The materials could be used in a wide range of engineering structures from wind turbines to aircraft component, from bridges to offshore oil-drilling components. The composite material developed by researchers in Buffalo, at the State University of New York has exceptionally high damping ability and avoids many of the problems of conventional damping materials based on polymers and metals.
“The damping ability of the new material is superior to any polymer (including rubber) and any metal (including shape-memory alloys),” says team leader Deborah Chung, who adds that the material has grown out of 15 years of research in her laboratory [Muthusamy et al., Carbon (2010) 48 (5), 1457] The material is a cement-matrix graphite-network composite containing 8 % by volume of graphite. The graphite ligaments in the network exhibit an accordion-like microstructure and so can absorb vibrational energy by a flexing. The cement component meanwhile adds overall stiffness to the composite.
“This structure is believed to be responsible for the high value of the loss tangent, i.e. the high value of the damping ratio,” explains Chung. In fact the damping ratio is higher than that of rubber. Together the high loss tangent and high stiffness lead to an exceptionally high energy dissipation under vibrational stress, adds Chung. She and her colleagues describe test details in the journal Carbon in which they demonstrate the composite’s prowess over conventional damping materials.
The researchers point out that this material has several advantages over conventional cement-based materials, in that it also has very high compressive ductility, very high compressive strength, high ?exural strength, high ?exural toughness, and low electrical resistivity. It does suffer from a low compressive modulus and low ?exural modulus but could nevertheless be used to replace polymers and metals for damping and be used with conventional concrete where damping is required, as its density is comparable to unmodified concrete. Given the close relationship between vibration damping and sound attenuation, the composite will also be effective in terms of sound proofing too.
The team is currently going through the patent application process and but is ready to make the technology available for commercial licensing.