Engineers have taken inspiration from natural materials such as grapefruit skins to create an “uncuttable” material that repels angle grinders, drills and even high-pressure water jets.
The lightweight material is made of ceramic spheres encased in a cellular aluminium structure, and “turns back” the force of cutting tools.
It’s described as the first-ever “uncuttable” manufactured material.
The researchers say the material could be used to make bike locks, lightweight armour and protective equipment for people who work with cutting tools.
It’s named Proteus, after a Greek sea deity with the power to change shape, say the researchers at Durham University, UK, and Fraunhofer Institute for Machine Tools and Forming Technology IWU in Chemnitz in Germany.
The researchers were inspired by the tough cellular skin of grapefruits and the shells of molluscs.
Lead author Dr Stefan Szyniszewski, assistant professor of applied mechanics in the department of engineering at Durham University, said: "We were intrigued by how the cellular structure of the grapefruit and the tiled structure of mollusc shells can prevent damage to the fruit or the creatures inside, despite being made of relatively weak organic building blocks.
"These natural structures informed the working principle of our metallic-ceramic material, which is based on dynamic interaction with the applied load, in contrast to passive resistance.
"Essentially, cutting our material is like cutting through a jelly filled with nuggets. If you get through the jelly you hit the nuggets and the material will vibrate in such a way that it destroys the cutting disc or drill bit.
"The ceramics embedded in this flexible material are also made of very fine particles which stiffen and resist the angle grinder or drill when you're cutting at speed in the same way that a sandbag would resist and stop a bullet at high speed.
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"This material could have lots of useful and exciting applications in the security and safety industries. In fact, we are not aware of any other manufactured non-cuttable material in existence as of now."
The researchers say the dynamic response of the new material is similar to that seen in living creatures.
When cut with an angle grinder or drill, the vibrations created by the ceramic spheres inside the casing blunt the cutting disc or drill bit.
The blade is gradually eroded and eventually rendered ineffective as the force and energy of the disc or the drill is turned back on itself, the researchers say.
In addition, the ceramics fragment into fine particles, which fill the cellular structure of the material and harden as the speed of the cutting tool is increased due to interatomic forces between the ceramic grains.
In this way the adaptive nature of the material further repulses any attack.