 Welcome to ASU Ked Talks, the podcast. I'm your host, Pete Zaroka, and I'm here today with Regents Professor Aditi Chaddopadhyay. She is the IRA Fulton Chair Professor of Mechanical and Aerospace Engineering and the School for Engineering of Matter, Transport and Energy, one of the IRA Fulton Schools of Engineering. She's also the Director of Adaptive, Intelligent Materials and Systems Center. Thanks so much for joining me, Aditi. Thank you, Pete, for having me. So first of all, I wanted to give listeners an idea of what AIMS, Adaptive, Intelligent Materials and Systems Centers, really does. So what do you and your students study in AIMS? So the AIMS Center was established in 2006 with the goal of creating a platform for transdisciplinary problems, problems that are big enough, challenging enough that requires the intersection of different disciplines. One of the goals is to develop a unified approach to develop intelligent materials and systems for next-generation vehicles, not necessarily aerospace, but it goes across disciplines. So a lot of your work has been in aerospace though, and that's developing new types of materials that are not only responsive, but like you said, adaptive and intelligent. What exactly do you mean by that? How is a material responsive and intelligent? So the material per se is not intelligent, right? But there are molecules we can incorporate. There are nanoparticles that we can incorporate to create this intelligence. So essentially what we are doing is embedding multifunctional characteristics to the material. So if I want to make it adaptive, I will incorporate certain type of smart material so that my airplane platform can change as it encounters different type of loading, and or I can feel the vibration in an airplane or a helicopter and have means and mechanisms to reduce it or modify it to improve passenger safety. And so it all boils down to understanding the material. And I know you work on length scales. Can you explain exactly what that means? So my research theme is knowledge to safety. So what it means is unless I know enough of the material at the constituent length scale, smallest length scale, I really do not know how it's going to perform at an airplane or an automobile level. So things initiate at different length scales. And there's flaws that are there inherently in the material sometimes, can also propagate when there is an external loading. So essentially if you don't understand the initiation, you really cannot understand the evolution. And by the time you detect it at a system level, it's too late because you know that there is a damage and you have to do some repair work. So that's the goal of merging the different length scale and developing multi-scale platform. When you talk about the initiation, are you talking about a change on a molecular or fundamental level? It depends on the material. So if I'm doing something to the chemistry, I'm incorporating anything that changes the nature of my polymer. I need to understand how whatever I've incorporated, those molecules, how do they interact with the original material? So if it doesn't, or if it does, what is the strength of those bonds? So that goes down to molecular level. And so if I'm trying to understand a phenomena that is at the micro scale, I need to understand these atomistic scale interactions. But if I'm talking about maybe a composite material, I probably will start with length scales such as the fiber and the matrix constituents, the coating on the fiber, and so on, and the interface between the fiber and the matrix. So those are the length scales I'm talking about because that's where damage initiates. So it all depends upon what we are trying to achieve and what kind of material we're talking about. You spoke about a material that is adaptive, giving it adaptive qualities, and it could change. When you say change, do you mean it would adapt to a greater load? It would adapt to an extreme temperature? What kind of range of changes are you pursuing with? It can essentially, an airfoil can change the camber. So if I change the camber, that means the lifting capability changes, the drag profile changes. So that is an adaptive plan form. But it all depends upon what level you're trying to change the material. If I want to incorporate self-sensing, self-healing properties, I may be looking at just the material length scale or a specimen and a system before I get to that length scale because I want to see what I've done at the molecular level, whether there is any effect at the system level. So it may not be, in that case, it is not adaptive, but it's telling us what's going on inside the material. So maybe I can come up with a way of self-healing mechanism. Or if I know that there is a debond growing in my, you know, a dreamliner, before it comes from maintenance, if I can figure that out. So maybe it can do some predictive maintenance. So self-healing materials is, I think, something that would generate a lot of interest for a lot of people, and that would obviously have applications outside of aerospace. And that's the same for a lot of your work at Ames. It's something you stated up top, saying that you want to create a platform that can transcend just aerospace materials. Can you tell me a little bit more about, like, the wide-ranging applications of your work? So I actually got a funding from the Department of Transportation on remote sensing and the capability to give early warnings as to when the bridge needs to be closed. And I