Carbon Fiber Tutorial (Plug, to Mold, to Part)

[nigelpheron]

Here is a way to make yourself, some custom carbon fiber parts, without using high-tech, complicated proceedures. Sometime for the size and quantity of the part desired, complicated proceedures are a complete waste of time and money.

We will be using glass fibers, carbon fibers, epoxy resin, and some powdered resin additives. I will detail the Plug's construction, making the Mold off of the the Plug, and then using the Mold to make the desired part.

Materials list:
-Room-temp cure epoxy resin and hardener.
-5 to 10-min epoxy glue and hardener.
-Various weights glass fiber woven cloth, mostly 2oz. 4oz. and 6oz. weights
-6oz. 3k carbon fiber woven cloth.
-Cabosil (Like flour for baking, used to thicken).
-Q-cell micro balloons (micro glass bubbles, to make light-weight, easily sanded mud.
-Graphite powder, to add blackness, hardness, and slickness to your resin.
-Honey wax mold release agent.
-Poly Vinyl Alchohol PVA mold release agent (insurance! LOL).

This tutorial will focus on the tranny floor cover, for my 1.9 scale build

First thing to do, is to make a Plug of the part you want to produce. It can be made from what ever material you can find, but keep it cheap, because this plug is sacrificial. For this part, I used scraps of balsa wood and blue foam



Preparing some reinforcement to go on next. This skin will act as a hard base, to be built up into a smooth finish. The smoother you make the Plug, the smoother the Mold & Part will be. Unless you want a different finish on the final part, like a mat-finish or a texture of some sort.



Pre-shape your reinforcement (6oz. glass fiber 0-90 cloth in this case), over the plug. This will make it easier to drape, over the sticky Plug to come. Using this technique helps big time with complicatedly-shaped items.





Next to do is to wet the Plug with epoxy; either in resin form, or fast-drying glue form. The resin method is slower but stronger, and the glue method is just the opposite.



Resin method. Mix up some epoxy resin, and paint it on to the Mold. Add graphite powder in the resin, to add blackness and hardness to the Mold. This will make it easy to see, trapped air bubbles when using glass fiber to make your parts out of, when the Mold is ready. Doesn't apply with carbon fiber, because unlike glass, it doesn't go clear when you wet it out. Room-temp epoxy resin, cures hard enough to sand in 24-hours. At about 3-hours or so, the resin is at a sticky stage. The reinforcement cloth can then be pressed onto the Plug, and the sticky resin will hold it firmly in place. The resin should be soft enough that the cloth really sticks to it, but not so soft that resin comes though the cloth and gums up your fingers. Messing with this method over time, will help you learn the resin you're working with, and help you know exactly when the resin is ready to stick the cloth into it.

Glue method. The same thing can be done with epoxy glue, but you have to have your steps perfected, because you have to do this method fast. There is a very small window, for when the resin is at a stage, to stick the cloth on to it.

After the cloth is stuck onto the sticky Plug, let the sticky resin harden a little longer, to really hold the cloth in place, so that when you wet out the cloth, it doesn't come off the epoxy underneath. About 1/2-hour longer with the resin, and about 1-min with the glue.



Wet the cloth out with some epoxy resin.



When hardened, sand the edges of the cloth surface, to clean the Plug up and get it ready for fairing. Coat the the Plug's glass fiber surface with a fairing compound, so you can sand the Plug smooth, ready to cast a Mold off of it. My fairing compounds are made from epoxy resin, thickened with Q-cell for ease of sandability, Cabosil to thicken and add thixotropic properties, and sometimes Graphite powder to add blackness, and to aid in seeing what you're doing, or for hardness and slickness.

Nice and slick: For the last step on the plug below, I quickly mixed some 5-min epoxy glue with graphite powder, and rubbed it all over the plug with my finger. It's thicker viscosity makes it settle really smooth.

