Researchers Design Stiffest 3D Printed Material

In a collaborative effort between researchers at ETH Zurich and MIT, a material was 3D printed with a stiffness that comes notably close to the theoretical maximum limit of a stiffness to weight ratio possible according to the laws of physics. The stiffest format of any given material is one that’s completely solid, but that’s also the heaviest format of that material, which is often too heavy for the intended application (as well as wasteful). Take planes: their frames need to be rigid so that planes don’t crumble to the slightest turbulence, but to build their frames out of solid steel would make them far too heavy to get airborne.

Instead, engineers use geometry to extract the most stiffness out of the least amount of material; arches, trusses, and girdles are all construction methods that arrange materials into their stiffest geometry in order to minimize material usage and volume while maintaining enough stiffness for the specific task.

But Dirk Mohr, Professor of Computational Modeling of Materials in Manufacturing at ETH Zurich, knew there were stronger geometries available, explaining, "The truss principle is very old; it has long been used for half-timbered houses, steel bridges and steel towers, such as the Eiffel Tower. We can see through truss lattices, so they are often perceived as ideal lightweight structures. However, using computer calculations, theory and experimental measurements, we have now established a new family of plate-lattice structures that are up to three times stiffer than truss-lattices of the same weight and volume."

The plate-lattice is not only breaking records with its stiffness, a measurement of resistance to elastic deformation, but also strength, which is resistance to irreversible deformation. And unlike most construction methods, the stiffness and strength are equal in all three dimensions. That can not be said for the Eiffel Tower as it was designed to resist mostly a downward force, or gravity. It would take little lateral force to knock the Tower over and thankfully King Kong doesn’t exist to test that theory.

The lattice structures were designed with computer models that calculated their mechanical properties on the fly. They were then 3D printed at a micrometer scale for testing. Mohr notes that the strength gains would apply to all materials and at all scales. “Lightweight construction, the current cost of which limits its practical use to aircraft manufacturing and space applications, could then also be used for a wide array of applications in which weight plays a role," he said.

From skyscrapers to medical implants to automotive parts, they could all be made lighter and stronger with these 3D printed lattice structures. "When the time is right, as soon as lightweight materials are being manufactured on a large scale," Mohr says, "these periodic plate lattices will be the design of choice."