A method, apparatus, system, and computer program product for fabricating a composite part. Composite materials are laid up on a mandrel. A caul is placed over the composite materials laid up on the mandrel. An inner mold line of the caul is sized to an outer surface of the composite materials in a cured state. The composite materials laid up on the mandrel with the caul over the composite materials is cured to form the composite part. The composite materials expand to the inner mold line of the caul during curing of the composite materials to form the composite part.