Introduction: DIY Simple High Quality Carbonfiber Parts
In this Instructable, I will show you how to make a very simple and yet very high-quality Carbonfiber part without complex mould making and Vacuumbagging. To myself, I am a German Examined Lightweight Aircraft builder, and a lot of my skills I learned from working at JH Aircraft, especially making extreme lightweight Carbon parts for one of the most advanced Ultralight Aircrafts. Making such lightweight parts, of course, takes some practice but with my help, you are off to a good start, and with some practice, you should get some very good weights after 2-3 tries. for the Example Part, I am showing you how I made the Prototypes for Armrests that I made for my Velomobile(last picture) and also show off a bit of the Mould I use for Serial production of the Armrests.
Step 1: Tools and Materials
I will show you how to make simple Carbon Parts so you will only need simple Tools
for the Mould
XPS Foam - EPS foam works too but is very soft and bad to sand
Cardboard - if you like to use a cutting template
Plastic Film(the stuff to wrap food)
Tape - duct tape and light double-sidedtape (3m924)
for the Part
baking paper - for pre-laminating the carbon and not spill resin to your table
Carbon fiber - 160g/m2-200g/m2(5.7o.z/7oz) 2x2twill
- 80g/m2-120g/m2(2.8oz-4.2oz) UD non crimped
Epoxy Resin - for Laminating, example: https://shop1.r-g.de/en/art/109285-AP
where to buy?
Germany - https://www.r-g.de/
Germany - https://shop.hp-textiles.com/shop/en/
for Mould making
Scissors - for cutting cardboard templates or plastic film
Pens - for marking
Ruler/triangle ruler - for measuring
Hotwire cutter - scrollsaw type(what I used) or Bow(picture)
instead of Hotwire a Bandsaw or scrollsaw also works - depends on your part
some pins/nails - for fixing a template to the foam
Sanding Tools - Flat Sanding bar, Round sanding block, soft sanding block
Sandpaper - a bit of 60 and 120 grit
for the Layup
mixing cups and sticks
scale - 0.1g (0.01oz) accuracy or better recommended
plastic tray with a foam roller (5/7,5cm - 2/3inch)
Brush - I didn't need it but depending on your part you might want one
acetone - for cleaning your tools - wear gloves !!!
Multicutter or Dremel tool with a diamond wheel - for cutting the cured Carbonfiber
a small angel sander (not necessary)
some 60 and 120 grit sandpaper
A vacuum cleaner with a proper filter
for your Safety!
for working with epoxy wear Nitrile Gloves!
I like to wear cotton gloves underneath nitrile gloves to prevent sweating
for working with epoxy safety glasses are recommended!
if you work with epoxy in a closed room better wear a proper respirator for paint!
when cutting carbonfiber wear safety glasses and a proper respirator!!
when cutting carbonfiber always have a proper vacuum cleaner running!
to prevent splinter wear gloves!
with powertools earmuffs are recommended too!
Step 2: Mould Making
When you want to prototype a composite Part and only want to make 1-3 Parts, it would be a waste to make real composite moulds and a simple Foam mould is sufficient. for my Part, I made a foam mould that worked perfectly for 3 parts, and now that I know that the shape is good and I want to make a lot more of the parts, I made a proper Mould for them.
How did I make the Prototype Mould?
There are different Mould types, Positive and Negative Moulds, with Positive Moulds you put the Carbon on the Outside(what I used here), with Negative Moulds you put the Carbon on the Inside (like a bowl). for Prototyping simple parts it's mostly best to use Positive moulds because you shape the foam how you need it and then just lay your carbon onto the mould. for production parts you mostly use Negative moulds because you want a shiny outside surface or want a part where you want to do secondary bonding inside the mould for example ribs inside an Airplane Fuselage.
for my Part I made a Cardboard template with the crosssection of the Part, stuck it to a block of foam and cut it out with a Hotwire. to get a good release of the part, you have to look at your mould and try to get a draft angle of about 1-2 degrees, that means you want the mould to be bigger at the bottom(see the Mould Type picture)
after hotwire cutting I didn't get a smooth surface, so I sanded it, if you have complex shapes you can make yourself a special sanding tool or use soft foam as a backing for the sandpaper. for Sandpaper I would recommend 60grit for shaping and some 120grit for a smooth surface.
