Abstract: A method of producing a sandwich plate that consists of a foamed core layer and two fiber-reinforced cover layers, comprising the steps ofproviding a sheet of a thermoplastic plastics material, such as polyetherimide, containing an amount of a suitable solvent or blowing agent;placing said sheet between two fiber-reinforced layers of a similar thermoplastic material, such as polyetherimide; placing the core web and cover layer assembly between two pressure plates;supplying heat and pressure to the pressure plates to cause foaming of the core web andcooling the pressure plates when a predetermined foam layer thickness is obtained.According to one aspect of the invention one of the cover layers has a remaining percentage of solvent that does not exceed 0.1% of weight.According to a second aspect of the invention the thermoplastic material in at least one of the cover layers is a modification having a higher chemical resistance than the thermoplastic material of the core layer.