First attempt at vacuum infusion

General Composites Discussions Composites Talk
#1

Hi

I am attempting vacuum infusion for the first time and have I few questions. I have read numerous guides on the subject but there are still a few things I am not sure about.

I have an estimate of the surface area of the part and I know which material and how many layers I am using. How do I calculate how much resin I need form this information?

How important are flow media, I have been reading a guide about this subject on fiberglast.com. Do I need to put a layer of flow media between each layer of carbon fibre? Am I correct in saying this is not necessary if using fibreglass?
Also does anybody now a good supplier of flow media in the UK. I only need relatively small amounts so do not want to buy in bulk.

Is the diameter of the vacuum and resin tubes important? What kind of diameter should I choose? What kind of plastic should the pipe be made from? Will the pipes be reusable?

What strength of vacuum pump do I need? What pressure needs to be achieved?

How tightly should the vacuum bag fit over the mould before I turn the vacuum pump on?

Thank you very much for your help, it is greatly appreciated as I have never attempted vacuum bagging or vacuum infusion before.

If you need anymore details to answer these questions please let me know.

#2

Are you familiar with composites and vacuum baggin? This will go a long way.
I’ll come back to the questions later.

#3

http://www.fibreglast.com/documents/361.pdf

http://www.1989batmobile.com/vip/vacuum_infusion.htm

http://racingcomposites.net/unt?id=507

http://www.compositeforum.werksberg.com/showthread.php?t=188&highlight=vacuum+infusion (no pics but still a good read)

http://www.youtube.com/watch?v=CVYQl8TnyBA (looks like its going to be a good series to watch, its new so i haven’t seen it.)

Do a bit of reading with the links above and they will help you alot. Infusion is a great method to build parts by but you should also know how to make molds. You should also start off infusing flat panels to get the methods that you like to use and then go from there.

#4

1: I don’t know the formula, but it’s about weighing the fibers, and knowing the volume and density of each part. Look up FVF or Fiber Volume Fraction. Someone on here might know off hand.
2: flow media is only on top of the part. part, peelply, flow media
3: common pipes are the clear flexible (pvc???), and LDPE. if you are lucky, you can pull the resin out (whole, or broken pieces) and reuse. Size depends onyour part. Small 30cmsq peices might only need 1/4" ID, while larger ones might need 3/8" dia.
4: Pump needs to run the entire time, from debulk to final cure. Pressure should be 29" of Hg…i would not go below 26", but some people are fine with that.
4" bagging should be as slack as it needs to be, so when you pull vacuum there are NO stretched areas. This will result in hollow voids that resin will fill, and your part will not compress. The bag should be even and flush with all surfaces and curves. It’s all technique :slight_smile: All flat pieces are really easy…just need a bit extra bag to cover around the tubes, and you are set.

#5

No this is the first time I have worked with composites

Thanks to the people that have replied

#6

I highly recommend trying out some wet layups and various materials before moving on to something as complex as infusion.