The sponge-like configuration has a density of just 5% and can be ten times stronger than steel.
Massachusetts Institute of Technology researchers have designed an extremely strong and lightweight material by compressing and fusing flakes of graphene.
The new material, a sponge-like configuration with a density of just 5%, can be ten times stronger than steel but much lighter.
In its two-dimensional form, the carbon allotrope is considered to be the strongest of all known materials. Yet, until now, researchers have struggled to translate that two-dimensional strength into useful three-dimensional materials.
MIT’s findings prove the crucial aspect of the new 3D forms has more to do with their unusual geometrical configuration than with the material itself. This suggests that similarly strong, lightweight materials could be made from a variety of materials by creating similar geometric features. Other groups had suggested the possibility of lightweight structures, but lab experiments had failed to match predictions, with some results exhibiting several orders of magnitude less strength than expected. In contrast, the MIT team analysed the material’s behaviour down to the level of individual atoms within the structure and were able to produce a mathematical framework that very closely matches experimental observations.
MIT graphene material test
MIT test a 3D-printed model of their graphene material
The team compressed small flakes of graphene using a combination of heat and pressure. This process produced a strong, stable structure whose form resembles that of some corals and microscopic creatures called diatoms. These shapes, of enormous surface area in proportion to their volume, proved to be remarkably strong.
Wanting to build the strongest material possible, the team created a variety of 3D models and then subjected them to various tests. In computational simulations, which mimic the loading conditions in the tensile and compression tests performed in a tensile loading machine, one of their samples had 5% the density of steel, with ten times the strength.
Using a high-resolution, multi-material 3D printer, the MIT researchers have been able to configure what they believe to be the strongest material known. Mechanically tested for their tensile and compressive properties, and their mechanical response under loading using the team’s theoretical models, the results from the experiments and simulations matched accurately.
These results rule out a possibility proposed by other research groups: that it might be possible to make 3D graphene structures so lightweight that they would be lighter than air, and could be used as a durable replacement for helium in balloons. The MIT research shows that at such low densities, the material would have sufficient strength and would collapse from the surrounding air pressure. But researchers say many other possible applications could be feasible.
“You could either use the real graphene material or use the geometry we discovered with other materials, like polymers or metals,” said Markus Buehler, the head of MIT’s Department of Civil and Environmental Engineering and the McAfee Professor of Engineering. “You can replace the material itself with anything. The geometry is the dominant factor. It’s something that has the potential to transfer to many things.”
These shapes, known as gyroids, are so complex the researchers doubt they could be made using conventional manufacturing methods. As well as being used with metals and polymers, the team say the geometry could even be applied to large-scale structural materials and possibly in filtration systems for water or chemical processing due to the tiny pore spaces in the shape.
“This is an inspiring study on the mechanics of 3D graphene assembly,” said Huajian Gao, a professor of engineering at Brown University, who while not involved in the study, has followed it extensively. “The combination of computational modelling with 3D printing-based experiments used in this paper is a powerful new approach in engineering research. It is impressive to see the scaling laws initially derived from nanoscale simulations resurface in macroscale experiments under the help of 3D printing.”