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This study investigates free vibration analysis of a microplate featuring a honeycomb (HC) core and incorporates two nanocomposite piezoelectric (NP) layers. Carbon nanotubes (CNTs) are hired to enhance the electro-mechanical performance of the piezoelectric patches, which are subjected to an externally applied electric voltage. All layers are tightly bonded together and are supported by an elastic substrate according to the Pasternak model, capable of withstanding both normal and shear loads. To establish the kinematic relations, a trigonometric plate theory is employed. The governing equations of motion are deduced through the application of Hamilton's principle and variational technique. The modified strain gradient theory, which includes three material length-scale parameters (MLSPs), is used to account for the scale effect. An analytical approach based on Fourier series functions is employed to solve the differential equations of motion. Subsequently, the impact of various factors, such as the geometrical characteristics of the HC core, distribution patterns of CNTs, and other significant parameters, on the normalized frequencies of the model is assessed after validating the accuracy of the results. The outcomes of this research have the potential to facilitate the advancement and production of lightweight and intelligent structures and devices, ultimately enhancing their efficiency. [ABSTRACT FROM AUTHOR]

Highlights This paper investigates a honeycomb sandwich structure that draws inspiration from the craft of origami. A specific folding pattern was applied to the honeycomb to create the origami‐based re‐entrant honeycomb (ORH), aimed at improving the energy absorption properties of the sandwich structure. The study on the energy absorption properties of structures under low‐velocity impact (LVI) utilized both experimental and numerical approaches. The energy absorption properties of the sandwich structure were examined by conducting LVI tests with different impact energy and then compared to the mechanical properties of the traditional re‐entrant honeycomb sandwich structures (TRHSS). Additionally, a refined finite element model has been established and its accuracy verified. Numerical studies were conducted to explore the effects of structural parameters on the energy absorption properties of ORH sandwich structure (ORHSS). The results show that the ORHSS exhibited a significant reduction in peak force when subjected to LVI, in contrast to the TRHSS. Furthermore, the ORHSS exhibit significant efficiency in energy absorption. Enhancing the wall thickness t$$ t $$ or folding angle V/H$$ V/H $$ can significantly improve the energy absorption properties of the ORHSS, thereby boosting the honeycomb's contribution to this process. This optimization results in an improved absorptive effect of the structure. The findings offer new recommendations for developing lightweight absorbent materials with potential applications across various industries. A novel composite sandwich structure serves as an efficient device for absorbing energy. This sandwich structure exhibits excellent cushioning and energy absorption capabilities. Changing geometric parameters can enhance the impact performance of the structure. A larger folding angle V/H$$ V/H $$ makes the core more prone to deformation. The greater the forward length V$$ V $$ of the ORH, the lower specific energy absorption (SEA) of the ORHSS. [ABSTRACT FROM AUTHOR]

This paper proposed a composite sandwich structure containing multilayer honeycombs, and a multi-objective optimization model containing its load-bearing and wave-absorbing properties, which were correlated with the geometric parameters of the honeycomb, was developed. The critical elastic buckling load was performed as an indicator to characterize the load-bearing capacity, and the bandwidth of the sandwich was employed as an indicator to characterize the wave-absorbing characteristics. This multi-objective optimization model was optimized based on JAYA algorithm and the results showed that the optimized structure had a significant improvement in both load-bearing and wave-absorbing capacities compared to the original structure. [ABSTRACT FROM AUTHOR]

In this study, the effects of different silicon carbide (SiC) particle sizes on the viscosity and curing behavior of alumina (Al 2 O 3) ceramic suspensions were thoroughly investigated. The findings revealed that increasing the size of SiC particles led to a noticeable decrease in the viscosity of the suspension. The Al 2 O 3 ceramic suspension with 0.6 μm SiC powder demonstrated a shallower cure depth and wider excess width compared to the suspension with 1.0 μm SiC powder. Sintering tests demonstrated that the properties of the SiC–Al 2 O 3 ceramics improved at higher sintering temperatures. Moreover, a high-performance honeycomb ceramic was successfully designed and fabricated with a porosity and compressive strength of 30.8 % and 188 MPa, respectively. Finally, the SiC–Al 2 O 3 honeycomb ceramics were effectively applied in heat insulation and oil-water separation applications, demonstrating their remarkable capabilities. [ABSTRACT FROM AUTHOR]

With the continuous innovation of UAV technology, composite honeycomb sandwich structures are used more and more in the fuselage structure of UAVs, and their anti-high-speed fragment impact performance has become a concern. In order to study the influence of fragments on the damage degree of composite honeycomb structures and analyze the damage difference of different initial velocity fragments on different composite honeycomb structures, based on the numerical simulation results of high-speed impact, the energy absorption characteristics of different honeycomb sandwich structures are analyzed, and the honeycomb structure with better energy absorption is selected for 24 impact experiments. The velocity range of fragment impact is 141–368 m/s. The typical damage of the upper core layer and the lower core layer in each structure is analyzed, and the energy absorption theory is used to compare the conditions of each group. The results show that ST-3-3 has the best energy absorption characteristics. Under different velocity impacts, the energy absorption per unit volume of the ST-3-3 structure reaches 521.6~659.6 × 103 J/m3, which is about 30.6% higher than that of the same design structure. The four groups of composite honeycomb sandwich structures designed in the experiment have obvious deformation in the process of impact, except that the deformation of the bottom skin of the ST-6-6-1 structure is not obvious, and the deformation of the other three groups is more obvious with the increase in structural resistance. This research shows that the reasonable arrangement of the structure and material of the composite honeycomb sandwich can better cope with the impact of high-speed fragments and reduce the damage to the structure. [ABSTRACT FROM AUTHOR]

Nomex honeycomb composites are widely recognized for their advanced structural applications in the aerospace, automotive and defense industries. These materials are distinguished by exceptional characteristics such as thin cell walls and a hexagonal structure, as well as layers made of phenolic resins and aramid fibers. However, complex machining and the maintenance of high quality at a large scale presents considerable challenges. This study provides a comprehensive review of the literature on the processing of Nomex composites, highlighting the design challenges related to processing technologies, the impact of conventional and ultrasonic processing methods, and the associated mechanical properties and microstructural topographies. Moreover, it reviews research advances in machining techniques, current challenges, and future perspectives, thereby providing valuable guidance to ensure the optimal cutting of Nomex honeycomb composite structures (NHCs). [ABSTRACT FROM AUTHOR]

