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ant...
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So I've been working on producing a carbon fibre coffee cup for many years, I want it to be perfect and its almost there. For the past 2 years I've had the project on the back burner having spent many thousands on equipment and tests. But last week watching the How Its Made featuring the Bugatti Veyron, I saw how their carbon nose cone always comes out with voids in tights places and that these areas were repaired to produce a flawless finish. That made me think my process might be good enough and I can finish my cup with a few repairs. These images show how my cup is one solid piece but the outside is always susceptible to tiny bubbles or sometimes voids, the inside is almost always perfect. My Process - The alloy mould is secured in a vacuum chamber while infusion resin is pumped from the mixing container into the mould from its base, this enables the cup to be one piece with all smooth sides and the vacuum chamber limits bubbles & voids. My next test will include curling the mould in a high pressure oven maybe 100psi (pressure cooker LOL). But I've tried loads of ways to get a 100% perfect result and id become disappointed until I saw the Bugatti repair process. With a little help I mights just get a finished mug... Question - Can these voids be filled? any suggestions? Im guessing sand the holes back to remove any release agent, maybe with some acetone and fill with a syringe of general epoxy. then rub it back to a perfect round finish.
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ChrisR
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Other than just leaving the vacuum on for longer before infusing and warming the fabric before layup/infusion I can't help on that front. It looks reasonably OK tbh. Just a couple of questions on the project on the whole though.... I assume you're using high temp resin & elevated post cured? Does it have a liner to prevent anything nasty from the resin getting into the drink? (99.99% of epoxies are not foodsafe - I only leave a 0.01% as I'm sure someone has come up with one) Does it come with a insulating holder as the carbon will conduct the heat straight to your hands in seconds & it would act as a heatsink for the liquid inside? I'm sure you've already considered these but just interested in how you've overcome them... Chris
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ant...
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Hi Chris Actually I might try heating the alloy mould and the material, I've not tested that yet, Thanks. The vacuum chamber is very good and I can 100% guarantee that no bubbles come through the peristaltic pump so its more likely that they are voids, thats why I'm hoping the pressure cure will help. Resin is infusion fast, not high temp and after and I cure for a few weeks. When the cups finished the rim and base will be fitted with aluminium rims, this will help stop people putting the cup in the microwave, which is the only risk I've found. Heat insulation 4 layers of 600 carbon fabric(chosen for its nice weave pattern) in testing the cup keeps hot 50-75% longer than a normal pottery coffee mug and it feels great in the hand. Food safe - The cup will go to Veritas when finished, its a piece of artwork though not your average brew cup. Even if it can't be sold as a beverage holder I'm still going to finish the project if I can keep thinking of ways to improve the process. I can get stainless steel inserts for £2 but then you wouldn't be able to see the inside.
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wandfisch
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Hey I'm not sure if I can follow you ChrisR, why should epoxy not be foodsafe ? Epoxy itself is inert to most things, some epoxy are although used in chemical tank building (but these are additionally stabilized ones). and with a fast google research I found that there a food safe epoxy coatings for self-made cups, so why should epoxy not be foodsafe in general. And the thing with the temperature doesn't seem reasonable to me too. why should a CFK part with epoxy matrix give away it's temperature so fast, as far as I learned this would go against every scientific data of thermal conductivity/heat transfer coefficients ? if you look up those heat transfer coefficients you'll see that CFK parts don't give away heat so fast as you assumed. And ant... has made the pracitcal test which seems very reasonable too me. Michael
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ChrisR
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CF is very thermally conductive (about twice that of steel), GF is very insulative (about 1/100th of steel), resin is about 2/1000th that of steel To use a resin which will be in contact with food and for human consumption you need to have it certified food safe, most epoxies are not certified - hence the comment. Also, while some resins may be safe, they may only be "safe" for dry food only. Add in liquid and heat they are two unknowns. Epoxy is not inert once cured, if you heat it higher than it's previous cured temperature it undergoes further chemical cross linking, heat it past its HDT / Tg and it undergoes a chemical breakdown.
