Honeycomb Sandwich Construction Research Articles

Buckling Stability and Vibration Characteristics of Functionally Graded Graphene Platelet-Reinforced Composites Multi-Arc Concave Honeycomb Sandwich Panels Under Thermal Loading

The utilization of functionally graded graphene platelet-reinforced composites (FG-GPLRC) and honeycomb sandwich constructions is prevalent in the field of engineering. Therefore, it is crucial to investigate the buckling and vibration properties of these materials under heat circumstances. This paper specifically focuses on the vibration and thermal buckling characteristics of a novel multi-arc concave honeycomb sandwich plate (MACHSP) equipped with an adjustable positive-negative Poisson’s ratio. The governing equations of motion for the system are derived based on the first-order shear deformation theory in conjunction with Hamilton’s principle. The formulation of the system’s characteristic equation involves the establishment of displacement functions that satisfy distinct boundary conditions. Using computational programming, natural frequencies, mode shapes, and critical buckling temperatures of MACHSP with three different FG-GPLRC distributions under thermal influences are determined. Subsequently, these results are compared with outcomes from finite element simulations and findings from previously published literature. Additionally, the amplitude-frequency response characteristics of the structure under harmonic excitation are analyzed, followed by a discussion of the impact of structural parameters on its buckling and vibration characteristics. The results indicate that the established theoretical model for predicting the buckling and vibration characteristics of MACHSP with FG-GPLRC distribution aligns well with simulation models and prior research. In contrast to solid plates, MACHSP not only achieves a substantial reduction in weight but also demonstrates a significant increase in natural frequency. Furthermore, graphene platelets have the potential to enhance the structure’s natural frequency values and critical buckling temperatures. Lastly, various structural parameters exert a notable influence on the structure’s performance.

Study on the penetration resistance of a honeycomb composite structure coated with polyurethane elastomer

In this study, the ballistic performance of the composite structure was investigated and studied by experiment and finite element analysis in order to study the anti-penetration performance of a polyurethane elastomer-coated honeycomb sandwich construction. Six kinds of target plate structures with different configurations were prepared by changing the hard segment content and coating position of polyurethane elastomer. The first-stage light gas gun device is used to conduct impact experiments at various speeds, and the finite element simulation computation is performed using LS-DYNA. Based on the experimental and finite element results, the ballistic limit velocity and specific energy absorption of different target configurations were analyzed, and the failure forms, damage areas, and failure mechanisms were discussed. The findings demonstrate that the polyurethane elastomer coating enhances the honeycomb sandwich structure’s ballistic limit performance by 40.6% to 51% and that the honeycomb core of the target plate with the coating on the front panel has a larger area of collapse. This fully exploits the benefits of the honeycomb structure in the energy absorption process and makes up for the weaknesses of the honeycomb sandwich structure’s subpar energy absorption effect under local impact loads. Therefore, the front panel coating has better ballistic limit performance. The coated polyurethane with medium hardness demonstrated the best ballistic limit performance for the various polyurethane hardness. The ballistic limit speeds of the front panel and back panel coatings increased by 51% and 48.8% respectively, in comparison to the uncoated target plate. After comparing the structure of polyurea coating, it is found that the ballistic limit performance of polyurethane coating with medium hardness is higher than that of polyurea coating structure, and the negative growth of the ballistic limit performance of the whole structure caused by the coating of rigid polyurea on the back panel is effectively avoided.

Analysis of Hard Point Mechanical Behaviour Due to Variations of Potting Agent Volume on a Composite Sandwich Panel

Composite sandwich panels are widely used in lightweight structures, especially in aerospace, automotive, and marine industries. They are chosen mainly because of the superiority of their specific stiffness as compared to solid panels. Stingray, a solar car designed by the UiTM Eco-photon team, applied this technology for its lightweight property. However, the honeycomb sandwich constructions were susceptible to localized load. Thus, load attachment points using metal inserts, also known as ‘hard points’, were introduced. In this study, the behaviour of hard points based on three volume variations of the potting agent was investigated. ESA recommended static pull-out tests to be conducted on the sandwich panels composed of Nomex honeycomb core, two laminates of carbon fibres/epoxy composite as the face-sheets to determine the failure load of the hard points. A finite element simulation using ANSYS was also performed to determine the displacement of the inserts in presence of normal-to-plane load. The results include load versus extension curves obtained by both methods. Potting agents were found to elevate the stiffness and the strength of the inserts by some degree. Therefore, the application of these hard points on the solar car was found to be effective.

