Lightweight synthetic foam metal improves fuel economy

Researchers at New York University (NYU) Polytechnic School of Engineering, in collaboration with Deep Springs Technology (DST) and the U.S. Army Research Laboratory, have demonstrated a new metal matrix composite that is so light that it can float on water. A boat made of such lightweight composites will not sink despite damage to its structure. The new material also promises to improve automotive fuel economy because it combines light weight with heat resistance.

Although syntactic foams have been around for many years, this is the first development of a lightweight metal matrix syntactic foam.

Their magnesium alloy matrix composite is reinforced with silicon carbide hollow particles and has a density of only 0.92g/cm3 compared to 1.0g/cm3 of water. Not only does it have a density lower than that of water, it is strong enough to withstand rigorous conditions.

Significant efforts in recent years have focused on developing lightweight polymer matrix composites to replace heavier metal-based components in automobiles and marine vessels. The technology for the new composites is very close to maturation and could be put into prototypes for testing within three years. Amphibious vehicles such as the Ultra Heavy-Lift Amphibious Connector (UHAC) being developed by the U.S. Marine Corps can especially benefit from the light weight and high buoyancy offered by the new syntactic foams, the researchers explained.

“This new development of very light metal matrix composites can swing the pendulum back in favor of metallic materials,” says Nikhil Gupta, NYU engineering professor in the Department of Mechanical and Aerospace Engineering and the study’s co-author. “The ability of metals to withstand higher temperatures can be a huge advantage for these composites in engine and exhaust components, quite apart from structural parts.”

The syntactic foam made by DST and NYU starts with a matrix made of a magnesium alloy, which is then turned into foam by adding strong, lightweight silicon carbide hollow spheres developed and manufactured by DST. A single sphere’s shell can withstand pressure of over 25,000psi before it ruptures – 100x the maximum pressure in a fire hose.

The hollow particles also offer impact protection to the syntactic foam because each shell acts like an energy absorber during its fracture. The composite can be customized for density and other properties by adding more or fewer shells into the metal matrix to fit the requirements of the application. This concept can also be used with other magnesium alloys that are non-flammable.

The composite has potential applications in boat flooring, automobile parts, buoyancy modules, and vehicle armor.

New York University Polytechnic School of Engineering

http://engineering.nyu.edu