Thank to Dan for sending me the Kevlar belts, I was able to get this done and analyzed.
Equipment
I used that same equipment as before. See my previous post above.
Procedure
I loaded the belt into the grips of the machine, ensuring 150mm of distance between the grips. I then loaded the belts with varying amounts of force from 5-40lbs.
Results
The Kevlar belts are potentially not as resistant to stretch as the steel belts but they are very close. I can’t say for certain that they are anything less than slightly stretchier than the steel because the statistical differences are small.
For comparison:
To put this in perspective, this is a difference of 2.45mm of stretch in the steel-cored belts and 2.65mm of stretch in the Kevlar-cored belts at 38 lbs-f. Realistically, we mill materials like wood and aluminum with radial forces closer to 10 lbs-f (@gmack can chime in here), the difference between the two are about 0.15mm of stretch with a 500m belt.
The charts and trendlines I used are below. I changed the graph from the prior one because I realized the data at 5 lbs is noisy due to the machine reaching it so quickly versus the higher loadings. I also forced the linear regressions’ intercepts at zero since at zero stress, there should be zero strain.
