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In recent years, communication systems, including RFID, have been used in intelligent beehives for beekeeping. RFID systems in the UHF frequency band offer reading distances of tens of centimetres, allowing the localisation and identification of the queen bee inside the hive. With this purpose, this work proposes an analysis of an environment of propagation that consists of a honeycomb frame, where the reader is placed within the frame, and the tag is placed in different positions over it. A honeycomb frame consists of a wooden box containing a honey wax panel, supported by metallic wires. The environment is modelled theoretically using its S-parameters and simulated in CST Studio. An analysis of these results and empirical measurements is performed. The results show that a periodicity in the received power of the tag is found with respect to the distance to the reader when the tag is located in a direction parallel to the wire, where local maximum and minimum values are found. Additionally, when the tag is placed over a wire of the frame, a higher received power is obtained compared to the case where the tag is placed between two wires. Furthermore, it has been observed that the reading range has increased with respect to free space, covering the full frame. [ABSTRACT FROM AUTHOR]

In response to the shortcomings of concentrated stress, difficult forming, and short service life of commonly used honeycomb ceramic thermal storage materials with square lattice holes, the author has developed a new type of low stress honeycomb ceramic thermal storage material by studying the structure, forming mold, and extrusion forming material of the thermal storage body. The author introduced the changes in specific surface area and porosity of heat storage materials with different geometric structures, and analyzed and compared the structural characteristics of two types of heat storage materials, namely heat storage balls and honeycomb bodies, under the premise of equal heat storage capacity. The trajectory of air-flow in the heat storage chamber was simulated using CFD software, and the pressure loss and centerline velocity changes of different shapes of honeycomb were analyzed. The flow characteristics, pressure distribution, and heat transfer performance of gas inside different shapes of honeycomb were calculated. The experimental results showed that the closer to the circular shape, the smaller the pressure loss of the centerline. The larger the equivalent diameter, the smaller the resistance along the path. From the perspective of cold pressure loss alone, regular quadrilateral holes and regular circular holes are the best choices for the shape of honeycomb openings. The centerline velocity of the equilateral triangle hole is the largest, indicating that the smaller the equivalent diameter is, the greater the average velocity at the outlet is. The resistance along the path of the round hole is the smallest, the regular quadrilateral hole is slightly larger, and the pressure loss of the equilateral triangle hole is the largest, which exceeds the round hole by nearly 1/3. Taking into account factors such as heat storage, specific surface area, flow characteristics, and heat transfer characteristics, quadrilateral honeycomb cells are the best choice. [ABSTRACT FROM AUTHOR]

This paper presents an innovative method of constructing energy absorbers, whose primary function is to effectively transform kinetic energy into strain energy in events with high deformation rates. Hybrid specimens are proposed considering thin-walled windowed metallic tubes filled with 3D-printed hexagonal honeycombs made of PET-G and ABS thermoplastic. The patterned windows dimensions vary from 20 × 20, 20 × 30, 15 × 20 and 15 × 30 mm2. Although using polymers in engineering and thin-walled sections is not new, their combination has not been explored in this type of structure designed to withstand impacts. Specimens resist out-of-plane quasi-static axial loading, and test results are analyzed, demonstrating that polymer core gives the samples better performance parameters than unfilled samples regarding energy absorption (Ea), load rate (LR), and structural effectiveness (η). An optimization procedure using specialized software was applied to evaluate experimental results, which led to identifying the optimal window geometry (16.4 × 20 mm2, in case) and polymer to be used (ABS). The optimized sample was constructed and tested for axial compression to validate the optimization outcomes. The results reveal that the optimal sample performed similarly to the estimated parameters, making this geometry the best choice under the test conditions. [ABSTRACT FROM AUTHOR]

The aim of current research was to improve water quality by constructing a single slope basin type solar water distillation system with honeycomb, as well as to increase distilled water productivity. In this investigation, honeycomb structure of 2.25 cm and a diameter of 6 mm in a square section (100 cm x100 cm) have been proposed to enhance the efficiency of the solar still. An experimental analysis was done to investigate the performance of the honeycomb structure. Thermal efficiency of the standard solar distillation system was obtained approximately 18.48%, while the thermal efficiency and productivity of the solar distillation system with honeycomb was obtained 25.45% and 749.58 ml/m² respectively. It was concluded that, the solar distillation system with honeycomb structure was more efficient that a simple conventional solar distillation system. The addition of honeycomb structure in simple solar desalination system increased the productivity and efficiency by 35.36% and 37.71% respectively. [ABSTRACT FROM AUTHOR]

Energy-absorbing materials have extensive applications in aerospace and automotive applications. Research has shown buckling initiators, or triggers, in energy-absorbing tubular structures increase the energy absorbed by encouraging the side panels to fold when loaded out of plane in compression conditions. Additively manufactured TPE honeycombs were designed in this study to include these buckling initiators, which introduced a slight decrease in initial weight, as well as initial stress concentrations, while improving crashworthiness characteristics. The samples with buckling initiators (1BI) showed an increase in crush efficiency when directly compared to their no buckling initiator (0BI) counterparts. The 1BI samples maintained an increased crush efficiency regardless of the strain rate used. The samples with 1BI were able to better equilibrate the peak stress with the plateau stress. These honeycomb samples were found to maintain their crush efficiency, even after multiple rounds of compression testing. The quasi-static 0BI samples experienced a 23.4% decrease in the peak stress after multiple rounds of compression testing, while the 1BI samples saw approximately a 23.0% decrease. The 1BI samples averaged a decrease in crush efficiency of 0.5%, while the 0BI samples saw a decrease in crush efficiency of 5%. As the strain rate increased, the crush efficiency for the 1BI samples showed an increase in performance, with a smaller degradation in crush efficiency over multiple uses. Visco-elastic honeycomb with buckling initiators has a higher energy absorption than samples with no buckling initiators when exposed to multiple impact cycles. [ABSTRACT FROM AUTHOR]

Auxetic honeycomb has unique mechanical properties such as good energy absorption capacity, tensile strength and fracture toughness, etc. Therefore, honeycomb with a negative Poisson's ratio is used widely in medical, biological, aerospace and other fields. This honeycomb has large deformations in energy absorption and vibration reduction. It is very important to study the nonlinear constitutive of the honeycomb structure. Therefore, this paper establishes the nonlinear constitutive relationship of the auxetic honeycomb structure under large deformations. This constitutive relation includes the in-plane stress, in-plane strain, Young's modulus and Poisson's ratio of the negative Poisson's ratio honeycomb. The finite element model of the negative Poisson's ratio honeycomb cells is established, and the calculated results of finite element model are compared with that of the theoretical calculation results. On this basis, the influence of the geometric parameters on the mechanical properties of the structure is studied. The results of this paper will provide a theoretical basis for the further study of the auxetic honeycomb sandwich structure and provide a basis for the engineering application of honeycomb structures. [ABSTRACT FROM AUTHOR]

