Honeycomb Core Sandwich Panels Research Articles

Adhesion Systems in New Supports for Mural Paintings: Reversibility Tests

ABSTRACT This article presents a study that investigates the utilization of diverse adhesives and intervention layers for affixing new supports to archaeological mural paintings that cannot be preserved in their original state. Depending on artwork characteristics (materiality, dimensions, state of conservation, location), various materials can be employed for attaching new supports, encompassing adhesives and intervention layers. Evaluating and assessing these materials is vital to ensure the stability, reversibility, and notably, the retreatability of the artwork. To this end, we have evaluated three commonly used adhesives and three intervention layers applied to new mural painting supports. We prepared test samples of mural paintings affixed to a new support structure, utilizing an aluminum honeycomb core sandwich panel (Aerolam). Through bibliographic analysis, we identified frequently used adhesives and intervention layers, and conducted an initial assessment of their behavior. Subsequently, following an aging process, we conducted color evaluations and reversibility tests to comprehensively study these materials and facilitate an objective comparison of their properties.

Research on The Damping Characteristics of Partially Filled All-Composite Honeycomb-Core Sandwich Panel

Research on The Damping Characteristics of Partially Filled All-Composite Honeycomb-Core Sandwich Panel

Characterization of the mechanical energy absorption of honeycomb core sandwich panels filled with shear thickening fluid under low speed impact

Characterization of the mechanical energy absorption of honeycomb core sandwich panels filled with shear thickening fluid under low speed impact

Experimental investigation with FE analysis on flexural strength of hexagonal-shaped honeycomb sandwich panel

In this study, a three-point bending test was carried out to determine the mechanical properties of hexagonal-shaped honeycomb core sandwich panels made of jute yarn with two distinct fiber orientations. A custom-made handloom was used to weave the unidirectional jute mat, and hand-layup with the cold press process was applied to fabricate the hexagonal honeycomb sandwich panel. To explore the effectiveness of different natural fibers for producing honeycomb core sandwich panels, a Finite Element Method (FEM) analysis was performed on different natural fibers with different fiber orientations. The resistance to environmental deterioration of bending properties was also investigated. Overall, this work offers perceptive information about the mechanical characteristics of sandwich panels made of jute honeycomb core and their behavior under various climatic circumstances, which may be relevant in a variety of engineering applications. Finally, it is noteworthy that the mechanical properties of jute fibers are anisotropic, which implies that their strength varies with the direction of loading. Sandwich panels with horizontal fiber orientation of hexagonal honeycomb core withstand a 36% higher bending strength than those with vertical fiber orientation.

Ultrasonically welded eco-friendly sandwich panels based on upcycled thermoplastic core: An eco-mechanical characterisation

A structure's sustainability depends not only on its components, but also on the manufacturing process. The adhesive layer mostly increases the structural weight, reducing weight-specific properties, beside hindering its disassembly and sorting at end-of-life. This study investigates an alternative joining method based on ultrasonic welding for upcycled honeycomb core sandwich panels. Thermoplastic composite skins, reinforced with flax or glass fibres, are connected to an upcycled polyethylene core made from disposed bottle caps and tested under quasi-static and dynamic loads. A life cycle assessment evaluates the environmental benefits of skin/core welding compared with adhesive bonding. Welded panels made from similar skins and cores presented similar to higher weight-specific flexural properties of adhesive-bonded structures (up to 45 % increase), while specific energy absorption under impact is increased by up to 23 % with welded joints. Skin/core welding reduces the panel environmental damage by up to 71 %, with an increment of up to 130 % in its eco-mechanical efficiency.

Response of aluminium honeycomb sandwich panels under combined shock and impact loading: Experimental and numerical investigations

The performance of sandwich structures against individual shock loading and fragment impact loading has been extensively examined, but little is known about their performance in the presence of simultaneous shock and impact loading. Based on a recently developed composite projectile to simulate combined shock and single fragment impact loading, the performance of aluminum honeycomb core sandwich panels (HCSPs) against combined loading is methodically examined. The achieved results reveal that the combined loading exhibits a synergistic effect compared to the single loading, i.e., increased damage of the sandwich panel and enhanced perforation resistance of the sandwich panel. After that, a three-dimensional finite element simulation is performed to explore the underlying mechanism of the synergistic effect. Numerical analysis indicates that the increased damage is a result of perforation-induced reduction of load-carrying capacity of sandwich panel, while the enhanced perforation resistance is the result of deflecting-induced perforation time delay of the perforation process. Finally, the parametric investigation of sandwich geometries such as asymmetric face sheets, core density, and core height is comprehensively conducted. The gained results reveal that both performance and synergistic effect due to combined loading are sensitive to these parameters.

