Dear community,

I have been using Easy Composites XT135 and XC110 Pre-Preg systems for a few months now and have steadily improved every step of the processing chain. The results are very promising indeed, and there are quite a few things I know for sure I can improve further. Now, I feel like I am approaching a juncture in the coming weeks where I will need to decide if I will commit fully to ooa Pre-Pregs or rather stick my nose in different areas of carbon fibre before deciding which route to take. The main issue I have with these ooa Pre-Pregs as of now is good reproducibility of high quality parts.

I live in the south of Germany, Stuttgart, and we have a flourishing carbon fibre industry thanks to the strong automobile/racing sector. I have been in contact with a couple smaller/medium-sized composite manufacturing companies to get their take on mould making, Pre-pregs, resin infusion and so forth. The general consensus seems to be that ooa offers good results, but more often than not their results are too inconsistent to be a serious alternative to autoclave Pre-Pregs or resin-infusion. I do not want to use resin-infusion because of the hassle it is, and because the part I want to make is relatively small compared to other projects. My main question therefore is whether I should stick my nose into curing Pre-Pregs under pressure or not. It does not necessarily need to be an autoclave, it could be a pressure-bladder with 2-3 bar instead. How much does pressure above 1 bar really improve the quality of the final parts? Are we talking a few percentage points, or are we talking a boost from 70% (ooa)  to 99% (2-3 bar) reproducibility of high quality parts? I know it is possible to produce high quality parts with ooa Pre-Pregs. But is it absolutely possible to achieve great reproducibility of high quality parts with ooa Pre-Pregs, or is curing under higher pressure that much superior in terms of reproducibility, enough to seriously consider it?

I would love to hear your opinion on that matter! Thanks.

I can't see how curing in an autoclave is going to be any more reliable than OOA. You still need to get the layup right with good technique, you still need to follow the cure schedule of the material, you still need to make sure the autoclave temperatures are even and that your mould is heating up evenly etc.

Realistically, when you have an OOA system that is designed to work without the pressure, then simply adding pressure isn't going to make it work any more reliably - it's a case of working out why what you've got isn't working every time. Whether it's an inconsistency in your oven or your cure schedule, or possibly more importantly whether your technique needs improvement - there's something going on that is causing the problems, and changing to autoclave isn't necessarily going to fix that, it's just going to add complications and huge expense.


Has I mentioned to you in our PM conversations, I'm yet to have great success with the XT135. I don't find it a very forgiving material to use, and the need for it to be absolutely perfect straight off the pattern means that it can be a very frustrating and expensive material to use. I'm still working on that though, as what I've been trying it on has been both non-recommended pattern materials, as well as some quite complex layups that really examine my layup technique.

That said, the XC110 has been extremely reliable for me when used in a wet-lay high temperature epoxy mould. It's perfect results every time, no pinholes at all. Very very easy to use, very reliable, very consistent results. So I think your consideration shouldn't be whether you change to autoclave or resin infusion, but rather whether you persist with the XT135 and work out where it's going wrong, or if you start off with making some hand laminated high temperature epoxy tools and get the XC110 working the way you want it to.

Thanks for your input, Hanaldo, great stuff as always.
I am also very confident in XC110, I just thought that there must be a reason so many companies still use autoclave prepregs other than that it is just the way they used to do things and thats why they continue to do so ... I get that some may think that if they already have an autoclave, they might as well use it, but that may hardly be the only reason. Using a pressure bladder for example takes out some error prone or at least time consuming steps like prepping a vacuum bag, no necessity for tacky tape or leaving the vacuum pump running (granted, you will need a compressor or something else to build pressure and maintain it properly).

Yes, we briefly talked about XT135, and it is a different story entirely compared to XC110. My results vary greatly and I do not know why. Getting a spotless XT135 tool is so essential. I am beginning to suspect that the 12k backing ply might be too thickly woven to really conform with my part geometry. But then again, I might be getting paranoid with XT135. I would have loved to give a 6k backing ply a try to tackle that suspicion, but as of now 12k is the only one available. I am using 2 layers of XC110 6k instead of one XC110 12k for a similar reason, I suspect the thicker woven 12k XC110 to be too difficult to properly apply and conform to the geometry of my XT135 mould. Do you have an opinion on 6k vs. 12k?

If you are struggling with the backing ply, you can cut it into pieces as long as you overlap.  When we did the video, you will see we used lots of pieces and overlapped them to help with getting the fabric to conform to the shape of the mould.  And As you can see in that, the shape was quite complicated so the cut pieces helped massively.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant