Carbon Zapp A 4040

Carbon Fiber: Essential Bicycle Component

Considered as an unusual space-shuttle composite just ten years ago, carbon fiber is now employed in nearly every bicycle element, from frames and parts to helmets and shoe soles. Carbon fibers are made from carbon, the ubiquitous part that forms coal, graphite and diamond and is a component of each organic chemical and each life form on earth. Carbon is the fourth most common component in the universe and the
Second most abundant part in the human body.

Polyacrylonitrile ( PAN ) fiber, also the source material for acrylic fiber, is made into carbon fiber by heating it to intense temperatures, burning away essentially everything except carbon. The ensuing 5-8 micron ( millionths of a meter ) thick fibers are a tenth the thickness of a human hair and made of carbon atoms strongly bonded together in microscopic crystals aligned parallel to the fibers axis. Robust and stiff, the fibers have a rigidity index of thirty three million pounds per square inch ( MSI ) and a rough surface. Pricey processing can strip off this outer surface to reveal a thinner, smoother
Intermediate Modulus ( IM ) fiber that packs tighter with other fibers for higher stiffness per unit area. A higher priced processing can create High Modulus ( HM ) carbon fibers, which boasts a Youngs modulus stiffness of 42 MSI to fifty five MSI or even more.

Common-modulus fibers are wrapped up together into yarn and woven into fabric. A number followed by the letter K designates how many thousands of fibers are in a strand of the yarn ( as in 3K, for three thousand fibers per strand ). Woven fabric frequently comprises the top layer for cultured purposes, but most carbon fibers in a bike part instead come in flat sheets of tightly packed parallel fibers pre-impregnated with epoxy resin stuck to backing paper. Precisely cut pieces ( plies ) are stacked, or laid up, on top of one another at opposing angles ( sometimes forty five degrees ), to fight forces from different directions. Unlike metals, carbon fiber plies within the laminate structure can be orientated to create a composite structure that may be stiff in one direction and more
Flexible in another. Indeed, plies must be laid up at angles, because carbon fiber, like thread, is powerful if you pull on it but far weaker if you push lengthwise on it or bend it sideways. However , in a carbon fiber tire bead, you do not need strength in tension alone, so orienting fibers at angles and gluing them along with resin allows the plies to work together, opposing forces from all directions. Subjecting the laminate to high pressure and heat in a mold pushes out air and excess resin.

Well-engineered carbon composite parts have high stiffness and strength, low density and high fatigue life but low elongation they cannot stretch or bend much before they break. Screw ups come from not properly engineering the directions and sorts of fibers to deal with the loads.

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