Boron fibers were historically used in aerospace but have largely been…

Question

Boron fibers were historically used in aerospace but have largely been displaced by carbon fibers. The main reason is:

Accepted Answer

D. {'text': 'Carbon fibers offer comparable specific stiffness at substantially LOWER COST and easier handling (boron is brittle, heavy filament)', 'label': 'B'}

Boron fibers (CVD-grown on tungsten core) are stiff but expensive, very brittle, and require specialty handling. Carbon fibers achieved comparable performance via continuous PAN-fiber processing at far lower cost. Modern composites overwhelmingly use carbon.

Answer

{'text': 'Boron is toxic', 'label': 'C'}

Answer

{'text': 'Boron melts', 'label': 'D'}

Answer

{'text': 'Boron is weaker', 'label': 'A'}