Delinquent
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| posted on 17/7/07 at 01:50 PM |
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any composite pro's on here?
Hi All,
I'm looking for a bit of assistance with some composite planning, wondering if there are any pro's on here that could help?
I have fairly good experience of working with both glass and carbon fibre, and a reasonably knowledge base, however not to the point where I am
confident gauging strength for given thickness / weights etc when working on a large scale. As I am trying to build something very light for its size
I don't want to go overkill and heavy, but I don't want to end up with something lethally fragile either!
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twybrow
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| posted on 17/7/07 at 02:02 PM |
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I could possibly help. Give me some more details and I'll see what I can do.
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Hammerhead
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| posted on 17/7/07 at 02:08 PM |
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mmm sounds interesting 
Maybe if you are more specific people might be able to make suggestions.
But heres my 2p:
If it was me i'd consider for non stressed body panels. 3 layers of 300gsm carbon. 1st layed in the vertical plane, 2nd + 45 degrees to vertical
and 3rd - 45 degrees to the vertical.
alternative is a sandwich of 1 cf, layer of core mat or ali honeycomb and another layer of cf.
I'd expect that you will have to layer up a bit thicker in areas of stress or fixings and add ribs over areas such as bonnet etc.
I'm no expert but the above would seem logical. I'm only halfway through my haynes competition car composites book!
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Delinquent
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| posted on 17/7/07 at 02:12 PM |
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thanks for the reply.
Basically I am looking to learn more on determining thickness's and weight / type of carbon cloth & reinforcements for the majority of the
bodywork, as it is a given that this will always be carbon. Easiest way of describing the project would be GT40 / Ultima like in build style - clam
shell front and rear with central tub. This bit I know I could make, but I think I'd make it heavier than needed, & over-engineered to
compensate for my uncertainties.
What I'd like to consider as well, is a carbon semi monocoque. Originally this was my plan but my knowledge is severely limited in the
structural side of large scale composites so I started to head down the spaceframe route - but really, It would be nice to do it
"properly". Obviously then we are talking re-inforcements with other materials, thick layups etc. Lost at the starting post would be an
adequate description....!
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Delinquent
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| posted on 17/7/07 at 02:15 PM |
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quote:
If it was me i'd consider for non stressed body panels. 3 layers of 300gsm carbon. 1st layed in the vertical plane, 2nd + 45 degrees to vertical
and 3rd - 45 degrees to the vertical.
LOL - that's my standard layup for my RC aircraft, (only in 80gsm cloth!) and my preferred method - I wasn't sure if this was enough or
not even going up to 300gsm for general bodywork. A friend suggested just 2 layers of 300gsm but that seemed... a bit flimsy!
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Hammerhead
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| posted on 17/7/07 at 02:25 PM |
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quote:
Originally posted by Delinquent
quote:
If it was me i'd consider for non stressed body panels. 3 layers of 300gsm carbon. 1st layed in the vertical plane, 2nd + 45 degrees to vertical
and 3rd - 45 degrees to the vertical.
LOL - that's my standard layup for my RC aircraft, (only in 80gsm cloth!) and my preferred method - I wasn't sure if this was enough or
not even going up to 300gsm for general bodywork. A friend suggested just 2 layers of 300gsm but that seemed... a bit flimsy!
2 layers of 300gsm will be flimsier in one direction over another whence laying one +45 and one -45.
Some rowing boats are built that way so I know they are strong, you may find that you need core mat in some places but not others.
Do a search on here for composite monocoques. It will put you off. Also search syd bridges posts, apparently he has been there and done it with cf.
Interestingly I know that a rear clamshell off a lotus elise S1 is quite heavy, due to being made by hand with a wet layup. I also have a front clam
off an elise s2 and it is very light even though it is grp. This is because the s2 elise uses resin infusion, os there is no excess resin in the
composite, it is very flexible compared to the elise s1 clam. Probably 50% lighter.
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twybrow
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| posted on 17/7/07 at 02:46 PM |
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quote:
3 layers of 300gsm carbon. 1st layed in the vertical plane, 2nd + 45 degrees to vertical and 3rd - 45 degrees to the vertical.
You should always aim to have a 'balanced' and symmetrical layup or else you will end up with a pre-stressed panel anyway...
I wouldn't try to build a composite chassis at home. You would need some major tooling and space just to accoodate the kit, let alone the
processing equipment required to prodcue a very high quality (high fibre volume fraction) composite.
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twybrow
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| posted on 17/7/07 at 02:49 PM |
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Remember strength and stiffness are two very different properties. Thickness adds stiffness, hence if you want a stiff/light structure, use a
lightweight core (balsa, PVC foam etc).
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Delinquent
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| posted on 17/7/07 at 02:59 PM |
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quote:
Originally posted by twybrow
quote:
3 layers of 300gsm carbon. 1st layed in the vertical plane, 2nd + 45 degrees to vertical and 3rd - 45 degrees to the vertical.
You should always aim to have a 'balanced' and symmetrical layup or else you will end up with a pre-stressed panel anyway...
I wouldn't try to build a composite chassis at home. You would need some major tooling and space just to accoodate the kit, let alone the
processing equipment required to prodcue a very high quality (high fibre volume fraction) composite.
OK, think we'll forget the chassis again. Seems a shame to, but I'll bow to superior knowledge every time! I'm building a over-sized
double garage specifically for the project build, but conceed it's not something I want to risk getting wrong. Reading some posts on here on it
as suggested would seem to reinforce that!
