tag:blogger.com,1999:blog-4786784182488135171.post859011785902565571..comments2023-07-21T17:26:24.127+04:00Comments on Ron George: Nanotechnology Application In Bicycles : How Good?Ronhttp://www.blogger.com/profile/16268869622833968439noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-4786784182488135171.post-11636730472340216212009-12-09T05:39:28.567+04:002009-12-09T05:39:28.567+04:00Energetic20, I followed the links in your Blogger ...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.<br><br>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.<br><br>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.<br><br>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.<br><br>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.<br><br>Cheers,<br><br>Jason<br><br>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.Jason Knoreply@blogger.comtag:blogger.com,1999:blog-4786784182488135171.post-2463848268430889332009-12-09T05:08:53.862+04:002009-12-09T05:08:53.862+04:00Energetich20, I have to disagree with you strongly...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.<br><br>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. <br><br>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.<br><br>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.<br><br>Cheers,<br><br>Jason<br><br>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 Knoreply@blogger.comtag:blogger.com,1999:blog-4786784182488135171.post-53642018816391708902009-12-07T16:15:37.812+04:002009-12-07T16:15:37.812+04:00Ron,The Arkema website does seem like gobbledegook...Ron,<br><br>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?<br><br>In US: <br>Robert Barsotti - +01 (0) 610 878 6028 <br>robert.barsotti@arkema.comMilessionoreply@blogger.comtag:blogger.com,1999:blog-4786784182488135171.post-54828965474308772382009-12-07T04:23:58.046+04:002009-12-07T04:23:58.046+04:00energetich20 - Doesn't the use of Carbon Nanot...energetich20 - <br>Doesn't the use of Carbon Nanotubes increase the the impact resistance of the carbon fiber product without adding any real weight penalty? <br><br>That seems like a good idea to me. <br><br>Also, the use of Carbon Nanotubes does not actually require any realy change in mold tooling, or the lay-up schedule. <br><br>In fact, it is pretty easay to implement. <br><br>I think these two reasons are the primary ones for their quick acceptance in the bike industry. <br> - RyanAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-4786784182488135171.post-65991594084336730522009-12-07T04:09:45.955+04:002009-12-07T04:09:45.955+04:00Carbon Nanotubes are all well and good, but I don&...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? <br><br>If crack propagation is the issue, there is something else wrong. <br><br>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. <br><br>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?energetich20https://www.blogger.com/profile/15519955301173973173noreply@blogger.comtag:blogger.com,1999:blog-4786784182488135171.post-45031799282315800962009-12-06T03:18:11.009+04:002009-12-06T03:18:11.009+04:00Just another gimmick by the industry to make a few...Just another gimmick by the industry to make a few bucks off dum early adopters.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4786784182488135171.post-80671693856081043752009-12-05T05:29:23.284+04:002009-12-05T05:29:23.284+04:00Agree with the article. My sincere opinion is that...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...Chrisnoreply@blogger.com