United Technologies Corporation

Sikorsky Aircraft Corporation

Geoffrey C Davis

Allen J McIntire

Gary J Jacaruso

Alex C Dublinski

Joseph Goldberg

David A Evans

Michael A Kornitzky

William Sharp, Jr

Sharp, Jr, William

A method and apparatus for controlling the thickness of press-cured composite articles during the manufacture thereof. The method includes a preparatory or prefabrication stage wherein prepreg plies are layed up and compacted to form a plurality of laminates that define a final laminate package that defines the uncured configuration of the composite article. The final laminate package may include supplemental ply-packs layed up at the mid-plane or neutral axis of the final laminate package for the purpose of controlling the overall thickness of the final laminate package. The prepreg plies layed up in the preparatory stage have been precut to conform to the final net shape of the composite article, but include a predetermined overbuild in the width dimension to facilitate control of thickness during cure of the final laminate package. The method further includes a fabrication stage wherein a deformable, back-pressure system is abutted in combination with the final laminate package, which is then subjected to a cure cycle to form the press-cured composite article. The deformable, back-pressure system is controllably deformed during the cure cycle to control and limit the lateral expansion of the final laminate package. The deformable, back-pressure system also prevents fiber washout during the cure cycle.

Apparatus for controlling thickness during lay-up and fabrication of

Method for controlling thickness during lay-up and fabrication of

A heating element for providing localized heating during the thermoplastic bonding of thermoset composite structures is disclosed. Various construction details are developed which disclose an apparatus and method for uniformly heating a bond line. In one embodiment, a heating element (22) includes a resistance heating material (24) sandwiched between two layers of electrical insulation (25) and encased within a layer of thermoplastic material (26). Low resistance electrical leads (28), which extend across the width of the resistance heating material, and a power supply (30) provide electrical energy to raise the temperature of the resistance heating material.

Heating means for thermoplastic bonding

A method of bonding metallic structures to thermoplastic composite structures is described. Various construction details have been developed which provide a method for producing a bond of sufficient strength to transmit rotational and axial loads between the metallic and thermoplastic composite structures. In one embodiment, the method includes the steps of knurling a mating surface of the metallic structure, coating the mating surface with a thermoplastic material to produce a bonding surface, and consolidating the bonding surface to the thermoplastic composite structure.

Bonding of thermoplastic composite structures to metal structures

A method to bond metallic structures to thermoset composite structures is described. Various construction details have been developed which provide a method for producing a bond of sufficient strength to transmit torsional and axial loads between the metallic and thermoset composite structures. In one embodiment, the method includes steps to form a bonding surface on a metallic structure by knurling a mating surface of the metallic structure and molding a thermoplastic material over the knurled surface. Further, the method includes steps to form a bonding surface on a thermoset composite structure by partially embedding a layer of dry fiber into a thermoplastic cone, coating the exposed dry fiber with thermoset resin, and curing the coated dry fibers into the thermoset composite structure. The final step is to fuse the two bonding surfaces by applying heat sufficient to melt the thermoplastic material.

Bonding of thermoset composite structures to metal structures

A pair of thermoset composite structures (19,19') are bonded together by a pair of adhesive strips (10,10'). An adhesive strip (10) is comprised of a layer of semi-crystalline thermoplastic material (12), a layer of amorphous thermoplastic material (14), a layer of dry fiber reinforcement (16) partially embedded in the layer of amorphous thermoplastic material (14), and a layer of thermosetting resin (18) covering the exposed fibers of the dry fiber reinforcement. An adhesive strip is bonded to the bonding surface (20) of the structure (19) during the curing process for the thermoset composite structure. A resistance heating element is placed between the bonding surfaces (20,20'), the bonding surfaces (20,20') are pressed together, and electrical energy is passed through the heating element (24) to heat the joint and fuse the thermoplastic adhesive layers together. The dry fiber reinforcement (16) forms a mechanical lock between the cumulative layer of thermoplastic adhesive (32) and the thermosetting structures (19,19') to provide the bond strength.

Bonding of thermoset composite structures

Method of making thermoplastic adhesive strip for bonding thermoset

A method of making a flexible composite tool particularly adapted for composite molding and the composite tool made by this method. The method includes dissolving a B-staged fluoroelastomer in a suitable solvent such as methyl ethyl ketone or toluene to form a fluoroelastomer solution. A fabric is then coated with the fluoroelastomer solution. The solvent is evaporated and the impregnated fabric is sandwiched between unreinforced sheets to form a reinforced tooling material. The reinforced tooling material is laid up with alternating layers of unreinforced fluoroelastomer and then cured to form a composite tool which is stable through multiple thermal cycles. In addition, an elastomer tool can be provided with detail cavities shaped to accept separately formed detail structures, with each cavity including extra reinforcement in order to locate the details to close tolerances without extensive hand positioning or use of adhesives. The tool is useful in molding composites and is reusable. The life of the tool is further prolonged by a described method of repairing damaged portions of the tool.

Method for forming complex composite articles

The method of manufacturing a multi-legged (preferably five) flexbeam for a hingeless flexbeam helicopter rotor, which flexbeam is of one-piece construction and made solely of composite materials, and includes full length plies of unidirectional high strength fibers extending from a first leg and splitting in passing through the hub portion of the flexbeam, and then extending into two substantially diametrically opposite legs, and having cross and unidirectional plies interspersed between the full length plies to effect the desired taper and shape of the flexbeam hub and legs, and wherein the final ply lay-up is made on a rotatable lay-up tool of dodecahedron shape.

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Madison, CT, United States of America

Geoffrey C Davis