Which materials have a high static COF on carbon strands?

[utsengr]

I'm trying to find a material for tensile test grip inserts for testing small diameter (~0.063" and ~.031") carbon fiber strands without using tabs. I need a high COF material that won't bite too hard into the specimen and cause failure in the grips, but will also withstand the specimen's tensile strength of about 515 lbf and 385 lbf respectively.

Please let me know your thoughts on such a material.

Thanks!

 

[Compositepro]

You cannot clamp onto dry carbon fibers with enough force to test them without damaging the fiber. That is why fibers are impregnated.

If you actually mean carbon fiber composite strands you still have the same issue but not to the same degree. Your grip must conform to the test specimen and then be very strong for the test.The only practical way to do this is adhesive bonding. The liquid adhesive conforms precisely to the specimen, and after it is cured it is very hard and strong enough to transfer the required loads. Tabs are only the interface between the specimen and mechanical grips so you don't have to bond the specimen to your test machine.

 

[utsengr]

The goal is to speed up the overall tensile testing process, including any cure time and other specimen prep time involved.

I am in the process of determining the fiber's transverse compressive strength, which will provide more information on how large the grip inserts will need to be to spread the normal force in frictional contact.

 

[utsengr]

The carbon strands will hold up to a squeezing (Normal) force of 658 lbf (for .044" diameter strand) and 785.6 lbf (for 0.030" diameter strand). This means that I need a material with a static COF of at least 0.74 on carbon fiber and will withstand a shear stress of at least 3150 psi.

Please let me know your thoughts!