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Matthieu Libeert
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I follow ChrisR on this one... pouring hot beverages in an epoxy cup isn't always a good thing...if not postcured, put your cup in the oven at 80°C, remove it and you'll see you'll be able to bend it. It will also feel sticky and have some smell...proper postcure is the least you can do, use a high thermal resin is even better. Seems like a good project though! but I would never buy something like that for safety reasons... the solution with an insert would solve everything.
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ant...
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Hi Matt & thanks for your input Trust me I've done all this testing and I've been drinking out of my mug for years and its more than fine, when its full of hot coffee it feels lovely in the hand and the cup resonates when empty. The big risk is putting the cup in the microwave, over 45 seconds in the microwave and the cup does start to melt, smell awful and then I wouldn't trust it top drink out of. My objective - This is Not a business venture, from the pics you can see I've tried to produce a piece of art, a perfectly encapsulated carbon fibre mug with a polished outer surface and it would cost into the hundreds to sell, not something you would chuck in the dishwasher. I could of cut an 8cm length of CF tube and stuck it on the outside of a cup if all I wanted was to sell a mug. Ive had lots of offers from advertising agencies wanting to back me on this project, it seems people who are into carbon fibre are dying to get hold of a piece of everyday household objects, at the moment if you want something nice out of CF its got to be car parts. But if I went down the business rout that would mean id have to work hard on finishing it and actually produce them at some point and thats not what I want to do as a job, I just want to produce a few mugs and see what people think of them. Thanks for the GC50 tip, ill try that :-) BTW - Can you buy high temp infusion resin???
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ChrisR
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yes, check the datasheet on the resin you currently use then approach a resin manufacturer/supplier directly as it won't be something that's stocked at EC/ECF/another online place. You could try Gurit, Matrix Mouldings in Bristol, Mouldlife (Huntsman resins) or Marineware in Southampton - obviously there are many other places but it's a place to start.
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ant...
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ChrisRThanks ill look into finding high temp infusion. I knew that their were an infinite amount of resin variations but I didnt think a hobby guy like myself could ever afford to have a specific resin made. Matthieutje65Ive looked at the GC50 video and I think that is the stuff that Matt from CarbonMods gave me, before it had a name. I was trying to use it as a gelcoat but I've given up on that method and I'm now going to spray paint 2pack clear for the finish. GC50 looks like a great thick resin to hold in place, but my holes are so small I think even an infusion resin would hold. Im lucky that I built all moulds with engineering machines so after repairing the cup I should be able to spin it on the lathe for a perfectly flat uniform surface. The handle will be a bit harder. Im still hoping curing at 100psi will help remove voids. When I release the vacuum the infusion resin drops 5mm down the mould, theirs something about the surface tension on the outside that makes it susceptible to voids. Food Safe - This is an area I dint want to talk about here because anyone who has worked with any 2 part resin knows how noxious they are. The food safe varnish/epoxy they spray inside alloy drinks cans is a closely guarded secret and I've had no luck finding any info on how or where to find them, but I might have more luck with the Veritas people or maybe those resin manufacturers that ChrisR mentioned. It has been 2 years since I've searched though.
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ant...
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Ive taken pics off the TV to show you what was shown on the How Its Made - Bugatti program.  The sanding process has shown the voids on the rear of the Veyron, these are actually very similar in size to my cup, perhaps these can be filled with just the 2 pack lacquer.  Here you can see a lady marking up a void on the bumper of the Veyron and actually its a bit of a mess if it were to be left, so its apparent to me that they are able to repair some severe voids, good enough for the bonnet of the most expensive car in the world. So I should be able to repair the tiny voids on my mug. The CF steering wheel is full of voids and thats a piece which we would expect would need to be perfect. What the CF cladded supercars do have that my mug doesn't is large vast areas of absolutely perfectly laid material, beautiful curves, patterned surfaces, all of which move your eye away from a tiny repair. This has given me hope for the possibility of repairing my mug to a perfect finish.
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