Abstract: The invention is a method of forming a composite structure which begins with the formation of a syntactic foam core having internal communication passages that terminate with a plurality of openings in the outer surface of said core. After being wrapped with a plurality of layers of porous material, the wrapped core is positioned in a cavity of a mold having an inlet communicating with one of the openings. A source of uncured resin mix then is connected to the inlet and the mold is evacuated. After being forced through the inlet and the passages to fill the mold and impregnate said fibrous material, the resin mix is cured to provide with the core and the fibrous material a rigid composite structure.