Carbon Fiber vs Fiberglass

[CFMopar]

I was just wondering the other day. Whats some of the pros and cons of both?

[mikepmcs]

http://en.wikipedia.org/wiki/Carbon_fiber

http://en.wikipedia.org/wiki/Fiberglass

Don't know if it will help but it's got some good info.

[Mr.Woolery]

It depends on what you're looking to build.  Carbon fiber can be a superior material for your needs, but you have to know how to process it to get any benefits it offers over fiberglass.  If you're looking to make your own parts and don't have an autoclave or vacuum bagging equipment (ie, you're going to make wet lay stuff) you're probably better off using fiberglass...it's much cheaper and it's easy to work with.

I've got a little experience working with both at the DIY level.  I made most of the body on this car out of various carbon/fiberglass bits, depending on their function & ease of fabrication.  Took me several years...learned by doing it:

[bull]

Carbon fiber is strong, light and expensive. Fiberglass is strong, heavy and cheap.

[bigcountry]

Carbon fiber is strong, light and expensive. Fiberglass is strong, heavy and cheap.

  You have to know what you are doing with carbon fiber, it is a more technical process.

[CFMopar]

Just thinking of buying some light weight parts for my daily.... I heard carbon fiber is more brittle and costly to repair and does not take to rocks and other road hazzerds very well.

What is the weight difference between carbon fiber and fiberglass...

[bull]

Just thinking of buying some light weight parts for my daily.... I heard carbon fiber is more brittle and costly to repair and does not take to rocks and other road hazzerds very well.

What is the weight difference between carbon fiber and fiberglass...

Just a guess but I'd say comparing equally-sized piece of materials of equal strength, fiberglass would be 4-5 times heavier.

[CFMopar]

Just thinking of buying some light weight parts for my daily.... I heard carbon fiber is more brittle and costly to repair and does not take to rocks and other road hazzerds very well.

What is the weight difference between carbon fiber and fiberglass...

Just a guess but I'd say comparing equally-sized piece of materials of equal strength, fiberglass would be 4-5 times heavier.

Thanks. Any truth to the britlleness?

[Ghoste]

Yes, it's very brittle and it's also good conductor of electricity.  That could be a pro or a con depending on how you plan to use it.

[Mike DC]

   
CF is brittle as hell. 

It's strong as hell too, but there is absolutely no flexing.  Either it's 100% intact or it is shattered.



It tends to break in a nicely controlled manner though.  Nice & even "falling away" quality to the chunks.  Almost like the way the dust falls away when you're sanding a very high-quality bondo. 

[Chad L. Magee]

Fiberglass has a tendency to shrink over time as the adhesives that hold it together start to decompose, especially if not well cared for (ie. stored outside unprotected from sunlight).  Left exposed too long without paint, the actual fiberglass strands can start flaking off from the surface (which is starting to happen to the hood and front fenders on my 70 Stingray), which is not fun to work with.  I hate the itching feeling after working on it, and not just because it is a chevy!  As for carbon fiber, I don't know if it has the same type of problem, but I would suspect not based on what I have read.


Warning:  If you don't like science, the rest of the post will be useless to read any further....

As a chemist, I do know that a new generation of carbon material technology is in the works, based upon sheets of carbon rather than individual strands (basically carbon nanotubes) "glued" together.  I have read that GM is in the developing stages, but the financial situation might end up cutting of the research funds to it.  They are after it for the corvette bodies first, but it is also useful for economy cars that they might be forced to make.  These new carbon materials would look much like the structure of graphite, except for materials that interact to lock the carbon layers together.  Graphite is slippery because of the low amount of force it takes to overcome the VDW force that locks them in place.  (The slip you feel is the layers gliding across each other.)  The new material would not allow for slippage between layers and should give a more ridged product.  The electrical conductivity of the material would be displaced a bit as the conjugated bonds in the carbon layers would be disrupted somewhat (depending upon the materials used to bind the layers together).  That can be fixed by adding in the correct dopant.  The binding material could even be picked to give the new carbon product different properties (ie. built into the structure) that regular carbon fiber would not have.  As you can tell, I have many potential ideas on this application (hint - think about a basically non-metallic automobile and how that would change things a bit towards future transportation)......

