crushing strength. Finally, considering the rotational symmetry of the 3D-RH unit, the 3D-RH-nRP unit was found, which is a new type of 3D re-entrant unit with multiple re-entrant parts. The corresponding equations of crushing strength were derived. The FE results showed that the equations can well estimate the crushing strength of 3D-RH-nRP structures.

Evidence of late root formation of molars in Anderson’s red-backed vole, Eothenomys andersoni (Thomas, 1905) (Cricetidae, Rodentia), and arguments for its generic allocation

We evaluated the molars in Anderson's red-backed vole (n = 114) from the Kii Peninsula of Honshu, Japan. Two of the specimens are considered extremely old aged based on their dimensions and on the loss of alveolar capsules of M2, and a third one is also old based on its strongly worn left M3 and M1. Of the former two individuals, one showed an incipient closure of re-entrant angles at its basal end, as estimated from the difference between the occlusal patterns of the occlusal and basal surfaces of the left M2. The latter individual also showed a complete closure of the basal end in the left M3. These patterns differ from incipient roots observed in other vole taxa but were similar to a previous example of incipient roots in Anderson's red-backed vole. Therefore, we suggest that molar roots in this species form at an extremely late age or by strong wear. Root formation in molars is considered an important diagnostic character, as Eothenomys molars lack roots, while Craseomys molars develop roots at a late age. However, this dental character may be particularly difficult to assess in voles under natural conditions. Considering previous phylogenetic findings based on molecular analyses, Craseomys is the most appropriate genus for Anderson's and other Asiatic red-backed voles.

Strength enhancement and modulus modulation in auxetic meta-biomaterials produced by selective laser melting

Meta-biomaterials are applied to orthopedic implants to avoid stress shielding effects; however, there is no reason for the yield strength to be comparable to that of human bone. In this study, a composite unit cell was designed by combining the positive Poisson's ratio (PPR) and negative Poisson's ratio (NPR) unit cells, inspired by the second-phase strengthening theory. The purpose was to increase the strength while maintaining the elastic modulus. All structures were successfully fabricated from Ti-6Al-4V via selective laser melting. The relative density is between 0.08 and 0.24, which falls within the optimal range for bone growth. Mechanical tests indicated that the center of the inclined rod fractured in a stepwise fracture mode, which was consistent with the predictions of the Johnson–Cook model. The elastic modulus ranged from 0.652 ± 0.016 to 5.172 ± 0.021 GPa, and the yield strength varied from 10.62 ± 0.112 to 87.158 ± 2.215 MPa. An improved Gibson–Ashby law was proposed to facilitate the design of gradient structures. When the re-entrant angle was 40°, a hybrid body-centered cubic NPR structure was formed, resulting in a significant improvement in the mechanical properties. Importantly, the yield strength of the proposed composite structures increased by 43.23%, and the compression strength increased by 44.70% under the same elastic modulus. The strengthening mechanism has been proven to apply to other bending-dominated structures. Overall, this imparts unprecedented mechanical performance to auxetic meta-biomaterials and provides insights into improving the reported porous structures. Statement of significanceAuxetic meta-biomaterials exhibit auxetic properties that can improve the contact between the bone-implant interface and reduce the risk of aseptic failure. To avoid the stress shielding effect, the elastic modulus has traditionally been decreased by increasing the porosity. However, the strength is simultaneously reduced. Therefore, a composite unit cell was proposed to increase strength rather than modulus by combining the positive and negative Poisson's ratio unit cells, inspired by the second-phase strengthening theory. We observed a 43.23% increase in the yield strength of the composite structure without increasing the elastic modulus. This strengthening mechanism has been proven to apply to other bending-dominated structures. Our approach provides insights into improving other bending-dominated structures and broadening their applications for bone implantation.

