Which of the following is NOT listed as a common cause of delamination?

• A. Thermal cycling
• B. Sonic vibration
• C. Expansion of internal moisture
• D. Liquid leakage

Answer: (A)

Delamination happens when the bond between laminate layers fails under stress at the ply interfaces. The usual culprits you’ll encounter are moisture-related effects, chemical attack from fluids, and cyclic mechanical loading. Expansion of internal moisture causes the layers to swell differently, creating interlaminar shear that can push the plies apart. Liquid leakage can degrade the resin or adhesive at the bond line, weakening the grip between layers and allowing separation under load. Sonic vibration introduces repeated, fatigue-causing stresses at the interfaces, gradually growing any existing delaminations. Thermal cycling, while it can affect materials in some situations, isn’t listed as a common cause in this context, so it’s the one that doesn’t fit with the other typical contributors.