Composite Research: Exploring applications
Some day in the not too distant future, American soldiers might find themselves traveling in military vehicles protected by a lightweight material engineered at Lamar University. When those soldiers exit their vehicles and enter enemy territory on foot, their gear might bring an extra layer of security also made possible by research conducted in the laboratory of Lamar professor Robert Yuan.
Yuan, who joined the Lamar faculty in 2003, chairs the Civil Engineering Department, holds the Andrew and Joyce Green Chair in Engineering and directs the Green Composite Research Center. His expertise in composites research brought him to Lamar after spending most of his career at University of Texas at Arlington. Now, Yuan is bringing his composites expertise to bear on U.S. military projects. Yuan has been at work on research for the U.S. Space Missile Defense Command, a joint research project with Auburn University.
“We’re doing the fundamental research for military applications,” Yuan said. “This research is developing the material for high-strength, lightweight and impact-resistant applications.” The research eventually will make the move from the lab to practical uses in military and construction ventures.
The research for the Space Missile Defense Command focuses on nanocomposites. At Auburn University, researchers produce single-walled carbon nanotubes (SWNT) that serve as one component in the materials being developed. Once the nanotubes arrive at Lamar University, they are combined with a polymer—in this case polyester—to form a strong, lightweight composite material. As the prefix “nano” implies, the nanotubes are small—black circles of carbon-fiber material about 50 millimeters in diameter and less than half a millimeter thick. Nanotubes are turned into nanocomposites when meshed with polymers in the Lamar University laboratory. Then, they are tested in the Green Composite Research Center housed in the Cherry Engineering Building on campus.
“Testing is very important in composite materials research. Many times the computation analysis is very limited because of the complication of the materials architecture,” Yuan said. “You make an initial analysis and design, and then manufacture one in the testing laboratory. The design will be modified based on the test results.” The fundamental assessment program includes tests of tension, compression, flexibility and impact. The objective is to obtain the necessary mechanical properties for material evaluation. All test equipment is attached to data acquisition systems to record loads, deformations, stresses and strains. For the impact test, data collected includes impact forces, impact time, energy absorption and impact velocity.
“Generally, composite materials have much higher strength-to-weight ratio and stiffness-to-weight ratio than steel,” Yuan said. “But compression and bending is not that strong, so you need to customize the design and optimize the material to use the best composite characteristics possible.”
So far, the project has focused largely on composites comprised of carbon fiber nanotubes and vapor growth carbon fiber (VGCF) with glass fiber and polyesters. Yuan also is considering using other polymers such as vinyl ester or epoxy and other fibers such as Kevlar. “It’s so difficult to make the optimal combination. You can put a lot of fiber in one specimen, which is not economic, and you can put lots of polymer in there, which may not be very strong. You have to make it lightweight, strong and satisfy economic design. That’s what makes it difficult. That is very challenging,” Yuan said.
Getting the right mix of the right materials is the key to composites research whether the composites are headed to the battlefield or a construction site. Yuan’s interest in composites research developed from his structures, mechanics and materials background. Twenty-five years ago, Andrew Green, for whom the research center and the endowed chair at Lamar are named, asked Yuan, then a professor at University of Texas at Arlington, to perform some composites research testing for his Fort Worth company. Yuan had been “a concrete guy.” He referred to concrete as a type of composite, too, since it is formed from a mix of cement, water and aggregates. As Yuan experimented with new composite materials formed from fibers and a polymer matrix, he was hooked. “It’s just been fascinating material,” Yuan said.
Potential applications for composites seem almost limitless. Prior to coming to Lamar University, Yuan was involved in projects using composite materials to build vehicular bridges, pedestrian walkways and cooling towers, a function composites perform ideally since they are not subject to corrosion like metal construction materials. His computer stores photos of composite rebar, which can be used in lieu of its steel cousin for bridge decking, and composite columns used in building a wastewater treatment plant.
Yuan, who moved to Lamar at the urging of Green and several Lamar administrators, considers the composite research program here under construction as he actively seeks to attract more faculty and student researchers and more research dollars to support their work. The Space Missile Defense Command project has no firm timeline for delivery of an end result. Research continues with periodic meetings to review progress and funding. Though Yuan is unsure when he and other researchers will complete their work, he feels confident they will be able to deliver what officials are seeking. When they do deliver, soldiers in military attire and others depending on U.S. government-issued gear could have Lamar University to thank for providing them with strong, lightweight, corrosion-resistant equipment made from composite materials.