Aluminum honeycomb structures are used in the construction of protective materials due to the positive relationship between their mass and their energy-absorbing properties. Applying such materials in the construction of large machinery, such as military vehicles, requires the development of a new method of finite element modeling, one that considers conditions with high strain rates, because a material model is currently lacking in the available simulation software, including LS-DYNA. In the present study, we proposed and verified a method of numerically modeling honeycomb materials using a simplified Y element. Results with a good level of agreement between the full core model and the Y element were achieved. The obtained description of the material properties was used in the subsequent creation of a homogeneous model. In addition, we considered the influence of increases in pressure and the leakage of the air entrapped in the honeycomb cells. As a result, we were able to attain a high level of accuracy regarding the stress values across the entire range of progressive failure, from the loss of stability to full core densification, and across a wide range of strain rates. [ABSTRACT FROM AUTHOR]

Numerical simulations were carried out in this study to explore the response of the reinforced honeycomb sandwich structure with varying cell sizes (7, 10, and 15 mm), node lengths (25, 37.5, and 50 mm), and cell wall thicknesses (0.1, 0.2, 0.3, and 0.4 mm). The honeycomb structure made of aluminum alloy 8011 was subjected to low intensity blast loads by varying masses of TNT (10 g, 15 g, 20 g, and 25 g) and standoff distances (200 mm, 250 mm, and 300 mm). Commercial finite element code LS-DYNA was employed to carry out numerical simulations for both conventional and reinforced honeycomb sandwich structures keeping identical geometrical and blast load parameters. The deformation of the back facesheet was a major parameter to establish blast resistance of the core. Failure mechanisms of reinforced honeycomb were characterized as fully folded region, partially folded region, and clamped region. Reinforced honeycomb sandwich outperformed the conventional honeycomb sandwich structure of identical geometry parameters under similar blast loads. The increase in cell-wall thickness and node length enhanced the blast resistance, whereas the increment in cell size reduced the blast resistance of the reinforced honeycomb sandwich structure. [ABSTRACT FROM AUTHOR]

We proposed a novel class of honeycomb structures inspired by triply periodic minimal surfaces (TPMS) architecture with tuneable mechanical responses. The design procedure based on the level-set approximation was first introduced for two TPMS-based honeycombs, namely GHoneycomb and P-Honeycomb. A numerical model was developed and validated by experimental results to evaluate the mechanical properties of G-Honeycomb and P-Honeycomb lattices. The results showed that P-Honeycomb exhibited higher elastic modulus and plateau stress than G-Honeycomb at various relative densities. Meanwhile, both TPMS-based honeycombs showed higher in-plane elastic modulus than conventional square honeycombs, although they had the same nodal connectivity. The idea of designing lattices with tuneable mechanical responses was achieved by introducing a density gradient or creating a G-P hybrid structure with the topology of G-Honeycomb and P-Honeycomb in different regions. The graded structures showed gradual stiffening and progressive collapse under compression, while the G-P hybrid structure can exhibit distinct properties at different compressive strains. [ABSTRACT FROM AUTHOR]

In this review, we present a comprehensive summary of the formation of honeycomb microstructures and their applications, which include tissue engineering, antibacterial materials, replication processes or sensors. The history of the honeycomb pattern, the first experiments, which mostly involved the breath figure procedure and the improved phase separation, the most recent approach to honeycomb pattern formation, are described in detail. Subsequent surface modifications of the pattern, which involve physical and chemical modifications and further enhancement of the surface properties, are also introduced. Different aspects influencing the polymer formation, such as the substrate influence, a particular polymer or solvent, which may significantly contribute to pattern formation, and thus influence the target structural properties, are also discussed. [ABSTRACT FROM AUTHOR]

In this work, we reported a theoretical model for a novel piezoelectric micromachined ultrasonic transducer (PMUT). The sensing cells with hexagonal transduction diaphragms in the PMUT array are designed and arranged in a bioinspired honeycomb structure. Based on the classical piece-wise approach commonly used for PMUT with circular diaphragm, an enhanced theoretical model is developed. In this model, the deflection of the honeycomb diaphragm is analytically determined by the volume deflection, rather than the path deflection commonly used in the previous models. The hexagonal diaphragm is converted as a circular one, whose radius is derived by correcting the characteristic size of the hexagonal diaphragm multiplied by a correction factor. The calculated parameters by the reported theoretical model of a transduction cell in the PMUT array, such as resonant frequency and static deflection, matched well with the data obtained by finite element analysis and experiment. Special investigations are made on the effects of top electrode coverage and transduction layer thickness towards PMUT’s performance. The reported theoretical model in this work is suitable not only for PMUTs with circular and hexagonal transduction cells, but also for square and other arbitrary shape diaphragms. This enhanced theoretical model provides an interesting insight on design optimizations of PMUT with various transduction cell geometries. [2022-0093] [ABSTRACT FROM AUTHOR]

Honeycombs are essential elements in mechanical systems where low weight and high strength are required. Aluminum and Nomex® are the most commonly used honeycomb materials in structures exposed to compression stress. The primary purpose of this study is to verify the compression behavior of honeycombs in Ls-Dyna using experimental values and theoretical equations. Additionally, it is aimed to evaluate the honeycombs parameters such as cell diameter, cell wall thickness, and material. A correlation matrix was created using the Python/Seaborn program to examine the impact coefficients of the parameters. In this way, the effect of design parameters on compression strength and internal energy was investigated. [ABSTRACT FROM AUTHOR]

In this article, we present a unique combination of techniques focusing on the immobilization of noble metal nanoparticles into a honeycomb polystyrene pattern prepared with the improved phase-separation technique. The procedure consists of two main steps: the preparation of the honeycomb pattern (HCP) on a perfluoroethylenepropylene substrate (FEP), followed by an immobilization procedure realized by the honeycomb pattern's exposure to an excimer laser in a noble metal nanoparticle solution. The surface physico-chemical properties, mainly the surface morphology and chemistry, are characterized in detail in the study. The two-step procedure represents the unique architecture of the surface immobilization process, which reveals a wide range of potential applications, mainly in tissue engineering, but also as substrates for analytical use. [ABSTRACT FROM AUTHOR]

