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Old 02-19-2018, 10:36 AM   #11 (permalink)
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Why carbon fiber it's always made with epoxi resin together ? Why not other resin or composite?
Aptera car shell had good resistance to a hammer impact test, made in a silica-based fabric composite. It deformed a little and returned to original shape, dissipating energy.

They could create a new carbon fiber, with other composite together, to behave with some of the energy dissipating approach.


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Old 02-19-2018, 10:50 AM   #12 (permalink)
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it isn't always epoxy, there are other resins and binders in use. Epoxy is generally used in the home-manufactured parts because epoxy is not as stringent to control , less toxic, available, cheaper.

I just don't see anybody with a 4 ft x 4 ft x 4ft oven in their backyard to do exotics or ceramic.

remember when GM shaves a buck from each car they make, it is a multi million dollar annual profit.
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Old 02-19-2018, 10:52 AM   #13 (permalink)
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Quote:
Originally Posted by rmay635703 View Post
BMW and other 3rd parties have been stating for 10 years that fiber can be produced at the same cost as steel.
I could of sworn BMW said all their cars would be CF in the near future.

Looking that up I found this article instead.

BMW is selling its stake in SGL carbon fiber joint venture
November 24, 2017
http://www.autonews.com/article/2017...bonfiber-stake
Quote:
FRANKFURT -- SGL Group said it would gradually buy BMW's stake in their joint venture that produces carbon fiber.

BMW said last year it was limiting its use of carbon fiber and turning to cheaper lightweight materials such as aluminum and steel for its biggest selling cars to keep profit margins high.
Steel is not going away without a good fight, and aluminum is here to stay.

There is a future for CF, just not going to be a slam dunk we once thought it was going to be.
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Old 02-19-2018, 01:38 PM   #14 (permalink)
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I think I'd rather see cars made from more wood than carbon fiber. As stated by others, the sharply reduced usefulness of recycled CF is part of the reason. There's less entrained energy in a part made from wood, and you can engineer wooden members with known, predictable strengths and yields.

It wouldn't shatter as abruptly as CF when it fails, either. I think it's completely within the scope of existing technology to engineer wooden structural chassis members that can contribute to predictable crash force dissipation.
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Old 02-19-2018, 01:44 PM   #15 (permalink)
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Did you watched these videos (since it was in the very end of page 1 thread) ?







I believe a autoclave made a big difference. But I would like to understand why, what it do to the carbon filaments, or if do some extra thing just to the epoxi resin. It wasn't important they would not use.
It carbon fiber without a autoclave it's weak, not really rigid, why take the expanse of carbon fiber fabric sheet ?

There is a intermediary process, a oven and so without high pressure of a autoclave, but just high temperature, like the one used for produce this carbon fiber chello :


So I conclude there are 3 qualitt degree for carbon fiber shaping, not considering the quality of the fabric sheet.

1-Non autoclaved (trash or almost) and nohigh temperature : Produces trash carbon fiber.
2-Hight temperature (not sure if high as in a autoclave : Intermediary rersults.
3- Autoclave treatment, with high temperature and high pressure combined : Produce true carbon fiber ressistance.

Steel reinforced concrete I can understand, since the rigid steel and the flexibility of steel under high forces make the concrete stronger, as a skeleton makes our body stronger. But carbon fiber... if the carbon filaments of the carbon sheet do not get rigid, the only thing to make the final piece rigid is the epoxi resin. So the rigidity would come just from the resin and nothing more.

I know there is more things, like forces of tension and traction. But we must or art least should expect rigidity for carbon fiber.
People said carbon fiber can be up to 0 times stronger than steel, but all tests I saw was only up to 3 times stronger. I wonder if 10x stronger are reality or just talk.

Is the comparisons based in carbon fiber of same weight of a piece of steel, or based in the same tickness of a piece of a steel piece?

I'm laughing hard with this video, since the carbon sheet looks like a papersheet after epoxy cure :

https://youtu.be/243L3yeoe0c?t=764

Is he making carbon fiber or preparing to cover a book with protective plastic ?
The guy said it's because it'sw just one sheet bu a single sheet steel would never be such flexible. And if the made a 3 layers sheet, it would be flexible if was 3 times larger.

I challenge anyone to prove to me that these home made carbon fiber are stronger than steel. If even the carbon fiber bikes was a joke... worse for impact, for pression of weight and for drill and cut.

Quote:
Originally Posted by Piotrsko View Post
it isn't always epoxy, there are other resins and binders in use. Epoxy is generally used in the home-manufactured parts because epoxy is not as stringent to control , less toxic, available, cheaper.

I just don't see anybody with a 4 ft x 4 ft x 4ft oven in their backyard to do exotics or ceramic.

remember when GM shaves a buck from each car they make, it is a multi million dollar annual profit.

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Old 02-19-2018, 06:08 PM   #16 (permalink)
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One more evidence that home made carbon fiber it's a garbage, if compared to the proposed 4x stronger than steel clains we always heard on TV.



The usual lame crap excuse many carbon fiber home made people said is : It have just few layers".

