Who among cycling and cycling aficionados has not heard of carbon fiber? It is ubiquitous in cycling news and it spills a lot of ink, whether on amateur blogs or specialized sites. In short, carbon fiber is an essential subject and we wanted to review its real advantages.
Carbon fiber competes with aluminum and steel in the manufacture of bicycle frames (at least it plays the role of the high-end underdog). Many are content to see it as an innovative material, expensive and endowed with special and somewhat enigmatic properties … without however trying to understand its real added value.
Let’s take a closer look at what carbon fiber does compare to aluminum and steel. This will tell you if it really meets your needs.
Carbon fiber: characteristics and manufacturing method
Carbon fiber is an inorganic compound material from the family of polymers, light, and insulating macromolecules (they play the role of electrical and thermal insulators). Like plastic, carbon fiber is obtained after a long manufacturing process: poly-acrylonitrile (PAN) is mixed with compounds such as methyl acrylate.
To form the filaments that characterize carbon fiber, the PAN must be stretched so that it is parallel to the fiber. PAN is then oxidized by adding oxygen, resulting in a hexagonal structure. It is following this step that the fiber takes on its characteristic black color.
The carbon filaments measure between 5 and 12 micrometers. To get an idea, know that such a filament is thinner than human hair. These filaments are then combined with thermosetting polymers such as an epoxy resin (from the poly-epoxy family), polyester, or vinyl ester (VE).
Due to the amorphous structure of carbon fiber, its configuration is irregular, and its sheets are distinguished by their strength. The combination by layering with the resin allows obtaining distinct mechanical properties while forming a strong, coherent, dimensionally stable, X-shaped anticorrosive, which withstands compression.
The end product is a kind of black fabric with distinctive very light and very malleable design, which completely revolutionized the manufacturing of parts in various industries. The bike has not escaped this radical innovation: frames and accessories are now available in carbon fiber.
Cost of manufacturing carbon fiber
Carbon fiber is expensive because its manufacture is complex and almost “artisanal”. It is used to build professional racing bikes and high-end products. A consequent drop in prices will be possible in the medium and long term when industries have reduced their manufacturing costs. Carbon fiber will then be within everyone’s reach. Aluminum remains one of the most economical and popular options.
Carbon fiber: lighter and more resistant
Carbon fiber is less dense than steel or aluminum, more resistant to mechanical pressure and corrosion. More insulating, it resists fire better and slows down electrical conduction.
Now ubiquitous, its history dates back to the 19th century, when inventor Thomas Edison and his teams began to explore the properties of carbon filaments. Edison used a method of carbonization to form cellulose filaments: these filaments were used to make the carbon filaments found in fluorescent lamps.
It was not until the 1960s that Union Carbide industrialized these carbon filaments. In 1966, manufacturers obtained PAN fibers formed from carbon, petroleum, and resin. Current carbon fiber is the result of the combined efforts of American, Japanese, and British manufacturers.
Very early on, the aerospace industry took a keen interest in carbon fiber, but it was the automotive industry that benefited the most: Formula 1 cars with monocoque chassis, dashboards, roofs of city cars, bodywork, universal joints, axles, crankshafts… to name just a few notable applications.
The stiffness and strength of carbon fiber bikes
The thermosetting resins in carbon fiber make it more rigid than steel or aluminum. Carbon fiber is 8 to 10 times stronger than aluminum or steel. Top athletes and extreme mountain bikers know all about this (although the bulk of the market is monopolized by aluminum and steel).
The tensile strength of steel is 600 MPa compared to 3600 MPa for carbon fiber. This resistance continues to increase as innovative nanotechnologies are incorporated into carbon fiber. No wonder the bicycle industry has literally rushed for carbon fiber.
To give it the desired shape, molds are used in which the resin is poured. This resin is then dried to obtain the desired frame. This technique is reminiscent of the manufacturing method of fiberglass.
Layers of carbon fiber are assembled in all directions to absorb any impact, regardless of the impact area. This “woven fabric” aspect is clearly seen on most bicycle frames, especially from the most reputable manufacturers; it is a kind of signature (unfortunately this signature is forged). This artisanal work also justifies the final price of the product: it takes great know-how and finesses to develop a carbon fiber frame that is as aesthetic as it is robust.
