kevlar advice please

[JimWoo50]

I decided to sandwich a layer of kevlar into my windscreen to canopy gap filler so it would be stronger. It certainly is strong and was very difficult to cut. The rotary cutter wouldn't work so I borrowed a pair of my wifes sewing scissors and was able to slowly cut it. Its now on the canopy but I'm finding it is very hard to sand and otherwise work now that it is hard with epoxy. I would like to sand off the rough edges and cover it with another layer of e glass. Any tips on how to work with this material would be appreciated. Thanks Jim.

[newtech]

This is one of those cases where I wish you had asked about kevlar before using it. You have already found out why I don't recommend it for very many uses. It is so strong that once it is in a layup none of our tools will do anything but fray the edges. Unless you are using something like a water jet cutter. About your only choice is to completely encapsulate it in the glass epoxy layup so when you sand you are only sanding glass and epoxy. Another option is to dig it out and redo it with glass. I know that isn't what you were wanting to hear. If someone else has a better suggestion I would love to know what it is.

The sad thing about kevlar is you very seldom get to use it where it actually contributes to the strength. It stretches more than glass or carbon so if it is used with either of these the glass or carbon will fail before the kevlar can start contributing to the strength.

Sorry,

Steve Eberhart
RV-7A bolting on the tail

[Hostage46]

Any stainless steel scissor can be quickly and easily converted to cut Kevlar. Just run the blade across a disk sander at a 90 degree angle, one or two passes on each blade is all it takes to modify new scissors or to "sharpen" them after they get "dull". (if I could post a picture here It would be eaiser)

[jcoloccia]

Yikes. Any attempt to sand the stuff will probably make it look like it went on a trip to Hair Club for Men. Can you say "fuzz"?

I don't know how much room you have but my suggestion would be:

1) Use a SHARP blade to cut through the Kevlar and trim it back as much as needed (or as much as you can). #11 X-acto blades or a single edge razor. Buy a whole box....you'll need them. Just keep scoring over the same spot and you'll eventually get through. And keep the blade SHARP.

2) When you're done, maybe some micro around the edges to give you something to sand smooth.

3) Put a layer of glass over it so you have a reasonable material to work with for your finish work

Maybe someone else has better advice but this is all I've ever gotten to work for me. My least favorite cloth to work with by far. I normally take great pains to cut it to EXACT size, or slightly undersize. What am I saying? I normally take great pains to use glass or carbon fibre instead

Good Luck! Let us know how it turns out and how you eventually were able to work it.

[Ironflight]

You do realize that you probably owe your wife a new pair of sewing scissors as well, right?

Well, you did ask for advice....

[BJohnson]

The nice thing about laminating Kevlar into a layup is that when you want to remove it, it easily peels off the layup because the bond between the epoxy and the kevlar is very poor.

If you want to remove the kevlar, start at an edge and begin the separation with a knife, then you can wedge or peel off the laminate above the kevlar along with the kevlar.

[RV505]

It is sheeeet material. I personally removed all of the kevlar out of all the Fairing panels / fairings for a major airlines A-320 fleet and replaced it with fiberglass.. It will suck water into you project and blow your panel out.. Just you wait!! Do your self a favor and remove it now!

[cobra]

As I remember from my composite days, Kevlar is very good for impact resistance (as in bullet proof vests), but tends to be brittle and does not stick to epoxy well. For strength/ stiffness, graphite cloth is preferred.

[JimWoo50]

Started under a corner, grabbed it with a pliers and off it came. Took about 5 minutes. I wouldn't have guessed it was bonded soo poorly to the glass underneath. Thanks to all for the advice. Now I'm just going to put a couple more layers of e glass and that will be strong enough.

[osxuser]

Would Carbon Fiber be a good addition for strength? Or are there any gotchas with that as well?