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The "EFFECTIVE engineering properties" of a symmetric laminate (E_x, E_y, ν_xy, G_xy) are computed FROM:
A{'text': 'Per-ply properties averaged equally', 'label': 'A'}
B{'text': 'The "a" matrix (inverse of A): $E_x = 1/(h \\cdot a_{11})$, etc., where h is the total laminate thickness', 'label': 'B'}
C{'text': 'Just the 0° plies', 'label': 'C'}
D{'text': 'Random formula', 'label': 'D'}
Answer & Solution
Correct answer: B. {'text': 'The "a" matrix (inverse of A): $E_x = 1/(h \\cdot a_{11})$, etc., where h is the total laminate thickness', 'label': 'B'}
The laminate "looks like" an orthotropic plate of thickness h with effective moduli derived from the inverse-A entries. E_x = 1/(h·a_{11}), E_y = 1/(h·a_{22}), G_xy = 1/(h·a_{66}), ν_xy = −a_{12}/a_{11}. Lets the laminate enter beam/plate formulas as a single equivalent material.
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