Carbon, water saturation

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#1

So I was using some of the multiaxial I bought off the forum and had some issues with water saturation. The parts were made with 5 layers of multiaxial and some with 2. They were well saturated with a high temp epoxy. The parts had been sitting in my garage for a while and I wanted to wash the wax off of them so I decided to wash a couple of the parts. I noticed that almost immediately the parts began to sag! They became extremely flexible and after drying retained the shape I had bent them into. After post-curing the rest of the parts I was curious and tried wetting out one of the pieces. They sitll absorbed water and lost some strength but it was less pronounced that before.

Anyone have an idea why this is happening? The parts were fully saturated so I dont understand why this would happen!

Evan

#2

1: even 2 layers should be hard as hell!!! It was not infused correctly at all then. Might have racetracked around the top and bottom, not the middle?
2: are you sure the fabric was sized for whatever epoxy you used? I know my Saertex stuff I have is NOT sized for the VER I used, so I have fiber/matrix bonding issues. (But it’s for a luggage box, I’ll live)

still…to droop when wet? weird.

#3

by chance did you use hot water to wash it?

I have a resin system that even while cured if you wash of put under hot water it gets flexible and soft but hardens back up once it cools.

#4

Yes, I did use smoking hot water to clear off any excess wax as well. The part was not infused, I used an epoxy resin and heated it using a heat gun to reduce viscosity and ensure it was fully saturated…When the plates were removed, there was resin around the plate so I believe it was fully saturated. If i seal the part with clear coat, will it stop this issue?

#5

So the water was actually absorbed by the resin?

it could just be that the resin may have been under or over catalysed or that it could have a very low tg and when you expose it to the hot water it begins to glass transition thus allowing you to bend it around and the it just keeps what ever shape it has once it’s cooled enough.:confused:

#6

See the thing is, it is a fairly brittle but very high temp resin. The water saturation happened bot before and after curing. I work with a gram scale to ensure that the mix ratio is very close to perfect. For this particular resin, I believe the ratio is 18g/100g…It is always within a gram give or take on each end. I am slightly curious but will have to test it out again.

What is the overall opinion regarding the multiaxial?

#7

Ok, so wetted out fabric, then clamped between plates?
Obvious question: Was the resin fully cured before you washed it? If it was sitting in a cold garage before it was fully cured, MAAAAAYBE it wasn’t, and the epoxy reheated, got softened, then cured later into the final shape.

Yeah, I just don’t know about this one.
I’ve had Saertex fabric pull apart on me after a 2 layer infusion, that confused me until someone told me there is almost NO multi-axial out there with VER sizing, and the fabric was old, so any sizing might have failed. But to re-soften? Hmm.

#8

doesnt polyester resin absort water?

#9

read above…I was using epoxy. I think it sat for a few days but I guess anything is possible. I think I may have to investigate this a bit more. Thanks for the suggestions.

So what is the general concensus?..how is the seartex? I think it is a great carbon fabric…nice and thick but I have to figure out what works and what doesn’t…