High modulus fiber is simply a more refined carbon fiber. The term "modulus" refers to "Young's Modulus", a measurement of stiffness. The higher the number, the stiffer the fiber. The process for making the higher modulus fibers involves stripping off the outer layers of the individual fibers, leaving the stronger core. A few companies are using a limited amount of high modulus fiber. It is expensive, and is used sparingly. The most advanced bicycle frame as of this writing is made with high modulus carbon co-mingled with boron fiber. The boron fiber is interesting because of its incredibly high stiffness in compression. Combined with the high tensile stiffness of the carbon, a synergistic result is achieved where the overall stiffness of the tube is greater than that predicted by the properties of the individual fibers. The ultra tough boron fiber also protects the more brittle high modulus carbon fiber. These advanced properties have found favor in the landing gear of fighter jets as well as a modern bicycle frame.
With Lance Armstrong winning the Tour de France 7 times in a row on a carbon fiber frame, the bicycle world has finally accepted carbon fiber as the material of choice. But few companies are actually making their own frames. Traditionally, the lower cost metal frames have been made in Asia with companies simply labeling them with the brand’s decals. Because of the labor intensity of making carbon fiber frames, most of them are being made in Asia as well. Some companies are simply buying carbon tubes and lugs from Asian suppliers and bonding them together in the home factory and labeling them as “made in Italy” (or other western country). A few companies are still making carbon frames in the US and some new, small shops are taking the place of the traditional custom steel frame builder.