I've been reading up on VIP systems, think it might be something I may invest in. It certainly would be worth the investment for the weight
saving, as power seems to be significantly more expensive!
I've been looking for evening courses on composites but haven't got very far yet.
[Edited on 17/7/07 by Delinquent]
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twybrow
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| posted on 17/7/07 at 03:07 PM |
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The chassis is a project for several years down the line. You would need to be bloody good at design/FEA as well as tooling design, composite design,
automotive design etc etc etc!
VIP (vacuum infusion, VARTM, etc) would be a great process to do at home. It takes relatively cheap kit to set up, you can use a homemade single sided
tool, and it can produce high quality parts.
It would be worthwhile doing as much background reading as you can, for the processes, materials, setup etc.
Try NetComposites.
I would be wary of an evening course - usulally they are quite a lot of money and are a generic course. If you already have some experience, you may
not be challenged. Again, check out the website, lots of useful links.
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Delinquent
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| posted on 17/7/07 at 03:21 PM |
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quote:
Originally posted by twybrow
The chassis is a project for several years down the line. You would need to be bloody good at design/FEA as well as tooling design, composite design,
automotive design etc etc etc!
VIP (vacuum infusion, VARTM, etc) would be a great process to do at home. It takes relatively cheap kit to set up, you can use a homemade single sided
tool, and it can produce high quality parts.
It would be worthwhile doing as much background reading as you can, for the processes, materials, setup etc.
Try NetComposites.
I would be wary of an evening course - usulally they are quite a lot of money and are a generic course. If you already have some experience, you may
not be challenged. Again, check out the website, lots of useful links.
I think you are definitely right on the chassis. The real bugger is I know someone with all the tools, info and knowledge to do the job, but they are
utterly, utterly disinterested in both their job and my project! Couldn't even get him to commit to offering any advice on the bodywork let
alone the Chassis!!! 
I've already got the vast majority of the equipment for the VIP, got a couple of vac systems, one high flow . low pressure and one high pressure
/ low flow, which combined and controlled make a great setup for layup. (not what either was intended for, but you have to improvise don't
you!)
Thanks for the link, I'll head over and get reading. I was thinking of the course purely because I tend to learn better when being shown and
doing hands on work, but point very much taken - no point spending money to cover what I already know.
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Hammerhead
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| posted on 17/7/07 at 03:35 PM |
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also get the competition car composites book bt haynes from amazon, only about £10.
Also have a look at dpcars.net for carbon bodywork.
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CAD Monkey
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| posted on 17/7/07 at 03:55 PM |
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You could also try here:
http://www.bayarearidersforum.com/forums/showthread.php?s=c7e18ea84d5028e0b62652cd2ac032cc&threadid=145975&perpage=15&pagenumber=7
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twybrow
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| posted on 17/7/07 at 04:43 PM |
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Or here....
http://www.eng-tips.com/threadminder.cfm?pid=327&page=6
A useful thread perhaps...
http://www.eng-tips.com/viewthread.cfm?qid=152408&page=6
[Edited on 17/7/07 by twybrow]
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Volvorsport
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| posted on 17/7/07 at 05:04 PM |
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well , until syd barges in - i say you can do it .
Take a trip round Darrians factory and youll see , its not that much harder, only lots more preparation .
www.dbsmotorsport.co.uk
getting dirty under a bus
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Syd Bridge
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| posted on 18/7/07 at 07:35 AM |
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quote:
Originally posted by Volvorsport
well , until syd barges in - i say you can do it .
Well, I don't know what you are inferring!
You can do anything you want if you put your mind to it.
I'd just be wary of resin infusion, unless you have a lot of hands on experience. It's very prone to dry and rich spots of resin.
Prepreg and a home made oven can work.
Regards,
Syd.
I'm off now to 'barge' about the Solent in yachts for a few days. Corporate entertainment and all that.
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Delinquent
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| posted on 18/7/07 at 08:20 AM |
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Cheers for the further thoughts All good stuff!
The dry / wet loading with VIP is something I had read about originally and one of the primary reasons I hadn't gone into it before, However
with this project the thought of hand layup is not one that particularly endears itself, and I'm prepared to practice, lots
Home made oven and pre-preg, I've never looked into pre-preg at all, as I assumed the tooling for the moulds would be vastly more difficult and
temperatures prohibitive - will do a bit of reading as well as for the smaller parts it could be interesting to try something else new, but
temperatures used? thought they were rather high for a home build affair?
Syd, you mind me asking where abouts you are? I'm a stones throw from the solent... a small stone that's not been thrown very hard.
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Syd Bridge
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| posted on 20/7/07 at 11:02 AM |
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I'm on the south side of the Solent, mostly. Sometimes on top of it, sometimes in it, or getting sprayed with it. Most of the time trying to
avoid the 'muddier' regions of water.
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Delinquent
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| posted on 10/9/07 at 07:13 PM |
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You know those really annoying people who come onto a forum, ask loads of questions, get loads of really good advice, then choose to ignore it
all...
...
...ermm...oops!
I've just found out that my brother may well have access to someone who not only has FEA software, but actually understands it, is qualified to
read the results and even make comment on the design.
so a semi-monocoque may just be back on the cards here. I say may as I'm still a bit nervous about it all, but this is going to be a once in a
lifetime build (I know that for a fact - the wife told me so  ) so I may as well give it my best shot. I can always change back to lumps of steel
if the chap comes back with the results laughing like a hyena!
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