basically had very little knowledge of civil infrastructure, but they wanted some technologies because their space technology in these areas advanced a lot. So they wanted to bring in those, you know, technologies that we have developed for aerospace platforms. And it worked really well. So we came up with a way to give you a red flag, you know, for bridge closure. They wanted to be on a ThinkPad or an iPhone where people in the county can look at and see, okay, I need to close that bridge. Did you ever think you'd be working in civil infrastructure? No, no, no, no. That's a big jump. And actually the project was reviewed very well by the program manager. And he encouraged me to apply for the next three years. And I'm a hardcore materials and aerospace person. I said, no, thank you. I want to stay with my planes. Planes or automobiles or mechanical systems. And that's another thing. I mean, a huge part of fuel efficiency would be materials that something is made out of, right? And you could easily make more fuel efficient cars if they were made out of more, not only robust, but lighter materials. So that's another place that I'm sure your research would have huge impact. Yes, yes. Especially, you know, for example, high temperature materials that we are working on ceramic matrix materials. When I started working in that area, it was of interest to Air Force, right? Army for propulsion and hypersonic vehicles, right? But recently, I came across a BA from the Department of Energy, which talked about land-based turbines. And their goal is to go all the way to 3000 degree Fahrenheit. Such material don't exist ceramics. Yeah, I was going to say, what can we stay in that temperature? Yes. So we were very happy to see that, you know, we got the word. And now we're working on so a lot of things happen. There is at the high temperature, there is oxidation of the material. And the atmospheric, you know, the moisture absorption that changes the material characteristics. Now, if oxygen sips in, essentially, if oxidation degrades my material, what does it do at the constituent scale? How do I know whether my matrix is cracking or it's a fiber? And if the matrix cracks, the load has to be carried by the fiber. And so that may initiate some damage mechanism that necessarily will not happen at, let's say, 700 degrees centigrade. And these materials are very interesting. They have a length scale effects, they call it, so at moderate temperature, room temperature, intermediate temperature and high temperature. And the mechanism actually changes as we go from different temperature because the way the oxidation actually helps impedes crack propagation in the intermediate temperature range. Does it fuse it in some way? Yes. Interesting. It creates some kind of a, you know, plastic zone. So it actually retards the crack growth. So the mechanism changes tremendously. So it's very difficult to come up with a coherent model that can actually understand and bridge these different to temperature ranges, not just length scale, but these effects due to oxidation, due to moisture absorption, and so on. So that's a challenging problem. You also mentioned modeling. It's hard to come up with a model for something like this. Ames is something of a full service location in that sense, right? You guys can fabricate, you can test, and you can model materials. I started my career as a modeling person with a few computers, and we developed a lot of theories for advanced composites, and it was very difficult to essentially validate our analysis efforts. So with the funding from Department of Defense, I was able to, you know, buy different types of equipment just for validation sake. And so my modeling approach is very different. I don't start with some kind of a finite element analysis, you know, and then essentially, you know, carry on with the larger structure. I want to see the material first under confocal microscopy to see what I'm modeling, and then start modeling. And then at every length scale, I want to do experiments to see how my model hypothesis is a valid or not. So you study a material first, create a model based on your study, and then you scale up your different stresses you put on it as you understand how this material behaves. Because the constitutive laws change from length scale to length scale, and I want to make sure that I'm actually taking the right material, modeling the right material, modeling the uncertainty or variability in the material, because if I take a small piece of ceramic from one side of a panel, and then I take another piece from a different side of the panel, there is variability. And that variability essentially is not something you can inspect and see. It is at the micro level. And especially for ceramic matrix composites, depending on how they're manufactured, the pristine material comes with flaws. And so if you try to idealize that flaw, saying that there are voids 10% of it is void, it does not give you the right failure strength. Because no material is ever not going to have. It's not like you can't just say, okay, I'm going to degrade my damage mechanics based on the fact that I have 10% void. You really have to know the microstructure, where these voids are, at the between the toes of the oven composite, or is it inter-toe or intra-toe? Makes a big difference. So the modeling assumptions have to be validated experimentally to make sure we are capturing the right physics. Because we all make hypotheses when we model. Our effort is always to