Engineers and technical buyers need energy absorption solutions that can help protect vehicles, buildings, equipment, and personnel from blast waves. As the threat of terrorism continues, military vehicles and facilities aren’t the only targets for attacks that use improvised explosive devices (IEDs). Today, concrete structures such as office buildings, parking garages, and sports stadiums represent “soft targets” for terrorists. In the event of an attack, energy-absorbing structural foams can decrease blast impulse transfers and help save lives. These specialized materials can also reduce shock and vibration.
Aluminum foams from Elasto Proxy are strong, lightweight materials that provide blast mitigation and thermal acoustic insulation. In addition to absorbing energy from explosions, these aluminum composite products offer thermal conductivity and sound attenuation. Applications for structural aluminum foams include vehicle IED underbody kits, architectural blast panels, composite flooring systems, and vibration management. Additional uses include vehicle lightweighting and sandwich panels, multi-layer building and construction materials with excellent mechanical performance.
Physical Properties and Custom Fabrication
Aluminum foams are produced through a continuous casting process where gas is direct-injected into a melt. Like pure aluminum, these closed-cell composites are buoyant, flame resistant, and corrosion resistant. Structural aluminum foams may oxidize over time, but this oxidation does not affect their physical properties. The porosity of aluminum foams can be “tuned” to meet specific application requirements, and blast mitigation data shows that these materials can reduce G-loading by 10-to-1. Additional properties include a high stiffness-to-weight ratio and strain-rate insensitivity.
Density and thickness play an important role in determining the energy absorption characteristics of aluminum foams. The materials that Elasto Proxy custom-fabricates have a relative density of 4% to 22% and an absolute density of 0.11 g/cc to 0.6 g/cc. Standard thicknesses range from 1/2 in. (12.7 mm) to 3.5 in. (89 mm), but custom sizes are also available. Using water jet cutting, Elasto Proxy can convert aluminum foam panels that are up to 4 ft. wide (1220 mm) and up to 12 ft. long (3658). With our lamination capabilities, Elasto Proxy can also create sandwich-like structures that incorporate other insulating materials.
Aluminum Foams and Blast Testing
Aluminum foams have been independently tested to demonstrate their utility to military vehicles and reinforced concrete (RC) structures. In accordance with ITOP 4-2-508 (Section 3.3), an International Test Operating Procedure (ITOP) for military vehicles, a large adjustable fixture with a weight of 11,000 lbs. was deployed. An explosive charge of 8 lbs. of TNT was then buried at a depth of 100 mm in an environment whose soil composition simulated that of the desert. The fixture, which was designed to simulate a ground vehicle, withstood different strain rate loadings. In layman’s terms, strain rate is the rate of material deformation over time and with velocity.
Aluminum foams were also used in independent testing that involved the protection of RC structures against explosion-generated blast wave loads. As a team of scientists reported in an article for the Journal of Structural Engineering (August 2005), “the experiments provided very clear results of the strains and accelerations.” An additional test concluded that the performance of aluminum foams is very similar at different impact speeds, proving that this closed-cell material has no distinct strain rate sensitivity.
Choose Custom-Fabricated Aluminum Foams
Do you have questions about structural aluminum foams from Elasto Proxy? Would you like to learn how our water jet cutting equipment provides a fast, accurate, and cost-effective way to convert panels of aluminum foams into the blast-resistant insulation that you need? Would you like to read the blast-test reports for yourself, or review some general product information? For custom-fabricated aluminum foams that you can count on, ask Elasto Proxy.