Aluminum Honeycomb Sandwich Structures Research Articles

Experimental study on compression properties of composite aluminum honeycomb sandwich structures

AbstractThe 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.Highlights 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.

Investigating the Excellence of Different Thermography Approaches to Subsurface Dis-bonds Detection in Aluminum Honeycomb Sandwich Structures

Investigating the Excellence of Different Thermography Approaches to Subsurface Dis-bonds Detection in Aluminum Honeycomb Sandwich Structures

Mechanical behaviour of hybrid FFRP/aluminium honeycomb sandwich structures

The combination of lightweight properties and high energy absorption capacity makes sandwich structures suitable for applications in transportation industry, such as automotive, aerospace, and shipbuilding industry. In these fields, the gas emissions reduction, fuel saving, vehicle safety and load capacity increase are currently important requirements. This research deals with the study of the mechanical behaviour of a “green” hybrid honeycomb sandwich structure made by an aluminium honeycomb core and flax fibres reinforced skins. Specific interest has been addressed to their mechanical behaviour in terms of bending properties and low-velocity impact response. For the impact tests, two indenters having hemispherical geometry with a diameter of 10 mm (H10) and 20 mm (H20) were selected. The results were compared with other hybrid structures analysed in previous studies. The static three-point bending tests produced different collapse modes, depending on the support span distance. Non-destructive evaluation was carried out for failure mode analysis by optical microscopy and digital radiography (DR). In the aluminium-flax hybrid sandwich structures it is found an increase in the impact strength of 25 % compared to the unreinforced aluminium honeycomb sandwich structures. In terms of specific energy absorption (SEA), it is interesting to underline an increase of 50 % compared to traditional AHS structures.

The Out-Of-Plane Compression Behavior of In Situ Ethylene Vinyl Acetate (EVA)-Foam-Filled Aluminum Honeycomb Sandwich Structures.

In this study, the mechanical behavior of aluminum honeycomb (AHC) sandwich structures filled with ethylene vinyl acetate copolymer (EVA) foam in situ under out-of-plane compression loading was investigated experimentally. Both non-filled and EVA-foam-filled sandwich specimens with three different AHC core cell sizes (5.20, 6.78, and 8.66 mm) were studied to correlate the foam-filling effect with a key structural parameter. The results showed that compression characteristic properties such as peak stress, plateau stress, and absorbed energy per unit volume of the sandwich structure increased with EVA foam filling. The structure showed high recoverability when the compression loading was removed due to the viscoelastic nature of EVA foam. Cored EVA sandwich with 8.66 mm AHC cell size was recovered at 44% of the original thickness. This result promises groundbreaking applications such as impact-resistant and self-healing structures. The microstructures were also observed using scanning electron microscopy (SEM) to investigate the failure and the recoverability mechanisms.

Effects of polymethacrylimide foam reinforced aluminum honeycomb sandwich under quasi‐static compression

AbstractIn 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.

Bending performance of carbon fiber–reinforced polymers/aluminum sandwich structure with different forming process and analysis of failure mode

This paper aims to study the failure response of carbon fiber–reinforced polymers (CFRP)/aluminum honeycomb sandwich structures facing three-point bending test by combining the experiments and numerical models. The theoretical model of three-point bending is established by the finite element software ABAQUS to predict the damage, and then verified by experiments. In order to study the bending performance of sandwich structures made by different forming processes, the test was carried out on sandwich panels with two different molding processes, which are secondary bonding and co-curing. The failure mode and failure mechanism of sandwich structures were also studied by testing specimens with different panel thicknesses and core heights. The results shows that the specimens of the secondary bonding molding process are more prone to damage, most of the samples were observed to be debonded after the test, and the peak load is lower than that of the co-curing. Three different failure modes, closely related to the damage length of the core, which are greatly influenced by different parameters, were observed for the co-cured specimens during the test and parametric studies were carried out for the co-cured specimens. The results showed that small damage length makes it easier to form type I failure mode, while the type II failure mode is more likely to form in situations when the damage length is larger.

Performance of honeycomb sandwich structure under combined blast and impact of fragments

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.

