Porous Aluminum Foam Research Articles

Development on Preparation Technology of Aluminum Foam Sandwich Panels

Abstract Aluminum Foam Sandwich (AFS) panels consist of a highly porous aluminum foam core and metal face sheets. They have been known as a new functional material with many excellent comprehensive properties. AFS panels not only have many excellent properties of aluminum foam materials (extremely low density, efficient capacity of energy dissipation, high specific strength and specific stiffness, acoustic and thermal insulation, high damping, etc.), but also solve the shortcoming of low strength of single aluminum foams, which makes them interesting for a number of practical applications, such as the realization of lightweight structures with a high mechanical strength and a good capacity of energy dissipation under impacts. So far, they have received a considerable attention from a great number of researchers. In this work, the development of the preparation method of AFS panels was reviewed, and the merits and faults of different processes were discussed.

X線CTを用いたシンタクティックフォーム/アルミニウムフォーム相互浸透複合材料の圧縮変形挙動の解析

Interpenetrating phase composites (IPCs), in which each phase forms a 3-dimentionally interconnected network, show a new class of reinforcement morphology. In this study, syntactic foams, which are made of hollow glass microspheres embedded in a polymer matrix, are reinforced with open-cellular porous aluminum foams. Both deformation behavior and a strengthening mechanism of the syntactic foam/aluminum foam IPCs (SF/AF IPCs) are investigated with the help of an X-ray Computed Tomography (X-ray CT). Deformation behavior of the aluminum foam in the SF/AF IPC during compressive deformation is observed by the X-ray CT. The von-Mises stress distribution in the aluminum foam under compression was simulated by a finite element method for both the aluminum foam alone and the SF/AF IPC. High von-Mises stresses are detected in a layer with a relatively higher porosity of aluminum foam alone. Cell edges in the aluminum foam of the SF/AF IPC are fractured in the perpendicular direction to the compressive direction.

A two-scale micromechanical model for aluminium foam based on results from nanoindentation

The main aim of this paper is to develop and verify simple but effective model for elastic properties of a porous aluminium foam system and to compare results received from experimental micromechanics with solutions given by analytical or more advanced numerical methods. The material is characterized by a closed pore system with very thin but microscopically inhomogeneous pore walls (∼0.1mm) and large air pores (∼2.9mm). Therefore, two material levels can be distinguished. The lower level of the proposed model contains inhomogeneous solid matter of the foam cell walls produced from an aluminium melted with admixtures. Elastic parameters as well as volume fractions of microstructural material phases at this level are assessed with nanoindentation and effective properties computed via analytical and numerical homogenization schemes. The effective Young’s modulus of the cell walls was found close to 70GPa irrespective to the used homogenization procedure.The higher model scale contains homogenized cell walls and a significant volume fraction of air voids (91.4%). Since analytical schemes fail to predict effective properties of this highly porous structure, numerical homogenization based on a simple two dimensional finite element model is utilized. The model geometry is based on foam optical images from which an equivalent beam structure is produced using Voronoi tessellation. Effective foam Young’s modulus was found to be 1.36–1.38GPa which is in relation with ∼1.45GPa obtained from uniaxial compression experiments.

New Aluminum Foam/Polyformaldehyde Interpenetrating Phase Composites Prepared by Injection Molding

A new type of interpenetrating phase composite was formed by filling 70%-porous open-cell aluminum foam with polyformaldehyde through injection molding process. The results showed that both mechanical properties and tribological behavior of composites were improved. The interphase behaviour of aluminum foam/polyformaldehyde composites was examined by scanning electron microscopy(SEM).The worn surfaces of composites were also examined and discussed. It could be indicated that injection molding and Al foam surface preprocessing including both alkaline wash and KH550 treatment for Al foam/ POM composites was available. The new composite could be used where moderate strength and wear properties are needed.

Analysis of the Influence of Static Flow Resistance on the Sound Absorption Properties of Aluminum Foam

For the complexity of the internal microstructure of porous aluminum foam, on the basis of Rayleigh-Kirchhoff circular tube model, taking viscosity loss and thermal transmission, the paper establishes a simplified theoretical model for sound absorption properties of aluminum foam. The paper also calculates and analyzes the influence of Static flow resistance on the sound absorption properties in the rigidity and cavity backing. The results show that the peak frequency moves to lower with the increasing of the thickness of the air layer. What’s more, there is a direct corresponding relation between flow resistance and the best sound absorption frequency range of aluminum foam. In a reasonable range of flow resistance value, the capability of sound absorption reach optimal, Aluminum Foam won’t have fine sound absorption capability if the value of flow resistance is too big or small.

310 ポーラス金属の圧延特性と塑性構成式の検討

Three porous metals, i.e., lotus-type porous copper, aluminum foam, and open-cell type porous nickel, were subjected to multi-pass cold rolling. At the beginning, thickness reduction was mostly converted to volumetric change, while after heavy rolling, elongation in the rolling direction became remarkable. It is found that strain ratio of elongation to thickness, i.e., 'elongation efficiency', increases with decreasing porosity. The trend is sensitive to neither initial porosity nor pore morphology. It can be described with Shima's eq. for sintered metals using modified constants.

