Multilayer sheet depends on adhesion between polymers that may not bond directly. A tie layer can fail during heating, deep drawing, cooling, trimming, bonding, or service. The defect may appear as bubbles, edge lifting, whitening, or broad separation between layers.
The first location and process stage should be recorded. Delamination confined to highly stretched corners suggests strain and thickness distribution; separation across flat sheet points toward incoming bond quality, moisture, or thermal exposure. Peel testing of unformed and formed samples helps separate sheet manufacture from forming damage.
The layer structure, tie-layer chemistry, thickness, conditioning, and approved forming window must be confirmed with the sheet supplier. More heat may improve flow while weakening an already marginal interface. Tool radii, pre-stretch, trimming method, and downstream chemicals should be evaluated as part of the complete laminate system.