[Chad L. Magee]

Just thinking of buying some light weight parts for my daily.... I heard carbon fiber is more brittle and costly to repair and does not take to rocks and other road hazzerds very well.

What is the weight difference between carbon fiber and fiberglass...

Just a guess but I'd say comparing equally-sized piece of materials of equal strength, fiberglass would be 4-5 times heavier.

I agree with bull on this one.  Fiberglass corvette bodies are not as light as most people think that they are.  It usually takes five to six people to lift the fiberglass shell off of the frame according to a Corvette restoration book that I have been reading.  The same shell out of carbon fiber could be lifted easily with two people in the right spots, one if they can manage it (bulky to handle).  That information is base upon a racing show I saw on speedtv a while back....

[Brock Samson]

interesting stuff,.. 
  Getting off track a bit -
Some of the materials experts such as yourself Chad, might be able to shed some light on the advancements I was reading about several years ago, i've heard nothing of since,.. regarding electric/fiber optics/controls even blended materials allowing control surfaces to flex at leading and trailing edges,.. of course this was skunk works type apps for future military air planes.
any thoughts on this, examples or R&D or where I might find research materials on the web or in publications?..

 

[ds440]

Brock,

Several years ago in Formula 1 a couple of internet hacks accused Ferrari of using that exact type of device.  Piezoelectrics?  They believed that Ferrari were using electrical current to bend the rear wings, to allow the wing to "lay down" (only slightly mind you) for improved arrow flow in the straights.  In the corners, the system turns off, wings go back to maximum downforce and away you go...

Mind you there was ZERO evidence of such a device, plus the cost has to be astronomical.  But it was on the internet so it HAS to be true.

However, carbon fiber will flex....VERY slightly - just watch some of the onboard shots during a race and you will see *some* (and very slight) wiggle.  The FIA will test the wings flexibility by attaching weights to the wings and there is an allowed tolerance.

http://www.youtube.com/watch?v=YQzFTeRomfg

http://www.youtube.com/watch?v=iJtNrM58PyY

However if you push carbon fiber too far you'll get THIS:

http://www.youtube.com/watch?v=kKMp5LBiafY

[Mike DC]

   
In the big picture, I think CF's extreme stiffness may become viewed as the biggest problem with it.

Extreme stiffness has its place, but in real-world daily life there aren't many times when you want something THAT brittle.  In most cases it just means stuff breaks more.  (Witness the flood of improvements we've gotten from plastics/urethanes, largely for opposite reasons.) 

[Chad L. Magee]

interesting stuff,.. 
  Getting off track a bit -
Some of the materials experts such as yourself Chad, might be able to shed some light on the advancements I was reading about several years ago, i've heard nothing of since,.. regarding electric/fiber optics/controls even blended materials allowing control surfaces to flex at leading and trailing edges,.. of course this was skunk works type apps for future military air planes.
any thoughts on this, examples or R&D or where I might find research materials on the web or in publications?..

 

Sorry if this is way off topic.....

Yes and no.  There are scientific publications out there on what you are looking for, but they are usually written in a way that basically an expert is needed to interpret into a usable form.  If you do decide to go this route, a good starting point to look at is either Inorganic Chemistry or Organometallics, as either one covers material design engineering in their articles.  (Even some of them get me to    for a while before I can see what they are talking about.  It gets even worse if the article is in another language and the translation does not match up to their meanings.)  Patents are just as bad if not worse in that respect.  Both types do not list all of the potential applications for said devices, as that would be like giving away all of your research results before the product is done, leaving you vulnerable to a takeover by someone else.  The internet is a minefield when it comes to certain information, as not everything on it is even close to being true, which can throw you off on your research ideas.  Tread lightly there unless you know the source well enough to trust it.  One thing I can suggest to you is to check with a local college if they have any classes on nanomaterial design or technology materials.  If they do, find out what textbook that they use as it may be a good source for what you are looking for (or at least lead you into the right direction).  I had one of those books, but it is a bit dated now (I took the class back in 2003)......

