Talk Composites - The Forum for Advanced Composites

Poor B side surface on vac infused part

http://www.talkcomposites.com/Topic34482.aspx

By bszikszai - 12/30/2019 9:40:10 AM

Hi, I've been trying to vacuum infuse basalt fibre using the EC infusion kit with an existing vacuum pump. The mould is made from aluminium, and the A side seems to be coming out really well, but the B side (peel ply side) looks to be aerated between the top few layers every time. I recently changed the direction of flow to run along the part rather than across it, which was an improvement but its still not coming out right. I've tried this 4 times now with various directions and layups but I can't seem to get it to work properly.

I wasn't able to order an EC epoxy as I'm in Australia so have used a local resin supplier. The vac pump pulls a strong vacuum, well under the -30inhg gauge minimum. I haven't degassed the resin.
Is there anything specifically that causes this type of failure?







The left one was resin flow across the part from left to right, and the right piece was flow from top to bottom, having to travel over the bends.

Thanks
By bszikszai - 1/20/2020 5:29:55 AM

 
Hanaldo - 1/20/2020 4:56:14 AM
Yeh sure, I know basalt well, I only ask because most people are using it for cosmetic purposes. I have had similar experience to you though, I find it's interlaminar bond strength very poor - I was getting full fibres peeling off in strips rather than little bits like you have experienced. I always just put it down to the specific material that I was using, so it's interesting you have come to the same conclusion with a different supplier.

There seems to be a pattern forming here!

I've been speaking to some composite specialists at a university down here, and it was suggested that the issue might be related to fibre sizing (https://www.michelman.com/Industrial-Manufacturing/Reinforced-Plastic-Composites/Fiber-Sizing/), and incompatibility with certain types of resin. Basalt is used a bit in surfboard manufacturing down here, and that mostly uses polyester and vinylester resins with hand lamination.

Interestingly my really bad results have been consistently from the 330gsm fabric, whereas the 200gsm was almost passable and felt quite strong, EDIT: but I tested for failure by bending it... low and behold, there was noticeable separation between the epoxy and the fabric. I'd say it was the same as what you were seeing. This didn't happen with my CF test plate at all.
 
I'll probably do these parts in CF as I need to progress my project.