Infusion issues

General Composites Discussions Composites Talk
#1

Even though my part came out fine I had a few issues that popped up during the infusion… maybe you guys might have some ideas on what to do in some of these cases?

  1. forgot the MTI hose changed so i had issues until i remembered to vac the bag first from another port. This becomes an issue later on…

  2. The draw on the resin was fast then slowed down a bunch to the point to where i was worried that the resin would cure before finishing. the resin is about 350cps. it took about 50min to infuse the whole thing. what would cause this? Only glue i used was the airtac 2 which is meant for infusion.

  3. towards the end, the pump started to act up and let some air in (was low on oil). i fixed it but then the mti hose wouldn’t pull enough air out of the bag to pull everything back down. i had to put another hole in the bag with a separate tube to remove all of the air.

i think i have some print through but i am not quite sure what that looks like… any one have pics? I attached what i think is print through on my part

The part also came out pretty dull (like all of my parts). do you guys generally clear coat afterwards or do an IMC with 2k? I am a little hesitant to spray a clear since i have never done it and the random pin holes also might cause issues.

also can you guys suggest a black putty for filling the pin holes?

#2

Not a bad result considering the issues!

The first one I think is just one of the drawbacks of MTI hose. It’s a bit of a shame it can’t flow faster, but I guess it is designed to be used in a perfect situation and in a perfectly sealed bag it shouldn’t need to flow air very fast once it has been pulled down. Obviously it’s just better that nothing goes wrong and you don’t need to rely on it, so I think next time just make sure your pump will be ok.

As for the infusion speed, how thick is the laminate? Thicker laminates will flow quite quickly at the start but get exponentially slower as they go along because the resin still has to flow through the stack at the start. However, your laminate doesn’t look thick enough to cause that issue, so it’s a bit of a strange one. Your resin viscosity is fine (assuming you were at room temp and not infusing cold?), so that won’t be the issue. What vac bag is that? It looks quite thin, so could have stretched into your mesh and blocked it up somewhat like Strechlon does, this will slow things very dramatically.

I prefer to use an IMC, but this makes it essential that everything goes well because it will be impossible or at least a hell of a lot of work to repair any issues. Post-coating is also fine if you are prepared for the extra finishing work. Pin holes can be filled with any polyester body filler with a bit of black pigment in it. Once cleared, these will be virtually invisible.

#3

Yeah the layup is thin. 2 layers of 2x2 twill, 2 layer of uni at 45 and 2 layer of triaxial. As for temperature, we were in the garage, probably 55deg which is a bit on the cold side but they may have save my butt when the vacuum stared acting up. The vacuum bag is stretchelon 800 which a lot suggest, so that’s why I bought it, but it’s the first time I have used it.

The only polyester filler I have used or come across off the shelf is bondo glazing spot putty but that is red and I wouldnt think it could be dyed. I wasnt sure if someone just made a black one or not since I can’t find it.

Any thoughts on what could be causing that weird surface finish? Are the spots caused by the spray glue?

#4

I’m almost certain the Strechlon would be your flow issue. Strechlon really isn’t suitable for infusion, I don’t know why so many people recommend it.

I’m sure you can get regular polyester body filler where you are, it’s probably the most widely available form of resin there is! It’s normally a cream, pink or grey colour and these can always be tinted black very easily.

The spots are very likely caused by the spray adhesive, that’s what it does. You have to go very very very light with it, and even then you will see it in the light. An IMC would fix this, you don’t see the effects of spray adhesive when it is behind an IMC.

#5

Ok. Do you have a suggestion for bagging material that i can try?

The last time i tried an IMC (german advance), it went really really bad. :eek:

I foud this but how do you die it?
http://www.amazon.com/3M-05095-Acryl-White-Putty-Tube/dp/B003P6I5KS

#6

You don’t want that, that’s acrylic. You need a polyester based 2-component body filler. Such as:

http://solutions.3m.com.au/wps/portal/3M/en_AU/AU_AAD/Home/Solutions/Filler/?PC_Z7_RJH9U5230OLLB0II6IU3PQ1GV6000000_assetId=1319243120078&MDR=true

Or this:

http://www.amazon.com/Evercoat-112-Premium-Lightweight-Filler/dp/B000P6URMA

Then you want a polyester pigment to colour it, like this:

http://www.easycomposites.co.uk/#!/resin-gel-silicone-adhesive/pigments-and-dyes/polyester-colour-pigment/black-polyester-colour-pigment.html

Any general fibreglass supply store is likely to have the pigment.

As for vacuum bag, you you can use virtually anything except Strechlon. I use Cytec Vac-Film450 myself, which is excellent. Have also used Airtech Wrightlon which is a bit thicker and stiffer, so can be harder to use but is also less likely to puncture.

