Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Tip deflecton of cantilevered beam made of material with different stiffness (EI)

  1. Mar 30, 2009 #1
    Hi
    For an initial approximate, I am modelling an aicraft wing as a cantilevered beam. I want to model the beam to incorporate the different materials used; a composite plate is sandwiched between a foam material and therefore the stiffnesses are different. How can I take this into account or figure out the overall stiffness and hence calculate the tip deflection? I plan to eithe model and lift distribution as triangular or elliptical with the peak load at the root.
    For simplicity, the cross section is rectangular.

    Also, as the foam is wider than the composite plate and so the moment of inertia, I, is different. How do I model this? Here is a sketch (left hand side is clamped, and RHS is free):

    ==============================
    Foam, thickness 10mm
    ---------------------------------------
    Composite, thickness 3mm
    ---------------------------------------
    Foam, thickness 10mm
    ==============================

    The cross-section looks like:

    =====================
    Foam, width 160mm
    -------------
    Composite, width 95mm
    -------------
    Foam, width 160mm
    =====================

    Thank you in advance.
     
  2. jcsd
  3. Mar 31, 2009 #2

    nvn

    User Avatar
    Science Advisor
    Homework Helper

    aa2105: t1 = composite thickness, t2 = foam thickness, b1 = composite width, b2 = foam width, E1 = composite tensile modulus of elasticity, E2 = foam tensile modulus of elasticity, n = E1/E2, M = bending moment, I = (n*b1*t1^3)/12 + 2(b2*t2^3)/12 + 2*b2*t2*[0.5(t1 + t2)]^2. Now compute deflection as usual. Bending stress in foam is M*(0.5*t1 + t2)/I. Bending stress in composite is n*M*(0.5*t1)/I.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Tip deflecton of cantilevered beam made of material with different stiffness (EI)
Loading...