GEOMETRICAL OPTIMIZATION AND EXPERIMENTAL STUDY OF ALUMINUM HONEYCOMB SANDWICH CONSTRUCTION FORMWORKS

The technique innovation of construction formwork is of great importance in concrete engineering. The possibility of applying honeycomb sandwich structures to aluminum construction formwork was analyzed by computational and test methods. The equivalent elastic parameters of a honeycomb core structure were calculated based on Gibson’s theory, and then the stresses and deformation of the honeycomb sandwich construction formwork subjected to a uniformly distributed load were computed by using Reissner’s model. The geometrical parameters of the honeycomb sandwich structure were optimized under the deformation and constraint conditions according to the industry standard of aluminum construction formwork. Finally, the bending tests of the honeycomb sandwich aluminum construction formworks were conducted in which full-field three-dimensional deformation data were acquired by using a digital photogrammetric system. The test results are in a good agreement with that of the theoretical computation. It shows that the mass of the aluminum formwork can be reduced at least 60% after the application of honeycomb sandwich structures.

Strength Assessment of Fan Blade with Different Materials

Weight reduction of turbofan engines is one of the main concerns of aero engine manufacturers in order to cut fuel burn. To achieve higher fuel efficiency, aero engine manufacturers develop turbofans with higher bypass ratio, which can only be achieved with larger (and heavier) fan sections. This makes weight reduction in fan components a major consideration and becomes a key driver for the use of composite materials in future engines. The objective of this project is to design, perform structural analysis and optimization of a Composite fan blade. Development of a fan blade is comparable to a future large aircraft engine fan blade. This thesis is about the structural analysis of a composite fan blade with a honeycomb sandwich construction with a polymer matrix composite and honeycomb Aluminium core compared with baseline solid basic fan blade made of titanium. The focus of this work is to design the sandwich composite blade with honeycomb core and conduct static and dynamic analysis.

Investigating the effects of fluid intrusion on Nomex® honeycomb sandwich structures with carbon fiber facesheets

Abstract Honeycomb sandwich construction is commonly used in aircraft structures to make parts with a superior strength to weight ratio. Nomex® honeycomb core is used extensively for flooring, skin panels, fairings, engine cowlings, and flight controls. Honeycomb sandwich structures are prone to fluid ingression due to their thin facesheets which get damaged easily by impact or erosion. The purpose of this research was to determine how the mechanical properties of honeycomb sandwich structures were affected if the structure was saturated by a fluid such as water, fuel, hydraulic fluid, or engine oil. The authors focused on the lasting effect on the sandwich structure when aircraft fluids ingress into the structure. The test panels were made of carbon fiber prepreg, and they were bonded to a 12.7 mm thick Nomex® honeycomb core material. The specimens were soaked in water, fuel, hydraulic fluid, or engine oil for 45 days. After the soak period, the specimens were removed from the fluids and left to drain for 30 days. The specimens including the control group were tested with a four-point loading test and impact test in accordance with ASTM standards.

A spectral element for wave propagation in honeycomb sandwich construction considering core flexibility

Spectral elements are found to be extremely resourceful to study the wave propagation characteristics of structures at high frequencies. Most of the aerospace structures use honeycomb sandwich constructions. The existing spectral elements use single layer theories for a sandwich construction wherein the two face sheets vibrate together and this model is sufficient for low frequency excitations. At high frequencies, the two face sheets vibrate independently. The Extended Higher order SAndwich Plate theory (EHSaPT) is suitable for representing the independent motion of the face sheets. A 1D spectral element based on EHSaPT is developed in this work. The wave number and the wave speed characteristics are obtained using the developed spectral element. It is shown that the developed spectral element is capable of representing independent wave motions of the face sheets. The propagation speeds of a high frequency modulated pulse in the face sheets and the core of a honeycomb sandwich are demonstrated. Responses of a typical honeycomb sandwich beam to high frequency shock loads are obtained using the developed spectral element and the response match very well with the finite element results. It is shown that the developed spectral element is able to represent the flexibility of the core resulting into independent wave motions in the face sheets, for which a finite element method needs huge degrees of freedom.

