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This article reports a carbon fiber–reinforced plastic Kagome composite honeycomb sandwich structure reinforced with polymethacrylimide (PMI) foam (PKCSS). Low‐velocity impact performances on the node, rib, and two cell centers of the PKCSS were experimentally compared with those on a composite Kagome honeycomb sandwich (CKHS), and the failure mechanism of the PKCSS was investigated. The impact process was analyzed through an explicit numerical analysis using ABAQUS. A three‐dimensional Hashin failure criterion was introduced using the VUMAT subroutine. Results confirmed that the PKCSS exhibits higher impact and specific loads than the CKHS, with the maximum improvements of 69.7% and 39.5%, respectively, under 50‐J impact energy. As an uncrushable material, the PMI foam provides strong impact resistance during its plateau stage. This technology of cell filling can be used to fabricate lightweight all‐composite honeycomb sandwiches for potential use in ultrahigh engineering applications. Highlights: Cell filling is applied in an all‐composite Kagome honeycomb sandwich.The LVI performances of the PKCSS and CKHS are experimentally compared.C‐scanning is used to analyze the failure of the considered structures.The PKCSS's numerical model is established to investigate the impact process.The enhancement mechanism of the PMI foam is analyzed. [ABSTRACT FROM AUTHOR]

3D printed honeycomb structures constituted by neat polylactic acid (PLA) and conductive PLA (PLAc) with different cell sizes and thicknesses were manufactured through 3D printing technology based on material extrusion (MEX). These structures were arranged into bi‐layer honeycomb structures (BHS) for evaluation of the microwave absorbing properties at the X‐band (8.2–12.4 GHz) and Ku‐band (12.4–18 GHz) frequency ranges. The effects of cell size, sample thickness, layer thickness ratio and the nature of the top layer on the electromagnetic attenuation performance of BHS samples were investigated in terms of reflection loss (RL). The components geometric characteristics and the arrangement of the layers exerted great influence on the RL values and effective absorption bandwidth (EAB). Overall the bilayer structures with 5 mm total thickness presented the best EM response in terms of EAB and minimum RL, where the component with the larger cell size (7.7 mm), PLAc (1 mm) as the top layer and PLA (4 mm) as the bottom layer exhibited the best results with RL values of −41 dB and EAB of 9.5 GHz. The BHS system with 7.7 mm cell size was more efficient in Ku band frequency range, whereas that with 3.5 mm cell size gave better response in the X‐band frequency range. Therefore, RL values and EAB can be adjustable by modifying the building strategy of the printed parts, such as thickness of the sample, cell size and thickness distribution of the conductive and non‐conductive layers. The findings in this work show the importance of the building strategy to fabricate components with controllable BHS and improved properties for microwave absorption application. [ABSTRACT FROM AUTHOR]

To realize the one‐dimensional deformation of morphing wings, zero Poisson's ratio (ZPR) honeycomb metamaterials have become a popular research topic due to their lightweight, low in‐plane modulus, and high out‐of‐plane strength. A ZPR honeycomb metamaterial is designed and prepared from short‐cut carbon fiber‐reinforced polyetheretherketone (CF/PEEK) by a 3D printer. The mechanical properties of ZPR honeycomb metamaterials were tested to determine their tensile and bending stiffness. The results show that the metamaterial can achieve 62.3% ± 3.3% in‐plane elastic deformation after optimized structure design. At the same time, metamaterial has a certain bending resistance to keep the airfoil from normal buckling deformation. Moreover, a new test method for evaluating the cycle deformation behavior of flexible morphing wings is proposed. The high‐speed cyclic tension‐compression test showed that H22‐t0.6‐CT has the best stability, which may be related to its lower porosity (2.15% ± 0.12%). These results indicate that ZPR honeycomb metamaterials have great application prospects in the field of morphing wings. Highlights: The printed CF/PEEK wire is treated as a transversely isotropic material.ZPR honeycomb metamaterial allows for more than 50% in‐plane deformation.A new test method to evaluate the cyclic deformation behavior. [ABSTRACT FROM AUTHOR]

