Minimizing the Impact of Aeroelascitiy on Airplanes
Advisor: Kavita Sharma
Aeroelastic instability in aircraft, which could include flexing and structural divergence in wings or fuselage, poses a serious risk to flight safety and performance. My project will investigate how material selection can influence aeroelastic behavior under aerodynamic loading. I will conduct experiments using controlled wind tunnel testing and simulations to compare materials based on their stiffness-to-weight ratio, damping capacity, and deformation response. Identifying materials that retain structural integrity while minimizing deformation could allow for safer, more efficient aircraft.
Project Blog
Post 1: Blog 1 -- Aeroelasticity
Every time an aircraft pushes through the air at high speeds, the wings don’t just carry the plane; they have to flex and twist in response to the aerodynamic forces acting on them. In extreme cases this can cause catastrophic instability. This flexing and twisting phenomenon is called aeroelasticity.
My goal isn’t to design materials that just resist the forces, but rather that are smart enough to work with them. I ask a simple question: how can we optimize aircraft materials while accounting for the aeroelastic effects experienced during flight? The traditional fixes include adding reinforcements and thickening structures, and they work. But they also add weight, burn more fuel, and raise costs. I want to explore which material types work the best for their price while making sure we don’t increase overall weight and cost.
I’m currently in the DC area, meaning I will have access to online academic journals, engineering databases, and the national library. I can commute there myself, which makes me able to conduct regular research practically. I will combine my research with small-scale simulations with wind tunnels to model how different materials behave under real loading conditions.
My end goal is to produce a research paper that can inform real aerospace design decisions. Benefits can include lower emissions, reduced operation costs, and more sustainable air travel overall.
Post 2: Blog 2 - The Library
I made my first research trip to the national library this week. I had a general sense of what I was looking for, like composite materials, aeroelastic behavior, and structural optimization, before going to the library, but actually sitting down with the books really helped me see everything clearer.
The biggest thing I learned from this experience was how carbon fiber composites handle stress differently depending on the direction of the fibers. Other materials, like metal, resist force the same way, no matter the orientation, and show a stark difference from this. This would allow wings to be designed so they can resist force from one direction but twist if forces act on them from another direction. This could prove really useful for managing aeroelastic effects.
While I might not be able to work with carbon fiber, which is not only expensive but also hard to work on on a small scale, this could impact my work with other materials, such as fiberglass, which is both accessible and reasonably priced. This would let me use a realistic depiction of this concept with my limited resources, which can be applied to broader aeroelastic research.
Post 3: Blog 3 -- Aeroelastcity
This week I started working on the design of the wings I will be using. I looked into how I can make the small scale wings using the accessible materials which were, balsa wood, fiberglass, and fabric. Sincethese 3 materials are realistic to use and have similar effects under aeroelastic forces comparatively to carbon fiber.
I will create 3 wings and make sure to keep the chord length, span, airfoil profile, and mounting method constant. The first wing will have the spar straight, therefore it will act as baseline. The second wing will have the spar angled twisted down under load which means it will show wash-out coupling which will delay divergence. The third method will promote wash-in coupling by having the nose up, which could cause the instability to start earlier. I am doing this to control bending and twisting, which is the core mechanics behind aeroelastic tailoring which is used in real life wings.
I’ll also be measuring the tip deflection in millimeters at all of the increments for the airspeed and then recording the flutter onset and divergence for each wing. I can then compare these to simplified theoretical predictions to see how well these lower cost material setups will match commonly used theory.
Post 4: Blog 4 -- Materials
I have started to order the materials I need for my project. The materials I've gotten were balsa wood sheets, craft fiberglass cloth, a foam board, epoxy resin, and wood glue. All the materials that I've gathered for now are inexpensive, helping me make sure that my project will allow meaningful testing without high expenses.
