Metal matrix composite that floats shows promise in auto, marine applications

NYU's Polytechnic School of Engineering has developed a magnesium alloy matrix composite reinforced with silicon carbide hollow particles that can float on water.

The New York University (NYU) Polytechnic School of Engineering reported on May 12 that researchers at the school have demonstrated a new metal matrix composite that light enough to float on water. Researchers say 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.

The magnesium alloy matrix composite, developed in cooperation with Deep Springs Technology (DST, Toledo, OH, US), is reinforced with silicon carbide hollow particles and has a density of 0.92 g/cc, compared to 1.0 g/cc of water. The university says technology for the new composite is 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 might especially benefit from the light weight and high buoyancy offered by the new syntactic foams, the researchers say.

“This new development of very light metal matrix composites can swing the pendulum back in favor of metallic materials,” says Nikhil Gupta, an NYU School of 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 lightweight silicon carbide hollow spheres were developed and manufactured by DST. A single sphere’s shell can withstand pressure of more than 25,000 psi before it ruptures—100 times 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.

NYU says the new composite has potential applications in boat flooring, automobile parts, and buoyancy modules, as well as vehicle armor. The research is being conducted in collaboration with the U.S. Army Research Laboratory.