reduce the number of hypotheses, making it as realistic as possible. And that's the goal. But you have to prove that your hypothesis is either correct or incorrect. We're not always correct. And so we should definitely be aware of those, the limitations of the models. This might be a strange question. But do you have a favorite material? Like, is there a material that you just really enjoy working with? Composite material. Any particular composite material or just composites in general? Just composite materials. I came to the U.S. actually wanting to work on composite materials because I was doing a bachelor's thesis. Unlike here, you know, that was part of our undergraduate curriculum. You have to do a thesis. And I wanted to do some stuff that my professor said, okay, you're on your own because composite was not something we would taught at the undergraduate level. So the more I tried to create my own project, I had to dig up a lot. And that's why when I said, okay, I want to go to Georgia Tech or someplace in the U.S., I wanted to focus on where I can actually have, you know, I can grow and learn. Where are those experts? And it was a snail mail time. I was actually writing letters to professors. And asking you, hey, do you work on composites? Yeah. And what do you do? And what will I be doing? And, you know, that sort of a thing, you know, some of them were probably pretty dumb questions, but I wanted to see whether they're really interested or they have some projects that they think I can fit in. And you continue to work on composites today with the ceramics like you're speaking about earlier. So composite is a very, you know, it essentially means more than two materials, you know, constituents blended together. So we work on nanocomposites, where essentially we are introducing this multifunctionality by incorporating nanomaterials. They can be carbon nanotubes. They can be mechanophorextrous responsive materials. The carbon nanotubes can be dispersed in the polymer, or they can grow from the fibers radially. They're called fuzzy fiber. So, and there is, you know, experimental evidence from MIT that these fuzzy fiber composites actually improves what we call the interlaminar strength. Because when you bond to composites, at that bonding level, bonding layer, a lot of things happen. And so if it can improve that strength, then we have something, you know, and that is useful. And so I wanted to prove it even from a theoretical standpoint that these materials, you know, how do we know how much to put in? Is it 5%, 10%? You know, am I sacrificing some properties when I'm enhancing something else? Is it the strength of composites that interest you, or is it something beautiful about how, like, they're constructed on a nanoscale? It is actually the way that you can change the architecture. You can tailor the performance, but just at the material scale by changing the fiber directions, whether it is in plane, out of plane, whether it is a three-dimensional dough kind of structure, fabric structure, or a completely braided composite. And so this is a material where, depending on what you want to achieve, you can make the material respond to that given loading condition. Incredibly customizable. Incredibly tailored properties we can get. So it doesn't have to be the molecular scale. Just at the macro scale, by changing the orientations, changing the type of weave, you can tailor the properties based on what you're looking for, be it flutter in an airplane, vibration, or in an automobile, you know, the impact, high-velocity impact of an engine, when a fan blade breaks out, you know, that surrounding is composite, or a ballistic impact for any. So how the composite reacts, right? Those are very important things to do. And till today, we really don't understand how damage evolves in composites. A lot of work to do. A lot of work to do. So now that I know what your favorite material is, I want to back up. When do you first become interested in aerospace engineering in general? Like, was there something that inspired you to want to do this when you were young? Very early on. So I grew up in Indian Institute of Technology Campus. It became solidified my interest in aerospace. I liked airplanes when Neil Armstrong, you know, lunar landing. And I remember going to an exhibition where they had the lunar rock, 68. And that kind of reinforced my interest, you know. So when you grew up in an IIT, my father was a professor, but he was in agriculture engineering. Those are the five top institutions in Asia. So you have all these intellectuals surrounding you. Right. And I thought, okay, somebody said rocket scientist. How cool will that be? Yeah. Did you have a, did you have a favorite plane growing up? Like, was there a plane that you're particularly enamored with when you're like? Oh, I just liked Boeing because my dad and mom flew when they came for the U.S. So I like them, you know, it's just the fact that such a heavy piece of metal. And you need to understand aerodynamics. You don't need to understand these, how the structure is performed. So you need to understand, you know, how the wings vibrate. And so it's an intersection of so many disciplines. Well, it is. Engine should function well too. So propulsion comes in. Yeah. So it's a truly multidisciplinary problem. And of course, you're all about an interdisciplinary challenge. Yes. And so I was more interested in the structural part of it, the material structures. Whereas my husband does the fluid mechanics, the