Carbon Fiber Perfect Finish

General Composites Discussions Composites Talk
#1

Hello, I have been testing panels using VARTM and most come out ok. Then one day I pulled a panel and to my surprise the carbon fiber looked simply amazing in comparison to other panels previously done.

So I have researched and read about it as I am somewhat new to composites but have really been doing my homework. The answers I have found seen to be its beautiful finish being purely based on resin content being more rich than previous panels.

I am looking for a way to achieve this in every panel I infuse. Here are a couple of pictures for example.

This panel is a single layer of 6k cf using epoxy resin. With normal vacuum infusion stack. reinforcement/peel ply/green mesh.

](http://s6.photobucket.com/user/raxton/media/carbo1_zpsc2bdbf91.jpg.html)[/IMG]

this is a panel of a 7.5oz with a soric xf core. As you can see the look changes at about 1 inch from top of panel. That is where the soric stopped and was just a peel ply break.

](http://s6.photobucket.com/user/raxton/media/carbo2_zps3ffe541e.jpg.html)[/IMG]

Any helpful advice would be great as 8 out of 10 various panels have the carbon fiber pressed looking effect.

I just ordered some MTI hose to test out.

I have also ordered some RED infusion mesh as someone has said on here that they received better cosmetic parts with it.

:confused:

#2

Do you degas your resin ? Were do you put the resin pot while infusion ? For cosmetic parts there be a lot more resin in it. Both panels have a to low vf for cosmetic parts. Make a brake zone that’s smaller on the part and a part off the product. Degas resin if you didn’t do that already, put the resin pot at the same hight as your infusion and try to slow down your infusion. The green flow mesh is in overall to fast.

#3

If you put the resin pot on the table or above, you’re gonna flow resin faster.

Also, how long do you leave the part under vacuum before infusing?

I"ve had fine results without degassing, i’m sure it’s better to do so. What I find is that having a good break area seems to be a big factor.

Infusion is a little tricky until you get your setup nailed down.

#4

can you explain that part i put in bold, please.

are you saying both panels do not have enough resin in them for the volume fraction and need to be more resin rich for a cosmetic part.

I will really add a nice brake zone, but yes I am putting the resin pot right next to the part on the table to pump more resin in. I ordered some red mesh so hopefully that helps too.

I have tried contacting lantor to order some soric tf but they have not got back to me. anyone know where to purchase that in the US. And since its such a resin rich layer I thought it would help wet out my bottom reinforcement.

thanks for your responses

#5

I usually do a drop test of about 20-30 minutes before infusing.

I built a degassing chamber but it is only 8 inch and was too small to degas the amount of resin I am needing so I headed the resin up a bit to free some bubbles. I wasn’t to worried about little pin holes due to it being a test panel and knowing my resin had air still in it.

I will do like you said and add a better brake in it, hopefully the MTI hose will help out too.

Yea I cant wait to get it down so that I can start doing it will consistency.

#6

Yes, but there are ways to slow down the infusion. It’s a combination that is needed here.

#7

It needs more resin for cosmetic use.

#8

I’ve had mixed results using a brake zone with mti hose. On flat panels it worked well because the resin front was equal. But on more complex parts where the resin doesn’t flow completely even, it can cause problems. If the resin reaches one part of the mti hose before the rest of the flow front, then it will race along the membrane faster than it will flow through the dry brake zone, and you can end up with dry spots of brake zone that take an age to wet out. Meanwhile the rest of your part is getting way too resin rich. But if you clamp your resin line before the peel ply is fully wet out then it can leach resin from your laminate and you end up with pinholes again.

#9

how would you make a part more resin rich in infusion? Isnt the point of infusion to create a close-to perfect ratio of resin to fiber?

How long should you leave the part under vacuum for before introducing resin? When i leave it for 10-15 minutes it really flattens the look of the weave…

OP- are the pics you posted with or without a gel coat?

#10

+1 on this. I’ve experienced this as well when using a brake zone with MTI hose. My brake zone is too small to actually leach enough resin out of my part to create any noticeable pinholes, even after clearing, but I’ve definitely noticed a sealed hose and a delayed wet out of random parts of my peel ply in the brake zone. But god damn, does the MTI hose work wonders or what :love:

#11

The point of resin infusion is to allow you to achieve whatever VF ratio you are aiming for. Let more resin in and you get a higher content, let less in and you get less. But with infusion you are able to calculate it almost exactly, so you can achieve whatever you are going for and do it repeatedly.

I normally leave mine under vacuum for at least an hour, often 4-5. Depending on the number of layers and type of fabrics I’m using, I sometimes let the vacuum off and revacuum several times before infusing.

#12

what does letting the vacuum on and off do? Better compaction?

#13

I doubt it leads to better compaction post-infusion vs a part that was just bagged, but I find it gets the fabrics to sit better. If I’ve got some stiff fabrics in the layup like heavier carbon fibres or carbon fibre uni’s, then they often don’t like to go down right the first time. If they sit up a bit around a corner then there will be a void, so I release and revacuum several times to make sure everything is in it’s place.

#14

You should check your vacuum level at the part inlet rather than using a time period to guess that your part is actually at low enough pressure level. There can be a big deviance in actual vacuum level depending on many variables. Best to confirm using a digital absolute pressure gauge at the part. Also, you can speed up vacuum soak time by attaching vacuum directly to your resin inlet.

#15

Thanks for all the responses will take these into my next infusion test panel.