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transversal isotropy for beam elements

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  • transversal isotropy for beam elements

    Hi all,
    I am doing some simulations for UD pultruded composite beams in Abaqus. In my case the considered profiles are symmetric and solid. I wrote the following simple VUMAT to specify the material behaviour ('1' being the fibre direction):

    e11 = props(1)
    g12 = props(2)
    v12 = props(3)

    do k = 1, nblock

    C Update stresses (direct & torsion shear)
    stressNew(k,1) = stressOld(k,1) + e11 * strainInc(k,1)
    stressNew(k,4) = stressOld(k,4) + g12 * strainInc(k,4)
    C Define transverse strain increments (direct)
    strainInc(k,2) = -v12 * strainInc(k,1)
    strainInc(k,3) = strainInc(k,2)

    end do

    This seems to work fine, but I still have two questions:
    1. The subroutine manual states that it is necessary to define the transverse strain increments. However, I notice the results are the same when this step is omitted. Does Abaqus actually use these strain increments, and how?
    2. Using a VUMAT, the transverse shear stiffness needs to be defined separately. When K12 = k G12 A; can we use the same shear correction factor k as for isotropic material? In some first checks against analytical calculation of a cantilever beam and simulation of a solid model this seems to hold fairly well, though there exists some error.

    Thank you.
    Last edited by Joren; 2018-10-09, 06:18.

  • #2


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    If you need subroutines: as an introduction get the file User Subroutines with ABAQUS.pdf

    Good luck



    • #3
      Hi Frank,

      Thanks for the links.
      There is also the Simulia Learning Community (though it's not the most user-friendly interface)

      But in the past I have always found the most interesting information on this forum, which is why I post it here.


      • #4
        The transverse strain increment is only used for certain element types, and only becomes important for certain loading modes. Yes, you can estimate the transverse shear stiffness from the isotropic terms. I have also found that the transverse shear stiffness is often not very important.

        Jorgen Bergstrom, Ph.D. PolymerFEM Administrator