Aluminum foam sandwich

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Aluminum foam sandwiches are sandwich panels made of an aluminum alloy , consisting of a metallic, bubble-free outer layer and a core made of metal foam . The sandwich panels have a high strength in relation to their mass and a great energy absorption potential.

For example, aluminum foam sandwich panels are suitable for the construction of engine hoods for high-speed trains .

Production and materials

In order to create a bond between the outer layer and the aluminum foam core, one can use the ex-situ bond or the in-situ bond.

Ex-situ bonded aluminum foam sandwich panels

Ex-situ bonding creates the connection between the outer layer and the aluminum foam core by gluing, soldering or diffusion welding. These foams are either closed or open-pored.

If you use closed-pore foam, it is made from aluminum alloys either with liquid metal compounds (Alporas, Cymat) or using the sintering technique.

Open-cell foam is also made from aluminum and other metals. The material for the outer layers is selected from various aluminum alloys, steel and other metals.

In-situ bonded aluminum foam sandwich panels

For in-situ bonded outer layers, the core is always closed-cell foam. The goal of in-situ bonding is to create a metallic bond between the outer layer and the foam core. This is achieved in three ways:

  • A foamable starting material is foamed between the outer layers. When the liquid foam comes into contact with the solid outer layer, a fine metal layer forms. This is difficult to achieve because the oxidation of the outer layers and the foam prevents a joint zone from forming. There is also a risk that the outer layers will begin to melt during this process. Therefore, the process is only successful if no aluminum but steel is used for the outer layers and only the foam consists of aluminum. However, recent investigations by the Fraunhofer IWU have shown that it is even possible to create a connection between an aluminum cover layer and the aluminum core with today's means without rolling.
  • Another strategy is to quickly solidify the surface of a foamable, molten metal before it can foam. Inside, however, a foamed structure is created. This method achieves an integral type foam structure. The integrated foam sandwich consists of aluminum alloys ( AlCu 4, AlSi 9Cu3) and magnesium alloys (AZ91, AM60). The material for the core and the outer layer is the same.
  • The third way to achieve an in-situ bond is to compact metal powder between the outer layers. These sandwich connections are rolled several times in order to achieve the desired thickness of the panels. The three-layer composite structure is then heated so that the core can foam. The melting point of the material for the outer layer is above the melting temperature of the foamable material. The compositions of the foamable material are usually Al-Si , Al-Si-Cu or Al-Si-Mg alloys, while the outer layers are 3xxx , 5xxx , 6xxx aluminum alloys.

Pre- and post-processing of aluminum foam sandwich panels

It is possible to produce complex 3D shapes from in-situ bonded aluminum foam panels. In the case of the second method, integral foam molding, the desired geometry is achieved by shaping the mold in which foaming is then carried out.

In the case of the third method, the three-layer composite structure is reshaped before foaming, but the sandwich panels can also be reshaped by forging after foaming. If the aluminum foam sheets are made of heat treatable alloys, the strength and strength are improved upon hardening. To join two sandwich panels or a sandwich panel with a metallic part, several joining techniques are used, for example: laser welding, TIG welding, MIG welding, riveting, etc.

literature

  • Thomas Hipke, Günther Lange, René Poss: Paperback for aluminum foams. Aluminum-Verlag, Düsseldorf 2007, ISBN 978-3-87017-285-5 .

Web links

Individual evidence

  1. ^ Robert Ballecer: Aluminum Foam . TWiT.tv . Accessed December 31, 2014.
  2. ↑ a b c J Banhart, HW Seeliger, Aluminum foam sandwich panels: manufacture, metallurgy and applications, Advanced Engineering Materials, 2008, 10: 793-802.
  3. ↑ AM Harte, NA Fleck, MF Ashby, The fatigue strength of sandwich beams with an aluminum alloy foam core, International Journal of Fatigue, 2001, 23: 499-507.
  4. ↑ I Elnasri, H Zhao, Y Girard, perforation of aluminum foam core sandwich panels under impact loading, Journal of Physique, 2006, 134: 921-927.
  5. ^ R Neugebauer, C Lies, J Hohlfeld, T Hipke, Adhesion in sandwiches with aluminum foam core, Production Engineering Research and Development, 2007, 1: 271-278.
  6. ↑ Trade journal for metallurgy "Metall", GDMB Verlag GmbH , edition 01-02 2017, ISSN 0026-0746, page 25, article "Production of sandwiches with aluminum cover sheets and aluminum foam core without roller compaction"
  7. ↑ a b C Körner, M Hirschmann, V Bräutigam, RF Singer, Endogenous particle stabilization during magnesium integral foam production, Advanced Engineering Materials, 2004, 6: 385-390.
  8. ^ HD Kunze, J Baumeister, J Banhart, M Weber, P / M technology for the production of metal foams, Powder Metallurgy International, 1993, 25: 182-185.
  9. ^ H Wiehler, C Körner, RF Singer, High pressure integral foam molding of aluminum - process technology, Advanced Engineering Materials, 2008, 10: 171-178. doi : 10.1002 / adem.200700267
  10. ↑ HW Seeliger, Aluminum foam sandwich (AFS) ready for market introduction, Advanced Engineering Materials, 2004, 6: 448-451.
  11. ↑ Carolin Koerner, Book - Integral foam molding of light metals: technology, foam physics and foam simulation, Springer-Verlag Berlin Heidelberg, 2008, p.19.
  12. ↑ HW Seeliger, Manufacture of aluminum foam sandwich (AFS) components, Advanced Engineering Materials, 2002, 4: 753-758.
  13. ↑ Book - Handbook of cellular metals: production, processing, applications, Editors: HP Degischer, B Kriszt, Wiley-VCH Verlag, 2002, p.119.