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In a Polymer Matrix Composite (PMC), the matrix can be EITHER thermoplastic OR thermoset. The KEY difference is:
A{'text': 'Thermoplastics can be re-melted and re-shaped after curing; thermosets cross-link irreversibly upon curing and cannot be re-melted', 'label': 'B'}
B{'text': 'Thermoset matrices are reversibly re-meltable; thermoplastics are not', 'label': 'A'}
C{'text': 'Thermoplastics are only for short fibers', 'label': 'D'}
D{'text': 'Thermosets are weaker', 'label': 'C'}
Answer & Solution
Correct answer: A. {'text': 'Thermoplastics can be re-melted and re-shaped after curing; thermosets cross-link irreversibly upon curing and cannot be re-melted', 'label': 'B'}
Thermoplastics (PEEK, nylon, polypropylene): linear/branched chains, can be melted and recycled. Thermosets (epoxy, polyester): irreversible cross-linking on cure — strong, dimensionally stable, but cannot be reshaped. Most aerospace CFRP uses thermoset epoxy.
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