What is Aluminium foam?
Aluminium foam is a material made of Aluminium, which is also populated with a large volume of pores or cavities. It is a solid material filled with pores such that up to 95% of the volume consists of gas-filled voids,in two different kinds of structures. Depending on the density, appearance of the structure, shapes of cavities and method of manufacture, these are known as Stochastic or Reticulated Foams and Regular Stacked Cell Foams. The pores can be sealed from each other (known as closed-cell foams) or can form an interconnected network (open-cell foams). The injection of gas, whether by physical or chemical means, is broadly responsible for creating the pores or cavities within Aluminium foam.
Like other metal foams, Aluminium foam is both extremely durable and lightweight, with a large surface area to volume ratio. The non-flammable material inherits all of the excellent properties of its parent metal Aluminium, such as recyclability, heat and corrosion resistance, strength, electrical and thermal conductivity, etc, but at a fraction of the weight. Aluminium foam has a high specific stiffness, especially compared to the original denser metal, and can withstand great damage with little deformation. From a designer or manufacturer’s perspective, Aluminium Foam can be made into complex geometrical forms easily and offers the properties of the original, metal in addition to new, favorable qualities of its own.
How strong is Aluminium foam?
Aluminium Foam is extremely strong and can absorb a great deal of mechanical energy when deformed, making it an attractive material for impact energy absorbers. Unlike polymeric foams which tend to spring back, Aluminium foams do not do this, preventing any secondary damage. There is a direct relationship between the density and strength of the material, that is, a 20% dense foam material is more than twice as strong as a 10% dense material.
An especially strong format of Aluminium foam is Aluminium foam sandwich (AFS) panels, where two metallic dense face sheets enclose within them a core made of metal foam, of Aluminium or Aluminium alloy. These sandwich panels serve as an engineering structural material due to their stiffness-to-mass ratio and energy absorption capacity, making them suitable for diverse applications in the aerospace, automotive and architecture and construction industries.
How is Aluminium foam made?
Open-cell and closed-cell foams can be created in one of two ways. The first method injects gas into metallic melts and as gas bubbles through the molten metal, a foam is created, which is then removed and allowed to cool. In some cases, the air-injection process may incorporate a fine dispersion of ceramic particulate in the molten Aluminium. These ceramic particles stabilise the air bubbles, and create panels with an interesting level of detail, texture and variability.
The second method incorporates chemical blowing agents or foaming agents, which decompose or react in the melt, producing gas bubbles, which result in the foam’s cavities. These processes are relevant to a Stochastic or Reticulated foam, which is essentially a skeletal structure, meaning that it is not a metal coating on a base structure, rather it is pure metal. Here, the pores and ligaments form a regular, repeatable matrix throughout the material.
What is Aluminium foam used for?
Closed-cell Aluminium foam is widely used as a lightweight construction material, both in its original format, and as sandwich panels, which are valued for their low density and very high stiffness. The main applications for this variety of foams are in the automotive industry as impact, acoustic and vibration absorbers, the aerospace industry as components for turbines or spatial cones, in the construction industry as a fire-proof, structural and protective barrier against explosions or heavy sound, as well as in the naval industry. A number of automotive and aircraft manufacturers have consistently used Aluminium foam and its high-strength sandwich panels for years now, to achieve valuable weight reduction in airplane and car body parts.
Open cell foams, on the other hand, are often employed for their filtration and catalytic properties, as well as their response to high temperature. They are used in structures such as heat sinks and exchangers, chemical beds and scrubbers, filters and mist eliminators, and battery plates. Like closed cell foams, they continue to find use in applications where vibration and sound absorption is needed.
Beyond these more functional roles, the architectural and design applications of Aluminium foam are extensive. In addition to its unique sponge-like appearance, it is sought after here for its sound absorbing properties, making it ideal for applications which require both acoustic absorption and beauty. Aluminium foam panels are seen in facades, wall cladding, ceiling tiles or dropped ceilings, retail displays, lighting fixtures, exhibits and more. The porosity, lightweight nature and unique aesthetic of the material also makes it a favorite for artists and designers creating lighting, furniture and decorative interior products.
Another reason why the material is so popular in the architecture and design industries is that it is 100% recyclable and is frequently composed from 100% recycled content as well. From a practical perspective, Aluminium foam panels are heat insulating and resistant, mold and mildew free, do not collect dust and do not create a hospitable environment for bugs to nest in. They are also highly resistant to wind loads when placed in exterior applications, are easy to install and move and have excellent fire ratings.
Is Aluminium foam expensive?
Metal foams, as a whole are not as inexpensive as sheet metals, or other polymeric counterparts. This is because of the number of processing steps and specific raw materials needed to facilitate their manufacture. They are expensive due to complicated and energy-intensive manufacturing procedures.
However, the cost and energy benefits offered by using lightweight yet resilient foams such as Aluminium foam in various applications–from the automotive industry to architectural facades–can greatly offset these initial material costs.