Can the Young's Modulus of a material change? 1

[Barry1492]

Can the Young's Modulus of a material change?

If I heat up a material, it can become more elastic. If I freeze it, it can become more brittle. Do we say that the Young's Modulus has changed?


I ask this because I had a recent conversation with a biochemist who was telling me that the Young's Modulus of a carbon fiber bicycle frame changes after hard use. Technicaly he was talking about fatigue. However, a frame can get less stiff over time. Do we say that the Moduls has changed? Has the material permanently deformed? or is it due to cracking that weakens the over all stucture?

Thanks for any input - Barry

 

[SWComposites]

Yep, fiber and resin moduli are both functions of temperature, resin more so than the fiber. Brittleness is a strength property, not a modulus. The modulus of a composite can decrease with the number of load cycles, due to degradation and cracking in the resin, though the load levels have to be fairly cloase to the ultimate strength of the material to see any measurable loss of modulus.

 

[Barry1492]

Re: Brittleness

Thanks for the clarification. I was thinking that brittle materials had a low strain to failure vrs...say...rubber, but I guess you are right. That has nothing to do with its stiffness (ie modulus).