Characterization of aluminum foam–polypropylene interpenetrating phase composites: Flexural test results

A type of interpenetrating phase composites was formed by impregnating 90%-porous open-cell aluminum foam with polypropylene through an injection molding process. Three aluminum foams were used having three distinct linear pore densities: 10, 20 and 40 pores per inch (ppi) or roughly 4, 8 and 16 pores per cm. Samples taken from these composites were tested for flexural strength and stiffness based on ASTM D790-03. Flexural modulus and strength of the composite are compared to those of unreinforced polypropylene. The results showed, in general, the combination of the polymer and metal foams to be stiffer than either of the two individual components. The stiffness of the composites was found to increase with decreasing pore size. The smaller pore size allowed more cells to exist across the thickness of the specimen, and thus increased the bending stiffness of the composite.

Aluminium Foam Sandwich Panels: Manufacture, Metallurgy and Applications

AbstractSandwich panels consisting of a highly porous aluminium foam core and aluminium alloy face sheets are manufactured by roll‐bonding aluminium alloy sheets to a densified mixture of metal powders – usually Al‐Si or Al‐Si‐Cu alloys with 6–8% Si and 3–10% Cu – and titanium hydride, and foaming the resulting three‐layer structure by a thermal treatment. We review the various processing steps of aluminium foam sandwich (AFS) and the metallurgical processes during foaming, compare the process to alternative ways to manufacture AFS, e.g. by adhesive bonding, and give an overview of the available literature. Two ways to treat AFS after foaming are presented, namely forging and age‐hardening. Some current and potential applications are described and the market potential of AFS is assessed.

Vertebroplasty

This is an experimental study on an artificial vertebra model and human cadaveric spine. Characterization of polymethylmethacrylate (PMMA) bone cement distribution in the vertebral body as a function of cement viscosity, bone porosity, and injection speed. Identification of relevant parameters for improved cement flow predictability and leak prevention in vertebroplasty. Vertebroplasty is an efficient procedure to treat vertebral fractures and stabilize osteoporotic bone in the spine. Severe complications result from bone cement leakage into the spinal canal or the vascular system. Cement viscosity has been identified as an important parameter for leak prevention but the influence of bone structure and injection speed remain obscure. An artificial vertebra model based on open porous aluminum foam was used to simulate bone of known porosity. Fifty-six vertebroplasties with 4 different starting viscosity levels and 2 different injection speeds were performed on artificial vertebrae of 3 different porosities. A validation on a human cadaveric spine was executed. The experiments were radiographically monitored and the shape of the cement clouds quantitatively described with the 2 indicators circularity and mean cement spreading distance. An increase in circularity and a decrease in mean cement spreading distance was observed with increasing viscosity, with the most striking change occurring between 50 and 100 Pas. Larger pores resulted in significantly reduced circularity and increased mean cement spreading distance whereas the effect of injection speed on the 2 indicators was not significant. Viscosity is the key factor for reducing the risk of PMMA cement leakage and it should be adapted to the degree of osteoporosis encountered in each patient. It may be advisable to opt for a higher starting viscosity but to inject the material at a faster rate.

Metallic foams: Radiative properties/comparison between different models

The aim of this study is to determine the radiative properties, which are the extinction coefficient, the scattering albedo and the scattering phase function, of highly porous open-cell aluminium foam, using more-or-less simple predictive models, and to compare all these models. The radiative properties are predicted using geometric optics laws to model the interaction of radiation with the particles forming the foam. Moreover, the particles forming the foam are large compared with the considered wavelength and are supposed to be sufficiently distant from each other to scatter radiation independently. Thus, the radiative characteristics of the foam can be determined by adding the contributions of each particle. A particular attention is paid on microstructure analysis and modelling. We considered different kinds of cell shapes and struts cross-section, using microscopic and tomographic analysis. Furthermore, a new phase function modelling is presented. Finally, we compare the results of each method with the radiative properties obtained from experimental measurements of directional and hemispherical transmittances and hemispherical reflectance.

Combined electrochemical and biological treatment of industrial wastewater using porous electrodes

AbstractZn2+, Ni2+ and propylene glycol methyl ether were simultaneously removed from simulated wastewater in a column consisting of an aerated packed bed and an electrochemical cell with a porous aluminium foam cathode and a porous stainless steel anode. After 48 h of sole electrochemical treatment at a liquid rate of 0.00183 m3 m−2 s−1, Zn2+ and Ni2+ were reduced by 95 and 80% respectively. In the turbulent flow regime with liquid rates varied from 0.0137 to 0.0366 m3 m−2 s−1, both Zn2+ and Ni2+ removal decreased by about 15% rather than increased as expected for a mass transfer‐controlled process. This can be attributed to bubble formation at the cathode surface under turbulent flow, which led to a lower active surface area for the electrodeposition of metal ions. Porous electrodes enhanced the metal removal by 17 and 60% for Zn2+ and Ni2+ respectively as compared with flat plate electrodes. Using combined biological and electrochemical treatment at a water rate of 0.00183 m3 m−2 s−1 and an air rate of 0.0518 m3 m−2 s−1, 99% of Zn2+ and 95% of Ni2+ were removed. In addition, the 5 day biological oxygen demand (BOD5) was reduced by 58% concurrently over 72 h of treatment. Copyright © 2006 Society of Chemical Industry

