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Why are most aerospace primary-structure composites laminates ALWAYS made SYMMETRIC (B = 0) even if some asymmetric layup might save weight?
A{'text': 'Cosmetic', 'label': 'A'}
B{'text': 'To avoid CURE-INDUCED WARPAGE — the thermally-driven coupling via B causes the laminate to spring out of shape on cooldown, ruining fit-up and adding cost', 'label': 'B'}
C{'text': 'Symmetric is always cheaper', 'label': 'C'}
D{'text': 'Asymmetric layups are illegal', 'label': 'D'}
Answer & Solution
Correct answer: B. {'text': 'To avoid CURE-INDUCED WARPAGE — the thermally-driven coupling via B causes the laminate to spring out of shape on cooldown, ruining fit-up and adding cost', 'label': 'B'}
Composites are cured at high temperature; cooling to room temperature creates thermal strains. Any B ≠ 0 converts this into out-of-plane warpage that cannot be easily corrected. Loss of dimensional control kills assembly fit-up. Hence the universal "symmetric layup" design rule.
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