Both the nacre‐like bionic microstructure and the spiral laminated bionic configuration exhibit superior damage‐tolerance characteristics. On the basis of this observation, the design concept of the bionic helical‐interlayer configuration is innovatively integrated into the design of a bionic nacre‐like honeycomb structure. By systematically studying different spiral angles of honeycomb's interlayer stacking forms, their influence on the structural performance is deeply discussed with four‐point bending tests. Mechanical samples are carefully prepared using short carbon fiber reinforced polyamide composites (i.e., PA6‐CF) through conventional fused filament fabrication (FFF) 3D printing technology, where the accuracy and reliability of the designed bio‐inspired samples are ensured. The experimental results reveal significant improvements in bending strength and elastic modulus across various bionic nacre‐like honeycomb spiral structures compared to uniformly overlap configurations. In particular, the SH‐7.5 sample shows a remarkable 35.47% increase in bending strength and a 65.10% increase in elastic modulus over the SH‐11.25 sample. SEM‐based microstructural analyses are carried out to further explore the fracture mode of the carbon fibers, implied the helical configuration adopted in the nacre‐like honeycomb structure enhances the flexural resistant ability of the PA6‐CF composites. The findings above bear important guiding significance and reference value for the design of lightweight and high damage‐tolerance composite structures. Highlights: A novel bio‐inspired structure is implemented to improve the mechanical performance of fused filament fabricated polyamide composites, where the bionic spiral helical configuration is integrated into high‐fracture‐resistance nacre‐like honeycomb structures.Mechanical testing results indicate that a helix angle under 10° results in a significant improvement in the structural performance of flexural strength.Microstructural analysis reveals that the helical configuration enhances the load‐bearing functionality of reinforcing carbon fibers in the printed polyamide composites.FFF 3D printing enables further implementation of the proposed bio‐inspired novel structure for lightweight and damage‐tolerant composite applications with high customization demands. [ABSTRACT FROM AUTHOR]

Highlights The mechanical properties of the carbon fiber and glass fiber composite honeycomb sandwich structure were studied through compression experiments. The influence of different aluminum honeycomb edge lengths, upper and lower panel thickness, aluminum honeycomb thickness, and loading speed on the compression failure load of carbon fiber composite laminates sandwich structure is analyzed. The influence of different aluminum honeycomb edge lengths and thicknesses on the compression failure load of glass fiber composite laminates sandwich structure was studied. The results show that the thickness of the panel has a significant effect on the failure load of the carbon fiber composite laminate sandwich structure, and the loading speed has a significant effect on the failure load of the carbon fiber composite laminate sandwich structure. The greater the loading speed, the greater the value of the failure load. The edge length and thickness of the aluminum honeycomb have a certain effect on the damage load of the carbon fiber composite laminates sandwich structure, but the influence on the mechanical properties of the glass fiber composite laminates sandwich structure is much greater. The compression performance of composite sandwich structures was experimentally studied. The influence of composite panel thickness was studied. The influence of aluminum honeycomb edge length and thickness was studied. The influence of loading speed was studied. [ABSTRACT FROM AUTHOR]

A novel composite tandem sandwich structure made of aramid fabric and aramid honeycomb, impregnated in a matrix of epoxy resin combined with poly (vinyl butyral), PVB, is proposed. The composite was additionally reinforced with a small concentration of titanium diboride nanoparticles, TiB2, to study its effect on impact resistance. Sandwich composite samples were fabricated by impregnating the aramid fabrics and honeycomb in subsequent layers with the system epoxy/PVB/TiB2. Their mechanical behavior was examined through three-point bending test, Charpy impact test, and compressive test. The chemical reaction between PVB and epoxy resin, and chemical inertness between the nanoparticles and the other constituents were confirmed by FTIR analysis. The flexural strength and stiffness increased by 27.6% and 62.5%, respectively, in the presence of TiB2 reinforcement. Impact tests showed increase of 104% in impact toughness in the case of samples with TiB2. Nano TiB2 did not increase compressive strength of the proposed sandwich structure, but it improved its stiffness and reduced the permanent deformation. The achieved improvements in mechanical resistance make this new composite structure a promising candidate for automotive, airspace, naval, civil engineering, sports equipment industry, and for use in defense technologies. [ABSTRACT FROM AUTHOR]

Honeycomb (HC) has been used in energy absorption applications due to its high stiffness and low density. Metallic HC are used for energy absorption applications, however, these metallic structures can be challenging to manufacture if complex geometric features designed to improve energy absorption are used, which motivates the use of additive manufacturing (AM). Metal AM methods include powder bed fusion (PBF) and direct energy deposition (DED). In addition to capital equipment cost, these processes possess challenges that include a required inert environment, powder handling, final part porosity, residual stresses, and nonuniform surface finish. These concerns can be alleviated through the use of polymer AM, however, polymeric parts exhibit brittle failure and have a lower stiffness than metallic HC structures. In this study, a low-cost 3D polymer printing method, stereolithography (SLA), is combined with a conventional electroplating process to fabricate a metal-plastic composite HC structure with energy absorption capability much greater than of a plastic HC structures of the same nominal volume. SLA parts have a smooth surface, so that the surface finish is at least as uniform after electroplating as the SLA part. The energy absorption characteristics of the electroplated HC is studied to determine how these energy absorbing materials can be manufactured at reduced cost. Our study confirms that the metal-plastic composite HC increases both the crush strain range and the mean crush stress of these samples, resulting in metal-plastic composite HC structures with substantially increased energy absorption. This study also examines how buckling initiators (BIs), or diamond shaped holes located at 50, 75, and 100% of the height of the hexagonal cell vertices, can influence energy absorption performance. This study shows that it is feasible to fabricate electroplated HCs, using an SLA preform, to achieve a substantial increase in energy absorption over using SLA alone. [ABSTRACT FROM AUTHOR]

The expansive utility of polymeric 3D-printing technologies and demand for high- performance lightweight structures has prompted the emergence of various carbon-reinforced polymer composite filaments. However, detailed characterization of the processing–microstructure–property relationships of these materials is still required to realize their full potential. In this study, acrylonitrile butadiene styrene (ABS) and two carbon-reinforced ABS variants, with either carbon nanotubes (CNT) or 5 wt.% chopped carbon fiber (CF), were designed in a bio-inspired honeycomb geometry. These structures were manufactured by fused filament fabrication (FFF) and investigated across a range of layer thicknesses and hexagonal (hex) sizes. Microscopy of material cross-sections was conducted to evaluate the relationship between print parameters and porosity. Analyses determined a trend of reduced porosity with lower print-layer heights and hex sizes compared to larger print-layer heights and hex sizes. Mechanical properties were evaluated through compression testing, with ABS specimens achieving higher compressive yield strength, while CNT-ABS achieved higher ultimate compressive strength due to the reduction in porosity and subsequent strengthening. A trend of decreasing strength with increasing hex size across all materials was supported by the negative correlation between porosity and increasing print-layer height and hex size. We elucidated the potential of honeycomb ABS, CNT-ABS, and ABS-5wt.% CF polymer composites for novel 3D-printed structures. These studies were supported by the development of a predictive classification and regression supervised machine learning model with 0.92 accuracy and a 0.96 coefficient of determination to help inform and guide design for targeted performance. [ABSTRACT FROM AUTHOR]

