Software Use > Creating & Editing Composite Laminates

Effective Laminate Elastic Engineering Constants

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mraedel:
Hello August,

thanks for the explanation. I usually use effective Laminates with a minimum of 4 plies. This example is just a breakdown in the search for a model discrepancy.

My second question remains: I use an orthotropic laminae to create effective laminates. Here for example with (35% 0°, 35% 45°, 30% 90°). As you said, effective laminates are supposed to be symmetric and balanced. Using HyperFEA, the calculated ABD-matrix (attached pic) has a filled B-Matrix, indicating an unsymmetric laminate.

Why is that?

August:
I can't re-create your non-zero B-matrix using those ply percentages with an effective laminate. Using your tape stiffness values from your previous post, I get a zero B-matrix every time.

Is the image of the ABD matrix coming from an unstiffened solid laminate concept?

HyperFEA would not have an impact on how the ABD calculation is done, so this is probably not causing the problem.

mraedel:
The ABD matrix comes from a "One Stack Unstiffened" concept section. I thought that HyperFEA has no impact on the ABD-matrix calculation. I just wanted to illustrate the workflow.

The model is a curved shell panel in ANSYS using Shell181 elements as well as Link180- and Beam188 elements for the representation of an actuator.

I'll try to prepare a simple model.

Btw: the same happens for an isotropic material. Something is wrong.

mraedel:
I created a generic model and can reproduce the behaviour. Despite isotropic material, the coupling stiffness matrix is populated. How is this possible?

I attached the model. Unfortunately, I can not attach the HyperSizer database (5MB zip) due to the size limit.

I basically created one assembly from the shell model and the components equivalent to the sections (11-22). I chose One Stack Unstiffened concept and isotropic material (Al 2024-T3). I use only buckling and isotropic strength criteria (longitudinal, transverse, shear, von-Mises).

I use version 7.0.53 of HyperSizer.

August:
Based on the ABD matrix you're showing, it looks like you have the Reference Plane set to "Top" for the component (this is on the Options tab, far-right).

Setting this to Midplane yields a zero B-matrix for the un-stiffened plate in your example.

The default reference plane is Midplane. However, if you have set a reference plane in your FEM, HyperSizer will read it in and set this option for you. This is necessary so that the stiffness matrix in HyperSizer will match the stiffness in the FEM used to derive the loads for the elements in the component.

It is recommended to use a Midplane reference in your FEM for sizing with HyperSizer. Otherwise, you will need to use HyperFEA more frequently to keep the FEM loads in sync with your design.

-August

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