Composite strength testing, simple question – almost!?

A continuous and aligned fibre-reinforced composite is to be produced consisting of 45% vol aramid fibres and 55% vol polycarbonate. What would the stiffness be in GPa (2 d.p.), if the same volume of fibres were used, however they were in the form of a chopped strand mat?

The mechanical properties of the two materials are given as follows:
Aramid fibre: E (GPa) 131 UTS (MPa) 3600
Polycarbonate: E (GPa)2.4 UTS (MPa)80

I went a head and did the question, with the formula:
Ec(longitudinal) = (K x Ef x Vf) + (Em x Vm)
And subing for:
Ec(longitudinal) = Unknown
K = 1 (aligned/continuous/parallel in plane)
Em = 2.4 GPa (polycarbonate = matrix phase)
Ef = 131 GPa (aramid fibre = fibre phase)
Vm = 55% = 0.55
Vf = 45% = 0.45

To get an answer of: 60.27 GPa

But then i realised it said "however they were in the form of a chopped strand mat" does that mean the K value is not 1???

If someone could point me in the right direction for this chopped mat that would be great!!!

That looks right to me

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One Response to Composite strength testing, simple question – almost!?

  1. The Expert of Experts says:

    That looks right to me
    References :
    math expert of experts