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carboncactus
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Soric is for infusion. If you want a core, use nomex or nidaplast.
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andygtt
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Warren Couple of silly questions: Can you use pre preg as the finish layer and resin infusion on the other layers? Is soric able to be used with prepreg?
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andygtt
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All sounds very good, some of my parts take many days to lay up for resin infusion, I have basically made moulds for the entire car so some moulds are 2.5 x 2.5meters approx. I like the idea of having an oven even for infusion as I find myself putting a heater in a room in my house and using gass heaters to get it to over 40deg c, one of my moulds won't fit in the room and another won't go up the stairs without the bag breaking so I have to move it after its cured. Hardly ideal. Might make a wooden box and line it with builders corex then have a remote heater feed it, how hot do you get yours?
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morepower
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andygtt (15/08/2013)
Love the tea tray, really gives an idea of what's involved with per preg... How large are the biggest parts you make, is it practical to make large car body panels from it? Can you use soric in per preg? Never used soric.. But you can make some big parts at home if you build an oven using simple parts and take your time... I have been using a friends oven that he built and it works perfectly...He uses it for his business so it is very well made and would be quite expensive to copy. But he has it on wheels and can move it round and run it on gas or electricity! Car body parts?? I would say it is not too hard to do them in a Pre-preg. I do bike parts in Pre-preg using VTF 261 for the surface and a material from SHD called LTC250XL. The other material I use is a PRF material called RF 464 which is a good material and is a good alternative to VTF261 if you dont mind some pin holes. To be honest all pre-preg parts need a coat of lacquer anyway to protect them from UV so the cost saving outweighs the little extra work the painter has to do if you send it for lacquer. I am charged £150 for a full bike kit regardless of how good or bad the pinholes may be and the parts look amazing anyway. Just for an idea the kits I make use about 6 Linea meters of 1.25 wide material so the cost if I use the PRF material is about £300 in carbon.. Not sure how big you are thinking but the seat and fuel tank unit is just over 5feet long or about 1.8m long and the fairing is a typical motorcycle fairing size... The seat/tank is a full monocoque and self supporting so has a LOT of carbon in the back up layers to give strength...    These are not small parts.. lol..  I am building a portable oven for some of my smaller parts and have just made a simple PID controller I can connect to a 3Kw fan heater and place in a simple oven. I have used anything from two cardboard boxes inside each other to a large garden wheelie bin (clean one of course).  The controller cost about £40 for the case, PID controller and a 40Amp Solid state relay and 5 thermocouples.. The fan heater was about £30 from eBay and the only other thing I got was a remote meat thermometer to measure the temp of the mould so I have both oven temp controlled and can let the heat soak into the mould and time my cure using the mould temperature but also know the oven will not get too hot if I tried to just take the temp from the part only the oven temp may not be right.
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Matthieu Libeert
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Thanks Warren for your great way of thinking... Really like the part where you talk about costs and saving of time making prepreg cheaper!
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Warren (Staff)
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In theory you can make a jumbo jet from pre-preg carbon if you have the facilities!!!  its commonplace in motorsport, especially single seater world to see carbon composite monococques and body shells and some are done with the same equipment and facilities available to you and I. Only the top flight teams are likely to have access to decent size autoclaves and large expensive ovens, the rest will be doing it thier own way commensurate with their budget. For most of the enthusiasts and small business' here, pre-preg becomes more prohibitatively expensive the bigger the panel is. But there is no reason you couldnt make pre-preg bonnets etc if you wanted too. For most lower temperature and out of autoclave pre-pregs you can even use the Uni-Mould Mould Making System so your moulding costs needn't be any higher. In fact for most of our workshop pre-preg manufacture, the moulded products generally use a Uni-Mould based mould.
But its the cost of the carbon for larger panels that makes it less likely to appeal financially.
For example our How to Make a Carbon Fibre Car Bonnet/Hood - Part 2/3 video shows the use of normal fabrics for resin infusion.
A rough cost for the laminate on about 2sqm fabric each layer is:
3 layers of 200gsm £144
1 layer of 600gsm £60
carbon tape £60
soric £30
3kg in2 resin £45
Total £339
Plus bagging stack materials ontop but there's little cost difference in bagging between pre-pregs and resin infusion, just a swap of a couple of the materials of similar cost.
You could bring that cost right down by buying materials in bulk and by re-using your waste/offcuts but for comparison purposes that is irrelevant.
In pre-preg the laminate differs slightly as we use a surfacing pre-preg for out of autoclave use, and the 660gsm carbon would have to be replaced with a layer of 400gsm and a layer of 200gsm pre-preg as we don't have a 600gsm pre-preg.
2 layers Easy-Preg Surfacing Layer £395
2 layers Varipreg 204g £215
1 layer Varipreg 430g £126
Easycell75 £30
Total £766
As above with bulk buy and wastage.
