Which of the following is used as a facing or core material in bonded honeycomb structures for special applications?

• A. Cardboard
• B. PVC
• C. Stainless steel
• D. Aluminum

Answer: (C)

In bonded honeycomb panels, the material chosen for the facing or core must provide the required strength, stiffness, and environmental tolerance for the application. Stainless steel is used in special applications because it offers high temperature capability and exceptional corrosion and chemical resistance, which other materials can’t reliably provide. This means the panel can maintain structural integrity in hot, harsh, or corrosive environments where lighter metals or plastics would soften, degrade, or corrode.

Cardboard would fail structurally and burn; PVC would soften or creep under heat; aluminum is lightweight and common but not always suitable for extreme environments. Stainless steel, though heavier, delivers the necessary performance when those harsh conditions demand it.