Manufacturing aircraft components through 3D printing has become a widespread concept with proven applicability for serial production of certain structural parts. The main objective of the research study is to determine whether a chlorinated polyethylene material reinforced with milled carbon fibers has the potential of replacing the current 5052 NIDA aluminum alloy core of the IAR330 helicopter tail rotor blade, under the form of a honeycomb structure with hexagonal cells. Achieving this purpose implied determining the tensile and compression mechanical properties of the material realized by fused deposition modeling. The tensile tests have been conducted on specimens manufactured on three printing directions, so that the orthotropic nature of the material may be taken into account. The bare compression tests were realized on specimens manufactured from both materials, with similar honeycomb characteristics. All the mechanical tests have been performed on the Instron 8872 servo hydraulic testing system and the results have been evaluated with the Dantec Q400 Digital Image Correlation system. The experimental tests have been reproduced as finite element analyses which have been validated by results comparison, in order to determine if the compression model is viable for more complex numerical analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • We fabricated carbonate apatite honeycomb scaffolds with vertical uniaxial channels. • At 4 weeks post implantation, all honeycomb scaffolds augmented new bone. • The augmentation happened close to the top surface of the scaffold. • In the following 8 weeks, the height and amount of new bone increased. • HC300 resisted compression from fasciae at 12-weeks post implantation. • Honeycomb structure is inherently suitable for vertical bone augmentation. Cases of intractable dental implant require vertical bone augmentation; however, the predicted bone height and volume are difficult to obtain. In vertical bone augmentation, the contact surface between the scaffold and the bone is limited to the bottom face of the scaffold. Furthermore, the strength decrease caused by scaffold resorption leads to collapse of the augmented site, leading to a decrease in the bone volume and height. To promote bone ingrowth, we fabricated carbonate apatite (i.e., bone mineral) honeycomb (HC) scaffolds with uniaxial channels vertically penetrating the scaffold. Furthermore, we controlled the scaffold resorption rate, eventually the endurability for compression, and the bone height and volume by controlling the strut thickness. The channel aperture was controlled to be 230–260 μm to promote bone ingrowth. Furthermore, the strut thicknesses of the HC scaffolds were adjusted to 100, 200, and 300 μm to control the scaffold resorption; these scaffolds were designated as HC100, HC200, and HC300, respectively. At 4 weeks post-implantation on rabbit calvarium, all scaffolds had already vertically augmented new bone close to the top surface of the scaffold. In the following 8 weeks, the height and amount of new bone in all scaffolds increased. Notably, HC300 was resorbed synchronously with new bone formation, allowing it to endure the compression from the fasciae for 12 weeks post-implantation. Furthermore, HC300 formed larger-diameter blood vessels than those of HC100 and HC200. The HC scaffolds surpassed the various combined scaffolds and growth factors or stem cells in the ability for vertical bone augmentation. Thus, the HC structure is inherently suitable for vertical bone augmentation. Notably, the HC scaffolds with 300-μm-thick struts enhanced both new bone formation and angiogenesis. This study revealed a structurally suitable design for achieving an outstanding outcome in vertical bone augmentation. [ABSTRACT FROM AUTHOR]

The all-composite sandwich structure with the honeycomb core is a lightweight and high-strength structure with broad application scenarios. The face sheet and honeycomb core of the proposed all-composite sandwich structure in this work are composed of carbon-fiber-reinforced polymer (CFRP) composites. The mechanical response and damage mechanism of the all-composite sandwich structure under out-of-plane quasi-static compression and out-of-plane impact are studied by numerical methods. The refined finite element models of the sandwich structures are built on the ABAQUS/Explicit platform. The micromechanics of failure (MMF) theory based on physical component failure is used to describe the intralaminar damage mechanism of the face sheet and honeycomb core, and the mixed-mode exponential cohesive zone model (ECZM) is utilized to simulate the initiation and evolution of interlayer damage. In addition, the cohesive contact approach is adopted to capture the debonding failure at the face-sheet/core. The numerical results show that the all-composite sandwich structure has the characteristics of large structural stiffness and strong energy absorption ability. The failure mechanism of the all-composite sandwich structure under compression is mainly matrix damage and delamination of the honeycomb core, with buckling and folding in appearance. Under out-of-plane impact, matrix damage and delamination arise on the upper sheet, little damage is observed on the lower sheet, and the delamination damage morphology tends to be circular with increasing impact energy. In addition, the interface failure of the upper-sheet/core is more than that of the lower-sheet/core. In addition, the matrix damage near the impact center of the honeycomb core tends to be consistent with the delamination contour, and a small amount of fiber failure is also observed, which manifests as a collapse morphology of the impact area. The research results enrich the understanding of the mechanical behavior of all-composite sandwich structures with honeycomb cores and provide theoretical support for their potential applications. [ABSTRACT FROM AUTHOR]

In this work, carbonated hydroxyapatite/titanium alloy (CHA/Ti) and carbonated hydroxyapatite/honeycomb/titanium alloy (CHA/HCB/Ti) plates were coated using the electrophoretic deposition dip coating (EP2D) method. Analysis of cell viability and surface morphology of CHA/Ti and CHA/HCB/Ti coatings were carried out using the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and scanning electron microscopy (SEM), respectively. In a previous study, the thickness and average compressive strength values for the CHA/Ti and CHA/HCB/Ti plates were about 63–89 μm and 54–75 MPa, respectively. The result for thickness and compressive strength in this research followed the thickness and compressive strength parameters for coating in bone implants. In this work, the cell viability for incubation times during 24 h and 48 h of CHA/Ti plates is demonstrably superior to that of CHA/HCB/Ti plates, respectively, where the cell viability for CHA/Ti plates increased to ((67 ± 2)%) after incubation for 48 h. According to the one-way analysis of variance (ANOVA), the p-value was <0.05, indicating a significant difference in the average cell viability value across the three groups. Furthermore, the surface of CHA/Ti is not changed after the coating process. These results will yield many positive biomedical applications, especially in bone implants. Overall, CHA/Ti and CHA/HCB/Ti plates can be considered candidates for biomedical applications based on an analysis of surface morphology and cell viability. [ABSTRACT FROM AUTHOR]

• PVA/CNF@14GO filled honeycomb composites at 30 mm achieve a broadband effective absorption performance of 13.25 GHz. • Honeycomb composites allows for broadband microwave absorption and enhanced structural strength. • The electromagnetic parameters of honeycomb composites can be precisely controlled. • The honeycomb composites were expected to be used for aviation stealth based on the light weight and broadband performance. Lightweight structural/microwave absorption (MA) integrated materials with broadband MA are urgently needed in the aerospace field. In this study, crosslinked PVA/CNF backbone-supported RGO foams were successfully filled into aramid honeycomb structures with significant broadband MA performance and structural enhancement properties through a synergistic strategy of chemical crosslinking, environmental drying and chemical vapor reduction. Flexible tuning of the electromagnetic parameters of the PVA/CNF@GO foam can be achieved by adjusting the number of GO parts. The 30 mm thickness of the PVA/CNF@14GO foam achieves a broadband effective absorption of 13.25 GHz, covering almost all C, X and Ku bands. Microstructural characterization and electromagnetic parameter tests proved that the uniform distribution of RGO was achieved with crosslinked PVA/CNF as the backbone, which resulted in less Debye relaxation and the construction of uniform conductive pathways. Therefore, the PVA/CNF@14GO-filled honeycomb not only enables the composite honeycomb to achieve broadband MA performance, but also achieves a compressive strength of 5.52 MPa, which is an improvement of 262.86 % with respect to that of the pure honeycomb. The obvious overlap of the CST power loss distribution and the electric field distribution region shows that the conductive loss and the 1/4 wavelength interference are the main paths for energy dissipation in the composite of the PVA/CNF@GO-filled honeycomb. The honeycomb-filled PVA/CNF@GO lightweight foams obtained in this chapter have good broadband microwave absorption properties and higher structural strength, which provide important design strategies and practical references for the development of high-performance MA-filled honeycomb structures. [ABSTRACT FROM AUTHOR]

