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Homework Help: Need help with a laminate analysis problem

  1. Jan 1, 2017 #1
    • Thread moved from the technical PF forums so no Homework Help Template is shown
    Hi, I am looking for some guidance on a problem I am trying to solve on laminate analysis.
    This is a flat laminate (9 plies with a thickness of 0.125mm) of unidirectional carbon fibre reinforced plastic with a stacking sequence of:

    Ply properties are as follows:

    E1 = 134 GPa, E2 = 10.3 GPa, G12 = 5.1 GPa and v12 = 0.326

    stress1UT = 2090 MPa, stress2UT = 97 MPa, stress1UC = -1600 MPa, stress2UC = -356 MPa and

    T1UT = 114 MPa

    How do I calculate Nx, the load per unit width in the 0 angle direction at which each set of plies will fail. I do not have any stress or strain values so I am unable to put this into the Tsai-Hill formulae. Is there any way I can calculate the stress and strain values? So far I have calculates the Q, Qbar and A B and D matrices. I do not know how to go further from this.
    In addition to this, I need to find ultimate strength allowing for those plies which fail early.

    I am not looking for plain answers, I would prefer some guidance on how to go about solving this. Any help is appreciated.
  2. jcsd
  3. Jan 2, 2017 #2
    Can you consider this as a plate bending problem, with a stack of plates? It would seem that each plate should bend according to the usual elastic bending model. Then you would need to require that the displacements on the top face of one plate should match those of the underside of the plate above. Then it is a matter of matching such boundary conditions through the whole stack, a bit messy, but possible in principle.
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