For my part I wanted to have a Box with a kind of tongue on it and to make the tongue I lay the Positive Mould onto a flat plate(more info in later steps)
How to make the Mould not stick to the Part?!
for proper Moulds you use release wax and sometimes PVA but for a foam mould that's not very good.
I wrapped my Foam mould with Plastic wrap(the stuff you cover food with) I used small stripes and taped them to the bottom, you have to do this carefully to not have tape on the surface where you later lay on Carbon fiber because it will be harder to demould. If you only want to use the mould once you can also use tape, for my first mould that didn't work because my draft angle is quite small and I had to destroy the mould. If you have a flat part it shouldn't be a problem to use tape.
no matter which method you use, pay very close attention to not have any open spots on your mould where resin could get to the foam Mould!
Step 3: Prepare the Layup
there is not a lot to prepare for this simple layup but preparation is key to success!
things to prepare for the Layup
check your Mould again for proper coverage with plastic film/mould release
cut all the carbon fiber
put all the tools, materials, and moulds organized on your workbench
- put down the Tools: foam roller with tray, brush, scissors
- prepare worksurface: put down baking paper for the Layup and to secure your workbench
- organize all the cloth the way you want to apply it
How much and What Carbon to use?
how much of what Carbon you need is totally dependent on your strength requirements.
to get the best result you will have to do some testing, but I will give you some tips to get a good result at your first try
I listed two types of Carbon, woven and unidirectional.
the woven type is the typical Carbon Look and will probably be your last layer(outside) the Unidirectional cloth is good if you need strength in one direction, it is comparable to the grain of wood, for my part for example I wrapped two layers around the box to get the most stiffness when trying to squeeze the Box together, that's the strongest load the part has to withstand, to get some twisting stiffness and to prevent the ud cloth from splitting and also get the nice look I added one layer of woven Carbon. The Carbon layer is laid at a 45deg angle to the UD cloth. for your Part, you should define the 0deg direction so you later know where to lay the cloth in what direction.
for your part you have to look at your part and think about the loads it will experience, if you only have a cosmetic part 2-3 layers of the woven cloth should be enough, depending on the size and shape. to get the most stiffness the shape is very important, if you add features like corrugated sheets have, you add a lot of stiffness in the direction of the feature. Also if you have a direction where your part experiences high forces, like mine, you can add UD layers in the direction of the force, for example at a bridge you would lay a lot of UD cloth along the bridge to prevent it from bending.
I could write even more about how to choose the right cloth, but its very complex, and with this information, you should be off to a good start and to get the best possible layup you have to do some testing, for my parts the 3rd set is now how I want it. If you need some advice, write a comment or contact me on Instagram.
you can see my Layup schedule in the last picture of this step.
for some good tips, you can take a look at this, its half German/English: https://www.r-g.de/w/images/6/69/R%26G_Handbuch.pd...
how to cut your carbon?
you have to closely look at the direction of the carbon, you should have a basic understanding of the cloth direction if you read the last section, for cosmetic parts just alternate between the fibers running +/-45deg and 0/90deg along your part.
to have a good layup you also have to think about laying the carbon onto your part, woven carbon is very nice for complex shapes, but there is a limit with wrapping it around complex curves. for my part, I have 2 pieces for the box, one for the bottom and one that wraps around the sides, this way I get the least amount of shifting with the woven cloth(look at the pictures of the next step). For overlapping the joints you roughly overlap 1cm per 100g/m2 cloth, so I used 200g/m2(7oz) and overlap it about 2cm(~0.8inch).
you have to experiment with the wrapping of the carbon and to get some experience you should cut your pieces of cloth a bit bigger and cut them to size while laying them up. with more experience, you can cut your cloth more precisely with every part.
for my part, I now started serial production and I don't have to do any cutting while laying up, I also cut cloth for multiple parts and store the pieces in a cardboard folder. On the 3rd layup, I didn't have to cut any cloth, the precut cloth was the perfect size and I just have to apply it to the mould and done.