flow around the airfoil. So you've worked with the Air Force and NASA multiple times over the course of your career. Was there a particular project or I guess a particular airframe or plane or aircraft in general that you've worked on or contributed to that you find maybe not even beautiful, but you just think is a very cool piece of equipment. So the research that we get funded from our basic research. Okay. Okay. So they're always, you know, six zero or six one, they call it in the TRL level, the technology readiness level. So the funding comes from that. But when you're working with DoD or NASA, you always have to make sure that you know where this fundamental work is going to go into. So when I started my career, I was working with the high speed civil transport. I also worked on the V 22s, NASA's version of the V 22 vertical lift. So those are some of the things that we did were very fascinating because that was the latest and, you know, greatest things that they were talking about, like reducing the acoustics when it's flying the high speed civil transport flies over, you know, populated areas, not just modeling the wing for vibration, but the wing and the body of the airplane. And in a vertical takeoff and landing, when you're talking about V 22, you know, it flies like an airplane and it hovers like a helicopter. So those were very, very different length scale, really system level. When it boils down to it is structural dynamics and understanding the mechanics of how these things interact. And again, when I did my Murie from Air Force, the component where we had to essentially show how our models work is something that Boeing provided, because I can put all my theories and show that, okay, it works on a flat plate under certain type of loading in my lab, but does it work in a real component? So they provided me with the shape and, you know, a material that piece of structure that goes in the undercarriage of the F 16. Okay. And they had to modify it slightly because of international students working on it. Right. But that was a very beneficial to Boeing because we were applying all our basic research to something that they considered a hotspot. So. And a Murie, that's a multi university research initiative. Yes. I know an acronym. Excellent. So in your Ked talk, you shared this great story about receiving a less than warm welcome your first day of aerospace engineering. Did you encounter kind of any other resistance to your desired career path or was your family like more supportive of it than you think? My family, without my family, I wouldn't be where I am. Because they basically said gender is never an issue. It was never even discussed in my family. So my parents always said that hard work, passion, you can do anything. So they even pushed me to the point of, you know, be the best in whatever you're doing. So that was never an issue. My father always is to say that research, discovery, whatever you want to call it in every facet of life is colorblind to gender. So that's what I believe in. And my parents encouraged me all along. So I never really faced anything until the day I walked in to my department. And I was greeted with that aerospace is not for women. It was a tacit. Yes. Disapproval. That kind of level of support you see from your family, do you think you've kind of taken those values incorporated into how you run your own lab? Yes, definitely. My father was a great storyteller. And so I knew when a story is coming, there has to be a moral at the end of it. But some of them resonate still. Like he used to say, every time I brought in a report card that said, Oh, you got 100 in this and 100 in that. You tell me the story of Isaac Newton remind me, you know, how little we know. And how deep is that unknown part of the ocean? And it still resonates. I tell my students, whenever they say, you know, okay, we have solved this problem. No, just think and critic and see what we have missed. Very important lesson that also resonates is humility. Because my I believe strongly that the moment ego can really impede our journey. So you have to admit when you're wrong. And you also have to acknowledge the people around you who made it possible for you to be where you are. So I tried to essentially, you know, treat my research program and treat my students with that kind of philosophy. That knowledge is a lifelong thing. And there is no harm in admitting you're wrong. What are some ways you try and help your students excel and succeed? I interviewed a few of your students to prepare for the podcast. And they both said that I think in our lab, students end up publishing a little bit more than they might elsewhere. Is that an opportunity you really try to push your students for or? Yes, because what I tell them is, you know, I don't want my CV to grow anymore. But their career has, they need those publications. Right. And they need quality publications. Most important, when you do something exciting, you need to publish. When students come to interview me, I always or interview with me. I always tell them my expectations are everything is due yesterday. I try to kind of see whether they're really passionate about it. Because of the, you know, unless you're passionate, you can get burned out very easily. So that's what I and but the thing is, I don't know the answer to everything. So I've told them always we agree to disagree. And that's something I always tell my new students that we have to agree to disagree, because if I knew the answer, then