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How many INDEPENDENT elastic constants describe an ORTHOTROPIC material (three mutually perpendicular planes of symmetry)?
A{'text': "9 — three Young's moduli (E_1, E_2, E_3), three Poisson's ratios (ν_12, ν_13, ν_23), three shear moduli (G_12, G_13, G_23)", 'label': 'C'}
B{'text': '3', 'label': 'B'}
C{'text': '2', 'label': 'A'}
D{'text': '21', 'label': 'D'}
Answer & Solution
Correct answer: A. {'text': "9 — three Young's moduli (E_1, E_2, E_3), three Poisson's ratios (ν_12, ν_13, ν_23), three shear moduli (G_12, G_13, G_23)", 'label': 'C'}
Orthotropic = three orthogonal planes of material symmetry (e.g., wood, single-ply unidirectional composite). The stiffness matrix has 9 independent entries: 3 Young's moduli, 3 Poisson's ratios, 3 shear moduli.
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