I won't comment directly on this, but will refer you to the articles at the link in post #6 above.

"The Basics" article discusses the nature of physical, mechanical and chemical properties of different materials. Physical properties are things like density, color, electrical conductivity, magnetic permeability, and thermal expansion. Mechanical properties include things like elongation, fatigue limit, hardness, stiffness, shear strength, tensile strength, and toughness. Finally, chemical properties include reactivity, corrosion resistance, electrochemical potential, irradiation resistance, resistance to acids, resistance to alkalis, and solubility.

Since you asked specifically about carbon fiber, read the article "Carbon Fiber Boasts Tremendous Potential" and note what it says about elongation.