Showing papers on "Aluminium foam sandwich published in 2005"

Graded open-cell aluminium foam core sandwich beams

Abstract: We show that the replication process can be extended towards the production of functionally graded porous structures by fabricating and testing structures in which outer layers of dense metal encase a central part made of foam with graded porosity. Samples of this kind are produced by pressing individual layers of NaCl powder of granulometry 60–90m, and then stacking these layers between two skins of dense aluminium. The stacked preforms are then infiltrated with pure aluminium and solidified before dissolution of the salt in water. Specimens containing up to five layers of porous Al of different density between two dense outer skins of pure Al are produced; selected samples are tested in three-point bending. Data show good agreement with analysis based on sandwich beam theory and the Deshpande–Fleck yield criterion. Results of this work indicate that whereas lightweight graded metal/metal foam beams show little promise from the standpoint of stiffness-limited design, they may be of interest from the standpoint of load-limited design. © 2005 Elsevier B.V. All rights reserved.

Energy absorption and crushing behaviour of foam-filled aluminium tubes

Abstract: The crushing behaviour and energy absorption of foam filled aluminium tubular structures were investigated using the quasi-static compressive tests. The crushing behaviour of the tubular structures changed due to foam filling. The energy absorption of the foam filled tubular structures was improved significantly. Foam filling caused an interaction effect between the tube and the foam during progressive crushing, leading to an increase in the mean crushing load compared to that of the foam or tube itself. This interaction effect might be affected by several parameters such as the density of the foam, the properties of both the foam material and tube material, and the thickness and outer diameter of the tube. In particular, the interaction effect essentially depended on the ratio of the mean crushing force of the foam to that of the tube.

Rheology Characteristics of Al-Si Alloy and Mg Alloy for Metal Foam Manufacturing

Abstract: Metal foam was produced by the Melt Foaming Method. In this foaming process, the two most important factors were the surface tension and the viscosity of molten Al-Si alloy and AZ91 Mg alloy that were measured, respectively, by the ring method and the rotational method. The surface tension and the viscosities were investigated in the temperature range from melting point to 800°C, and the effects of the added thickening elements were investigated at the mixing temperature. The optimal conditions for the metal foam manufacturing require low surface tension and high viscosity. It is possible that the optimal conditions of the surface tension and the viscosity can be obtained through controlling the amount of added thickening elements and holding temperature. Introduction Many metallic foam produced by Foaming method have coarse and irregular cell structures. The primary concern is to fabricate foams with more uniform structure, cell size and emulsion. It is important to understand the mechanisms and factors controlling. For the control of the bubble in molten metal, such as birth (foaming agent, TiH2), life, death, shape and size in molten metal, the physical properties of liquid metal which have great influence on fabricating properties of metal foam must be given adequate attention [1]. Thus this paper will investigate the bubble behavior of the molten metal and its two most important parameters: surface tension and liquid viscosity. These two factors were considered with two liquid mechanisms operating in foam. The first is gravity-driven melt flow from the top to base of foam column. The second is capillarity-driven melt flow from cell face to plateau borders. This leads to cell face thinning and often to cell face rupture [2,3]. Therefore, we investigated relation between the driving force of a melt flow and two parameters to make metal foam with fine cell structure. This study investigated the rheology characteristics, namely, viscosity and surface tension behavior evolution of Al-Si alloy and AZ91 Mg alloy in the liquid state. The Al-Si alloy and AZ91 magnesium alloy had the following characteristics; good castability and mechanical properties and light weight. The relationship between viscosity, surface tension and temperature, additional elements and stirring time, temperature was studied. Experimental Procedure Surface tension was measured by the modified drop weight method, which applies the capillary phenomenon to measure the maximum force and wetting angle when the ring is pulled out from the melt surface [4,5]. Fig. 1(a) shows a schematic illustration of the experimental apparatus for the surface tension measurement. Viscosity was measured by the rotational method, which measures the viscosity by calculating the torque that is a resistance force of the melt for the rotating rotor [4,5,6]. Fig. 1(b) shows a schematic illustration of the experimental apparatus for the viscosity measurement. In this experiment, graphite rotor and crucible were used. The high purity argon and SF6+CO2 (1:100) gas sealing was used to prevent surface oxidation. The flowing rate was set to 30(l/min). The alloy studied was Al-Si alloy, Materials Science Forum Online: 2005-06-15 ISSN: 1662-9752, Vols. 486-487, pp 464-467 doi:10.4028/www.scientific.net/MSF.486-487.464 © 2005 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-11/03/20,12:04:23) the chemical composition of which was (wt%) 7.0% Si-1.0% Cu-0.4% Fe-0.3% Mg-0.3% Zn and AZ91 Mg alloy with adding Ca. The temperature range of measurement was set from melting point to 800°C. The temperature was measured by Pt-Rh thermocouples, which were put them into the bottom and the side of the crucible. The maximum force (Fmax) that is measured by the ring method can be recalculated to a surface tension (σst) by equation (1).       ⋅ ⋅ = r R V R f R F , cos 4 3 max θ π σ (1) Where 4πR is wetted length, Fmax is the total maximum force, f is the Harkins Jordan factor [7] and θ is the wetted angle. Viscosity (ηvisco) can be calculated from the measured torque (T) on the rotation rotor [4, 5].