Stress–Strain Assessment of Honeycomb Sandwich Panel Subjected to Uniaxial Compressive Load

The ship hull structure is composed of plates and stiffened panels. Estimating the maximum load-carrying capacity, or the ultimate strength, of these structural components is fundamental. One of the main challenges nowadays is the implementation of new materials and technologies to enhance the structural integrity, economy, safety and environmentally friendly design of the ship’s hull structure. A new design solution may be represented by aluminium alloy honeycomb sandwich structures, both as plane panels or stiffened ones, which are characterised by excellent impact-absorption capabilities and a high stiffness-to-weight ratio. Still, their response to some conditions typical of ship structural design needs to be deeply investigated. Axial compressive loading is one of the most critical conditions that could impact the structural integrity of such light-weight solutions. Hence, the uniaxial compressive behaviour of aluminium honeycomb sandwich structures has to be deeply investigated to promote their integration in ship structural design. Within this context, the present work performs an experimental and numerical study of a honeycomb sandwich panel subjected to uniaxial compressive loads. The results will help develop models for predicting the uniaxial compressive load-carrying capacity of hybrid honeycomb sandwiches of aluminium alloy design.

Residual Compressive Strength of Aluminum Honeycomb Sandwich Structures with CFRP Face Sheets after Low-velocity Impact

Residual Compressive Strength of Aluminum Honeycomb Sandwich Structures with CFRP Face Sheets after Low-velocity Impact

A comparative study on the ballistic performance of aramid and aluminum honeycomb sandwich structures

This study investigated the perforation phenomenon of aramid and aluminium honeycomb sandwich structures under high-velocity impacts and compared the impact responses experimentally and numerically. The dimension of the face sheets used was 1 mm in thickness and 220 mm in diameter, and for both the honeycomb cores, the cell thickness of 0.05 mm and the cell size of 3.2 mm was used. Ballistic impact tests were conducted by employing a pneumatic air gun to study damage behavior and failure modes under different impact velocities between 35 m/s and 150 m/s using conical shaped and hemispherical shaped projectiles.Three-dimensional finite element models were implemented in ABAQUS/Explicit to model sandwich panels.The numerical model was validated with experimental data and, subsequently, the numerical study was further extended to study the effects of different geometrical parameters affecting the impact response of sandwich structures. The results showed that for the ballistic limit, sandwich structure having an aluminium honeycomb core performed better than the aramid honeycomb core by 3.09% and 2.5% against conical and hemispherical projectiles, respectively. However, the aramid honeycomb structure was proven to be more efficient than the aluminum honeycomb structure in terms of energy absorption and specific energy absorption.

Design and fabrication of aluminum honeycomb sandwich structures by atmosphere protect brazing: Microstructural evolution and mechanical behavior

Aluminum honeycomb sandwich structures with robust interfacial bonding and great mechanical response were fabricated by atmosphere protect brazing technique. The key brazing parameters (brazing temperature, holding time) were investigated and the correlations between interfacial microstructure evolution and mechanical behavior were addressed. Suitable brazing parameters (600 °C-15 min) could not only minimize the deterioration of high thermal cycle on the performance of joints including grain coarsening and over-burning of core walls, but also provide excellent interface metallurgical bonding. Additionally, the dominant failure mode of brazed aluminum honeycomb sandwich structures was core buckling rather than skin-core debonding. This study provides a reliable and efficient method to enhance interfacial bonding and overall performance of honeycomb sandwich structures.

Experimental Study on Static and Dynamic Response of Aluminum Honeycomb Sandwich Structures.

Honeycomb aluminum structures are used in energy-absorbing constructions in military, automotive, aerospace and space industries. Especially, the protection against explosives in military vehicles is very important. The paper deals with the study of selected aluminum honeycomb sandwich materials subjected to static and dynamic compressive loading. The used equipment includes: static strength machine, drop hammer and Split Hopkinson Pressure Bar (SHPB). The results show the influence of applied strain rate on the strength properties, especially Plateau stress, of the tested material. In each of the discussed cases, an increase in the value of plateau stresses in the entire strain range was noted with an increase in the strain rate, with an average of 10 to 19%. This increase is mostly visible in the final phase of structure destruction, and considering the geometrical parameters of the samples, the plateau stress increase was about 0.3 MPa between samples with the smallest and largest cell size for the SHPB test and about 0.15 MPa for the drop hammer test.