Producing Technology of Aluminum Foam from Machined Chip Waste

The present study focuses on the investigation of the possibility of producing aluminum foam from low cost machined chip waste. To produce highly porous aluminum, manufacturing process of precursor, the effect of TiH2 content and the effect of ceramic particle addition were examined. In the study of precursor manufacturing processes, precursors fabricated by extrusion process did not expand sufficiently and the pore morphology was very irregular. In contrast, precursors fabricated by compressive torsion processing satisfactorily expanded and the pore morphology was uniform. There was an adequate range of TiH2 addition. The increase of TiH2 content more than 3 mass% was not an effective way to produce highly porous aluminum foam. Addition of fine Al2O3 particle resulted in a significant increase in foam expansion.

Numerical study of confined slot jet impinging on porous metallic foam heat sink

This study numerically investigates the impinging cooling of porous metallic foam heat sink. The analyzed parameters ranges comprise ε = 0.93/10 PPI Aluminum foam, L/ W = 20, Pr = 0.7, H/ W = 2–8, and Re = 100–40,000. The simulation results exhibit that when the Re is low (such as Re = 100), the Nu max occurs at the stagnation point (i.e. X = 0). However, when the Reynolds number increases, the Nu max would move downwards, i.e. the narrowest part between the recirculation zone and the heating surface. Besides, the extent to which the inlet thermal boundary condition influences the prediction accuracy of the Nusselt number increases with a decreasing H/ W and forced convective effect. The application ranges of H/ W and Re that the effect of the inlet thermal boundary condition can be neglected are proposed. Lastly, comparing our results with those in other studies reveals that the heat transfer performance of the Aluminum foam heat sink is 2–3 times as large as that without it. The thermal resistance is also 30% less than that of the plate fin heat sink for the same volumetric flow rate and the 5.3 mm jet nozzle width. Therefore, the porous Aluminum foam heat sink enhances the heat transfer performance of impinging cooling.

A Novel Semi-empirical Model for Evaluating Thermal Performance of Porous Metallic Foam Heat Sinks

A novel semi-empirical model with an improved single blow method for exploring the heat transfer performance of porous aluminum-foam heat sinks in a channel has been successfully developed. The influencing parameters such as the steady-state air preheating temperature ratio, Reynolds number and medium porosity on local and average heat transfer behavior of porous aluminum-foam heat sinks in a channel are explored. The heat transfer enhancement of using a porous heat sink in a channel to a hollow channel is, (Nu¯b)ss∕(Nu¯b)ε=1, much greater than unity and generally decrease with increasing Re. Furthermore, two new correlations of (Nu¯b)ss and (Nu¯i)ss in terms of ϴ,Re,Da,γ and ε are proposed. As compared with the results evaluated by the transient liquid crystal method, the channel wall temperatures predicted by the present semi-empirical model have a more satisfactory agreement with the experimental data, especially for the cases with smaller porosities. The limitations with relevant error maps of using the transient liquid crystal method in porous aluminum foam channels are finally postulated.

Heat transfer in rotating channel with open cell porous aluminium foam

The convective heat transfer of pressurized airflow in a radially rotating serpentine channel inside porous aluminum material is examined experimentally. The most important governing parameters are the Prandtl number, the Reynolds number for forced convection, the rotation number for the Coriolis force-induced cross stream secondary flow and the Grashof number for natural convection. This work maintains the parameters of the test rig at approximately the values of those in a real engine, to simulate the operating conditions of a real gas turbine. The local heat transfer rates for radially rotating serpentine channels with porous aluminum foams were measured and compared with those of staggered half-V ribbed and smooth walls in previous literature. This paper investigates the heat transfer capability of porous aluminum foams in rotating channels

Shock Propagation in Nonreactive Porous Solids

Shock propagation and attenuation have been studied in porous graphite and aluminum foams (40% to 80% of crystal density). The effects of such material parameters as particle (or pore) shape, size, and size distribution on response of the materials to shock loading were investigated, and Hugoniot measurements below 25 kbar were made. It was found that in the pressure and porosity range studied, the ``compacted'' volumes for pressures above a few kilobars are essentially those of the solid materials at the same pressure. The densities of specimens of aluminum foam recovered after shocking to about 10 kbar correspond approximately to that of solid aluminum, while the densities of recovered specimens of ATJ graphite are very close to their initial densities, even after shocking to 50 kbar. An artificial viscosity computer code has been successfully adapted to calculation of shock attenuation in porous solids. Within the idealizations of the models employed, calculated transit times and shock profiles are in reasonably good agreement with the experimentally measured quantities.