Delamination

Separation of layers in a composite or coated material along an internal interface, producing a loss of through-thickness mechanical continuity and integrity.

Separation between adjacent plies or layers within a laminated composite or bonded multi‑layer structure caused by interlaminar stress, out‑of‑plane loading, impact, manufacturing defects, or fatigue; delamination propagates when the energy release rate at the interply interface exceeds the interlaminar fracture toughness (G_IC, G_IIC) and is distinct from matrix cracking and fiber breakage.