Study on Finite Element Modeling Aspects of Delaminated Honeycomb Sandwich Beams

The simulation of damaged honeycomb sandwich structures is an important aspect in the structural health monitoring and prognosis. This paper studies finite element modeling aspects of delaminated honeycomb sandwich structure. The models proposed are 3-D model of the honeycomb sandwich construction using isotropic shell elements and a layered shell element model, both with contact elements defined in between the delaminated skin and core. Case study is conducted on damaged and undamaged metallic sandwich beam with 3-D shell element modeling and layered element modelling. The models are validated using three point bending test of damaged and undamaged beams. Results are compared with the experimental, theoretical and finite element results. The results show that the layered element modeling simulates the stiffness and gives the similar results to that of 3D model in the global responses and is computationally efficient.

Special features of diffusion bonding of three-layer titanium structures with a honeycomb filler

In this paper, research results of the OT4-1 alloy samples, simulating three-layered honeycomb sandwich constructions, are covered. It is established that the factors influencing the welding process and the diffusive junction quality are thicknesses of the skin and filler materials ratio.

A Study for the Characteristic Changes Under the Repeated Thermal Exposure in the Process of Repairing Aircraft Sandwich Structures

Delamination can be observed in the sound areas during and/or after a couple times exposure to the elevated curing temperature due to the repeated repair condition. This study was conducted for checking the degree of degradation of properties of the cured parts and delamination between skin prepreg and honeycomb core. Specimens with glass honeycomb sandwich construction and glass/epoxy prepreg were prepared. The specimens were cured 1 to 5 times at 260°F in an autoclave and each additionally exposed 50, 100 and 150 hours in the 260°F oven. Each specimen was tested for tensile strength, compressive strength, flatwise tensile strength and interlaminar shear strength. To monitor the characteristics of the resin itself, the cured resin was tested using DMA and DSC. As a results, the decrease of Tg value were observed in the specific specimen which is exposed over 50 hrs at 260°F. This means the change or degradative of resin properties is also related to the decrease of flatwise tensile properties. Accordingly, minimal exposure on the curing temperature is recommended for parts in order to prevent the delation and maintain the better condition.

Woodlike Properties from Carpet and Textile Fibrous Waste: Mitigating the Coming Landfill Crisis

Large-volume usage of textile and carpet fibrous waste may be achieved with a low-cost material that has woodlike properties. Formulations and properties of composites, laminates, and honeycomb sandwich constructions made from carpet and textile fibrous waste in a high-modulus phenol formaldehyde matrix are described. Using design parameters based on the mechanics of bending beams and the moduli of the fibrous component materials, one can achieve apparent bending moduli of 1 million psi (6.9 GPa) and bending strengths of 10, 000 psi (69 MPa). To achieve these woodlike properties, it is best to use waste carpet material in the core and higher-modulus textile materials such as cotton and polyester in the outer layers. About 20 wt.% phenolic resin is suggested for the matrix component.

Thermal Deformation Analysis of Honeycomb Sandwich Construction by using Honeycomb Model.

A simple method for thermal deformation analysis of a honeycomb sandwich construction (HSC), which is used as wall plates of buildings and mirror plates for parabolic antennas, was given. Orthotropic equivalent material properties are given theoretically by calculations with a periodical unit cell of honeycomb core. The theoretical thermal conductivities of the honeycomb core agreed with the value given by an experimental and computational hybrid system with thermal video system. A honeycomb model which has the theoretical material properties doesn't reduce the precision but significantly reduces the time for pre and post processes, and analyses.

Elastic-Plastic Analysis of Honeycomb Sandwich Construction by Using Honeycomb Model.

A simple method for structural analysis of honeycomb sandwich construction (HSC), which is used as light weight and high stiffness material, was given. It was shown that a rigidity of honeycomb material is very influential to the stiffness of HSC when HSC is subjected to bending load, and elastic and plastic moduli of rigidity are given by honeycomb parameters such as cell size and cell wall thickness. Therefore the authors proposed the finite element model for structural analysis of HSC, which can simulate the HSC deformed behavior without detailed hexagnal mesh. The analyses results given by proposed model agreed with the results of the experiment and the detaied meshing analyses. This model doesn't reduce the precision but reduce much time for pre-post processes and analyses.

