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Discussion Starter #1
I already understand that pre preg is a better choice if you are going to do structural work, but does that mean you cannot do wet lay for structural parts??
Does anyone know of any type of structural CF that was done with wet lay??

Tree
 

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Its not that simple. Matter of fact its much more involved and complex than one might think. There are many methods of wet laying carbon. One will need to know what kind of structure the part(s) are being made for, as well as the actual design of the part. If its a critical part then its a good idea to search out carbon companies that could better guide you on the carbon you are looking to make.


Couple examples of wet lay carbon parts that are structural parts......sailing masts and those long and low row boats you see in the olympics.
 

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Its not that simple. Matter of fact its much more involved and complex than one might think. There are many methods of wet laying carbon. One will need to know what kind of structure the part(s) are being made for, as well as the actual design of the part. If its a critical part then its a good idea to search out carbon companies that could better guide you on the carbon you are looking to make.


Couple examples of wet lay carbon parts that are structural parts......sailing masts and those long and low row boats you see in the olympics.
Not to mention frames on Ducati MotoGP bikes
 

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Discussion Starter #6
So possibly bad idea for say seat assembly unit?
Would pre-peg/autoclave be the only option, or would wet-lay safely work done properly??
 

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Oh yeah if done properly a wet lay with some vacuum bagging should be fine. If you have autoclave access that would be even better cause bagging can only get you so much pressure.
Keep in mind there are numerous methods for wet lay and it would be good practice to make sure one is intimately familiar with all of them for their advantages and disadvantages. Depending on what one has to work with some methods may work better than others.
If you are going to be making a mold of the sub frame you want its not much more work to make a plug for it. If going that far may as well go with prepreg if you have use of an autoclave. There is tooooooooons of stuff that can be pulled up quickly through google to help you figure outt he finer points. Think there are some composite specific forums that would be a good place to start with. Who knows you may even find someone in your area willing to do such a project for or with you. At the very least you'll have access to 100's of years of knowledge through the web sites which can't be found on here or many(if any) of your typical bike and/or car forums.
 

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Discussion Starter #8
Varium
Thanks for the good words
Winter project enroute
dont look for the short path gents, this one is gonna take a while
I am looking a something special for the 2014 GP in Texas
Babygirl is gonna have to take a side seat to her new sister :)
let the cash register ringing.... begin!

Tree
 

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I already understand that pre preg is a better choice if you are going to do structural work, but does that mean you cannot do wet lay for structural parts??
Does anyone know of any type of structural CF that was done with wet lay??
Basically as you go through the processes from pre-preg and autoclave to wet lay and vacuum bag to straight wet lay you get cheaper and also loose an element of quality control, so to make-up for this more resin is used and the parts get heavier.

The rear bodywork on my Bimota SB6 is a self supporting carbon fibre element and since this bike originates from 1993, I'd bet the bodywork is not a pre-preg autoclave structure. It is possible the bodywork was vacuum bagged, however, most likely it is just a wet-laid structure - this rear bodywork is thick, heavy and plenty strong enough.

Andrew...
 

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You want to build something like this guy does for the 1098? http://durbahn.de/Web 1098.htm

It's very possible. With laminates, layup is everything. Depending on the composite technology you can get your hands on, you could do the whole thing with a wet layup and no vacuum bagging. Don't expect too much weight savings if you do that thought. You'll likely need your layup to be thick to compensate for porosity (tiny air bubbles) weakening your overall strength. Your ability to build the layup and funds will likely be the limiting factors in your project.

Practice makes perfect. Have you ever worked with composite materials before?
 

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Discussion Starter #11
just fiberglass a year ago
I had a guy who makes C/F parts for tuner cars show me how to do it.
All of his work was wet lay, and i was interested in maybe making bodywork parts, he said too easy.
Of course he had me make a whole bunch of wet lay fiberglass parts to get acustom to working fibers and he said my work was pretty good.
He slowed down because he said getting C/F was getting harder and more expensive. So he always told me make what i want in fiber first, then C/F it (as it would further help the skill and i could cheaply see if the part is what i wanted).
It looks like now there are a whole lot of C/F dealers online now (thank you Boeing) and the choices are more abundant, but i started reading about autoclave and i want to be sure if it is absolutly necessary for structural parts?
And i get the gist "if you make it thick enough, No", but there is no talented hand that has wet laid acomparable part to and autoclaved part??

Tree
 

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there is no talented hand that has wet laid acomparable part to and autoclaved part??
As Varium said, you can get really good material with a heat blanket and vacuum bag. The autoclave will get you a more pristine material, and generally more consistent. The key to making a good material is the process control. A good vacuum bag process will yield better material than a poor autoclave process.

I think it would be a fun project, even if making a usable seat unit doesn't work out. I would make at least 1 fiberglass to test your mold for shape and fit. Then make a carbon one to practice the process and test it for strength. Test it until you break it and even if you don't break it, make a second one.
 

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I might be wrong but doesn't the direction of the weave (in the way it is 'placed' in relation to the loads) also effect the strength?
 

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I might be wrong but doesn't the direction of the weave (in the way it is 'placed' in relation to the loads) also effect the strength?
Absolutely, the weave direction has an effect, so does the material.

Carbon offers excellent abrasion resistance and compressive strength, kevlar has much higher tensile strength and lower compressive strength than carbon so often in composites weaves containing both materials are used. Likewise if you can pre-stress the carbon prior to applying the resin, even higher stiffness can be realised (only really possible with flat and straight products).

As an aside I've seen some incredibly thin stiff carbon mouldings through the years one memorable example being an OEM MV Agusta carbon key surround for the original F4 series. While the intended application of a key shroud was a total waste of the stiffness and strength of the product it was impressive as was the price.

Andrew...
 

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Discussion Starter #15
HEAT BLANKET!!!!!!!!!!!!!!!
I knew there had to be another way for the dry fiber :)

I am gonna take a swing and see what happens
Hopefully C/F will remain available in enough quantity and maybe the price may drop

Tree
 

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Absolutely, the weave direction has an effect, so does the material.

Carbon offers excellent abrasion resistance and compressive strength, kevlar has much higher tensile strength and lower compressive strength than carbon so often in composites weaves containing both materials are used. Likewise if you can pre-stress the carbon prior to applying the resin, even higher stiffness can be realised (only really possible with flat and straight products).

As an aside I've seen some incredibly thin stiff carbon mouldings through the years one memorable example being an OEM MV Agusta carbon key surround for the original F4 series. While the intended application of a key shroud was a total waste of the stiffness and strength of the product it was impressive as was the price.

Andrew...
Strand orientation, resin system, fiber properties, cure process, etc. it all matters. Composite materials are a system and like any system it is only as good as it's weakest link. With a proper design, a 2 ply weave can out perform a 5 ply tape but at 8x the cost and a 50% rejection rate for the best composite shops in the industry. It all comes down to what you have to work with. On a limited diy budget, a wet layup of low to average strength weave will work for you. However, since you likely will not have the expected and actual loads to base your design and tests on, I would error on the side of caution and make it thicker and focus on quality. It's difficult to tell bad carbon from good carbon by looking at the outside and testing can be really expensive.

poor quality = bad times
http://www.cbsnews.com/stories/2011/09/22/ap/cabstatepent/main20110203.shtml
 
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