Carbon Fiber Technology Overview
Carbon Fiber technology
When it comes to constructing bicycles, carbon fibre is the ideal material that most brands would choose. There are many reasons why carbon fibre is preferred.
Firstly, it is arguably lighter than aluminum and feels much more robust compared to steel. Secondly, it is more likely for engineers to design the shapes and forms based on their creativity and imagination.
There are various types of carbon fibre, and that the engineers need to know which type is appropriate for which bicycle. It’s common for bicycle frames to be constituted of different kinds of carbon fibre throughout so as to balance everything.
Things You Should Know About Carbon Fibre
Carbon fibre has become one of the most commonly used materials in means of transport construction such as airplanes, high-performance cars, motorcycles, and so on.
Moreover, this strong material took the cycling world by storm 10 years ago. For that reason, it’s no surprise to learn that more and more bike manufacturers are making use of carbon fibre, a light yet stiff material in their latest line-ups.
An advantage of using carbon fibre is that it allows greater flexibility, creativity, and uniqueness in their designs which would otherwise have been difficult for metal. However, more research needs to be carried out in order to optimize the characteristics of this relatively new material.
- Carbon fibre is actually a composite
In fact, the carbon material used on bikes constitutes not only carbon, but also a glue-like material called epoxy resin. With the addition of such material, bicycles have become incredibly tough and durable.
- Not all carbon fibres are made in Asia
The primary producers of carbon fibre bicycle frames are China and Taiwan, and they also manufacture carbon-based products. However, such frames and other parts are also constructed by Zipp (US-based brand) or Time (France-based brand).
Most brands have their own fancy carbon construction titles, namely FACT (Specialized), OCLV (Trek) and Advanced Composite (Giant).
One thing in mind is that the ride quality and strength all depends on the manipulation of a particular bike brand.
- Most raw carbon fibre comes from Asia
Nonetheless, only 6 companies actually produce raw carbon fibre, which will be used in the aerospace industry later. These companies are Toho Tenax, Mitsubishi Rayon, Toray, Hexcel, Zoltek, and Cytec respectively.
This new material is derived from Polyacrylonitrile (aka PAN) fibre, which, when baked at very high temperatures, breaks down the non-carbon elements in the fibre itself. As a result, the fibre becomes extremely thin and long.
- Different types of carbon fibre
There is a variety of carbon fibre, including raw thread, sheet or chopped forms. Most of the bikes are built with sheet or chopped fibres, which are found in frames and pedal bodies correspondingly.
- Strength of carbon fibre
The real strength of carbon fibre lies in its layup, and its characteristics – stiffness and lightness. The stiffness can not be changed, yet the anisotropy makes it a very flexible material since it can be stiff if laid out along the axis of the fibre, or unidirectionally.
- Carbon fibre frames are handmade and repairable
Parts of the bikes that are constructed manually include frames, handlebars, wheels, and some other small sections.
The damaged section can be easily repaired with new material with meticulousness, and that it needs to be properly cut, cure, sand and paint.
To construct a perfect carbon fibre bike, it is imperative that a variety of materials be used to produce a stiff yet comfortable, light in and out of the saddle, and robust enough to tackle the rigors of daily riding.
The Ultra Hybrid Carbon (UHC) allows engineers to put the materials together just like the way a cook blends ingredients. Starting with ultra-high modulus carbon fibre, which provides the bike strength and stiffness.
After that, the high modulus and intermediate modulus are combined to create vibration damping for added comfort and impact drag (resistance) to increased durability. The way the materials are laid out brings about thicker areas at the joints, which perform pretty much the same as how butting functions on metal tubing.
UHC enables engineers to place the material where it is needed the most; however, choosing which one appropriate for the application is a whole different story, but it’s apparently something metal tubes cannot be used with.
There are two principal criteria which decides the quality of carbon fibre: elasticity and tensile strength.
The modulus elasticity shapes the stiffness of the carbon fibre whereas the tensile strength decides how strong the fibre is. Due to the materials’ anisotropy, carbon fibre is strong in one direction only, which is along its length and under tension.
That being said, in order to produce a strong tube, the fibres must be positioned multi directionally to put strength into the mix.
The high modulus used has a relatively high tensile strength, which is approximately 8 times greater than 3/2.5 titanium and roughly more than 3 times as rigid as 6061 aluminum.
On top of that, the ultra-high modulus material is nearly 30% more robust than the high-modulus material that is being used, but requires less resins, which makes it not only stiffer, but also lighter.
Molded monocoque designs originated around 20 years ago, a time when engineers learnt something important in order to optimize the construction.
However, molding the whole bike without damage is a bad idea, not to mention that there will be some consequences that may come along. Furthermore, the larger and complicated the structure gets, the harder it becomes for engineers to achieve proper compaction and alignment.
For that reason, they have decided that the superior method to construct a perfect carbon fibre bike is to join smaller sub-assemblies.
Adding more stiffness?
In producing a truly stiff bicycle, each facet of the bike must be optimized, such as the dropouts. The dropout here is forged from one piece, but comes in a number of sizes to prevent failure.
It’s common to see many bikes whose rear dropout is bolted by two pieces together; however, this method makes those pieces shift slightly that create a small bending at the rear wheel.
Let’s talk about the F series, Z series as well as DA bikes. In general, the reason these bicycles are stiff lies in the bottom bracket. A rib of carbon fibre frame extends from the chainstays and wraps around the bottom bracket shell.
The addition of these layers, as a consequence, greatly reinforces the chainstays as well as the seat tube, further stiffening the bottom bracket.
