Honeycomb (Femap V7.00-Nastran V70.5) 2

[sbernardini]

Hy to all,

i need to set an analysis of a structure that uses honeycomb.
It is a sandwich laminate of all aluminum, both external skins and core.
The thickness is 10mm.
I need some info on how to set the proper characteristics in femap to be solved with nstran.
Thanks in advance to all sbernardini
Rome, Italy

http://digilander.libero.it/sbernardini

 

[pjhype]

To get the macroscopic behavior of the honeycomb do the following:

1. Assume that the bending and extensional stiffness of the honeycomb sheet is a function of only the facesheet thickness and offset of the facesheets from the neutral axis.

2. Define an equivalent plate of thickness (t*) and modulus (E*).

3. Set the bending stiffness of the honeycomb sheet equal to the bending stiffness of the equivalent plate, i.e.,

EI=(E*)(I*)
2*(E*b*t^3/12+b*t*d^2)= (E*)*b*(t*)^3/12

where b is the width, t is the thickness of one facesheet, d is the distance to the neutral axis.

4. Set the extnesional stiffness of the honeycomb sheet equal to the extensional stiffness of the equivalent plate, i.e.,

AE=A*E*
2*b*t*E=b*(t*)*(E*)

5. This yields two equations with two unknowns. Solve the equations, and you have your equivalent plate. Input (E*) into your model on the material card, and (t*) into your model on the property card.

pj

 

[BJM]

I am not familiar with FEMAP but I have done a lot of honeycomb analyisis with NASTRAN. Make sure the PSHELL NASTRAN card has the BSP and TS/T fields filled with values.

The Bending Stiffness Parameter does what was mentioned above but in the way NASTRAN expects. It allows you to put in the correct material props for the facesheets and the BSP will scale up the bending stiffness.

The TS/T allows the shear flexibility of the core to be modelled. Your actual stiffness will be much lower than what beam bending calculations would suggest. I used to use a MAT8 card to define the core material.

 

[nmackaron]

Check out the following site for more detailed information using Nastran:

http://femci.gsfc.nasa.gov/femcibook.html