To bring the surface to a really good class "A" finish, wet sand with 400grit, then 800, then 1200grit. Now time for compounds. Use a medium cut cleaner, and rub the hell out of the surface, then buff with a clean towel. Now do it again with 3M hand-glaze, and that sucker will really shine!



Now to cast the Mold. You have to prepare the Plug, so that nothing sticks to it. There are all kinds of release agents on the market. I find it's not the product that makes for good results, it's the routines and step by step methods that make for good consistent results. I use Honey Wax, an Poly Vinyl Alcohol. I wax the Mold one good time, making sure to not miss any where (The reason the instructions say to do multiple wax coats, is cause people like to rush, so many time makes up for lasiness. Once pores are full, ya cant fill them more, so one propper coats is all that is needed). Some wax multiple times so the Mold can pop out many parts, with out waxing in between casts. I've witnessed many times, when Molds have gone too long with out waxing, that has caused the Part to stick to the Mold, causing damage to both. I wax and PVA my Molds once; everytime I use them, and in nearly 25 years, I have never had a part stick in the Mold. Consistent repetition is the key!

For the PVA, apply some to the Plug, and rub it all over with your hands. It's safe on your skin, but if you have Mary-hands wear gloves. As the achohol evaporates, you will feel the PVA getting thicker. Now it feels like the part is greasy. Then leave it let it settle and dry. If it starts to get to dry and your fingers start sticking during the rubbing, just wet it with more PVA and continue. PVA is water soluble, so if ya really mess it up...I'll make a vid on this, to show the desired method.

When the Plug is ready, mix up some epoxy resin, with graphite powder, and cabosil powder to thicken it a little. Thick enough like runny cake icing. This will make a thick base layer, that will be the surface of the Mold.



When that gets to the right sticky stage, put on the first layer of cloth. After it hardens a little longer, wet out with epoxy resin / graphite, and wait for that layer to sticky and put another layer cloth, repeating until you have reached the desired number of layers for your Mold. Rull of thumb is 4-times the thickness of your Part. This sticky / apply cloth / wet-out method, is good for tricky shaped items. For a shape that is simple like a flat plate Mold, ya just do the sicky part once on the very first coat of epoxy. For the rest of the layers, you can do them all at once...glass-layer / wet-out, glass-layer wet-out, until the thickness is reached.





Release the Mold when dry (min 24-hours). Start with working the edges loose, and using a plastic wedge (used up Timmies or similar plastic cards work awesome), to seperate the Mold from the Plug.



Edge-sand and clean the Mold, and prep it for casting the Part. Same as with the Plug, wax and PVA it...
For the tranny piece, I used the glue method for the first layer. 2-3mins later at the right sticky stage, I jammed the pre-shapped 6oz. carbon fiber plain weave cloth into the Mold.





When the glue hardened 1-min later, I wet out the carbon with resin. 3-hours later when it stickied up, I put on a layer of .75oz. glass cloth, to act as the minimum second layer, which will help seal the carbon cloth. 1-layer carbon, 1-layer fine glass is the minimum amount of layers for a Part. If I wanted this Part strong enough to jump on with a work boot, 6-10 layers of carbon would make it indestructable.



.75oz. glass cloth stuck on:



Wetted out:



Cured, released, edge-sanded, hole for slipper adjustment, and washed. It's a little resin-rick in some spots, but this piece was done for quickly for the tutorial, and the parts will be painted anyway.



Mock-installed:

[JohnRobHolmes]

Great tutorial! I'm sticking it for future reference.

Can you go over the plug polishing a bit more? I know the finish on the plug determines the surface of the mold and therefore the final part finish. It looks like you just sanded down the plug filler smooth (what did you use for filler?) and waxed it shiny, is it really that simple?

[nigelpheron]

Will do John. I'll get to it later on today. I'm the Sunday man @ my Friend's shop, so got to run to work now.

Your ESC and Team Crawlmaster motor are planned for my truck by the way.

I have some other methods to write about as well, and will update this thread with their tutorial.

[iguana102602]

Great tutorial, I've always wanted to try this but never really understood the entire process. Now I have to find the materials.