Honeycomb is regarded as a valuable structural material because of its high strength, shear stiffness, high impact strength, low weight, high crushing stress, and nearly constant force to crush. It is a cellular solid, well-known as a core in creating sandwich structures for use in structural composites. Honeycombs are often utilized in the aircraft sector as the core of sandwich panels and in the automotive industry as effective impact attenuators because of their superior mechanical performance. The hollow spaces in the honeycomb structure not only reduce weight but also ensure the required strength, provided they are designed correctly. In lightweight application areas, because they offer structural integrity, 3-D woven honeycomb composites have a bright future and possess the potential to replace aluminum and other metal alloys. This issue of Textile Progress focuses on the manufacturing of 3-D woven honeycomb fabrics, their mechanical characterization, application areas, different ways of weaving honeycomb cells, and some innovations related to honeycomb-like auxetic and 3-D printed honeycomb structures. [ABSTRACT FROM AUTHOR]

In order to improve the impact resistance of sandwich panels under low-velocity impact, the lotus leaf vein is selected as a biological prototype to design a bio-inspired honeycomb (BIH) sandwich panel. ABAQUS is used to establish and effectively verify the finite element (FE) model of the BIH sandwich panel. To systematically compare and study the mechanical properties of BIH and conventional hexagonal honeycomb sandwich panels under low-velocity impact, the maximum displacement of face-sheets, the deformation mode, the plastic energy consumption and the dynamic response curve of the impact end are presented. At the same time, the performance differences between them are revealed from the perspective of an energy absorption mechanism. Furthermore, the influence of the circumscribed circle diameter ratio of the BIH trunk to branch (γ), the thickness ratio of the trunk to branch (K) and the impact angle (θ) on impact resistance is studied. Finally, the BIH sandwich panel is further optimized by using the response surface method. It can be concluded that, compared to conventional hexagonal honeycomb sandwich panels, the addition of walls in the BIH sandwich panel reduces the maximum deformation of the rear face-sheet by 10.29% and increases plastic energy consumption by 8.02%. Properly adjusting the structural parameters can effectively enhance the impact resistance of the BIH sandwich panel. [ABSTRACT FROM AUTHOR]

Honeycomb cores made of phenol resin impregnated paper are widely used in sandwich structures of aircraft. Owing to the rather weak core material, this kind of sandwich is prone to a range of damages as a result of impact loading which may accidentally occur during operation. When employed in aircraft these structures have to be damage tolerant. This means barely visible damages have to be considered in the structural design process. In the standard design process for damage tolerant aircraft structures especially the effect of impacts has to be considered but is mostly investigated on unloaded sandwich components. However, aircraft structures are not completely stress free, even when the aircraft is in parking position. At least the structural weight will cause a permanent static preload. In the literature there are only few investigations dealing with the impact behaviour of preloaded honeycomb sandwich structures. In general, studies on composite structures have shown that tension preloads lead to higher structural impact resistance, while prestressing in compression reduces mechanical properties such as impact strength and stiffness of the structure. For this reason, a compression preload is considered as the more critical load case. In order to evaluate the effect of static compression preloads an experimental study on five different honeycomb sandwich configurations was conducted. The experimental investigations showed that even low preloads cause a higher structural damage area, which results in a lower residual strength of the structure. The results indicated that it is recommendable to consider structural compression preloads in the aircraft structural design process. [ABSTRACT FROM AUTHOR]

The deployable reflector antenna based on the synthetic aperture radar is a satellite component that consists of a unit structure in the form of a folded reflector. During the launch process, this satellite antenna is in the stowed condition to improve storage efficiency. It is then deployed to perform the space mission in the on-orbit condition. Due to these structural characteristics of the deployable reflector antenna, the reflector is possible to be loaded in the limited volume of the launch vehicle with the reduced size. Additionally, because the deployable reflector antenna is made by the lightweight material of the carbon fiber reinforced polymer and honeycomb core, it can reduce the launching cost and improve the revisit interval. In this paper, the conceptual design of the main reflector of the deployable reflector antenna was conducted. The main reflector was designed as the honeycomb sandwich composite structure. To design the main reflector, the stacking sequence of the composite material and honeycomb core was investigated to maximize the structural stiffness and minimize the antenna's mass. Subsequently, finite element analyses including modal, quasi-static, structural–thermal coupling, and transient response were performed to numerically evaluate the structural performance of the lightweight composite reflector antenna. [ABSTRACT FROM AUTHOR]

The response of sandwich structures under the synergistic effects of blast wave and fragments is a topic of interest for researchers and designers. Thus, the performance of a sandwich structure used for enhancing the protection of a target structure is numerically investigated because it may experience such complex loading conditions resulting from combined blast and fragment impact. A conventional sandwich structure modelled using aluminium alloy resists a bare blast load imposed on it. Analysis, however, reveals that fragments penetrate through the front facesheet of a conventional sandwich structure, indicating a lower resistance of the front facesheet to combined blast and fragment effects. Thus, the behaviour of conventional aluminium honeycomb sandwich structures is compared with enhanced sandwich configurations consisting of a front facesheet covered with multilayer lightweight composite Kevlar fabric material. The Kevlar fabric arrests the maximum number of fragments, and reduces their momentum, thereby reducing the damage level in the sandwich structure. The effect of the charge weight and shape of the fragments on the damage modes of the sandwich structure is also assessed. With the increase in charge weight, the momentum of the fragments is found to increase, and these penetrate the back facesheet of the sandwich structure. [ABSTRACT FROM AUTHOR]

Nomex honeycomb composite (NHC) cores have seen significant growth in recent years, particularly in the aeronautics, aerospace, naval and automotive industries. This development presents significant challenges in terms of improving machining quality, requiring the use of specialized cutting tools and favorable cutting techniques. In this context, experimental studies have been carried out to highlight the characteristics of the milling of NHCs by rotary ultrasonic machining (RUM). However, the rapid motion of the cutting tool and the inaccessibility of the tool/part interface prevent the visualization of the chip formation process. For this purpose, a three-dimensional numerical model for milling the NHC structure using RUM technology was developed by Abaqus Explicit software. On the basis of this model, the components of the cutting force, the quality of the machined surface and the chip accumulation in front of the cutting tool were analyzed. The numerical results agree with the experimental tests, demonstrating that the use of RUM technology effectively reduces the cutting force components. An in-depth analysis of the influence of feed component Fy on the quality of the generated surface was carried out, revealing that the surface quality improved with low values of feed component Fy. Furthermore, the impact of ultrasonic vibrations on the accumulation of chips in front of the cutting tool is particularly optimized, in particular for large amplitudes. [ABSTRACT FROM AUTHOR]

