Angle grinder

Material that cannot be cut would make the ultimate bike lock

Attempting to cut the material with an angle grinder

Dr René Vogel, Technical Leader, in the Fraunhofer Institute for Machine Tools and Forming Technology IWU

Engineers have created the first artificial material that effectively cannot be cut, holding out the promise of lightweight but cut-proof bike locks, security doors and protective clothing.

The team embedded ceramic spheres in aluminium foam to create a material that they could not cut with angle grinders, power drills or water jet cutters. They dubbed it Proteus after the shape-shifting Greek god, for the way the material metamorphosised in different ways to defend against attacks.

“It’s pretty amazing,” says Miranda Anderson at the University of Stirling, UK, who worked on the project. Rather than just being a hard surface that resists external pressure, the material turns the force of the drill or cutting mechanism back on itself, as the ceramic spheres create vibrations that disrupt the external force. “It actually destroys the cutting blade through the sideways jerky vibrations that it creates, or it widens the water jet’s spray,” Anderson says.


The material also has a second defence mechanism. Attempting to cut it the ceramic spheres into smaller fragments which are even harder and act like a very tough sandpaper. “So the attack mechanism causes the material to become more resistant to the attack,” says Anderson. While the angle grinder the team used took 45 seconds to cut through steel armour used to protect against explosive mines, it was rendered inoperative by Proteus.

The only comparable structure in the natural world is diamond, says Anderson, but Proteus is cheaper and lighter, making it practical for a range of applications, from security doors and barriers to shoe soles or elbow pad and forearm guards for workers. She believes it can be mass-produced, as there is no shortage of the metals and ceramics it is made from.

Journal reference: Scientific Reports, DOI: 10.1038/s41598-020-65976-0

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