This week, we take you across the Atlantic to the American Midwest for a fascinating meeting with Philippe Geubelle, Professor of Aerospace Engineering at the University of Illinois at Urbana-Champaign. We are 200 kilometers south of Chicago…
Originally from Belgium, Philippe Geubelle studied at UCLouvain. With his degree in Mechanical Civil Engineering in hand, he went to the United States to get a master’s degree and a Ph.D. « I always knew I wanted to work in academia. I went to the United States to get a master’s degree and a Ph.D. in aeronautics at Caltech (California Institute of Technology). I was then a postdoctoral research associate at Harvard and joined the University of Illinois at Urbana-Champaign in January 1995. So I’ve been here for over 28 years!”
Geubelle Research Group: the research engine of the Aerospace Engineering Department
In charge of his own research group, Philippe Geubelle heads up around ten researchers (undergraduate students, PhDs and postdocs). « Our research activities are mainly linked to the activities of the Autonomous Materials Systems group at the Beckman Institute for Advanced Science & Technology. The Beckman Institute is, in a way, an entity that brings together research centers working on different subjects; it’s an ideal place for students, postdocs and professors to work together and exchange ideas. We have around ten professors and forty students and postdocs. Lately, we’ve been working a lot with our colleagues in chemistry and materials science. This interdisciplinary approach is proving very effective!”
Do you work directly for aerospace companies?
« We sometimes do, but the majority of research programs are funded by federal agencies such as the National Science Foundation (NSF), US Air Force Office of Scientific Research, NASA, Defense Advanced Research Projects Agency (DARPA), US Department of Energy, … »
Can you tell us about some of your past or current research projects?
« We have been working (for some time now) on the development of self-healing materials, i.e. materials that have the ability to repair themselves automatically after sustaining damage; these are not just polymer materials, but also composites. The idea is to have materials that can automatically detect the presence of cracks. When cracks appear, microcapsules rupture and release self-healing agent that slows down or even stops the progression of the crack.
Following this project, in close collaboration with collaborators in aeronautics, materials science and chemistry, we developed materials with a circulatory system. In addition to their self-healing properties, these materials have an active cooling system thanks to a network of veins and arteries through which we pass a cooling system.
A third project we are currently working on concerns composite material production methods. Today, to manufacture a composite aircraft wing, you must prepare the material, place it in an autoclave and leave it for several hours at high temperatures of about 160 to 180 degrees Celsius. This manufacturing process is both time-consuming and energy intensive. To speed up the manufacturing process and drastically reduce energy consumption, we have developed a new approach based on the frontal polymerization of the resin by injecting a small amount of heat to initiate the polymerization, which is then propagated by the exothermic properties of the chemical transformation. We have demonstrated that it is now possible to produce high-quality composite materials outside an autoclave, using 6 to 7 orders of magnitude less energy than conventional processes and using minutes instead of hours. We have also shown that the frontal polymerization technique is also applicable to additive manufacturing (3D printing), enabling complex structures to be printed rapidly without the need for the post-processing stage required in conventional processes.
More recently, we have started a new research project funded by the Department of Energy, the aim of which is to develop a new generation of thermoset materials that are both compatible with frontal polymerization and are recyclable. The aim of this project, which, in addition to our university, involves researchers from several other American institutions (MIT, Harvard, Stanford, U. Utah, and Sandia National Lab) is to develop polymer materials that would have mechanical properties similar to those of thermosets and would be recyclable like thermoplastics.
DARPA (Defense Advanced Research Projects Agency) is also funding us to study the possibility of using frontal polymerization to build large structures in space. This would avoid the need to transport and deploy components (prefabricated on earth) on board space vehicles and allow these large structures to be built directly in space. It’s a magnificent project that we’ll be demonstrating first on earth… before sending it into space (he smiles).
As we have seen, making materials lighter, improving production performance, etc. are at the heart of our developments, but there is another aspect that is keeping us very busy, and that is of course the recycling of all these materials, which has become a major issue! When you look at the landfill sites where wind turbines must be disposed of, it’s vital to develop materials that deliver the expected performance but are also recyclable. That’s what we’re working on!”
What have been the highlights of your career?
“The development of self-healing materials was a highlight of our research activities. This project had an international impact; different research groups started working on this material, international conferences were organized, etc. This technology has also been adopted by the paint industry to extend the life of products, for example.
The manufacture of composite materials based on frontal polymerization had also a major impact and has attracted the interest of several research groups in the United States and elsewhere. We are collaborating with several groups in the USA and Europe.”
What relationships do you have with research centers in Europe?
« For example, we have relationships with the Department of Chemistry of ULB (Belgium), where one of my colleagues, Professor Rongy, works. I have also worked with the EPFL (Switzerland) on fracture mechanics, a subject of great interest to me. Within my group, we have received students from EPFL doing a master’s or thesis work. We also have a relationship with a group in France that develops catalysts.”
What is your perception of the research sector in Europe?
« There are some excellent research centers and the EU’s financial support system seems to be effective. The link between research and industry is certainly an interesting approach. While there is also an emphasis on interaction between academic research and industrial applications here in the US, there are also here a lot of sources of funding for fundamental research.
What sets the USA apart is the number of research funds available and the fact that you can work within organizations like the Beckman Institute for Advanced Science & Technology, a university unit dedicated exclusively to interdisciplinary research. This environment appeals to students because their training goes beyond traditional education; we have chemistry students who understand mechanics and vice versa. We’ve brought our research groups together in the same environment, and that’s unique!”
Do you plan to return to Belgium one day?
« I don’t think so,” (he smiles), “even though most of my family is in Belgium. My wife is American, our children are American and I will have spent my entire career at the University of Illinois! It would be difficult for me to embark on a new career in Belgium.”
To get in touch or find out more about the Geubelle Research Group: https://geubelle.aerospace.illinois.edu
Images & logo ©Philippe Geubelle & University of Illinois.