Terrible Surface finish-Please help!!c


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nebraskatrevor
nebraskatrevor
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I need some help, I just recieved my first order of prepreg and after playing with it for the last couple days I am horribly disappointed.  I have been working with other prepregs from another supplier and I have had pretty good success with conventional prepreg that is meant to be cured in an autoclave even though I have been using it in an out of autoclave process.  So far the first 5 things I have tried to make with easy preg have all been complete failures.  I am super frustrated because I spent a lot of money to buy a couple yards of the material and have it sent to the US and at this point I am feeling like it all needs to be thrown in the trashcan because it seems completely useless.  I will describe the setup that I am using and maybe someone can tell me what I might be doing wrong.  I will also attach some pictures of the problems I am having.  I have tried metal molds, composite molds with a gelcoat surface, cnc machined solid teflon molds, and tonight even a sheet of glass to see if I could get a good surface finish and so far all have failed miserably.  For my mold release I am using a chemical release called Freekote 700nc which has performed beautifully with the other prepregs I have used.  I am vacuum bagging with a flexible bagging material called stretchlon 200 and with a solid release film and a breather cloth.  I have used cure schedules all over the map from 180 deg F for ten hours up to 275 deg F for less than an hour and all have yielded similar results  The max amount of vac I am able to achieve here is about 26.5inches of mercury and that has proven to be acceptable for the other prepreg I have used but I am wondering if it is not enough for the easy preg because I have read a couple of places that a near perfect vac level above 29 inches is necessary.  I leave the vac pump running throughout the process every time.  To top it all off I am not at all happy with how the cured fiber looks and  find it to be some of the most boring carbon fiber I have ever seen anywhere.  There seems to be such a lack of contrast of the alternating fibers that it almost doesn't even look like carbon fiber at all, I would hope that if I could get my surface finish issues resolved the appearance might also improve but I am skeptical that it will ever look as good as any of the other various  fabrics I have worked with.  For me the selling point of this prepreg was that it was great for making cosmetic parts and I am disappointed to say the least.  I appreciate any input that I can get and really hope that I am doing something wrong and that I can learn to love this easy preg!  Thanks for your help.

The first two pictures show a piece that I cured on glass,  It consists of one surfacing layers and two backing layers bagged up as  I have described above.  The last two pictures show some parts I have made with another brand of prepreg shown with the same piece molded on glass.  The skull and the outlet cover do have automotive clear coat on them and although I realize that it may not seem like a fair comparison I can tell you that the clear coat does not hide any flaws, but if anything tends to magnify them.
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nebraskatrevor
nebraskatrevor
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Thanks to all of the suggestions I have received here I am getting much closer to success with the easypreg.  I will attach 3 pictures below that show from left to right:

Left sample= easy preg cured on glass sheet with 3 coats of 2K clear coat sanded with a block in between coats then polished with 3M polish, then coated with 3 coats of Carnauba wax

Center sample= easy preg cured on glass with a ramped cure consisting of 2.5 hrs at 65 deg C followed by an hour at 85 deg C followed by half an hour at 110 deg C (the last part at 110 was only necessary for the other sample to the right of another material) then finished with one coat of carnauba wax which can be seen as white specks in just a few pinholes.

Right sample = 2 layers of another fabric that I have used and that I have been basing some of my previous comparisons on finished only with one coat of carnauba wax.

All in all the improvements I have been able to make in less than  a week are very pleasing to me. Next I need to try achieving the same results in actual mold rather than just on a flat sheet of glass.  I also need to investigate buying a ramping capable temp controller for my oven so that I can avoid the boring and inaccurate method I have been using, me  knob and watching the clock!  Thanks again for all of the help I have recieved and I will continue with a picture in the future, hopefully of a more complex part. 
ehttp://www.talkcomposites.com/Uploads/Images/411d8658-0b43-46c6-ad34-18c7.jpghttp://www.talkcomposites.com/Uploads/Images/17e678a3-9e98-439f-be58-4046.jpghttp://www.talkcomposites.com/Uploads/Images/82d4d0a8-5e0d-41b0-80e2-5c2d.jpg
Edited 12 Years Ago by nebraskatrevor
Matthieu Libeert
Matthieu Libeert
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Thanks nebraskatrevor for the updates, I ve been following the entire post because I'll try prepreg for a project soon and found a lot of usefull information on here! keep us updated when parts come out of a mould Wink

Matthieu Libeert
Founder MAT2 Composites X Sports
website:
www.mat2composites.com




carboncactus
carboncactus
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Glad to see the improvements, trev.
Are you happier with the cosmetics of it? Clear coat and wax does make a big difference for depth and shine.
I think you'll find that hour at 110 would have been needed for the easypreg to cure.
What did you back the easypreg with?

http://www.talkcomposites.com/Uploads/Images/db628ad5-e0e7-47b9-873a-3d84.png
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nebraskatrevor - 12 Years Ago
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