#7

Great and thanks! I will look those up probably in a quart size.
I am going to assume this is the same
http://www.summitracing.com/parts/tes-05800?seid=srese1&gclid=CM-q8bzgmswCFQuPaQodqDAK5Q

i can get this pigment online
http://compositeenvisions.com/pigment-black-667.html

Funny I had the Wrightlon bagging material but i ran out. Based on everyone’s suggestion, i went to the stretchelon 800… i will go back.

Shockingly here in denver, which is a pretty big city, we have one fiberglass supply store and it isnt very great for composite products. They do plastics and composites.

#8

Same issue again on another infusion! I switch bagging material and no change. Everything started flowing fine then slowed down a lot. This time i think the part is garbage since the resin stared to cure before the whole part was infused. Any other thoughts what might be going on?

the only other thing i could think of is that the MTI hose is causing the issue somehow.

#9

The MTI hose has no effect if you are at full vacuum. The resin is pushed in, not sucked in.

I think you will have to give us the full details on the materials you are using. Fibre weights, resin, brands etc etc. There’s something not right in your set up.

#10

Ok here is my exact set up (of the last infusion).

Wax and pva
Light Airtact when need
2 layer of 2x2 twill 5.7oz
3 layers of triaxial (similar to this i think https://www.rockwestcomposites.com/materials-tools/fabrics-pre-pregs-tow/13012-d)

Airtech Bleeder Lease B Coated Peel Ply
Airtech Greenflow 75 Resin Flow Medium
Airtech Wrightlon® WL6400 Nylon Vacuum Bagging Film
MTI hose

Max CLR 1618 resin

This set up has been used before and the only thing that has changed is the triaxial (usein place of 3k and fiberglass) and MTI hose (which MTI changed)

what i don’t get is why is flows fast then slows down to a crawl.

#11

i think the 12k triaxial is causing the problems. I will lay up another one only using the 3k. Maybe some fiberglass too

#12

Your resins viscosity is measured at @75f, the 55f shop temperature will make the resin thick as snot, well above 1000 centipoise. You have a temperature issue, not a setup problem.

#13

It is a temperature problem as long as your vacuum is perfect and the setup tight!
The MTI hose is the same, what sometimes can be is that the membrane is more or less permeable, but the only thing it will change is the evacuuation time, nothing else.

Post more pictures from your results, that helps to find your problem. But I can tell you in 95% it is “only” a vacuum problem.

#14

these new parts were infused at 70°. with the resin flowing just fine then slowing to a crawl i doubt it is a temp issue. the liquid in the cup was very fluid when it started to slow down.

here are the pics of half of the part and the setup.

#15

The problem was a leak in your setup. You can see that from the air inclusions at the backside and that the fibres are dry.
The thing is, if you use regular spiral you would get a full impregnated part in this case because the spiral sucks theleaked air much faster. But if your setup is tight what it should be you will get the much better result with MTI. MTI is not a “Miracle Maker”. It will make life easier and give you a much better part quality, BUT it is absolute nessecary that your setup is tight! And it has to be always tight if you make an infusion! Without a digital gauge you can also not make a leak test, analogue gauges are not preciese enough.

#16

Again, i think the focus on the hose is off. i still think the 12k is the issue. I don’t see how, even with a leak, that the resin would flow quickly then just exponentially slow down.

Yeah it didn’t have any leaks and i have definitely had parts with small leaks that infused way better.

probably what you are seeing is where i got pissed off and pulled the vacuum once the resin stared to cure.

I had a colleagues do a similar set up and he got the same results.

Let me know if i am wrong here since i plan on doing anther layup today or tomorrow (deciding if i want to try the 12k again or not) but What might cause this is a thick laminate. As the resin flows initially, it may flow quickly but as you try to pull more through, it has to overcome the initial resin first.

on the reverse, can you explain how the resin flow is related to the vacuum leak?

#17

Pf course the resin slows down exponentially. The inlet has always the same diameter, but the surface where the resin is spread becomes exponetially bigger. You can compensate that by a bigger resin inlet wich you regulate down at the beginning of the infusion.
If you have a leak there is air getting in wich means the pressure difference is smaller what slows the infusion also down.
Depending on some variables it can slow your infusion partially down. But I am quite sure it is not the fabric. I have infused panels of 1 by 1.5m with 60 Layers of 460g/m2 12k fabric without any issues.

#18

To clarify the exponential, i went from an initial rate of 1" every 5min to 1/4 every 10-15min.
I am going to just have to try it again and see what happens. I just hate burning through the 12k tri since it is super expensive.

#19

in the beginning you should have 10" per minute or something like that! 1" in 5min at the beginning is way to slow!

#20

Put your resin for sale where you bought it, eBay… :slight_smile: lol,it actually probley is alright…

Are you still using the strechlon 800 or did you go back to some vesion oftwrightlon? Thickness of film? Thin strechy film will pinch off resin flow channels. I’m thinking you are closing off the resin feed line with the bagging film, wrap with either peel ply or even better, infusion mesh. That 12k cloth , known as “quiso” weave from manufacter A&P technology, should flow like mad…