Carbon Fiber in the Fast Lane
Composite materials have been used for thousands of years. Ancient peoples knew that mixing two or more materials could yield a new material with far better properties than each ingredient alone. The earliest composites were mud bricks reinforced with straw, which allowed prehistoric humans to build larger and more durable structures.
Today’s composites are made from microscopic fibers, typically made of carbon or glass, that are embedded in a plastic matrix—and just as composites revolutionized ancient construction, they now stand to radically change the automotive industry.
Carbon-fiber and advanced glass-fiber composite materials can be just as strong and stiff as steel—the current material used in automotive structures—but are 30 to 70 percent lighter.
Since lighter vehicles have better fuel economy or driving ranges (for combustion and electric cars, respectively), modern composites could significantly improve auto efficiency and reduce transportation costs.
So why haven’t they taken over?
“Engineers have over 100 years of testing data, design rules, and standards for metals,” said José L. Martínez Collado, a PhD student in energy science and engineering at the University of Tennessee’s Bredesen Center. “With composites, performance depends on things like fiber direction, resin content, and how the part was processed, which makes modeling and certification more complex.”
Fortunately, UT is the perfect place to fill the knowledge gap. In 2015, UT and Oak Ridge National Laboratory (ORNL) established the Institute for Advanced Composites Manufacturing Innovation (IACMI), a Manufacturing USA institute that networks more than 170 institutions and industrial organizations across the nation. The university is also home to the Institute for Advanced Materials and Manufacturing (IAMM), which includes cutting-edge characterization equipment.
“UT Knoxville and ORNL are internationally recognized for their leadership in advanced composites, materials science, and manufacturing innovation,” said Martínez Collado, who also serves as the president of UT’s chapter of the Society for the Advancement of Material and Process Engineering (SAMPE). “For me, choosing UT was choosing to learn from the best, and to work at the center of a field that is experiencing remarkable momentum and real-world impact.”
Improved Data Improves Performance
Under guidance from his PhD advisor, Department of Civil and Environmental Engineering Professor Dayakar Penumadu, and with help from University of Tennessee-ORNL Innovation Institute (UTORII) Assistant Research Professor Philip Barnett, Martínez Collado spearheaded a ground-breaking project to test the crashworthiness of fiber-reinforced polymer composites across a range of temperatures and crash speeds.
The research was jointly funded by the American Chemistry Council (ACC) and IACMI as part of their efforts to develop next-generation materials with substantially improved performance in automotive crashes and other extreme scenarios.
Since most labs specialize in only temperature or velocity testing, previous composite materials tests only focused on one of those variables—but, of course, a car needs to protect passengers in both the winter and the summer, in humid and dry environments, and in collisions at various speeds.
“Crashworthiness models are only as good as the data they are calibrated with,” Martínez Collado said. “If we want to design lightweight structures responsibly, we need data that reflects the actual conditions where safety matters.”
Martínez Collado’s team tested high-quality composite samples donated by several automotive material manufacturers, challenging them with a range of simulated crash environments using cutting-edge equipment at IACMI, IAMM, and ORNL. Instron®, a brand specializing in materials testing, independently verified the results, which were published in the industry-leading Journal of Composite Materials in September.
Industry Partnerships for Immediate Impact
Throughout the research process, the industry partners on the project shared insights into the properties that matter most for automotive crashworthiness.
“Academia is very good at asking fundamental questions and taking the time to understand why a material behaves the way it does,” said Martínez Collado. “Industry, on the other hand, is close to real manufacturing constraints and the real performance requirements that vehicles must meet. Working together on this project made our research more grounded and impactful for the future of lightweight vehicle design.”
Being able to use industry-standard materials in the research also means that the automotive sector can more quickly respond to the team’s results.
“This type of research is immediately relevant for meeting the current administration’s focus on strengthening domestic manufacturing,” Penumadu said. “Many of our students are making major impacts on US composite manufacturing and prototyping, and José’s work is a great example.”
Contact
Izzie Gall (egall4@utk.edu)