Equivalent Modulus

[audacious1234]

Hello All,
Question:

I have a tensile modulus for a face sheet of honeycomb panel which is composed of 6 layers of phenolic (0/90/0/90/0/90). And I would like to calculate tensile modulus for individual layer. Is there any formula which calculates it?
OR
If I know value of modulus for an individual ply is there way to calculate equivalent modulus for a face sheet composed 6 layers of phenolic (0/90/0/90/0/90).

I am new to this area of composites therefore any help will be highly appreciated.

Thanks a lot for your time.

Regards,
Audacious1234

 

[SWComposites]

Are the layers unidirectional tape or fabric?

Layer properties can be estimated from laminate properties by making some assumptions.

Laminate properties can be calculated from layer (ply) properties using Classical Laminated Ply Theory, which is given in many text books, and probably can be found on the web along with some CLPT codes.

The formulas are not simple enough to write here.

 

[Onda]

Here you have a very good software that perform CLPT.

http://www.thelaminator.net/

You can download and try It.
Onda

 

[GBor]

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

has online calculators that may be useful, but SWComposites is right that you will need to make some assumptions about void volume, fiber volume, etc.

 

[RPstress]

SW's first question is the most important. If this is a reasonably symmetric cloth (perhaps five harness satin weave, plain weave or twill weave, etc.) then the properties of the individual plies should be quite close (or perhaps the same) as the laminate properties for 0 and 90 layups. (The assumption here is that the individual plies have very similar properties at 90 to those at 0, and that the layup is either symmetric across the core or that the depth of core is large compared with face skin thickness.)

If it's all unidirectional plies then you need to know a bit more about the material. Are the fibres carbon or glass (or maybe Kevlar, etc.)? What is the fibre volume fraction? (Fibre volume can be found from knowing areal weights of fibre and resin and densities.) Combinations of cloth and UD just get a bit more complicated.

So, as SW says, you need some assumptions, but it's possible to back out ply stiffness properties from laminate ones.

NB: Getting strengths rather than stiffnesses is much harder.

 

[NickE]

The above are all correct. One good source for the fundamentals is here:

http://home.comcast.net/~brandihampson/ep.html

click the composite materials link

This is from the professor who taught my composites course in university... IMHO a very good course taught by a great professor.


nick

 

[SandwitchPanel]

To add to the expert comments above, if you are using a pre processor such as FEMAP, which is what I use, when the layup is defined there is a convenient feature in FEMAP called "COMPUTE". It gives you different properties of the particular layup you define on the fly. The properties include the layup tensile and shear modulii (equivalent). Some other useful results are the ABD matrices. With these matrix results, you can get an idea of the membrane bending and coupling properties of the layup. I am sure other preprocessors may have this feature too.