Composite sandwich structure and method of making the same

A method for forming a composite sandwich structure by compression molding, the method comprising:

• (a) providing a compression molding tool having at least a first mold portion and a second mold portion, wherein the first and second mold portions have opposing molding surfaces that cooperate to define a mold gap or mold cavity when the compression molding tool is in a closed position;
• (b) placing a stack of two composite skins separated by a non-adherent layer on the molding surface of the first or second mold portion when the tool is in an open position, wherein each composite skin comprises reinforcement fibers impregnated or infused with a curable thermoset resin and the non-adherent layer is formed of a thermally deformable material selected from silicone, rubber, hydrophobic fluoropolymers, and combinations thereof;
• (c) closing the compression molding tool to compress the stack of composite skins and non-adherent layer between the molding surfaces of the first and second mold portions while applying heat to the tool, wherein compression of the stack is carried out until each composite skin conforms to and adhere to the molding surface adjacent to it but the thermoset resin in said composite skin is not fully cured;
• (d) opening the compression molding tool, wherein each composite skin remains adhered to the adjacent molding surface;
• (e) removing the non-adherent layer from the compression molding tool;
• (f) placing a core layer in the compression molding tool while the tool is in the open position such that the core layer is on one of the composite skins adhered to the molding surfaces;
• (g) closing the compression molding tool to compress the core layer between the first and second mold portions while applying heat to the tool, wherein compression of the core layer is carried out until the core layer is bonded to the composite skins and the thermoset resin in each composite skin is fully cured, thereby forming a shaped sandwich structure;
• (h) opening the compression molding tool;
• and
• (i) removing the shaped sandwich structure from the compression molding tool.