first Infusion

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#1

I am making a set of rocket fins for a pretty serious project. I have just finished the two part mold and would like to attempt to infuse them.I’m hoping to use a unidirectional carbon fiber in the layup for the most part. I plan to add a couple pieces of a weaved material to help the resin flow through the uni because I’m thinking the uni itself may not infuse well.
As I set this 15"x15" project up ,I hope to produce some pics and get some advice in regards to setup.
The laminating epoxy I normally use is Resin Services HTR212 with 386-99 hardener.
A couple questions:

Could anyone recommend a good high performance epoxy with a fairly high Tg ,say 300 degrees or higher that will have a low enough viscosity to infuse?

And could anyone give me there thoughts on infusing Unidirectional carbon?
Thank you,
Terry

#2

I decided to try a test. There are four layers of uni carbon fiber tacky material down that is .020" thick. They are orientated at 0 degrees,15 degrees. 30 degrees,and 45degrees. This was material I had laying around that I could sacrifice.
The carbon I am using in this test is twice as heavy as what I want to use in the real layups so I used a little more than half the layers I plan to use later.The main objective of the test is to see if uni will infuse while orientated directionally.Also to get a feel how this infusion stuff works.
So here’s what I have so far.
I’m wondering if I even have this set up any where near correct. If anyone would want to give me a little advise I would greatly appreciate it.
Thank you,
Terry

#3

It is perfectly possible to infuse carbon UNI, but do remember that it is a SLOW process. In general 4-6 times as slow as glass. Do not use a high speed infusion mesh, or you will end up with dry sports within your laminate.

After infusion of your sample, cut it in several places to see if the resin went through and through.

#4

It’s been my experience that cutting the infusion media short by an inch stops the resin flow sufficiently to eliminate voids in first part of the infusion but close enough to the edge where the non mesh part infuses as well, albeit more slowly.

I feel like infusion mesh is invaluable for infusions but am I missing something here?

#5

The green mesh is what the salesperson basically handed me. He also had a red mesh offered for sale. If I remember correctly the red mesh had larger holes in it. Is the green mesh typically a fast moving flow media?

I’m waiting on the mail for a leak detector. Next week Ill give it a go and then cut up the sample. Ill post pics of the results.

I also have some Pro Set infusion resin on order, but on this test I may try a resin I have in my possession . The viscosity is around 600cps, and try warming the layup with heat lamps just to see if it goes through. If I can get this epoxy to infuse it would be better. I am looking for a higher Tg resin. So maybe Ill get lucky and the faster flow media will become an asset with the high viscosity epoxy.

I hope I can learn enough from this first test to at least start some test using the actual mold.

At this point I am thinking more in the lines of using a plain weave , a twill, weave , and also incorporate just a couple layers of uni in the layup.
Thanks for the input and advise.
Ill let you know how it goes.
Terry

#6

Now that you mention it , I have seen this in some pics.Now I’m wondering if I should open up the bag and cut an inch off the flow media. Except for the fact that I may try a higher viscosity resin and warm it.I’m thinking this resin may slow the flow down on its own (maybe too much). Does this make sense?
Ill post pics of the results next week.
Thank you Terry

#7

It does make sense. In infusion its good practice to match flow media with resin viscosity. Thicker resin requires faster flow. I wouldn’t cut the bag open if you already have it sealed. For this one part manually control the resin flow by kinking the tube till the flow is sufficiently slow. By controlling the inlet tube bend you can slow or speed up the epoxy. The next time you lay up though take some of the suggestions. By studying the flow patterns you’ll quickly become experienced and know how to set these up to work everytime.

#8

Sounds good Canyon. Ill keep that trick in mind and all suggestions on paper.I hope to get more comfortable with this process partly because I am allergic to epoxy and this would be a lot cleaner than hanging over a wet layup for a couple hours at a time while wetting it out.

I think with this test the main things I will come to a conclusion on are if I can get the epoxy I have to infuse,to get a feel how the infusion flows and how well uni infuses layed out directionally. I would have liked to get a little more out of the test but I know I will be using a lighter fabric,and may end up using a thinner epoxy.If I had these fabrics here yesterday I would have used them but there not in my hands as of yet.
Thanks again,
Terry

#9

Well, I busted loose the two halves of my mold today. The first side came out well but I will have to do some repair to the second side.Im not sure what happened but when I took the thing apart my plug had a big crack in it. This made one edge of the plug dip down into the parting board about a 1/16th of an inch more than I wanted. And some flash wrapped around the plug on the side. So I trimmed it up and pulled out the part. Now I chipped the edge at the parting board.

I feel that I got lucky because I can repair it by doing some detailed sanding and a little filling with surface coat.

I’m not sure why the plug cracked.There was some body filler in the part, maybe the heat from the mold surface coat kicking off did it.Also I did raise the post cure temp up higher than I usually do in knowing I will want to post cure the actual parts.

