Aluminium Foam – Structure, Properties and Benefits

Foam structures are both durable and lightweight, with a large surface area to volume ratio. The unique mechanical properties of aluminum foam include a high strength to weight ratio and a completely isotropic load response.

The foam also inherits a large number of the properties of its parent metal that include corrosion resistance, strength, electrical and thermal conductivity, but at a fraction of the weight. These foams find applications in structures such as heat exchangers and as substrates for catalytic converters.

Two Basic Foam Structures

Goodfellow offers two basic foam structures in a range of sizes and densities. The first form is stochastic or evenly sized, but with irregular shaped pores, also known as reticulated. The second form has regular, stacked cells.

Stochastic or Reticulated Foam

This foam is a skeletal structure, meaning it is not a metal coating on a base structure, but is instead a pure metal/alloy. The cells and ligaments form a regular, repeatable, regular and uniform matrix throughout the entirety of the material.

It is rigid with a highly porous and permeable structure. It exists in a range of densities and pore sizes.

Regular Stacked Cell Foam

This regular, stacked cell foam has evenly- spaced, open pores, defined as tetrakaidecahedrons, which are polygons with 14 faces - 8 hexagonal and 6 square. It can be imagined as a 3D honeycomb.

Sand casting is used to manufacture the foam and as such the exact form of the foam can be determined before its manufacture, and is repeatable in series: each manufactured piece will be identical and will therefore have exactly the same behavior.

Properties of Aluminum Foam

The properties of aluminium foam are shown in Table 1.

Table 1. Properties of Alumium foam

CHARACTERISTICS Stochastic or reticulated foam Regular, stacked cell foam
Material Aluminium 98.5% (Aluminium 6101 alloy) Pure aluminium 99.5% (aluminium alloys on request)
Standard catalogue sizes 3.2mm to 30mm thick x 150mm x 150mm (other sizes on request) 40mm x 100mm x 172mm (other sizes on request)
Standard cladding None Aluminium, one side
Cladding thickness Not applicable 4mm
Standard cell size 2 to 16 pores/cm 10mm
Other available cell sizes Not applicable 14mm or on request
Foam topology Open, interconnected Open, stacked Kelvin cells
Relative density 4 to 10% 15%
Nominal Density (unclad foam) 0.11 to 0.27 g/cm3 0.41 g/cm3
Relative surface area 200 to 2000 m2/m3 360 m2/m3
Maximum service temperature 450°C 450°C
Melting point 660°C 660°C
Compression Strength 2.53 MPa* 4 MPa**
Tensile Strength* 1.24 MPa* -
Shear Strength 1.31 MPa* -
Modulus of Elasticity (Compression)* 103.08 MPa* 100 MPa (estimated)
Modulus of Elasticity (Tension)* 101.84 MPa* 100 MPa (estimated)
Shear Modulus 199.95 MPa* 48 MPa
Specific Heat 0.895 J/g-C* 0.9 J/g-C**
Bulk Thermal Conductivity 5.8 W/m-C* 15 W/m-C**
Coefficient of Thermal Expansion (0-100°C) 23.58 x 10-6 m/m—C* -
Bulk Resistivity 7.2 x 10-5 ohm - cm* -

*8% nominal density
** AlSi7Mg (available to special order)
** 15% nominal density

Properties shown are typical values, they are not absolute material properties, and should be used for guidance only. It is recommended that materials and components are tested for their suitability for a specific application.

Applications

Typical applications of all foam types include:

  • Sound absorption
  • Fragmentation capture
  • Impact absorption
  • Heat sinks and exchangers
  • Matrix for chemical beds and scrubbers
  • Filters and mist elimination of water and oils
  • Core structure for high strength panels
  • Battery plates and spacers
  • Weight reducing components in aircraft or automotive applications
  • Catalyst surface

About Goodfellow

Goodfellow supplies metals, ceramics and other materials to meet the research, development and specialist production requirements of science and industry worldwide.

The Goodfellow group consists of four companies. The main administration, research laboratories and workshops are located at the Company's headquarters in Cambridge, England. The subsidiary offices in America, France and Germany provide an additional service.

This information has been sourced, reviewed and adapted from materials provided by Goodfellow.

For more information on this source, please visit Goodfellow.

Comments

  1. Ehsan Soli Ehsan Soli Iran says:

    What curve yield stress vs volumetric strain in the foam aluminum?

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of AZoM.com.

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