General Mechanical

General Mechanical

Bending residual stress for composite beam

    • rahmanmahfuz11
      Subscriber

      Hello all, I am trying to simulate the bending residual stress for a cantilever composite beam in ansys static structural. However, I think just giving a displacement at the free end and then setting it to zero again is not giving me the residual stress as the values I have got are too small compared to the bending stress. If anyone would kindly tell me how could I do it, I would be grateful.

      Thanks in avdance.

    • peteroznewman
      Subscriber
      Please describe the material model in detail that you have used and expect to show residual stress.
    • rahmanmahfuz11
      Subscriber
      Thank you for replying. My model is slightly different than a simple cantilever beam.
      It is a tube with an HDPE (Polyethylene) liner of 4mm and 8 layers of carbon (epoxy carbon UD/woven 395GPA Prepreg) and glass fiber (Epoxy S-glass UD) in resing epoxy. I am trying to bend it on a roller and then straight again to see the developed residual stress. All the materials are chosen from the default ansys material database.
      The following images contain the model and the boundary conditions. For computing residual stress, the pressure BC has been suppressed, only displacement and the fixed supports are used.

      The tube looks like this after bending.


    • peteroznewman
      Subscriber
      I can't comment on your specific materials, since I don't use composites in ANSYS, I use them in NASTRAN. I can comment on how to see the residual stress when using a Plasticity material model. The method is to apply a Force in step 1, then set the Force to 0 in step 2. As the force ramps off in step 2, the material at the core that is still elastic pulls back against the material at the surface that experienced plastic stretching, until an equilibrium is found. At this equilibrium, there is some permanent deformation and some residual stress. The material at the surface that was plastically stretched in tension ends up in compression while the central core ends up with some tension to create the equilibrium.
      You need to study how damage is accumulated in composites and whether damage will result in residual stress. Perhaps someone who knows will answer.
    • rahmanmahfuz11
      Subscriber
      These are the default properties of carbon fiber in ANSYS. I don't think any plastic properties are included here.

      However, there is a list of plasticity properties that I can add to a material. This is that list. Would you please help me select the plasticity properties I might need for a residual stress simulation?

    • peteroznewman
      Subscriber
      Plasticity doesn't apply to composite materials. I only mentioned it as an example of how to look at residual stress.
      You need to study how damage is accumulated in composites and whether damage will result in residual stress. Perhaps someone who knows will answer.

    • rahmanmahfuz11
      Subscriber
      Got it. Thanks a ton, mate!
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