Which material property of composites makes them attractive for aircraft structures?

• A. Low density
• B. High thermal conductivity
• C. Poor fatigue resistance
• D. High strength-to-weight ratio and corrosion resistance

Answer: (D)

The standout idea is a combination of how much load a material can carry for its weight and its resistance to environmental degradation. In aircraft structures, you want parts that are very strong without being heavy, so the strength-to-weight ratio is a major driver of performance and efficiency. Composites excel here because they can be engineered to be very stiff and strong while keeping mass low, which improves fuel efficiency, range, and payload capability.

Corrosion resistance adds another big advantage. In service, aircraft face moisture, salts, de-icing fluids, and other chemicals that can corrode metals. Many composites resist these effects, so they maintain their integrity longer and require less maintenance compared with metals. This combination—high strength-to-weight and good corrosion resistance—drives the attractiveness of composites for critical structures.

Low density is helpful, but by itself it doesn’t capture the full benefit. High thermal conductivity isn’t typical of most composites, which often have lower thermal conductivity than metals and isn’t the primary reason for their use. Saying they have poor fatigue resistance isn’t accurate for properly designed composites, as they can offer excellent fatigue performance when the layup and materials are chosen for the application.