Adding elastic / youngs moduli?

Question

I'm trying to find the elastic modulus of a combined material consisting of two layers, say compound A and compound B. The two are stacked on top of each other and the elastic modulus for each separate component is known. How do I find an elastic modulus to approximate both of them stacked on top of each other? At first I thought it was as simple as multiplying each modulus by its proportion of the total length and then adding these two numbers, but I believe it's a little more complex than that. Thanks for any insight!

Answer 1

OK...

E = (1-V)Em + VEf

I have a lecture hand out that will answer this.

I am uploading it to a file hosting site atm.

http://www.mediafire.com/?92xylze9g9g

That should cover it.

Answer 2

Not quite sure how the two materials are aligned.

If the force is along the interface between the materials then the strain will be the same for both materials.

Youngs modulus = Stress/ strain

so you can write two equations of Stress1/E1=Stress2/E2

Where stress is Force divided by area.

You also know what F1 + F2 equals so you can work it out.

If the stress is at right angles to the interface then you find the strain for each material and divide the stress by the combined strain to obtain E