Aluminium Sandwich Panels Research Articles

Finite element analysis of indentation of aluminium foam and sandwich panels with aluminium foam core

This paper presents modelling techniques for achieving convergent and accurate solutions in simulating quasi-static indentation of closed-cell aluminium foams and sandwich panels with aluminium foam core using the commercial finite-element software ABAQUS/Standard. Various indenters are utilised: hemispherical indenters of 10, 15 and 20mm diameter, a 16-mm cylindrical flat punch, and a long flat punch. The material parameters are established by comparison with the previous experimental results in uniaxial compression. Experimentally-observed tearing of the cell walls is accounted for in the simulations by introducing element failure and deletion criteria. Stress and strain analysis of the results reveals that foam failure occurs where cell tearing takes place. This occurs at critical tear energy and shear strength, independent of indenter size. The resulting load–displacement curves correlate closely with experimental results. The quasi-static indentation of sandwich panels of aluminium foam cladded with aluminium skins is also simulated for hemispherical indenters of diameter 5–20mm. Cell tearing does not occur until the point of failure and thus, is not accounted for in the simulations. The effect of the skin strength on the stiffness, strength and energy absorption of the panels is elucidated. A particular emphasis is placed on the material formulation for the foam core which would ensure convergence and reliable predictions.

GS17 サンドイッチパネルの損傷同定

This study proposes a method for identifying damages induced by an impact force acting on aluminum and CFRP sandwich panels with honeycomb core. The impact location and the impact history are identified using strain data measured by biaxial strain gauges. Experimental transfer matrices, which relate the impact force and the sensor response, are used to identify the force history. The present paper reveals that the impact damage in aluminum and CFRP sandwich panels can be estimated by the shape and the peak value of identified force history of the impact force.

Deformation characteristic of aluminum sheet/powders/aluminum sheet sandwich rolling process

The aluminum sheet/powders/aluminum sheet sandwich rolling process which was applied to manufacturing precursor of foam aluminum sandwich panel was put forward. The purpose of sandwich rolling was to obtain high densification precursor and bonding of metal face-sheet/powders interface. Compared with mold-compacting, powder densification process and deformation characteristic of interface were studied for the first time in the process of aluminum sheet/powders/aluminum sheet sandwich rolling. The experimental results show powder deformation is a continuous deformation process. Elastic deformation and plastic deformation were produced in powders, thus powders became lamellar structure under rolling pressure. Powders were compacted bonded and atomic force formed among the powders. Metal aluminum sheet exposed fresh metal surface under tensile rolling force. Powders near the interface filled the fresh surface of the metal face sheet and bonded each other.

Two-stage cumulative bending fatigue behavior for the adhesively bonded aluminum honeycomb sandwich panels

This study experimentally investigates two-stage cumulative bending fatigue behavior of adhesively bonded aluminum sandwich panels with local indentation failure mode. Experimental results show that the sums of cycle ratios of both stages are larger and less than unity when their loading sequence is low-to-high and high-to-low, respectively. The Miner’s rule fails to predict the loading sequence effect observed in cumulative fatigue tests. The variations in stiffness and residual strength of the studied specimens with the applied cycles in the constant-amplitude fatigue tests were also observed and recorded. Furthermore, the non-linear damage rule, which is based on the stiffness degradation of the specimens, provides better prediction of the remaining fatigue lives in the second stage than the traditional linear damage rule. However, the residual strength remains almost constant until the final stage of the constant-amplitude fatigue tests, demonstrating that residual strength is not a suitable indicator of non-linear damage in predicting the cumulative fatigue lives.

An equivalent material formulation for sinusoidal corrugated cores of structural sandwich panels

Metal sandwich panels with corrugated cores are an appealing industrial solution as structural components thanks to their high stiffness-to-mass ratio. Nevertheless, using detailed finite element models for numerical computation of their properties leads to large models and long solution time, especially for acoustic simulations. Therefore, reduction of the complex shaped core to an equivalent homogenous material is commonly used.In this paper, an innovative aluminum sandwich panel with sinusoidal corrugated core is investigated. The properties of the equivalent material are determined both analytically and numerically for the chosen Reissner–Mindlin orthotropic representation. The two derived models are compared in a comprehensive parametric study to validate the computationally much cheaper analytical formulation. Moreover, a validation of the equivalent models is done based on the bending stiffness per unit width of the sandwich panel. Finally, the acoustic behavior of the structure is investigated comparing the reduced layered model with the fully detailed 3D model.