The development of an efficient microwave absorbing structure (MAS) for the concealment of electromagnetic (EM) waves is a consistent puzzling errand. In this regard, a new kind of lightweight broadband multilayer honeycomb (HC)-MAS is developed, by coating aramid HC with Fe/SiC polymeric paint optimized using effective medium approximations. An environment-friendly, cost-effective, and easily accessible procedure is embraced for the preparation of microwave absorbing paint and diverse coatings at X-band. The multi-objective Jaya’s algorithm is envisioned for the optimum design of multilayered and hybrid HC-MASs. A multi-objective fitness function is integrated into the optimization algorithm to resolve the issue of the thickness-bandwidth (BW) tradeoff. As a result, optimized single layer HC-MAS with thickness 2.1 mm attains a reflection coefficient (RC) of −12.0 dB at 10.3 GHz with a BW of 3.2 GHz below the −10 dB threshold. The intriguing results are obtained by doing a dual-mode analysis, i.e., multilayer HC-MAS and multilayer hybrid HC-MAS. Hybrid HC-MAS achieves an RC of −31 dB at 9.8 GHz with a thickness of 2.8 mm exhibiting 100% BW. Besides, the response of the proposed structure is evaluated for distinct oblique angles of incidence. The findings offer a significant opportunity for the improvement of lightweight and broadband HC-MAS for stealth applications. [ABSTRACT FROM AUTHOR]

• Side impact effects on a LIB pack are numerically investigated using the FE approach. • Honeycomb reinforcement is introduced to minimize the side impact on the LIB cell components. • Three different materials were used for the honeycomb structure: AHSS, AISI316L, and Al7075-T5. • The absorbed energy is reduced by 18.7% on average due to the application of the honeycomb reinforcement structure. • The proposed honeycomb reinforcement reduced the lateral penetration by around 20.7% on average. • The temperature contours revealed that the honeycomb reinforcement was able to prevent short-circuit. Protection of lithium-ion batteries (LIB) from collision-related damage is a critical concern for electric vehicle (EV) manufacturers. However, predicting damage to the standard 18,650 LIB cells from external side impacts has received little attention. This study aims to numerically estimate the damage to the LIB pack attached to a Toyota Camry car model during a side impact at 32 km/h using a finite element approach. A honeycomb reinforcement design is proposed to mitigate side impact effects by adopting a special arrangement. The battery pack, consisting of 12 modules each with 417 LIB cells, was attached to the vehicle bottom in a "floor" configuration. Four scenarios were simulated, namely (i) baseline [no reinforcement, (S1)], (ii) LIB module with Aluminium Alloy 7075-T6 reinforcement (S2), (iii) LIB module with Stainless Steel 316L reinforcement (S3), and (iv) LIB module with Advanced High Strength Steel reinforcement (S4). Numerical results showed that among the 12 battery modules, only one suffered from significant damage in all scenarios. The maximum penetration for the baseline scenario was found to be 79.29 mm. The penetration was reduced by 22.4 %, 20.2 %, and 19.4 % after including the proposed reinforcement structure and using AHSS, AISI316L, and Al7075-T5 materials, respectively. The absorbed energy by the LIB cell component was reduced by around 0.5 MJ (i.e., 18.7 % reduction) when using the proposed reinforcement. The outcomes of this study showed the ability of the proposed reinforcement structure to mitigate the side impact effects on the LIB cells; however, further optimization studies using different materials and thicknesses are recommended. [ABSTRACT FROM AUTHOR]

• Face-centered hierarchical strategy is proposed to develop a novel honeycomb. • Face-centered hierarchical network provides strong lateral support to resist the multi-crushing loads. • Effect of hierarchy order and thickness gradient is significant on the multi-crushing properties. • Face-centered hierarchical honeycomb possesses the more stable and efficient multi-crushing properties. The undesirable resistance to multi-crushing loads limits the development of regular honeycomb structures in advanced engineering fields. Therefore, a novel hierarchical strategy, namely face-centered hierarchical strategy, is proposed to improve the multi-crushing properties of honeycombs. The honeycombs with the face-centered hierarchical network are manufactured by selective laser melting to test their energy absorption mechanism against the oblique crushing load. The multi-crushing properties of face-centered hierarchical honeycomb (FCHH) are explored by a numerical investigation. The carrying capacity and energy absorption of the FCHH decrease with the increasing crushing angle. The parameter configuration design indicates that the hierarchy order has a positive effect on the multi-crushing resistance of the FCHH. The face-centered hierarchical network not only provides the strong lateral support, improving the collapse of the honeycomb, but also reduces the folding wavelength, improving its material utilization. Specifically, the specific energy absorption and crushing force efficiency of the FCHH improve by 27.65 % and 30.83 % respectively as the hierarchy order increases from 1 to 3 at the crushing angle of 30°. Furthermore, when the thickness gradient factor is close to 1, the FCHH obtains a more reasonable material distribution to resist the oblique crushing load. Compared with other hierarchical honeycombs for the oblique crushing resistance, the FCHH demonstrates a more stable carrying process and more efficient energy absorption. This research expects to propose a promising reinforcement strategy to guide the design of multi-crushing properties for honeycombs. [Display omitted] [ABSTRACT FROM AUTHOR]

Metamaterial structures that exhibit negative stiffness (MSNS) behavior have shown the potential to be used as energy dissipation systems in different applications. Negative stiffness honeycomb structures consist of multiple pre-buckled beams that snapping through from one pre-buckled mode to another buckled mode, when subjected to transverse loads, displaying negative stiffness, and dissipating a significant portion of the input energy. This paper presents finite element models (FEMs) developed to investigate the performance of negative stiffness pre-buckled beams and honeycombs. The FEMs were validated using experimental results of single pre-buckled beams and honeycomb structures. The experimental testing of the pre-buckled beams was presented in the current study while the results of the honeycomb were available in the literature. The FEMs have the ability to capture the transition of the elements from one mode of buckling to another mode as well as the force thresholds, energy dissipation values, and residual displacements. The FEMs were extended to investigate the effect of different parameters such as boundary condition, apex height-to-beam thickness ratio, and constraining the second mode of buckling on the behavior of negative stiffness honeycombs. • Metamaterial structures that exhibit negative stiffness (MSNS) have potential for use in energy dissipation systems. • Finite element models (FEMs) are presented to study the performance of MSNS beams and honeycombs. • FEMs are validated using experimental results from single pre-buckled beams and honeycomb structures. • FEMs can accurately predict transitions between different modes of buckling, force thresholds, and energy dissipation. [ABSTRACT FROM AUTHOR]