The wetting transition of low surface tension droplet on the special-shaped microstructure surface

The hydrophobic surfaces have been widely used in many field due to their excellent properties. However, the droplet with low surface tension can easily undergo wetting transition and highly infiltrate on a surface with conventional structure, so it is difficult to achieve the hydrophobic state. Preliminary bionics studies showed that the microstructure surface with a reentrant angle could suspend the droplet with low surface tension to achieve the hydrophobic property. But, the wetting mechanism of droplet on the reentrant microstructure surface was not clear. The wettability of the droplet on the reentrant microstructure surface was studied with the numerical method of VOF-CSF in this paper. It was found that the reentrant structure could effectively inhibit the occurrence of wetting transition compared with the conventional columnar-shaped structure, so that the hydrophilic droplet remained suspended and showed a large apparent contact angle. The mechanical model and the relative surface free energy of the droplet in the wetting process on the reentrant microstructure surface were analyzed theoretically. It was found that the geometrical parameters of reentrant structure affected the breakthrough pressure and energy barrier, and then affected the wetting transition. The results showed that the performance of doubly-reentrant structure was better than that of singly-reentrant structure in inhibiting wetting transition. For the reentrant structure with larger width and smaller spacing, the advantage of inhibiting wetting transition was more obvious, and the effect of width gradually disappeared with the increase of spacing. For the droplet that has been suspended on the reentrant structure surface, a slight change of structure width will greatly affect the stability of the small droplet.

A Novel Re-Entrant-Type Metamaterial with Tunable Negative Poisson’s Ratios and Coefficients of Thermal Expansion

Introducing bi-material double-triangular elements into a standard re-entrant structure, a novel metamaterial is proposed in this work. The effect of geometrical parameters on negative Poisson’s ratio (NPR) and coefficient of thermal expansion (CTE) is studied theoretically and verified by finite element (FE) method. Results show that the proposed structure provides tunable Poisson’s ratios in wide ranges (from negative to positive) by adopting base materials with different elastic moduli. The horizontal Poisson’s ratio of the structure increases with the increment of the re-entrant angle, and decreases with the decrement of the elastic modulus ratio (i.e., the ratio of the elastic modulus of MAT-1 and MAT-2); while the vertical Poisson’s ratio decreases with the increment of the re-entrant angle, but is independent on the elastic modulus ratio. Moreover, comparing with various reported re-entrant structures, the proposed design enhances elastic modulus significantly owing to the introduced bi-material triangles. The structure also exhibits tailorable CTEs. The CTE of the structure decreases with the increment of the CTE ratios and the re-entrant angle.

A numerical approach for solving one nonlinear problem of hydrodynamics in a non-convex polygonal domain

The paper considers the two-dimensional stationary problem obtained as a result of time discretization of the nonlinear Navier-Stokes equations in rotation form, which describe the incompressible viscous fluid flow in a non-convex polygonal domain. In order to solve a nonlinear problem, it is necessary to find solutions to a sequence of approximate linear problems. For linear problems, the concept of an Rv-generalized solution in weighted sets obeying the weighted analogue of the Ladyzhenskaya-Babuška-Brezzi condition is introduced. A scheme of the weighted finite element method is constructed which suppresses the error arising in the neighborhood of the vertex of the reentrant angle and does not allow it to propagate into the inner part of the computational domain. The mass conservation law is valid directly at the grid nodes, and not only in the (weak) integral sense. Numerical experiments are carried out and a comparative analysis is made in polygonal domains with different values of reentrant angles. The advantage of the proposed approach over the classical finite element method is the order of convergence with respect to the grid step. A set of optimal parameters of the method is determined to obtain the required order of convergence. In this case, the exponent of the weight function depends on the value of the reentrant angle, and the parameters determining the Rv-generalized solution are independent on its value. In contrast to the classical approach, the order of convergence of the proposed approximate method to the exact solution of a nonlinear problem does not depend on the value of the reentrant angle. The constructed approximate method can be used without geometric mesh refinement in the vicinity of the singularity point.

Design 3D improved star-shaped honeycomb with different tip angles from 2D analytical star-shaped model

Two-dimensional star-shaped honeycombs (2D SSHs) exhibit an effective negative Poisson's ratio due to the abundant internal space and re-entrant angle, while the strength and the deformation of the three-dimensional (3D) SSHs are still limited owing to the finite tuneability of the tip angle. By adding different tip re-entrant angles into the SSH, multiple improved star-shaped honeycombs (ISSHs) with tunable Poisson's ratio are proposed. The in-plane elastic properties, including the effective Young's moduli and effective Poisson's ratio, are both derived by 2D analytical model using the energy method. The finite element simulation and compression experiment are used to verify the correctness of theoretical results. Based on the work, the deformation mechanism of the 3D ISSHs is discussed by quasi-static compression experiment and numerical simulation. The simulation results and experimental results show a great agreement with theoretical results. Different tip angles heighten the normalized Young's modulus and make the Poisson's ratio more tunable, respectively. In addition, the 3D ISSHs show an enhanced effect among higher strength and stability while bearing the compression load. This work provides a good reference for constructing 3D symmetrical multicellular structures, especially honeycombs.

