I'm glad you were able to do the stress tests. I'm a bit surprised by your results; I thought the feather would be stronger. But, I haven't done the test and you have! Your comment about "removing the feather from the quill" makes me think that maybe you didn't measure what I thought you were measuring, which may explain the low value. Do you mean that you took the vane off the rachis and shaft and measured the strength of the vane alone, detached from the rachis? (see this page for feather anatomy: http://askabiologist.asu.edu/explore/feather-biology
) When the feathers failed, did they break in the middle? Or did they break where they connected to the binder clips? I definitely agree that birds have forces on their feathers greater than 0.049N when they fly. That's part of why I want to know what, precisely, you measured and how the feather broke.
Birds feathers have little interlocking barbules and hooklets that lock together, helping the feathers stay connected and in place. It's a bit like Velcro. They also match the bird's aerodynamic profile, so the way that air passes around the feathers helps them stay together, to some extent. There are also oils and waxes in feathers that might help bind them together. In addition, different types of feathers fill different roles, so flight feathers are quite different from downy feathers.
Can you please describe the vertical shear problem in more detail? One thing to keep in mind is that the strength of materials is often anisotropic, which is a big word that just means they are stronger in one direction than in others. So, you might be able to address the problem by changing the orientation of the feather. Polyacrylate might help the feathers stay together, but I'm not certain of that. You can always test it and see if it works. You can then also test to see if you can blow air through the polyacrylate-coated feathers. That's what the engineering design process is all about. You're showing it in action right here--you built something; you tested it and it didn't work like you had planned. So, you brainstormed possible solutions. Now is the time to test those solutions. It's an iterative process, and it sounds like you are doing it well. Keep track of all your iterations and work; that's what will show your teacher and judges that you didn't just tinker with something. Instead, you applied the engineering design process to invent a material that meets specified design criteria.
Are you referring to a UV indicator card, such as this: http://www.healthedco.com/index.php/uv- ... -card.html
? If so, I think that is a neat idea for getting a qualitative sense for how effective your invention is at filtering out UV light. I like how you are thinking. Without knowing more about your invention (its size, shape, opacity, etc.) or seeing a picture of it, I'm not sure how well the card will work, but I think it's a great idea to try. Essentially, if your invention is small compared to the size of the card, then the card won't really be shielded from UV by your invention; light will just go around the invention and hit the card. And, if your invention blocks the light completely then the card won't tell you much about UV filtering specifically. But, these are based on specifics about your invention. From a theoretical point of view, I don't see any reason why the card wouldn't give you qualitative information. From a practical point of view, the card's usefulness will depend on the details of your invention. I suggest trying the card and seeing if it works with your particular invention.
Best of luck as you continue your project. I'm sure the end of October due date feels like it's coming up quickly. But, keep working on your project, step by step, and you'll get there. I'm excited to see how your project turns out! Let me know if I can help in any other way.
All the best,