• 3D bi-material triangle re-entrant honeycomb with adjustable Poisson's ratio is proposed. • The intrinsic mechanisms of tunable CTE and PR are revealed by theoretical models. • The finite element analysis is used to calculate the band structures and width of the total effective bandgap. • This work provides a design idea for 3D metamaterials to regulate CTE, PR and the bandgap. In the aerospace industry, precision components need to serve in a comprehensive environment of severe temperature changes, vibrations, and noise. Therefore, it is necessary to design a multifunctional mechanical metamaterial that integrates a tunable coefficient of thermal expansion (CTE), Poisson's ratio (PR), and bandgap. Here, a 3D bi-material triangle re-entrant honeycomb (3D-BTRH) with adjustable Poisson's ratio is proposed. Due to the geometric symmetry, the 3D-BTRH realizes the isotropy of mechanical properties in the three coordinate axes. The intrinsic mechanisms of tunable CTE and PR of the 3D-BTRH are revealed by building theoretical models. The accuracy of the theoretical analysis of PR and Young's modulus is verified by simulation and experiment. The finite element analysis is used to calculate the band structures and width of the total effective bandgap utilizing Bloch's theorem and Bloch's periodic boundary conditions. The accuracy of the band structure calculations is verified by calculating the transmission characteristic curve. The parametric analysis shows that the 3D-BTRH can achieve tunable CTE and PR in the directions of the three axes, and has a large width of the total effective bandgap. Moreover, this work provides a design idea for 3D metamaterials to simultaneously regulate CTE, PR, and the bandgap, which offers opportunities for better engineering practice. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • S-shaped reinforced cores are designed by flattening hexagonal honeycomb cores. • S-shaped reinforced structures can effectively change the deformation mode of cores. • The peak load of S-shaped reinforced core can be 86.12% greater than plain core. • Theoretical prediction model of S-shaped reinforced honeycomb cores is proposed. • The design capabilities of cores are expanded because of S-shaped structure. Honeycomb structures serve as the core of sandwich structures in various industries, such as aerospace and rail transit. In this study, a novel design was introduced where hexagonal honeycomb cores were flattened in specific areas to form S-shaped reinforced cores. Compression tests were conducted on S-shaped reinforced honeycomb cores with different rotational structures – left-hand, right-hand, and mixed rotation. The deformation process of these cores was thoroughly investigated. Additionally, a theoretical prediction model was proposed to determine the Young's modulus and peak load of S-shaped reinforced honeycomb cores. The experimental data was compared with the theoretical model to validate its accuracy. Moreover, the study examined the effects of changing the relative density and cell wall angle of S-shaped reinforced honeycomb cores on the peak and specific peak loads. The results demonstrated that the use of S-shaped reinforced structures successfully altered the deformation mode of the honeycomb cores. In particular, the peak loads of S-LL and S-LR specimens were 29.14% and 86.12% higher than that of plain honeycomb, respectively. In summary, increasing the relative density of S-shaped reinforced honeycomb cores proved to enhance the peak load and specific peak load, thereby augmenting the design capabilities of these cores. [ABSTRACT FROM AUTHOR]

• The effects of GDGQD reinforcement on GFRP honeycomb sandwich shells are investigated. • The mechanical characteristics of the GDGQD-reinforced GFRP composites were evaluated using experimental tests. • The GDGQD-GFRP composite surfaces were observed using SEM analysis. • HSDT is employed to model the GDGQD-reinforced GFRP sandwich shells. • The influences of various parameters on the bending and dynamic behavior of the GFRP sandwich shells are studied. The present study employs a finite element (FE) formulation to examine the free vibration and bending analyses of sandwich shells made of a glass fiber reinforced polymer (GFRP) composite honeycomb core and graphene decorated with graphene quantum dots (GDGQD) reinforced by GFRP composite face layers. The mechanical characteristics of the GFRP composites with GDGQD reinforcement were evaluated using experimental tests. The FE formulation was developed to compute the vibration and bending responses of the sandwich shells via MATLAB software. The Lagrange method is used for dynamic analysis, whereas the principle of potential energy is used for static analysis. The FE model's validity is compared to numerical data reported in the literature in terms of frequencies and deflection, and the results demonstrate excellent agreement. The impacts of the end conditions, core-to-facesheet thickness ratio, curvature ratios, and weight percent of GDGQD are studied further in relation to the bending and dynamic properties of GFRP sandwich shells. [ABSTRACT FROM AUTHOR]

Continuous-carbon-fibre-reinforced (CCFR) honeycomb structures with self-sensing abilities were fabricated by three-dimensional (3D) printing. Pure polylactic acid (PLA) honeycombs of the same size were also fabricated for comparison. Low-velocity impact (LVI) tests and compression after impact (CAI) tests were conducted. Cone beam computed tomography (CBCT) and scanning electron microscope (SEM) were employed to investigate the corresponding damage mechanisms. The LVI test results showed that the presence of continuous carbon fibre effectively inhibited the generation and propagation of the damage in the matrix during impact, which allowed the CCFR honeycomb structure to have better low-velocity impact resistance, especially for repeated impacts with small energies. In contrast to the PLA honeycomb, the CAI test results showed that the CCFR honeycomb still retained good specific compression strength and specific energy absorption properties even after experiencing impacts. Furthermore, the continuous carbon fibre integrated into the CCFR honeycomb could be used as a sensor element to realize the in-situ structural health monitoring during impact and compression. The 3D-printed CCFR honeycomb structure, investigated in this research, demonstrates remarkable mechanical performance and self-sensing capabilities both during LVI and CAI tests, which highlights the vast potential of 3D-printed CCFR honeycomb for diverse applications. [Display omitted] • Continuous carbon fiber (CCF) inhibits the damage generation in the matrix. • 3D-printed CCFR honeycomb has better impact resistance compared to PLA honeycomb. • CCFR honeycomb after low-velocity impact still has high compression performance. • CCF can be a sensing element for structural health monitoring of CCFR honeycomb. [ABSTRACT FROM AUTHOR]

In this paper, the thermal shock resistance of an auxetic ceramic honeycomb plate is studied based on the fracture mechanics concept for the cases of a central crack or an edge crack. The transient temperature field and transient thermal stress field are obtained for both auxetic and non-auxetic structures. The relationship between the thermal stress intensity factor (TSIF) and the internal cell angle, crack length and time is determined and the critical temperature for the initiation of crack propagation is predicted. Results show that compared with the non-auxetic ceramic honeycombs which are at an internal cell angle of 30°, the critical temperature of the auxetic ceramic honeycombs whose cell are orientated at an angle of −30° increases by 78.5% and the TSIF at the crack tip decreases by 40%, respectively. Hence, the auxetic structures have better thermal shock resistance. This study indicates that auxetic ceramic honeycombs have significant potential applications in harsh temperature environments. [ABSTRACT FROM AUTHOR]

• A two-stage hybrid optimization for honeycomb structures is proposed. • The material properties and wall thickness are considered. • The Taguchi-based grey correlation discrete optimization is applied. • The proposed algorithm can be used to solve more complicated problems. Honeycomb structures with better balance between lightweight and crashworthiness have aroused growing attentions. However, structural parameters design by traditional optimization algorithm in small design space is not sufficient to significantly enhance the specific energy absorption (SEA) with the lower peak acceleration (a max). In this paper, a two-stage hybrid optimization for honeycomb-type cellular parameters is proposed to achieve rapid positioning of design space and significantly increase crashworthiness in a larger variable domain under out-of-plane dynamic impact. In stage I, a Taguchi-based grey correlation discrete optimization, combining Taguchi analysis, grey relational analysis, analysis of variance (ANOVA) with grey entropy measurement, is performed to determine the initial optimal value with a higher robustness and the significant influence variables. In stage II, a multi-objective design technique, namely non-nominated sorting genetic algorithm II based on surrogated model, is adopted to maximize the SEA and minimize the a max in a relatively small design domain. And it is found that the proposed two-stage hybrid method can broaden the optimal design space compared to that of traditional method attributable to its center point positioned by stage I. And the final optimization based on the proposed strategy is superior to the original structure, i.e., the SEA is increased by 47.55% and the a max is decreased by 80.8%. Therefore, the proposed algorithm can also be used to solve other more complicated engineering problems in a large design space with insightful design data. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive experimental investigation was carried out to precisely characterize the delamination and uncut fiber in the drilling process. A digital imaging procedure was developed in order to calculate the damage resulted from the drilling process. A novel method is proposed in this article based on image intensity to verify the obtained results. A full factorial experimental design was performed to evaluate the importance of the drilling parameters. Among other process parameters, feed rate, cutting speed, and tool diameter are the principal factors responsible for the delamination damage size during the drilling. The drilling process was assessed based on two proposed incurred damage factors, specifically the delamination factor and uncut fiber factor. Experimental results demonstrated that the feed rate was the paramount parameter for both delamination and uncut fiber factors. It was observed that both factors increased with an increase in the feed rate. Additionally, by increasing the tool diameter, the delamination and uncut fiber factors significantly increase. The effects of the cutting speed on damage factors were not linear. The minimum delamination factor and uncut fiber factor were obtained at the cutting speed of 1500 and 2500 r/min, respectively. [ABSTRACT FROM AUTHOR]

