Infusing carbon fiber leaf springs

General Composites Discussions Composites Talk
#1

I want to infuse a set of leaf springs for a piece of sporting equipment.
I’m using 3 layers of 9 oz. uni per leaf. There are a total of 7 leafs per spring. Each spring is 6" wide and about 12" in length. (the uni runs parallel with the length.)
Each leaf will be separated from the others with polyethylene sheeting during the infusion and no bleeder layers will be used. The entire stack (with the poly) will be about 1/2" thick…and will be draped over a mold with a substantial radius to it.

My questions:

  • Would it be possible to pull epoxy through this type of layered stacking using an infusion pump…given that I won’t be using a bleeder?

  • If so, what is the lowest viscosity epoxy I could use for this without sacrificing the springs performance?

  • Would it be better to pull side to side (perpendicular to the grain) with a 6" travel path…or end to end (with the grain)…a 12" travel path? Or does that even matter?

Also, if the infusion process doesn’t pan out…and I decide to lay the springs up wet…can I put individual leafs in the freezer temporarily to stop the cure until I have a full set ready for the mold? I would like to build a set of two springs at the same time which will very likely take a couple of hours.

Thanks so much!
Steve

#2

You never use bleeder with infusion. Are you referring to flow media?

#3

[You never use bleeder with infusion. Are you referring to flow media?]

Yes. I’m new to this. (What is bleeder used for?)

#4

if your resin has a long enough gel time, yes, you can infuse carbon fiber with interlayers and no flow media. I can not say what viscosity, someone will mention this I’m sure. However, it should be as thin as you can get!!!

For what you are doing, infuse the short distance.

you can, yes, hand infuse/wet layup each layer, freeze as needed, then assemble the system and let it cure. Or, again, if you use a long gel time (say, 10hr gel time epoxy), you can just do a normal wet layup, and bag it, and let it cure. No freezing needed. You can even oversize the part, and cut the size you need. with the PP/PE sheets, each leaf will separate.

#5

Bleeder is used in vacuum bagging to absorb the excess resin as the laminate is consolidated.

#6

Thanks gentlemen,
I really appreciate your help.
Please be patient while I get up to speed with using this forum. I’m not yet sure how to select individual lines for quoting. I’ll figure it out, but for now, the responses I’m quoting are in brackets.

[if your resin has a long enough gel time, yes, you can infuse carbon fiber with interlayers and no flow media. I can not say what viscosity, someone will mention this I’m sure. However, it should be as thin as you can get!!!]

Will I sacrifice strength and flexibility as I decrease the viscosity of the epoxy? Would the West System 105 with the 209 hardener be sufficiently slow…and low in viscosity…to achieve full wet out for this application?

[For what you are doing, infuse the short distance.]

Would it help to build a stack of flow media next to the interlayers of CF to give the epoxy a “ladder” up to the upper layer…since the layers will be separated with PE?

[you can, yes, hand infuse/wet layup each layer, freeze as needed, then assemble the system and let it cure. Or, again, if you use a long gel time (say, 10hr gel time epoxy), you can just do a normal wet layup, and bag it, and let it cure.]

Where’s a good place to get quality epoxies (and related materials) online? I’ve purchased some material from Fiberglast.com…and then read in a few posts in this forum that they are really expensive? I found that to be true when I compared their price on 3M’s Super 77 spray adhesive with Ace Hardware’s price…Ace was 3 times less.

Thanks again…your help is likely going to save me a lot of time with research and experimentation…and $ in materials. I’ve learned a lot on my own already…but there’s a balance right?

#7

Yes, or enlarge the CF layers, and offset the PE layers internally:
CCCCCCCCC
ppppppp
CCCCCCCCC
ppppppp
CCCCCCCCC

or

ccccccDM
ppppppDM
ccccccDM
ppppppDM
ccccccDM

As for the resin, I’ve used 300cp resin that has a 24hr geltime successfully on many LARGE plates with no DM, or interlayered systems.
Applied Poleramic Inc. from Belincia CA: SC-15, CCMFCS-2 and SC-79

#8

Thanks again Riff…what’s DM?

#9

distribution media/flow media/mesh are some of the names.