Process to make lightweight aluminium and plastic e.g. carbon fibre sandwich panels for e.g. automotive applications

Abstract: In a process to manufacture lightweight aluminium sandwich panels the panels are joined by staples inserted through pre-drilled holes. The sandwich may be further strengthened by bonding and insertion of a plastic layer.

A comparison of low energy impact behaviour in aluminium foam and polymer foam sandwich structures

Abstract: Energy absorption of polymer and aluminum foam sandwich structures with glass-fibre composite skins was similar for 5-25J impacts. The polymer foam structure exhibited localized fibre fracture and core crushing as impact energy increased. The aluminum foam structure exhibited extensive plastic deformation, radiating from the impact point, at all impact energies.

Open-cell foam manufacturing method for composite thermoplastic elastomer materials with a sandwich structure

Abstract: An open-cell foam manufacturing method uses a thermoplastic elastomer material as a substrate and adds composites, foaming agents and crosslinking agents to produce a first external sheet and a second external sheet, and then forms a sandwich structure having the first external sheet, a reinforced layer and the second external sheet aligned and stacked in sequence to produce open-cell foam sheets with a sandwich structure. Threads are pressed on the surface of the foam sandwich structure by a roller to improve the slippery resistance of the foam material, which not only has high elasticity and slippery resisting property, but also creates a high tensile strength due to the fibers of the reinforced layer.

Structural assessment of metal foam using combined NDE and FEA

Abstract: Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a high fidelity finite element analysis is conducted on as fabricated metal foam microstructures, to compare the calculated mechanical properties with the idealized theory. The high fidelity geometric models for the FEA are generated using series of 2D CT scans of the foam structure to reconstruct the 3D metal foam geometry. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile, compressive, and shear mechanical properties are deduced from the FEA model and compared with the theoretical values. The combined NDE/FEA provided insight in the variability of the mechanical properties compared to idealized theory.

Magnesium Integral Foam — A New Metallic Sandwich Structure

Abstract: Structural foams or integral foams are monolithic components with a solid skin and a cellular core. We developed a new method to produce metallic integral foam with conventional casting machines. The advantages of the material are a low density, a high energy absorption capacity, a high weight specific bending stiffness and a remarkable damping capacity.

Research on Preparation Of Aluminium Foam Sandwich by Powder Meta-llurgical Method and Face Plate/Foam Core Interfacial Microstructure

Abstract: Iron/aluminium foam/iron and titanium/aluminium foam/titanium sandwiches were prepared by powder metallurgical foaming method. The expansion behavior of aluminium foam core and the metallurgical combination process between the face plate and the core during heating were investigated, and the combination mechanism was established. It was found that the combination interfaces are composed of two parts, the intermetallic compounds formed by diffusion during heating and the structures solidified during cooling, which result in a good metallic combination between the face plates and the cores.

Deformation of sandwich beams with spherical pore Al alloy foam core in three-point bending

Abstract: The uniform axis compression capability of spherical pore Al alloy foam was studied and the relationship between compression strength and relative density was acquired. A comparison was made among the spherical pore Al alloy foam, polygonal pore Al alloy foam and Al foam. It is concluded that the spherical pore Al alloy foam has more good mechanics property than others two spherical pore. The load-deflection curve of sandwich beams with spherical pore Al alloy foam core loaded in three-point bending and the four kinds of failure mode were investigated and the failure map of sandwich beams was founded. The calculated values with peak load formulae coincide well with the experimental ones. It is concluded that the sandwich beams with core of spherical pore Al alloy foam is excellent for more good mechanics property.