Ceramic honeycombs exhibit unique mechanical properties based on engineered formulations and geometry of cells. Extrusion of formable paste through a complex honeycomb die is the commonly practiced technique for the manufacturing of honeycombs globally. Extrusion die fabrication is a complex process which necessitates sophisticated infrastructure facilities that provide high geometrical accuracy and finish to produce defect free honeycombs. Furthermore, every configuration of honeycomb requires a specific tool. Additive manufacturing (AM)/ 3D printing is a rapid prototyping technique which offers flexibility in fabrication of honeycombs with desired geometries from a virtual model directly. Further, this does not require complicated dies. In this study, viscoplastic printable cordierite raw mix paste with a shear rate exponent of 0.87 was printed into honeycombs with hexagonal, square, and triangular cells using a ram type 3D printer. The printed honeycomb samples are found to possess good integrity and near net shape after drying. Sintered 3D‐printed honeycomb samples of all configurations have exhibited cordierite as a major phase along with minor phases of magnesium aluminate (MgAl2O4) spinel, clinoenstatite (MgSiO3), and corundum (Al2O3) with sintered density of 2.41‐2.48 g/cc. The samples are also subjected to compression testing under quasi‐static condition. The study demonstrates 3D printing as a viable and flexible technique for rapid prototyping of honeycombs with desired configurations and engineered properties. [ABSTRACT FROM AUTHOR]

Aluminum honeycombs are widely applied in weight sensitive applications, increasing their specific strength and energy absorption capacity are rather important. Thin-walled metallic tube was used to enhance the mechanical properties of aluminum honeycomb and formed a novel tube-reinforced honeycomb structure. Its compressive and three-point bending performances were studied experimentally and numerically. Due to tube filling, the specific compressive strength, elastic modulus and energy absorption have been increased by 16%, 26% and 73%, and the specific bending load and stiffness increased by 42% and 62% respectively. The strengthen mechanism study indicated that the sum of tube and honeycomb caused the increase of compressive properties, and aluminum tube filling changed the stress distribution and expanded the stress concentration region which led to a transformation of bending failure mode. The present reinforcement method will make honeycomb more competitive in light-weight structure applications. [ABSTRACT FROM AUTHOR]

Nickel-based superalloy honeycomb core (NBSHC) is extensively used in aerospace field due to the light weight, high specific strength and high temperature resistance. The burrs of NBSHC are extremely prone to be formed during machining and the insufficient welding strength or false welding between NBSHC and skin is generated because of the large or unreasonable burr morphology, resulting in premature failure of the parts. In this work, a novel method of ice freezing combining with minimum quantity lubrication (MQL) was proposed to grind NBSHC to improve the burr morphology and size. The burr formation mechanisms of NBSHC under ice freezing and MQL conditions were revealed by single abrasive particle grinding cell wall and verified by grinding experiments. The grinding force, burr morphology transformation mechanisms and size were investigated in-detail by experiments combining with FEM results. The results indicated that MQL and ice freezing decreased the plastic flow property of material by reducing the temperature and friction of NBSHC, thereby promoting the transformation of burr size from large into micro, and the burr shape from long strip into block. Decreasing grinding depth can also improve the burr morphology by decreasing the volume of plastic flow material. The improving effects of full of ice freezing were better than MQL for NBSHC grinding. The machining efficiency under full of ice combining with MQL was 3 times of that under quasi-dry grinding. These findings are significant for improving the machining quality and exploring the burr morphology transformation of NBSHC. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A new auxetic honeycomb was designed by hybriding rhombic and star configurations. • A theoretical model was developed to predict the elastic modulus and Poisson's ratio. • The proposed honeycomb possesses higher auxetic effect and larger specific modulus than the star honeycomb. • The proposed honeycomb exhibits enhanced plateau stress and specific energy absorption compared with conventional auxetic honeycombs. Auxetic structures with negative Poisson's ratio exhibit excellent performance in cushioning, shear resistance and energy absorption, but their load-bearing capacity is usually poor. To address this drawback of the conventional Auxetic structure, a star-rhombic honeycomb (SRH) design is proposed in this paper to improve its load-bearing capacity. Analytical models of the elastic modulus and Poisson's ratio of this structure for different loading directions are developed. Quasi-static compression experiments were conducted on SRH specimens fabricated by selective laser melting (SLM) technique. Good agreement was achieved between the simulated and experimental stress response curves and deformation patterns. It was found that the SRH structure possessed better elastic modulus and energy absorption capacity than the SH structure without sacrificing the auxetic properties. The elastic modulus and Poisson's ratio of SRH under the x loading direction are more sensitive to the changes of structural parameters. An optimum energy absorption performance is achieved for an appropriate ratio of the inner rhombic strut thickness to outer reentrant strut thickness (k = 0.5). The specific energy absorption of SRH is improved by 136% and 75% compared to that of the conventional reentrant honeycomb (RH) and star honeycomb (SH), respectively. It has advantages for application scenarios with requirements for both auxetic and load bearing properties. [ABSTRACT FROM AUTHOR]

Abstract In this study, comprehensive investigations of an innovative composited cellular structure—Honeycomb cells filled with circular aluminum tubes (HFCT) are conducted by means of numerical simulation and theoretical analyses. A conventional honeycomb was modeled to calibrate the numerical model and a good agreement between numerical and experimental results was achieved. With the calibrated numerical model, extensive comparisons between mechanical performances considering the deformation modes, nominal stress and energy absorption property were carried out in terms of HFCT, conventional honeycomb, and multi-tubes. The interaction effects between internal filler and outside container of HFTC were discussed through the comparison considering representative volume elements (RVE) of three structures. In addition, obvious matching effects in terms of cell thickness were observed between the filler and container of HFCT. Afterward, a theoretical model based on the minimum energy principle which considering the basic fold element of HFCT was constructed to determine the key compression characteristics (half-wave length and nominal plateau stress). Agreement between them was found in plateau stress and geometrical description of post-deformation mode. [ABSTRACT FROM AUTHOR]

Abstract Recently, more and more attentions have been paid to structural defect suppression. In this study, branch point algorithm was first constructed for structural irregularity determination of honeycomb structure, so as to identify the geometric defect of similar cellular structures. Detailed principle and process were presented with key steps as image binarization, smoothing & noise suppression , skeletonization , vertex identification and cell reconstruction. A representative illustration was given. Afterwards, the routine difference has been discussed between the present method and classic Harris algorithm. Some examples in different cases were presented. As the findings turned out that, the branch point algorithm efficiently identifies the vertices of each cell with high precision, even in cases of poor images with low resolution. All these achievements pave a way for high standard honeycomb structure in consistency, reliability and homogeneity. [ABSTRACT FROM AUTHOR]

