Beginner's Guide to Carbon Fibre Resin Infusion

It depends on the print.  Most prints have a high porosity and relatively low compressive strength so may be crushed or have a lot of resin soaking into it. A high infill level on the print may mitigage that. Obviouslty the outside would need sanding smooth and then probably best to lacquer it with a UV stable clear coat.  

We have a product called GC50 which is designed specifically for this purpose. It's a an epoxy-compatible polyester gelcoat designed only to be used in this way. Because it's polyester, it's pretty much perfectly UV stable; the epoxy-compatible bit means that it cures hard and smooth on the open face, ready for the epoxy to bond to it (rather than staying tacking like conventional polyester gelcoats do). The advantages to an in-mould coating are obvious (no dreaded orange-peel if your spraying's not up to scratch) but the disadvantages are a slight change to the appearance of the carbon, particularly when doing resin infusion, because the in-mould coating itself will go down with a slight texture and this texture transfers to the carbon fibre, and also if anything goes wrong with the infusion (a dry patch here or there) then you can easily patch it and then spray over it if you don't have an in-mould coating but if you do, it's much harder to recover.

Making such a size and shape as a singe piece moulding would certainly be a challenge, but not impossible. For sure you'd need a split mould, as you describe. Then, assuming the door opening is large enough for you to work inside, I'd probably turn the whole thing over so the door/hatch is underneath; much easier to work this way and you're not standing on the reinforcement as you get in and out.

Then it depends on the process you want to use. Prepreg would be easier to laminate but you'd need to be able to oven cure the whole 8m+ structure, which is probably not practical, and so you'd be left with resin infusion (mechanically better but more complicated to set up) or a conventional wet layup. Assuming you're looking for the best performance then that means infusion. To do this, start by flash-taping the seams on the splits (so they're airtight) and then lay in the reinforcement; you'll need a fair bit of spray adhesive to keep it on upside down in a cylinder. The resin flow will be much more complicated and hard to predict on this shape so you'll need to use microporous membranes (DD Compound MTI hose etc) to maintain airflow and avoid dry spots. Then, the whole thing in a massive bag which would almost certainly need to be an envelope bag (so, you're bagging the inside and outside of the mould, like a giant elongated donut!

If you're serious about the project, get in touch with our technical team and we can give you more detailed advice on products and processes. And, good luck with it!

Thanks for the comment, this is a very interesting question and absolutely deserving of its own video, either a spotlight, or possibly the main channel because it's an important part of a lot of projects. To summarise though, FusionFix EP will leave a residue but it can't be seen and doesn't remove easily. Strong solvents (like acetone) can remove the residue which will leave a very faint 'dither' on the surface. For most parts in most circumstances, we think you wouldn't need to do anything (i.e. just leave it as is) which is a game changer. If you thought the part might be exposed to strong solvents (like acetone) then you would want to remove the residue. But, to be honest, you'd probably need to be thinking in terms a tougher coating for parts that will be exposed to harsh chemicals/solvents anyway.

It looks good, just a dark grey colour solid material. You can sand, flat and polish the cut edge no problem.

We don't have a video on it, no. Mainly, it's to do with allowing the pressure to slightly reduce in the bag, this significantly reduces the volume of any residual air. The drawing in of the resin is done by the elastic tension in the bag and mesh. The resin uptake during this phase is minimal (maybe 10-20g on a part like this) but you'll tend to get a better surface finish as an micro-air bubbles will shrink down. Maybe we can look at it in more detail in the future.

Hi Mike, you converted your 914 to electric! Amazing project. For sure a carbon Targo top would go well with that. You're quite right that the attaching/latching hardware and accuracy would be the challenging part. Not impossible but a Targa roof is more complicated than a conventional static body panel. I hope you do it though, and be sure to reach out to our technical team if you need any advice on material or process selection. I wish you all the best with it.

The only time that there's a benefit in making a mould from carbon fibre is when you're using a high temperature process (like prepreg) and you're making carbon fibre parts. The reason for this is because at temperature, the CTE of the material (the mould and then component) really matters. Having a mould that has the same thermal expansion as the component you'll be making in it is advantageous. However, for room temperature processes, there's not really any advantage to a carbon mould. What could be an advantage would be a low-to-no shrinkage resin system. Uni-Mould (like the mould used in this video) is very low shrinkage and an epoxy mould would be even lower shrinkage. So, the shrinkage of the resin makes a lot more difference than the reinforcement, for room temperature processes.

The best solution is a high quality 2k automotive clearcoat. We'll be stocking a product called Fantom Clear very soon, which is one such product, although there are others, both in special 2k cans (the type you have to activate and then use within 48hrs) and spraygun type. Although we do have a clear gelcoat which performs very well in terms of long term UV stability, it's generally not the way we would choose to finish a daily-driven 'carbon look' component because it's harder to repair or restore.

Yes, if you can get the resin flow distances within the rules laid out in the video (or change resin system if you can't) then you should be able to infuse most shapes. It would depend on the dimensions and proportions of this cone-shape but (possibly with some trial and error) it should be possible.

'Galvanic corrosion' is a type of corrosion that occurs when you have two dissimilar materials, with specific properties, in direct contact with each other, in the presence of an electrolyte. In a carbon fibre context, galvanic corrosion is a concern when you have carbon fibre in direct contact with aluminium, in the presence of salt water. It's only an issue when all of these things are present. For carbon fibre vehicle panels, the risk is only really present where you bond carbon fibre panels directly to aluminium brackets or an aluminium subframe, and then use the vehicle in a way that regularly exposes these areas to salty water (like UK winter roads). Fortunately, the solution is fairly straightforward and is a case of making sure that any carbon fibre isn't in direct contact with aluminium, usually by adding a layer or two of glass reinforcement between carbon fibre and aluminium components when bonding or joining them directly together.

The weight saving benefits can be great compared to original OEM parts. On an R8 this is a cosmetic trim panel so replacing both on a track/race car is almost 6kg of saving alone!

Yes, you can post-cure the IN2 resin system. If it's practical to do so then it's generally considered a good idea. Post curing will improve the mechanical performance by a few percent and will raise the Tg (temperature tolerance) of the component. It can also speed up the cure, which can be very useful in high volume production. Please see the technical datasheet for the IN2 resin for suggested post cure cycles.