Design and Fabrication of Aluminum Honeycomb Sandwich Structures by Atmosphere Protect Brazing: Microstructural Evolution and Mechanical Behavior

Design and Fabrication of Aluminum Honeycomb Sandwich Structures by Atmosphere Protect Brazing: Microstructural Evolution and Mechanical Behavior

Aluminium honeycomb sandwich as a design alternative for lightweight marine structures

ABSTRACT Weight reduction and materials sustainability are becoming of primary importance for marine structures. A solution to both issues could lie in the application of all-metal sandwich structures. The study suggests the substitution of common marine structures with aluminium honeycomb sandwich structures (AHS), as a green and lightweight alternative, through a new methodology for structure comparison and design. Comparisons were based on bending stiffness equivalence and its relation to other design parameters, used to produce materials charts. A graphical approach based on plots of stiffness requirements, weight reduction goal and failure modes was applied for the identification of the main design variables. The feasibility and effectiveness of the developed approach was illustrated by outlining an example regarding the substitution of a GFRP-based ship balcony overhang with an equivalent AHS. The results showed the possibility to significantly reduce the weight, leave the geometry almost unchanged, and improve the mechanical response.

Finite Element Analysis of Heat Transfer Behaviors of Aluminum Honeycomb Sandwich Structures

Honeycomb sandwich structures show excellent heat-shielding performance. This paper studies heat transfer mechanisms of aluminum honeycomb sandwich structures by finite element analysis. The heat conduction/radiation coupling relationship is considered, where the transient first-order heat conduction governing equation is used to describe the relationship between the temperature change and the external heat source, and the heat radiation is formulated by the Stefan–Boltzmann governing equation that describes the relationship between the effective radiation and the temperature field. Thus, the coupling relationship is represented by the imposition of heat source due to radiation as the boundary condition on the heat conduction equation. The finite difference algorithm is used to solve the temperature distribution of structures. Effects of geometry parameters and boundary conditions on the temperature field of structures are explored. Numerical results by ABAQUS software demonstrate the advantage of honeycomb structures in area of heat shielding.

Mechanical behavior of aluminum honeycomb sandwich structures under extreme low temperature conditions

The current study is an effort to characterize the mechanical response of panels that are used as structural elements at low temperature applications. For the above reason, plaques of aluminum honeycomb sandwich were exposed for a certain period of time at different low temperature profiles ranging from 23°C to -70°C so that possible variation of their mechanical properties due to temperature exposure to be justified. Four different temperatures namely 23°C, 0°C, -40°C and -70°C were applied to these plaques prior mechanical testing that was performed at different loading modes. Specimens were obtained from these plaques in order to study the effect of low temperature on mechanical behavior and damage response of the specific sandwich structures. Extensive mechanical testing was carried out by means of tensile, compression and bending loading and the respective mechanical properties occurring from these tests were determined. From the results occurring from experimental data obtained from mechanical testing it is evident that there is a moderate decrease of ultimate strength and yield strength of the material as service temperature decreases in tensile, edgewise and flatwise compression as well as in three point bending loading modes. Moreover a drop in temperature results in a decrease in strain at rupture at tensile and compression loading.

Collapse modes of aluminium honeycomb sandwich structures under fatigue bending loading

Abstract Aluminium honeycomb sandwich panels are an interesting lightweight structural solution for several applications such as marine structures, aerospace, automotive and aeronautics. In many of these applications, in-service conditions produce fatigue loadings: as a result, safer use of aluminium honeycomb sandwich structures requires a deep knowledge of their fatigue response, which was seldom studied in previous literature. The aim of the current study is to evaluate the fatigue response of aluminium honeycomb sandwich panels subjected to three-point bending loading conditions. The experimental investigation was performed on a commercial aluminium honeycomb sandwich structure with an overall thickness of 11 mm. A preliminary static analysis was performed both under three and four point bending conditions. The static tests allowed the identification of the static bending strength and the absence of a significant strain rate influence. Crashworthiness parameters were evaluated and a slight better performance was found under four point bending. The combination of static tests with Computed Tomography analysis resulted in the observation of the phenomena involved in static bending response of aluminium honeycomb sandwich structures, which are mainly dependent on cell walls buckling. Fatigue tests were conducted under three-point bending conditions. The influence of boundary conditions on fatigue life and on collapse modes were investigated by considering different supports spans. For one condition the S-N curve was obtained and its equation was compared to literature results. Two different collapse mechanisms were observed depending on the supports span: for larger supports span a fracture of the tensioned skin was observed, whereas lower supports span produced core shear. The former mode differed significantly from static failure with the same boundary conditions. In both cases, failure occurred suddenly and this should be taken into consideration in industrial applications. An analytical model was applied to predict fatigue collapse modes and limit loads. A fatigue failure map describing the relationship between supports span, collapse modes and fatigue limit loads was obtained, in order to provide a quantitative tool for aluminium honeycomb sandwich structures design. The fatigue failure map was able to accurately predict the experimental results.