An investigation of optimal auxetic cores in sandwich structures to withstand low-velocity impact loading

One of the main issues in designing sandwich structures is selecting an appropriate core with optimal dimensions for the application. This study investigated the impact response of auxetic cores with re-entrant structures when subjected to low-velocity impact (LVI) loading. To this end, an analytical model was developed using high-order nonlinear theory, and the corresponding equations were extracted by applying the Ritz method and subsequently solved using the Runge–Kutta method. The analytical model was developed by replacing the porous auxetic core with an equivalent orthotropic solid layer. The numerical simulation demonstrated that the substituted layer exhibited behaviour similar to that of the original auxetic core. The validation of the analytical and numerical models was performed by fabricating several samples using fused deposition modelling (FDM); then, LVI tests were performed on the samples using a drop-weight apparatus. The comparison of the experimental and analytical results indicated that the proposed nonlinear model accurately predicted the behaviour of the auxetic core when subjected to LVI loading. The effects of the different geometric features – including re-entrant angle, strut thickness, core thickness, and impactor energy – were also examined in the parametric study in an effort to gain an enhanced understanding of the behaviour of the auxetic core.

Behavior of axially loaded L-shaped RC columns strengthened using steel jacketing

Other than rectangular and circular columns, the most commonly used sections in reinforced concrete (RC) buildings in Saudi Arabia are L-shaped columns with a re-entrant angle of 90° or more. The structural designers are using L-shaped columns to meet the architectural and functional constraints of the building without obstructing the movement. Strengthening of such L-shaped RC columns is required to increase their load capacity for a number of reasons, such as an increase in the number of stories, the change of building use, design error(s), or construction defect(s). This research studied experimentally and analytically the behavior of strengthened L-shaped RC columns. The test matrix comprised two groups of six half-scale L-shaped RC columns. In the first and second groups, respectively, columns had 90° and 135° re-entrant corners. Each group had three columns: one unstrengthened control specimen used as a baseline for comparison and two steel-jacketed columns. In the first strengthened specimen, there was a 25 mm gap at the interface of the steel jacket with the ends (bottom base and top box), whereas, in the second specimen, the jacket was connected with the ends. The column specimens were concentrically loaded in compression until failure. It is demonstrated that strengthening of L-shaped columns with disconnected steel jackets had limited improvement in the axial load capacity ranging from 26% to 29% over the unstrengthened ones, while upgrading the columns with connected steel jackets had major enhancement in the axial load capacity varying from 68% to 79% over the control specimens. Furthermore, an analytical model that considers concrete confinement and axial load contributed by connected steel jacket was developed for assessing the axial capacity of tested specimens. Good agreement was achieved between the experimental and analytical peak loads with errors in prediction ranging from 1% to 6%.

Three-dimensional composites with nearly isotropic negative Poisson's ratio by random inclusions: Experiments and finite element simulation

Composites with negative Poisson's Ratio (NPR), also known as auxetic composites, are of great interests due to excellent properties. Auxetic composites of various types have been developed, however most of them have anisotropic NPR behaviour. This paper reports a new type of three-dimensional (3D) composites with nearly isotropic NPR by randomly embedding rigid re-entrant equilateral triangle inclusions into soft matrix. Four types of inclusions with different structural parameters including re-entrant angle, prism length and rib thickness were first made from two types of carbon fibre prepregs, and then embedded into silicone rubber matrix with different inclusion numbers to fabricate 3D composites with various volume fractions of inclusions. Both experimental and finite element analyses were conducted to investigate the deformation behaviours under compression and the effects of different structural parameters and materials. The results show that the NPR of the composites can be realised with suitable structural parameters and properties. The lowest NPR of −0.19 was obtained via embedding 6 mm length inclusions made of one-layer 3K twill weave carbon fibre prepreg with an inclusion number of 800. The study provides a new approach for the development of 3D composites with isotropic NPR for the practical applications of auxetic materials.