[nigelpheron]

Some have asked about my method for constructing my seats. So, I will give a little tutorial on their construction method. This requires no high-tech tools or processes. Just a little patience.

First, you need to carve the core. In my case, it was 1/8” balsa wood. Easy to carve and sand. Foams could also be used, from high-tech Corecell, to blue / pink foam, and depron. Honey-combed Nomex or Kevlar can be used, as well as cardboard when done right.

Here is a pic of the interior core, made from balsa like the seats.



Once you have your core shaped, make sure all corners are radiused and filleted. This makes draping the reinforcement (carbon fiber cloth in this instance), easier to make the corners, and also to have no air-voids in the corners.

Filletting mud made from epoxy resin, cabosil, and micro balloons.



Note mud fillets in the inside corners, and the opposite outside corners sanded round.





Now for laminating the carbon skins. Cut a piece of carbon cloth (glass cloth in shown in picture), and pre-shape it by pressing it onto the dry part. This pre-shaping when the cloth is dry, makes it easier to stick it onto the core, when it’s sticky with the curing epoxy resin.







Now for the resin, or glue...If you’re quick enough. If your quick enough, you can mix up some 5-min epoxy, and quickly coat the one side of the core. Now, while watching and touching the epoxy film now and then, you are waiting for it to cure just tacky enough to press the dry carbon cloth onto it. If the glue is at the right stage, the cloth should stick onto it good, with out slowly releasing out of the corners (when the glue is still too wet). If the glue is still too wet, the glue will easily come through the cloth, and get your fingers all sticky. And, the carbon being stiff-ish, will want to come away from the corners.

The 5-min epoxy glue method, is not as strong as doing the sticky part with epoxy resin. The resin method is stronger, but takes longer to “catch it”, in the right tacky-ness. I find after about 3-hours of curing, gives the right amount of tacky-ness. Another 45min. after that, and it’s holding the cloth secure enough, that the wet-out stage can begin. If not enough time has passed for the epoxy to grip the cloth, wetting it out might loosen it from the sticky bond to the core. Not good.

Method shown on the construction of my tranny-cover plug.



3-hours later, cloth stuck down to sticky part.



The resin is holding enough, and the cloth is now held in position, ready for wet out with epoxy resin.



Once the wetted carbon-clothed core is dry (next day or so), wash the part in cold water, to remove any formed “Amine Blush”. A waxy film that appears on the surface, of the dried epoxy-wetted part. This film on smooth surfaces can trick the inexperienced, into thinking the epoxy did not dry right. Wash the part, dry it, and if it is still tacky; ya, the glue didn’t cure right. After thoroughly dried, edge sand the cored part, and lightly sand the carbon cloth surface, to clean it up.
I use Nortons Blue Magnum sand paper for everything. For these I'm using 80grit.

Carbon dust is tenaciously itchy, and absolutely do not breath it. I try to do all my sanding outside, to keep that itchy stuff out! Remember to always wash your composite work clothes, separately from your other clothes.

A test piece here, to show what I mean.



When the part has been washed and dried again, it’s time to take care of the exposed core edges. Take some rolled up sand paper (about 1/8” round), and sand the core edge to make a u-shaped groove between the two carbon skins. Then mix some epoxy resin, with graphite powder and cabosil powder to thicken it slightly. Then fill the groove with this thickened black epoxy, to seal and give the edges a finished look.



(insert epoxied edge pic)



After the edge-resin is dry, clean the edge up with some sanding.



Mix up some more black resin, this time a wee bit runnier so as to flow better, and coat the edge again. Done right, the epoxy resin will flow into a nice radiused edge (meniscus flow). To runny, and it will pool in low spots, or even drip off the edge.



Here the resin has pooled into a nice edge.



After a light sanding of the epoxied edge, the entire surface of the seats get a light epoxy resin coat, to seal up the cloth.



When dry, I'll green Scotch pad the seats, then mist a satin clearcoat on them, and add some details like harness cut-outs, harnesses, and cushions.

