Composite Metal Foams and Their Applications
Metal foam is a porous material consisting of open-cell, closed-cell, or composite cavities. Open-cell metal foam has an interconnected network of pores. Closed-cell metal foam is similar to open-cell, but is sealed and may not have interconnectivity of internal pores. Composite metal foam combines a matrix of hollow metal beads of one material, such as steel or nickel, within another material, such as aluminum.
Recently, researchers from North Carolina State University have reached out to the researching community in an attempt to open research into different applications of composite metal foams using the current manufacturing methods and available data as a starting point.
One of the difficulties with composite metal foam is ensuring the matrix of beads is consistent. This is one of the patented processes researchers from NC State has developed.
More recently, interest in 3d printing applications for manufacturing metal foams has surfaced. This includes everything from development of custom sand castings for open-cell metal foams to development of composite metal foams with a perfect bead matrix.
Possible Applications
Light Weight Structures
Metal foam panels can be used as a supplemental material replacing some solid material while reducing weight and retaining material properties.
A metal foam panel is lighter weight than a solid panel of the same material and can offer the same bending stiffness properties.
Metal foams have energy absorbing properties similar to tubing, but can absorb from any direction. The level of absorption can be modified based on the pore sizes and quantities.
Structures will have the benefit of being able to damp beam vibration and dissipate energy.
Strain Isolation
When loaded axially, metal foam and thin-walled tubing absorb energy similarly. The foam compresses the internal pores until the solid metal surfaces are in contact. The tube buckles and deforms to mechanically move metal out of the way to allow for compression.
Because metal foam will have the same properties when loaded in any direction, it can be used to isolate energy absorbing in a system.
Tubing can be filled with metal foam to increase the energy absorbing properties.
Mechanical Damping
Composite metal foams can have a 10x increase in mechanical damping capacity when compared with solid metals.
Acoustic Absorption
Sound absorption is an attractive property if it can be obtained without having to incorporate additional materials such as fiberglass for that specific reason.
Metal foams can offer a good absorption coefficient that will work in the design favor if the other properties of metal foams are also desired.
Sound can be absorbed through mechanical damping, thermos-elastic damping, moving through different material mediums, etc.
Heat Transfer
The thermal conductivity of solid metal is higher than the thermal conductivity of its metal foam. Therefore, metal foams will be more effective as fire protection and heat protection than solid metal.
Filters (open-cell metal foam)
The ability to control the pore size and quantity of pores allows for the potential to develop high temperature gas and fluid filtration systems.
Buoyancy
The low density properties and good corrosion resistance of some metal foams offers the possibility for floatation or subsea systems.
Resources:
Metal Foams: A Design Guide (PDF)
“Overview of Composite Metal Foams and their Properties and Performance”
Metal Foams: Fundamentals and Applications - By Nihad Dukhan
Jarrett Linowes
Mechanical Engineer
omniamfg@gmail.com
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