What product do I need for making a heat expanding plug? Silicon? Latex?

General Composites Discussions Products Talk
#1

I’d like to form an irregular shaped tube. I’ve looked at the options between using two clamshell halves with either vacuum bagging, a positive pressure balloon, or an expanding plug that is slightly undersized to the closed molds.

I’m leaning in the direction of the plug. It seems it would be the easiest way to make the part considering I’ll need to bake pre-preg. For me, that would make vacuum and positive pressure kinda difficult.

What is the better/best product for this? Silicon was recommended, I’ve heard others using latex.

Does anyone have a recommendation on a product? And just as much so, does anyone have a link or video to someone doing this?

Thanks!

#2

What size, shape and laminate thickness is your tube?

#3

1.5" dia for 13" or so, irrgegular shape between octagon, oval, round, looking at .0625-.080 layup

Recently considering skipping the over to bake the pre-preg by instead running hot water through.

#4

Tried bladders etc,etc, not successfull or could not get a quality repeat product?, I am now using Expancel for over 14yrs. with great success especially with AC elements recessed into my Alum. moulds, I use pre-preg in all of my tube and foil applications, see my post - http://compositescentral.net/showthread.php?t=5872 contact me if you need any info etc. - email: bladerunner.boats@bigpond.com
John Hayes

#5

You can prob’ use a thick silicone tube that closely matches what you want. Layup paper/wax/clay on the mold to act as material thickness, pour in silicone, put in a shape matching rod/tube. Cure. Pull out the center tube/rod, and then you have a way to inject air to expand the silicone tool.
Cap one end to hold pressure of course.

As for hot water…depends on the prepreg. It you have to cure at 250f, better to bake then attempt to pump boiling water in your mold! Plus Silicone is an insulator, so it won’t be effective.

#6

I"ve use BJB TC 5045 for silicone mandrels using the High CTE for fantastic results.

http://www.bjbenterprises.com/silicones/platinum-based/tc-5045-a-b-1/

If you have a part that would allow the mandrel to be removed, it’s a good way to go. I’ve seen the parts made for the formula mazda race series, by swift engineering in socal, and they look beautiful. They do a lot of that method and It works. So long as the part allows for the mandrel to be pulled out. Usually a rope is embedded to allow for stretch of the silicone which facilitates in it’s removal.

#7

When you make one of these silicone mandrels do you have to create another mold that is slightly undersized or can you get away with using the composite mold and dealing with the fact that that fabric will take up ~.03-07"?

also this Expancel looks great, not to thread jack but we make lots of components without open ends but that get machined afterwards. Does it maintain its powder form after heating (to less than 110C) so that it can be poured out/removed after molding?

#8

Quote:also this Expancel looks great, not to thread jack but we make lots of components without open ends but that get machined afterwards. Does it maintain its powder form after heating (to less than 110C) so that it can be poured out/removed after molding?

Re: Expancel, In my case the heating process expands aprox. 30:1 and solidifies the Expancel powder to aprox. 130kg/m2 density, I suppose this is what “Pushes” my laminate or whatever you chose to place within your chosen “Female” shape to suit your product, I make Foil, Tube and other complicated shapes that suit the use of Expancel to exert enough pressure - est. aprox. 100psi. to compact my laminate against the internal shape of my cnc machined moulds, in some cases I remove the Expancel physically to give me a lighter outcome, if I have open ends to allow access to do same?, I hope this explains the way I use Expancel?.

PM me or send me an email - bladerunner.boats@bigpond.com for more info, I am happy to help!.

Regards

John Hayes
www.bladerunneroutriggers.com

#9

the expancel looks like a cool product. What do you pay for it? And it is completely reusable right? Do they give a CTE listing on the material sheet?

#10

Hello Sammymatic, sorry the Expancel “Dies” after 1 use, it cannot be reused - I drill my cores out if trying to get a super light outcome!, * SPECIAL NOTE * re: DIES!, if you do not exceed the expansion cycle to the Kill Temp of your particular Expancel grade? - this is when the Expancel schrinks back from the ID of the laminate - you can experience another expansion if your product is exposed to long sun exposure again, especially if you have a clear glossy carbon finish, this can sometimes destroy your product if it tries to expand again!!!, keep this in mind!.

Try some of the links below, they might help you?.

PM me if you want more info?.

Kind Regards

John Hayes
www.bladerunneroutriggers.com