CRITICAL AND COINCIDENCE FREQUENCIES OF FLAT PANELS

Critical and coincidence frequencies of panels are important in studying their behaviour under acoustic excitation. Most spacecraft structural panels are of honeycomb sandwich construction and many of them have face sheets made of composite material. The critical and coincidence frequencies of such panels are discussed here. Expressions for critical and coincidence frequencies of thick isotropic and thin as well as thick symmetric composite panels are derived. It is shown that the orthotropic behaviour and transverse shear flexibility of the panels affects the critical and coincidence frequencies. The critical frequency of a typical composite honeycomb sandwich panel obtained using the above expressions match well with experimental results.

Application of infrared thermography to detection of flaws in honeycomb sandwich constructions : Shiratori, M.; Qiang, Y.; Takahashi, Y.; Ogasawara, N. JSME International Journal, A. Vol. 37, No. 4, pp. 396–402 (1994)

Application of infrared thermography to detection of flaws in honeycomb sandwich constructions : Shiratori, M.; Qiang, Y.; Takahashi, Y.; Ogasawara, N. JSME International Journal, A. Vol. 37, No. 4, pp. 396–402 (1994)

Application of Infrared Thermography to Detection of Flaws in Honeycomb Sandwich Constructions

We have developed an experimental and computational hybrid system which can be applied to the detection of flaws in structural members. The system consists of an infrared thermal video system by which the temperature distribution of the body surface can be measured, and an engineering work station which carries out image processing of the thermograms

ＦＲＰハニカムサンドイッチ構造の耐熱性および耐アルカリ性

FRP honeycomb sandwich constructions are light and high rigidity members which have a good corrosion resistance. These constructions have been by many different molding methods and used for many appliances. So in this paper, we have examined the practical properties of FRP honeycomb sandwich constructions which are used for underground laid application. The practical properties examined were alkali (pH 12) resistance, the dependence of heat circumstance and freezing-hot water (60°C) heat cycle resistance. Especially fracture pattern and mechanism were considered in testing of alkali resistance. The results obtained confirmed that FRP honeycomb sandwich can be applied for the structural members of underground laid uses. From the flexural test after dipping test of high alkali solution, it was clarified that there are different fracture patterns (one or both side fracture of facing, shearing fracture of core and combination fracture of facing and core) of FRP honeycomb sandwich constructions.

ＦＲＰハニカムサンドイッチ構造の環境クリープ特性

Fiber reinforced plastic (FRP) materials composed of glass/unsaturated polyester (GF/UP) are used in many fields because of their good properties. In this paper, the fiber reinforced plastic honeycomb sandwich construction made of GF/UP composites was investigated to examine its applicability as structural parts for underground use by utilizing its high flexural rigidity and high corrosion resistance. The creep tests were carried out by dipping the pamples in alkali buffer solution simulating the condition of under-ground water. The creep properties of FRP honeycomb sandwich construction were examined in flexural mode. The fracture appeared in the flexural or shear mode pattern depending on the loading conditions. The experimental results clarified the creep properties of the material and provided an important information about creep design for the application of FRP honeycomb sandwich structure in underground water.

Optimum design of honeycomb sandwich constructions with buckling constraints

Optimum design of honeycomb sandwich constructions with buckling constraints is treated in this paper. Four modes of instability for honeycomb sandwich structures are considered in buckling constraints, including overall buckling, core shear instability, face wrinkling, and monocell buckling. The face thicknesses, core depth, cell wall thickness, and diameter of an inscribed circle in a honeycomb cell are taken as design variables. Eight-nodal quadrilateral honeycomb sandwich isoparametric shell elements and hybrid approximation techniques in combination with the dual solution are used. Some comparisons are also made between the cases with and without buckling constraints. Numerical results are given for four examples.

Use of modal energy distribution in the design of honeycomb sandwich decks

Through the example of a spacecraft equipment deck, which is generally made of honeycomb sandwich construction, it is shown that modal energy distribution can be used as an effective guideline in improving the deck's frequencies to meet the restrictions imposed upon it. The kinetic energy distribution is employed as a basis for redistributing various packages on the deck. Strain energy distribution is used to identify areas which can be stiffened by bonding ‘doublers’ on the face sheets and the doubler thickness is obtained from a sensitivity analysis.