The use of a fibre composite material W having a sandwich structure, constructed from: A) a thermoplastic material layer w, containing as components: a) a thermoplastic moulding compound A as a matrix, b) a ply made from reinforcing fibres B, and c) optionally additive C, wherein the ply of reinforcing fibres B is embedded in the matrix of the thermoplastic moulding compound A, and, in the production of the material layer w, the thermoplastic moulding compound A comprises at least one chemically reactive functionality, which reacts with chemical groups of the surface of the reinforcing fibres B; and B) a further thermoplastic layer T and/or a foam layer S, wherein said further layer T and/or S is permanently connected to the material layer w; provides increased mechanical stability for the production of moulded parts.