dave33 Posted March 4, 2012 Report Share Posted March 4, 2012 Carbon fibre is carbon fibre but there is scope for a massive variation in strength and performance when it is laid up and made into a component. Singlespeed spacers will just have been made from a length of relatively simple and cheap CFRP tube but to make something like a set of bars or a frame where strength is required the layup process, fibre orientation, number of plies etc. all makes a massive difference to how the final product will behave. Seems like Santa Cruz know what they're doing but I'm still not convinced that CFRP is necessarily the best option for trials frames which often get scratched and beaten to shit. Do t be silly now, there are loads of different grades Of carbon fibre Quote Link to comment Share on other sites More sharing options...
trialsbeginner Posted March 4, 2012 Report Share Posted March 4, 2012 i will get some samples of carbon sheets tmz and do some test for you guys here it is very very strong stuff put together correctly. i say if you want to trust in carbon bike frames its not all about the material it about the prosess they use when building, testing and designing the frames. i can list a few companys whom i would never buy carbon frames from cannondale ie crack n fail lapierre ie crackierre whyte ie thats the colour of the filler they use . x lite handle bars cracked from new kenesis has anyone even looked at there carbon seat stays, just no i have seen snaps in all of these. but that doesnt mean all will snap. just saying i havent yet seen a giant carbon snapped but thats the only company i know of making there own carbon weave from carbon on reels.not prepreg or wetlay ect.. if made properly, i cant see why bike companys cannot suppy a raw frame cut in half as a show frame to let the customer see what there buying into. if this were law i think a lot of carbon bike would have never been sold. haha maybe i should warn my mate he has a fully carbon cannondale Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 4, 2012 Report Share Posted March 4, 2012 Do t be silly now, there are loads of different grades Of carbon fibre I think you'll find that, by the definition, carbon fibre is fibres of carbon. Likewise, carbon fibre woven cloth is pretty standard across the board, the difference comes in the process used to lay it up and the skill and knowledge of the people doing the work. Which is what I said. So where was I being silly? 1 Quote Link to comment Share on other sites More sharing options...
dezmtber Posted March 4, 2012 Report Share Posted March 4, 2012 haha maybe i should warn my mate he has a fully carbon cannondale if its still within warranty he will be given a new frame if it snaps. so no worries if its secondhand then keep youe eyes open for cracks. there are diffent grades of carbon makeup. the fibers are all the same. allthough there are many ways of manufacturing the fibers into a finished product. 1st you get two differnt carbon fiber sheets one weaved and one unidirectional (fibers only layed in one dirction rather than crossed) with weaved carbon you can alter the tighteness of the weave and how broad the sets of fibers. with unidirctional carbon, this type is currently the strogest type you can get, but its such a ball ache to lay. with out the weave the sheets are very fragile and break up very easily. buy layed correctly and in the right directions you need for stenght this type of carbon contains the least resin possible. carbon grades are measured in the levels of carbon to resin in the end product. a very good strong and light carbon contains more carbon to resin. a weaved carbon wil contain more resin due to the gaps betwwen the cross over in the weave. the resin content of carbon is reduced by bakeing the product at 200 degrees and applying pressure in a autoclave to squese out the resin between the carbon. a lot of cheper carbon producta are produced using a wet lay teqnuiqe. where the carbon i just layed onto a mould just like paper mashe. and left to dry. most bike frames are made in the same way, only diffrence is they then inflate massive condoms inside the frame to apply pressure and then ar backed in an autoclave to allow the resin to thin up and flow out of the carbon mould. carbon sheets for space shuttles are made up and then set under a press putting 40 tons pressure on the sheet. Quote Link to comment Share on other sites More sharing options...
dezmtber Posted March 10, 2012 Report Share Posted March 10, 2012 here is my very own carbon test just for you lot i will have to do a 3mm thick alloy one the same to show the difference but even i was shocked at the results Quote Link to comment Share on other sites More sharing options...
Luke Rainbird Posted March 10, 2012 Report Share Posted March 10, 2012 Fair play for going and doing it off your own back, though it's not particularly representative of a carbon frame/fork etc. A flat, unsupported section of sheet will react pretty differently to a formed unit. I'll see if I can dig out an old image of a chap who'd built his own carbon PC case. it was around 1-2mm thick but supported him standing on it comfortably which was pretty cool (just the carbon shell, no internal supports etc) Edit; Couldn't quite find the image I was after, but here's the guy's daughter on the box; Note; this if after he'd cut a load of holes in the case too Tough stuff Quote Link to comment Share on other sites More sharing options...
Topsy Posted March 10, 2012 Report Share Posted March 10, 2012 and I always thought carbon fibre dust was so unhealthy that you should only work with it outside with mouth protection etc. etc. ^^ Quote Link to comment Share on other sites More sharing options...
ZeroMatt Posted March 11, 2012 Report Share Posted March 11, 2012 Full project log if anyone's interested. However it's still not finished yet. Quote Link to comment Share on other sites More sharing options...
