Let's talk Kevlar or Dyneema!

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Michael

Michael

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Mar 25, 2015
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I've had this idea floating around in my head for a while, but I have zero experience with ballistic fabrics. The primary goal is to make a silent backstop that will stop a pellet generating up to about 80 FPE. 

This crude drawing depicts what I have in mind. A 4x4 wooden frame with a sheet of Kevlar/Dyneema loosely bolted to it. I say loosely because I'm using the concept of catching an egg in a piece of fabric. Cradling the pellet as it impacts the fabric. 



So here are a few questions about these materials:
  1. Will a single sheet of Kevlar/Dyneema stop a pellet? If not how do I "bond" multiple sheets together (as done for personal body armor)?
  2. Am I on the right path thinking the material can be loose? Or does it need to be taught?
  3. ​If I make the material taught will the pellet bounce back?
  4. Will it require some type of backing? If so what type of material would keep it silent?
  5. Can I drill thru Kevlar/Dyneema? If not how do I make a hole in it?
  6. Which is stronger 3000 denier, 1500 denier, or 1000 denier?
  7. Would a resin coated Kevlar work better than strictly Kevlar? 
  8. Does anyone have experience with Dyneema HB26? Which apparently is 40% stronger than Kevlar?
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    Any and all experience with either of these materials would be helpful.

    Let's make a stronger, lighter, quieter backstop.

    Thanks

 
One big drawback to Kevlar is its lack of UV resistance. Dyneema is far more UV resistant. I will look for some samples of various materials.

http://www.fibreglast.com/product/Kevlar_and_Hybrid_Sample_Pack_4004/sample-packs

I am thinking a sandwich of several layers of Dyneema / Kevlar with Dyneema as the outer covering due to its increased UV resistance. It will certainly need to be loose as taught would create a pellet trampoline which could be detrimental to ones eyes / or eye as the case may be.

I like this idea because I have been shooting holes in my 14 gauge pellet trap back wall with my continuous .25 caliber pounding.

Thurmond

 
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I'm interested to see what comes up in response to your topic. I just started a similar project. I looked into kevlar fabric but found some ballistic nylon that was much cheaper. Same stuff they make suitcases out of. I ordered a couple yards of it, and it just arrived yesterday.

My plan is to make a frame out of PVC pipe and hang it like a shower curtain. That should provide plenty of give to dissipate energy. No idea if the nylon will hold up but it wasn't very expensive . I'm only going to use it to catch strays if someone has really bad aim. I'll have a pellet trap of some sort in front. I think it will work as it won't get repeated hits in the same spot, but time will tell. Worst case I double or triple up, or buy some kevlar. I should have it together in a week or so and will post up how it holds up
 
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I have experience with Kevlar and other other composite reinforcement fabrics and I have made some backstops with them.

First off, I recommend watching some YouTube videos showing the basic process for making composite parts. There is zero chance that a loose piece of Kevlar fabric will stop a pellet.

The strength in composites comes from the layers. You wet out the fabric with epoxy resin and add multiple layers in different directions which you then compress for the curing process. Once cured, it will be hard so it won't be silent on it's own although it probably won't be as noisy as steel.

Kevlar vests are designed to stop bullets but not repeatedly. I.e. If you keep shooting the same spot, you will eventually cut through it. So understand that it will have a limited lifespan.

I would avoid putting it in a frame of wood or anything else. The wood will crack and / or you shoot the Kevlar right out of it.

I don't know how many layers you will need for something that powerful. I used 7 layers for my 25 cal and added additional layers of fiberglass because it flexes better. You will need to experiment with your gun and the resin you choose (there are tons of resins with different properties) but you will need a lot of layers.

I am not familiar with Dyneema but not all strength is equal with composites. Carbon fiber is the strongest overall but Kevlar is better for stopping the cutting motion of projections. It's a pain to cut that's for sure (buy good scissors). I would find out if the other material has the same type of strength as Kevlar. If not then I wouldn't bother with it for this. 

I compress the composite fabrics between two pieces of plexiglass with weights on top for curing flat panels. I use two sheets of release liner film to stop the fabric sticking to the plexiglass.
 
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@Zebra - I've seen your Carbon Fiber stock building prowess. I myself have quite a bit of experience making surfboards from fiberglass/carbon fiber/epoxy resins. I don't want to make a composite based backstop, because as you pointed out it will have a limited life span.

I'm more interested in seeing if Kevlar/Dyneema will stop the pellet if it is caught in a fashion where the pellet is tumbled into a loose fabric. Kind of like a steel trap where 45 degree angles are utilized to reduce the amount of energy.

 
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I like the idea of the "catching an egg in a piece of fabric" idea, but suggest a hybrid design. I think if you used a cushion of duct seal behind the Dyneema/Kevlar, perhaps with a thin metal plate behind that, you'd have the perfect back stop with a very long life for high energy pellets. The Dyneema or Kevlar would flex with the initial hit, passing energy into the duct seal. Metal plate needed only for safety. After shooting a bunch of rounds, the Dyneema/Kevlar should hopefully be intact, and the duct seal could be squished back into shape, after which you start over with a 'new' back stop. Having a Dyneema/Kevlar front surface would solve the problem of tunneling through the duct seal that occurs when pellets strike the same place repeatedly, and with the Dyneema/Kevlar front surface the pellets should fall into the collecting trough at the base, without having to be dug out from the duct seal goop. Do you think this would work?
 