Influence of core topology on blast mitigation application of multi-layered honeycomb core sandwich panel

In the past years, the aluminium honeycomb core sandwich panel has emerged as a promising blast mitigation solution owing to its high energy absorbing capacity under impulsive loading. To enhance its performance against the blast load, it is important to understand the mechanical behaviour of honeycomb core sandwich panel with varying core configurations. The present study investigates the difference in load mitigation behaviour of sandwich panel under blast loading with different honeycomb core topologies. Three types of honeycomb core topology i.e., square, circular, and hexagonal are considered in the present study. The performance of the sandwich panels under blast loading is compared for two criteria i.e., constant mass (or aerial density) and constant cell size. The influence of a multi-layered core along with the intermediate sheets on the blast resistance of sandwich panel is further examined under blast load. It is observed that the multi-layered core and intermediate sheets not only strengthen the sandwich panel but also make it significantly stronger under the blast loading in comparison to the single layer sandwich panel. The role of intermediate sheets in energy dissipation is observed to be insignificant in multi-layered sandwich panel for the parameters considered in this investigation. Further, it is observed that the difference in energy dissipated by front face sheet and back face sheet is increased with increase in the number of layers of cores.

Performance evaluation of composite sandwich structures with additively manufactured aluminum honeycomb cores with increased bonding surface area

AbstractModern 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.

Fabrication and Experimental Characteristics of Aluminum Honeycomb Core Sandwich Panel Compared with Nomex Honeycomb Sandwich Panel

Fabrication and Experimental Characteristics of Aluminum Honeycomb Core Sandwich Panel Compared with Nomex Honeycomb Sandwich Panel

Dynamic response of honeycomb cored sandwich panels under high velocity impact: A numerical study

To investigate the impact resisting behavior of honeycomb cored sandwich panel under the bullet attacks, birds and debris, computational analysis of ballistic impact tests have been performed. The honeycomb sandwich panel with SS 316L front and back sheets are used owing to its better impact resistance, high ductility and superior strength for impact resisting applications. The Ballistic test simulations under a wide range of 150 to 800 m/s have been carried out on a SS 316L sandwich panel embedded with Aluminum alloy (AA 3003) honeycomb core using ABAQUS/Explicit software. For this, 12 mm thick sandwich panel and three types of bullet profiles namely conical, hemispherical and blunt are considered. The initial and residual velocity obtained from the simulation is used for computing the dynamic energy absorption of the panels. The significance of projectile velocity, nose shape on overall energy absorption capacity of the panel have been thoroughly investigated. The sandwich panel reportedly absorbed 20.6% and 41.2% higher energy when impacted with blunt projectile than those impacted with hemispherical and conical bullets. Moreover, an almost linear increase in the overall energy absorption capacity of the panel have been observed by increasing the striking sheet thickness.

Sound absorption performance of a micro perforated sandwich panel with honeycomb-hierarchical pore structure core

A new micro perforated sandwich panel with honeycomb-hierarchical pore structure core is designed and prepared in this study. Carbonized cotton with hierarchical pore structure is combined with a micro perforated honeycomb core sandwich panel, which enhances the sound-absorbing performance of the structure without significantly increasing its weight. The experiment showed that pure carbonized cotton filling can improve the average sound absorption coefficient (at 125, 250, 500, 1000, 2000, and 4000 Hz) of the structure from 0.220 to 0.558, and hierarchical pore structure can further improve the average sound absorption coefficient to 0.626. Meanwhile, appropriate theoretical and finite element models are established, with 16.8 % and 8.6 % error respectively based on the predicted average sound absorption coefficient relative to experimental results.

The Dynamic Response of AuxHex and Star-Reentrant Honeycomb Cored Sandwich Panels Subject to Blast Loading

The Dynamic Response of AuxHex and Star-Reentrant Honeycomb Cored Sandwich Panels Subject to Blast Loading