Design and modeling of a novel three dimensional auxetic reentrant honeycomb structure for energy absorption

Aiming at achieving excellent energy absorption capacity, a novel periodic auxetic reentrant honeycomb structure is proposed by defining an octagon honeycomb unit cell with various shape parameters and reentrant angles. Additive manufacturing is applied to fabricate three groups of resin samples with different design parameters. Quasi-static compression experimental test is conducted obtaining the effects of negative Poisson’s ratio (NPR) on the compressive stress–strain relationship of the proposed structure. The results show the excellent lateral material shrinkage under axial compression and distinct hardening process with sharp stiffness increase when the structure experiences densification. The experiment results are then used to validate the corresponding 3D finite element models. Good agreements are found between the experiment and finite element simulation results. Furthermore, a geometry parameter study is used to analyze the effect of design parameters on energy absorption capacity of the structure and the results can be a good reference for future optimal design of similar meta-materials. To summarize, in addition to the good energy absorption capacity, thanks to the obvious NPR effects and lateral shrinkage behavior, the newly proposed honeycomb meta-material with specific auxetic reentrant design becomes a solid material with low porosity and high stiffness after full compression to provide further protection or support for its neighbor objectives.

A method for regulating negative Poisson's ratio by a reentrant anti-tetrachiral structure

Auxetic structures with negative Poisson's ratio (NPR) have been drawing an increasing attention due to the distinctive mechanical performance, i.e. expanding laterally when stretched axially or contracting when compressed. And the mechanical characteristic can be tailorable, which has vast prospects in large deformation structures. In this study, a novel auxetic structure, named reentrant anti-tetrachiral (RATC) structure, is designed by introducing a reentrant angle into the existing anti-chiral structure. The present structure can exhibit a significant improvement of NPR. In order to facilitate numerical analysis, ABAQUS and Python script are utilized to generate numerical models with different configurations automatically. Then effects of geometrical parameters on the elastic modulus, shear modulus, Poisson's ratio and relative area (the ratio between base material area and unit cell area) are numerically investigated. The simulation results show that the structural parameters have great influence on the mechanical performance. Finally, additive manufacturing technique is employed to fabricate samples of the proposed design, which are subjected to uniaxial quasi-static tensile tests and three-point bending tests. The mechanical characteristics are verified through both simulation and experiments. Overall, the improved mechanical performance of RATC is demonstrated, which provides guidelines for auxetic structure designs.

Impact Testing of 3D Re-Entrant Honeycomb Polyamide Structure Using Split Hopkinson Pressure Bar

In this study, a total of 30 3D re-entrant honeycomb specimens made of polyamide were fabricated with various configurations by using the additive manufacturing (AM) technique. Split Hopkinson Pressure Bar (SHPB) tests were conducted on the RH specimens at different impact velocities. The incident, reflected and transmitted waveforms can well explain the wave propagation and energy absorption characteristics of the specimens, which can help us to understand and analyse the process of impact loading. The stress–strain curves, energy absorption ability and failure modes of SHPB tests with different impact velocities and quasi-static compression tests were analysed and compared, and it was found that the flow stress and energy absorption ability of the specimens subjected to impact load were much improved. Among the tested specimens, specimen C2, with a smaller re-entrant angle θ, displayed the best energy absorption ability, which was 1.701 J/cm3 at the impact velocity of 22 m/s and was 5.1 times that in the quasi-static test. Specimen C5 had the longest horizontal length of the diagonal bar L0, and its energy absorption was 1.222 J/cm3 at the impact velocity of 22 m/s and was 15.7 times that in the quasi-static test, reflecting the superiority of a structurally stable specimen in energy absorption under impact loading. The test results can provide a reference for the optimization of the design of the same or similar structures.

On the wave propagation properties and Poisson’s ratio of the Star-3/6 structures

In this study, wave propagation characteristics of the Star-3/6 structures are studied, and the effects of geometric parameters on the wave propagation are analyzed. Especially, Poisson’s ratio is studied based on the long wavelength approximation of band structure. The Star-3/6 structures are assembled to be hexagonal and triangular topologies with re-entrant angles. By using the finite element method and Bloch's theorem, the dynamic models of the Star-3/6 structures are established, and the elastic wave behaviors are calculated. The effects of geometric parameters on distribution of band gaps are studied in detail. By applying the long wavelength approximation of band structure, the Poisson's ratio of the macrostructure is predicted, which is also obtained by the commercial finite element software for the comparisons. This paper confirms that the Star-3/6 structures have a positive Poisson's ratio rather than the visual negative Poisson's ratio. Additionally, the isotropic features of the Star-3/6 structures are evaluated by the group velocity. The Star-3/6 structures show effective isotropic features in the low frequency range. As the frequency of elastic waves increases, the propagation speed of elastic waves decreases, and the wave propagation gradually becomes anisotropic.

