The breakdown of a material by separation of the layers composing it is called delamination. It occurs when bonded layers fracture or lose adhesion, causing a material to split into sheets or plies.
Delamination is especially common in laminated composites, such as carbon-fiber or fiberglass panels. These materials combine strong reinforcement fibers with a polymer matrix, often epoxy. Forces running across the layers, repeated impacts, moisture, heat, or manufacturing flaws can weaken the bond between them. The damage may begin invisibly inside the material before appearing as bubbling, cracking, or peeling.
The term also applies to coatings, paints, concrete, rolled metals, and some 3D-printed objects. A common mix-up is confusing delamination with ordinary surface cracking: delamination specifically involves separation between layers or between a coating and its underlying surface. In engineering, detecting it early matters because a seemingly small internal separation can reduce strength dramatically.