Sandwich structure 3 point bending test

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Hey there,

 

 

I am comparing different ways to simulate a sandwich structure going through a 3 point bending test. In order to check if I am defining well the structure, I have calculated theoretically the maximum stress and compared it to the different simulations I have done. Below are the results of a 3 point bending test applying a total force of 110N on a test-tube of 100x15x10 mm :

 

Theoretically: Maximum stress- 7.33 MPa

 

1 solid (3D elements): 

<?xml version="1.0" encoding="UTF-8"?>Slide1.JPG

 

Plies (2D elements)

<?xml version="1.0" encoding="UTF-8"?>Slide2.JPG

 

Core (3D) +Plies (2D):

<?xml version="1.0" encoding="UTF-8"?>Slide3.JPG

 

The total dimensions of the three test-tubes are the same, as well as the boundary conditions. Therefore, I don't understand why I am obtaining such different stress results nor which would be the best option to simulate this test.

 

I hope you can help me with my problem.

 

Thanks in advance!

 

 

 

 

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2016

    Hi Monica,

     

    Can you request Composite Stress (CSTRESS) and check if that matches with your theoretical calculations?

     

    If you still see a huge change when you compare, kindly share the calculation sheet and the model file.  Use this File Transfer LINK

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2016

    FYI,

     

     

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2016

    Hey Prakash,

     

    The results I am obtaining are still too high. I have attached the model file in the link you provided.

    <?xml version="1.0" encoding="UTF-8"?>Solid sandwich composite stress(2).jpg

     

     

    Here are the theoretical calculations:

     

    <?xml version="1.0" encoding="UTF-8"?>proveta.jpg

     

    Thanks!

     

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2016

    Hi Monica,

     

    Can you cross check the unit system?

     

    The length of the block is 0.1mts and the applied force is in Newtons?

     

    This makes Stress in N/m^2?

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2016

    Yees, exactly!

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2016

    Hi Monica,

     

    Can you scale the model so that the units become MilliMeters and not meters?

     

    Also, in your calculations, you have a point load where as in your model the load is distributed among three nodes. Please check this as well. :)/emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20'> 

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