Materials inspired by chain mail change from flexible to rigid when pressurized.This fabric was developed by Chiara Daraio and her colleagues at the California Institute of Technology and can become The hardness is more than 25 times that of the original state, Team report nature.
The researchers built it with hollow octahedral subunits, which are interlocked but able to move with each other. Its special properties are based on a process called “interference”. When pressure is applied to the material, the octahedral unit becomes immobile. The fabric behaved as if it suddenly became an entity. Similarly, chain mail exhibits high tensile strength to protect fighters, but can fit the body.
Such structured materials-those that can be shaped as required and can be solidified and loosened again on command-are of interest to many technical applications. For example, they can be used as easy-to-transport construction materials for temporary buildings or bridges.
Daraio and her team built this fabric with three-dimensional “particles” made of pillars that form an octahedral cage, each of which is interlocked with its nearest neighbor. Adjacent octahedrons rotate 90 degrees to each other and connect at corners. In order to make the material withstand the pressure, the researchers put it in a plastic bag and evacuated air from it, so that the pressure on the structure corresponds to the difference between the external pressure and the internal pressure. Then, they exposed the fabric to a pressure between 0 and 93 kPa to observe its changing properties.
In fact, clogging has a well-known and widely used effect on granular materials Even mayonnaiseFor example, this happens when you pour rice through a funnel. If you do this too quickly, the grain will clog and block the passage. The sand hardens under pressure and exhibits similar behavior. However, there is a fundamental difference between grain and chain mail-like fabrics. Although grains only become clogged when they shrink, fabrics made of interlocking components can also be cured under other stresses—for example, when it is bent or stretched.
Using computer simulations, the team studied how disturbances occur at the level of individual components in the fabric and what factors affect these mechanical properties. In addition, the researchers built similar fabrics with building blocks of different shapes. These materials include the rings of the classic chain mail, as well as the octahedrons with different angles or fewer cross braces. The team found that such fabrics have consistent properties: the degree to which they harden under pressure depends only on the number of times the polymorphic elements touch each other on average—regardless of the exact structure.
The properties of this chain mail-like material may still be surprising.Laurent Orgéas, a materials researcher at the University of Grenoble Alpes in France, pointed out in the comments nature Measurements made by Daraio’s team show Signs of nonlinear behavior under stress, Which shows the unusual material properties. In addition, the fabric as a whole maintains a fairly flat shape. Also worth studying is the three-dimensional chain mail structure. An idea might include a “smart” material that changes shape when an electric current or heat is applied.
This article originally appeared in Science spectrum And reprinted with permission.