Honeycomb composite with excellent mechanical–physical properties had attracted extensive attention. To achieve outstanding sound insulation while maximizing the high‐performance of honeycomb composite, this article reported a honeycomb composite structure filled with glass fiber (HFG) based on a paper‐making process and the corresponding sandwich structure. Pulping parameters, mechanical property, air permeability and sound insulation of HFG were analyzed. The results showed that the hanging index and settling height of glass fiber slurry were inversely proportional to the beating degree, which was beneficial for reducing the coefficient of variation (CV) of HFG with value of 4%–6%. The maximum improvement in tensile strength and bursting strength of HFG were 70% and 53%, respectively. In addition, sound transmission loss (STL) of HFG was proportional to cell size, density, filling amount and thickness of the honeycomb. Compared to HFG, sandwich structure consisting of HFG and glass fiber/hot melt fiber panels effectively improved STL, especially at low‐mid frequencies. It was also found that designing holes on the surface of sandwich structure could further improve STL in certain frequency bands. The structure offered a lightweight and high‐performance response for construction, transportation and infrastructure. Highlights: This article designs a new type of honeycomb filled glass fiber via paper‐making process, aiming to improve the comprehensive performance of honeycomb.By the design of embedded structure, the maximum improvement in tensile strength and bursting strength of honeycomb were 70% and 53%, respectively.By designing perforated, embedded and laminated structures, sound insulation has been improved, while reducing material quality. [ABSTRACT FROM AUTHOR]

In this study, an investigation is presented on the effects of the honeycomb core splice gaps on the performance of advanced composite sandwich structures consisting of aluminum honeycomb core and carbon-fiber/epoxy facesheets. The experimental and numerical investigation explores the effects of core thickness, facesheet thickness, splice gap width, and the presence of core splice adhesive on the structural response of the composite sandwich structure. The specimens fabricated with the splices exposed to primarily bending and shear to understand further how the core splice interacts with the overall structural response under such loading conditions. In addition, 3D finite element models investigated the failure modes in the specimens by examining the strain fields for core-spliced sections of the sandwich structure under the experimentally observed loading conditions. Various failure modes are observed in the experiments ranging from core shear failure, facesheet debonding, or fracture depending on the location of the core splice, core, and the facesheet properties. The results illustrate the importance of proper detailing and analysis of core splices in composite structures made from sandwich designs. [ABSTRACT FROM AUTHOR]

There is a growing demand to comprehend the orthotropic properties of composite sandwich structures. Indentation stress is often experienced on the surfaces of sandwich beams, particularly during maintenance procedures. The objective of the present investigation is to evaluate the performance of these structures under such circumstances. The mechanical behavior of the composite sandwich structures is assessed by analyzing the results of edgewise compression and flexure tests conducted after indentation. The experiments encompass variations in carbon composite face thicknesses, core types, and indentation depths. The overall outcomes highlight a notable effect of indentation, particularly in the case of foam-core sandwiches, which exhibit lower elasticity compared to honeycomb-core sandwiches. Interestingly, the specific properties of both foam and honeycomb core beams, relative to their weight ratios, are found to be comparable. Furthermore, the results demonstrate that sandwich beams with reduced face material display lower stiffness but higher flexibility, enabling them to greater resistance to damage. [ABSTRACT FROM AUTHOR]

Auxetic re-entrant honeycomb (AREH) structures, consisting of a single soft or tough material, have long faced the challenge of balancing stiffness and rebound resilience. To achieve this balance, dual-material printing technology is employed to enhance shock absorption by combining layers of soft and tough materials. Additionally, a novel structure called the curved re-entrant honeycomb (CREH) structure has been introduced to improve stiffness. The selected materials for processing the composite structures of AREH and CREH are the rigid thermoplastic polymer polylactic acid (PLA) and the soft rubber material thermoplastic polyurethane (TPU), created utilizing fused deposition modeling (FDM) 3D printing technology. The influence of the material system and structure type on stress distribution and mechanical response was subsequently investigated. The results revealed that the dual-material printed structures demonstrated later entry into the densification phase compared to the single-material printed structures. Moreover, the soft material in the interlayer offered exceptional protection, thereby ensuring the overall integrity of the structure. These findings effectively serve as a reference for the design of dual-material re-entrant honeycombs. [ABSTRACT FROM AUTHOR]

Background: High strength-to-weight ratio and high stiffness-to-weight ratio are the potential benefits of syntactic foam core sandwich composite for structural applications. However, these composite structures may encounter problems in correlation with vibration because of poor quality-factor and leads to poor structural performance. Purpose: Present investigation focused on improving the structural performance of syntactic-foam core sandwich composites by enhancing their quality-factor. This is achieved by integrating stiffening grid honeycomb structure in syntactic foam during manufacturing. Methods: The investigation has been restricted to the flexural vibrations of sandwich composite beams, which are the predominant mode of vibration in many practical vibration scenarios. Experimentally modal analyses are carried out to analyze the vibration signals under different boundary conditions. Initially suitable theoretical model is used to validate the experimental results. Results: Results obtained from the investigation reveals that the stiffened syntactic foam core sandwich composite shows excellent vibration attenuation characteristics. This behaviour can be attributed to the presence of stiffening grid honeycomb cells in the syntactic foam core. Each cell wall of the honeycomb grid leads to the interference between the incident wave and the reflected wave under vibrating condition. Further, the vibration response characteristics are significantly affected by the orientation and boundary conditions. It is observed that the increase in the frequency of vibration, better quality factor and minor decrease in the damping ratio of sandwich composites are considerably influenced by the confined state of syntactic foam in the hexagonal cell size of honeycomb stiffening grid structure. Conclusion: The improvement in quality factor highlights the significant influence of continuum characteristics of honeycomb grid stiffened syntactic-foam cored sandwich composites. [ABSTRACT FROM AUTHOR]

Apart from the inherent anomalous behaviour under tensile and compressive structures, auxetic structures have shown improved energy absorption characteristics that are of prime interest to various fields of study. This is further exemplified by additive manufacturing (AM) techniques and polymer composites to tailor the shape, geometry and form of these structures. Consequently, this paper aims to characterise the in-plane compressive behaviour and negative Poisson's ratio (NPR) of the most prominent auxetic structures fabricated additively used polymer nanocomposite materials. The study incorporates the use of glycol-modified polyethylene terephthalate (PETG) and nanocomposites of PETG filled with organically modified montmorillonite (OMMT) nanoclay particles to produce auxetic structures fabricated through fused filament fabrication (FFF). Different structures such as hexagonal re-entrant honeycomb structures, peanut-shaped honeycombs, chiral honeycomb structures and missing rib structures are characterised for their compressive performance through experimental approaches involving mechanical testing and digital image correlation (DIC). Different parameters such as the peak crushing strength, average crushing strength, NPR, specific energy absorption (SEA), and crush force efficiency (CFE) of these structures are evaluated at different strain rates/loading rates for varying concentrations of nanoclay and PETG. It is observed that higher loadings of nanoclay particles lower the compressive strength of the structures. Additionally, the NPR decreases with increasing strain rates and is also influenced by the composition and the resultant stiffness. Moreover, the geometrical parameters of the structure largely influence its strain energy absorption. The results have shown that such material-structure combinations can produce structures of high-performance capabilities suitable for aerospace applications. [ABSTRACT FROM AUTHOR]

