bending stiffness?

[floch]

Hello
(sorry for the mistakes)

I begin in composite analysis and i have a problem. I don't found the formulation to calculate the bending stiffness of the sandwich panel,with two orthotrope skins (0°,45°,0) and nomex hexagonal core.

here are the data of the materiel
for the skin (carbone /epoxy)

plies thikness e=0.75mm
Young's modulus Exx=62400Mpa
Eyy=58850Mpa
Shear modulus Gxy=3950Mpa
Poisson vxy=0.05
Out plane shear mod Gxz=Gxy=600Mpa

For the nida

thickness e=18mm
Out plane shear mod Gxz=41Mpa
Out plane shear mod Gyz=23Mpa
Compressive modulus Ezz=138Mpa

I would calculate the equivalent bending stiffness.
i found formulation but it's performed for beams (with supposition that the core is an isotrope materiel) and not for a plate with nida.
I ask me how calculate this bending stiffness easily for my sandwich panel .

Have you an idea? , please

Thank you

 

[SWComposites]

Use laminated plate theory; there are many text books available. Treat the core as a layer (ply) with it properties, and use low values for the in-plane values (this has been discussed before on this forum).

 

[RPstress]

This has indeed been covered many times. Try the Google search option for Eng-Tips at the top of page.

Also the references in
thread327-172605
thread367-219620