an improved lightweight , flame resistant composite panel is disclosed which is readily shaped at room temperature without the necessity of machining . the composite panel comprises a foamed rigid thermoplastic core sandwiched between a pair of metallic layers . the thermoplastic core contains inorganic fillers in powder form to add further flame resistant characteristics to the composite panel . the metallic layers are bonded to the core by means of a thin layer of adhesive which exhibits good strength at elevated temperatures .