Experimental Study of Sandwich Panels Subjected to Foam Projectile Impact

Similar blast loading characteristics can be obtained using impact of aluminium foam projectiles, which enables blast tests to be mimicked in a laboratory scale and in a safer environment. The purpose of this study is to determine the back-face deflection history of aluminium sandwich panels experimentally by aids of a laser displacement meter when panels are subjected to the impact of metal foam projectiles. This information was usually determined using finite element analysis (FEA) due to the difficulty in the experiment. The projectiles are cylindrical ALPORAS aluminium foam with diameter of 37 mm, length of 50 mm and nominal relative density of 10%. The sandwich panels consist of two 1 mm aluminium face-sheets and an aluminium honeycomb as the core. There are five different core configurations with a brand name of HEXCEL. The projectiles are fired towards the centre of the sandwich panels at different velocities using a gas gun. During the tests, a laser optical displacement measuring device is used to record the history of the back-face deflection experimentally. The deflection of the back-face is found to reach the maximum before coming to rest at a smaller value. The final back-face deflections of the sandwich panels show exponential relationship with the projectile impulse. The final deflections are compared with the deflection of monolithic plates with equal mass. The sandwich panels deflect less than the monolithic plate with an equal mass up to a critical value but continue to increase significantly afterwards. Care should be taken when using sandwich panels as protective structures against foam projectiles as beyond this point, the monolithic plates outperform the sandwich panels in absorbing the impact load.

Similitude study on bending stiffness and behavior of composite tubes

A procedure to design a composite tube that matches the flexural stiffness, load-carrying capacity, and energy absorption of an aluminum tube while subjected to bending load is of interest. The large deformation and energy absorption requirements are fulfilled through the progressive failure of the plies of suitable fiber orientations across the thickness of the tube. The layer wise nature of the composite tubes and cylindrical anisotropy, however, has impeded obtaining a simple closed-form solution for calculating the flexural stiffness. Available analytical solutions are mainly a complex set of equations, which should be solved simultaneously. In addition, the boundary and interface conditions between the adjacent plies must be satisfied. This article presents a straightforward simulation technique for this purpose. First, the tube is correlated to a corresponding composite sandwich panel, the flexural stiffness of which is obtained by the classical laminate theory. Then an analogous aluminum sandwich panel is designed and is correlated to a so-called ‘equivalent’ aluminum tube. The bending stiffness of the composite tube is shown to be the same as that of its equivalent aluminum tube. As a result, a complex problem of cylindrical anisotropy is mapped into a Cartesian coordinate system and solved via the classical laminate theory. The accuracy of the technique is verified by experimental work and analytical solutions. The agreement between the three methods is shown.

Design, development, and manufacture of an aluminium honeycomb sandwich panel monocoque chassis for Formula Student competition

Cardiff University students have used the freedom of the Formula Student rules to create an innovative chassis that combines a high performance with an efficient manufacturing process. All aluminium sandwich panels were pre-cut using computer numerical control routing, which is a rapid low-cost operation that produced highly accurate results. Assembling the monocoque consisted of folding and bonding panels along pre-routed lines and reinforcing the relevant joints. This required no specialist tools or equipment and was a rapid non-labour-intensive operation. The key design features, the manufacturing techniques, and the results of experimental and computational performance testing are presented here. This chassis construction technique is the result of research and development for seven years over six generations of Formula Student race cars.

Wet-sand impulse loading of metallic plates and corrugated core sandwich panels

We have utilized a combination of experimental and modeling methods to investigate the mechanical response of edge-clamped sandwich panels subject to the impact of explosively driven wet sand. A porthole extrusion process followed by friction stir welding was utilized to fabricate 6061-T6 aluminum sandwich panels with corrugated cores. The panels were edge clamped and subjected to localized high intensity dynamic loading by the detonation of spherical explosive charges encased by a concentric shell of wet sand placed at different standoff distances. Monolithic plates of the same alloy and mass per unit area were also tested in an identical manner and found to suffer 15–20% larger permanent deflections. A decoupled wet sand loading model was developed and incorporated into a parallel finite-element simulation capability. The loading model was calibrated to one of the experiments. The model predictions for the remaining tests were found to be in close agreement with experimental observations for both sandwich panels and monolithic plates. The simulation tool was then utilized to explore sandwich panel designs with improved performance. It was found that the performance of the sandwich panel to wet sand blast loading can be varied by redistributing the mass among the core webs and the face sheets. Sandwich panel designs that suffer 30% smaller deflections than equivalent solid plates have been identified.

Static Performance of Hot Bonded and Cold Bonded Inserts in Honeycomb Panels

An investigation on the structural performance of inserts within honeycomb sandwich panels is presented. The investigation considers metallic inserts in all aluminum sandwich panels and emphasis is placed on the structural performance difference between hot bonded and cold bonded inserts. The former are introduced during panel manufacture while the latter are potted into existing panels. The investigation focuses on the static performance of the two insert systems subject to loads in the normal direction to the facing plane. The experimental part of the work presented involved carrying out pullout tests on hot bonded and cold bonded reference samples by loading them at a centrally located insert. The experimental results were compared with results from an analytical model and results from a finite element model. Contrary to what was expected it was found from the experiments that the cold bonded inserts outperformed the hot bonded inserts in terms of load carrying capability. From the finite element study it was found that this was mainly due to the difference in stiffness of the different filler materials used in the two insert systems.

