Apparatus for forming a composite tape

An extrusion die for coating a foraminous core material comprising an extrusion member having a channel extending therethrough dimensioned and configurated to substantially correspond to external dimensions of the core material to be coated to permit passage of the core material through said channel with clearance, said channel having an entry end and an exit end, a passageway provided on each side of said channel in said extrusion member which merges with and opens into said channel proximate to said exit end and a die orifice where the core material leaves said extrusion member, a section disposed on one side of and adjacent to a point of merging of said passageways with said channel at said exit end, said section providing a die lip area communicating with said die orifice on an opposite side thereof, said passageways having lengths of approximately 0.25 inches with an effective dimension across their flow path being approximately 0.05 inches, said die lip area having a length along the flow path of approximately 0.015 inches with an effective dimension across the flow path of approximately 0.02 inches, said dimensions of said passageways and of said die lip area permitting a coating of resin material under suitable extrusion pressures to encapsulate the core material during the course of passage through the extrusion die and prior to its emergence therefrom, whereby controlled application of pressure on the extruded resin material by selection of the extrusion die dimensions forces the resin material into interstices of the foraminous core material prior to emergence from the die orifice to impart a layer of resin material about the core material.