INVESTIGATION IN TO THE STATIC AND DYNAMIC PROPERTIES OF LIGHTWEIGHT STRUCTURAL SANDWICH PANEL

Analytical investigations on the static and dynamic behaviour of light weight structural sandwich panels, which are widely employed in maritime, aircraft, transport, and mechanical/civil engineering applications, are provided. These light, thin-walled structures can vibrate ferociously and are sensitive to even the smallest disturbances. So, the main goal of this work is to improve sandwich panels' static and dynamic behaviour by investigating various face sheets and core materials. Studies on carbon-based polymer nanocomposite are currently generating more interest because to its favourable thermal, electric, magnetic, and structural characteristics. In this study, functionally graded carbon nanotube reinforced polymer composite faces with a 3D graphene foam core and functionally graded carbon nanotube reinforced polymer composite faces were all used to make the sandwich panels. Also, the thermal stresses created in this structure when these panels are exposed to a thermal environment have a significant impact on the dynamic behaviour. Hence, the honeycomb core and polymer composite sandwich panels with reinforced FG-CNT face sheets are examined in various thermal environments. This study examines the properties of forced and free vibration to analyse the dynamic behaviour of a structure

Parametric study of re-entrant honeycomb cored auxetic sandwich panel exposed to blast loading

The protection of military vehicles and critical infrastructure against Improvised Explosive Devices (IED) has become a significant challenge due to frequent terrorist attacks. Sandwich panel with periodic lattice structures as a core material has gained the attention of researchers for blast resistant applications because of their lightweight and high energy absorption capability. Auxetic structures are a class of lattice structures that possess a negative Poisson's ratio (NPR) owing to their topology as a consequence that it undergoes lateral contraction upon compression. Due to this lateral contraction, additional material movement takes place in the impact zone offering more resistance to the localized loading. Near field detonation of explosives imposes localized loading on the structures. The sandwich panel with an auxetic mechanism in the core provides maximum resistance at the point of loading by recruiting more material in the impact zone. The purpose of this study is to numerically investigate the performance of re-entrant honeycomb cored sandwich panels (RHSP) subjected to blast loading. It is followed by a parametric study for optimizing the energy absorption by the core and the force transmitted to the protected structure. Effects on the performance of RHSP for the variation in geometrical parameters, charge mass, and the number of core layers are discussed. Effective Poisson's ratio (EPR) is evaluated for quantifying the lateral contraction in the auxetic structure.

Numerical analysis of low-speed impact response of sandwich panels with bio-inspired diagonal-enhanced square honeycomb core

The diagonal-enhanced square grid configuration inspired by glass sponge has great potential in mechanics, with geometries serving as honeycomb cores for sandwich panels, which can improve the structure’s energy absorption capabilities. Modeling the hexagonal honeycomb core (HHC) sandwich panels, a finite element numerical model for low-speed impact of sandwich panels with high accuracy is proposed, and low-speed impact response of bio-inspired diagonal-enhanced square honeycomb core (BSHC) sandwich panels is studied. The impact response of BSHC sandwich panels, Hexagonal honeycomb core (HHC) sandwich panels and ordinary square honeycomb core (OSHC) sandwich panels were studied with the same relative densities and the same face-sheets. BSHC can lead to significantly enhanced the peak loads and stiffness of the sandwich panels. BSHC sandwich panels not only have excellent energy absorption performance, but also outperform HHC sandwich panels in terms of resistance to impact deformation. BSHC can transfer dynamic loads from the front face-sheet to the back face-sheet efficiently without stress concentration in the core itself. A theoretical analysis of the energy absorption capacity of the BSHCs and HHC were performed to illustrate the energy absorption mechanism. In addition, the peak load and contact energy of BSHC sandwich panels and HHC sandwich panels were theoretically predicted under low-speed impact.

Hoff's Investigation of The Sandwich Panel with Honeycomb Core

Recently, the use of sandwich panels has become increasingly important. This is due to its good mechanical properties and high strength-to-weight ratio. It is used in many fields, especially in aviation, construction and aerospace. It is necessary to know the behavior of the materials used, especially the free vibrations, to know the effect of external factors on the sandwich panels. The honeycomb core sandwich panel was studied. A model for analysis and modeling is proposed. A previous model was chosen for analysis and comparison. Hoff theory was applied to convert honeycomb sandwich panel into equivalent sandwich panel to facilitate the solution and save time. The limits were considered fixed on the one hand and moving on the other hand, and the ANSYS program was used to analyze and extract the results, and the results were compared and were promising and accurate, which proves to us the validity and accuracy of the proposed theoretical results

