Which material typically offers a higher stiffness-to-weight ratio, CFRP or GFRP, albeit at a higher cost?

Which material typically offers a higher stiffness-to-weight ratio, CFRP or GFRP, albeit at a higher cost?

• A. GFRP has higher stiffness-to-weight ratio than CFRP
• B. CFRP has equal stiffness-to-weight ratio as GFRP
• C. CFRP typically offers higher stiffness and strength per unit weight than GFRP, but at higher cost
• D. Costs are lower for CFRP than GFRP

Answer: (C)

Stiffness per unit weight, or specific stiffness, is about how much an material resists bending or deformation for a given mass. Carbon fiber has a much higher modulus than glass fiber and usually a lower density, so when you make a carbon fiber reinforced polymer, the composite tends to be much stiffer per kilogram than a glass fiber reinforced polymer. That means you get more stiffness and often higher strength for each kilogram of material, which is why CFRP is favored for lightweight, high-stiffness applications. The trade-off is cost: carbon fibers and the associated processing are more expensive, so CFRP generally costs more than GFRP for the same performance. So the choice that CFRP typically offers higher stiffness and strength per unit weight than GFRP, but at a higher cost, best captures the comparison.

Stiffness per unit weight, or specific stiffness, is about how much an material resists bending or deformation for a given mass. Carbon fiber has a much higher modulus than glass fiber and usually a lower density, so when you make a carbon fiber reinforced polymer, the composite tends to be much stiffer per kilogram than a glass fiber reinforced polymer. That means you get more stiffness and often higher strength for each kilogram of material, which is why CFRP is favored for lightweight, high-stiffness applications. The trade-off is cost: carbon fibers and the associated processing are more expensive, so CFRP generally costs more than GFRP for the same performance. So the choice that CFRP typically offers higher stiffness and strength per unit weight than GFRP, but at a higher cost, best captures the comparison.