I am trying to understand how Aramid works as a reinforcing fabric, especially for composite tubes.
What I want to know : should the Young's modulus of aramid be lower BEFORE weaving the aramid into patterns as shown below? And does the Young's modulus increase AFTER it is woven onto the tube?
Is it theoretically true that unstrained aramid has a MUCH lower E than that of strained? (See graph below in order to get my drift)
Dear Jonah,
E of the fiber should be greater along the axis. E can not increase with strain for fibers.
How are you getting stress-strain curve? It may happen that for initial strain, only few fibers may be taking the load. And after certain strain, remaining fibers may also take the load.
Regards,
Chandrashekhar
this usually happens when some fibers start taking load after some strain.
Dear Jonah,
first of all, the aramid fiber keeps its Young's modulus no matter if it is a single fiber or woven as a mesh. The difference that you observe between a single fiber and a woven mesh is due to the different load states of the fibers. Depending on how you apply the mechanical load on the woven structure the fibers will experience tensile or shear load. If you apply the load e.g. along the long tube axis, all the fibers that are aoriented in the same direction will experience tensile stress. This is nicely described e.g. here:
https://www.tf.uni-kiel.de/matwis/amat/mw1_ge/kap_7/backbone/r7_1_4.html
Best regards,
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