Gradient-based optimisation of rectangular honeycomb core sandwich panels

When subjected to bending loads, sandwich panels are highly efficient structural components with the potential to achieve substantial weight reduction. A successful design methodology for sandwich panels should aim at maximising this potential for weight reduction while considering the various possible failure mode in a simple yet accurate manner. This paper investigates the application of steel sandwich panels as two-way deck systems. Near-optimal designs for all-steel Rectangular Honeycomb Core Sandwich Panels (RHCSPs) under general out-of-plane loading are achieved using a gradient-based optimisation method. The method relies on continuously optimising the design limit state constraints while the response constraints are considered a priori in the analysis stage using simplified analytical assessment. Plate bending solutions and sandwich bending solutions are used as alternatives to estimate the internal stresses on each layer of the sandwich panel under out-of-plane loads, where comparisons are made between these two analysis methods in terms of computational efficiency and accuracy. The internal stresses are then used to formulate design limit state equations for each relevant failure mode, including material yielding, plate buckling and deformation control. The Method of Moving Asymptotes is used for the optimisation of RHCSPs, considering the limit states as the constraints of the optimisation problem and weight as the objective function to be minimised. The proposed methodology for simplified assessment is verified against detailed nonlinear finite element models for optimal design solutions. The implications of the results of the proposed optimisation strategy on the development of a systematic design methodology for RHCSPs are also highlighted, making specific reference to critical failure modes.

Vibration and aeroelastic stability analysis of hexagonal honeycomb core sandwich panels in supersonic airflow

This work investigates the vibration and aeroelastic stability behavior of honeycomb core sandwich panels with four-side simply supported boundaries in supersonic airflow. The sandwich panel includes a hexagonal honeycomb core layer with equal wall thickness, and upper and lower isotropic face sheets. The quasi-steady first order piston theory is used to model the aerodynamic pressure, and aeroelastic equations are established using Hamilton’s principle and a finite element approach. The effects of honeycomb core parameters on vibration and critical dynamic pressures of the honeycomb core panel are analyzed in two cases: Case 1, the dimensions of the simply supported hexagonal honeycomb sandwich panel is the same as the basic isotropic model; Case 2, the masses of the honeycomb sandwich panels are n(0<n≤1) times of the basic isotropic panel. The results show that the hexagonal honeycomb core can improve the natural frequencies of the panel. The honeycomb core thickness has a major influence on the critical dynamic pressure of the honeycomb sandwich panel, and the cell thickness, the cell angle and internal aspect ratio have no significant effect on the critical dynamic pressure. Compared with the basic isotropic panel, the mass can be reduced by nearly 70% using the honeycomb panel in the condition of the same critical dynamic pressure, which is of great significance to reduce the weight of the aircraft panel.

Experimental investigation of 3D-printed auxetic core sandwich structures under quasi-static and dynamic compression and bending loads

Auxiliary metamaterials designed according to the Negative Poisson’s Ratio (NPR) property are exciting structures due to their high impact strength, impact energy absorption abilities, and different damage mechanisms. These good mechanical features are suitable for aviation, automotive, and protective construction applications. These structures, whose most significant disadvantages are production difficulties, have become easier to produce with the development of 3D production technology and have been the subject of many studies in recent years. In this presented study, two conventional core geometries and three different auxetic geometries, commonly used in sandwich structures, were designed and produced with 3D printer technology. The strength and energy absorption capabilities of prototype sandwich structures investigated experimentally under bending loads with static and dynamic compression. Except for the re-entrant (RE) type core, the auxetic core foam sandwich structures demonstrate higher rigidity and load-carrying capacity than classical sinusoidal corrugated (SC) core and honeycomb (HC) core sandwich structures under both quasi-static and impact-loaded compression and three-point bending experiments. Double arrowhead (DAH) and tetrachiral (TC) auxetic cores outperformed honeycomb core in terms of specific quasi-static and impact load-bearing performance under compression by 1.5 ± 0.25 times. In three-point bending experiments under both quasi-static and impact loading conditions, the load-carrying capacity of the double arrowhead and tetrachiral auxetic cores was found to be more than 1,86 ± 0.38 times that of the honeycomb core sandwich panels.

An exact solution for vibro-acoustic response of smart sandwich panels with MEE composite Layer

To the best of our knowledge, this is the first endeavor to provide an exact solution for a vibro-acoustic response of Magneto-electro-elastic (MEE) composite plate and sandwich panels with MEE facings. The governing equation of motion is developed using Hamilton’s principle considering the third-order shear deformation theory to account for transverse shear. Based on boundary conditions and the Maxwell equation, the variation of electric and magnetic potentials are adopted along the thickness of the MEE composite layer. Analysis of the vibro-acoustic response of sandwich panels which are extensively used in aerospace structures such as cellular, trapezoidal, triangular, and honeycomb are presented. Influences of electric and magnetic potential on the vibro-acoustic response are also presented for the different types of truss core and honeycomb core sandwich panels.