Attached is an example picture of a clamp that will be attached to a pipe made of Aluminium 6061-T4. The clamp should have very tight grip on the pipe and prevent it from slipping or rotating but the Aluminium pipe is fragile and so the clamp cannot be tightened too much. Thats why I am looking for a material for the inner surface of the clamp that will provide a firm grip on the Al pipe without requiring too much tightening force.
The clamp-pipe interface material (shown here as the black rubber-like thing) should have a very high coefficient of static friction with Al6061 in order to provive a tight grip. I want to know what materials are best suited for this purpose? Which material has the highest coefficient of static friction with Al6061?
My research so far:
The best material I could find is rubber that supposedly has a coeff of static friction of 0.8 with Aluminium. (source: http://atc.sjf.stuba.sk/files/mechanika_vms_ADAMS/Contact_Table.pdf)
Surprisingly the coeff of static friction between Aluminium-Aluminium is 1.05 !! So does it mean I should use aluminium in the inner surface of the clamp instead of rubber? sounds counter intuitive. (source: http://www.engineershandbook.com/Tables/frictioncoefficients.htm)
If I use a material like rubber or silicone, should I consider any texture on the surface? Are treads better than a smooth surface?
Edit 1: To visualize, imagine the pipe is held vertically by the clamps and a weight is attached to the bottom of the pipe, what material at the pipe-clamp interface will allow me to hang the heaviest weight?
Edit 2: The surface of the pipe is smooth to touch with matt finish, not mirror polish. Its actually anodized. Any damage to the pipe like denting or clamping marks is absolutely not acceptable. Also the pipe needs to be re-positioned occasionally, to do so, we loosen the clamp, slide the pipe to position and then tighten the clamp again