CARBON FIBER

WHAT IS CARBON FIBER?

Once limited to applications in the aerospace industry and the pinnacle series of motor sports competition, carbon fiber has been the material of choice for high-performance bicycles, wheels, and other cycling components for several decades. Carbon fiber provides bicycle engineers with the potential to create a riding experience that offers an unmatched combination of comfort, stiffness, strength, and efficiency. With its incredibly high strength-to-weight ratio and malleability, carbon fiber is second to none for building the world’s best bicycles. In its raw form, carbon fiber is a conjoining of thin, strong fibers. These fibers come in a variety of grades based on overall strength and modulus.

The higher the modulus, the stiffer and lighter it is—in the simplest of terms, “modulus” is a term for the stiffness of a given material. However, this doesn’t mean that the best bikes are completely constructed from high-modulus carbon fiber. On the contrary, the key to building bikes is to mix and match different types of carbon fibers in order to find the ideal balance between stiffness, strength, and weight. In addition, no bicycle is crafted from carbon fiber alone—it’s used in conjunction with resin, which acts as a bonding agent to hold the structure together. It’s a complex puzzle to create a carbon fiber bike that not only rides well, but can sprint away from the competition. But just like how the finest food ingredients demand the skills of a master chef to yield a truly exquisite meal, bicycle frame materials require engineering expertise to produce a truly great bicycle.

"The key to building bikes is to mix and match different types of carbon fibers in order to find the ideal balance between stiffness, strength, and weight."

ALL ABOUT UNIDIRECTIONAL.

Unidirectional carbon fiber is the most common type of carbon fiber used in bicycle construction. As its name implies, a sheet of unidirectional carbon has its fibers oriented in one way, or in parallel (as in, “one direction”). To help visualize the characteristics of unidirectional carbon fiber, think of a wine glass. If you drop it on a hard floor, it will shatter because it’s so thin, stiff, and brittle. Now think of a plastic cup. You can drop it and nothing happens because of its flexible properties. Carbon follows similar rules. As you increase the modulus, the stiffer and more fragile the fibers become. And if you go in the other direction, the fibers are not as stiff, but more compliant and durable. As such, there is no such thing as a bicycle frame constructed completely from high-modulus carbon fiber, at least not one that would be safe or pleasant to ride.

It would likely break apart the first time you hit a big enough pothole. High-modulus carbon fiber can be tricky to work with and there must be balance between stiffness, weight, strength, and durability. Also remember that not all unidirectional carbon fiber is created equal—there are countless varieties and versions created by various composite manufacturers around the world, each one with different weights, durabilities, vibration resistance, and other attributes that can greatly affect how a completed structure will perform. Think of different types of carbon like paper: Plain, white sheets of paper are intended for computer printers; thicker, colorful construction paper is ideal for crafts; and thick-stock, supple, and durable paper is best for archival printing and bookkeeping. Every type has its unique properties and ideal uses.

WOVEN INTO THE MIX.

In addition to unidirectional carbon fiber, woven carbon fiber is also very commonly used in bicycle construction. As its name implies, woven carbon is composed of relatively narrow strands of unidirectional carbon fiber woven together, just as one would do with textiles on a loom. Because carbon fiber is such a uniquely versatile material, yet has inherent weaknesses when it comes to the way its threads are oriented, weaving carbon strands together gives composite experts and engineers more ways to manipulate the structure that they’re designing. But just like with unidirectional carbon fiber, not all woven carbon fiber is created equal. All have their unique properties. One of the very best types of carbon fiber that we’ve long used to elevate the performance of our bikes is TeXtreme. Read on to discover what makes TeXtreme so special.

WHAT MAKES TEXTREME SO SPECIAL?

Because Felt Bicycles was the first company in the bike industry to utilize TeXtreme in its products, many cyclists believe that it is a type of carbon created by, or unique to, Felt. However, this is not the case. TeXtreme is a type of woven carbon fiber created by the Swedish materials company, Oxeon, who make it available to dozens of brands in a wide array of industries including aerospace and motor sports. However, it’s still a rarified material in bicycle construction due to its high cost. However, pursuant to our mission of giving all cyclists the best riding experience imaginable, we’re okay with taking the monetary hit in order to create the very best bicycles in the world. So what makes TeXtreme ideal for use in bikes? Strength and weight.

MORE THAN MEETS THE EYE.

TeXtreme features a unique makeup that Oxeon calls “Spread Tow” technology. “Tow” is a term that refers to the specific type of thread used to weave carbon fiber sheets. TeXtreme’s Spread Tow design offers the strength of two layers of unidirectional carbon at around half the weight. Also, similarly, TeXtreme requires less resin than a comparable combination of fibers, further reducing the overall weight of the finished structure. As an added bonus, TeXtreme’s wide “checkerboard” pattern is also quite aesthetically pleasing. You can learn more about TeXtreme at Oxeon’s website. But it’s important to remember that TeXtreme is but one ingredient in creating a Felt bike, which includes several other types of carbon fibers skillfully laid up by master craftspeople from complex lay-up schedules developed by the best bicycle engineers in the world. "But, wait," you say. "What's a lay-up schedule?" We've got you covered—Keep on reading.

"It’s important to remember that TeXtreme is but one ingredient in creating a Felt bike."

WHAT ARE LAY-UPS & SCHEDULES?

The term “lay-up” or “lay-up schedule” refers to the overall recipe for how the various types and shapes of carbon fiber sheets are pieced together (or “laid up” in a mold before resin is added) during the bicycle frame manufacturing process. A schedule is often composed of lists, charts, diagrams, or some combination thereof, which details the various dimensions, moduli, fiber orientation, and resin content for each piece. Together, this information provides the road map that leads to a finished frame. Every bike model can contain hundreds of these entries. Many people think all carbon bicycle construction is the same. And, sure, every bike manufacturer can tweak ply orientations and materials, and use different resins to hold everything together. But if you don’t put in the time during the design phase to truly understand structural relationships, you’re just creating generic bikes.

FRAME DEVELOPMENT & SIZE SPECIFICITY

Through extensive Computer Aided Design (CAD), Finite Element Analysis (FEA), and prototype testing by Felt’s professional riders, our engineers are able to ascertain which fiber types to use. The goal is to precisely position each piece on the frame to take maximum advantage of its specific properties. In some areas, we may use intermediate modulus material because it has the potential to offer an ideal balance of stiffness and strength. In other areas we opt for high-modulus material for additional stiffness. TeXtreme is used in many models, as well, often as a way to add strength and durability without excessive weight. Every frame design behaves differently, and every frame size requires a unique lay-up. That's why we've been creating size-specific frames for decades, to ensure that every cyclist shares the same riding experience.

The blending of these materials can vary greatly. For example, stiffer fiber plies are typically used in areas requiring maximum performance, such as the bottom bracket and down tube. Higher-strength fiber is best for areas more susceptible to impact. The same attention is applied to changes in frame size. As tube diameters and intersections change, so will ply orientation and material specifications. These determinations take months, even years to finalize considering all the variations. Once the ideal blend of materials and ply orientation is determined, the lay-up schedule is finalized, outlining every detail of the construction process. Then the frame is produced in the factory and made ready for real-world test-riding before being mass-produced for the marketplace.