Jump to content

Fibreglass, Carbon Fibre, Paper Mache - The composites chat thread


Roman

Recommended Posts

I take it back. 
This was a complete failure haha. 

Almost none of the resin soaked into the actual carbon.
Not sure if my resin is too thick compared to proper infusion oriented stuff. 
But I think the main issue was that my resin ran out juuusssttt a bit before reaching the far edge.
But it seemed sweet and I'm Dutch so I didnt mix up some any more resin.
But it probably would have soaked up a fair bit more to fully saturate the fabric if I kept it running.
Also, I should have oriented the in and out pipes the short length across the part and used some spiral stuff so it flows more uniformly.
It's really really really nice to be able to have a dry layup of cuts though and not feel time pressured.

At the very least, I'm happy that I can now make bags that can pull down to about 8kpa absolute pressure without leaks.
Will try again! 

One of the best parts of vacuum bagging and using peel ply etc is that its like unwrapping christmas presents at the end. hahaha.
It's like the satisfaction of peeling off those clear stickers on your phone screen but on a much larger scale.

Link to comment
Share on other sites

  • Replies 306
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

You are correct in mixing more resin, also allow the resin to flow a while into the resin trap (I assume you're rigged something up?) can also help at this stage to drop the pressure a tad to prevent the resin outgassing .

Spiral tube works well, but you can also notch standard tube to the same effect.

Be careful of short stumpy flow paths, they can short easy, providing your pot life is sufficient, that length should be fine. 

I'm not sure of the layup you're using, but the peel ply can act as a short circuit preventing full wet out.

What does your pump pull down to? your bag should go to that pressure too.

  • Like 1
Link to comment
Share on other sites

Pump goes down to about 8kpa.

Yeah ive got a big degassing chamber in line with the pump so resin wont reach it.

Thanks ill try again with more resin.

I wasnt using peel ply but the perforated blue plastic stuff thats supposed to let resin through. Then that flow mesh stuff on top of that.

The pump pulls down to 8kpa with bag on it when the resin line is shut off.

Link to comment
Share on other sites

So I would like to make some headlight blanks for my racecar, as there does not seem to be anything available off the shelf. The problem being this is totally foreign to me. But I am keen to learn a new skill.

 

Now if I wanted a rough finish could I potentially just lay up some carbon fibre directly over the outside of the headlight after applying some form release agent?

 

What I thought may work better is splitting the lens off the housing and laying the cf inside the headlight lens to improve the finish? 

Can I get the bubbles out without a vacuum setup. I do have a hand vacuum pump but assume this would be painful /gutless?

These do not need to be show finish naturally. Is there any good noob site to visit to figure out what the downfalls are.

 

  • Like 1
Link to comment
Share on other sites

Id just make a mold. Its not as hard or time consuming as ya may think. 

You will need to take the assembly and turn it into something with no negative angles using clay so that the mold will pop off.. 

Dont worry about bubbles. Its really only an issue in the first coat of resin- dust the surfsce with a flame or heat gun and they will all pop.

I suggest taking it into the fiberglass shop (frankton) and having a chat with them. Pick up some clay and west systems epoxy with slow hardener.

  • Like 1
Link to comment
Share on other sites

Well I havent made any more useful parts but I've made a lot of test pieces that have ended up in the bin.

I tried another resin infusion but using a larger diameter feed hose and with a resin that looks a bit thinner. 

This flowed across the part a little quicker but then still had poor absorbtion into the part. 

So tried again using peel ply instead of the perforated plastic sheet between the CF and the flow mesh. 
(This was probably half my issue) 

I read a few posts where people had success by heating the resin as its viscosity massively drops with some heat.

But, then how do you avoid making your pot life too short...
Answer is to heat the part and keep the feed pot cool. 

So got my part up to maybe 35 degrees by sitting it on the heated bed of my 3d printer with a heat lamp on top too.

And then holy shit, the speed at which the resin flows through the part was amazing. Was almost like water. 

And, the resin penetrated right through 4 layers of tight weave CF! Awesome. Apart from one corner which was a bit dry because it wasnt very well in the flow path. Because I was just using a hose in, hose out. Rather than spiral tube or similar to disperse the entry and exit points a bit.
So I'm confident that my next part will be fully saturated with resin if I use spiral tube.

The next part I try will be hopefully be a "keeper" so I'll let it cure properly before unbagging haha.
But need to make a more rigid mold now that I'll be using vacuum bagging rather than my initial plan. Which was laying up around a dissolvable core which I havent been able to print successfully.

Also, the spray adhesive stuff is an absolute lifesaver for trying to dry lay up parts in a meaningful fasion. Jesus. Night and day difference.

Hopefully soon I'll have something worthwhile to show for my efforts. Oh, and using PVA instead of the wax and the surface finish no longer looks white-ish anymore. Awesome.
 