Modern aerostructures, including wings and fuselages, increasingly feature sandwich structures due to their high‐energy absorption, low weight, and high flexural stiffness. The face sheet of these sandwich structures are typically thin composite laminates with interior honeycombs made of Nomex or aluminum. Standard cores are structurally efficient, but their design cannot be varied throughout the structure. With additive manufacturing (AM) technology, these core geometries can be altered to meet the design requirements that are not met in standard honeycomb cores. This study used a modified aluminum honeycomb core, with increased surface area on the top and bottom, as the core material in sandwich panels. The modified honeycomb core was produced through the laser powder bed fusion method. The behavior of the modified sandwich composite panels was evaluated through three‐point bend, edgewise compression, and impact tests, and their performance was compared to that of a conventional honeycomb core sandwich panel. The three‐point bend test results indicated that the sandwich structure's ultimate shear strength improved by 12.6% with the modified honeycomb core. Additionally, the displacement at the failure of the structure increased by 11%. The edgewise compression tests showed that the ultimate edgewise compressive strength improved by 19.1% when using the modified core. The impact test results revealed that the peak force increased by 8% and the energy‐absorbing capacity of the sandwich structure increased by 20% with the use of the modified honeycomb core. [ABSTRACT FROM AUTHOR]

In this study, aluminum honeycomb cells were filled with polymethacrylimide (PMI) foam of high strength and stiffness, and carbon fiber reinforced composite (CFRC) skins were added to create a composite sandwich structure. Nine types of specimens with varying cell node spacing and foam density were constructed, and stiffness equations were derived. To compare the performances of aluminum honeycomb and PMI foam sandwich structures, their compressive responses were examined using edgewise and flatwise compression tests. Moreover, the failure was analyzed using finite element methods (FEM). Analytical and numerical models were used to investigate the size effects of rib width, rib angle, and node spacing. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) are becoming promising candidates for energy storage devices due to the low cost, abundant reserves, and excellent electrochemical performance. As the most important unit, layered cathodes attract much attention, where honeycomb‐layered‐oxides (HLOs) manifest outstanding structural stability, high redox potential, and long‐life electrochemistry. Here, recent progress on HLOs as well as Na3Ni2SbO6 and Na3Ni2BiO6 as two representative materials are introduced, and the crystal and electronic structure, electrochemical performance, and modification strategies are summarized. The advanced high nickel HLOs are highlighted toward development of state‐of‐the‐art sodium‐ion batteries. This review would deepen the understanding of superstructure in layered oxides, as well as structure–property relationship, and inspire more interest in high output voltage, long lifespan sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA)—based honeycomb samples with different cell sizes and thickness were prepared using the fused filament fabrication (FFF) 3D printing technology and used to build sandwiched multilayer structures consisted of the honeycomb as the core component and poly(vinylidene fluoride) (PVDF) and/or PVDF/carbon nanotube (CNT) nanocomposites as top and bottom layers. The effect of the honeycomb design (cell size and thickness) and the presence and nature of the impedance matching layer on the microwave absorbing properties of the corresponding structures was investigated in the X‐band (8.2–12.4 GHz) and Ku‐band (12.4–18 GHz). For the systems without matching layer or with neat PVDF film as the matching layer, the honeycomb with larger thickness (5 mm) and larger cell size resulted in better electromagnetic wave attenuation but narrow frequency bandwidth with RL below −10 dB. The best combination minimum RL value (−18 to −14 dB) and broad frequency bandwidth with attenuation higher than 90% (around 8 GHz) was achieved with honeycomb of 2 mm thickness sandwiched by PVDF/CNT05 as the matching layer and bottom layer constituted by PVDF/CNT1 film, regardless the cell size of the honeycomb. These results indicate the PLA honeycomb as promising candidate as component for multilayer microwave absorbing materials and open new possibilities of applications of FFF technology for designing flexible, lightweight, and low‐cost materials to be used in both civil and military industries. [ABSTRACT FROM AUTHOR]

