Hi guys what trick are you using when doing wet lay ups in order to have perfect part with no pin holes or bubbles, or the only way to achieve such results is via resin infusion? any help will be greatly appreciated.
thanks
I am not good at hand laminating, and only with infusion I get pinhole free laminates.
Infusion and prepregs are probably the only way, hen hand laminating it takes a lot of time to get good results, not very reliable or transferable on to other people.
I had similar problems when I started and to be honest I cannot give you a single answer or a single bit of advice to help… Mine was a combination of things which ALL had to be resolved… I use Polyester so time is a little more critical… I had to spend more time making sure the surface layer of carbon was fully down… Make sure air could be pulled off the surface… make sure any peel ply was not bridging over areas too…release film has enough perforations but not too many that it wicks extra resin off the part through the peel ply… ( I perforate my own film depending on the part I am making and may add more perforations where I have a problem mould or less where the mould works really well) Working the bag over the part when there is a vacuum over it and really working the bag into every area possible… Breather not just over the surface of the part but all round the mould too… I may also thin the resin down a little to get it to go into every area but again have to be careful thinning it as it can cause shrinkage… It really is looking at the methods you use and changing one thing to cure your problem… Keep to the basics and try different things… It may not be too helpful… But dont give up and pre-pregs are not the answer for a poor technique if you have to use Out of autoclave pre-pregs because you dont have an Autoclave… In fact as good as you are unless you use the right pre-preg you may still get pinholes even if your technique is perfect… I have used numerous pre-pregs and only one works for me…
im just a self taught hack but one thing to help us out would be to explain the part you are making a little and the materials you are using.
for example I have a 12oz 0-90 with mat backing. the strands are spaced pretty far apart and its pretty tough to get enough resin on it to wet it out enough versus say a plain weave like a 10 oz or 6oz. the material is very fine and conforms very well to surfaces and takes very little to wet out.
mat soaks up resin and if you are having dry areas you might need more resin. you might try using a paint roller rather than a brush. I really like the white cigar type rollers, they hold a good amount of resin and the handle is about as easy to clean as can be.
there are also metal or plastic rollers that help pull the resin up and roll air out. I rarely use those as I hate the cleanup but they do work.
again if we had some more info this might be easier than writing endlessly about various situations. for the pinholes you can try laying a thin layer of mat and making sure its wet out completely. letting that kick and then continuing. you can also use gelcoat to make a nice surface and layup over that once it kicks.
hope this helps and didnt put you to sleep:D
Have you tried putting down a really light layer of 1 ounce woven fiberglass first? This will turn invisible over carbon.
When you say wet lay are you talking about an open moulding or wet lay then vac bag?
I am able to get pin hole and void free lay ups from wet lay/vac bagged composites every day with woven clothes (ie Carbon fibre and Kevlar) it just takes time and patience!
This is one of those issues that can be challenging to resolve. It might help to do some practicing on a piece of glass. There are two parts to think about: 1) your application (resin and fiber) process, 2) the bagging process.
Do a layup on the glass without vacuum bagging and see if you can get a pinhole free surface. It can be helpful to turn the glass over so you can see any voids while your doing the layup. Let the layup cure, peel it off, and see what it looks like. If you have pinholes then you know that you need to refine your resin and fiber application.
Once you can do the layup pinhole free without vacuum then try and do it with adding the vacuum bagging. If you start to get pinholes then you need to refine the bagging system. Vacuum bagging can often cause pinhole problems that are not application issues. The breather/bleeder, perf-ply, and resin gel-time can all effect pinholes.
If you are willing to do some testing and post your results of test layups then I’ll happily walk through the process with you. We just need to figure out the problem first. 
It is much easier to make the parts by infusion. For pinhole free ( and I still say it is not possible in wet layup) parts you will need years if experiance and a lot of trials and will produce a lot trash.
By infusion you may need 5 parts to get a perfect result if you just follow some rules.
And the equipment is the same price for wet bagging than for infusion. So why going on with wet layup?
I can often do a wet layup in less time than I can get an infusion prepped. Hollow molded parts can be a real pain to infuse with co-cured seams in one shot. Learning to do a wet layup has its place.
You can also make two shells and bond them together, most tomes nicer and easier than wet layup with blind seam.
And if you have to bag you are not faster when it should look nice. Also you can not make that nice cuts. And most times you will habe a voin, bubble or ponhole somewhere.
Sometimes you need wet layup for repairing or moulds. But I will never use it again for parts.