Now that I've ordered all the materials, I need to think more about how I will actually build the wings. To make sure these 3 different materials can produce 3 wings that are almost geometrically identical will definitely prove to be a challenge. Even small errors, like in chord length or rib spacing between the models, can make the results meaningless. Before I start actually cutting, I want to make templates that I can easily replicate in all 3 wings.
The spar is the most important part of the build for me to get right. It needs to change throughout the builds, first running straight, then running down, then running up. Making sure I get these angles consistent throughout all 3 of my build designs is absolutely vital. Meaning I need to do a lot of measuring, as just a couple of angles not visible to us can mess up the experiment terribly.
I will start by building the ribs of the airplane. This will stay constant for all 3 designs for all 3 materials, meaning I need to create it 9 times. This will act like a skeleton to the airplane, giving it the structure it needs. Next will be the spar; it will act like a spine. This is where the differences between the 3 wings emerge. The spar goes through the rig and is angled based on the wing design I need. This acts like a backbone and will support the weight of the wing. Lastly, the skin will be added. This skin is what closes the closes the wings and give it the aerodynamic surface. These 3 components are all you need to design a simple wing design.
Post 5: Blog 5 -- Aeroelasticity
Now that I know what to build, I need to focus on how I can test all the wings. I will make sure that all nine wings, including all three materials with the three spar orientations each, will go through the same procedures so that the results will be easily comparable.
Every single wing will be mounted at the root end in the wind tunnel; they will be fixed in place so that the only movement that will be able to occur is the wing responding to the airflow, showing the aeroelasticity of the wing. I will then incrementally increase the tunnel's airspeed, stepping up gradually, not just going to high speeds. At each increment I will measure the tip deflection, which is how much the free end of the wing bends in millimeters. This will give me a deflection and airspeed curve for each wing, which is easily comparable throughout the models.
The second measurement is flutter onset, which is the exact point where the wing stops deflecting steadily and starts uncontrollably oscillating. This is not possible to capture in the moment due to human error, so I plan on recording every run so I can look through the video footage to identify the point where the oscillation begins as precisely as possible.
Once all the data is collected, I’ll compare everything across the orientations and materials and see whether the predictions from established theory will match the results. I will also repeat runs to ensure reliability.
Post 6: Blog 6 -- More on Aeroelasticity
I have ordered all materials needed to start testing my wings. I also have been reading more on the theory behind my testing.
Something that keeps coming up is flutter, the vibration of the wings. It sounds simple, but it goes a little deeper. Since it's a self-sustaining oscillation where aerodynamic forces and the structural dynamics of the wing start to complement each other. It doesn’t just stop on its own; it progressively gets worse. This is the problem that destroyed many early aircraft before there was even a name for it. The reason why spar orientation is important is that it controls how the bending and twisting interact. A wing that only bends upwards while twisting nose-down under load, which is washout coupling, reduces the aerodynamic forces acting upon it, which can help slow down flutter. A wing that has a twist nose up would have more instability.
I’ve also been researching how to build the air tunnels. I could buy one, but that’s expensive; I’d rather spend $50-80 building one that works the same way. All I really need is to be able to produce consistent airflow speeds and also have a window or something so I can film the wing. The only real expensive part is the fan itself.
Post 7: Blog 7 -- Beginning to Build
I now have all the materials needed to build, including balsa wood, foam sheets, fiberglass cloth, and additional support materials like epoxy resin and super glue. I finally started experimenting with the designs to make them easily replicable to minimize the margin of error. To make sure that all 9 wings will have the same template, I used sharpies to trace outlines using a paper model. I haven’t cut anything, but the rib templates have been installed into all the wings. Looking into the design, balsa wings will be the most straightforward due to their stiffness, while fiberglass and foam parts will be a bit harder. Therefore, before I start the mechanical work, I'll watch and read tutorials on how to properly handle these materials. I’ve also learned more about how a wind tunnel works after seeing how a real one works at UMD. This has given me a better idea on how aeroelasticity testing really works and will allow me to perfect my form on real testing, whether it be at home or anywhere else.