Hello everyone, my tecnique is RFI (resin film infusion) a Mix of prepeg and infusion, using a solid epoxy resin film wich melt and became liquid with the rise of temperature.
For the moment my problem are pinholes, i think to solve them making smoothier molds and slowing down the impregnation time. What do you think? someone knows this process?
what kind of ramp rate do you use for this technique? I would think this process would have pinhole issues more so than either prepreg or infusion.
What is your laminate stack also?
I’ve tried everything on temps excluding slowing down the first ramp to get impregnation temp of 70C. Because the controller of my oven didn’t admitted to program it. Now i’m without laboratory and I need to equip the new one. I’ll surelly get a good one with every kind of settings. So for the moment all I can do is working on theory 
Another idea that i’d like to try is using a countermould. Any idea? Link?
Is the film already on the cloth? or do you apply it on the cloth yourself?
Temperature is one point, but what about the pressure?
No, the film is separated from the cloth, I’ve tried:
- mould > resin >carbon > resin > carbon…
- mould > carbon > resin > carbon > resin…
I think that the right lamination is
- mould > carbon > carbon > resin > carbon…
I’ve tried a lot of combination of plies : 1x carbon 200g/sm, 2x carbon 200g, 3x carbon 200g, 1x csrbon 200g + carbon 400g…
I think that i have to do it more “scientifically” changing just 1 thing every time, but in the old laboratory i had a lot of issues…
(Sorry for my bad english)
The stack and order is important. It works under the same principal as infusion. Basically the resin will flow, and as it flows any remaining air would be flushed out to the vacuum. Thats why typically you would want dry fabric against the mould surface, gives a good air pathway. If your air pathway is closed then your air is trapped. In your case, you are putting the resin film down first against the mould surface. This traps air between the surface and the resin film. Its a bad start. additionally, same as infusion, you must have good vacuum integrity. I would suggest same standards as infusion; for example 0mbar drop a the part in 10 minutes. Lastly what is your consumable stack? Are you using a perforated release film, or no perforated film? What type of breather? One more question; how long are you leaving it under vacuum before curing? and at what temperature?
As hojo said, stacking sequence is important, so yes, dry carbon against the mould, then film behind it. Some people do all dry carbon then all film but this is thickness dependent and also bleed stack dependent. I tend to put one dry layer, one film, one dry, one film, etc for parts of a few mm thick
really thanks for sharing your experiences with me.
when I tried with dry fabric directly on the mould i haven’t noticed big changes, but now I think that the problem was the surface of the mould that wasn’t really smooth.
have you tried to do a “prepeg”? putting the film on the fabric and let it melt at 50°C? i think that this could trap some air, right? I used this tecnique because was very easy to handle the “prepegged” fabric
hojo, i can’t undestand this “for example 0mbar drop a the part in 10 minutes” I usually opened the vacuum tap helping the bag to don’t bridge with my hand or with soft plastic tools, is it wrong? so the pressure drop was very quick, is it a problem?
I check for 0 mbar at room temperature, then i setted the oven temperature to 75°, checking with an external thermometer the laminated temperature, the ramp time was usally 30 minutes, but this is quicker than what the supplier said to me (1°C/3min) this is another mistake, right?
I’ve tried to stay at 70-75°C for any kind of time but this doesn’t change anything
my consumable stack is: (laminated) > peel ply (optional) > perforated film > breather
I hate the breather (and the peelply) beacause very often they bridge… And I have to do a lot of work to push down and press them when the bag is closed and sometimes this doesn’t work… any suggestion? I was thinking to intensifiers, but if i have to spend a lot of time on them why not a complete counter-mould? Maybe a soft sand bag pressed directly on the outside of the vacuum bag? or an alluminium microsphere bag that will be easier to heat and will expand with the rise of temperature…
Try a lightweight glass film as surface film (50-75 gram/m2). Try to extend the first layer beyond the rest of the stack, that will help extracting the air.
Sorry but I don’t understand completely what you said, you mean putting a film directly on the mold, like a “release agent”? won’t it wrinkle?
Your technique of slowly applying vacuum and press in corners is correct. My point is that before you start the curing process you should confirm the vacuum integrity (leak rate, and pressure level) is good for the process. If you have a small leak, this will likely cause a poor surface in the part. You can try double bagging the part to increase your integrity, and lower the risk. What RIF system are you using? do you have TDS? You may find using a non perforated release film, with some try dry glass toes going to the breather to be a better technique.
sorry hojo, what means “Rif System”? and TDS? sorry but I don’t know what those acronyms means… 
I may have understood what hojo said about the unperfored film: to put it behind the breather, before the vacuum bag, to let the stack slip into the mold, to avoid bridging, right?
Moreover I saw that with Zyvax semipermanent full treatment, I had better results in terms of surface smooth, so I’ll surely use this in the new laboratory. Wax like “Ferro Mirror Coat” ar not good for me
hojo, I check my vacuum integrity looking at the manomether I don’t like to pull out the mould from the oven, there is any kind of instrument to check for micro leak?
I’ll surely try double bagging
really thanks to everyone of you, you are helping me a lot
Company’s like cytec, gurit, etc, sell “surface films”
It is basically what you are trying.
They come in a roll, where there is a resin film sandwiched in between a lightweight glass layer, and a thicker (300 gram/m2) carbon layer. It is one of the easiest materials to get a pinhole free result with.
So if I where you, I would try the same. Sandwich the film in between glass and carbon. The glass will become transparent, and will have no pinholes. because of the air extraction (important with dry fibres) above and beneath the film, pinholes in the carbon will get very rare, if air will become trapped. So try to get this layer in contact with the breather, by extending it 1 to 3 cm around the whole perimeter of the part. If necessary, on complex shapes for instance, trow in some glassfiber tows behind the first layer to the outside of the part, that will help too.
Then the trick is that there is enough resin in there for the whole stack (calculate), and a high vacuum, possibly around 97-98 percent.
If that gives a desired surface quality, you could do a test with out the glass layer, as the glass will be not as clear (although most won’t notice the glass layer at all)
Sorry, meant RFI (resin film infusion)… I suggest you use an absolute pressure gauge such as the GDH200-14. You should check the pressure level and leak rate before putting the part in the oven. You would want a pressure level at your part to be less than 20mbars, and a leak rate over 10 minutes to be zero would be ideal.
My RFI system is from a company called 5M
I’ll surely buy something like GHD200-14, thank you!
I’ve looked at the cytec’s and gurit’s websites, i think that cytec SURFACEMASTER will be a nice solution, what do you think?
I think you should control the variable in your process first, then make changes to the process to achieve the results you are looking for. You can contact Vacmobiles for the GDH200-14.