Impact Damage and Energy-absorbing Characteristics and Residual In-plane Compressive Strength of Honeycomb Sandwich Panels

An experimental study of the in-plane compressive behavior of both aluminium and nomex composite sandwich panels with 8 ply carbon/epoxy skins was conducted. All sandwich panels were impact-damaged with a range of impact energies from 1 to 55 J. Dominant damage mechanisms were found to be core crushing, skin delamination, and fracture with the former two absorbing most of the impact energy. While the intact panels failed in region close to one loaded end, all the impact-damaged nomex panels failed around the mid-section region. Two thirds of the aluminium panels also failed in the mid-section region and one third failed in the loaded end region. The presence of the core played a unique role in in-plane compression with a substantial stabilizing support to the skins, which counteracted the deleterious effect of impact damage. The in-plane compressive behavior has shown the combined effects of impact damage and the core in a complex manner.

The localized low-velocity impact response of aluminium honeycombs and sandwich panels for occupant head protection: experimental characterization and analytical modelling

This paper describes an investigation into the localized impact response of aluminium honeycombs and sandwich panels from the perspective of their use in occupant head protection applications. A programme of quasi-static and dynamic low-velocity impact testing using a hemispheric ‘head form’ impactor is described. From this, design data is presented in terms of acceleration histories and head injury criterion values. Furthermore, a simple analytical model is described for predicting acceleration histories for preliminary design purposes.

Low-velocity impact failure of aluminium honeycomb sandwich panels

Abstract In this paper, the failure response of aluminium sandwich panels subjected to low-velocity impact is discussed. A three-dimensional geometrically correct finite element model of the honeycomb sandwich plate and a rigid impactor was developed using the commercial software, ABAQUS. This discrete modelling approach enabled further understanding of the parameters affecting the initiation and propagation of impact damage. Strain-hardening behaviour of the aluminium alloys and the honeycomb core density were shown to affect the impact response. In addition, the impulse–momentum equation was incorporated into the energy-balance model, so that the impact force and deflection histories could be determined as well.

Failure analysis of an aluminum sandwich panel skin from the space shuttle Columbia

A failure analysis was carried out on the skin of a 2000-series aluminum sandwich panel from the space shuttle Columbia. Light optical microscopy and scanning electron microscopy were used in determining the mode of failure. Analysis of the fracture surface indicated that the skin failed intergranularly. Second-phase particles present in the microstructure liquefied upon heating and subsequently wet the aluminum grain boundaries. The skin was shown to have failed by the liquation of the iron- and manganese-rich particles only along the edges of the failed panel, suggesting that local heating—termed “hotspots”—was the cause of failure of the aluminum sandwich panel.

알루미늄 샌드위치 패널의 구조적 형상 및 진동 특성에 관한 연구

Aluminum honeycomb sandwich panel (AHSP) not only have high flexural rigidity and strength per density but also excellence in anti-vibration and anti-noise properties. Their properties are very useful for build airplane and high speed crafts, which need lighter-weighted and more strengthed element. Recently, the AHSP is regarded as a promising strength member of light structures like the hull of high speed crafts. Generally, the core shape of aluminum sandwich panel (ASP) is the hexagonal shape of honeycomb. But, in this paper, authors proposed the ASP with pyramid core, as the ASP model of new type, and analysed the structural and vibrational characteristics for aluminum pyramid sandwich panel (APSP) as this new ASP type, according to the thickness variation of core and face, the height variation of core. The applied sandwich models have isotropic and symmetrical aluminum faces and pyramid cores. And, the applied boundary conditions are simple, fixed and free support.

The strength characteristics of aluminum honeycomb sandwich panels

Aluminum sandwich construction has been recognized as a promising concept for structural design of lightweight transportation systems such as aircraft, high-speed trains and fast ships. The aim of the present study is to investigate the strength characteristics of aluminum sandwich panels with aluminum honeycomb core theoretically and experimentally. A series of strength tests are carried out on aluminum honeycomb-cored sandwich panel specimen in three point bending, axial compression and lateral crushing loads. Simplified theories are applied to analyze bending deformation, buckling/ultimate strength and crushing strength of honeycomb sandwich panels subject to the corresponding load component. The structural failure characteristics of aluminum sandwich panels are discussed. The test data developed are documented.

On the new Generator Hut for JARE-'65

A strong new generator hut which will become the heart of Japanese Antarctic Research Expedition's Showa Base was complated recently.The generator hut has a floor space of 68.8 square meters and contains two 45 KVA generators, an ice melting tank and a hat bath.The hut, which is the first step toward making the Japanese Antarctic base a permanent one, was made according to the multipurpse building and assembling method a new technique developed by the Takenaka Building Research Institute in Tokyo.The generartor hut is oval shaped and is made mostly of aluminium sandwich panels. It has been designed so that seven or eight men can easily construct it on very rough terrain.It is an assembly type structure weighing a total of seven tons.Since it will be the heart of life in Antarctic base, heaviest emphasis was placed on resistance to fire and cold.It has been designed to withstand maximum winds of 60 meters per second (134 miles per hour) and temperatures of 45 degrees below zoro centigrade.