For a policy of 100% renewable energy, most renewable‐energy research is aimed at decarbonization; particular emphasis is being placed on increasing the portion of electricity generated by photovoltaics (PVs). As the application fields of PVs broadens from PV power plants and rooftop to various urban environments, achieving high energy yields requires expansion beyond current PV module structures. To satisfy these demands, honeycomb‐structured PV modules with incorporated mechanical metamaterials are proposed, to overcome the aforementioned problems associated with the limited mechanical properties of PVs, and to advance the development of 3D PV modules with enhanced energy yield. The honeycomb structures provide 28% greater power compared with flat cells by utilizing extra reflected or scattered light inside a 3D tetrahedron structure. For mechanical robustness, the 3D concave tetrahedron units are supported by a 3D‐structured mechanical metamaterial that exhibits a negative Poisson's ratio and is arranged in a 3D pattern. [ABSTRACT FROM AUTHOR]

In this study, a three‐dimensional bandpass frequency selective surface (FSS) with a new fabrication technology is proposed and designed based on slotlines. The proposed FSS consists of silver paste circuits printed on aramid paper, and is vertically and horizontally arranged to form a periodic array in honeycomb structure. To better understand the design principle of the proposed FSS, the equivalent circuit model (ECM), single‐polarized structure, and dual‐polarized structure are presented and analyzed, respectively. The proposed FSS exhibits a passband at 4.1 GHz with a fractional bandwidth of 71.5% at x‐polarization and 66.2% at y‐polarization with reflectivity less than −10 dB. Moreover, the reflection and transmission coefficients have relative stable properties up to 30° for the oblique incidence. Then, the proposed structure is fabricated and measured to verify the design strategies. The measured and simulated results have reasonable agreement under a large variation of incident angles. [ABSTRACT FROM AUTHOR]

A detailed step‐by‐step fabrication procedural document of thin‐walled aluminum honeycomb sandwich composite structures, panels, and specimens using vacuum assisted resin infusion process was delivered in this paper. By and large, honeycomb sandwich structures are made by keeping the honeycomb core in between two face sheets, which are glued with the help of adhesives. In the present fabrication process, aluminum honeycomb core was glued in between the carbon fabric reinforced epoxy composite face sheets through vacuum assisted resin infusion technique. The present paper is aimed at fabricating two configurations of honeycomb sandwich composite panels namely, without considering any filler material inside the honeycomb cell, with considering the filler material inside the honeycomb cell. Plastic pellets made up of poly carbonate were considered as filler material for stiffening the aluminum honeycomb sandwich composite panels. [ABSTRACT FROM AUTHOR]

Efficient, facile, lightweight, and low‐frequency sound‐absorbing materials are in great demand for noise elimination and insulation. However, the applications of some candidate materials are limited by their large space, mass, or unsatisfactory sound‐absorption performance especially in low‐frequency sound‐wave region. Graphene network structure can be promising sound‐absorbing materials due to ultrahigh porosity, ultralight weight, and excellent intrinsic properties. Conventionally, allowing for poor mechanical strength, such graphene materials are needed to be reinforced by polymer, metal, or ceramic. Here, a novel strategy of graphene network reinforced by honeycomb structure is proposed, in which graphene is used as a sound absorber, and meanwhile flexible aramid honeycomb is introduced to enhance the graphene composite. In this work, the compressive strength of graphene network structure is improved 1000 times by the flexible aramid honeycomb, and meanwhile the density is only increased 2.5 times. Moreover, the sound‐absorption coefficient of graphene network is about 0.9 at 700 Hz for the thickness of 30 mm. Further, the sound‐absorption coefficient is above 0.9 in the frequency range of >1000 Hz. Therefore, the graphene composite is expected to be saving space and weight for the engineering design of sound absorbers in low‐frequency regions. [ABSTRACT FROM AUTHOR]