why will DoD give me a three or a four year funding? So they get a freedom. You know, I kind of give them some guidance, they get the freedom to explore. And that's where the passion comes in. Where do you think you'd be today if you hadn't pursued engineering? It was a toss up in ninth grade in India. Believe me, in high school is when you decide your fate. Really? I can't imagine doing that. Actually, in the eighth grade final exam. So if your scores and physics and math are not high enough, you don't even enter the science. It's closed off to you. Yes. So I was also interested in writing and language was one of my very favorite topics. So there were teachers coming to my house almost volunteering and saying, Okay, heaven doesn't lie in engineering, you know, what she should be doing this aggressively recruited by the arts. So it was a toss up. And probably, you know, I still like poetry a lot. I love to read and something in that area probably interesting. I don't think that's something you usually hear from engineers. That's why I don't believe in left brain, right brain. I know you don't. I know. And again, you're a very multidisciplinary person, but a lot of engineers I've talked to, they say, Well, if it wasn't engineering, I probably have ended up in mathematics or physics or something like that. Now, my parents actually encouraged us to diversify. So we had a lot of extracurricular activities, you know, extemporal speeches, debates on different random topics, take part in it into school or into the strict essay competition, basically, you know, reinforcing writing skills, but I love to write. So that's when the interest in language came, but I owe it to my parents to make me, you know, the only thing they couldn't do is make me an athlete. My mom was an athlete and an educator, but your mom was a professor as well. No, she actually, she got her college degree when she was 18. And she has multiple, you know, degrees and stats and econ. So when they both started their career, my mom was making double my dad's salary. My dad was a professor. And for a couple of years of, you know, when I was about two or so, my mom quit. She wanted to just put all her energy in me. And so that was a decision she made. But she was also an athlete. She used to do crazy things like rope walking and like a gymnast? Yes. Wow. And she was a great badminton and tennis player. My brother and I would be on one side of the court and she would make us run back and forth and, you know, so yeah, it's interesting. We've spoken a lot about your research and your work and in your lab. But like, what are some things aside from poetry and reading you do in your spare time? Or even if that's one of the only things you do, like what are some of your memories? I like tending to my roses. I grew up, you know, my dad was passionate about your garden. Okay. And I still remember in high school, he got a new rose bush and its name was Madame Curie. And it was a yellow rose and yellow roses are very hard to grow. Are they? I didn't know that. Yes, they're very sensitive. And he told me, you're in charge. If you want to be like Madame Curie, take care of the rose bush. But I loved working with my dad. And so I tried to grow a rose here in Arizona, which is challenging. I was going to say that must be difficult. Yeah. Through garden, you read, you love poetry. Just the roses. But believe me, I don't get time to do all of these things. Do you ever have your students over to garden for you? You're giving me ideas now in their quote unquote free time. Yeah, there you go. You know, extra credit. So I know your husband is also an engineer and you said he worked in fluid dynamics, correct? So how is balancing both of your careers and life at home when you both have very demanding jobs? Yes. So when we have, we both have our PhDs from Georgia Tech and we started a career at NASA Langley. And the reason we went to NASA Langley, of course it's a dream job, but we also got it's a dual career problem. Right. But my husband knew I was passionate about this academic freedom and research. And so he actually sacrificed his NASA career and he was very happy with what he was doing. He was working on hypersonics, you know, and so on. And he moved here with me and joined the polycampus. So that was a huge sacrifice he made. And his unwavering support and he made it easy for me to balance both. So it's a son devil family. My son is also a mechanical engineer here. He started with an aerospace, decided to change so that he doesn't hear his mom and dad always tell him, oh, this is an easy course, but he's graduating with a mechanical this semester. Oh, that's wonderful. Congratulations to him and you. So without my husband's support probably would have been very, very difficult because anytime I talk to women faculty, you know, there's always a complaint that we have to do more for our spouses. But if you're asking me, my husband probably does 55%. When I was interviewing your students to prepare for this podcast, Siddharth was telling me that he really wanted to join your lab after he took a composites class by you. And he said he started working for free until in his words, you were lent it and gave him a position. Is that a somewhat common thing that happens? No, it's not because I do a lot of soul searching before I make an offer to a student. So they go through some rigorous in-house personnel committee interviews, which are my students at those talks. And I give them both sides, you know, that this