Kevlar safety equipment

[GrandpaRacer]

OK, I tried Delrin backing under the Kevlar and re-sharpened the turn fin. It was sharp enough to cut my fingers. The result is amazing, the aluminum just rolled up and the Kevlar is uncut and the Delrin is hardly blemished. Kevlar is really strong. I am sure a slicing motion may be more effective but I am not sure how to do that in a test set up.

[Charlie Pater]

Is that fin made out of Al? Some people are using steel or other material. May not have the same effect. I have seen fins made out of Carbon fiber. So many variables. I think you are heading in the right direction with the testing.

[GrandpaRacer]

Yes, aluminum. It was a J turn fin so if could be a softer version. I will make a test one with 6061 or even harder if I have a sample. Probably should try steel also.

[ricochet112]

I didn't think just pressure would show much.

How about making some kind of cantilever, guillotine or switchblade device. It would have to impact at at least 45 mph to have any valuable data.

Or, take a pant sleeve, fill it foam and run over it?

[racing18z]

Is wet Kevlar easier to cut than dry Kevlar? Or does Kevlar retain all of its properties and it is the same force to cut wet/dry?

[GrandpaRacer]

Kevlar absorbs moisture, so you have a good question.

[mathrich]

Kevlar does not have full strength while wet. 3-13% less when wet according to this article https://arc.aiaa.org/doi/abs/10.2514...journalCode=ja

[GrandpaRacer]

I found some good info on cut resistant testing here https://www.hexarmor.com/posts/the-t...ut-cut-testing There are two techniques: static like I am doing and dynamic with a spinning wheel. We want to know if a blunt edge gives more protection so I think our static test is ok. One interesting point the US cut level 5 is better (stronger) than the European cut level 5.

[GrandpaRacer]

The EU standard is now A through F. F is about the same as the new US A6 . The old US level 5 is half way between the new A6 and A7 cut level.

[GrandpaRacer]

Here is the new ASTM ratings set in 2016. The standard test is a sliding razor blade.The new A6 or A7 is about the same as the old cut level 5.
file:///C:/Users/johnr/Desktop/Cutting%20Kevlar/ASTM%20F2992-15%20Cut%20Resistant%20Standard.pdf

[GrandpaRacer]

This is probably my last test because I can not cut this Kevlar sleeve with aluminum under direct pressure. This time I sharpened some strong fin material, 7075 AL to a 0.001 edge. I switched to a harder wood backing, Birch I think. Again I could drive the al into the wood and Kevlar. eventually the al gave and rolled as you can see. The Kevlar remained undamaged. The original goal was to see if making the turn fin blunter we could get better cut protection. That seems logical but since I can not cut this Kevlar sample in any of my tests, I conclude from these tests that there is no predictable advantage to having a blunter edge. In fact I conclude with direct static force AL is too soft to cut Kevlar.

[Solesen]

Thank you for doing all the testing, it’s helpful information. Not sure why ours cut or if skid or prop. We are planning to double up our Kevlar and make sure seams have Kevlar coverage. Also planning to experiment with Lee’s idea for ballistic plates in pockets on the pants. Thanks again for the research...we appreciate your efforts.