Working with Kevlar?

My car has a kevlar skid on the gas tank. There are a couple of areas that have gotten worn thin and I would like to undertake a repair/patch.

Does anybody have a link to working with Kevlar? Is it fundamentally the same as working with Fiberglass?

Sean

Robert might know (rallymech) I know he just made a Kevlar skid plate for a tank.

Working with kevlar is very similar to fiberglass. You have to use epoxy instead of polyester resin. The Kevlar is a pain in the ass to cut because it is so slipery. The guys at the store showed me how to put a strip of masking tape on the cloth and cut through it.

I just covered a fuel tank. Two layers on the bottom and three on the leading edge. It feels strong and didn't add mutch weight. I would have preferred to use an aluminum skid plate but there was no good way to mount it.

---

Robert.

"You are way too normal to be on Rally Anarchy." Eddie Fiorelli.

Works just like fiberglass, and as Robert said "use epoxy instead of polyester resin." I also really like the tape trick, I'll have to try that on an upcoming project.
If you are new to fiberglass/composites, look at some boat repair how-to's on the interlinks. They should have some tricks that could be helpful.
How big are the holes/patches? How thick is the skidplate in those areas?

The skid is about 3/16s to 1/4" thick by my estimation. The tears aren't all the way through, but up to 1.5-2" long and .5" wide. My plan would be to lay some Kevlar on the inside of the skid in the areas that are getting worn. I would assume it's as easy as cleaning the existing kevlar, brushing the epoxy resin on the area, lay in the kevlar and brush my epoxy over the top and let dry. Wash, rinse, repeat.

Thanks for the help!

Quote
SeanP
The skid is about 3/16s to 1/4" thick by my estimation. The tears aren't all the way through, but up to 1.5-2" long and .5" wide. My plan would be to lay some Kevlar on the inside of the skid in the areas that are getting worn. I would assume it's as easy as cleaning the existing kevlar, brushing the epoxy resin on the area, lay in the kevlar and brush my epoxy over the top and let dry. Wash, rinse, repeat.
Thanks for the help!

I've done some working with composites in a completely different application. So, fwiw...

Clean the area first and make sure it is completely dry
Scuff up the area to be repaired and clean off any 'dust'
Probably best to clean with something that will cut any oils or grease and let dry.
lay in epoxy
lay down 1 ply of kevlar
lay in epoxy
lay down another ply of kevlar at 45deg offset to the first (you probably want the outside most layer to be at 45 deg to the direction of travel)
Do all of this in one 'lay-up' NOT in repeated set-up, cure, set-up again steps.
Use quality resin
if possible, cure in a vacuum bag for best results.* (under vacuum, of course)
Make sure your kevlar is completely sealed. It will soak-up water/humidity that will lead to delamination fairly quickly (moreso with freeze/thaw cycles, but not good nonetheless)

*Under vacuum you can use a very small amount of resin and still have some squeased out of the actual area being laminated. More resin is not the same as more strength.

---

First Rally: 2001
Driver (7), Co-Driver (44)
Drivers (16)
Clerk (10), Official (7), Volunteer (4)
Cars Built (1), Engines Built (0) Cages Built (0)
Last Updated, January 4, 2015

Quote
john vanlandingham
Blame is for idiots. losers.

Thanks, Morrison.

Ask Dave Kern. He spends more time doing that than anything else on his race cars.

---

Grant Hughes

Quote
SeanP
Thanks, Morrison.

No problem.
Caveat: That's all been from my experience, by all means weigh other thought opinions as well. My application was in R/C Gliders at a reasonably high level of spec. Strength and light weight were priorities.

---

First Rally: 2001
Driver (7), Co-Driver (44)
Drivers (16)
Clerk (10), Official (7), Volunteer (4)
Cars Built (1), Engines Built (0) Cages Built (0)
Last Updated, January 4, 2015

Quote
john vanlandingham
Blame is for idiots. losers.

Edited 1 time(s). Last edit at 06/10/2013 12:11PM by Morison.

One thing I've always wondered, how well do people think Kevlar works for fuel tank protection? Does it disperse load or just prevent impacts? Thinking mostly about the BMW plastic fuel tanks and if Kevlar (or aluminum for that matter) will really prevent them from still breaking.

---

Grant Hughes

I am more concerned with puncture than big impacts.

Quote
SeanP
I am more concerned with puncture than big impacts.

I'm more concerned with blowing up or burning to death.

---

"Talk about drugs. Driving a car like that, going that fast, it’s like all the drugs at once." - Tommy Byrne

"Now, Pinky, if by any chance you are captured during this mission, remember you are Gunther Heindriksen from Appenzell. You moved to Grindelwald to drive the cog train to Murren. Can you repeat that?" - The Brain

The one thing to be mindful of with the 'tape trick' is that the tape will never come off. If you have the luxury of making the piece oversized and trim it down later, its not much of a problem. But if you're the kind of person who sees blue painters tape laminated into the tank...just take the time to cut it as-is.

Also, pulling one thread like you do for carbon to help you cut a nice straight line will make cutting kevlar even harder as the threads will have an easier time running away from the cutting action of the scissors.

Dave

Another note, most of the epoxies for composites are measured by WEIGHT not volume.

---

Welcome to the cult of JVL drink the koolaid or be banned.

Quote
Dazed_Driver
Another note, most of the epoxies for composites are measured by WEIGHT not volume.

Maybe the industrial stuff is different, but most are metered by using different amount of pumps. System Three is 2:1 and the stuff I got from USComposites in medium cure is 3:1. Both of those have you use the same volume pump in the resin and hardener bottles. West System comes with their own pumps and I think you always use a 1:1 ratio and the volume of the pumps is where the difference is made up.

Dave