From Velonews
Jack,
Your question on modulus in composites, the answer applies to materials in general. Modulus (or more specifically Young’s Modulus) is the term used to describe a material’s ability to deform under the application of load. If a material deforms very little, the Modulus is thought, in a relative sense, to be high. Aluminum has a modulus of 10msi, Titanium’s modulus is 15msi and Steel is 30msi. As you can see aluminum is 1/3rd as stiff as steel so this is why aluminum frames have to be built using large diameter tubing to be competitive with the stiffness of steel frames. This is the only way to get the stiffness you need to make a nice riding bike using aluminum tubes.In composites, the term modulus holds the same meaning. The modulus is a relative indication of the stiffness of the particular fiber or component. This is an often-misused term in the context of your question. Sometimes manufactures will use a very small amount of high modulus fibers mixed in with the standard modulus fibers and call the unit a high modulus unit.In carbon fiber, there are numerous different moduli available as follows: Type Modulus (msi)
The trade-off between the different modulus is the toughness and price. The higher you go in modulus the more brittle the material becomes. It is rarely justifiable to use 100 percent Intermediate or High modulus material in sporting goods, especially bicycle frames and components. Bicycle components benefit from longer fatigue life and greater toughness. We can design for stiffness by engineering larger diameter tubes and optimized orientation of the fibers, i.e. what we call the laminate schedule. The final result being a high performance affordable composite structural component. Finally, directly to your question, the industry in general uses approximately 95 percent standard modulus fiber, 4 percent intermediate and 1 percent high to very high modulus fibers.
John Harrington
Vice President- Bicycle Products
Easton Sports