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A joint team of researchers from ETH Zurich and MIT have developed material architectures which could feasibly be the stiffest material structures possible for a given weight. The innovative lattice structures could be manufactured using additive manufacturing techniques.

The research team behind the strong, lightweight and incredible stiff material architectures is led by Dirk Mohr, a professor of Computational Modeling of Materials in Manufacturing and a specialist in developing computational models for the design and manufacturing of lightweight materials and structures. Working together, the researchers and Mohr successfully came up with a plate-lattice structure that was very stiff and equally strong in all three dimensions.

Interestingly, because it is possible to theoretically determine how stiff lattice structures or other geometries with internal voids can be, the researchers have determined their material structure is close to the maximum stiffness possible.

The strength and stiffness of the structure is owed to the plate-lattice geometry—a type of lattice that offers more advantages over more commonly used trusses, which typically come in the form of posts, struts, rafters, etc.

“The truss principle is very old,” said Professor Mohr. “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.”

To add to that, the researchers say that the plate-lattices are not just stiffer than their truss-lattice counterparts, but they are also stronger. In fact, the structures reportedly approach their theoretical maximum values for strength.

In developing the innovative lattices, the research team created computational models which they subsequently 3D printed from plastic using a micrometer-scale printing system or further evaluation. Though the researchers worked with micrometer printed models, the plate-lattice would offer the same benefits for a structure printed at any scale.

At this stage, the researchers emphasize that their research is a step ahead of the additive manufacturing technologies available. That is, because of the costs associated with 3D printing—especially for metal AM—the plate lattice structures would be prohibitively expensive to produce.

“If these kinds of lattices were to be additively manufactured from stainless steel today, they would cost as much per gram as silver,” Mohr elaborated. “But the breakthrough will come when additive manufacturing technologies are ready for mass production. 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.”

Once the cost of additive manufacturing has been driven down by advancements and adoption, the lattice structures could even help to reduce costs, as less material would be needed in comparison to a solid object.

Outside of the aerospace industry, the plate-lattice architecture could be implemented to improve medical implants, laptop casings and even vehicle structures. “When the time is right, as soon as lightweight materials are being manufactured on a large scale, these periodic plate lattices will be the design of choice,” Mohr concluded.

The innovative research project conducted by ETH Zurich and MIT was recently published in the journal Advanced Materials in the study “3D Plate‐Lattices: An Emerging Class of Low‐Density Metamaterial Exhibiting Optimal Isotropic Stiffness.”