Resin richness and bag wrinkles

General Composites Discussions Composites Talk
#1

I am currently working for my company at a different facility than normal. Both facilities make similar part families with pretty much the same glass prepreg. The parts being made are non-structural shrouds or side panels for example. Again the parts are cosmetic and the toolside is the showside. At my home facility we perform vacuum debulks about every three plies and the final bags are smoothed out over the part and peel ply, pleats properly placed. The parts come out looking nice toolside and bagside. Here at the other facility they don’t debag (most parts are only 4 plies) selectively place peel ply in bond and bracket areas and they don’t plan pleat layout, but they pleat plenty and have bagging to move around. They also don’t smooth out the wrinkles over the part. I have only been out of school for 8 months or so, but everything I have been taught/shown is smooth the bag.

Parts at home facility look great on both sides.

Parts at away facility have a fine toolside but the bagside is veiny looking and any radii have resin richness from bridging.

Is this bad on a cosmetic part? Is my home facility wasting production time sweating the details?

Or should I be training the away facility workers do it the way I have been taught and trained to do?

#2

Debulking after 3 plies is standard for making aircraft parts. Sounds like your home facility is following strict guidlines regardless of the purpose of the finished parts.

They are only wasting money if having a poor non-show side wont effect their sales of the product.

#3

So, I shouldn’t worry about resin rich radii and things like that?

The home facility does work to very strict standards, the away facility not so much but their parts are for another OEM.

I’m just thinking about the overall part quality being affected by these “easier” practices. But if no harm, no foul.

#4

Chances are your home facility is actually obeying the blue prints they were given. Which normally are accompanied by a layup schedule.

Good chance that your away office is only obeying the parts of the layup schedule that are convenient for them.

Your home office is making much higher quality parts (from the sounds of it).

#5

Sounds like the “away” place has bagging issues.
Is the bag actually against the last ply? This would cause the veins, but it could also be from release film with wrinkles, which is difficult to avoid. Peel ply fixes those issues.
Are the corners resin rich on the tool side, or is it the bag side? If they have plenty of bag, then it’s most likely they just aren’t working it into the corners. Less likely but also possible, if there is no breather being used there’s a good chance of resin richness in tight areas.
What shop is this and what type of parts are being made? Got pics?
I do some consulting work for a large aerospace OEM outside of Spokane.

As an aside, I can’t imagine how flimsy the FG pieces must be with just 4 plies!

#6

I’ll work on getting some pictures, I didn’t bring my camera usb cable with me and these old work laptops don’t have cards readers so I need to wait until I get to the hotel and email them from my netbook.

I should clarify that the parts are not huge, and their design helps to keep them from deforming much. Also some parts do contain core, 0.125" to 0.313" thick.

The toolside radius doesn’t have the resin richness its mainly the bagside. Sometimes the toolside is slightly resin starved, no dry fibers, but its not a smooth surface all the time.

Most layups are are bagged with perforated release film (1 inch spacing), a layer of Breather/Bleeder, and then bagging. Certain parts get peel ply in hardware mounting and bonding areas.

I’m currently working in Brazil (4 hours ahead of Pacific Std.) and it seems unless I have a break through reason to change things they are pretty resistant. Maybe I’ll just focus on the resin richness in the radii and not worry much about the bagging veins since yes it is correctable with peel ply. I’ll work with them on preventing bridging.

Another thing I have noticed down here, static plans, WO’s, layup schedules, and basically any specs are kind of hard to come by or are understood as “suggestions.” Maybe that is why things are more affordable here?

Again I’ll work on getting pictures. But just to clarify for me, does smoothing the bag over the part lead to more uniform compaction because the forces are spread evenly instead of being interupted by bag wrinkles?

#7

No time to go through the whole post right now.

But to answer the last question, no. Doesn’t work that way.

#8

OK, thank you for clarifying. I am taking some pictures today for you.

#9

Here are some pictures of bags and after debag. Some are extreme cases.

#10

I have seen and done that. I tried everything in the world to get sharp corners and compact areas to not bridge. From tons of extra release, bagging, release film wrapped tacky tape, and caul plates. I just never figured it out. We are talking a 1.5" wide U channel, with 1" mounting blocks imbedded…

Those parts seem a bit bigger. Are you sure the prepreg itself is PERFECTLY imbedded into the mold radii? If the prepreg is bridging, then no amount of pleats will help that. If you have too, split the fabric in the corners to take off contour stresses.
Also, what kind of prepreg are you using? If it is not Net-Resin, where there is the exact amount of resin in the fabric, you might have the pooling of the resin in the corners, and need to somehow get more bleeder down there to suck out the excess resin.
Maybe layer the perf. release film, add some bleeder in the corners, and add more release on the outside, THEN cover the part in your bleeder/breather.

#11

ps: wrinkles, yes, are from direct bag/release surface contact. peel ply gets rid of that, but of course, leaves the rough surface.

also, you might want to try cycle debulking. Debulk, and work fabric/bagging into the corners. Release vacuum, and debulk again, maybe 3-6 times. It will help squish down the material, and shift it in position.

#12

It is a Net Resin system, JD Lincoln L530-7781. I went and worked with production today in the layup room, and it quickly became apparent that they are not working the bagging materials into the corners very well. I went over a couple parts after they pulled vacuum and the bagging was definitely hovering over the corner. I did release a little vacuum and worked the materials around, then pulled vacuum, working the materials while the air was being removed. The corners looked better, but I will see after they come out of the oven. Thanks for the cycle debulk tip I will test that out.

#13

Ok, i’ll be the one to ask the dumb question: What is “debulking”?

#14

Debulking helps to remove voids and consolidate a laminate. We normally (at “home” facility) perform debulking after every three plies by using a temporary vacuum bag to consolidate the plies. Depending on what you need to do you can debulk using regulated vacuum or full vacuum for however long you see fit. And usually try for three-five minutes. If I’m not being clear I can clarify.

#15

That makes sense. Each debulking cycle then consumes a bag and sealant tape only, correct?

#16

with prepreg you can reuse the bag for debulking multiple times by taking strips of bagging film and lightly adhering them to the sealant tape and rolling your bag up. usely for finale bag you should use a new bag to be safe. you can also reuse the bag with wetlay but it can get messy.

#17

We use the same bag and cheaper sealant tape for all the debulk cycles. Then the final bag gets new bagging and the good sealant tape. Like the previous post stated you can just roll the temporary bag out of the way until the next cycle. And this would be very messy with a wet layup. :eek:

#18

yeah, I have used the same bag at least 10 times in the past, just adding some tacky tape where needed. We also cycle debulk VARTM runs, since it too, will help shift the fabric and nest better. It’s not just for Prepreg.

wooo…speaking of prepreg, gotta run a hotpress part! almost forgot

#19

yeah, from what you said about how you home shop adheres strictly to a good method, and the away shop just does whatever is quick and cheap…i’m sure most of your problems will be there, and in lack of training. Even if it’s the back of the part, if you have a resin rich area, it might have stress points at the edges of the resin pool, and lead to failure quicker.

#20

Sweet! Thank you Riff42, that is exactly what I’m looking for, more backup for why they need to improve their processes.