This study aims to improve the impact protection performance of composite structures by combining a honeycomb core with negative Poisson's ratio and graphene platelets reinforced (GPR) face sheets. The paper investigates the nonlinear repeated low-velocity impact responses of auxetic honeycomb composite plates, taking into account loading-unloading-reloading processes. Effective material properties of the auxetic honeycomb core and GPR face sheets are obtained by using the proposed modified Gibson function and Halpin-Tsai model. Then, taking into account geometric nonlinearity, the nonlinear equations of motion for the system were derived by Hamilton's principle. Afterward, the time-varying contact force between the composite plate and a spherical impactor is defined by the modified nonlinear Hertz contact theory. The Galerkin method and variable-step Runge-Kutta algorithm are selected to obtain nonlinear impact responses. The proposed methods are verified by finite element simulation and experiment. Finally, the study evaluates the effects of key parameters on the nonlinear repeated low-velocity impact responses. [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]

The crashworthiness of embedded composite structures that couple carbon fiber reinforced plastic tubes and aluminum honeycomb (CFRP-AH) was assessed through quasi-static compression tests and finite element simulation. Experimental results show that CFRP tubes tilt, when the AH fits with the CFRP tubes is not tight enough. With an increasing number of embedded CFRP tubes, the CFRP-AH composite structures are found to have a larger mean crush force (MCF) and specific energy absorption (SEA). Among the four experimental groups, CFRP-AH composite structures in Group S3, which used a larger size of CFRP tube, are found to have significantly improved energy-absorbing performance, and SEA of S3-t25 is improved by 576% compared with that of the pure AH S3-t0 without tubes. The S2 group's CFRP tube is tilted, which used a smaller size, and the structure is improved to obtain the NS2 structure, so that only tearing deformation occurs in the AH-CFRP structure's CFRP tube. The SEA of NS2-t25 was improved by 29.70% over S2-t25 and 22.83% over S3-t25, which has the best energy absorption characteristics among the filled tube structures. [ABSTRACT FROM AUTHOR]

Sandwich structure with honeycomb core and CFRP facesheets is increasingly used in the high-performance fields due to the high specific stiffness and strength. However, it is susceptible to localized low-velocity impacts such as tool drop during maintenance, and thus, understanding the damage behavior is important for a safety design and optimization. The objective of this article is to investigate the influence of the structural parameters and impact energy on the damage behaviors of the composite honeycomb sandwich panels subjected to localized low-velocity impact. An effective computational framework considering complicate damage mechanisms is proposed to predict the failure patterns, load history, and energy absorption. Comparisons with the experimental data show that the error of predictions is within 4% and thus the framework is validated. Then, a comprehensive parametric study is conducted to explore the effects of wall thickness and height of honeycomb, impact energy, and stacking sequences of the laminated facesheets on the impact resistance, damage behaviors, and energy absorption of the sandwich structure. The reported results may be useful in practice. [ABSTRACT FROM AUTHOR]

This study investigated the feasibility of using natural fiber material to create honeycomb cores, as traditional cores made of aluminum, Nomex, and petroleum‐based materials are not environmentally friendly. The natural fiber honeycomb cores were formed using a 3D printed molding process and were bonded to flax and glass fiber facings to improve the durability of the structures. The addition of cellulose and nanoclay to the adhesive enhanced the flexural strength of the structures by 7.43% and 10.48%, respectively, while also absorbing 8.67% and 8.91% more impact energy than structures bonded with epoxy alone. However, the compressive strength decreased by 10.79% and 13.6% with the addition of cellulose and nanoclay to the adhesive, respectively. Tensile properties were also studied, and the tensile strength of hybrid facings was found to be 69.45% higher than those using solely flax facings. Additionally, hybrid facings effectively reduced moisture uptake, making them hydrophobic and reducing water uptake by 46.89% compared to solely flax facings. Overall, natural fiber honeycomb composite structures showed comparable performance to Nomex and aluminum honeycomb composites, offering favorable properties while being constructed using environmentally friendly materials. The efficient manufacturing process using additive manufacturing makes these structures readily customizable and scalable, leading to their implementation in numerous applications such as aerospace, automotive, and marine industries. [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]

In the composite structure of spacecraft, the honeycomb sandwich structure is the basic bearing component used to bear and transmit loads. To explore the influencing factors on the bearing capacity of honeycomb sandwich structures, this study combines local tests and speckle measurement systems to conduct tensile tests on 10 test specimens with different parameters. Firstly, a comprehensive assessment was conducted on the accuracy of the loading and measurement system, the rationality of the testing method, and the mechanical properties of the test piece. It was found that the maximum measurement error of the speckle measurement system did not exceed 0.01 mm, and the differences between the yield load and failure load measured using different inner diameters of the compression ring were 0.15% and 3.84%, respectively. This indicates that the measurement system is accurate and that the influence of the inner diameter of the compression ring can be ignored. Moreover, it was found that considering the accuracy retention ability of the structure under load, the allowable load of the embedded parts is about 90% of the yield load. Finally, the data of specimens with different parameters were compared and it was found that the strength of the honeycomb sandwich structure is directly proportional to the thickness of the skin, the density of the honeycomb core cells, and the size of the embedded parts. [ABSTRACT FROM AUTHOR]

The paper deals with the main aspects of the technique for weight optimization of design parameters of sandwich shell-type composite structures with a honeycomb filler. This technique was implemented in the framework of the comprehensive approach proposed earlier for the integrated designing of assembly units of the equipment class considered. Multi-parameter problem of optimization of the parameters of sandwich shell-type composite structures was solved. The optimization process was divided into several stages in accordance with the reasonable levels of significance of the parameters included in the objective function, i.e., minimum weight. The results allow us to achieve a deep level of simultaneous optimization of the reinforcement pattern and structure of load-bearing skins, the height of the honeycomb filler, and the geometric parameters of its cell, as well as parameters of the additional structural frame in the regular zone and local reinforcement zones for almost all spectrum of external actions. At the same time, the load-bearing capacity of the structure was provided in all critical areas taking into account the deterioration of the physicomechanical characteristics of materials employed due to thermal effect and fulfilment of additional functional and technological constraints. Using an example of the interstage compartment of a launch rocket, implementation of the technique proposed for synthesis of its rational design and technology parameters was shown. Results of ground-based strength tests of the interstage compartment at this stage of development confirmed the reliability of the results obtained. The results taken as a whole form are the scientific basis for the rational design of sandwich shell-type systems with the honeycomb filler under simultaneous strength and thermal loadings, taking into account of technological constraints and can be used in designing of the other load-bearing shell-type units for aviation, space, and conversion applications. [ABSTRACT FROM AUTHOR]

Since the taper ratio of most wings is not equal to 1, the beam-disk trailing edge deflection mechanism originally designed for the rectangular wing is not fully applicable to the non-equal chord wing. Moreover, it is not only expected that the wing shape can achieve excellent aerodynamic performance under different flight conditions, but one also needs to consider whether the flexible skin can achieve this deformation. This paper used the honeycomb composite structure with zero Poisson's ratio as the flexible skin of the trailing edge for the variable camber wing, and designed the beam-disk trailing edge deflection mechanism for the non-equal chord wing. The aerodynamic configuration was optimized considering the deformation capability of the skin, and the multidisciplinary design and optimization method of the variable camber wing with non-equal chord was studied. The results show that the aerodynamic performances of the optimized non-equal chord wings were better than before under all given flight conditions. The flexible skin could withstand the strain caused by the maximum deflection of the trailing edge of the wing, and the weight of the wing structure was reduced by 47.1% compared with the initial design when the structural stiffness and strength were satisfied. [ABSTRACT FROM AUTHOR]

