This new carbon-based material could be the basis for lighter, stronger alternatives to Kevlar and steel.
A new study by engineers at MIT, Caltech and ETH Zürich shows that the material “nanoarchitected,” a material designed from a precisely patterned nanoscale structure. It could be the way to lightweight armor. Protective coatings, explosion shields and other impact resistant materials
Researchers have fabricated an ultra-light material made from nanometer-sized carbon struts that provide the material’s toughness and mechanical durability. The team tested the material’s flexibility by firing it with tiny particles at supersonic speeds. and found that the material, which is thinner than the width of a human hair Prevents small missiles from passing through.
The researchers calculated that, compared to steel, Kevlar, aluminum and other impact-resistant materials, of the same weight The new material will be more effective at absorbing shock.
“The same amount of our material is more effective at stopping a projectile than the same Kevlar mass,” said Carlos Portela, an assistant professor of mechanical engineering at MIT, who led the research team.
if produced in large quantities This material and other nanoarchitecture materials May be designed to be lighter It is a more durable alternative to Kevlar and steel.
“Knowledge from this work… Design principles for ultra-lightweight impact-resistant materials can be provided. [for use in] effective armor material protective coating and explosion-proof armor It is in demand in defense and aerospace applications,” said co-author Julia R. Greer, Caltech Professor of Materials Science, Mechanics and Medical Engineering whose lab is the leader in materials manufacturing.
The team, which published their work on June 24, 2021, in the journal natural materialincluding David Veysset, Yuchen Sun and Keith A. Nelson of the MIT Institute for Military Nanotechnology and Chemistry, and Dennis M. Kochmann of ETH Zürich.
from brittle to brittle
Nano-architectured materials consist of patterned nanometer-sized structures. which depends on the arrangement method It can provide material-specific properties such as ultra-lightweight and flexibility. As a result, nano-architecture-based materials are viewed as lighter and more durable impact-resistant materials. But this potential is largely untested.
“We only know about their response in the slow transformation regime. While many practical applications are presumed to be in production where nothing is slow to deform,” Portela said.
The team began to study nano-architectured materials under conditions of rapid deformation, such as during high-speed shocks. At Caltech, they fabricated the first nano-architectured material using two lithography. Photon It is a technique that uses a fast, high-powered laser to solidify the microstructures in photosensitive resins. The researchers created a so-called repeating pattern. tetrakaidecahedron which is a lattice consisting of small pillars
Portela, who chose to model this foam-like architecture in carbon materials at the nanoscale, said: “Historically, this geometry has appeared in energy-saving foams” to provide flexible and shock-absorbing properties to conventional rigid materials. “While carbon tends to be brittle, But the smaller arrangements and struts in the nano-architecture material create a ribbed, bendable architecture.”
After formatting the lattice structure The researchers washed the residual resin and placed it in a vacuum furnace at high temperatures to convert the polymer to carbon. By leaving behind the ultra-lightweight carbon nanomaterials.
faster than the speed of sound
To test the flexibility of materials against severe deformation. The team conducted microparticle impact experiments at MIT using laser particle impact testing. This technique targets ultra-fast lasers through a glass slide coated with a thin gold film. which is coated with a layer of small particles in this case, silicon oxide particles, 14 microns wide, when the laser passes through the slide. It creates a plasma, or rapid expansion of gas from gold. which pushes the silicon oxide particles out in the direction of the laser. causing the smaller particles to accelerate towards the target quickly.
The researchers were able to adjust the laser power to control the speed of the microparticles. In their experiments, they explored the velocity range of microparticles from 40 to 1,100 meters per second. which is in the range of supersonic speed
“Supersonic speed is something above about 340 meters per second. which is the speed of sound in air at sea level,” Portela said. “So some experiments are twice as fast as sound. easily.”
by using a high-speed camera They captured video of tiny particles making an impact on nano-architectured materials. They fabricated a material of two different densities — the less dense material had slightly thinner pillars. When comparing the impact response of the two materials They found that the denser the material was more flexible. And smaller particles tend to be embedded in the material rather than directly torn.
to get a more detailed view The researchers carefully cut through the embedded microparticles and materials. and found that in the area under the embedded particles The microscopic columns and beams are crumpled and compacted in response to the impact. But the surrounding architecture remains intact.
“We showed that the material can absorb a lot of energy due to the strut impact mechanism at the nanoscale compared to what is dense and completely monolithic, not nanoarchitectures,” Portela said.
interesting is The team found that they were able to predict the type of damage the material would sustain using a dimensional analysis framework to characterize planetary impacts. It uses a principle known as the Buckingham-ing theorem. This analysis describes physical quantities, such as the velocity of a meteor and the strength of a planet’s surface material, to calculate a “crater efficiency”, or the probability and extent that a meteorite will mine the material.
When the team adapted the equations to the physical properties of the nanoarchitecture films and the size and velocity of the microparticles. They found that the framework was able to predict the type of effect that the experimental data showed.
In the future, Portela said the framework could be used to predict the resilience of the impact of other nanoarchitecture materials. He plans to explore various nanostructures. including other materials besides carbon and how to expand the production scale All with the goal of designing a more durable and lighter protective material.
“Nano-architectured materials tend to be true cushioning materials,” Portela said. “There is still a lot we don’t know about them. And we are embarking on this path to answer these questions and open the door to their widespread use.”
Reference: “Supersonic Shock Flexibility of Carbon Nanoarchitectures” by Carlos M. Portela, Bryce W. Edwards, David Veysset, Yuchen Sun, Keith A. Nelson, Dennis M. Kochmann and Julia R. Greer. , 24 June 2021, natural material.
Some of this research was supported by the U.S. Naval Research Office, Vannevar Bush grants, and the U.S. Army Research Office. through the Military Nanotechnology Institute at MIT