Biomechanical design and analysis of auxetic pedicle screw to resist loosening

BackgroundPedicle screws are widely used in fusion surgery, while screw loosening often occurrs. An auxetic structures based pedicle screw was proposed to improve the bone–screw fixation by radial expansion of the screw body under tensile force to resist pulling out. It was optimized to obtain excellent anti-pullout ability for a particular bone based on the biomechanical interaction between screw and surrounding bone. MethodsThe screw was designed based on re-entrant unit cells. The mechanical properties of it were adjusted by the wall thickness (t) and re-entrant angle (θ) of the unit cell, and characterized using finite element (FE) method. The designed screws were manufactured using 3D-printing, and Ti6Al4V as the materials. Subsequently, the pullout FE models were established, and verified by pulling the fabricated screws out of Sawbone blocks. The pulling out processes of screws from bone were simulated to explore the optimizing design of the screw. ResultsThe mechanical properties of the screw could be adjusted in a wide range. The biomechanical interaction between the screw and bone can affect the anti-pullout performance of the screw. With an identical elastic modulus (E), better auxiticity of the screw, resulted in a better anti-pullout performance; while an appropriate E is the necessary condition for its excellent anti-pullout performance for a particular bone. ConclusionAppropriate mechanical properties are necessary for the auxetic pedicle screw with excellent screw-bone fixation performance for a particular bone, which can be obtained by rationally designing the wall thickness and re-entrant angle of the unit cells.

Fatigue performance of auxetic meta-biomaterials

Meta-biomaterials offer a promising route towards the development of life-lasting implants. The concept aims to achieve solutions that are ordinarily impossible, by offering a unique combination of mechanical, mass transport, and biological properties through the optimization of their small-scale geometrical and topological designs. In this study, we primarily focus on auxetic meta-biomaterials that have the extraordinary ability to expand in response to axial tension. This could potentially improve the longstanding problem of implant loosening, if their performance can be guaranteed in cyclically loaded conditions. The high-cycle fatigue performance of additively manufactured (AM) auxetic meta-biomaterials made from commercially pure titanium (CP-Ti) was therefore studied. Small variations in the geometry of the re-entrant hexagonal honeycomb unit cell and its relative density resulted in twelve different designs (relative density: ~5–45%, re-entrant angle = 10–25°, Poisson's ratio = -0.076 to -0.504). Micro-computed tomography, scanning electron microscopy and mechanical testing were used to respectively measure the morphological and quasi-static properties of the specimens before proceeding with compression-compression fatigue testing. These auxetic meta-biomaterials exhibited morphological and mechanical properties that are deemed appropriate for bone implant applications (elastic modulus = 66.3–5648 MPa, yield strength = 1.4–46.7 MPa, pore size = 1.3–2.7 mm). With an average maximum stress level of 0.47 σy at 106 cycles (range: 0.35 σyσy- 0.82 σyσy), the auxetic structures characterized here are superior to many other non-auxetic meta-biomaterials made from the same material. The optimization of the printing process and the potential application of post-processing treatments could improve their performance in cyclically loaded settings even further. Statement of SignificanceAuxetic meta-biomaterials have a negative Poisson's ratio and, therefore, expand laterally in response to axial tension. Recently, they have been found to restore bone-implant contact along the lateral side of a hip stem. As a result, the bone will be compressed along both of the implant's contact lines, thereby actively reducing the risk of implant failure. In this case the material will be subjected to cyclic loading, for which no experimental data has been reported yet. Here, we present the first ever study of the fatigue performance of additively manufactured auxetic meta-biomaterials based on the re-entrant hexagonal honeycomb. These results will advance the adoption of auxetic meta-biomaterials in load-bearing applications, such as the hip stem, to potentially improve implant longevity.