By N2CFRI - 9/9/2020 3:17:02 AM
Hey everyone,
This is my first post but I thought it would be a proper time to join since I actually need some specific advice. I just attempted my first resin infusion from a mold I made a few weeks ago and everything was perfect (to me, but I’m anxiously waiting to be corrected haha) until I actually started my resin flow. I just wasted a whole bunch of resin and carbon fiber but not in an overly irresponsible way, I just think I lacked the experience to know what specific materials to use for my application. I think my bagging film is the problem but I’m open to ALL suggestions/burns/comments/laughs, whatever. I want to learn and perfect this, I can take the criticism. I have no idea what I’m doing haha. I’ve read many posts on here and all the write ups and videos about infusion and issues related for days on end before attempting this which I thought I followed closely and I’m sorry if my lack of experience is going to annoy anyone but I didn’t find any posts from anyone with as severe of an issue with bagging film as I just had. Anyway.. Here was my stack up.
-6-8 layers of partall paste 2 wax
-Sprayed 3-4 layers of evercoat mold release PVA
-4 layers of 3K 2X2 twill, about 1mm total dry thickness
-1 layer of green nylon mesh peel ply
-1 layer of Composite Envisions red Flex Flow media
-Stretchlon 200 bagging film. (As you can see the part/mold is deep with several tight radius’s and depth changes, so I wanted to ensure a tight fit with no bridging and I didn’t plan on baking it which is why I chose this film from everything I looked at.. this might have been the death of me)
So long story short I vacuumed down to about 27 in/Hg according to the gauge on my catch pot (my air converter pump thing that I bought is only rated for 26 in/Hg so I figured that was a good start). I valved off the bag setup and much to my surprise for about 50-60 minutes the bag held completely. I mean the analog gauge didn’t move at ALL. I presumably had zero leaks. I was quite proud of myself for a first timer. I for sure thought I was going to have a tornado of air from somewhere finding its way in but nope, held like a champ. That is, dry, at least. Problems started shortly after that when I started the infusion..
After the hour of being under vacuum I slowly re-introduced the pump to the circuit and unclamped the feed line to my freshly mixed/degassed resin cup (let it sit for 10 mins). The flow was decent as it entered the mold. It appeared the resin wanted to flow more in the left right direction but I guess that was because of how I positioned my flow media. (Not sure if there’s a way to get a more omnidirectional flow through the part? That wasn’t my main problem but I’m curious if anyone has any tips on that.) I had the resin flowing about 3/4”-1” a minute.
Here comes trouble.. As soon as about the middle third of the mold was resin saturated, POP.. hole blew open in the bagging film right in one of the round bottom edges, lost almost all vac. Grabbed my tape, sealed it off.. 2 seconds later.. POP.. another hole blew in the bag, other side, completely unrelated.. sealed that one off.. POP... POP.. POP... FML
And that’s how the next hour of my life went. Pops and tape and more pops and more tape. This damn bag blew holes in itself everywhere on the mold. Even in places that had no sharp material like along the smooth edges of the spiral tube up on the flange. Most of the blow through’s were around the radius’s and tight turns, but some just blew open in random flat spots as well. If you were walking near my garage today you would have thought a person with Tourette’s syndrome was making popcorn because there were that many pops and that many obscenities being shouted at the same time. It seemed that as soon as I sealed one off and the vacuum approached 25-26 in/Hg another hole would blow somewhere.
About 30-45 minutes into playing wack a mole and going through more than half a roll of tacky tape I waived the white flag. I couldn’t seal holes fast enough before another blew and then some of the holes I had sealed previously started to leak again. It seemed like the grey tacky tape wasn’t even sticking to the outside of the bagging film that well anymore. Maybe it was just all my sweat pouring off my face from the stress and anxiety as I watched $100 of carbon fiber and resin being thrown into the trash. I hadn’t even been paying attention to the resin flow anymore because I was panicking so much trying to seal the bag.. With about 75%-80% of the part saturated the resin flow had slowed so much because of the constant air leaks I figured at this point I should just save what little tacky tape I had left for the next run. I clamped off the resin, killed the vacuum, and went to go cry in the corner for a few hours.. I’m just kidding. I went to work. I was crying inside though.
So It feels to me like the bagging film just failed. Or I failed and used it improperly. OR I failed by using the wrong bagging film. Now it’s everyone’s turn to roast my methods. I’m hoping someone here can shed light on what caused the bag to blow me. The stretch-o-matic 200 or whatever it’s called is supposed to stretch quite a bit and I didn’t think I overdid it, but maybe I’m wrong. I even left a little extra slack before I sealed it down, but maybe not enough. Who knows. I thought I had everything down solid, but I was wrong.
Someone PLEASE help me decide how to approach this next. I already ordered another gallon of resin and some stretchlon 700 bag film because I read it’s much tougher and a little thicker than the 200, maybe that’s the key? I eagerly await all of your questions and instructions. Thanks in advance for helping me enter the wacky world of composites everyone.
PS I tried to upload an image of my mold but I couldn’t get it to work no matter what size I choose it just hangs on uploading forever. Doea anyone else have issues uploading from their camera roll?
|
By torstenker - 9/11/2020 7:46:13 AM
according so some documentation I found, all resin shrink after gelation between 2% and 5%, polyester is the worst.
This shinkage is due to the thermal expansion occuring when hardening and then cooling later on, once cured it should not shink anymore.
In a mould, the shrinkage is on the side not adhered to the mould surface but you will get a slight inprint which can be polished off
thats the reason big patches of polyester car body filler get stressed by that shrinking on curing and will crack on the smallest bump
Sometimes that shinkage is desired whem using poliester resins on infusion because they come easier out of the mould :-)
|
|