(insert final tutorial pic).

[SVEN]

Great tutorial!! I can't wait to have a reason to try it out.

[SlickRockSpider]

Wow That is realy cool. thank you for taking the time to show us. Making parts out of fiber glass or carbon fiber makes fabing parts a in house a low investment. No expensive tools. I have for years wanted to try making CF parts. Right now I am working on a vaccum former. Another form of fabrication that can be done in your apartment. Thank you

Evan

[nigelpheron]

I'm glad you find the tute helpful. I want to encourage all to mess with new mediums, just like these wee truck forum folk, have taught me to work with new mediums...Steel, styrene, etc.

Vacuum processes are very useful tools indeed. Even just for taking bubbles out of plaster mixes, forming sheet plastic, or debulking composite lay-ups.

[Harley]

Great work Something I have always wanted to try myself.

[BC-Brian]

Cool stuff man, thanks for sharing.

[DickyT]

5 Stars

Awesome tutorial, thank you for your effort!

[nigelpheron]

Eh Gang. The tutorial is just one of many methods of working with composites. So if any of you have questions about other methods, please ask away.

[sgl]

Thank you for the tutorial, there's enough detail for me to give it a try.
Thanks again.
sgk

[nigelpheron]

Originally Posted by sgl

Thank you for the tutorial, there's enough detail for me to give it a try.
Thanks again.
sgk

Yes; try, and try again. The more you mess with the material mediums, the more you learn their characteristics. Then they can be propperly adapted to your designs.

[TnT817]

Have you ever used pre-impregnated carbon? I did a few pieces in school with it. We used a bag and sealed it up then vacuumed formed the part and baked it. They had all the fancy stuff at school to do it, but I'm wondering if you could do that and then heat it in the oven at about 150 degrees (I think thats what the temp was, its been awhile).

[nigelpheron]

Yup. I've making my "time pre-pegs" for years; as well as using professional pre-pegs from SP / GURIT, on the 60" Spirit of Canada project.

The carbon fiber pre-pregs from SP were frigg'n strong. We once took a triangle shaped piece of 200gm, rolled by hand as tight as we could, so it made a splike with the fat end about 1/2". We hammered it through a 1" wooden work bench table easily, with no tip deformation. We horded as many scraps of that stuff for our hobby-ing. My freezer was full. Frozen peas, perogies, some ground beef, pre-peg carbon fiber...

I just used the time ones on these last night actually:







It will be fully functional, and able to carry real gasoline. That's the reason for the resin-rich glass layer inside, to seal it up good!

[TnT817]

So you do use your oven to cook them in? If I remember correctly at school we put a cardboard box over the part in the vacuum bag and they had this little heater with a probe on the inside of the box that heated it.

What do you use to form your pre-preg? Vacuum bags? I think I may be able to get my hands on some pre-preg carbon and kevlar if I can do it at the house.

[nigelpheron]

I've used all kinds of ovens. From heated box home-builts, to the one in the kitchen.

Pre-pregs are really an over-complicated procedure to use for most parts. Only when a need a precise amount of resin, to flow a certain amount, under a certain pressure, at a certain temperature. Such as honey-comb core construction.

For the time method, get wax paper, lay out your cloths, wet out and roller each layer, and let set up enough for the application. Then just mush in on to what ever your doing. Eg. When I go to make the front light covers, I will simply cover them with aluminum tape. There's the male mold. Wax & pva the alu tape, then drape on the pre-preg, and mush it into place. Pop it of when dry, sand & finish the outside. Like the spur gear cover

[nigelpheron]

If you are wondering how precise home made pre-pregs can be, on my past production boats, the one's hull used the exact weight cloth cut to pattern, with a resin content counted to the drop, making each hull come out the exact same weight. 21gm. hulls for each of these:

[TnT817]

Thats some awesome work! I only used the pre-preg stuff because it was available to me. It was just used for cover pieces to my battlebots that I made. I may have to start giving this a shot at home this time!