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Oct 21, 2021Liked by Surjan Singh

I think you might be off on your apples-to-apples comparison. If you go past the yield point, and into permanent deformation, your Kevlar net will start to get saggy/'dent', and not be able to absorb as much energy next time. This isn't to say that it's not a good idea, just that I have problems with that specific argument.

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You're probably right. That's something I'm not 100% sure about when it comes to fibers in a non-composite application. (This is my first time trying to build something with them). I was going off of the stress-strain curves like this one: https://www.researchgate.net/profile/Serge-Rebouillat/publication/271436330/figure/fig1/AS:362116772057095@1463346774625/Typical-stress-strain-curves-of-a-KEVLARR-fibres-and-b-other-commercially.png

It shows no distinct yield point like the metallic stress-strain curves. But in my latest round of testing, I have had some permanent stretching. A different mechanism than yielding I guess.

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Oct 27, 2021Liked by Surjan Singh

I'm not sure what kind of equipment you have available, typically loading/deloading throughout the test will give you additional information when you don't have a clear yield point. I wouldn't be surprised to see some stress rate dependent behaviour, which is even harder to test! An example of the load/deload: https://www.texpedi.com/2020/10/tensile-loading-elastic-and-plastic-deformation.html

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Thanks for the link. I have absolutely zero testing equipment haha. My approach has been to test the structure as a unit and tackle the most glaring issue as it arises. This looks like it's the next one. So much to learn about textiles (and materials in general). Did find this paper that I'm hoping might be useful for me: https://ascelibrary.org/doi/full/10.1061/%28ASCE%29MT.1943-5533.0000156 . Though I guess the solution to these problems is probably just to use more material, so I'm not sure how in depth I actually need to get.

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