Abstract: An integral lightning protection system and method for its use with an aircraft graphite epoxy structure. If a repair is to be made to an aircraft composite structure, the hole to be repaired is first cleared of broken composite material and replaced with a bonded adhesive patch. Over the patch and conformal to the surface of the aircraft composite structure, a dielectric layer is placed, and over the dielectric layer, at least one metal-plated graphite fiber fabric ply is placed. Where fasteners are inserted through an aircraft composite panel, the heads of the fasteners are left flush with the outer surface of the composite material, and the composite material and fastener heads are adhesively covered by a dielectric cover. Thereafter, at least one metal-plated graphite fiber fabric ply is placed over the dielectric layer. Subsequently, either structure may be given a primer and paint coating.

Abstract: A method of forming a bushing in a graphite/epoxy structure in order to repair holes that are either too large or out-of-round. A mandrel having a diameter that is smaller than the desired hole diameter is wrapped with a strip of epoxy-impregnated graphite mat until the mandrel and mat tightly fit into the hole in the graphite/epoxy structure. The mandrel is then heated causing the mandrel to both expand and cure the epoxy resin in the mat. Expansion of the mandrel forces the mat against the edge of the hole to promote bonding between the mat and the graphite/epoxy structure. After the mat has cured, the mandrel is cooled thereby causing it to contract away from the mat so that it can be easily removed. Finally, the mat is trimmed to the thickness of the graphite/epoxy structure and a hole having the desired diameter is then machined in the mat.

Abstract: A lightning protection repair system for graphite epoxy structures. An aircraft graphite epoxy structure is repaired by fastening a repair plate over the hole to be covered, followed by a dielectric sheet covering the outer surface of the metal repair plate. An electrically conducting lightning diversion sheet, conforming to the outer surface of the repair plate, is fastened to the repair plate through the dielectric sheet. The edges of the lightning diversion sheet are bent toward the outer surface of the aircraft graphite epoxy structure to be adjacent or touching its outer surface. Sealing compounds can be used around the repair plate to prevent moisture intrusion, and the repair can be faired into the aircraft graphite epoxy structure by means of a fairing compound.

Abstract: The method of sealing and bonding faying surfaces of laminated graphite reinforced epoxy plates, including the steps of mixing an uncured epoxy resin with a filler of carbon microspheres, impregnating a layer of spaced glass fibers or cloth with the mixture, positioning the impregnated fibers between the faying surfaces of overlapping plates, fastening the plates together, and curing the resin. When it is necessary to repair the seal, the fasteners are removed and the plates are separated with a wedge at the seal bondline without damaging the plate laminations.

Abstract: In a composite aircraft formed of graphite reinforced epoxy plates forming walls of the aircraft and walls of fuel tanks therein, for example, there is an adhesive seal for bonding overlapping faying plate surfaces together. The seal is formed of spaced glass fibers mixed with a conductive material and impregnated with a resin. The resin is cured between the surfaces of the plates to which it is bonded. The conductive filler is carbon in the form of approximate microspheres, generally hollow and having diameters in the range of 5 to 150 microns. The carbon microspheres function to weaken the adhesive seal between the plates so that they can be forcibly separated by a wedge without structural damage to the plates. The conductive material equalizes negative and positive static charges in the aircraft, particularly in fuel tanks, to eliminate electrical potential differences in the wall structures and in the materials therein.

Abstract: In a composite aircraft formed of graphite reinforced epoxy plates forming walls (14, 16) of the aircraft and walls of fuel tanks (12) therein, for example, there is an adhesive seal (36) for bonding overlapping faying plate surfaces together. The seal (36) is formed of spaced glass fibers (58) impregnated with a resin and with a filler of conductive material (50). The conductive filler is carbon in the form of approximate microspheres (52, 54), generally hollow, and having diameters in the range of 5 to 150 microns. The resin is cured on the faying surfaces after they have been secured together by fasteners (28) coated with a dielectric (30). The carbon microspheres (50) function to weaken the adhesive seal (36) between the plates (16, 22) so that they can be forcibly separated without structural damage to the plates.

Abstract: Method and structures for enhancing the conductivity of graphite composite materials for lightning protection and prevention of attachment of lightning to fasteners. The integral lightning protection for composite aircraft skins, including skins with fasteners penetrating into fuel tanks, utilizes metal coated or plated graphite fibers which are woven into the outer layer of tape or fabric of the structural component requiring protection.

Abstract: Method and structures for enhancing the conductivity of graphite composite materials for lightning protection and prevention of attachment of lightning to fasteners. The integral lightning protection system for composite aircraft skins, including skins with fasteners penetrating into fuel tanks, utilizes nickel-plated graphite fibers (24) which are woven into the outer layer of fabric of the structural component (10) requiring protection.