Theory Meets Practice: Philippe Geubelle
Philippe Geubelle marvels at the “beautiful experiments” that his colleagues conduct. As a professor of aerospace engineering and a member of the Autonomous Materials Systems (AMS) Group within the Molecular and Electronic Nanostructures research theme, he theorizes and creates computational models, while others perform the experiments that test his theories and validate his models and optimal designs.
“Direct collaboration with experimentalists has always been part of my research,” Geubelle said. “It always adds so much to my work to collaborate with talented scientists who have so much insight and can help us validate the numerical results.”
Some of those experimentalists include colleagues in AMS: Nancy Sottos, a professor of materials science and engineering; Scott White, a professor of aerospace engineering; and Jeff Moore, a professor of chemistry. Geubelle has been working with them on self-healing and other multifunctional materials for more than two decades.
Their groundbreaking work focuses on creating new materials that can repair themselves when damaged. It’s work that has implications for how composite materials are made, how long they last, and what happens when they are at the end of their useful lives.
“Scott, Nancy, and I started the discussion early on and did a very simple feasibility study on the concept of self-healing materials,” Geubelle said. “At the time, we thought the best approach was to use microcapsules that would be embedded in the material. We realized very quickly that to explore this further we would need a top-notch chemist and a multidisciplinary approach. That’s when Jeff joined the team. It was also decided that the Beckman Institute was the ideal place to conduct this type of multidisciplinary research.”
Geubelle said his role in the self-healing collaboration was “to try to understand how we could achieve an extension of the fatigue life of these materials. Could we actually predict how much longer the structure would survive thanks to this self-healing capability? Could we understand how a crack interacts with one of these microcapsules, whether it is attracted by it or not?”
Essentially, Geubelle was working to understand how the microstructure of a material affected its performance.
As the project progressed to other forms of autonomous materials systems, the question became: “Once we understand how the microstructure affects the properties of the material, can we optimize the responsible material by designing the microstructure?”
This emphasis on computational design of materials was motivated by advances made in AMS in the manufacturing of composite materials with complex microvascular systems, basically a system of embedded microchannels, similar to the veins and arteries you find in living systems.
“My role is to come up with numerical methods that allow us to see the impact on the response of these microvascular composites, mostly for active cooling,” Geubelle said. “Once we have formulated, implemented, and validated the numerical methods that allow us to quantify the impact of these microchannels on the thermal response of the microvascular materials, we can optimize the configuration of the embedded microchannel network using gradient-based optimization techniques.”
One aspect of this materials design work that is particularly satisfying, Geubelle said, is the opportunity to see tangible results of the theoretical and computational work that he does.
“The reason I so enjoy and appreciate working in this collaborative environment is that my colleagues have a unique ability to be able to manufacture what I come up with,” Geubelle said. “Whatever I design, these experimentalists can actually make. Their work actually closes the loop because the material system or composite system they make shows experimentally that what we design is indeed better than what we started from.”
Geubelle believes that the multidisciplinary research focus at Beckman is especially valuable because of the engagement it affords faculty and students.
“The strength of the environment is how it allows chemists to learn from scientists and engineers working in mechanics and materials science and vice versa,” Geubelle said. “If you put students with different expertise together, they will influence each other in a way that brings great benefit to each of them and to their fields, which is a great success story for the Beckman Institute. This multidisciplinary environment greatly enhances the education of our students.”
He believes the same is true for faculty. “I remember when we started the collaboration on self-healing materials, we had biweekly meetings. When the chemists would talk, we didn’t understand a word, and I’m sure they felt the same way. Eventually, you hear them explain their science and you come to learn and gain from that.”
That lesson on collaboration continues to inform Geubelle’s work.
“I rarely write single-PI proposals because I strongly believe that it’s critical to work with experimentalists to get some insight as to what kind of model you should use and then to check how good your model is,” he said. “Without the talented scientists at Beckman and across campus, the theoretical and computational work I do would be an intellectual exercise without much application. I know to leave the experiments to the professionals.”