Abstract Damage severity of sandwich panels to underwater explosion load depend not only on the shock factors, but also on the fluid behind the structure. Underwater explosion tests were performed on water-backed sandwich panels to examine the deformation and failure of such composite structure. The dynamic blast response of water-backed sandwich panel was investigated using the LS-DYNA software. An analytical three-stage model was developed for the deformation history of water-backed sandwich panel subjected to shock loading in water. Blast resistance of water-backed sandwich panel was compared with monolithic plate of equivalent areal mass and air-backed sandwich panel with the same configurations. Water-backed sandwich panel exhibited the best deformation/damage resistant capability. Compared with air-backed sandwich panel, core material exhibited greater volumetric strain when the sandwich structure wetted on both sides. Overpressure in the water behind structure was reduced to about 7% by using sandwich structure over monolithic plate of equivalent thickness. Present study led to the apprehension of dynamic response of water-backed sandwich structure to underwater blast load, thereby developed useful guidelines for the design of blast-resistant structural systems. [ABSTRACT FROM AUTHOR]

Abstract In this study, sandwich panels with carbon/epoxy composite skins and an magnetorheological elastomer (MRE) honeycomb core in different proportions of magneto/elastomer (w/w%) are manufactured and studied numerically and experimentally. Test specimens in the beam form are subjected to free and forced vibrations and evaluated with and without the presence of an external (until 120 kA/m) magnetic field, positioned on the free end and on the center of the beam. The experimental results showed good performance in the attenuation of vibration level, especially on the fundamental vibration mode of the structures in question. The applied magnetic field on the free end of the test panel was capable of reducing until 37.45% their first natural frequency value. It can be noted from numerical and experimental results that sandwich panel with MRE honeycomb shifted the natural frequencies due to the increase of an induced magnetic field, especially for the first mode shape. [ABSTRACT FROM AUTHOR]

Abstract Predicting the honeycomb sandwich's response to impact loading is a major challenge in the aeronautical industry. Several papers demonstrated the possible use of non-linear springs to model Nomex's impact behavior. On the other hand, the authors show that the lack of transverse shear consideration constitutes a real limitation. The aim of this study is to overcome this limitation by introducing a compression/shear coupling to take into account the transverse shear. In this approach, the modelling of a low velocity impact test is performed on a sandwich composite with CFRP skins and Nomex® honeycomb. Composite skins are modeled as an elasto-plastic-damage material using a user field surbroutine (Abaqus©). The Nomex core is modeled with non-linear springs integrating a compression/shear coupling behavior. Then, the sandwich response under low speed impact is realized and compared with experimental data leading to a good correlation. [ABSTRACT FROM AUTHOR]

Abstract The paper investigated the dynamic impact response and characteristics of aluminum honeycomb filled with EPP foam (Expanded polypropylene) experimentally and numerically. It was found that the initial peak strength and mean strength of the filled honeycomb were improved significantly attributable to the interaction effect between the aluminum honeycomb and the foam, but the specific energy absorption (SEA) decreased. For the filled specimens with the same foam density, the initial peak strength, mean strength and SEA increased with the increase in impact velocity. Compared with the characteristics in the static compression test, the initial peak strength in the dynamic impact test increased, whereas the mean strength and SEA decreased. The study showed that EPP foam filling was effective to improve the impact characteristics of the bare aluminum honeycomb. Numerical simulation for the dynamic impact of filled honeycombs was also explored. It accurately reproduced the deformation process and addressed the interaction between the wall and EPP foam. By comparison of the properties in different filling types, it showed the single-cell filling was a good choice to improve the load resistance while using the least filling material. [ABSTRACT FROM AUTHOR]

Honeycomb sandwich structures have excellent energy absorption capabilities, combined with good mechanical properties and low density. These characteristics make them ideal for the transportation industry, which has a growing interest in reaching higher safety standards. The purpose of the present paper is the introduction of lightweight and more efficient crashworthy structures. Double-layer honeycomb sandwich structures were analysed and their energy absorption capabilities were evaluated by means of low-velocity impact tests. The specific energy absorption of double-layer panels was compared to single-layer honeycomb and other lightweight panels, in order to assess the effectiveness and the convenience of the introduced solution for lightweight and crashworthy devices. The impact absorption mechanism was evaluated through Computed Tomography images and visual inspection. A theoretical evaluation was applied to investigate the mono-layer impact response. The results were compared to those obtained with different boundary conditions and with a full-scale test. Contact parameters were influenced by boundary conditions since they depend on the specimens stiffness. Double-layer panels displayed a progressive collapse sequence, depending on the core arrangement and on the cell size. Honeycomb with larger cell size showed a better distribution of the impact loading which generated an almost uniform compression of the core. Such observations suggested the possibility to obtain energy absorber devices with a controlled deformation. Preliminary considerations on the existence of a size effect were drawn, since it was observed a relation among the contact parameters and the geometrical characteristics of the honeycomb and the indenter. [ABSTRACT FROM AUTHOR]

Periodic honeycombs have been used for their high strength, low weight and multifunctionality. The quasi-static and dynamic compressive responses of three types of additively manufactured AlSi10Mg honeycomb structures, specifically a single-scale honeycomb and two hierarchical honeycombs with two and three levels of hierarchy, respectively, have been investigated using experimental measurement and finite element (FE) simulations. The validated FE simulation has been employed to investigate the effects of relative density of the honeycombs and the key experimental parameters. The following failure modes of the three types of honeycombs have been observed both under quasi-static and dynamic compression: (1) the single-scale honeycomb experienced a transition of failure mechanism from local plastic buckling of walls to local damage of the parent material without buckling with the increase of the relative density of the honeycomb; (2) the hierarchical honeycombs all failed with parent material damage without buckling at different relative densities. For both quasi-static and dynamic compression, the hierarchical honeycombs offer higher peak nominal wall stresses compared to the single-scale honeycomb at low relative density of ρ ¯ = 0.19 ; the difference is diminished as relative density increases, i.e. the three types of honeycombs can achieve similar peak wall stresses when ρ ¯ ⩾ 0.26 . Numerical results have suggested the hierarchical honeycombs can offer better energy absorption capacity than the single-scale honeycomb. The two-scale and three-scale hierarchical honeycombs achieved similar peak nominal wall stresses for both quasi-static and dynamic compression, which may suggest that the structural performance under out-of-plane compression is not sensitive to the hierarchical architecture. This work indicates that the structural advantage of hierarchical honeycombs can be utilised to develop high performance lightweight structural components. [ABSTRACT FROM AUTHOR]