King C Posted March 11, 2012 Report Share Posted March 11, 2012 (edited) I would do his daughter in a couple of years time EDIT: To be a little more constructive, I would agree that by definition, carbon fibre is carbon fibre. Of course you can chose the orientation of the fibres etc but I wouldn't call them grades like you would a metal. When the design of the product has been finalised, a layup can be designed to suit, whereas a metal (and a specific grade) is chosen. Grades are standardised whereas layups are designed. Edited March 11, 2012 by King C Quote Link to comment Share on other sites More sharing options...
dezmtber Posted March 11, 2012 Report Share Posted March 11, 2012 i used the 40 ton press to make that 3mm thick carbon sheet. none of the bike frames u see are made using the same kind of pressure to squeese out the resin. i dont think i could have made a stronger piece to test with Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 11, 2012 Report Share Posted March 11, 2012 The pressurisation isn't done to squeeze out the resin... I would also imagine that most carbon frames are made with the aid of bladders and autoclaves so they do involve temperature and pressure during the curing process. Quote Link to comment Share on other sites More sharing options...
dezmtber Posted March 11, 2012 Report Share Posted March 11, 2012 as far as i knew an auto clave cannot produce the same pressure as a 40 ton press. they work on making a vacum in the space inside to apply pressure, but 40 tons would be some auto clave Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 11, 2012 Report Share Posted March 11, 2012 Can't be arsed arguing but your logic seems flawed. Quote Link to comment Share on other sites More sharing options...
Luke Rainbird Posted March 11, 2012 Report Share Posted March 11, 2012 Sucking it out vs squeezing it out, they're again pretty different. As I said, fair shout for getting off your arse and having a look/go. That's genuine, not sarcastic praise for actually thinking about stuff, hopefully it's coming across that way Again though, it's an unsupported flat sheet, which a bike frame isn't. Standing on a thin flat sheet of alu will bend it. Standing on an alu tube of similar thickness will hold up much better. There's more to it that purely the material itself, the way it's put together and the overall form of the thing comes into play in huge amounts with something so complex as a bike frame, which is why companies spend so much time, effort and money on putting the work in to getting it right 1 Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 11, 2012 Report Share Posted March 11, 2012 as far as i knew an auto clave cannot produce the same pressure as a 40 ton press. they work on making a vacum in the space inside to apply pressure, but 40 tons would be some auto clave There seems to be some confusion over what an autoclave does (high temperature and pressure).For most cases the part will be put in a vac bag first which involves removing all the air from around the component. Depending on the type of material and lay up procedure this can then either be cured at low temperature in the absence of high pressure or put in an autoclave where high pressure and temperature is used to aid the curing process and produce a stronger part. Internal bladders are used for hollow sections to stop the component from collapsing in the vac bag or from the autoclave pressure. Quote Link to comment Share on other sites More sharing options...
casualjoe Posted March 11, 2012 Report Share Posted March 11, 2012 Squeezing out the resin just makes it nice and light Quote Link to comment Share on other sites More sharing options...
eskimo Posted March 11, 2012 Report Share Posted March 11, 2012 Still wouldn't touch any trial product made from carbon. But would consider a Santa Cruz frame. Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 11, 2012 Report Share Posted March 11, 2012 Squeezing out the resin just makes it nice and light The resin doesn't get squeezed out at all though! It has nowhere to squeeze to as it's in a sealed vac bag. If anything, the compression squeezes the resin into the fibres to increase the strength and ensure consistent properties throughout. Quote Link to comment Share on other sites More sharing options...
casualjoe Posted March 11, 2012 Report Share Posted March 11, 2012 Yea fair one, it's a little different when you lay up the carbon by hand though. I used to build yacht decks out of the stuff. Quote Link to comment Share on other sites More sharing options...
dezmtber Posted March 11, 2012 Report Share Posted March 11, 2012 i know how a autoclave works and how to use one and the procesure. although i havent done the math on just what 150psi vacum pressure will apply directly on the carbon and resin in a vac bag. but i am saying is cabon in a autoclave at 150psi vac. surely wont be going under the same as cabon under 40 tons plates. both plates and autoclave have heat on them and a vac bag so its only the pressure thats different good carbon consists of two things, no voids (air trapped) which weave is bad for and uni diretional is very good for. and low resin content, the more carbon to resin the stronger. i only know a litte about carbon, i only know how to make the stuff as my old job before bike mechanic. i would take my hammer to the lapierre chainstay we have snapped at work (not the 1st we now dont deal lapierre) but they want it back Quote Link to comment Share on other sites More sharing options...
sstein Posted March 12, 2012 Report Share Posted March 12, 2012 I think this is silly. Carbon is no doubt stronger than alu or steel on paper and in tests like that, the problem lies elsewhere. If I had a bad crash on a steel frame, as long as it did not crack i would still ride it. If I had the same crash on a carbon frame I would be very worried as most damage would not be visible. Also a bad scrape can ruin carbon where steel or alu would be fine. Carbon is amazingly light and strong but I think it is better off kept to uses where it will not constantly be smashed into stuff. Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 12, 2012 Report Share Posted March 12, 2012 150psi vacum pressure Uh huh. What's a vacuum again? To put that figure into perspective 150psi will induce a pressure of over 105 tons per square metre. Quote Link to comment Share on other sites More sharing options...
Matt Vandart Posted March 12, 2012 Report Share Posted March 12, 2012 I thought the pressure had to be below 14psi to be considered even a partial vacum. Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 12, 2012 Report Share Posted March 12, 2012 I thought the pressure had to be below 14psi to be considered even a partial vacum. Standard atmospheric pressure is about 14.7 psi and according to Wikipedia a 'low vacuum' is considered between 14.5-0.44 psi so quite a range! A perfect vacuum is of course 0 psi. Don't think 150 psi can be considered a vacuum... Quote Link to comment Share on other sites More sharing options...
dezmtber Posted March 12, 2012 Report Share Posted March 12, 2012 so what tons per square meter does an autoclave work at? i really dont know the figures. i just know that it makes a vacum. i am just saying i dont belive air pressure can be stronger than pysical pressure coming from an set of 4 pistons acting on a smaller area than a pump acting on a large chamber. Quote Link to comment Share on other sites More sharing options...
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