Equivalent elasticity modulus

[Kooler]

Thank you so much for reading this post, I hope you can help me with this topic.

I am reading a book where says something like: "The elasticity modulus of material A is EA GPa, the elasticity modulus of material B is EB GPa. So, assuming that both materials are X% on the piece, the resultant one is E". On the book the values that appear are 110GPa and 3GPa, so the final result is 9.4GPa with 50% of each material.

Does anyone know how is this calculated?

Thanks a lot!

 

[GBor]

Kooler,

Is the 50% by weight or by volume? I believe the calculation is generally:

E = VaEa + (1-Va)Eb, but that comes out closer to 57GPa. If you add some percentage for void, it will drop. Check out

http://math.materials-sciences.com/webMathematica/MSC/start.html

and look at the lamination theory calculator.

 

[Kooler]

GBor, this doesn't work. Is what I thought at first but it is not true.
I have been searching on the internet and it seems there is a formula from Enst which is used tocalculate it. But I haven't found this formula.
Thanks for helping, and hope better luck next time.

 

[Compositepro]

I agree with Gbor. Perhaps your book is talking about flexural modulus?

 

[GBor]

If the 50% is by weight, then you have to calculate the volume fraction for this equation. If you have very little volume of modulus A, then the equation may work. In this case, it would take about 6% of "A" by volume (94% of "B"), but this is just a "Law of Mixtures". What type of composite is it? Continuous Fiber? Short Fiber? Microsphere?

 

[Kooler]

It is about copper.
I will try to do with volumes, but I am not sure wether it will work or not.
As soon as I have it done I will tell you.
Thanks!