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How is Carbon Fiber Made?

The possibilities are endless for what can be made from carbon fiber. It’s light, strong and easy to manipulate into just about any shape. The versatility of carbon fiber can be attributed to both how it’s made and what it’s made from. Let’s break down just how, exactly, carbon fiber is manufactured before it’s used to create your next project.

Materials

The foundational component of carbon fiber is (you guessed it) carbon, combined with organic polymers. Carbon fiber is relatively new to the manufacturing industry, with really only a handful of companies who specialize in making the material. Each manufacturer varies slightly in their formulas and guard their specific combination as a trade secret.

However, it’s understood within the industry that carbon fiber is generally made using polyacrylonitrile (PAN), rayon or petroleum pitch. These materials are all organic polymers, meaning they are long strings of molecules bound together by carbon atoms. The specific materials used to make the carbon fibers impact the material’s quality, grade and can create certain effects.

Process

About 90 percent of all carbon fibers are produced through PAN processing. We’ll focus on this material since it’s by far the most common. For the carbon fiber making process, PAN is called the “precursor” – the raw material being used to build the carbon fibers.

  • Stabilizing: To start, the fibers must be chemically manipulated to create more thermally-stable ladder bonding between molecules. Fibers are heated to between 390° – 590° F for a half hour to an hour and a half. The fibers pick up oxygen molecules from the air and rearrange their atomic bonding pattern.
  • Carbonizing: After the material has been stabilized, the precursor is pulled into long strands and heated to 1,830° – 5,500° F, this time deprived entirely of oxygen. Without oxygen, the extreme heat won’t burn up the fibers, but rather cause its atoms to violently vibrate and expel just about all non-carbon atoms. The carbonization leaves long, tightly bonded chains of almost all carbon.
  • Treating: The carbonizing process leaves the fibers with a surface that doesn’t bond well to epoxies and other materials used to make the carbon fiber composite. To remedy this, the surface is slightly oxidized. This achieves two things. First, better chemical bonding properties and second, an etched/rough surface that’s better for mechanical bonding. While the oxidization process can be completed in multiple ways, it should be done carefully to avoid tiny surface defects which could lead to fiber failure.
  • Sizing: The final step in manufacturing carbon fiber is to coat the fibers so they won’t be damaged during winding or weaving – this is called sizing. Coating materials vary and are selected to be compatible with the adhesive used to form composite materials. Some examples of coating materials are epoxy, polyester, nylon, urethane and more. From here, fibers are then twisted or woven into ropes of various sizes.

Now that you know a little more about how carbon fiber is made – let’s put it to work. Give us a call to learn about how carbon fiber can improve your next project and potentially save you money, too!

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