A honeycomb sandwich battery box composed of high-strength steel outer layer, sandwich aluminum alloy honeycomb and inner layer is proposed. Firstly, the expressions of platform stress, ultimate strain and equivalent elastic modulus of 'Y' honeycomb cell are derived based on deformation mechanism and energy principle under quasi-static compression, and then the relations among relative density, unit volume energy absorption and thickness coefficient are acquired. Based on above, the optimal thickness coefficient of honeycomb unit cell can be acquired by utilizing particle swarm optimization algorithm. Simultaneously, aluminum alloy honeycomb sample is made to verify the accuracy of finite element simulation and theoretical models under quasi-static compression. Subsequently, the optimal thicknesses of three layers are optimized with the constraint that the 1st mode frequency is more than 30 Hz. Finally, the mass of the optimized battery box decreases by 37.26 %, and its static performances increase more largely compared with traditional one. [ABSTRACT FROM AUTHOR]

The interlocked composite honeycomb structures have high specific strength and specific stiffness, convenient processing, and low cost with great application potential in aerospace, marine, construction, and civil fields. In this study, an effective method is proposed for manufacturing an all‐composite interlocked triangular honeycomb (CITH), and the quasi‐static mechanical properties of the honeycomb and the corresponding sandwich structure (CITHSS) are examined. Through experimental tests, the basic mechanical properties of CITH and CITHSS are analyzed. Further, the effective strength and stiffness coefficient of the slotted carbon sheets constituting CITH are measured through tensile experiments. The in‐plane stiffness model of CITH is derived based on the continuous equivalent method. The failure strength models of CITHSS are also established. At the same time, the failure modes under three‐point bending and edge compression loads are predicted. The experimental results reveal that compared with the interlocked Kagome and square honeycomb, the specific strength of CITH is increased by 27.8% and 24.4%, respectively. Further, the specific stiffness is increased by 148.4% and 8.3%, respectively. Compared with aluminum honeycomb sandwich, the compressive and bending specific strengths of CITHSS are increased by more than 46.5% and 15.2%, respectively. The debonding failure and edge effect are found to be the main weakness of CITHSS. Overall, CTIH and CITHSS exhibit excellent mechanical properties and create feasible options for processing complex multifunctional composite honeycombs by interlocking technology. [ABSTRACT FROM AUTHOR]

The Uniform Honeycomb-filled Tube (UHT) is one of the composite structures that has shown huge potential in absorbing energy. In this paper, Uniform Honeycomb (UH) filler is replaced by an enhanced Modularized Honeycomb (MH). The biggest advantage of MH is that it can significantly enhance energy absorption without adding weight compared with its uniform counterpart. Finite element models are created, and then validated by theoretical models. The energy absorption of the Modularized Honeycomb-filled Tube (MHT) is compared with that of the empty tube and UHT. The results show that the MHT is superior to them in Specific Energy Absorption (SEA). It is also found that the tube can help the MH improve its deformation stability, which is the key of the MHT's excellent energy absorption capacity. Then, effects of design parameters on the SEA of the MHT are investigated and discussed. The results show that the MH with a large graded coefficient is good for enhancing the SEA of the MHT. However, the SEA also relies on the match between the honeycomb filler and tube walls. The work could inspire designs of modularized filler with various types of cells and benefit the development of advanced energy absorbers with lighter weight and more excellent energy absorption capacity. [ABSTRACT FROM AUTHOR]

Paper honeycomb and EPE are widely used in the field of packaging protection and safety transportation. Given the cushioning and protective function of unilateral and bilateral composite layered structures (CLSs) including polyethylene foam (EPE) and paper honeycomb, this work focused on analyzing the energy absorption (EA) and compression deformation of honeycomb thickness (HT) CLS under diverse drop impact (DI) status. Experimental observation showed that the increase of HT can improve the impact resistance of EPE and its CLSs. For the CLS with the HTs of 10, 15, 20, and 25 mm, the increase of paper HT may reduce the EA at low impact energy, while enhancing the EA capability at high impact energy. However, the EA of CLSs with a large HT of 70 mm is relatively poor. For the same drop weight mass or impact energy, the stroke efficiency (SE) and specific energy absorption (SEA) of the unilateral CLS with the same HT are, respectively, increased by 39.1% and 16.2%, so the EA of the unilateral CLS is superior to the bilateral CLS. [ABSTRACT FROM AUTHOR]

The composite re‐entrant honeycomb structures were fabricated by hot pressing and bonding processes in this article. The bending responses of composite re‐entrant honeycomb structure under three‐point bending load were studied experimentally. The bending deformation, failure process and failure load were analyzed and discussed. The influence of wall thickness gradient form which were less reported on the bending behaviors of composite re‐entrant honeycomb structures was investigated. The gradient distributions included positive gradient, negative gradient and homogeneous structures. The experimental results indicated that the wall thickness gradient design influenced the bending failure modes of composite re‐entrant honeycomb structures, and the negative gradient honeycomb structure mainly exhibited the whole bending deformation under three‐point bending loading. The influence of the relative densities on the bending behaviors of composite re‐entrant honeycomb structures was also studied. The results of three‐point bending experiment showed that the bending failure load increased significantly with the increase of relative density. [ABSTRACT FROM AUTHOR]

The trapped air in unvented honeycomb core and the surrounding environment can induce a pressure differential across the facesheet during launch ascent. Combined with the presence of a defect, the pressure differential across a facesheet in combination with external loads can cause facesheet failure or unstable facesheet debond growth. While honeycomb core venting is the recommended solution, there might be practical limitations in implementing this solution or the possibility that a structure intended to be vented is partially unvented due to manufacturing issues. A methodology for accepting composite sandwich structures for space applications is presented, which heavily relies on the building block approach to characterize the facesheet strength and interfacial fracture toughness. To demonstrate the approach, an allowable flaw size is defined for a hypothetical flight condition using analyses anchored to subscale tests. [ABSTRACT FROM AUTHOR]

The Glycerol monolaurate (GML) oleogel was induced using Camellia oil by slowly raising the temp to the melting point (MP) of GML. Whey protein isolate (WPI) solution with different ratios was composited with GML oleogel by emulsion template methods, forming dense spines and honeycomb-like networks and impressed with an adjustable composite structure. Textural results showed that compared with single GML-based oleogels, the GML/WPI composite oleogels had the advantages of high hardness and molding, and structural stability. The composite oleogels had moderate thermal stability and maximal oil binding (96.36%). In particular, as up to 6 wt% GML/WPI, its modulus apparent viscosity was significantly increased in rheology and similar to commercial fats. Moreover, it achieved the highest release of FFA (64.07%) and the synergy provided a lipase substrate and reduced the body's burden. The resulting composite oleogel also showed intermolecular hydrogen bonding and van der Waals force interactions. These findings further enlarge the application in the plant and animal-based combined of fat substitutes, delivery of bioactive molecules, etc. , with the desired physical and functional properties according to different proportions. [Display omitted] • Monoglycerides and proteins imparted spines and honeycomb network structures. • Oleogels exhibited favorable oil-holding, stronger rigidity, and thermal stability. • Hydrogen bonding-induced protein polymerization was the dominant interaction within composite oleogels. • The rheological properties were similar to commercial fats. • The synergy provided a lipase substrate and reduced the body's burden. [ABSTRACT FROM AUTHOR]

