A flat composite component, in particular a vehicle body part, comprising a material composite having an outer layer, a barrier layer adjoining the outer layer and a carrier structure on which the barrier layer is arranged and which comprises a core which has a first cover layer on the side facing the barrier layer and a second cover layer on the side facing away from the barrier layer. According to the invention, the barrier layer and the carrier structure have thermal expansion coefficients which are selected such that a deformation of the material composite in the case of a temperature change at least largely stops in a range between −50° C. and +80° C.