Composites 101: Carbon Fiber, Fiberglass, etc.

i got my plug made today.....i used dry wall mud for body filler, and to coats of epoxy to fill in all my sanding scratches. a clean room to do this in would be nice. im having trouble gauging how much resin to mix up...... a little goes a long way.
when i closed the garage door the plug was smooth as glass.

<a href="http://s722.photobucket.com/albums/ww228/mrbubblehead_photos/?action=view&amp;current=plugs005Small.jpg" target="_blank"><img src="http://i722.photobucket.com/albums/ww228/mrbubblehead_photos/plugs005Small.jpg" border="0" alt="Photobucket"></a>

You can wet-sand out the craters and dust particles, with 600 - 800 grit. From my experience, when you make your mold, use extra layers of FG mat around the highest edges of your plug (deepest edges of your mold), and extra layers in the space in between your two parts.

cool.... thanks hick.....

since the mold is so smooth do i just sand the very small imperferction? there are only 2-3 of them. or do i sand the whole plug. also, if i just sand the small imperfections, do i keep sanding with finer and finer and then polish to mirror finish like the rest of the plug?

im kinda broke and dont have any fg mat. but i have lots of fiber glass. a real thin piece shiny smooth piece for the first layer....then i was gonna use the thicker fiberglass i have to build it up. its not chopped glass but heavier cloth....maybe what, 10-12 layers. would that be sufficiant? or should i use more.

do i vacuum bag the mold? or is it not nesecary for the mold? i hope to make a dozen or 2 parts from the mold. maybe more

Would kevlar fabric work as a seat cover? Would it stand up to the sun and conform to the curves in the seat? I think if it would work, then I would not have to worry about abrasion anymore.



My stock seat cover is starting to give up.

Good luck

I believe when Kevlar is used as armor, it is sandwiched between other abrasion-resistant fabrics, such as Cordura. Layering Kevlar atop your seat without covering it with leather, "pleather", or some other abrasive-resistant material would only result in frayed material after the first use. Having worked with Hybrid fabrics of Kevlar, I can tell you that even a hangnail can permanently fray and damage the fabric.

Thanks, I had understood that kevlar gave a lot of abrasion resistance, so it seemed it me be a good seat cover materail. Hope you guys didn't mind the threadjack too much.

thanks hick. i think im gonna try to infuse it...... it looks like laying it up dry will be easier...

I don't want to attempt to overstep my boundaries of knowledge and experience here however I would like to add another ingredient to that skid plate. Carbon Fiber will only go far as to protect your vulnerable frame and engine casing from sticks and stones but once in a while your going to come across something with a bit more substance and mass and even the best built carbon fiber guard will suffer from a direct hit or grind.

The ingredient I wish to add is Kevlar. Extremely abrasive resistant and it wont shatter or brake in-half like carbon. I'm not trying to say that carbon alone is bad, just that your only addressing half the issue with carbon alone.

Assuming you are building this on a home made mold or are even using the OEM skid plate as the mold and that layer number is going closest to the bike, then ideally I would lay up this skid plate with layers 1-9 like this...
1. Carbon Fiber
2. Kevlar
3-6 Carbon Fiber
7 Kevlar
8 Kevlar
9 Carbon Fiber/Kevlar matrix

Between layers 6 &7 add a few strips of waffle cardboard. They only need to be a couple of inches wide but need to run the length of the bottom of the pan. It also helps if these strips of cardboard cover the mounting holes

It would also pay great dividends later to reinforce the mounting points with an extra layer or two of carbon fiber

I helped my mate build this same bash guard last month and it has seen some very aggressive testing over the past week. So far, the final layer (closest tot he ground) has shown the evidence of war. The carbon/Kevlar matrix has taken a good thrashing and the carbon strands show a bit of splintering in some places. However, the Kevlar has done it's job very well and it's damage is only cosmetic.

In hind site we could have, and should have, made the 9th layer Kevlar as well. It would have looked a bit odd as a final layer but in this case it's all about function over fashion.

I hope this helps,

Dave

Just want to make sure I have this right.

Make a model of what you want
Bondo it
Epoxy it
Wax it
PVA it
Box it
glass it

Pull the bondoed, epoxied, waxed, PVAd, Boxed model out.

That is my mold?

Thanks

D

That is the gist of it. Add in some sanding between steps, and you have it.

Epoxy first cause the bondo will eat the foam if that' what you're using. Use guide coats for each sanding session. Otherwise you just end up sanding in low spots and you're not sanding for any purpose really just wasting time and layers.

What's the boxing bit all about?

So the bondo then epoxy layer is pulled out and that is your shape? Meaning the epoxy layer on the bondo better be perfect because that is what your final shape is going to be?

Thanks.

D

Bondo will dissolve styrofoam, but I use styrofoam posterboard, and the Bondo dries before it dissolves the posterboard.

Yes, once the epoxy is added over the Bondo, that is your shape (plug). You'll want the plug to be as perfect as possible.

This is styrofoam posterboard, covered by 3-4 coats of Bondo.


After covering with 3-4 layers of epoxy:


Once the epoxy cures (1-2 days), I wet sand out the small craters and pinpoints, then wax, wax, wax.

The box:

I may have missed it. Why aren't you going straight onto the bondo?

Still not clear on the need for the box.

You can go straight from the Bondo'd part , I just find it is quicker and easier to cover a roughly sanded, Bondo'd part with epoxy. There is much less time spent sanding

Surrounding the plug with the box makes layup easier later, especially if vacuum bagging

I need a better source for CF cloth and West epoxy. I bought a few yards of cloth from eBay, and that is hit or miss. I've bought epoxy from www.carbon-fiber.us, but they are a very small shop and don't convey much about their custom epoxy mix. There are no local sources that I'm aware of. Anyone have a good mail order source?

I mostly use Jamestown distributing - they often run free shipping specials as well.

I have been following your work in expeditionportal, so cool, I am about ready to do that to my CJ8

Saludos