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"Michael"@Zebra - I've seen your Carbon Fiber stock building prowess. I myself have quite a bit of experience making surfboards from fiberglass/carbon fiber/epoxy resins. I don't want to make a composite based backstop, because as you pointed out it will have a limited life span.

I'm more interested in seeing if Kevlar/Dyneema will stop the pellet if it is caught in a fashion where the pellet is tumbled into a loose fabric. Kind of like a steel trap where 45 degree angles are utilized to reduce the amount of energy.

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The raw Kevlar fabric I have used has been a bunch of loose threads that you could pull apart by hand before it's cured with resin. Unless you have a type I haven't seen that is cured into a flexible fabric, I can't see how it would stop a pellet. 

The only materials I have seen that can withstand constant repeated impact are the hardened steel panels they use at the range. 

Kevlar fabric looks and handles like carbon fiber before it's cured. It's a different color, harder to cut and takes more resin to wet out but if you've used carbon fiber then you know what I mean.

maybe you could try a semi rigid / semi flexible impact resistant resin with Kevlar to achieve your goal. I know of a few like that. I'd still want many layers for a powerful airgun though. 
 
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Michael

I build a backstop out of salt treated 2 x 10 lumber which I was starting to shoot through. When I noticed the center going on that arrangement I looked around for something I could put on the backstop to reinforce that area. My eyes fell upon an old vest that I had been issued back in the early 90's. I thought, "Am I ever going to need that again?" Well, the answer was no. So I took that vest and cut the sides and just screwed the thing to that backstop. I've completely shot the middle out of that lumber backstop since and the kevlar shows no sign of ever failing. It will work and it will work well. It does make a loud pop when hit though.
 
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If you made a rubber back stop from the Tractor supply store at a 45 degree angle you would still need a 2x12 hard wood behind the rubber as a safety factor Noise factor would be way down, I think the pellet would glance off the rubber onto the ground,
I think rubber is and will be the key factor in your pellet stop and noise reduction , Not Kevlar.
I know nothing about Dyneema so I can not say nothing about this material.

Mike
 
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I have a friend with a composit custom composit shop that got a contract to build some aircraft CF floor boards that will stop a ballistic projectile. They have been doing all kinds of R&D with Kevlar and other materials. One was a loose Kevlar sandwiched between two layers of epoxied Kevlar. They have come up with some designs that work, but they are only good for one event. All of the many materials they are working with, when loose you can poke a nail through by hand. Like oldspook, I found a body armor vest at a army surplus store that has worked best with pellets. It needs to have a solid backing like wood to hold it in place. Tried making a box out of 2 inch insulation foam, but it broke up. Vest material works good though, but so far has had only a couple hundred rounds. Maybe if a person could find some bulletproof glass and shoot that at a 45 deg angle it might last. I tried using a 12x12 piece of 3/16 T1 steel but it bent in a u shape and over time had holes in it. The problem as I se it is nothing stands up to repetitive hits over time. But then there is that old saying that says. People that say it can't be done are irritating to those that don't know it can't be done and are doing it. This is a great thread.
 
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Anything impact resistant is usually a little flexible so some of the force is absorbed. That's probably the only way to reduce noise too.

This is why I like to shoot ou of the window and aim down so the mud is my backstop. It's as silent as it gets and reusable. The same principle could probably be applied to a horizontal backstop with lots of sand bags or bags of soil. Then only the bags would need replacing. 

For a flexible resin with Kevlar mix, it's going to be a case of trial and error to see what works. You need a combination of high tensile strength, high shore hardness and semi flexibility. 

The store Smooth-on has a few resins that may work. They are labeled "impact resistant" anyway. 
 
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Bullet proof vest works in two ways first the back plate is more of a shock absorber to help keep a direct chest impact from breaking ribs and reduce damage to the heart and lungs from such a impact, It does act as a backup for higher/faster rounds. The quilted and layered soft weave is what actually stops the bullet
I have actually used loosely hung moving blankets to catch Arrows and it does very well so your idea of loosely draped kev may work but it will need to be quilted since a single layer most likely will not work.
That being said you might think about using the above mentioned use of moving blankets layered with one to two inche air space between each one. Leave the bottom and sides loose on all of them so they can wrap around the pellet and shed the K.E.
Not sure if I will have time this week but I have a airodam roof cover from a big truck that I am going to set up this way I will give it a try with my 357 If it holds up to that it should hold up to anything else
 
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If a quiet pellet trap is what you want just build one in similar construction to a LDC. Make a box with multiple fronts which represent the baffles in a sound moderator. At the rear would be a pellet trapping area filled with your choice of absorbent material such as rubber mulch or old magazines. The pellet would pass through the paper target, through multiple baffles and then into the absorbent material at the rear of the box. This is on assumption the shooter can put a pellet through the baffles which should be easily replaced as a wear item. If you really wanted to get quiet you could engineer a replaceable piece of thin rubber, inner tube scrap, to cover the opening to the baffle chamber to contain sound. Think of it as a "whipe" in a firearm suppressor. I try to define the desired result then go about designing a solution, a quiet pellet trap.
 
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