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M Hathiyari
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Hi i plan on making a Roll Wrapped carbon fiber tube of 90mm ID and 97mm OD.I was planing on using 12k 400gsm plain weave Carbon fiber material for the same but i am concerned that the cloth will not conform well to the mandrel at the time of wrapping.I plan to vacuum bag after wrapping it manually . So will 12k 400gsm plain weave cloth work or do i need to change the weave/cloth? Please help
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Dravis
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I do not think you will have much trouble using 400gsm plain weave on a 90 mm mandrel -- keeping the ends of the fabric in place while bagging it will be the biggest challenge, I would use shrink tape for that.
"Sapere Aude"... Dare to KNOW!
The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...
103% of all people do not understand statistics...
Do not adjust our mind, theres a fault in reality :-)
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VVS
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How long is the tube going to be and is it a parallel tube.
first thing I made was 100mm parallel tube and had problems removing the mandrel after curing.
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M Hathiyari
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@Dravis Thank you Could you please elaborate on how the ends of the fabric would displace and why shrink tape would be more advantageous? Also at present i dont have acess to an oven for curing,plan to use Room temp curing Epoxy.Can we use shrink tape at room temp? @VVS if by parallel tube you mean straight rod yes it is It getting stuck to the mandrel is one of my biggest fears.Hence i have decided to wax the mandrel then roll a layer of release film and then start the layup.Since the mandrel is waxed it will be easy for the release film to conform to thus eliminating wrinkles. What do you think of this idea? Any other techniques and suggestion welcome.
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ChrisR
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One of the biggest problems you will have is removing the mandrel, one method is using a metal mandrel, laying up the fabric and doing a heat cure with shrink tape on the outside. The oven is critical phase of the cure. The metal mandrel then heats up and EXPANDS, the composite cures and once the heat is removed and the thing cools down, the mandrel contracts and essentially de-moulds itself because the composite doesn't contract as much during the cool off. For a smooth finish (although I haven't tried this myself) you could try using heat shrink tubing placed over the laminate, then use a heat gun to shrink the tape down evenly over the part. The finish then MAY be OK, but you would have to experiment.
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VVS
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I can answer alot of your questions as ive been and tried them.
you may have less problems than I had due to the very thick wall you are producing, I only wanted a 1mm wall thickness.
I used a 450mm long x 100mm dia polished alloy tube as the mandrel to produce a 400x100 tube and this gave me my first problem of not enough over hang to make working comfortable so give yourself a little extra mandrel length than you think.
first trial was waxed mandrel, total fail and could not remove the tube.
second was easy lease plus un-perforated film and again total fail.
third trial was Vaseline plus un-perforated film and total success.
first trial was using heat tape and hot air gun the rest were using shrink tube and hot air gun.
only issues with the shrink tube were its expensive and could give a few small faults to the finish due to the shrink tube being supplied flat, this causes uneven shrink at the folds when shrinking.
other issues are putting too much heat into the work, its very easy to do this and causes the shrink tube/tape to melt (total fail in finish) and causing the resin to boil again complete scrap.
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mep12rid
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Hi VVS Any idea why Vaseline works better than most of the commercially available release agents? Have you tried or know off other release agents? What about high temperature resistant grease? PS: Couldn't stop myself from commenting 
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Dravis
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I think perhaps Vaseline forms a slightly thicker layer on the mandrel, leaving some room for movement when the CF tube has cured.
I know this sounds a bit far fetched, but have you considered using an aluminium tube for the mandrel ? If you heat the CF tube slightly from the outside, and cool the Alu tube, by putting one long end in ice water, the CF tube will not shrink, but the alu tube will.. That may be enough to free the CF tube from the mandrel, even with only a thin layer of release wax or chem lease ..
"Sapere Aude"... Dare to KNOW!
The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...
103% of all people do not understand statistics...
Do not adjust our mind, theres a fault in reality :-)
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VVS
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Unsure why the Vaseline worked when the others didn't, Paul at EC put me on to it. I expected to wrap the tube and the simply tap the carbon off BUT it was solid. You have to be able to brake the initial key that is formed by the curing process, i tried freezing it, heating it and smashing with a block NO JOY but vaseline gave no problems. will post picture when photobucket issues sorted.
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Dravis
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@VVS
With your method of using heatshrink tubing you start off wrapping a relatively cold Aluminium mandrel. then heating the entire thing to a high temperature (to activate the heatshrink tubing/tape you will be well above 100 degrees)
The tubing shrinks, and the Alu mandrel expands (more than you would think)!, and since both shrink tape and especially the tubing is elastic, it will keep a tight wrap on the CF/resin as the mandrel cools down, keeping the CF tube tightly pressed against the mandrel. Which is all good, from a curing point of view, but the heat also deteriorates the thin layers of wax or chem release, and may distort the combination of release film and wax/release to the point where it locks the composite into any microscopic imperfection in the mandrel.
It is quite possible that cooling the mandrel will not shrink it enough to have any effect on the CF tube, a 1 mm tube will still be a bit elastic on the circumference, and so it just stays attached to the mandrel.
As I said, I think the vaseline works because it forms a thicker layer, and in effect also "lubricates" the inner surface of the release-film, making it possible to slide the tube off the mandrel, wax or chem-lease does not have that "lubricating" effect.
"Sapere Aude"... Dare to KNOW!
The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...
103% of all people do not understand statistics...
Do not adjust our mind, theres a fault in reality :-)
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