The high-performance architected materials, which could be used in aeroplanes, cars or spacecraft, are known as plate lattices and have tuneable mechanical properties, such as stiffness and flexibility.
Built on a much larger scale than in previous projects thanks to additive manufacturing, the structures with custom shapes and tailored properties were made from metal and other materials. They could also find use in construction applications.
“This material is like steel cork. It is lighter than cork, but with high strength and high stiffness,” said Professor Neil Gershenfeld, senior author of a new paper on the work.
The researchers developed a modular construction process in which many smaller components are formed, folded, and assembled into 3D shapes. Using this method, they fabricated ‘ultralight and ultrastrong’ structures and robots that, under a specific load, can morph and hold their shape.
The MIT researchers modified a common origami crease pattern, known as a Miura-ori pattern, so the sharp points of a corrugated structure are transformed into facets. The facets provide flat surfaces to which plates can be attached more easily, with bolts or rivets.
“Plate lattices construction has been so difficult that there has been little research on the macro scale. We think folding is a path to easier utilisation of this type of plate structure made from metals,” said co-lead author Alfonso Parra Rubio.
The way the patterns are designed, folded and cut allows certain mechanical properties, such as stiffness, strength, and flexural modulus (the tendency of a material to resist bending), to be tuned. The researchers encoded this information, as well as the 3D shape, into a ‘creasing map’ that is used to create the kirigami corrugations.
Based on the way the folds are designed, some cells can be shaped so they hold their shape when compressed, while others can be modified so they bend. In this way, the researchers could precisely control how different areas of the structure deformed when compressed.
“Because the flexibility of the structure can be controlled, these corrugations could be used in robots or other dynamic applications with parts that move, twist, and bend,” the MIT announcement said.
To craft larger structures like robots, the team used a modular assembly process, mass producing smaller crease patterns and assembling them into 3D structures. Smaller structures have fewer creases, which simplifies the manufacturing process.
“To make things like cars and airplanes, a huge investment goes into tooling. This manufacturing process is without tooling, like 3D printing. But unlike 3D printing, our process can set the limit for record material properties,” Professor Gershenfeld said.
Using their method, the team produced aluminium structures with a compression strength of more than 62kN, with a weight of 90kg per square metre. The structures were reportedly so strong they could withstand three-times as much force as typical corrugated aluminium.
The technique could be used for many materials such as steel and composites, the team said, making it well-suited for producing lightweight, shock-absorbing components for aeroplanes, cars, or spacecraft.
The researchers found their method can be difficult to model, however. In future, they plan to develop user-friendly CAD design tools for the kirigami plate lattice structures. They also aim to explore methods to reduce the computational costs of simulating a design that yields desired properties.
“Kirigami corrugations hold exciting potential for architectural construction,” said James Coleman, co-founder of the design for fabrication and installation firm SumPoint, who was not involved with the work.
“In my experience producing complex architectural projects, current methods for constructing large-scale curved and doubly curved elements are material intensive and wasteful, and thus deemed impractical for most projects.
“While the authors’ technology offers novel solutions to the aerospace and automotive industries, I believe their cell-based method can also significantly impact the built environment. The ability to fabricate various plate lattice geometries with specific properties could enable higher performing and more expressive buildings with less material. Goodbye heavy steel and concrete structures, hello lightweight lattices!”
Members of the research team also used the technique to create three large-scale folded artworks from aluminium composite, which are on display at the MIT Media Lab. Despite each piece being several metres in length, they reportedly only took a few hours to fabricate.
The work will be presented at ASME’s Computers and Information in Engineering Conference.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.