Friday, December 4, 2009

Nanotechnology Application In Bicycles : How Good?

Readers may know that last year, I addressed how carbon nanotube technology had been seeping into the bicycling scene. While by themselves, the properties are very remarkable, the issue we all want to sort out is, how much is the end product we care about - the bicycle frame - improved by using such tech?

Some readers in that article held the view that this technology is an "April Fool's joke" on the consumer, that the change in finished properties in the frame with nanotube reinforcement is extremely small and not worth it considering the increases in cost. Is this just a "feel good" marketing ploy from the cycling industry? Should it have prevented failures such as this one?

Today's article below is borrowed from one of the writings of Dexter Johnson, who is an IEEE technical blogger writing for Nanoclast. Here, he's posing the question of what nanotube reinforced bicycle frames really have to offer in terms of cost-benefit and also explores the different buzz words seen in bicycle marketing literature. Do they mean anything at all?

Enjoy the read and let me know what you think.

Nanotechnology And The Bicycle
Dexter Johnson, IEEE
September 9, 2009

At a conference that I had put the program together for a few years back, a speaker during his presentation suggested that maybe he would supply some carbon nanotubes to a bicycle manufacturer and have Lance Armstrong ride the bike in the Tour de France. What a great marketing idea, he thought out loud.

Being an avid cyclist and an even more avid fan of cycling, I explained to him that the professional cycling federation had put a weight limit on bicycles and that maybe there was not much to be gained in pursuing this marketing avenue.

How wrong I was. Since then, which I believe was around 2005, I have become aware of at least three high-end bicycles that employ some kind of nanoparticle in the frame.

The three that I know of are Spanish-based BH Bicycles, Swiss-based BMC and most recently I’ve discovered Italian-based Pinarello has gotten on the nano bandwagon.

What does the nanotech actually do for these bikes other than to raise their asking price slightly north of a new economy car? Well, it’s hard to say except by taking a look at their marketing copy.

Let’s start with the BH G4 bike. Here the marketing copy reads: “BH achieves this magical blend of low-weight, great ride and toughness using Nanotechnology resins.”

“Nanotechnology resins”? After reading the rest it appears what they mean is that they are using carbon nanotubes as a filler material between the carbon fibers. Despite the rather breathless description of how carbon nanotubes “have a strength-to-weight ratio orders of magnitude greater than steel”, they never quite get around to saying whether the CNT-enabled resins make the carbon fiber bicycle any stronger or lighter than any other run-of-the-mill resin.

BMC it turns out is using carbon nanotubes in exactly the same way as BH (not really a surprise to be honest). But BMC does manage to say that the material matrix that is developed using these carbon nanotubes is 20% stronger for practically the same weight. I am a little concerned with the usage of the phrase “practically the same weight”. And for that matter what does “stronger” mean?

Pinarello appears to be much more discrete about their foray into nanomaterials, but they do manage to say the following: “the exclusive 60HM1K carbon by Torayca® with Nanoalloy™ that prevents sudden breakage.”

Wow, now we’ve got a nanoalloy (and it’s trademarked)! From what I have been able to piece together about the “Nanoalloy™” from the bicycle trade press is that:

“Nanoalloy… disperses nanoscale elastomers between the carbon fibers. These elastomers have the ability to absorb impacts and prevent the propagation of cracks as they occur.” The result: Pinarello claims the Dogma frame weighs about 860 grams, 40 grams less than the Prince but is 23 percent more resistant to impacts."

Could this resistance to impacts that Pinarello describes be the same “stronger” that BMC offers up?

Is there anything to all of this nano talk in bicycles other than a cool marketing angle? Impossible to say outside of conducting some real experiments, and it’s hard to imagine anyone being that interested to bother.

Now if we can develop a material that would be perfect for the rigors of a bicycle frame by using a material by design method and then build the material and the frame atom-by-atom then I might pay a premium price for it. Will I still be able to ride a bike by then? Stay tuned.

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Chris said...

Agree with the article. My sincere opinion is that its better to stay away from any new technology that just appeared recently in the industry. Its costly, haven't proven much in terms of benefits, and the end user is making a gamble by a) not being much knowledgable about what they're getting into, b) opening themselves up to the risk of being the first testee. Save the bucks on something that has taken the rounds and proven something in terms of safety and design. Unless you want to be the pioneer and jump into the unknown waters...

