While sanding the excess resin with micro from the rivet heads you have to be careful to not remove any aluminium from the rivet.
Removing just a tiny bit is done easily, I measured on a test rivet about 0.1/0.2 mm.
This doesn’t seem to be much but will it impact the strength of the rivet?
For educational purposes I did some shear and tensile tests with the 3.2 and 4.0 mm rivets.
With a digital kranescale of 300 kg I created this setup for the shear test:
I tested both rivets sizes and with different head thicknesses until the rivets failed.
All rivets failed at the same location, just between the 2 aluminium strips:
These are all the results of the shear test:
Conclusion for the shear test: all rivets failed slightly above the shear values published by Gesipa and the rivethead height does not impact the shear strength of the rivet.
For the tension test I used an equal setup, but instead of 2 strips I used 2 U pieces:
The rivet is positioned between 2 U pieces of aluminium:
Just before the rivet fails, it’s visible that the head gets pulled inwards and after failure the head looks like a tinnerman washer:
For the tension test I used 4 samples for each test, here the results:
Conclusion for the tension test: all rivets failed slightly above the tensile values published by Gesipa. A height reduction of 0.1/0.2 mm does not impact the strength of the rivet. However when removing 0.2 mm or more it does impact the strength.
Just for fun I tested a solid rivet as well, this AN470-AD-4-4 did not fail, at 173 kg it was pulled out of the U pieces:
Quite strong these solid rivets…