I posted this over at Talk Composites. I know the demographic here is a bit more pro, but hopefully a beginner might take something from it. I would have posted here aswel, but the limit is 10 images.
Read the thread. 3 things pop my mind:
What mould material did you use? Or what is its Tg?
Do you control the ramp/soak of the oven?
On pinholes: check for a product called “bouche pores” from Sicomin / Map Yachting. It is a black PU putty (1 component), which you can spread over the pinholes with a spreader. After half an hour cure, you can sand the residue off with a scotchbrite. Saves you some painting and sanding.
I presume VTF is the Advanced Composites product, right? There are more good prepreg manufacturers (but also lesser quality ones)
Mould was GC206 gel (130) and optimould (100). Ramp was from ambient to 90 with a dwell at 60.
Yea I’ve emailed Map Yatching about Bouches Pores, they told me to get it from the UK distributor, Matrix composites. Rang them, they said they have been trying to get it for ages but Map Yatching just won’t send it… Who knows? The putty I used there was a one component stopper from Mipa, dries in minutes.
Yea VTF261 from Umeco. Normally with this prepreg, I lay it down without paying much attention and parts come out fine. The first tray was Hexcel M52. It’s a 120 cure, but my rep said it’ll cure at 85 for 10 hours. The second one is an Italian prepreg from “Impregnatex Compositi” model IMP530. The rep that sent me this sample said a local college uses it to make simple OOA bits for Augusta Westland, a local helicopter manufacturer. He recomended 10 hours at 80C.
I don’t think it was anything to do with ramps. It was just a bridge. But the second one I made, I didn’t use breather and it came out flawless:
I believe it was the lack of breather that helped, because both prepregs were VERY similar physically, as you can see in the photos, they both laid down identically and were equally tacky. So I’m going to stop using breather from now on different parts and see if it helps.
Thanks for your answers. Makes sense.
Indeed MAP can be difficult at times, but as they are French, and our head office is in the French part of Belgium, that helps a lot.
Always interesting to see people’s experiments and processes.
I noticed your oven - doesn’t it matter if your part is laid flat? There’s no risk of it deforming while leaning like that in the oven? Obviously you didn’t have a problem… because the Tg of your materials was higher than the oven temp? Is it usually “good practice” to make sure the part is laid flat/supported?
Yea, except its an experiment almost every time!
I’ve never had an issue that was related to orientation.
Hi Cactus, what release system are you using and for how long did you cure the part.
thanks
Im using Chemlease 41-90. Parts were cured between 85-90 (oven regulates itselft and can vary) for 10 hours.
I can not get the link for the paper to work, why do you say no breather? Breather allows VOCs to escape through the perf release film. I’m guessing you got a good surface finish without the breather. Was the release film perforated? The reasoning is, if there is any sealing of the film/bagging on the part surface, air can not escape, and then full vacuum pressure will not be pushing down on the part. Even simple peel ply AS a breather is a good idea.
Can you explain your methods and reasoning a bit more on that?
Yea, perfect finish without breather on the laminate side. Even on the main flat area, with breather it had a pin hole here and there. Without breather it was flawless. Release film was non perforated. I did however use glass tows on the edges, but I always do this.
Sorry, this link works:
http://digitool.library.mcgill.ca/thesisfile97254.pdf
The guy used breather, just not in the corners. I skipped breather all together. I remembered when I first started, I forgot to use breather and the part came out fine. Quite a complex part too.
I’m cooking another one today without breather.
For the logo you neec to use fine line
I’ve git fine line, but I quite like the distorted look.