Researchers find inspiration in nature to improve ceramic armor
ABERDEEN PROVING GROUND, Md. — Future American Soldiers will be better protected in combat by stronger and lighter body armor thanks to innovative work at the U.S. Army Research Laboratory. Materials science engineers are using nature as the inspiration for breakthroughs in additive manufacturing.
"My project is to design a system that can 3-D print armor ceramics that will allow production of parts with graded structures similar to an abalone structure in nature that will improve the ceramic armor's toughness and survivability with lower weight," said Joshua Pelz, a materials science and engineering doctoral candidate at the University of California San Diego. He spent this summer working with Army scientists at ARL's Rodman Materials Science Laboratory at APG to design and build a unique 3-D printer.
Two syringes containing distinct, viscous ceramic slurries are connected to a custom-made auger and print head. Pelz took advantage of his computer programming skills to hack into the 3-D printer, tricking it into using its own fan controls to manipulate the ratio of materials being printed. He designed a custom auger and print head and even used the same 3-D printer to create those parts.
"Josh found a way to implement our ideas into that machine, take apart machine, take out the polymer FDM heads that are built into it, start to look at how to design the machine to incorporate our ceramic slurries and print those slurries into the head but then he had to do a lot of really basic work looking at how to actually hack the machine," said Dr. Lionel Vargas-Gonzalez, Ceramics Synthesis and Processing team lead at the laboratory. "We've got people like Josh who were very gifted and talented and can bring all that kind of capability and use a lot to our advantage it's a huge benefit for us."
Current processing techniques used to create ceramic armor are limited by how engineers can combine materials into a stronger composite material.
"For ceramics, that's a bit of a challenge because with you can't really do what a one-step additive manufacturing process like you could if a metal or a polymer," Vargas-Gonzalez said. "We see this as a next avenue for armor because we're going to be able to, in theory, design armor in a way that we can attach multiple materials together into a single armor plate, and be able to provide ways for the armor to perform better than it can be just based on one material alone."
Hard ceramic materials defeat kinetic energy projectiles by shattering them into pieces and decreasing the projectile's penetration ability, he said.
"You have ceramic armors processed typically right now with dry powder and with hot pressing or sintering — we're able to get really good properties and what I mean by those properties I mean really high theoretical density," Vargas-Gonzalez said. "These particles are able to sinter well and you're getting something that's about 99 to 100 percent fully dense because porosity is one of the main deficiencies of ceramic armor when it comes to being able to withstand threats."
"I think that the main thing that sets my design apart from other additive manufacturing and specifically direct ink writing setups is that I can extrude multiple materials out of a single nozzle and I can also extrude any ratio of this material," he said.
Pelz said he came up with the concept during his undergraduate studies at the Colorado School of Mines. "I started working on this project to create next-generation antennas with graded structures and then transitioned into using armor ceramic materials such as boron carbide and silicon carbide and trying to produce parts that had a gradient or internal structures impossible to produce with traditional ceramic forming techniques," Pelz said.
He hopes to take his work with back to the University of California at San Diego this fall where he will continue to collaborate with Army researchers on the project.
"I hope to use this system that I've designed, as well as the processing of creating these armor ceramics and creating armor ceramic composites to develop both next-generation armor, but also apply it to various other fields such as a biomedical implant," he said. "You could use this same system to produce ceramic implants for say a hip replacement or a knee replacement you could produce the ball that would be put into that that hip joint to actually produce those parts. And so this system gives the ability to produce graded parts — composite ceramic parts — for really any application with any material.
The freedom to easily test ideas in additive manufacturing appeals to Pelz, he said.
"I think the freedom to really explore your ideas and do rapid iterations through your various prototypes allows you to very quickly narrow down your ideas and kind of develop a new piece of equipment or a new technology that might take months or years using traditional subtractive manufacturing processes," he said. "3-D printing and additive manufacturing generally gives someone the ability to really design and create anything they want. It's a very quick process from thinking up a design, modeling that design and actually producing that design."
Additive manufacturing offers great potential, Vargas-Gonzalez said.
"For us, there's a limitless amount of design space that we could probably open up because of additive manufacturing," he said. "One of our biggest challenges is being able to make the materials that are going to give us the right properties."
Pelz said that is one of his motivating factors.
"I think that supporting our Soldiers is of utmost importance and I think they're carrying so much weight that a small reduction in weight anywhere in their package will allow them to go farther and do more for our nation," he said.