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Thomas Attard, Ph.D., a professor in the Department of Civil, Construction, and Environmental Engineering, is using highly specialized equipment at Oak Ridge National Laboratory to explore new variations in a variety of polymer matrix composites.

Attard2016 175Thomas Attard, Ph.D.Attard and a team of researchers (see sidebar) have received two in-kind support grants from the Department of Energy (DOE) User program to run experiments at Oak Ridge’s Center for Nanophase Materials Sciences (CNMS). The team is utilizing the facility’s dynamic mechanical analyzer (DMA) and nano-infrared equipment (Nano-IR) to study on a nanoscale how manipulating the chemistries, diffusity, and thermodynamic equilibrium of epoxy can change the properties of an interfacial reaction with polyurea. One of the applications of this discovery is to carbon-fiber technology. The DOE estimates the global market for carbon-fiber technology to grow to $25.2 billion by 2020, representing a continued annual growth rate of 15.3 percent and a global value demand of 210,000 metric tons.

Research Team

Attard's team of researchers include a postdoctoral student and two Ph.D. candidates. Each one is focused on a different area of research. For images related to their research, click here.

weixing sun

Weixing Sun, Ph.D., is a research scientist who analyzes infrared spectra of chemical bonds, identification of new bonds in various IEPM, and spread/density of bonds.

zhenhua si

Zhenhua Shi is a Ph.D. candidate who works with DMA to identify damping ratios and loss moduli. He also develops molecular dynamics models of various IEPM reactions to capture the statistics of chemical-bond structures.

li he

Li He is a Ph.D. candidate who works on chemical imaging of IEPM for various diffusity states.

“It starts with a simple reaction of a two-part epoxy, analogous to the two-part epoxy that you would buy at a hardware store,” Attard said. “Each part is non-reactive, but when you mix the two parts together, a reaction starts. Because of certain undesirable properties contained in the cured epoxy, we decided to interrupt the curing process, or reaction, of those two epoxy parts by adding certain elastomeric polyureas. Depending on the level of reactivity of the epoxy system at the time when we interrupt its curing cycle, we are able to create a brand-new material that possesses very desirable and tunable properties.”

The result is the formation of a previously unknown material they are calling Interfacial Polymer Matrix (IEPM)—a material with epoxy and polyurea parts that look unchanged from their original configurations to the naked eye but that are actually radically altered on a chemical interface level that can be seen by using Nano-IR equipment. “We are able to perform chemical imaging and infrared spectroscopy on a 10 nanometer-size region at the point of contact, and identify new chemical bonds and bond-motion modes of each type of IEPM,” Attard said. “We also found that the new IEPM material is tunable, meaning that we can design the molecular structure of each IEPM reaction at its interface. If we apply IEPM to carbon fiber (CF) technology, we suddenly inject a multitude of combined properties, depending on when we interrupt the curing processes, making CFs more resilient, sustainable, durable, and cost-effective.”

The different properties mean that the material is suited to a wide variety of engineering systems. For example, variations in fracture toughness, impact resistance, or damping could create a high-strength material that is suited for helmets, or another that is suited to automotive parts, or another that is better suited to bridge construction. “If we 'cook' the epoxy and polyurea when the epoxy initially mixes or if we wait 10 minutes or if we wait 2 hours, we can acquire very different chemical structures, with different chemical bond density and distribution. So if our desire is to use IEPM to withstand a hurricane disaster as opposed to an automotive crash or even a ballistics environment, each incurring a very different dynamics scenario, each IEPM, while it looks the same on the outside, is very different under a microscope, thus enabling it to withstand different dynamics.”

Although the materials can be manipulated to suit a wide range of applications, Attard is currently looking specifically at creating a more durable energy-dissipative connection detail for highway bridges. “For bridges, IEPM can be used to re-design the connection detail at the location where the girder connects to the top of the bent cap,” he said. “We are currently examining the I-10 bay-way bridges across Mobile Bay that may realistically experience disastrous hurricane conditions. However, IEPM can also be tailor-designed, using the same chemical processing, to develop a connection detail for bridges subject to devastating seismic forces. We simply interrupt the curing kinetics of epoxy, thereby controlling the energy transfer mechanism and maximizing bridge protection.”