Abstract: The invention relates to a contoured structural element (100) for use as a core layer in a curved sandwich composite element, the contoured structural element (100) being formed from a thermoplastic foam, in particular PET, the contoured structural element (100) being subdivided, except for a connecting layer (12), into a plurality of body elements (10), and the body elements (10) and the connecting layer (12) being aligned parallel to a base area (26) of the contoured structural element (100) which is in a planar state. According to the invention, at least one surface layer (16) of the connecting layer (12) and the adjoining surface layer (18) of the body elements (10) at least partly have a thermally densified layer (14); the body elements (10), the connecting layer (12) and the thermally densified layer (14) being made of the same material.