Papers by Keyword: Metal Foam

Abstract: Here, we report the mechanical behaviour of open-cell foams of 6061-T6 Al-alloys under quasi-static loading. The foams were processed by pressurized salt infiltration technique with efficient control over pore size and distribution. Spherical salt beads of NaCl of required size distribution were used as preforms. The molten alloy was infiltrated into the preforms under an inert gas pressure of 2 bar followed by cooling and leaching of the salt pattern in a suitable aqueous medium. The pressurized infiltration process is convenient to overcome the capillary forces arising from the non-wetting conditions between salt beads and molten alloys and offers a versatile and economical route for the production of open-cell foams. The shape, size and distribution of the pores were studied with optical microscope and X-ray computed tomography (X-ray CT). The developed foam samples were cut into required dimensions following ASTM E9-09 standard and their mechanical properties were analyzed under quasi-static compressive loading.

Abstract: Metal foams have a cellular structure consisting of a solid metal containing a large volume fraction of pores. In particular, open, penetrable pores are necessary for industrial applications such as in high temperature filters and as support for catalysts. In this study, Fe foam with greater than 90% porosity, 2-mm pore size was successfully fabricated using a slurry coating process and the pore properties were characterized. The Fe and Fe₂O₃ powder mixing ratios were controlled to produce Fe foam samples with different pore sizes and porosity. First, the slurry was prepared through the uniform mixing of powders, distilled water, and polyvinyl alcohol (PVA). The amount of slurry coated on the PU foam increased with theFe₂O₃ mixing powder ratio, but the shrinkage and porosity of the Fe foams decreased, respectively, with increasing Fe₂O₃ mixing powder ratio.

Abstract: Purpose of this study is investigation of energy absorption capability of the sandwich structures composed of combination of polystyrene and metal foam element and their suitability as new structure for design of protective helmets. Two types of the metal foams were experimentally tested and evaluated: Alporas (Shinko Wire Ltd., Japan) and Aluhab (Aluinvent Plc., Hungary). Samples of the sandwich structure are composed of two layers: bottom expanded polystyrene (EPS 200S) layer and upper metal foam layer which are glued together. Prepared samples are tested using a drop tower experiment to measure sample response (acceleration, reaction force) at different strain rates and energies. From acceleration/time history the Head Injury Criterion (HIC) is calculated as significant parameters in terms of protective helmets. Moreover, measured and derived characteristics are compared with pure EPS samples to obtain comparison of deformation behaviour between conventional structure for protective helmets and designed sandwich structures.

Abstract: Closed-cell superplastic Zn-22Al alloy foams were manufactured through the melt foaming process using sodium hydrogen carbonate powder as a foaming agent. Foaming tests were carried out under different foaming temperatures, times and additive amounts of foaming agent. The porosity of Zn-22Al alloy foams were between 30 and 70%. The cell wall consisted of fine equiaxial crystal grains after solution treatment. The compressive properties of the Zn-22Al alloy foams were investigated at room temperature and high temperature. Zn-22Al alloy foams exhibited high strain rate sensitivity, which was caused by superplastic deformation of the cell wall material.

Abstract: Fe foam with above 90% porosity and 2 millimeter pore size was successfully fabricated by a slurry coating process. In this study, the binder contents were controlled to produce the Fe foam with different pore size, strut thickness and porosity. Firstly, the slurry was prepared by uniform mixing with Fe powders, distilled water and polyvinyl alcohol (PVA) as initial materials. After slurry coating on the polyurethane (PU) foam the sample was dried at 80°C. The PVA and PU foams were then removed by heating at 700°C for 3 hours. The debinded samples were subsequently sintered at 1250°C with holding time of 3 hours under hydrogen atmosphere. The three dimensional geometries of the obtained Fe foams with open cell structure were investigated using X-ray micro CT(computed tomography) as well as the pore morphology, size and phase.

Abstract: This work is carried out to study the copper metal foam as porous wick structure in a flat heat pipe. The method of fabricating copper foam has been described. The characterization of copper foam has been carried out by scanning electron microscope (SEM) and X-Ray Diffractogram (XRD) analysis. Effect of liquid velocity on pressure drop and maximum capillary heat transport of fabricated copper foam has been presented.

Abstract: In the paper the methods of designing and manufacturing of the metals foam with regular cells are researched. The software models of metals foam are designed by CAD. The models are transmitted into 3D printing machine to manufacture foam framework. The metal foams with regular cells and fixed porosities are manufactured by chemical plating, electric plating and investment cast. According to the applications the structures of metal foams can be designed to control sizes, shapes and distribution of pores, porosities, density and to control the properties of metals foam, which can satisfy various demands of applications. Nickel foam with regular cells is designed and manufactured by this method.

Abstract: Metallic foams are known for their interesting physical and mechanical properties such as high stiffness, very low specific weight, high compression strength, unusual acoustic and thermal properties and good energy absorption characteristics. These materials are currently manufactured by means of several different processes. The limit of these conventional technologies is the impossibility to produce foams with complex geometry.This paper deals with the study of an innovative method to produce complex shaped precursors for aluminum foams through cold gas dynamic spray deposition process (CGDS). Aluminum alloy (Al-Si) fine powders were previously mixed with the blowing agent (titanium-hydride, TiH2). The mixing process was carried out by means of sound-assisted fluidized bed apparatus that allows to obtain an homogeneous mixture of the two elements. The mixed particles were then sprayed by means of the CGDS process on a stainless steel sheet that simulates the real component to be reinforced with the foam. Subsequently the obtained precursor was heated up in a furnace The produced metal foam was characterized using optical and electron microscopy in order to study the cell morphology and distribution.The obtained results showed the effectiveness of this method to produce aluminum foams with complex shape.

Abstract: The fracture properties of a series of metal foam sandwich structures based on glass fiber-reinforced polyamide 6,6 composite (GF/PA6,6) skins have been investigated. The open cell core materials were manufactured using the Lost Carbonate Sintering (LCS) process, a recently-developed technique for manufacturing metal foams. Initially, the effect of varying the compaction pressure used in producing the metal foams as well as the density of the samples were investigated through a series of compression tests. Here, it was shown that the compressive strength and the elastic modulus of the foams varied with density and compaction pressure, in spite of the fact that the average size of the cells in these foams were insensitive to either of these two parameters. The resistance of sandwich structures to localized loading was investigated through a series of indentation tests. Here, it was shown that the indentation response of sandwich structures could be characterized using a simple indentation law, the parameters of which did not exhibit any clear dependency on the density of the foam. Finally, three point bend tests on the sandwich structures have shown that their loading-bearing properties were sensitive to foam density.

Abstract: The effects of geometrical shapes are believed to play significant role in the deformation of metal foams under impact loading. This research was carried out to investigate the deformation behaviour of a single cellular cell of metal foam with different geometrical shapes. The simulation analyses were done on various two dimensional shapes with the consideration of the material properties. Two parameter values had been studied to determine the dynamic deformation behaviour of various geometrical shapes i.e. the internal energy and kinetic energy. It is found that, the geometrical shapes have shown significant effects on the dynamic deformation of single metal foam cell. It is hoped that this study could contribute significant result to the research of the metal foams especially in analyzing the shape effects to the behaviour of the metal foam under impact loading.