Sandwich structure composite is one of the most potential and effective materials to comprehensively realize microwave absorption in wide frequency range and structural lightweight function. Here, honeycomb (HC) composites were fabricated by immersion method, consisting of a carbon nanotubes/carbon black/polyurethane (CNTs/CB/PU) absorbing layer and an aramid HC core. The using CNTs and CB were both modified by improved Hummers method with a heterogeneous structural surface to enhance the dielectric properties of the carbon materials. The sandwich honeycomb (SHC) absorber showed excellent broadband absorption performance with an effective absorption bandwidth (RL<−10 dB) of 15.5 GHz. Furthermore, the compressive stress of the absorber reached 3.69 MPa. With the integrated high microwave absorption and load-bearing performance, the as-prepared SHC absorber demonstrated promising future for applications in avionics. [Display omitted] • The SHC absorber exhibited excellent absorption and comprehensive properties. • Maxwell-Garnett formula was modified by a coefficient to fit honeycomb structure. • Multilayer impedance matching was realized using Jaumamn structure design method. • The EAB of 15.5 GHz was due to heterogenous CNTs/CB and impedance matching. [ABSTRACT FROM AUTHOR]

• A class of multistable shape-reconfigurable origami honeycombs are proposed. • The honeycomb has scalability in 3D space by tilling or tessellating. • The honeycomb is lightweight and owns flexible and easy designability. • A simplified rod-hinge model can easily predict the behavior of the bistable unit. Increasing energy and space utilization efficiency is crucial for lightweight shape-reconfigurable materials/structures that require tunable functions and multiple applications. Mechanical multistable origami/kirigami structures can improve the controlling stability and energy utilization efficiency of shape-reconfiguration. However, their scalability in 3-dimensinal (3D) space by tilling or tessellating remains largely unexplored. Inspired by origami, we propose a class of novel multistable shape-reconfigurable honeycombs that are lightweight, scalable in 3D space and have flexible and easy designability. It is architected by periodically arranged truncated diamond-shaped units composed of crease-connected panels. Each unit has two stable states, i.e., the deployed state and collapsed state, which can switch from each other reversely and repeatedly. Firstly, the bistability and mechanical tunability of the unit are verified by experiments. Then a simplified rod-hinge model for investigating the mechanical behavior of the unit is established and validated numerically. Based on this simplified rod-hinge model, the effects of edge number and geometric parameters of the unit on its mechanical behaviors are studied. This novel design and its mechanical model may pave a new way for the design and analysis of lightweight shape-reconfigurable materials/structures. [Display omitted] [ABSTRACT FROM AUTHOR]

This work is a contribution to the understanding of the nonlinear shear behaviour caused by cell postbuckling in Nomex honeycomb cores. First, an experimental benchmark study was made of different designs for the shear testing of honeycomb cores. Then, several test specimens were fabricated and tested, a 3D DIC system being used to measure and record the displacements. An Artificial Neural Network (ANN) was also used to identify the onset of bucking and collapse of the cells. The influence of the overall boundary conditions of shear tests on the buckling of the cells is presented both experimentally and numerically. The reversibility and test procedure results suggest that it may be possible to allow the shear strength to be increased by up to 35% under certain conditions. [ABSTRACT FROM AUTHOR]

The yield surfaces of several honeycombs with tunable Poisson's ratio, i. e. hexagonal honeycomb, augmented hexagonal honeycomb, re-entrant honeycomb, and augmented re-entrant honeycomb, are investigated by both theoretical analysis and numerical simulations. A theoretical model is developed to predict the mechanical response of these honeycombs considering the coupling effect of the shear stress and axial stress. Explicit expressions of the yield strength are derived for the four types of honeycombs. Good consistency is obtained between the analytical solutions and the numerical simulations. The results of the study provide a new idea for designing new honeycomb materials with tunable Poisson's ratio for engineering applications in the future. [ABSTRACT FROM AUTHOR]

Biological tissues like bone, wood, and sponge possess hierarchical cellular topologies, which are lightweight and feature an excellent energy absorption capability. Here we present a system of bio-inspired hierarchical honeycomb structures based on hexagonal, Kagome, and triangular tessellations. The hierarchical designs and a reference regular honeycomb configuration are subjected to simulated in-plane impact using the nonlinear finite element code LS-DYNA. The numerical simulation results show that the triangular hierarchical honeycomb provides the best performance compared to the other two hierarchical honeycombs, and features more than twice the energy absorbed by the regular honeycomb under similar loading conditions. We also propose a parametric study correlating the microstructure parameters (hierarchical length ratio r and the number of sub cells N ) to the energy absorption capacity of these hierarchical honeycombs. The triangular hierarchical honeycomb with N  = 2 and r  = 1/8 shows the highest energy absorption capacity among all the investigated cases, and this configuration could be employed as a benchmark for the design of future safety protective systems. [ABSTRACT FROM AUTHOR]

Recently, cellular-filled structure has gained popularity due to its evident promotion in energy absorption capacity of absorber. In this study, a new pattern of composited filling structure— honeycomb cells filled with circular tubes (HFCT) has been put forward. Comprehensive experimental investigations have been conducted in terms of ten types of HFCT structures with hollow and different fillers including circular carbon fiber reinforced polymer (CFRP) tubes as well as circular Al tubes in different filling patterns. Detailed mechanical performances on energy absorption, deformation mode and interaction between inside circular CFRP filler and outside hexagonal honeycomb container were determined. The analyses show that, when undergoing axial loading, the HFCT structure not only maintains the same excellent mechanical properties with conventional hollow honeycomb core, but also gains evident promotion in energy absorption when filled in appropriate filling pattern. Obvious filling effect and matching effect were extensively discussed around the kind patterns of filling structures, which have significant influence on HFCT structure's performance. All the achievements prove that the HFCT structure can be considered as a perfect choice in aid to design of energy absorption device. [ABSTRACT FROM AUTHOR]

The vibration characteristic of the sandwich plate with a honeycomb core was investigated by experimental measurements and numerical calculation based on radial basis function (RBF). RBF method was used not only in the meshless approach but also in the post-processing of the experimental data. During the experiment, amplitude-fluctuation electronic speckle pattern interferometry was applied to access the resonant frequencies and the corresponding vibration mode shapes simultaneously. Then RBF method was used to improve the quality of patterns and reconstruct the out-of-plane vibration amplitude after fringe analysis. As for numerical calculation, the modal parameters were numerically predicted using the first-order shear deformation theory. The computation approach was based on collocation with multi-quadric radial basis function. To understand the influence of the thickness of face sheet on dynamic behaviors, three types of specimens with different thickness were tested and analyzed. Of particular interest was that the vibration modes show veering due to the thickness increment. Furthermore, the numerical predicted results were compared with the experimental measurements for the first five modes. They are in good agreement with each other for resonant frequencies, mode shapes and relative out-of-plane amplitudes. [ABSTRACT FROM AUTHOR]

The effective in-plane elastic moduli of different types of honeycomb cores with thick walls are studied using analytical and numerical approaches. Analytical equations derived in this paper take a proposed jointed rectangle into consideration. The analytical results under plane stress and plane strain conditions are also obtained. The effective in-plane elastic moduli are studied as a function of their own relative densities because of the different methods of describing the geometrical shapes of honeycomb cores. The results are quantitatively compared with the available experimental results in this paper. It indicates that the present model can better predict the elastic properties in x -direction but are less suitable in y -direction. The proposed jointed rectangle has significant effect at high relative density. Moreover, the effective in-plane modulus increases with the relative height of honeycomb cores because of the Poisson effect of the material, and the results under plane stress and plane strain conditions are the lower and upper bounds, respectively. [ABSTRACT FROM AUTHOR]