With each frame size, FELT BICYCLES has also specified the diameter, the number of layers of material and corresponding size, and most importantly, the kind of carbon used at different locations.
Such variations exert a huge impact on the quality and strength of the bicycle, allowing riders to find their balance between stiffness, weight, and of course, ride quality.
FELT BICYCLES has successfully created a bike that can take the rigors of long rides while remaining stiff even under hardest sprints, and surprisingly weighs less than a kilogram.
The size-specific ride
When steel was in its heyday, most bicycle frames, regardless of the size, were built with the same tubing, measuring between 50cm to 57cm. The bike maker also made every effort to provide more stiffness to the frame, and that he or she even used a 50cm frame for a 60cm frame.
Now, FELT makes use of small diameter tubes for the smallest frames and vice versa. The company’s goal is to lengthen the tube as much as possible on the small frames because it gives better damping vibration.
FELT BICYCLES claims that they want to maximize this property in small sizes to provide as much comfort as possible. For the largest frames, on the other hand, the transitions, or fillets, between the tubes are enlarged to maintain and increase the stiffness.
Attention to detail
Looking at the front derailleur hanger, it is made from stainless steel, which helps increase front shifting performance. In other words, it improves the ability to ascend to the big chainring while out of the saddle.
The derailleur hanger and seat tube, in turn, receive more reinforcement to become as stiff as possible.
In addition, the bottom bracket shell and head tube feature aluminum inserts for precision instruments. Most of the headsets and bottom brackets employ cartridge-style bearings, which is more convenient when it comes to installation.
In short, FELT BICYCLES is confident to provide you a bike that brings you to perfect ride, whether in race criterium, road races, ride charity events or even in triathlon competitions.
Carbon Fibre Manufacturing Methodology
Factors to consider in manufacturing
There are many factors affecting the construction and quality of a frame or fork. Of all, three following factors are the most important: design details, construction methods, and materials.
Carbon fibre is, in fact, an engineers’ fantasy fulfilled. A high flexible material that not not only can be molded into various complex shapes and sizes, but it is also able to lay up with more materials when needed.
Not to mention the fact that carbon fibre is lighter than aluminum and stronger than steel.
Taking the advantages of this material enables FELT engineers to bring their wall specifications and tube shapes to the next level, including the oversized diameters, unique shapes, and exaggerated tapers.
Each frame makes use of size-specific details, which means those details only pertain to that particular frame size. To illustrate, a 50cm tube diameter has the following details specific to its size, such as the radii and the tube transitions.
With this utilization, bike makers are able to create a frame that is both stiff and responsive, with outstanding damping vibration and vibration control, and most importantly, that frame is specific to the size of the rider.
If you notice, all of the FELT carbon frames are constructed using the Modular Monocoque Method, which is the second primary factor influencing the performance.
In simple explanation, this process entails the construction and molding of individual sections, including the front triangle, seat stays, and chainstays, which allows the bike builders to fully optimize each frame section according to a specific requirement.
As mentioned earlier, the carbon fibre is laid out of multiple layers for each frame section, and the number of layers also determines the weight of the frame. In other words, the number of layers varies depending on the areas where it is placed.
More layers are implemented in areas where the stress on the frame is high and vice versa, areas with low load use fewer layers to reduce the overall weight of the frame.
Once these individual sections are molded, they are put together to form a seamless monocoque, or one-piece, structure.
Knowing the advantages of carbon fibre, which works best under tension, FELT engineers have placed the carbon parts in whichever direction that produces the most stress.
Unidirectional carbon, undoubtedly, has the highest tensile strength, and therefore, is accounted for the structure of the frame to hold everything in place.
With the Modular Monocoque construction method, bike makers are able to create bikes with minimal weight, excellent responsiveness and overall strength without using excess material, puttying or fillering in the finishing process, and stress concentration.
This method, in short, is superior to other construction procedures as the unified design helps ensure perfect alignment.
As we may know, all carbon fibre material is not created equal. For example, the carbon weave is normally used for the final outermost layer since it can be seen through the clear coat.
The properties of a single material gives little or no information about the quality of a frame, instead, the modulus and the tensile strength are two primary factors that determines the quality of the frame.
However, creating frames with highest modulus or greatest tensile strength means no perfection and/ or success. In doing so, there would exist problems and compromises relating to stiffness, and ultimately, the ride quality.
For that reason, placing different materials with unique properties at specific targeted areas of the frame would produce fruitful yields, a perfect balance between stiffness, strength and compliance at minimal weight.
The third major factor which optimizes the frame’s strength is through the careful, detailed, and meticulous engineering skills of bike makers, alongside the use of highest quality, premium name brand carbon materials.
Take a look at the three different carbon materials being used in Felt’s bicycle line-ups:
|High Modulus||Ultra-High Modulus||Ultra-Hybrid Carbon (UHC)|
|● 700ksi fiber blend
● Tensile strength 8 times greater than 3/2.5 titanium
● Stiffness 3.3 times greater than 6061 aluminum
|● 800ksi and 700ksi fibers
● 27% stiffer than material used in High Modulus frames
● Lower capacity for retaining resin
● 20% lighter
● Same stiffness and strength as in High Modulus
|● Blend of 588GPa, toughest carbon fibre and stiffest carbon fibre
● Chassis with unparalleled compliance, lightness, strength, performance, and handling
FELT has never let its customers down with its manufacturing method because of their thorough investment in design, testing, experiences and the costs that go along for the use of components as well as development.
As a result, they have successfully created a chassis delivering ultimate power with no compromises.