Which description best matches the general properties of common reinforcement fibers such as carbon, glass, and aramid?

Which description best matches the general properties of common reinforcement fibers such as carbon, glass, and aramid?

• A. Carbon fiber: very high stiffness and strength, low density; Glass fiber: lower stiffness, higher density than carbon, good toughness; Aramid (Kevlar): high toughness, moderate stiffness
• B. Carbon fiber: low stiffness; Glass fiber: high stiffness; Aramid: low toughness
• C. Carbon fiber: high density; Glass fiber: very high stiffness; Aramid: low strength
• D. Carbon fiber: brittle; Glass fiber: flexible; Aramid: low toughness

Answer: (A)

Stiffness, density, and toughness define how these fibers behave in composites. Carbon fiber delivers an exceptionally high stiffness (tensile modulus) and high strength for a very light weight, so it’s known for a very high stiffness-to-weight ratio and low density. Glass fiber is denser and not as stiff as carbon, but it still provides solid strength and has better resistance to impact failure than carbon, giving it relatively good overall toughness. Aramid fibers, such as Kevlar, are prized for absorbing energy and withstanding impacts, so they offer high toughness with only moderate stiffness compared with carbon or high-modulus glass. That combination—carbon with very high stiffness and low density; glass with lower stiffness and higher density plus good toughness; and aramid with high toughness and moderate stiffness—best matches the typical properties described. The other descriptions assign unlikely or inaccurate attributes to these fibers (for example, carbon as low stiffness, glass as extremely stiff, or aramid as having low toughness), which don’t align with how these reinforcements actually behave.

Stiffness, density, and toughness define how these fibers behave in composites. Carbon fiber delivers an exceptionally high stiffness (tensile modulus) and high strength for a very light weight, so it’s known for a very high stiffness-to-weight ratio and low density. Glass fiber is denser and not as stiff as carbon, but it still provides solid strength and has better resistance to impact failure than carbon, giving it relatively good overall toughness. Aramid fibers, such as Kevlar, are prized for absorbing energy and withstanding impacts, so they offer high toughness with only moderate stiffness compared with carbon or high-modulus glass.

That combination—carbon with very high stiffness and low density; glass with lower stiffness and higher density plus good toughness; and aramid with high toughness and moderate stiffness—best matches the typical properties described. The other descriptions assign unlikely or inaccurate attributes to these fibers (for example, carbon as low stiffness, glass as extremely stiff, or aramid as having low toughness), which don’t align with how these reinforcements actually behave.