So thats £339 versus £766. So pre-preg costs over double in this example. General rule of thumb is about double cost of raw materials.
So unless you are minted or need that extra minor weight saving and extra small percentage of strength/stiffness, then I couldnt possibly recommend large pre-preg panels to any one.
Those doing lots of carbon will get materials much cheaper than those prices above by bulk buying and using the offcuts efficiently.
Where pre-preg comes into its own is layup with smaller parts and complicated parts. You can achieve much more complicated parts with pre-preg than can be practically achieved with other methods. PLus for the smaller complicated parts it is much quicker to lay up.
An example of mine.
I first made those surrounds with Resin infusion. It would take probably 4 hours to lay up neatly. With pre-preg took 40 minutes plus was soo much easier.
Now for the DIYer, time isnt a cost factor so much, but for a business it is.
So although ive gone from about £20 of materials to £40 materials at most, ive saved over 3 hours of labour and overheads. For smaller business your actual hourly running costs could easily be between £30-50 per hour (we commonly advise people to think around £50 per hour for costing purposes) so you can see the money saved on the labour more than exceeds the additional cost of the materials so makes sense from a business perspective.
Even for a DIYer it still makes sense on small parts. Less hours spent, much easier to get the fabric in the mould, meaning less chance of bridging and less chance of ruined parts. You keep it under vacuum throughout curing so the odd tiny leak that might ruin an infused part you will likely get away with.
Warren PenalverEasy Composites / Carbon Mods - Technical Support Assistant
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Warren (Staff)
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fgayford (03/08/2013)
wozza (25/06/2013)
Any Marine grade Polyester will give good U.V protection.  Now that is news to me. I have never heard of polyester that was UV resistant. I know boat people use it as long as they cover it with paint to protect it from UV destruction.
Polyester gelcoat finishes turn to chalk if left in the sun without protection. Epoxy does as well. Unless I am missing something this doesn't right.
Also you shouldn't be using polyester resin with carbon fiber in the first place as the laminate will be much weaker than with epoxy which is what carbon calls for. I think some of the experts at EZ Composites need to chime in and clear this up before someone makes some costly mistakes.
Fred Actually wazza is right. Any marine grade polyester resin is likely to have a high level of UV stability, especially compared to epoxies, and anything lloyd registered is of a good quality standard full stop. Most clear polyester gelcoats aimed at our market are again UV stable. Its only the cheap rubbish that is unlikely to offer it. You get what you pay for. There is nothing wrong with using polyester resins with carbon fibre. It IS weaker compared to vinylesters and epoxies but it is cheap so has its place. You will find the vast majority of premade cosmetic carbon sheeting offered in the UK and europe and especially any chinese imports, are all polyester based. Also a lot of cheaper carbon panels on the market are polyester based. Sure they are not as strong as they could be with epoxies, but then they don't necessarily need to be as strong for thier intended market. Sure if you want to maximise the performance of your part with advanced composites such as carbons etc then using epoxy based (or at least a quality vinylester resin) resin will be high on your priority list. But all us carbon nutters have to accept that a large part of the "carbon fibre" market is based on its cosmetic appeal (especially in the car world) and many such people couldn't give a damn if thier carbon bonnet (well 1 skin carbon, rest e-glass) is 40% heavier than an epoxy equivilent.
Warren PenalverEasy Composites / Carbon Mods - Technical Support Assistant
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andygtt
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Love the tea tray, really gives an idea of what's involved with per preg... How large are the biggest parts you make, is it practical to make large car body panels from it? Can you use soric in per preg?
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fgayford
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wozza (25/06/2013)
Any Marine grade Polyester will give good U.V protection. Now that is news to me. I have never heard of polyester that was UV resistant. I know boat people use it as long as they cover it with paint to protect it from UV destruction.
Polyester gelcoat finishes turn to chalk if left in the sun without protection. Epoxy does as well. Unless I am missing something this doesn't right.
Also you shouldn't be using polyester resin with carbon fiber in the first place as the laminate will be much weaker than with epoxy which is what carbon calls for. I think some of the experts at EZ Composites need to chime in and clear this up before someone makes some costly mistakes.
Fred
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carboncactus
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The first one I used was Hexcel M49. 200g, 45% resin, medium temp. The cosmetics of it are top notch, probably the most cosmetic I've seen. No gaps between tows, and the thread is very square. However, it didn't perform. Ill be getting another sample soon to give it another shot. The second one is an Italian product. 204g, 42% resin, medium temp. Pretty good stuff, but its not as good as VTF, you can see the tows dip and rise. Cheap though, £30 a metre. No, not single sided. The only single sided prepregs you will find are VTF, Amber's 525 and Easy-Preg.
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