A form of 3D-printed chain mail can alternate between being flexible and rigid as needed, meaning it could be used for more comfortable medical supports, strong but flexible military armour or even temporary bridges.
at the California Institute of Technology and her colleagues used 3D printers to create several versions of chain mail using link shapes such as octahedrons, pyramids and rhomboids. The designs were printed in one go using plastic for some samples and aluminium for others.
With no compression forces pushing on them, these fabrics are flexible and easily draped over objects. But under compression, their links jam together, making the materials up to 25 times stiffer. In one experiment, the team used a plastic fabric weighing just tens of grams to create an arch supporting a 1.5-kilogram weight.
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Daraio says that a smart fabric that can adapt its stiffness may lead to innovations in a range of fields. A lightweight fine mesh of the material could make medical supports for broken bones, but a much larger grid of metal links could even create tents or temporary bridges.
鈥淚f you think about the medieval chain mail that we鈥檝e seen in museums, they were incredibly effective at protecting against blades and cuts, but not against blunt impacts. That鈥檚 precisely because they are so drapable,鈥� says Daraio.
鈥淩igid armour is certainly more effective at protecting against blunt impact, but it鈥檚 not as comfortable to wear. There is, of course, a trade-off. The concept behind what we did was that we can effectively convert the chain mail on command.鈥�
The team found that friction wasn鈥檛 involved in the jamming of the fabric and that even chain mail with smooth links could be made rigid.
Daraio says that it is the configuration that the links take on under compression that creates stiffness, just like rice in a funnel usually flows like a liquid but occasionally jams solid, or how vacuum-packed packets of coffee beans become rigid.
The shapes are pushed together in such a way that the links come into contact with each other in several places, preventing movement and creating a rigid whole.
Nature
