Abstract: A method of making a composite structure, such as an aircraft wing, which has a foam core and at least one outer layer of fiber reinforced resin material. A shaped foam core is prepared by compressing a rigid, closed-cell foam to the desired shape in a closed mold under heat and pressure. A sheet of flexible open-cell foam is impregnated with a thermosetting resin. A sheet of dry fiber reinforcement material is placed on one or both sides of the impregnated foam sheet. The resulting sandwich is wrapped around the foam core and the assembly is placed in a corresponding tool cavity. The tool is heated to the curing temperature of the impregnating resin. As the temperature rises, the foam core expands, exerting pressure on the impregnated foam sheet, forcing resin into the fiber reinforcement, wetting all the fibers and forcing air out of the material. As the resin cures, void-free, strong skins are formed integral with the core foam.