Help Center

Carbon Fiber is a polymer and is sometimes known as graphite fiber. It is a very strong material that is also very lightweight. Carbon fiber is five-times stronger than steel and twice as stiff. Though carbon fiber is stronger and stiffer than steel, it is lighter than steel; making it the ideal manufacturing material for many parts. These are just a few reasons why carbon fiber is favored by engineers and designers for manufacturing.

The simple comparison between carbon fiber, steel and aluminum can be understood using common forms of the high-strength versions of these materials.   Compare the mechanical properties, the modulus of elasticity (stiffness) and the tensile strength (strength under tension) of these three materials:

1.      Carbon fiber T700S from Toray, a standard modulus high-strength fiber, in an epoxy 250 F-cure composite
2.      Alloy steel AISI 5130, a low hardenability alloy steel with moderate strength and good toughness
3.      Aluminum alloy 7075-T6, a standard aerospace aluminum alloy

As a comparison, steel has a tensile modulus of about 29 million psi (200 million kPa). Thus, the strongest carbon fibers are ten times stronger than steel and eight times that of aluminum, not to mention much lighter than both materials, 5 and 1.5 times respectively.

In addition to very low thermal expansion and good corrosion resistance, carbon composites offer outstanding characteristics for lightweight construction: Compared to metals, the weight can be substantially reduced in many applications.

In the best cases a carbon composite will achieve the mechanical properties of steel with only one fifth (20%) of its weight.

Unlike metals, the material properties of a composite are created during part production, through the orientation of the reinforcement fibres in the part. The better the fibre orientation can be optimised for the particular loading of a component, the higher the performance/weight ratio.

Almost all carbon fiber is made from a common industrial fiber called polyacrylonitrile fiber, also known as PAN.  Most PAN fiber is used to make acrylic fiber.  It is also used to make carbon fiber with a pyrolizing process, which means it is heated to ultra high temperatures to remove all elements except the carbon.  Most carbon fiber is sold at this point and it has a tensile modulus of 33 million pounds per square inch (MSI).  (Tensile modulus is a measurement of stiffness.)  This 33 MSI fiber, if seen up close, looks like a a redwood tree trunk, with deep fissured bark.  If processed further, the “bark” is stripped off, leaving a smoother round fiber that is smaller in diameter.  More of these fibers can be packed into a smaller space, making it have a higher stiffness per cross sectional area.  42 MSI fiber is the result and it is informally known as Intermediate Modulus fiber or IM fiber.  The benefit is that you can use less material to get the same stiffness and therefore a lighter structure.