Lightweight sandwich panels have been used in various industry sectors due to their unique properties as well as a high ratio of stiffness‐to‐weight and energy absorption. Three‐dimensional (3D) printing process provides a unique opportunity to fabricate highly complex shapes of sandwich panels and also the application of smart materials, such as shape memory polymers, can create unique functionality for the 3D printed sandwich structure so that they can change their shape in response to external stimuli and give a new dimension to the printing process called four‐dimensional (4D) printing. Polylactic acid is a biodegradable and compostable polymer with a good shape memory effect that can be printed easily with an inexpensive fused deposition modeling. This study investigated the effect of printing and activation parameters on the functionality, in particular shape recovery, of the deformed sandwich structure with honeycomb out‐of‐plane tailored core. The input parameters were the activation temperature, the nozzle temperature, and the printing velocity. The results showed that the optimum recovery ratio can be achieved using a higher activations and nozzle temperatures and lower printing speed. [ABSTRACT FROM AUTHOR]

Crashworthiness design and development of lightweight structures have become important engineering challenges because of the high standards of energy consumption and safety regulations. Within this context, the use of honeycomb structures as crush absorber is continuously growing in automotive and aircraft industries, once honeycombs are known for their high strength‐to‐weight ratio and excellent energy absorbing capacity. Thus, this paper presents a method that combines radial basis functions with expected improvement to optimize the specific energy absorption of honeycomb cellular materials, while the peak crush force is constrained at low levels for safety reasons. Honeycomb's cell size, cell shape and thickness are the design variables. Concerning the cell shape, the results indicate the hexagonal configuration has a higher out‐of‐plane performance compared to auxetic and rectangular cells in terms of energy absorption capacity. Lastly, a multi‐objective optimization using only the radial basis function predictor (without sequential sampling) is carried out to seek simultaneously for optimal solutions with minimum peak force and maximum specific energy absorption. [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]

This paper proposes a novel type of metallic damper, named Honeycomb Structural Fuse (HSF), a modified version of the previously developed Welded Wide Flange Fuse (WWFF). Based on the commonly available welded wide flange section, honeycomb‐shape perforations were laser cut on web. The HSF is designed to dissipate earthquake energy through plastic deformation of the web in shear, while the flanges remain elastic. To investigate the seismic behaviour of HSF, a total of 9 specimens with different honeycomb cell wall aspect ratios (cell wall thickness to cell wall centre length) and honeycomb cell combinations (number of cell rows and columns) were manufactured and tested to examine the influence of different parameters on its performance including force‐drift relationship, working mechanism and buckling modes etc., are summarized. The experiment shows that the newly proposed HSF exhibits stable energy dissipation capability, which can be used as an efficient metallic damper for seismic applications. [ABSTRACT FROM AUTHOR]

The mechanical and structural response of powder metallurgical square-celled honeycomb structures to quasi-static and dynamic impact loads are described. By constructing the cellular lattice with a novel metal matrix composite material based on a metastable high-alloyed austenitic TRIP-steel particle-reinforced by magnesia partially stabilized zirconia (Mg-PSZ), high specific yield and ultimate collapse strengths as well as a high ductility and an enhanced specific energy absorption were gained. In order to prove the temperature sensitivity of the honeycomb structures, a selected low-reinforced composite condition was investigated in a pre-series of quasi-static compression tests at temperatures in the range between −190 and 150°C. The present study shows that the deformation mechanisms of the TRIP-matrix composite honeycomb structures can be classified with respect to strain rate and deformation temperature, including the failure characteristics and the strain-induced α′-martensite transformation in the austenitic steel matrices ensuring the TRIP effect. The evolution of the α′-martensite phase content in the central crush zone of the TRIP steel and TRIP-Matrix Composite honeycombs is demonstrated based on the results of magnetic balance measurements. [ABSTRACT FROM AUTHOR]