A novel, 12 mm multilayer dielectric gradient honeycomb absorber (MGHA) was designed, fabricated and analyzed with a double layer metasurface consisting of a resistive film and an artificial magnetic conductor (AMC) checkerboard. Despite its thin profile, the MGHA demonstrates significantly enhanced absorption performance across a wide frequency range due to the impedance of the composite structure. Furthermore, two distinct metasurfaces are integrated into the dielectric gradient multilayer honeycomb absorber to further enhance its low-frequency properties without increasing thickness. This structure exhibits wideband absorption from 2.8 GHz to 18 GHz, featuring three absorption peaks at 3 GHz, 11 GHz and 16 GHz. The relative bandwidth can reach nearly 136.6 % of that achieved by a common honeycomb absorber with the same thickness, while maintaining an absorption peak reflection of about −22dB. The great attenuation of incident waves is attributed to Ohmic loss on the resistive film, electric resonance effect on the checkerboard, and magnetic resonance near 17 GHz on the checkerboard metasurface. The proposed MGHA structure holds significant potential for applications in aerospace and military. • Multi-layer honeycombs have better absorption performance than single-layer ones of the same height because of improved impedance matching. • Three types of resistive film metasurface are added to the multilayer dielectric gradient honeycomb absorber, improving absorption. • A multilayer absorber with resistive film and AMC checkerboard metasurfaces has wideband absorbing property from 2.8 GHz to 18 GHz, which is almost 136.6% better than a common honeycomb absorber of the same thickness. • Hence, this novel multilayer dielectric gradient honeycombs absorber with double layer metasurface shows greatly potential application in aerospace and military and will attract wide readership. [ABSTRACT FROM AUTHOR]

• Thermal-force external coupling enhances polyimide molecular chain orientation. • Orientation modulation increases the honeycomb shear strength 10 times to 1.07 MPa. • Excellent thermal performance of polyimide aerogel honeycomb (T d5% >650 °C). • Fabricating integrated lightweight honeycomb structures using the formwork method. Lightweight honeycomb structures are widely used in applications that require high strength-to-weight ratios and low densities, including aircraft, automobiles, and various engine components. However, due to the immaturity of microstructure conditioning techniques and the fact that highly porous structures usually fracture during stretching, it is challenging to obtain both high-strength and lightweight porous structures. Herein, a newly developed multilayer interconnected polyimide aerogel-based paper honeycomb is successfully prepared based on the ice crystal reverse template method and multi-level structure regulation via chemical and physical interactions. The synergistic effect of the hot extrusion-stress strategy and the heat imidization process provides the submicron layer of the paper honeycomb wall with more orderly molecular chain stacking, excellent orientation, and an enhanced folding degree between layers. The prepared polyimide aerogel paper honeycombs have low density (approx. 8–9 kg/m3), good shear strength of 1.07 MPa (W direction) and 0.86 MPa (L direction), excellent specific compressive strength (0.38 MPa), and excellent thermal stability. These integrally molded polyimide paper honeycombs, as sandwich resin-based composite structures, provide a new versatile platform for aerospace and marine applications. [ABSTRACT FROM AUTHOR]

Thermal characterization of honeycomb core sandwich panels with GFRP skins by theoretical formulations, and experimental methods followed by corroborating numerical models help identify the effective thermal conductivity in both the out-of-plane and in-plane directions. Swann–Pitman's semi-empirical model formed the basis for the theoretical understanding of heat transfer in honeycomb core sandwich panels. Experimental approach involved a setup based on guarded hot plate (GHP) apparatus, and transient laser flash technique while the numerical approach involved FE modeling of the woven composite fabric face sheet by multi-scale modeling using the actual physical dimensions of the yarn e.g., crimp angle, width and height of the yarns etc. obtained using microscopic analysis. The fiber volume fraction of the experimental samples was estimated both by image analysis and burn-off method using Thermogravimetry (TGA). Various numerical models based on Mechanics of Structure Genome (MSG) and randomized fiber distribution in the yarns at the micro-level are compared with the experimental results to arrive at the model that most closely mimics real situation. Then, the numerical model is used to predict the thermal conductivity of the composite as the fiber volume fraction and crimp angle varies. • Heat flow in sandwich structures with composite facesheets is dominated by core cell wall conduction. • Better representative RVE model of the composite yarns using data from micrograph images, and Procrustes analysis. • E-glass/polypropylene facesheets perform better at low crimp angle and fiber volume fraction (V f). • Small "resin-rich" matrix region disrupts heat flow in facesheets. [ABSTRACT FROM AUTHOR]