But in this video, in you response to the comments, the guy said it had 3mm or 4mm.
Honestly if was a 3mm or 4mm steel plate it would not broke by a person with strong hands.
And if carbon fiber is at least 3 times stronger than steel, it's like he was broking a 9 mm or 12mm tick steel plate at least.

I still challenge someone to prove me that a home made carbon fiber is stronger than steel. Right now for me, based in these videos, it's just crap.
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Old 02-19-2018, 06:31 PM   #17 (permalink)
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Quote:
Originally Posted by All Darc View Post
And if carbon fiber is at least 3 times stronger than steel, it's like he was broking a 9 mm or 12mm tick steel plate at least.

I still challenge someone to prove me that a home made carbon fiber is stronger than steel. Right now for me, based in these videos, it's just crap.
Strength claims are based on weight, not thickness or volume. As you know, the strength of both steel and CF depend on what kind it is.

I think there is huge potential in the automotive industry to implement CF, but costs must come down and the automation process must improve.

Weight is relatively unimportant for automobiles compared to other vehicles. As I've read elsewhere, the larger the percentage of a vehicle is comprised of fuel, the more important it is to reduce weight. Rockets are about 90% fuel by weight, so exotic lightweight materials are cost effective. Airplanes are about 40% fuel, so they have a medium need for lightweight materials. Cars are only 10% fuel, so they don't benefit as much by expensive forms of weight reduction.
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Old 02-19-2018, 07:19 PM   #18 (permalink)
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Uhhnnn... But they always told us : "Carbon fiber... a lot stronger than steel and a lot lightweight than steel, so now we can build cars much more stronger and much more lighter."

So it's not so stronger and lighter at same time. And based in your information I conclude the pices of CF need to be much more ticker to compare or surpass steel.
It would take countless layers (and $$$$$) to get really 3 times stronger than steel. Unviable for DIY projects of eco vehicles (unless we accept a not resistant final work).

Quote:
Originally Posted by redpoint5 View Post
Strength claims are based on weight, not thickness or volume. As you know, the strength of both steel and CF depend on what kind it is.

I think there is huge potential in the automotive industry to implement CF, but costs must come down and the automation process must improve.
Sorry to disagree with you now. But a rocket it's mostly fuel in weight, so if you cut for the weight of the empty body of a rocket in 99%, it would still be incredible heavy (98,99% of weigh if with fuel added), due the weight of fuel.
A Airplane would take some benefit.
But a car, with only 10% of fuel weight of total weight, and so a90% of weight for the car's body (shape/reels/motor...) and if we could cut 70% of the body weight, the final car (with fuel) would be 40% of the initial car's weight with fuel.
You had reversed the fuel weight important analysis.

Quote:
Originally Posted by redpoint5 View Post
Weight is relatively unimportant for automobiles compared to other vehicles. As I've read elsewhere, the larger the percentage of a vehicle is comprised of fuel, the more important it is to reduce weight. Rockets are about 90% fuel by weight, so exotic lightweight materials are cost effective. Airplanes are about 40% fuel, so they have a medium need for lightweight materials. Cars are only 10% fuel, so they don't benefit as much by expensive forms of weight reduction.
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Old 02-19-2018, 07:30 PM   #19 (permalink)
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Quote:
Originally Posted by All Darc View Post

I still challenge someone to prove me that a home made carbon fiber is stronger than steel. Right now for me, based in these videos, it's just crap.
Ok but I need several parameters defined: weight / mass of finished product, resistance to how much force applied where and how, binder materials and their specs, resins specs for filling the matrix, cure process, Attach points, etc. If it is a simple pull test then the comparison can be done easy peesey. How strong is 10 mill steel 1" wide? (I already know this.


Btw when you say home made, what do you really mean?
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Old 02-19-2018, 08:15 PM   #20 (permalink)
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Quote:
One thing anoys me. The carbon fiber shappingg made in home, like we see in youtube videos, do not use autoclaves, and many carbon fiber sheets looks very crap, not even solid. I presume that withouty a autoclave it's impossible to create really resistant carbon fiber like in formula one cars.
I find this the earliest, clearest statement of your question.

To my understanding (YMMV), the hurdle for mass production isn't cost so much as speed (and possibly yield rate). And the lack of high-speed production is down to the vacuum-bagged autoclaving. It's purpose is to minimize the amount of binder — epoxy or whatever — in ratio to the fibers, to maximize strength (toughness, whatever) for weight.

On to the larger question, the future of carbon fiber. That would be in 3D printing:

https://en.wikipedia.org/wiki/Strati_%28automobile%29

OTOH it's future will include competition:

https://en.wikipedia.org/wiki/Basalt_fiber
Quote:
Basalt fiber is a material made from extremely fine fibers of basalt, which is composed of the minerals plagioclase, pyroxene, and olivine. It is similar to fiberglass, having better physicomechanical properties than fiberglass, but being significantly cheaper than carbon fiber. It is used as a fireproof textile in the aerospace and automotive industries and can also be used as a composite to produce products such as camera tripods.
Read it and weep.

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