Carbon Nanotubes VS Kevlar

[RacingManiac]

Funny thing I just read, a replacement CF hood(not even a chassis component) for a new Ford Shelby GT500 will cost $18K....sure there is a ton of mark up, but compare that to any series production parts today.....

About the repair, most race car tubs can only be repaired at specialist manufacturers, and I believe that's how a lot of them makes some extra money. Multimatic in Toronto for example does repair for a lot of the single seaters in various series and their repair work has to be re-certified by the governing bodies for the car to get their chassis plate back. The equipment and material is not something a regular mom and pop shop can afford or used....

Lotus is unlikely to move from their current bonded aluminum extrusion to something like a carbon tub. The amount of weight you are going to save is not going to be remotely proportional to the cost. Sure the new McLaren is going to be cheaper, but you are still talking about a $200,000+ car, vs a $70,000 car....

[Roentgen]

Chasis only, isn't it?

That, and also some other parts, like the one piece carbon monocell.

[wwgkd]

^^ That's why enclaves are used for "production" Vaccuum and heat pulls them out !

Tho A friend made his own c/f panels for his Darrian ... and then told to stop by the company !!!! So where it's not load bearing it's not so crucial.

BUT still too expensive.

Am intrigued if the documentary on the JSF and new son the 787 mentioned that Airbus Industries are doing fine using carbin fibre in their planes COULD NOT RESIST


THE best pic I've seen of the Airbus military transport A400
BUilding on the experience of Airbus on carbon fibre tail planes and partial carbon fibre structures, the wings are carbon fibre -- made in the UK
Delivbery problems and cost/schedule over-runs meant the intended engines were tested in Hercs and the plane isn't meeting it's lift objectives. Short by 3 tons .. ... which is a lot of ammunition
The Filton site reported the wings had been undergoing their test-to-destruction and met every objective !
A400M Deal Near, Airbus Says | AVIATION WEEK << clearly not any one thing by the sounds of it.

The plane boeing came up with for the JSF contract (like any experimental new plane) had some problems, but in reality lockheed martin just made a better, more usefull plane. It wasn't really a problem with the tech or the engineering put into it, they just went further than required (or wanted) and came up with a more expensive design. Still, Boeing commercial has been on a downward slide for a while now due in part to the fact that they dominated for so long they stopped trying to build new things and just tried to keep what they had. The new managment even said that they didn't envision boeing as an engineering company, but as a manufacturing one. Pretty craptacular attitude if you ask me. I know some people involved in the mess and it's not so much the carbon fiber as nepotism placing managers that shouldn't be where they are resulting in bad engineering calls.

Also if you want to brag about airbus lets remember that they just lost the ruling and it has been decided (at least this can be said in part since exact details haven't been/may not ever be released) that they violated international trade rules and recieved an unfair advantage by taking all that money from the governments involved. What you're bragging about is that some of the richest countries in europe combined managed to out spend one US company. Lofty goals...

Hmm. Interesting, didn't know that it could be THAT bad...

A C/F Focus would be too much, but I would love to see an Evora or a GT-R. They would sell like hot-cakes if the price could be made right.

Anyways the debate has concentrated on carbon. Does anyone have an expertise on Carbon nanotubes? How would that turn out?

No experience myself, but I'd immagine that the tech would have the same problems as are ebing discussed with carbonfiber, just magnified greatly. Who knows what will happen in the future? I' imagine that composits will become more commonplace, but it will take a manufacturing advancement rather than advancing the tech for carbon focuses to appear.

[Bob]

One big thing with carbon is that its hard to tell if the work is good or bad- it takes advanced equipment to actually look inside the structure and see if its sound. Unlike steel there are almost no visible signs of the quality of work.

[acfsambo]

First of all Carbon Nanotubes and Carbon Fibers are different things. Carbon Nanotubes have not been made longer than about 20mm (a little less than an inch) if i remember correctly. Carbon fiber has a Tensile strength of approx 5.6 GPa, the Nanotubes have a tensile strength of 62 GPa and Kevlar has a tensile strength of 3.6 GPa.

There is no way as of yet to make long ropes of the Nanotubes. The space elevator, if made, is going to use carbon nanotube cables, though since that we cannot make a continuous length of carbon nanotubes, that wont happen.

[CapnBoost]

I just want to note that "strength" is a relative term. When used to compare kevlar and carbon fiber composites to other substances (usually metals) they're talking about stiffness. It's load/stress bearing capacity is lower, and rather than deform (like a metal) they will fracture and/or de-laminate.

Also differences between dry (autoclaved pre-preg) and wet (practically fiberglass) carbon fiber/kevlar.

[ronbros]

this mimics the Carbon fiber debates of 15-20yrs back.

guys just give it time!! C/F was real expensive back then, its much more relative today.

[Alastor]

I just want to note that "strength" is a relative term. When used to compare kevlar and carbon fiber composites to other substances (usually metals) they're talking about stiffness.

Isn't that backwards...strength is a fixed material property, while stiffness is dependent on an objects size/shape?

[CapnBoost]

Isn't that backwards...strength is a fixed material property, while stiffness is dependent on an objects size/shape?

Actually no. The trouble is that we're discussing many different engineering attributes: Tensile & ductile strength, hardness, malleability, etc. I wish I had a greater grasp on these concepts but I do not. It's difficult to describe since I don't have the literature handy.

[Alastor]

Actually no. The trouble is that we're discussing many different engineering attributes: Tensile & ductile strength, hardness, malleability, etc.

Again, all three of those are 'constant' material properties, they are bulk properties and they don't change if you have more or less material. While stiffness is a function of both material properties and geometry.

For example, if you take a plate and make it twice as thick the stiffness is increased. However, the tensile/ductile strength, hardness, etc are unaffected.

So I don't understand why you would say they are relative measures. If anything stiffness is relative because it is only applicable for the same geometries.

Although I would agree that "strength" is a vague term, as you pointed out there are many kinds. But to be fair "stiffness" is also vague as it can mean different things in different applications.

[CapnBoost]

Certainly stiffness can be improved by geometry and dimensions. As can load bearing ability, etc.

What I'm saying is that carbon fiber is not x times as strong as steel because there are many different kinds of strength.

[Alastor]

What I'm saying is that carbon fiber is not x times as strong as steel because there are many different kinds of strength.

That makes sense, and also obviously you can compare the same type of strength and therefore say that carbon fiber is "x" times stronger/weaker than steel.

Although the caveat with composites material is that they have orthotropic material properties, so the strength is dependent on the direction in which the load is applied with respect to construction orientation. Maybe that is what you were getting at?

[CapnBoost]

That makes sense, and also obviously you can compare the same type of strength and therefore say that carbon fiber is "x" times stronger/weaker than steel.

Although the caveat with composites material is that they have orthotropic material properties, so the strength is dependent on the direction in which the load is applied with respect to construction orientation. Maybe that is what you were getting at?

Yes, to a certain extent. And the fact that instead of deforming like metals they will have the tendency, if the stresses are high enough to catastrophically fail.

The price of composites may come down so far that it's available in a consumer car, but should you ever get in to an accident the insurance co. would write it off faster than you can say "I <3 carbon!", in part owing to the fact that no body shop is going to have an autoclave to fix your car.

In a mass produced automotive application the materials' behavior at the threshold of failure is very important.

[keerthana]

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[lightweight]

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How insightful of you