Researchers said the strength of the system, which does not require adhesives or fasteners, was not anticipated “at all”.
The structures were created by visiting graduate student Xinyu Wang and professor Randall Kamien of the University of Pennsylvania in collaboration with Simon Guest from the University of Cambridge.
Wang built a triangle shape with tilted walls using kirigami. Similar to origami, the technique allows materials to be cut and reconnected using tape or glue.
Instead of removing excess flaps from the triangles, however, Wang left them in place. The researchers discovered that although the triangles were not particularly strong on their own, they could support a much greater force than expected when arranged in a repetitive design.
“Here was this structure that didn't require tape, it had cuts, and it was really strong,” said Kamien. “Suddenly, we have this system that we hadn't anticipated at all.”
Wang made several versions out of materials including paper, copper, and plastic. She also made versions where the flaps were taped, cut or damaged. Using industry-grade tension and compression testing equipment at the Laboratory for Research on the Structure of Matter, the team found that the structure could support 14,000 times its own weight. The tilted, triangular design was strongest when the flaps were undamaged and untaped, and it was also stronger than the same design with vertical walls.
With the help of Guest, the researchers realised that two deviations from typical kirigami rules were key to the structure's strength. When the walls of the triangles were angled, any force applied to the top was translated into horizontal compression within the centre of the design. They also found that the overlap from leaving the flaps in place allowed the triangles to press up against their neighbours, helping distribute the vertical load.
One possible application could be to make inexpensive, lightweight and deployable structures, such as temporary shelter tents that are strong and durable but can also be easily assembled and disassembled. The structures – which have the slightly tongue-in-cheek name ‘Interleaved Kirigami Extension Assembly’ – could also be used as furniture, claimed Kamien. “Some day, you'll go to Ikea, you fold the box into the furniture, and the only thing inside is the cushion. You don't need any of those connectors or little screws.”
An announcement of the work predicted “endless” other possibilities for the structures.
The research was published in Physical Review X.
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