Dear friends FEM FEMAP HONEYCOMB CO 1

[cgcg1]

Dear friends FEM FEMAP HONEYCOMB CORE

I have a question about filling up the Material property Tab in Femap. Let’s say we have honeycomb aluminum core sandwiched between the two thin aluminum face sheets. I understand that the core material in a honeycomb sandwich panel can be modeled as a 2D-Orthotropic Material Type. (Mind you I,m not addressing the face sheets which are modeled as an isotopic aluminum material). When you open the 2D-Orthotropic material type you get the the tab (please see attached picture). Now the material property Specs that is usually given by the manufacture of the aluminum Core is as follows:

Plate Shear Modulus:
L direction 90 ksi
W direction 38 ksi

Plate Shear Strength:
L direction 460 psi
W direction 300 psi

Bare Compression Modulus:
220 ksi

Bare Compression Strength:
770 psi

Nominal Density:
5.7 lb/ft^3

Now my question is where these values , specially the shear moduli and should go in the 2D-Orthotropic material Tab in Femap (picture Attached).

I really be grateful if someone has experience with this can help me.

Cheers!

 

[BlasMolero]

Hello!,
Please visit my FEMAP support web site where I explain how to define a sandwich benchmark problem posed by NAFEMS:

http://www.iberisa.com/soporte/femap/composites/nafems_benchmark_composite_test_r0031_3.htm

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[cgcg1]

Thank you very much Blas, sorry for late reply I am new in this forum website took me a while to find out how I reply to you to thank you. I visited your website it was excellent. Correct me if if I’m wrong, the way I understand it the “Lam Ply YZ Shear Stress” and “Lam Ply XZ Shear Stress” that we get from Femap results are “OUT OF PLANE” (Transverse) Shear Stresses which correspond to Shear Modulus values of “2z” and “1z” respectively, that were entered in the “2D Orthotropic” material Tab in Femap. Thank you very much and looking forward to hear from you

Cheers!

 

[cgcg1]

To Clarify, I meant, "Shear Modulus values of “2z” and “1z” respectively, that were entered in the “2D Orthotropic” material Tab in Femap. Thank you very much and looking forward to hear from you" are for the CORE Material only. As for the Face sheet layers, they are "isotropic Aluminum material" which will be Top and Bottom layers of the Layup card.

Thanks

 

[BlasMolero]

Hello,
One of the more difficult aspects of working with composites is getting realistic, usable material data. All are asumptions: is possible that the FEA model runs Ok in pure flex, but the same material data is not valid when a lot of shear or twist is prescribed to the structure, then caution with material data: a FEA model is only as good as the asumptions included on it.
Said the above, FEMAP requires the entry of 5 values:
• 2 Young’s Moduli for the material’s primary directions.
• An inplane 1-2 Shear Modulus (G12, ie, GXY).
• 2 Transverse Shear Moduli, 1z & 2z (ie, GXZ & GYZ)
• The 1-2 Poisson Ratio, the 2-1 Poisson Ratio is not required. The symmetry of the material stress tensor allows FEMAP to calculate it based upon E1, E2 and v1-2.
Please note FEMAP use 1 & 2 instead X & Y, this is because you need to define first the material orientation using command MODIFY > UPDATE ELEMENTS > MATERIAL ORIENTATION, this is the "1" primary direction, and "2" is the ortho direction. Also if you want to compute the index failure you need to enter the limit stress material values (the values with the "strength" word in its name).

Back to your data:
• I miss values of the Young`s module E1 & E2, ie, Ex & EY. This is mandatory.
• In-plane shear modulus G12 (ie, GXY) is missing. You can always use the shear modulus formula: G = E / [2(1 + ν)]
• With your data you can enter Shear Modules GYZ=38000 psi (W) and GXZ=90000 psi (L).

In summary, with your data I would use the following data entries:

Also please remember that the classical lamination theory assumes the laminated plate is non‐shear deformable, and do not account for the out‐of‐plane stresses. Accordingly, the transverse shear moduli of the core must have a high value.
To estimate the interlaminar stresses FOR SANDWICH COMPOSITE MODELING it is recomended to use the mixing method of 2-D laminates and 3-D CORE:
• In this method, the facesheets can be modeled as 2-D Shell CQUAD4 elements and the core can be modeled as a 3-D solid CHEXA 8-nodes element.
• Be careful when defining both facesheets: they have to be placed at an offset of half the laminate thickness from the solid core!!.

Enjoy!.
Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/