A few questions on resin infusion

So i am making up some foam cored panels to replace the plywood cabin sole on a project at work. I am using infusion on a temporary melamine table and using materials that we have in stock, so, not necessarily what i would choose. The panels are simple 1/2"perforated foam with 1 ply of 5 harness satin 6k carbon, 10.9 oz each side. I have done a fair amount of infusion over the years but usually much larger parts in stitched glass so a lot more, heavier plies and also, typically, contour balsa core or solid laminates so plenty of paths for the resin to get through from the top and travel across the molded side. With this i am using materials i have not infused with before and i was a bit unsure of how well the resin would pass through the core as the perforations are on 4" centers ( i am used to closer than that with balsa or double scored foam) and how well the resin front would move on the mold side as there is not much bulk in 1 ply, however it is woven so i felt was a better choice than the double bias carbon we also have in stock as far as the resin drawing through it goes. I did the first panel a couple of days ago which is about 48" x 20" and it came out pretty well except that, as i was concerned about, there were a few small areas that did not wet out on the mold side. No big deal as we just mixed a little resin and wet them with a brush. I forgot to mention that i am using infusion VE and i warmed it up to about 70 degrees F so it is quite low viscosity. So, i think everything worked fine but i need to slow down the flow, give it more time for the resin front on the mold side to progress. It took less than a minute to get to the vacuum line so i have plenty of time. My stack on the top was the layer of carbon, peel ply, green infusion flow media and the bag. I usually use the red flow media but i used the green because i think it is supposed to be slower but clearly not slow enough. So my questions for you folks are, can i eliminate the flow media altogether and rely on just the peel ply, maybe add a second layer of peel ply. Should i back off the vacuum. I am using MTI tube for the vacuum side and 3/8" spiral wrap for the feed.

 

I can’t help due to limited experience, but the perforations are generally used in wet bag work; not infusion afaik, so I would want flow channels on the bottom.

 

Steve, would it be out of the question to just hand laminate and using the peel ply and vacuum bag to consolidate/hold flat through cure?
The you can skip the infusion media and tubes and not wonder if the sauce is going to make it through the layup.
I don't do a lot of carbon, normally just reinforcing patches here and there. I did make some 'door skins' for my two galley cabinets with 6oz 3K plain weave. They were done open-air over melamine coated with PVA mold release.

 

Fallguy, there are a number of ways to get the resin from the top to the bottom molded surface, in the past i have used the same balsa contour core with the scrim on one side as has been used for half a century and this works great, foam is available for infusion as drilled perforated core such as i am using for this project as well as kerfed, knife cut and double knife cut. They all have their applications. We have cases of double knife cut pvc core but it's all 1" thick which is unnecessary for this application. I think the holes on 4" centers seems fine now having done this one part, i think i just need to slow the resin flow down so the resin front on the mold side has more time to catch up. I may also have clamped off the feed line a little soon. Overall a nice part though with just a small repair. With just vacuum bagging you don't necessarily need a perforated core does help draw the air away to the breather on the t
op but you do generally use a plastic perforated film between the peel ply and the breather/bleeder to control how much resin you keep in the part.
Tops, I did consider just vacuum bagging but i do prefer infusing when i can, hand laminating is messy, smelly and on larger projects, potentially stressful. I also don't work with carbon much but i don't see much difference other than having to deal with woven fabrics which i find a pita. I have rarely had problems with the resin wetting out the mold side with layups i have done before but as i said, they have always been with more plies. The main disadvantage i feel with infusion vs vacuum bagging is the extra plumbing and the greater need for vacuum integrity, with vacuum bagging its just a clamp so more tolerant of leaks. With bagging you eliminate the flow media but you actually have more layers on top of the part, peel ply, perf film, breather/bleeder and the bag. I'm also working in an area where others are working so reducing the smell while using VE is important. I have done quite a bit of infusion over the last decade but i'm always re learning as i don't do it very often.

 

I don’t have a great deal of experience with vacuum infusion, but the few projects I have were done on a glass table top, allowing a clear visual of the wetting out of the bottom of the laminate.
It’s not an answer to your question, but it’s helped me tremendously to understand resin flow with various material combinations.

 

Thanks KapnD, i do actually have a glass table for testing samples but it is not at my workplace where i'm doing this and it is not easy to get to. I am pretty sure that slowing it down will get me there but i'm not sure the best way to go about this. I can reduce the vacuum, eliminate the flow media altogether and just rely on the peel ply, maybe add a second layer of peel ply. The VE resin is very thin so it moves pretty quick compared to the Proset epoxy infusion resin i have used on a few past projects which is much more viscous. I could switch to regular West system 105 epoxy (non infusion) with i think the 109 hardener. All kinds of options i guess. I think,( unless someone with experience chimes in and tells me it's a dumb idea) i will try the peel ply without the mesh. The good thing is none of these parts are very big so no big loss if i have a failure. The largest parts will be about 77" x 20" and i will do those last. They are just floorboards.

 

Hi Steve, increasing resin viscosity or reducing vacuum will not help.
Did you have the flow media go right to the edge of the job on the vacuum side? if you did try holding it back 3". If you did hold it back increase this amount.
Slower media will help, I have used a very fine white media (DelStar ?) much slower than green. I mostly used the knitted Shade Cloth, 30% shade for slow and 70% shade for fast, much more economical. Readily available from a hardware store in the 70 to 90% shade range, you may have to go to a specialty Shade Cloth Supplier for the 30% cloth.

Other option is to drill more holes, stack 4 sheets and use a high tensile steel rod not a twist drill. I sacrificed the top solid tip from a telescopic car radio antenna, round the tip like a bullet head.

Cheers Andrew

Having a center feed and vacuum lines either side on the 20" dimension should work with no media.

 

Thanks Andrew,
Yes, i did run the flow media a bit past the part out onto the table and had the vacuum line on top of it in the corner. I am using MTI tube for the vacuum line and i believe they want it on top of the mesh. It's been a few years since i have done any infusion so i'm a bit rusty. When i first learned infusion we would have place the vacuum line maybe 6" outside the part and i think run the peel ply out but stop the flow media at the edge of the part or something like that but since i started using the MTI tube i have been putting it right at the edge of the part.

 

Steve, I haven't used the MTI tube my self, not even sure if its readily available locally but would be nice to try it out. I don't do a great deal now my self just an occasional small part or a carbon instrument panel for friends.
Unless you drill a lot of extra holes stopping short the flow media is the only thing that you can control to reduce the lag between the top and bottom resin fronts. You could always have the media on the table side as well as top if you were not concerned with waste.
The fine white mesh would be ideal for that approach as it only used about a third of resin compared to the green mesh and does not leave much of an imprint on the laminate.