Virginia Tech materials researchers selected to improve military armor

Virginia Tech has been selected by the Army Research Laboratory to establish a Materials Center of Excellence. The center will develop polymer-based materials to protect personnel and equipment against weapons attack. The center will also offer graduate student and postdoctoral scholar mentorship and undergraduate research programs.

The Multilayered Technologies for Armored Structures and Composites (MultiTASC) Materials Center of Excellence involves researchers from eight interdisciplinary research groups, two colleges, and six academic departments at Virginia Tech, who will team with personnel at the Army Research Lab Weapons and Materials Research Directorate (ARL-WMRD). Timothy E. Long, professor of chemistry in the College of Science, and Romesh C. Batra, professor of engineering science and mechanics in the College of Engineering, both at Virginia Tech, are the co-technical directors.

"The MultiTASC center offers a unique, interdisciplinary team focused on providing polymeric materials-based solutions for lightweight Army systems with increased functionality, structural protection, and improved reliability," said Long.

The ARL award provides $500,000 per year, potentially renewable for nine years, totaling approximately $4 million, Long said. "It is a prestigious award for Virginia Tech. These funds will have a tremendous impact on advancing nanotechnology research on campus. Moreover, the synergy with Virginia Tech's Institute for Critical Technology and Applied Science will ensure a state-of-the-art research facility to foster collaborations and interdisciplinary approaches to science and engineering."

In recent decades, low-weight, high-performance polymeric materials and composites have revolutionized advanced commercial and military technologies. Polymers continue to replace heavier metals and metallic alloys and new technologies range from biomaterials and electro-optical devices to alternate energy sources and nanotechnology.

The Virginia Tech MultiTASC center researchers will develop structural materials with chemical resistance, thermal stability, and fracture resistance; transparent materials that are self-healing with anti-reflection and anti-abrasions surfaces, and new, efficient manufacturing processes to create multi-functional, multi-layered materials.

The first year's research and development will focus on transparent thermoplastics that are durable, such as for ballistic resistant, self-healing visors and windshields, to allow personnel to see threats while being protected. Lighter weight materials will also save energy while increasing maneuverability. The Virginia Tech researchers' past discoveries and achievements with molecular structures enable them to tailor materials at the sub-molecular (nanoscale) level to have the necessary composition and abilities for specific tasks.

"Fundamental science and engineering also enable us to engineer corrosion resistance, chemical agent resistance, more durable adhesives, and self-repairing technologies for aircraft and munitions," Long said.

A related MultiTASC objective is tailored multifunctional protective coatings with multilayer structures. Research will focus on light management in nanoscale, protective polymer thin films, including highly efficient nanoparticle anti-reflection coatings and finely-controlled linear and nonlinear absorption properties. The researchers will develop the coatings, assess their durability, and develop versatile coating technologies for rapid implementation on diverse substrates.

ARL-WMRD will provide technology transfer of films, coatings, and self-assembled surfaces, Long said. But researchers at the Advanced and Applied Polymer Processing Institute (AAPPI) in Danville, a research component of the Institute for Advance Learning and Research, will do technology transfer of processes for creating thicker multilayered materials, such as for light weight personal armor and vehicle protection.

Technology for simultaneous fabrication of multiple layers (coextrusion) is proposed for producing of multifunctional transparent armor in an economical, efficient manner, with fewer steps. In addition to transparent thermoplastics, processes for multilayer coextruded or laminated ballistic composite structures will be developed. Researchers at Virginia Tech and at ARL will do characterization and fabrication of likely composites, and pilot-plant scale processing refinements will be carried out AAPPI, which houses many types of equipment, such as injection molders and melt-spin equipment. A Leistritz micro27 twin-screw extruder can blend powders, resins, and liquids into new polymer materials that can be molded into products. And wetlay equipment combines different materials in solution then creates composite sheets in a process similar to paper making. The sheets can be compression molded into components for automotive or military applications.

Work on assessing the ballistic performance of layered polymer composites will start soon. Virginia Tech recently completed work on computationally ascertaining the ballistic limit of 28-layer Kevlar woven soft body armor. "Our primary goal is to prevent catastrophic failure of personnel body armor and vehicles by accurately characterizing the mechanical properties of protective thermoplastics for new and improved multilayered composites," said Batra.

The researchers will augment standard impact and ballistic tests done in the lab by testing the composite specimens on test dummies in collaboration with the Center for Injury Biomechanics at Virginia Tech. "This will produce a more realistic evaluation and validation of the exceptional toughness and energy absorption capabilities of the synthesized multilayered composites," Batra said. The optimized protective composites will then undergo ultra high strain rate testing by ARL.

The ARL-WMRD also asked the MultiTASC center to look at the use of interface tailored nanofillers in protective materials. Nanofillers are nanoscale structures, such as tube-shaped molecules or modified clay molecules, that can be arranged within a layer of material to increase its strength, add EMI shielding, and other attributes.

The Virginia Tech team was selected based on their experience and record of achievement. "MultiTASC faculty expertise spans molecular design, modeling and constitutive behavior, thin film performance and characterization, morphology and mechanical performance, and analytical characterization," said Long.

The new center will be positioned administratively within the Virginia Tech Macromolecules and Interfaces Institute (MII), which will provide education, outreach, administrative, and technology transfer support. The MultiTASC center laboratory and office space will be located at the Institute for Critical Technology and Applied Science (ICTAS) building in the Virginia Tech Corporate Research Center. The Advanced Materials Characterization Facility, also in the ICTAS building, has instrumentation for the characterization of nanostructures.

MII, an interdisciplinary group with more than 40 faculty members spanning five colleges, will team with ARL-WMRD and commercial partners to develop and commercialize products for the DoD, and AAPPI will work with R&D companies, such as Luna Innovations Inc.

"The MultiTASC center will establish collaborative partnerships with various local industries including Luna Innovations and Nanosonic in the Blacksburg area, and research partnership with the Institute for Advanced Learning and Research in Danville," said Long. "Center researchers will develop advanced technologies and a critical component is the transition to both local and international manufacturing partners."

For example, "Strongwell (Bristol, Va.) is very interested in participating with Virginia Tech's Material Center of Excellence in the development of advanced materials for our nation's soldiers and their vehicles," said Glenn Barefoot, corporate marketing manager. "We have supplied pultruded FRP (fiber reinforced polymer) materials for two different applications in Iraq and look forward to the production of better, more advanced FRP materials through Virginia Tech's research work. Strongwell has cooperated on several research and development programs with Virginia Tech since 1996 and we have been extremely pleased with the outcome of our joint efforts," Barefoot said.

Existing relationships with Kraton Polymers of Houston, Solvay of Atlanta, and Eastman Chemical of Kingsport, Tenn.) will also serve as springboards for new technology development, Long said.

Co-investigators at Virginia Tech with Long and Batra are Randy Heflin, associate professor of physics, and John R. Morris, associate professor of chemistry in the College of Science; Nakhiah Goulbourne, assistant professor of mechanical engineering; Jack Lesko and Mike Hyer, both professors of engineering science and mechanics, and Garth L. Wilkes, professor of chemical engineering in the College of Engineering; AAPPI Director Ronald D. Moffitt, and MII director S. Richard Turner.