Which of the following are possible materials for the fiber phase in fiber-reinforced composites?

• A. Ceramics and Polymers
• B. Metals only
• C. Ceramics, Polymers, Polycrystalline, and Amorphous
• D. Hydrogels and Elastomers

Answer: (C)

The reinforcing fiber in a fiber-reinforced composite can come from a broad range of solid materials, chosen for high strength and stiffness. Ceramics offer very high stiffness and temperature resistance; polymers provide toughness and light weight; metals can also be used as fibers and are typically polycrystalline in structure. In addition, fibers can have different microstructures, being either crystalline (often polycrystalline) or amorphous. Together, this means the fiber phase can be ceramics, polymers, polycrystalline metals, or amorphous materials. Hydrogels and elastomers are generally too soft to serve as the primary reinforcing fibers in standard fiber-reinforced composites, though they may appear in specialized flexible or compliant applications.