12-27-06 - Why carbon?

Okay, next time you talk about carbon you can use some words as “compressive modulus”…

(Extracted from compositesworld.com. Read the full article here)

Traditionally, rims, spokes and hubs have been made from aluminum because it is one of the lightest extrudable metals, yet durable enough for daily riding. An aluminum rim also is relatively easy to manufacture: The desired cross-section is extruded, then cut to length, rolled and joined at the ends to create the rim. However, because it is an isotropic material, aluminum has the same value – 68 GPa (10×106 psi) – for two key rim properties, tensile and compressive modulus. By contrast, a carbon composite’s fiber architecture can be designed anisotropically, exhibiting much higher tensile modulus – 140 GPa to 240 GPa (20.3×106 psi to 34.8×106 psi) for standard modulus carbon/epoxy composites – but with a compressive modulus as low as 11 GPa to 15 GPa (1.6×106 psi to 2.2×106 psi). Carbon is able to achieve these values at lower rim weight...