Anonymous said...

Just another gimmick by the industry to make a few bucks off dum early adopters.

energetich20 said...

Carbon Nanotubes are all well and good, but I don't think the failure mechanism for bikes is addressed by them. In general, when a carbon frame fails it is not some small crack propagation issue that would have been solved by micro-fibers mixed into the resin. It is rather a catastrophic failure of the resin in compression which leads to complete crumple type failures. Nanotubes do little to address resin/laminate compression strength. I could see fatigue life of a frame increasing from their use, but should we really by using our frames anywhere near their fatigue life?

If crack propagation is the issue, there is something else wrong.

When it comes down to it, carbon has some tensile strength and resin has some compression strength, if you aren't going to improve the compression strength of resins you should focus on structural design like Cervelo seems to do so well.

Any frame manufacturers working in Kevlar for better frame compliance? I'm guessing not because of resin flexibility issues, but I would be curious if anyone has seen it out there?

Anonymous said...

energetich20 -
Doesn't the use of Carbon Nanotubes increase the the impact resistance of the carbon fiber product without adding any real weight penalty?

That seems like a good idea to me.

Also, the use of Carbon Nanotubes does not actually require any realy change in mold tooling, or the lay-up schedule.

In fact, it is pretty easay to implement.

I think these two reasons are the primary ones for their quick acceptance in the bike industry.
- Ryan

Milessio said...


The Arkema website does seem like gobbledegook, but I don't think it was written with us as the target reader. On the pdf information sheet the following contact is given, so maybe Robert can explain it to you in less specialised language?

In US:
Robert Barsotti - +01 (0) 610 878 6028

Jason K said...

Energetich20, I have to disagree with you strongly about the failure mode of carbon/resin systems. You need to think about it from a micromechanics perspective. "Plain" carbon (no resin) has plenty of compression strength; it's not all that much less than the tensile strength.

However, the fiber diameters are so small that the individual fibers tend to buckle immediately. The resin is there largely to stabilize the carbon, keeping it from buckling under compression.

You suggest that the resin fails in compression; that's not right. Look at the stress/strain curves for the epoxy matrix and the dry carbon; remember that the strain of the fiber must equal the strain of the resin at the fiber/resin boundary. Carbon fibers are so much stiffer than the resin that their stress level at a given strain is much, much higher. When the carbon reaches its ultimate compressive yield strength, the resin hasn't been strained nearly enough to reach its yield stress.

Obviously, once the carbon reinforcement goes, the matrix (with much less strength) fails as well. However, the carbon fibers themselves fail first under a pure compressive load.



P.S. I saw from your Blogger profile that you're an engineering student at UW-Madison. I got my master's degree there. Which program are you in?

Jason K said...

Energetic20, I followed the links in your Blogger profile and I see you're on UW-Madison's concrete canoe team, so you're almost certainly a civil engineering student.

That explains a lot. The compressive failure mode you described is right for reinforced concrete but wrong for carbon/epoxy structures. As you well know, reinforced concrete typically uses steel rods (rebar) to handle tensile loads. Under compression, the concrete bears the load.

Why? Because the concrete matrix is stiffer than steel "fiber". The compressive failure strain for the concrete is much smaller than that of the steel, so the concrete fails first and the steel crumples.

But this is not what happens in a carbon/epoxy laminate. The fiber modulus is typically 10-15 times that of the matrix, so the situation is essentially the opposite of that embodied by reinforced concrete.

At any rate, I now understand why you made your claim about the matrix taking the compressive load and failing first--you were treating carbon/epoxy laminates like reinforce concrete. That's a mistake, but the mistake makes a lot more sense and is very understandable now that I know the context.



P.S. For what it's worth, I was in the Engineering Physics department at Madison. If you have any interest in learning more about composites in general, I highly recommend Professor Rowlands' class on composites. It's ME 508, so it's technically a mechanical engineering class. However, I'm sure Prof. Rowlands would give you permission to take the class if you were interested. He's a fantastic teacher and a really nice guy; I took 508 from him and then did a semester-long graduate-level independent study project with him. His voice is kind of funny in a good way; it was like learning about composites from Fozzie Bear.