Personal protection equipmentNanostructured material stronger than a speeding bullet
Providing protection against impacts from bullets and other high-speed projectiles is more than just a matter of brute strength; while traditional shields have been made of bulky materials such as steel, newer body armor made of lightweight material such as Kevlar has shown that thickness and weight are not necessary for absorbing the energy of impacts; new tests of nanostructured material could lead to better armor against everything from gunfire to micrometeorites
Providing protection against impacts from bullets and other high-speed projectiles is more than just a matter of brute strength. While traditional shields have been made of bulky materials such as steel, newer body armor made of lightweight material such as Kevlar has shown that thickness and weight are not necessary for absorbing the energy of impacts. Now, a new study by researchers at MIT and Rice University has shown that even lighter materials may be capable of doing the job just as effectively.
The key is to use composites made of two or more materials whose stiffness and flexibility are structured in very specific ways — such as in alternating layers just a few nanometers thick. The research team produced miniature high-speed projectiles and measured the effects they had on the impact-absorbing material.
The results of the research are reported in the journal Nature Communications, in a paper co-authored by former postdoc Jae-Hwang Lee, now a research scientist at Rice; postdoc Markus Retsch; graduate student Jonathan Singer; Edwin Thomas, a former MIT professor who is now at Rice; graduate student David Veysset; former graduate student Gagan Saini; former postdoc Thomas Pezeril, now on the faculty at Université du Maine, in Le Mans, France; and chemistry professor Keith Nelson. The experimental work was conducted at MIT’s Institute for Soldier Nanotechnologies.
The team developed a self-assembling polymer with a layer-cake structure: rubbery layers, which provide resilience, alternating with glassy layers, which provide strength. They then developed a method for shooting glass beads at the material at high speed by using a laser pulse to rapidly evaporate a layer of material just below its surface. Though the beads were tiny — just millionths of a meter in diameter — they were still hundreds of times larger than the layers of the polymer they impacted: big enough to simulate impacts by larger objects, such as bullets, but small enough so the effects of the impacts could be studied in detail using an electron microscope.
Seeing the layers
Structured polymer composites have previously been tested for possible impact-protection applications. But nobody had found a way to study exactly how they work — so there was no way to systematically search for improved combinations of materials.
The new techniques developed by the MIT and Rice researchers could provide such a method. Their work could accelerate progress on materials for applications in body and vehicle armor; shielding to protect satellites from
