This post is dedicated to the women of the Rêve tour. Six fierce females are riding this year's Tour de France, an event normally reserved for men. The super six is raising money for Bikes Belong, an organization that advocates for bicycle rights. Well said by Josh Herst, CEO of Walk Score, “Bicycling saves money on gas and fosters better health and a cleaner environment. But the best part about it is not being trapped in traffic. Biking can turn your commute into the best part of your day.” Studies have shown that women cycling are a good indication that a city's infrastructure is such that the safety concerns of the cyclists have been adequately considered. As bike-friendly cities go, Portland is # 2 (see bicycle rights video above), San Fran is # 3, Madison is # 5, NYC is # 9 and Chicago is #10. Los Angeles and Glendale do not appear on this top 10 list, no surprise.
When I first got my road bike, my dad was concerned about the structural integrity and long-term stability of carbon-fiber components. Meeting a few new cycling friends (Bodacious Bike Babes or BBB) at Golden Road brewery a couple weeks ago, I realized that my purchase was appropriate at the time (planning a cross-country trip and riding with a club almost daily) but this investment in carbon-fiber may not stand the test of time (everyone in BBB rode vintage steel-frame bikes). This prompted me to investigate the science behind the carbon-fiber components on modern racing bikes.
The size of a carbon fiber filament is 5 to 10 microns in diameter. A human hair ranges from 40 microns to 120 microns in diameter (an order of magnitude larger). On an atomic level the carbon atoms in the fiber are bonded in a honeycomb shape (sp2 hybridized). On a molecular level, long chains are formed via polymerization along an axis. These chains prefer to stack on top of one another. A two-stage heating process involves carbonization (400-1500 deg C) and graphitization (700-3000 deg C), which improves the ordering and orientation of atoms along a fiber's axis. These fibers can be spun into bundles (like yarn) and woven, knitted or braided into sheets. Thus, we have traveled from the nano- (atomic) scale to the macro (human) scale, thanks to Prof. Larry C. Wadsworth and his students at the University of Tenessee, Knoxville who teaches a class called materials science & engineering 554, providing open source web-based access to his course information.
Carbon fiber is used in an array of bicycle components such as forks (Sisneros, et al., 2012), stem (Ghiasi, et al., 2010), brakes and frame (Mattheij, et al., 1998). An associate of Lance Armstrong, Scott Daubert, explains that carbon fiber "has the properties we’re looking for as far as being stiff and light. With carbon fiber you can manipulate the carbon in certain ways to make the bike have a certain feel to it, as compared to metal.” (Byko, 2005) Jim Colgrove is a manufacturing engineer at Trek Bicycles who explains that carbon fiber has evolved since its initial development in the late 1950s and early 1960s. Weight and strength of the material tend to be in opposition, which was the same for other bicycle materials (aluminum, titanium, and steel) but with carbon fiber another dimension can be exploited: "ride feel."
Carbon fiber bicycles are not made of entirely carbon, the woven sheets of carbon fiber are coated with a resin (or glue) to achieve a composite material with specific strength and stiffness. The direction and number of layers can be varied to achieve greater strength or stiffness in various directions based on the stresses to be experienced by the design (Sisneros, et al., 2012). Carbon fiber is not only used in bicycle components, but in other applications where strength and weight are important design considerations. Examples include: airplanes, boats, telescopes, loudspeakers, robot arms, automobile hoods, prostheses, implants, tendon/ligament repair, and radiological equipment. Yes, even my smart car is made of a composite material (but not likely carbon fiber).I have posted this under NANOTECHNOLOGY because this is yet another area where our FITNESS AWARENESS has intersected with our interests in the scientific investigation of material properties.
Works Cited
Byko, M. "Carbon Fiber Lightens up Bicycle Racing" Journal of Materials, February 2005, p. 80.
Ghiasi, H.; Lessard, L.; Pasini, D. and Thouin, M. "Optimum Structural and Manufacturing Design of a Braided Hollow Composite Part" Applied Composite Materials, 2010, Vol. 17, p. 159-173.
Mattheij, P.; Gliesche, K. and Feltin, D. "Tailored Fiber Placement - Mechanical Properties and Applications" Journal of Reinforced Plastics and Composites, 1998, Vol. 17, No. 9, p. 774-786.
Sisneros, P. M.; Yang, P. and El-Hajjar, R. F. "Fatigue and Impact Behaviour of Carbon Fibre Composite Bicycle Forks" Fatigue & Fracture of Engineering Materials & Structures, 2012, Vol. 35, p. 672-682.