is how bad your life may be, if you really don't enjoy. So they need to so go talk to other professors and then come back if you still want to work with me. But then we also get these students who come unfunded. And so they're always stopping by with resumes, you know, wanting to get support from different faculty members, which is very common. Siddharth was in my composites class and he was trying to bring a CV. My admin intercepted him, but he was very bold. He just left the CV and ran. And then he, you know, talked to my postdoc and said, can I volunteer? And my postdoc actually paid attention to his CV and he saw that he did something that was more than an undergraduate in India could do. So he said, can we hire him as an hourly? So we don't usually do that. So we hired him as an hourly and he did so good that, yeah, he's now an army research lab postdoc. Oh, has he left the lab? No, because ACU, my center is part of ARL extended. You know, we are part of the UCLA, Stanford, you know, they divided into zones. So the goal of these extended campus is to be able to hire non-citizens to work on army related material. So the fact, you know, I've been funded by army for a long time, but you know, they really, when they come here, they get to meet the students. And not everybody is a domestic majority is international. And they were very, so they've been blessed with good students, pretty much all my life, knock on wood. So they were impressed. And they said they wanted to start the ARL extended here. And the first postdoc to be hired is Siddhant. So he's located in my lab, but he works on an army related project. Interesting. He was telling me about it. Was it the electrically activated shape-memory polymeric? Yeah, which he told me about that. And I initially said, Batman, like Batman. And he was like, yeah, but yeah, kind of like that. Shape-memory materials, you know, basically the reason it's called shape-memory, you know, it retains its shape after the excitation or whatever you want to, whether it's electrical or thermal, it comes back to your original shape. Again, an insane amount of applications, all kinds of things. Yeah, adaptive morphing and so on. So one thing that you brought up during your KED talk, and I've also heard you talk about a couple of different times is how there's no demarcation in research, that everything kind of bleeds together at least a little bit. Can you tell me a little about how you kind of came to that philosophy and how you practice that in your work? So traditionally, we researchers tend to focus on our little disciplines where we have been trained and have the expertise. And anything that is outside my expertise is either not important enough or, you know, less important. And I don't believe in that. And especially being an aerospace engineer, although I work with the structures and materials, these structures and materials, the airplane wing and the fuselage, the way they deform depend upon how the fluid flows. So that is why I don't believe, you know, that you can only keep doing what you're doing, because everything lies at the intersection of these transdisciplinary boundaries. You have to be able to, even if I'm not an expert in that area, I need to be able to understand or bring in an expertise so that, you know, whatever I'm developing becomes more realistic. You've also said that sometimes people are territorial about their disciplines as well. And it's sometimes hard to get people to collaborate because someone over here does not want the nosy aerospace engineer pushing into their field. How is that something you've dealt with over the course of your career? I'll give you an example of the MURI I got. So I was being funded by FOSR on smart composite structures at that point. And I called up the program manager when I saw the MURI announcement and the MURI announcement was on metals. But the theme was understanding defects in metals and developing techniques to quantify, classify these defects and establish what is the residual useful life of these materials. So when I called him up, he told me, you realize you're not a metals person. I told him I'm going to study metals before I write my proposal. I learned a lot. So it was outside my comfort range, but I got interested in metals also. So, you know, later on I worked on super alloys like titanium and so on. So definitely, you know, there are things that are outside our comfort zone, but in knowledge to safety, every material has some kind of a flaw inside or something happens inside it and that crack grows. So the underlying theme is you really cannot ensure safety unless you know what's going on at the material length scale. So that's very multidisciplinary in nature and it keeps us busy because we're always reading papers and learning new things. And the territorial part is you cannot really blame this because we're all going for funding and that's our survival. So, you know, it's just part of this, you know, our system is. Thank you for your time today, professor. I really enjoyed talking to you. I hope everyone at home learned something and enjoyed listening. Thank you Pete for listening to me. It has not been a solo journey. I've had a lot of people, a lot of mentors and I still learn from my students. Thank you. If you're interested in more from Aditi Chattopadhyay, watch the ASU Ked Talks video at research.asu.edu slash Ked Talks. Subscribe to our podcast through your favorite podcast directory and find us on Facebook and Twitter at ASU research.