The freefall of grapefruit from 10 m does not damage the pulp, the Arapaimas fish living in the Amazon resist the attack of piranhas’ triangular teeth arrays, Shells of the abalone sea creature are hard and fracture resistant, ……….
In the above instances, the nature uses hierarchical structures to provide for protection against extreme loads.
Inspired by these examples of living creatures using hierarchical structures for protection, scientists have developed a new ‘architected material’ called Proteus (after the shape-changing mythical god) which has similar properties.
Proteus, the new lightweight material (only 15% of steel density) is both highly deformable and ultra‐resistant to dynamic point loads thus is non-cuttable by an angle grinder and a power drill.
It is metallic foam made from alumina ceramic spheres encased in a cellular aluminium. This new metallic-ceramic, hierarchical structure, is susceptible to internal vibrations under localized loads. These oscillations are designed to occur when a rotating cutting tool encounters a ceramic sphere on its path. The contact with the ceramic segment produces a localized load on the rim of a rotating disc, which leads to high-frequency, out-of-plane vibrations.
When cut with an angle grinder or drill, the interlocking vibrational connection created by the ceramic spheres inside the casing blunts the cutting disc or drill bit. The ceramics also fragment into fine particles, which fill the cellular structure of the material and harden as the speed of the cutting tool is increased.
Proteus seems to have industrial applications in making bike locks, lightweight armour and protective equipment for professionals who work with cutting tools.
Szyniszewski, S., Vogel, R., Bittner, F. et al. Non-cuttable material created through local resonance and strain rate effects. Published: 20 July 2020. Scientific Reports 10, 11539 (2020). DOI: https://doi.org/10.1038/s41598-020-65976-0