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What is QUASI-ISOTROPIC laminate, and when is it used?
A{'text': 'A laminate with one isotropic ply', 'label': 'A'}
B{'text': 'A laminate stacking sequence (e.g. [0/+45/-45/90]_s or [0/60/-60]_s) that produces in-plane stiffness independent of direction', 'label': 'B'}
C{'text': 'A perfect isotropic material', 'label': 'C'}
D{'text': 'A laminate with only 0° plies', 'label': 'D'}
Answer & Solution
Correct answer: B. {'text': 'A laminate stacking sequence (e.g. [0/+45/-45/90]_s or [0/60/-60]_s) that produces in-plane stiffness independent of direction', 'label': 'B'}
Quasi-isotropic: by combining plies at multiple symmetric angles, the EXTENSIONAL stiffness A becomes isotropic in-plane (the same E_x in every direction). Note: only A is isotropic; D (bending) generally is NOT — true isotropy in bending requires more complex layups.
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