The weight of carbon fiber
The lightness of carbon fiber is second to none – it is one of the two great characteristics of this fiber and one of the main reasons the bicycle industry has adopted it.
Thanks to carbon fiber, airplanes are lighter, as are boats and vehicles, without being less robust.
Carbon fiber is 4 to 5 times less dense than steel: the resulting lightness is obvious. A one-meter beam weighs at least 12 kg if it is made of steel, compared to a maximum of 2 kg if it is made of carbon fibers.
As a result, the carbon fiber electric bike has unparalleled elasticity, lightness, design, and aerodynamics. In Formula 1, acceleration, cornering speed and collisions would be unthinkable without the carbon fiber.
Design and aesthetics
What jumps out at the sight of a carbon fiber frame is the look! The eye perceives immediately that it is dealing with a noble material, elegant and incomparable to steel or aluminum (as noble as they are!). Carbon fiber is more malleable which has given the bicycle industry a boost of creativity.
The fiber can be affixed in plates, in raw or short form, in order to create the different parts of the bike: frames, pedals, handlebars … Throughout the manufacturing process, we see that the automation is less and that the craftsman lingers on each piece. The use of fiber is in a way more “artisanal”, less industrial. Only the cutting of the initial plate – the one from which all the parts are created – is managed by the computer.
The demolding, painting, and cleaning of carbon fiber also follow strict rules. Here again, great dexterity and perfect knowledge of the material are required. Defects happen quickly, for a careless mistake or a hasty gesture. We are really talking about the work of a goldsmith.
Carbon fiber can be repaired if there is damage to its structure. But this repair requires expert intervention and “tinkering” is not advisable (even if you find a great tutorial on YouTube!). It is then necessary to cut out the damaged part, put a new hardened and sanded part.
Fiber is a composite material, both rigid and elastic, designed to resist impact. Certainly. But doubt remains: does carbon fiber absorb impact so well and are its properties so flawless?
In its early days, carbon fiber was mixed with aluminum compounds … and it was susceptible to galvanic corrosion and UV exposure; rather embarrassing for a product that everyone said the greatest good about!
But with the help of materials engineering, these early mistakes were quickly resolved. Carbon fiber bicycle frames can now last for years without damage. So much so that if you take good care of it (and in general, the rider takes care of it given the price of the product), your carbon fiber bike will be with you for life. Incremental innovations have also strengthened the resin that forms carbon fiber.
The FDC In a bicycle
Carbon fiber frames are found in all major bike families: urban, racing bikes, mountain e-bikes, cyclocross, cross-country … especially in bikes subjected to extreme conditions (cold, heat, wind, rain, snow ). The performance of carbon fiber makes it a top-of-the-range product even if it becomes more democratized every day.
Despite all of its strengths, carbon fiber still has a long way to go: aluminum and steel remain prime options for most of us. You will find excellent value for money in the segment of aluminum and/or steel bikes.
Caution: The braided fiber pattern can be imitated. So beware of counterfeits if you opt for carbon fiber. Pay special attention to the weight: counterfeits are always heavier than genuine carbon fiber.
Carbon fiber has a bright future ahead of it: technical progress, innovations, and combinations (especially with Kevlar PPD-T) will give carbon fiber properties unprecedented in the history of building materials.
3 areas for improvement
- Make carbon fiber 100% recyclable.
- Automate your production
- Lower all production costs to democratize carbon fiber
- Will the future of cycling by 100% carbon fiber?
Certainly not! Steel and aluminum have proven their worth in all segments of the market: from racing bikes to hybrid bikes, mountain bikes, and electric folding bikes. Before buying a carbon fiber bike, identify your needs: Will you be using it for sport in a competition? Do you have the necessary budget? Do you really need an ultralight model? Are you looking for a tailor-made or unique design? These are the kinds of questions that will guide your choice.
We hope we have helped you better understand the benefits of carbon fiber. If you already have a carbon fiber bike, please let us know about your experience in the comments!