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Homework Help: Young's Modulus of a Composite

  1. Oct 28, 2014 #1
    1. The problem statement, all variables and given/known data
    Glass fibres in Nylon provide reinforcement. Young's modulus of glass fibre is 72.4GPa; Young's modulus of Nylon is 2.8GPa.
    If the Nylon contains 30% by volume glass fibres, what fraction of the force applied parallel to the fibre axis is carried by the glass fibre?

    (Assume the bonding between glass fibre and Nylon is strong enough to transfer the load, so εc = εf = εm applies)

    2. Relevant equations

    Ecl = (ff ⋅ Ef) + (fm ⋅ Em)

    Ecl = Young's modulus of composite in parallel direction
    ff = Fraction of the fibre
    Ef = Young's modulus of the fibre
    fm = Fraction of the matrix
    Em = Young's modulus of the matrix

    3. The attempt at a solution

    Given that Nylon is the matrix and the glass fibres are the fibre, the following can be assumed...

    Ecl = (0.3 ⋅ 72.4) + (0.7 ⋅ 2.8) = 41.32 MPa

    With respect to the fraction of the force applied parallel to the fibre axis, is it a matter of dividing the Young's modulus of the composite by that of the fibre?

    41.32 MPa / 72.4 MPa = 0.57 or 57%
  2. jcsd
  3. Oct 29, 2014 #2
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