Effect of structural parameters on low-velocity impact behavior of aluminum honeycomb sandwich structures with CFRP face sheets

This paper systematically investigates the low-velocity impact response and resulting damage behavior of aluminum honeycomb sandwich structures with carbon fiber reinforced plastic (CFRP) face sheets by combining the experimental and numerical methods. Low-velocity impact tests are conducted to determine and quantify the effects of structural parameters, such as face sheet thickness, cell wall thickness, honeycomb core height and hexagon side length, on the impact load, energy absorption, and failure mode. To further elucidate the impact behavior, a user VUMAT subroutine is developed to predict the progressive failure behavior of composite face sheets. Numerical simulation is performed to characterize the impact response and explore the deformation/failure mechanisms. The predicted impact load, energy absorption, contact time and failure mode agree well with measured counterparts. These studies reveal the face sheet thickness has particularly significant influence on the impact resistance performance of honeycomb structures. Cell wall thickness and side length of honeycomb core have notable effect on the impact load and structural stiffness of such structures, while which do not play a great role in energy absorption. Increase in core height has comparatively little effect on initial stiffness and energy absorption but makes the second peak loads decreasing for the perforation cases.

A sustainable approach of damping treatment for aluminium honeycomb sandwich structures

The damping plays a vital role in structural dynamic and acoustic performance of aluminium honeycomb sandwich structures. The viscoelastic damping treatment of skins is most common. An alternative, the use of sustainable cork inserts to improve the damping of cores and the whole assembly is investigated in this study. Structures with different filling degrees are analysed, as well as the optimum location for inserts is determined. The structural dynamic as well as the vibro-acoustic performance is estimated numerically. Average squared displacement amplitude reduction efficiency [Formula: see text] is defined as the target parameter for structural dynamic performance, whereas average transmission loss effectiveness [Formula: see text] is designed for vibro-acoustic performance. The structural dynamic models are validated by experimental vibration analysis, whereas the vibro-acoustic models are validated against published data. Different ways of bonding the inserts to the host structure are analysed in order to maximise damping. The highest improvement is obtained with a filling degree of 64% honeycomb voids and 9.76% increase in mass, for which an average squared displacement amplitude reduction of 35.25% and an average increase in transmission loss of 1.5 dB is achieved. The transmission loss increase in relation to the added mass is much higher than that achieved by doubling of mass in the mass law region. The introduction of cork inserts spreads the energy in local modes to a larger space, effectively decreasing the resonance amplitudes. Interestingly, damping does not increase with the number of inserts in a monotonic way and the improvement depends on the spatial distribution of inserts.

Finite Element Analysis of Dynamic Mechanical Responses of Aluminum Honeycomb Sandwich Structures Under Low-Velocity Impact

Honeycomb sandwich structures, composed of many regularly arranged hexagonal cores and two skins, often show excellent impact performance due to strong energy absorption ability under impact loads. This paper studies dynamic mechanical responses of aluminum honeycomb sandwich structures. Parametric geometry modeling using UG software and finite element analysis using ANSYS explicit dynamics module are performed. Finite difference algorithm based on time-stepping integration is used to get the impact displacement, and stress and strain with time. Effects of different impact velocities, core length and wall thickness on the distributions of plastic stress and strain are also explored. Results show that thinner honeycomb side length and thicker wall thickness lead to stronger impact resistance. This research provides theoretical support for promoting optimal design of lightweight structures against impact loads.