Researchers at Harvard University have developed a way to 3D-print a cellular composite with record lightness and stiffness using an epoxy resin. This is the first time that epoxy is used for 3D-printing, and it could potentially lead to the development of new lightweight architectures for more efficient and affordable wind turbines, faster cars, and lighter airplanes.
Getting materials that are both light and strong is difficult since most of the lightweight materials are extremely weak while the heaviest are very strong. However, one exception is balsa wood, which has a density as low as 40 kg per cubic meter (2.5 lb per cubic foot) but is still very strong, thanks to a microscopic structure that features a highly effective mix of cellulose and lignin fibers. Balsa wood is therefore used in applications where light but strong structures are critical, from the blades in wind turbines to the chassis of model airplanes and helicopters.
The problem with balsa wood is that 95% of it comes from a single country – Ecuador
Scientists at Harvard have now come up with a way to manufacture a cellular composite that’s even better than balsa wood, making it more reliable since it has no structural defects that wood naturally has.
Here is a short clip of the composite being printed.
The researchers took inspiration from the microscopic structure of balsa, which is mostly hollow and in which only the cell walls are carrying the load. They built their new composite using an epoxy-based resin containing nanoclay platelets to increase viscosity, as well as two types of fillers – silicon carbide “whiskers” and discrete carbon fibers.
The researchers can even control the exact stiffness of the material by changing the orientation of the fillers as needed. Orienting the silicon carbide whiskers perpendicularly to the direction which will face the most load makes the material stronger.
According to principal investigator Prof. Jennifer A. Lewis, their research is a significant step because it paves the way for 3D-printing using materials, such as epoxies, which can be used for structural applications, as opposed to the thermoplastics that your standard 3D printer uses.
This resin is as stiff as wood and as twice as strong as the strongest polymer composites
This technology could lead to advances not only in structural materials, but also in conductive composites.
A paper describing the advance appears in the journal Advanced Materials.