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Where:<br />

Ar = weight of one sheet of reinforcement / unit area, g/m 2<br />

N = number of sheets in the test specimen.<br />

For the Reinforcement Content, Volume Percent;<br />

Vr = (Ar x N x 0.1)( ρc x h) (Equation 3.15)<br />

For the Matrix Content, Weight Percent;<br />

Wm = 100 - (Ar x N x 0.1)/ (ρc x h) (Equation 3.16)<br />

<strong>an</strong>d<br />

For the Matrix Content, Volume Percent;<br />

Vm = Wm x ρc/ ρm (Equation 3.17)<br />

The earlier five elastic const<strong>an</strong>ts equations (i.e. Equations 3.7 till 3.11) are<br />

required in the study of the macro-mech<strong>an</strong>ics of lamina, whereby the material is<br />

presumed to be homogeneous <strong>an</strong>d the effects of the constituent materials are detected<br />

only as averaged apparent properties of the composite (McGraw-Hill, 2003).<br />

In other words, given the material properties of the fibres, <strong>an</strong>d the matrix <strong>an</strong>d<br />

volume fraction of fibres, those equations will estimate the equivalent material<br />

properties of the composite lamina in the principal directions (Efunda, 2011).<br />

There are a few assumptions in the macro-mech<strong>an</strong>ics of laminated composites:<br />

The matrix is homogeneous, isotropic, <strong>an</strong>d linearly elastic.<br />

The fibre is homogeneous, isotropic, linearly elastic, continuous, regularly spaced,<br />

<strong>an</strong>d perfectly aligned.<br />

The lamina (single layer) is macroscopically homogeneous, macroscopically<br />

orthotropic, linearly elastic, initially stress-free, void-free, <strong>an</strong>d perfectly bonded.<br />

95

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