The problem is that people which work for a long time with another process do not like other processes, but if you will start you should try them all and make a descission. And most people will choose infusion.
But that is just my oppinion.
I am yet to do any infusion but I have done a little wet lay… Been doing wet lay for about 2 years. I dont just make composites for a living I also build bikes… So I dont make parts every day. But I dont have a problem now with Pinholes and the issues I had and solving them have helped me with working with Pre-preg too as you still need to understand how air is removed from a part being made.
Here is on of my parts which was wet laid and I am happy with the results… These would have been a lot quicker to make this way than being set up for infusion… But each technique has its place and I would say you need to understand the basics for all of them… I have seen infusion parts that are full of pin holes too and one company near me does every part in wet lay without vacuum bagging them and they look perfect.
This was wet lay polyester resin using Vacuum. This is as it came out of the mould and it couldnt be simpler…
I can not see anything on these pictures. But most times people have a different point of view what is a perfect part.
Til now I found pinholes or voids in every wet layup part people showed me. When I showed them to the people they say things like: That are only a few small ones, that are not really pinholes. That is a very good part.
Or they have clearcoated them. And I beat the man who build all the Mosler cars. He said he will be faster and produce a lighter part. He loosed in both;) I have been faster and my part was lighter.
He still makes some wet layups, and he is very skilled, but he also said that if someone would have shown him how to make a perfect infusion his life would have been much easier! He said he never popped out such perfect parts. He also said that the infused parts have these nice ceramic sound when you knock on them instead of the plastic sound of a wet layup part.
I do not want to say wet layup is useless, but it is mich easier to get perfect results than with a wet layup.
Those parts are flawless. Pinholes happen in every technique from time to time and to be honest the worst one for me is out of autoclave pre-preg unless I am using VTF261. But it all varies from one mould to another as each lay up can be different. I know with some parts I would be better doing infusion. Other I need to use pre-preg.
Hi, which rules are you suggesting i follow?
thanks.
I’m making a mirror cover and i’m using the following:
2x2 twill (2 layers)
SP115 resin system with fast hardener (laminating resin)
envelope bagging
I haven’t done any proper carbon fibre parts yet, but what I have found in doing samples and working with other woven fabrics are these few guidelines:
[ul]
[li]If the final part has any holes/voids/dry areas, the layup was rushed. (Don’t rush it on the re-do!)[/li][li]There are no shortcuts - the cloth must be fully wet out, this takes time and patience. Simple as that. (Actually this is true for everything, whether it’s woven fabrics of just basic CSM.)[/li][li]Use a heat gun on the surface layer of epoxy to remove air bubbles. (If you are not using gelcoat.)[/li][/ul]
If I had to recommend one rule, it would be “don’t rush”. Basically that’s all it comes down to. If your part ends up with dry spots or pinholes & voids, you’ve just got to make a note to work slower next time and be 100% sure that everything is wet out fully and you don’t leave any bridging in the process of working the resin into the fabric.
When I bought my first bit of carbon fibre I did a few samples using CF and got zero bubbles/voids/pinholes etc. I am 100% wet layup at the moment, I’m only doing this at a hobby level and don’t have a budget for any vacuum pumps etc. I tried using a glass veil on the surface, but there was no visible difference between the samples that just had CF laid straight down. The process went like this:
[ol]
[li]Brush epoxy resin onto the mould[/li][li]Use a heat gun to disperse air bubbles (not too hot, but some heat can be good to help this surface layer of epoxy tack off)[/li][li]Place the first layer of CF onto the mould (being careful with placement, because once it touches it will not move)[/li][li]Work the fabric into the epoxy surface layer (I prefer a brush for this, not using the tip, but holding the brush on an angle to get a larger surface area and use a smooth pushing kind of motion)[/li][li]Once the CF has been fully pressed into the mould, only then do I put epoxy onto my brush and start to wet out the job[/li][li]Don’t just slap on resin in great quantity, I only use enough to wet out the fabric.[/li][li]Repeat for each additional layer - work the fabric down, then wet it out.[/li][/ol]
If you’re going for a visible carbon look, I think an important part is to let the surface layer of epoxy tack up a bit before putting any fabric down. It helps hold the fabric as soon as it touches down, any movement could introduce air I suppose?
Well that’s what worked for me on a few smaller test pieces at least. Hope that gives you some ideas.
I keep a heat gun ready and apply heat right after applying the resin and continue to apply heat steadily around the entire area until i am satisfied that all air bubbles are popped.
Hi Mugget would you be kind enough to share a few close up pics of your work.