The sad part of this is that you have to be careful who you talk to if you have a really good idea.  Science is a field of one-up-manship, where you get judged not only on what you have done, but also on what you are currently doing and could potentially do in the future.  That leads to people trying to scoop ideas as they might be stuck in a rut on their own research.  I have never really had that problem as I am constantly designing or inventing new materials in my head (sometimes I do that in my sleep too) and then trying to find the applications for them later on.  Yes, I know that sounds counterproductive/counterintuative in a way, but that is just how my brain is set up to solve certain problems that I see....

Oh....  I just thought of something that may point you in the direction that you originally was asking.  Some of the newer conjugated plastics can be made to induce metallic-like properties (ie. electrical conductivity as an example), depending upon what their starting materials are.  They can be used much like flexible wires on a edge or curved surface that they are coated on.  The key is the delocalized electrons within the material which mimics the free (delocalized) electrons in a bulk metal surface, allowing for electrons to "flow" as in a wire when current is applied.   When I was working on my oral exam qualifier project five years ago, I had an idea similar to that, but I incorporated in an energy collector/storage molecule for electrons, such that the material could be potentially used as a solid state solar cell/battery (all in one device).  Since then, there have been a few articles on similar types of materials (MIT had one I remember seeing), but no working devices with just one material as of yet..... 

[Chad L. Magee]

   
In the big picture, I think CF's extreme stiffness may become viewed as the biggest problem with it.

Extreme stiffness has its place, but in real-world daily life there aren't many times when you want something THAT brittle.  In most cases it just means stuff breaks more.  (Witness the flood of improvements we've gotten from plastics/urethanes, largely for opposite reasons.) 

True, but if the material was fine-tuned a bit, I think that problem can be fixed.  CF materials can be engineered to act differently, it just takes time/patience/money to get it done.  It would be a nice problem to work on.....

[Mike DC]

 
I would be impressed if they could really get around the problems.  I'm not convinced it's fully possible. 


CF displays the same characteristics of most lightweight-but-strong materials - stiff and brittle as hell is the big one.  It's a product of the arrangement of the molecules for the weight loss and I'm not sure they could realistically get the one gain w/o the other loss.

It's like the difference between a 1" OD solid steel bar, versus a 1" OD hollow tube - the tube has most of the bar's stiffness without most of the weight.  But those same characteristics that give that weight loss will also result in a more brittle structure just by definition.  The solid bar's ability to severely flex with a long fatigue life is a product of having lots of extra redundant material in the structure.  But the weight loss of the hollow tube was a direct product of removing that same redundant material. 

[Chad L. Magee]

 
I would be impressed if they could really get around the problems.  I'm not convinced it's fully possible. 


CF displays the same characteristics of most lightweight-but-strong materials - stiff and brittle as hell is the big one.  It's a product of the arrangement of the molecules for the weight loss and I'm not sure they could realistically get the one gain w/o the other loss.

It's like the difference between a 1" OD solid steel bar, versus a 1" OD hollow tube - the tube has most of the bar's stiffness without most of the weight.  But those same characteristics that give that weight loss will also result in a more brittle structure just by definition.  The solid bar's ability to severely flex with a long fatigue life is a product of having lots of extra redundant material in the structure.  But the weight loss of the hollow tube was a direct product of removing that same redundant material. 

I think that they can, although it may no longer be an actual Carbon Fiber structure (strands woven together in place) and may take a long time to do.  It may be more like the strands threaded through carbon sheets to hold them into place (much like the materials I mentioned before), with other flexible materials built in to help cushion the structure.  It could also involve fullerene (carbon soccer balls) cage materials within the design, as they can potentially be used as molecular ball bearings within the actual structure, giving it a bit more of give before the material breaks down.   Whether or not it can actually be done is to be seen though, so you are probably right to be skeptical about it.  I try to think that a solution to every material problem potentially exists, unfortunately we just might not live long enough to find out what it actually is.....