Step 4: The Layup
The Layup is where the magic happens!
usually, you brush some Resin to your mould, put the Carbon on it, and brush a ton of resin on it to get it properly saturated, that's how you can make parts fast and reliable, but I want to show you how to make parts with hand lay-up that weigh less than a Vacuumbagged part and weight nearly as little as prepreg parts, the secret is that you basically make your own prepreg on the go!
If you properly did step 3 you should be able to start right away with mixing Epoxy, to mix up the right amount of epoxy you can simply weigh your cloth, add about 20g (that's for the foam roller) and you shouldn't be wasting a lot. Mixing epoxy has to be done carefully, you should carefully weigh the Resin/hardener parts within at least 5%, better 2-3%. Closely look at the Datasheet of your Resin system and write down the Mixing Ratio in big letters onto the Bottles. Mixing has to be done accurately too, mix for about 2 minutes and regularly scrape the sides and bottom of your cup and your mixing stick.
Always when working with Epoxy, wear Nitril gloves!
Pay attention when mixing, there will be small resin bubbles popping up, flying around your Workshop! wear glasses and a respirator!
To Start your Layup, pour the Resin into the plastic tray and roll a bit onto the Baking paper, put your first layers of carbon onto the Resin and roll carefully more resin onto it, very little, just as much that it barely starts to look like shiny resin on the Carbon. you can also remove resin again by using paper towels. carefully lift the carbon up from the Baking paper and put it onto your mould, it should barely stick to the mould, before wrapping the piece around the mould you can already start to put the next layer onto the baking paper so it can start to soak up some resin. when you have problems with the cloth sticking to the mould or the next layer you can use a little bit more resin. When you applied all your layers you can add some Peelply if you want to do some bonding later but I wouldn't recommend putting peel-ply onto the seams, if you don't want to sand later you can wait about 2 hours(depending on the Pot life of your resin) and push the fibers down when it starts to cure.
after curing for about 12hours at Room-temperature I put my parts into a foam oven and slowly increase the temperature to about 40-45degC for about 10 hours. If you don't want to make a simple oven(highly recommended) you have to let it cure for at least 36 hours before doing more work with the part.
If you have a fillet as I have on my part, you can fill it with foaming resin, you should do it when the resin is hard but not fully cured, so about 12 hours after the layup so it still has a chance to properly stick to the epoxy.
Here is a timelapse of my 3rd Layup, maybe I will do a video later where I closely show the process of the Layup...
Step 5: Demoulding and Triming
After Curing you can demould your Part, I made a simple handle to pull my mould out, the plastic film worked perfectly! if you have problems demoulding you can use thin wood or plastic sheets to get between your part and the mould.
After demoulding you have to cut your parts to the size you want, you can see how I marked my parts...
for cutting a Multicutter or Dremeltool with a diamond wheel works great.
always use glasses, a respirator, and Vacuum cleaner when cutting/sanding Carbon!
after cutting you can sand it to the exact size and also carefully sand down the open Carbon Splinters.
I weight my Parts before cutting anything off, my 2nd set was nearly a bit too light and flexible, at 90g with 50g of fibers, so fiber/resin content of about 55/45 that's nearly as good as resin infusion!
the 3rd set is nearly perfect and about 113g with 60g of fibers, fiber/resin ~53/47 not as good as the first but still better than Vacuumbagging!
Step 6: Finishing and Mounting
to finish my Part I added some Velcro on the back for Mounting and made some EVA foam parts to not scrub my elbow on the pure Carbon Fiber.
before sticking any tape to the parts, as always with bonding, degrease the bonding area and then stick on your Tape.
I hope my first Instructable is already good enough to show you everything you expected from the title and properly explain it to you. If you have any questions, just write a comment or contact me on Instagram:https://www.instagram.com/nbfaserverbundtechnik/
If you like the Instructable please share it, tell me about your projects, and if you need some Carbon parts but don't want to do it yourself you can contact me: https://www.nbfaserverbundtechnik.de/
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