The properties of closed-cell Aluminum foam
Aluminum foams have two basic shapes: closed-cell Aluminum foam and open cell Aluminum foam.
Closed-cell metal foams have been developed since about 1956 by John C. Elliott at Bjorksten Research Laboratories. Metal foams are commonly made by injecting a gas or mixing a foaming agent (frequently TiH2) into molten metal. In order to stabilize the molten metal bubbles, high temperature foaming agent (nano- or micrometer sized solid particles) is required. The size of the pores, or cells, is usually 1 to 8 mm.
The main characteristics of closed-cell Aluminum foams are:
• Efficient energy absorption
• Excellent stiffness-to-weight ratio
• Nearly isotropic - Multiaxial loading
• Low thermal conductivity
• Fire resistant
• Shock wave attenuation
• Sound and vibration damping and absorption
• Tailorable density and properties
• Recyclable
Closed-cell Aluminum foams structure makes them excellent materials to absorb sound, impacts and vibrations. Their metallic nature allows their use as electromagnetic shields and makes them stable at high temperatures. Aluminum foams are recyclable and non contaminant, while offering a combination of physical, mechanical, thermal and acoustic characteristics typical of a homogeneous material. All these characteristics are ideal for diverse and important applications in different industrial sectors, from aerospace or navy to motor and construction.
Aluminum foam is metallic and relatively isotropic, with many randomly distributed pores inside its structure. These pores, mainly spherical, (open or closed) occupy 50% to 90% of the total volume. The mechanical and physical properties depend greatly on density that varies from 0.4 to 0.8 g/cm3 (floats in water).
There are a lot of applications areas of Aluminum foams. Due to perfect sound absorption it could be used as sound barriers inside tunnels, as the unique acoustic materials, etc. Aluminum foams are found in construction industry as fire proof materials and structure protection systems against explosions, in the automotive industry, in the aerospace industry as structural components in turbines and spatial cones, in the naval industry as low frequency vibration absorb.
Moreover, closed-cell Aluminum foam is well-processed by drilling, milling and turning. It can be connected by pasting, soldering or special welding. Various decorative materials are freely pasted on its surface, it can be painted. That is why it can be used as decorative materials for indoor and outdoor.