Link to comment
Share on other sites

On 25/04/2018 at 08:09, mjrstar said:

So I would like to make some headlight blanks for my racecar, as there does not seem to be anything available off the shelf. The problem being this is totally foreign to me. But I am keen to learn a new skill.

 

Now if I wanted a rough finish could I potentially just lay up some carbon fibre directly over the outside of the headlight after applying some form release agent?

 

What I thought may work better is splitting the lens off the housing and laying the cf inside the headlight lens to improve the finish? 

Can I get the bubbles out without a vacuum setup. I do have a hand vacuum pump but assume this would be painful /gutless?

These do not need to be show finish naturally. Is there any good noob site to visit to figure out what the downfalls are.

 

Which ever side is up against the mold is what comes out nice. 

So if you lay up against the light directly you'll get a nice looking inside finish that no one will ever see haha. 

+1 to just waxing / PVA the shit out of your headlight lense and then make a mold, then layup CF into this. 

There are a few videos posted earlier in this thread on Youtube, by Easy Composites I think its called. Watch all their stuff its awesome! 

I've found the best way to avoid bubbles when wet layup is I bought some big shallow plastic bins, and I'll wet layup the sheets (already cut to shape) and then let them sit for 5-10 mins. Then drape them onto the part. 

And get CF with a fine weave or it frays like crazy and it's bloody hard to do anything with. 

Link to comment
Share on other sites

cheers guys,

that bonnet tutorial linked a few pages back is legit, i think a single piece mould would be pretty easy to take after watching that vid, then i start tihinking hmm front guards could be pretty easy to do too.. heh.

  • Like 1
Link to comment
Share on other sites

@Roman when you say wet layup, you literally mean soaking the matting in resin and then just letting it rest for 5-10 minutes in the tub? I would’ve thought the resin would go off in that time?

havent done FG yet but really keen to start soon. 

Link to comment
Share on other sites

4 hours ago, Mr Vapour said:

Remind us of whAt car it is. 

I would not bother with carbon for the light covers. You can buy dyed fiberglass that looks the same but will be much cheaper.  Unless you are doing what Dave is doing there is no benefit in hand laying carbon. 

I have an old EK civic hillclimb machine, nothing too flash. It's probably more for the skill and experience than the outcome.. ideally I do want to trim a few more kg's out of various bits and pieces after coming to grips with the process...

 

 

Link to comment
Share on other sites

14 hours ago, kws said:

@Roman when you say wet layup, you literally mean soaking the matting in resin and then just letting it rest for 5-10 minutes in the tub? I would’ve thought the resin would go off in that time?

havent done FG yet but really keen to start soon. 

Yeah it seems counter intuitive but with epoxy it starts going off in the pot way quicker than when its on a part. 

Because it builds up heat which causes the epoxy around it to build up more heat and it gets in an exponential cycle. Can start smoking and melt your pot if its plastic! but when laid out in a thin layer the part its on helps cool it and it stops this process. Like your pot might last 15 mins or less but your pieces of cloth could sit there with epoxy brushed on for hours before even starting to cure.

So if you get the epoxy onto the cuts of cloth asap and then there isnt really any time pressure anymore.

And it gives the epoxy a bit of time to let off some of the gas that can cause bubbles in your surface finish.

 

  • Like 1
Link to comment
Share on other sites

Yeah facelift ek ones can be sourced from overseas (and also a guy in taumaranui) but my car is pre facelift. Have spent some time trying to find 96-98 spec light blanks with no joy.

I could also hack the lights up and just use the front lens with some brackets. But as mentioned earlier keen to learn a useful skill. Will definetly consider just doing in fibreglass in case it turns into total fail.

Link to comment
Share on other sites

Has anyone here done anything with prepreg carbon fibre? I've been umming and ahhing over what to do with respect to the intake manifolds I've printed for the v12 Jag engine I have. The obvious thing to do would be lost wax casting but I'm not really interested in that. After watching those easy composites videos approx 18 months ago I've wanted to try and make something out of prepreg carbon ever since so thought I'd try and make these manifolds out of carbon. 

I sprayed the print with some high build primer and sanded it back to smooth it out. So far the biggest decision has been what to make the mould out of, have decided to give silicone a go as it's supposedly temperature stable to like 220 degrees Celsius. Will put a box of some description around the mould for support and hopefully be able to out-of-autoclave bake it in the oven to cure the carbon. Plan to import one of the easy composites starter kits with the vacummn pump etc and have a play. Hope to report back with how I get on.

20180427_193409.thumb.jpg.c10b41cdcf2bdfe0efb64ccbfde332c3.jpg

 

I stuffed up when i poured the first half of the mould and forgot to put locating dowels in to align the 2 halves, should be able to wing it though.

I should really start with a simpler shape haha...

  • Like 2
Link to comment
Share on other sites

Be careful using CFRP at high temperatures like that if it will be in contact with the cylinder head. The epoxy will be pretty close to its glass transition temperature around 90 C (depending on the epoxy you use and the cure cycle) and your parts could get quite rubbery.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...