• Hybrid re-entrant/hexagonal CF/PA12 honeycombs were 3D printed via FFF. • Temperature-dependent mechanical and piezoresistive characteristics were evaluated. • Hybrid honeycombs excel in enhancing in-plane strength (+64 %) and energy absorption (+125 %). • Hybrid honeycombs exhibit remarkable strain-sensing abilities, boasting gauge factors of ∼146. • The hybrid honeycombs retain 40–60 % of their mechanical properties at 125 °C. This study investigates a novel self-sensing honeycomb composite structure composed of two distinct cellular layers with differing unit cell architectures, specifically hexagonal and re-entrant designs. Short carbon fiber (CF)/polyamide 12 (PA12) composite filaments with 0, 5 or 15 wt.% CF content were utilized to additively manufacture the honeycomb structures via Fused Filament Fabrication (FFF), and their mechanical and piezoresistive self-sensing characteristics were experimentally investigated under quasi-static in-plane and out-of-plane compression at both room temperature and elevated temperatures. The results reveal that the hybrid hexagonal/re-entrant (HR) honeycombs mechanically outperform their non-hybrid double-layer and single-layer counterparts under in-plane loading, reporting an increase in collapse strength and energy absorption by factors of 1.64 and 2.25, respectively. These improvements are attributed to the mechanical interactions occurring at the interface between the auxetic and non-auxetic layers within the hybrid structure, effectively enhancing its structural attributes. Furthermore, the double-layer honeycombs display excellent strain-sensing capabilities within the elastic regime, with gauge factors reaching values as high as 146. Mechanical tests conducted at elevated temperatures reveal that the CF/PA12 honeycombs retain a significant portion of their elastic modulus, strength and energy absorption even at 125 °C, while maintaining high gauge factors of up to 72.4. These honeycombs also exhibit pronounced thermoresistive behavior, evidenced by a decrease in electrical resistance of up to 41.3 % with increasing temperatures from 25 to 125 °C. Considering their exceptional combination of thermo-mechanical, thermoresistive and piezoresistive characteristics, these hybrid double-layered CF/PA12 honeycombs hold promise for potential applications in multifunctional lightweight structures, offering integrated temperature and strain-sensing capabilities. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Bioinspired design was used to ceramic materials via DIW technique. • Polysilazane (PSZ) based ceramic materials were printed by DIW 3D printing. • B 4 C-based honeycomb ceramic 3D structures were printed by PSZ/B 4 C ink. • B 4 C-based honeycomb ceramic was impregnated by epoxy resin for armor structures. B 4 C ceramic holds enormous application potential in the lightweight armors. In order to simplify the design of armor materials, 3D printed B 4 C-based honeycomb ceramic via DIW technique with high solid content were fabricated using printing ink with B 4 C powder, BYK-2070 dispersant, BAC solvent, PSZ adhesive and DCP cross-linking agent. The role of each constituent and the printing parameters of such honeycomb ceramic were investigated. In addition, epoxy resin was employed to impregnate PSZ-modified B 4 C-based honeycomb ceramic to prepare three-dimensional structure hybrid composites with excellent mechanical strength (172 MPa of flexural strength, 4.95 KJ/m2 of impact strength) and physiochemical properties (7.52 % of open porosity, 5.5 % of water absorption, 1.35 g/cm−1 of density, and 5.2 GPa of hardness). The exceptional performances of the three-dimensional structure hybrid composite come from the bioinspired structure design, new chemical bonds (such as the formation of B–C, C–N and Si–B bonds) formed in the ceramic material and cross-linking reaction occurred during curing between epoxy resin and PSZ. The findings in this study provide an effective strategy for the fabrication of B 4 C-based composites with controllable structures and mechanical performances and exhibit the potential application in complex armor structures. [ABSTRACT FROM AUTHOR]

In this study, the buckling loads of a composite sandwich structure, which is reinforced by a honeycomb layer and filled with viscoelastic damping material, are analyzed. By applying von Karman anisotropic plate equations for large deflection, the governing equation of the composite sandwich structure is determined, and the deflection of the structure is further defined by a double triangular series. According to the dynamic equivalent effective stiffness obtained by the homogenous asymptotic method and Hill's generalized self-consistent model based on the Halpin–Tsai model, limiting the dynamic load buckling of the composite honeycomb reinforced sandwich structure embedded with viscoelastic damping material under axial compression can be achieved. The factors that influence the composite sandwich's buckling loads are discussed and compared, such as the load and geometry parameters, the thickness of the honeycomb reinforcement layer and the honeycomb's width. Finally, the results obtained by the present method are validated by the existing literature. [ABSTRACT FROM AUTHOR]

A lot of researches on continuous carbon-fiber composite laminates have been conducted, but no scrutiny has been devoted to continuous carbon-fiber composite honeycomb sandwiches. This paper is aimed to assess the design and properties aspects of honeycomb sandwiches made of continuous carbon-fiber composite laminates. The applicability of the existing theoretical formulas for the mechanical properties of isotropic material honeycomb sandwich on continuous carbon-fiber composite honeycomb is examined by comparing the obtained results from the finite-element modeling and experimental results. The results reveal that the theoretical formulas of isotropic material honeycomb sandwich in density and out-of-plane compressive elastic modulus are suitable for continuous carbon-fiber composite honeycomb, while other performances cannot be achieved by theoretical formulas of isotropic material honeycomb sandwiches. The out-of-plane compression and shear properties of continuous carbon-fiber composite honeycomb can be evaluated by finite-element modeling. The effects of cell side length, wall thickness, and 45° ply content on the honeycomb density, out-of-plane compression properties and out-of-plane shear strength are researched. Subsequently, the out-of-plane compression experiments of honeycomb are carried out to show the accuracy of the finite-element modeling. Finally, a design approach for continuous carbon-fiber composites honeycomb structures is proposed. This methodology results in the design of honeycomb sandwiches with better performances. The chief innovation of this paper is to develop the concept of continuous carbon-fiber composite honeycomb sandwich structures. To this end, a honeycomb structure finite-element model of continuous carbon-fiber composite is established, and the mechanical properties of continuous carbon-fiber composite honeycomb sandwiches are explored. A methodology for the rapid design of honeycomb size parameters of continuous carbon fiber composite honeycomb sandwich is also proposed. [ABSTRACT FROM AUTHOR]

Most spoilers are made from a sandwich structure with a honeycomb component as its core. However, the honeycomb core is sensitive to water ingress, causing damage to the control surface due to its weak moisture-resistance behavior. This study aimed to conduct the design and analysis of an improved composite structure for a coreless spoiler. A spoiler design of an aircraft, the A320, was used for the case study. The weaknesses of a coreless spoiler were identified through finite element analysis via Abaqus software. Multi-spar and multi-rib designs were studied and compared for topological optimization. The variables used for evaluation were the Tsai–Hill failure index and the critical buckling load. The design with the most potential was considered for parametric optimization to obtain the most satisfactory configuration. The results showed that the upper skin of the spoiler without a honeycomb core failed the Tsai–Hill criteria. Furthermore, the results show that the multi-spar configuration outperformed the multi-rib configuration. The final multi-spar configuration achieved a mass reduction of 24% from the original spoiler and an additional 6% mass reduction by re-designing the internal structures without violating the design criteria. In conclusion, the weaknesses of the spoiler without a honeycomb core have been identified, and an improved design for a coreless spoiler has been proposed. [ABSTRACT FROM AUTHOR]

The low‐velocity impacts that represent the equipment drop during maintenance and production, crash and drops of luggage that may occur during transportation and bird strikes during takeoff may occur in aircraft parts where honeycomb composite structures are used. Therefore, the low‐velocity impact (LVI) resistance of aircraft components is crucial. In this study, the effect of graphene nano platelets (GNPs) on the LVI behaviors of the BFR (basalt fiber reinforcement) laminated face‐sheets and the interface adhesive between the face‐sheet and the aluminum honeycomb core for composite sandwich structures were investigated. LVI tests were applied to GNPs doped and un‐doped BFR/aluminum composite sandwich samples to determine the values of the impact forces, displacements, interaction times, and absorbed energy at two different energy levels of 10 J and 20 J. The surface damages in the impact zones of the GNPs doped and un‐doped BFR laminated top face‐sheets of the sandwich samples were investigated on a macro scale with liquid penetrant. The damage formation and development of GNPs were detected in the cross‐sectional micro‐images of the top face‐sheets. SEM analysis was accomplished to define the fracture mechanisms provided by GNPs. As a consequence of tests and damage analysis, it was reported that GNPs increase the impact resistance of BFR/aluminum honeycomb composite sandwiches and limit and reduce damage development. GNPs showed increases in force and rebound energies of approximately 16.1% and 21.1% for 10 J, and approximately 8.2% and 14.7% for 20 J, respectively. [ABSTRACT FROM AUTHOR]