The procedure allowing single-step formation of microscaled thermostable polymer honeycomb patterns is reported. Polymer substrates soluble in chlorinated solvents were pulled from the solvents before their final dissolution and placed into a humid atmosphere. Honeycomb patterns were deposited by this method on polyetherimide, polysulfone (PSF), and polyethersulfone (PESF) substrates. PSF and PESF substrates demonstrated reversibly switchable wetting under UV irradiation/heating cycles strengthened by the Cassie-Baxter wetting regime. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The transverse shear modulus of in-plane negative Poisson’s ratio honeycombs is determined using numerical simulations. General honeycombs have theoretical upper and lower bounds of transverse shear moduli. The actual transverse shear modulus is an intermediate value, depending on the relative density and the gauge thickness ratio. The difference between upper and lower bounds is particularly significant for negative Poisson’s ratio honeycombs. Finite element simulations confirm the theoretical trend, and show gauge ratio dependence different from that envisaged in the literature for conventional honeycombs. A modified approximate formula is thus proposed to predict the actual transverse shear modulus for honeycombs having in-plane negative Poisson’s ratio values. [ABSTRACT FROM AUTHOR]

Cordierite honeycomb ceramics are sintered under a range of sintering atmosphere and temperature conditions. The linear thermal expansion coefficient (CTE) is measured along the extrusion direction. The samples sintered in an enclosed crucible have a much lower CTE than those sintered in open air. The CTE decreases with increasing sintering temperature up to 1450 °C. The polymorphic phases, texture, amorphous phase, impurity crystals, and porosity are analyzed using scanning electron microscopy, HR‐TEM, porosimeter, and Rietveld refinement method. The sintered samples consist of two polymorphic phases: indialite (hexagonal symmetry) and cordierite (orthorhombic symmetry). Both the volume % of the cordierite phase and the crystal texture increase with increasing sintering temperature. The orthorhombic distortion of cordierite from the hexagonal lattice (indialite) increases with increasing sintering temperature. The characteristic six‐membered ring of the (Si,Al)‐O4 tetrahedra in the cordierite structure shows substantial changes in the bond length due to Al‐Si ordering. Amorphous phase and impurity crystal phases such as silimanite and spinel remain at temperatures as high as 1450 °C. The effect of the polymorphic phases, the degree of texture, amorphous phase, impurity crystal phases, and the orthorhombic distortion is discussed in relation to the CTE characteristics of honeycomb. The sintered honeycomb consists of two polymorphic phases, indialite (hexagonal symmetry) and cordierite (orthorhombic symmetry). The volume % of cordierite phase and the crystal texture increase with increasing sintering temperature. The thermal expansion coefficient (CTE) reduces with the sintering temperature. The orthorhombic distortion originates from Al‐Si ordering. Amorphous and silimanite phases are ascribed to higher CTEs of the samples sintered in open air. [ABSTRACT FROM AUTHOR]

This article provides a comprehensive review of recent research efforts on the development and characterization of sandwich structures with corrugated, honeycomb, and foam cores. The topics discussed in this review article include aspects of core‐face bonding and reinforcement, enhancement of core mechanical properties and panel performance (including the role of structural hierarchy), and multifunctional advantages offered by different core constructions. In addition, the review discusses potential applications, including in morphing wing design, impact resistance, and ultralightweight applications. Future research directions are discussed. This article provides a comprehensive review of the current state of the art of sandwich structures including corrugated sandwich structures, honeycomb sandwich structures, and foam sandwich structures. The topics mainly consist of core‐face bonding and reinforcement, enhancement of core mechanical properties and panel performance, and tailoring properties for each core type. [ABSTRACT FROM AUTHOR]