CTE: coefficient of thermal expansion - Secant Method - Ansys

[Xuxa]

Hello,



I have to perform a thermo-mechanical simulation in Ansys WB and I have to provide the cte of a material.

I have few experience with thermo-mechanical simulation.

I have got a document with the material properties of this material; there I have the Tg (glass transition temperature)

and two coefficients: cte1 (below Tg) and cte2 (above Tg).



--> How should I calculate the CTE for a temperature range (e.g. -50 < Tg < 300) ? <---



Usually I have measurements with DeltaL/L0 for different temperature T and I use the secant method:

cte = [(L-Lref)/Lref]/(T-Tref) and I take Tref = 25 C (room temperature).



If I only have 2 values (below and above Tg), how can I calculate the CTE?

And what is the correct Tref?



Can I say, cte = cte1 (for T < Tg) and cte = cte2 (for T >= Tg)

or is it possible to get some temperature dependent curve using the secant method?



Do you also have some good support literature about this problem?



many thanks!

 

[Compositepro]

The secant method is one way to calculate CTE. You already have the CTE so there is nothing left to calculate. Use the appropriate CTE for temperatures below Tg and the other for temperatures above Tg.

 

[Xuxa]

Many thanks for the answer!

My problem is that in Ansys, I must provide the cte using the secant method.
If I just use the 2 CTEs, I have a large discontinuity, I think it is like the tangent method.

If I enter the values cte = cte1 (for T < Tg) and cte = cte2 (for T >= Tg),
what should be my reference temperature, Tg or room temperature?

Is it possible make cte = cte1 (constant for T < Tg) and get a nonlinear curve for T >= Tg ?

thanks!