Resin Infuse Around Timber Core Possible?

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#1

Hi,

I have been asked to provide a few posts for a friend which has a timber core, I am however unsure if this if possible to produce without problems. I have attached a sample image of what I am trying to produce.

The mould consists of a simple ‘U’ shape however there is a piece of timber needed in the middle of the part which needs to remain in place. I was wondering if it would be possible to lay the mould up with gelcoat and include a breather as part of the fibreglass to allow this to be cast with the infusion?

Even if this was possible I am unsure where the infusion line would go for the resin?

I could also drill some holes in the timber to allow the resin to flow through if needed however I am still a little nervous as the timber core will not allow you to see the resin flow and wondered if I could get dry spots or inconsistent coverage?

I also considered casting the outer part first then bonding the core later. My issue with this is I am again unsure if I would achieve complete coverage of resin around the part?

I am really struggling to get my head around this and thought I would post this to see if anyone has achieved anything similar to this please?

Thanks very much.

#2

Of course you can do this. You can buy Balsa wood that is scored or perforated for infusion.

Not sure what kind of mold you plan on using? Or are you just tacking the fiber to the wood then bagging it for infusion? Also are you just wraping in a U? If you went all the way around you’d have a better grip on the wood.

I’ve infused similar parts for airplanes using core material of balsa and foam. You can feed resin to the underside of the wood to help it flow. you’ll need to have either interlaminate flow media, or score/drill the wood. If you feed from the bottom, you’ll be able to see when the resin flows up toward the top or through the wood. That would help you gauge the wet out. You might have to run this a few times if the setup isn’t right. I’d put feed lines every foot or so… lots of tubing for such a long setup. It’d be a bit complicated but doable. Might be worth making a smaller section to do tests and figure your setup before committing the materials to a full length.

What is this part? The core is a 2x4 piece of lumber? I take it weight isn’t an issue on this part?

#3

Hi,

Thank you for your positive reply.

I can wrap the fibreglass all around the part so that isn’t a problem.

The weight of the part isn’t an issue either and the core is simply 4x2 timber put through the thicknesser to take a little off the size.

I am confused regarding the placement of the flow media and wondered if you could clarify this please? I plan to use maybe 3 layers of 450-600g chopstrand all around the part, do I place the infusion mesh in between this to allow the resin to flow around he core?

I was also a little confused where to put the flow line as this can only be placed either end of the mould or on the top. If I placed this on the top I guessed it would flood the top first and reach the catch pot before the resin infused the lower part of the mould? Am I correct to presume this?

I don’t understand how I can add the flow line anywhere else?

Thanks again for your reply, any further advice would be ace as I really am worried about how best to approach this :confused:

#4

I can’t answer all your questions but if you have an infusable core than that itself will be the flow media. For example if you put Soric Core underneath the wood that will distribute resin to the plies underneath the wood.

#5

As canyon says, you can use soric, which is a flow media/bulker and will help to distribute the resin. I haven’t used chop strand for infusion, but others have and supposedly it should work.

as for where to put inputs. You can of course put them along the top, but they can also be on the bottom from the mold side. Really it’s gonna have to be tested to see what will or won’t work exactly. You will need to have them along the length, in several places for a part that long as the resin won’t travel the whole distance. If it were me, I"d input resin on the back side and have vacuum on the opposite side. I’d use many ports so I could clamp off the vacuum lines as the resin travels around, then I could control the flow some what and avoid choking off the vacuum lines. If your using a mold, then the mold would need a resin channel of some sort since you can’t really put flow media in there. It’s also hard to put a break with peel ply but, I think you could probably make brakes in a long pleat running along the top, though it might run risks of race tracking along any pleats.

I’m still a bit confused as to why you would use a 2x4 for core? You’re going to leave this in the part? maybe you can’t have a solid part? Does this part need to be infuse or could you do a wet layup? SInce its made from CSM it’s not going to be the strongest part anyway, and with a 2x4 on the inside, the wood would carry a good amount of load.

As with any composite situation, you need to figure out the process depending on the needs of the part and the ease of manufacturing. Infusion does give some good quality parts when done correctly but, can be a pain to setup. Once setup is should go smoothly. If you’re only making a few parts it’s not necessarily the most efficient method. You have to think about what sort of time for setup is involved and the costs of failure. Is this something you absolutely have to make or can you buy a premade piece that is pultruded or wound?

I’m just trying to figure out better what would be best/easiest/most efficient.

#6

Hi,

The timber has been provided at no cost and I don’t really have access to anything else as other than this we deal in plastics primarily.

I did consider a wet layup too but I really was unsure if I would be able to ensure the core is completely covered with resin once it was inserted and the whole thing bagged and the vacuum applied.

Potentially there are large numbers required and I have been asked to have a go at trying to get this to work so I am a little keen to find a way forward. I guess this isn’t going to be plain sailing and more than prepared to put some effort in to find an efficient way of making it work.

We have lots of supplies available to us in our factory, I can also score the underside of the timber and place some breather at the bottom to aid the flow of resin. We also have triaxial cloth which we can use in lieu of the CSM. I wasnt sure that the resin would flow through the CSM either so was planning on putting in a breather cloth which would end up being part of the laminate.

I guess I have to test the best method as you suggest, it’s really the breather fabric placement and resin line placement that’s throwing me as this is new territory.

I really appreciate the time taken to reply, the advice and opinions really are a huge help, thank you very much indeed :slight_smile:

#7

Sounds like a good challenge.

Definitely start with a smaller section and figure out the kinks.

The most important part will be your inlets and vacuum plus the flow media.

You may also want to start off by just doing some test pannels first with the various materials you have. Try the triax. I used to use some ±45 triax for infusion and it worked fine. The triaxial would be stronger and probably easier to lay up. You should only need one ply or so for strength. You can add CSM to bulk up thickness if necessary. I do think you’ll want to get some soric for your tests too.

Probably make up a batch of test panels with various ply schedules to see how they are after infusion. You can also do some pannels with a piece of the 2x4 laid up to get an idea of how to setup your molded part. The areas underneath the core will be the area of concern. The extra compaction from the core makes the infusion a bit more difficult but, completely feasible. You can also try some with grooves, some with perforations, and some with both and none, to see how they fair. No point in adding extra work if it doesn’t help.

Though I think ultimaely it would be best with the soric and the inputs some where on the bottom of the wood with the vacuum running along the top in the middle of a peel ply break and no perforations. The distance isn’t to far for the resin to travel and it should make it over the top no problems.

What resin are you using?

#8

I have ordered some soric today so that will form part of the test for sure. The supplier did say it was feasible but they did say it wasnt the fastest slow media.

I think I will score the core as that really isn’t a problem as we have CNC equipment at the factory. I am using polyester infusion resin from Scott Bader, I ordered this today also.

I think the challenge is getting the resin from the underside around and over at the right time. My problem is I can only see logic to infuse from one end and vacuum from the other to minimise on the possibility of not soaking the resin all the way through. I suppose that’s my lack of experience shining through lol

It’s definitely a test that’s for sure, I cant find much similar online which also can be seen as a bad thing!

#9

I have been able to infuse carbon to 3mm MDF wood board. It didn’t adhere to the MDF as well as I would have hoped (as I was able to pry off the carbon with a little bit of effort) and I could tell the epoxy didn’t flow all the way through the MDF (as there were some dry spots on the MDF after I pried it off), but it did work.

My supplier told me he is able to obtain a special carbon or fiberglass that has flow media woven into it and I could probably sandwich it between the carbon and the MDF and it might help. I am going to be trying that next.