In our latest “Sneaker Ingredients” series installment, we focus on carbon fiber. Continue reading for the in-depth story on one of footwear’s most dynamic ingredients…
Made famous in the footwear industry for its use as the shank plate material for Air Jordan XI, carbon fiber is composed mostly of carbon atoms. Carbon fiber is a long, thin strand that measures 0.0002-0.0004 inches in diameter and its strength comes from its crystal alignment – carbon atoms bonded together in microscopic crystals that are lined parallel to the fiber’s filament axis. Thousands of fibers are twisted together to form a yarn, which then can be used independently or woven into fabric. The yarn or fabric is then married with an epoxy and either wound or molded into virtually any shape for use in various products. A small piece of carbon fiber can withstand the weight of many tons, and provides excellent torsion control and corrosion resistance, yet it can crack or shatter altogether if hit with blunt force.
Modern carbon fiber was born in 1958 from the efforts of Dr. Roger Bacon, scientist at the Union Carbide Parma Technical Center in suburban Cleveland, Ohio. The initial goal was to produce a reinforcement for molded plastic components on missiles. These early carbon fibers were produced by essentially charring strands of rayon until they carbonized. This method proved inefficient, however, as the resulting product contained only 20% carbon and possessed low strength and rigidity. The early 1960s saw carbon fiber made by a process utilizing polyacrylonitrile – an inorganic oxide – that yielded a fiber strand containing 55% carbon and much higher tensile strength. Then, in the 1970s, carbon fiber began to be produced from petroleum pitch from oil processing. This raised the carbon content to 85% and afforded great flexural strength. However, compression strength proved to be compromised and the method was soon widely abandoned. Today, about 90% of all carbon fiber is made from polyacrylonitrile and the remaining 10% is made from rayon and petroleum pitch.
Today, the United States, Japan, and Western Europe lead the world in carbon fiber production and the material’s strength rating is currently broken down into five classifications or “moduluses”: low, standard, intermediate, high, and ultrahigh. A modulus is simply a measure of how much pulling force a certain diameter fiber can withstand without breaking. For instance, a low modulus carbon fiber scores below 34.8 million pounds per square inch of pressure while an ultrahigh modulus carbon fiber rates between 72.5-145.0 million psi. By comparison, steel has a modulus of approximately 29 million psi which means that the strongest grade of carbon fiber is 10 times stronger than steel and eight times stronger than aluminum, all while coming in at a significantly lower weight than both materials.
It is used in many applications including aircraft such as the all-carbon fiber composite body of the new Boeing 787 Dreamliner, automobile exteriors and interiors, musical instruments, jackets, t-shirts, vests, and footwear. Carbon fiber began to be used in the mid-1980s on outdoor footwear and subtly crossed over into athletic footwear as its light weight and super strength made it ideal for performance sports. In areas of a shoe where an athlete may benefit from motion control and shape recovery, such as the midfoot and forefoot, carbon fiber is extremely useful and simultaneously lends a high-tech look to the shoe‘s design.
Notable sneakers to employ carbon fiber: Air Jordan XI (shank plate), Air Jordan XX3 (shank plate), Nike Air Flightposite 1 (faux carbon fiber pattern upper), Nike Zoom Kobe 1 (medial/lateral wrap, shank plate).
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