I’m just glad it didn’t turn out worse. I have a few weeks into making the part from scratch and then making the mold.
Here’s a few more pics.

#10

After a moderate postcure, you could have demolded, and then carefully postucre to a higher temp freestanding. Plugs can be problematic at times. (specifically CNCed PU moulds)

Your resin will infuse quite fast with any of the plastic meshes. I believe the red mesh is slowest, but you might want to slow the resin down. As said in another post, infusion is not a race. It is about quality.

Canyon said you should match infusion mesh speed with resin viscosity, but I prefer matching it with permeability of the laminate as well. Total infusion time can be influenced by rearranging runners, and this is the factor that worries me the least.

The carbon weave can help aiding in resin flow.

#11

In hindsight I guess I should have broke the two halves and took out the plug. The good news is the mold is repair well.Ill remember that next time.

If I am able to infuse with the resin I have(Resin services HTR212). I will have plenty of time to let it infuse as slow as needed. I just have to figure out how slow and not so slow that it never reaches the end.suggestions Ive gotten to slow it down are to “adjust the flow media covering the carbon more or less at the vacuum side” and then “bend the resin intake line to slow resin flow”.Actually, I’m concerned on the 1st test that It may move too slow because of the resin I am using.

I have been to a demo that was put on by a supplier. It got late and I never saw the actually resin flow,only set up.
So that demo and this web site are all I have to go with as far as figuring this out. So I hope to keep showing you guys the plan and I will correct as I go.I will draw a sketch of my setup and post it.Maybe we can pick that apart in hope to do this closer to correct the first time when I set up the mold.I hope you will stay tuned in.

When I was at the demo, I had not made the mold yet. The supplier suggested I put in the three troffs running along the outer edges to add volume. I don’t plan on putting any vacuum lines in them , and I don’t really have an understanding as to how they help. I just figured they shouldn’t hurt.Are they a concern?
Terry

#12

Staying tuned. Setup is most important, resin flow is just the aftermath.

The three troffs? No idea what they are for. My concern is that they will put a lot of strain on the bag. I suggest filling them at least with spiral wrap. Keep in mind that eventually every cavity will be filled with resin.

Can you give me a mail? I have something for you. (herman at bugattibuilder dot com)

#13

I had asked the guy that told me to put the troffs in if it wouls strain the bag and he said I was to bridge the treoff with peel ply.
I like your idea better. Ill protect them with spiral tubing.
I kinda wish I didnt put then in now ,mainly because I dont know what the benefit of them is , and they take up room on the plate.

I shot you an e-mail
Thanks Terry

#14

Something I want to ask while its on my mind.
When I start working with the real mold I want to keep the body line running down the center of the mold nice and crisp.I don’t want any surface coat on the fin because I want carbon to carbon when I attach these things to the airframe.And I will have to put some reinforcement on from the fin to the airframe.

But would it be a good idea to spray in a little surface coat just along this body line. I’m concerned that the line may want to become a soft curve
Terry

#15

1: uni CF is slow…
2: cut your distro media SHORTER THAN YOUR PART!!! on the 3 sides you are not infusing on. Maybe 1/2 inch at least for a small part. This way, the resin doesn’t flow OVER the carbon stack, cutting off the air on the bottom.
3: u can use peelply in your resin stopping trench, no need to use breather, except at the very end near your vent fitting. It will slow down the resin like crazy.
4: that layup isn’t going to give you anything in terms of…anything…cept a warped potato chip

#16

Your sure right as far as the potato chip comment. I have the layup on a thin sheet of stainless steel plate. It curled up a little.
Ill make sure to cut the flow media short on the real deal.
Thanks Riff

#17

I gave the first test infusion a go today. I had mentioned earlier I wanted to see if I could get a certain laminating resin to infuse by warming. I put heat lamps on the part and heated it to around 100 degrees, then I warmed the resin. Once the resin started flowing it moved kinda quick for the first 15-20% of layup then it slowed way down. It took about 12-14 minutes to cover. Now its just sitting under vacuum drying.

I wish I would have put the layup on something different than a thin sheet of stainless steel. The layup curled up a little.

The flow did seem to come across the layup fairly evenly though.

I’ll chop it in pieces and see what happened tommorrow and then post.
Terry

#18

Can I ask why it would curl up?

Is this because how thin the sheet metal is or change in temperature when in cure.

Also those heat lamps, are they distributing the heat evenly or where it shows the red circle? The reason I ask is because I found when I’m laying flat panels, if I used the heat blower on the part, there were flow issues in places, if I used a room heater, holding the room at 30 deg c, the flow was much better.

Stu

#19

I thought it was the layup making it curl. But you are correct. I turned the heat off and it laid down flat again.

#20

if all the fibres are going in the same direction there is little to hold the shape in the other direction, therefore it will bend easily and end up looking like a pringle.