Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/08—Anti-corrosive paints
  • C09D5/082—Anti-corrosive paints characterised by the anti-corrosive pigment
  • C09D5/084—Inorganic compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/08—Anti-corrosive paints
  • C09D5/10—Anti-corrosive paints containing metal dust
  • C09D5/103—Anti-corrosive paints containing metal dust containing Al
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
  • F16B19/00—Bolts without screw-thread; Pins, including deformable elements; Rivets
  • F16B19/04—Rivets; Spigots or the like fastened by riveting
  • F16B19/06—Solid rivets made in one piece
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
  • F16B2200/00—Constructional details of connections not covered for in other groups of this subclass
  • F16B2200/97—Constructional details of connections not covered for in other groups of this subclass having differing thermal expansion coefficients

Definitions

• the invention relates to the pre-coating of composite components.
• the invention relates to a composite component, coated with a cured organic coating, and a method of applying the coating to the composite component.
• the invention relates to a composite fastener, coated with a cured organic resin.
• High-strength composite materials are gaining acceptance in manufacturing due to improving physical properties and economic availability. Along with increased use, the composite materials are more commonly used in conjunction with metallic components in situations that require structural integrity and fatigue resistance.
• the use of composite materials in aerospace applications has been limited to secondary aircraft components and parts, which have provided for significant weight savings while possessing exceptional durability and maintainability.
• a major area of concern continues to be the mechanical joining of high-strength composite components using high-strength aerospace fasteners.
• high-strength fasteners are typically metallic or formed from particular high-strength composite resins (often polyetheretherketone, "PEEKTM” aromatic polymers) different from the main composite material (typically a carbon/epoxy or polyaramid/epoxy or glass/epoxy composite), they do not often have similar or compatible physical characteristics as those main composite materials.
• PEEKTM polyetheretherketone
• the dissimilarity of the metallic fasteners and the composite materials joined in the assembly stackup materials is still problematic, particularly concerning delamination, electrical continuity, galvanic corrosion, and differential expansion of the materials. It is desired to provide an improved composite component for use with composite structural components in a wide variety of applications, both aerospace and otherwise. More particularly, it is desired to provide a composite fastener for use in the joining and assembly of composite and composite/metallic stackups that avoids the problems of delamination, electrical continuity, galvanic corrosion, and differential expansion associated with metallic fasteners, but avoids the problems of incompatibility associated with composite fasteners of the past.
• the present invention provides a pre-coated composite component and method of pre- coating a composite component with an organic coating that improves the component's compatibility with other dissimilar composite and metallic materials.
• improved compatibility it is meant that the composite structures assembled with the coated component generally exhibit reduced issues relating to composite delamination, water intrusion, electrical continuity of the composite, arcing between components, galvanic corrosion, fuel-tightness, and differential expansion of the components in the structure.
• the precursor component is a composite, i.e., fiber-reinforced material within a polymeric resin matrix, and the surface of the component is pre-coated with an organic resin that is cured after being applied to the surface of the component.
• the fiber-reinforced material of the component precursor is typically selected from carbon fibers, polyaramid fibers, and glass fibers, and the matrix material of the component precursor is preferably a high-strength thermoplastic aromatic resin, such as a polyetheretherketone (PEEKTM), but may also be a thermosetting resin.
• the curable organic coating material is provided advantageously comprising a polyaromatic- based resin mixed with at least one plasticizer and an organic additive selected from a group consisting of aluminum powder and a chromate-containing filler, preferably strontium chromate, with the coating material having a non- volatile portion.
• Preferred polyaromatic-resins include, but are not limited to, phenolics, polyamides, polyimides, polybenozazoles, and polytetrafluoroethylenes.
• the pre-coated component may be used with composite structures in any application, in forms such as brackets, fittings, etc., wherein intimate physical contact between the structure and the component would otherwise be deleterious to the assembled structure due to the difference in material properties between the adjacent, surrounding structure and the pre-coated component.
• the pre-coated component may advantageously be used as a fastener, such as a rivet or bolt, when assembling and joining composite and composite/metallic structures.
• the pre-coated components When used in the assembly of composite structures, the pre-coated components provide joints with optimized strength, improved durability, and enhanced corrosion resistance compared to joints and assemblies made with uncoated fasteners of the past.
• the pre-coated components may be used directly in the assembly of composite materials without the additional and costly protective steps needed with metallic or uncoated components, e.g., use of certain, more expensive metallic materials and fatigue compromising clearance- fit and wet- installed fastener installations.
• resulting joint strength and integrity are improved by improving the compatibility of the fasteners with the joined, assembled materials.
• FIG. 1 is a flowchart demonstrating the coating or pre-coating of a composite component in accordance with an embodiment of the invention
• FIG. 2 is a figure that illustrates a pre-coated standard protruding-head rivet and installation of the pre-coated rivet into two structures to be joined together in accordance with an embodiment of the invention
• FIG. 3 is a figure that illustrates a pre-coated slug-type rivet that has been inserted into a structure without yet being upset to join two structures in accordance with an embodiment of the invention
• FIG. 4 is a figure that illustrates a pre-coated flush-head rivet and installation of the pre- coated blind rivet into two structures to be joined together in accordance with another embodiment of the invention
• FIG. 5 is a figure that illustrates the pre-coated flush-head rivet of FIG. 4 that has been upset and use of the upset pre-coated rivet to join two structures in accordance with another embodiment of the invention.
• thermoplastic and thermoset polymeric resins can act as the matrix for a wide range of particle and fiber additives.
• exemplary thermosetting resins include but are not limited to allyl polymers, alkyd polyesters, bismaleimides (BMI), epoxies, phenolic resins, polyesters, polyurethanes (PUR), and polyurea-formaldehydes. Epoxies and thermoset polyesters are currently the favored thermoset resins.
• Thermoplastics useful in the formation of composites include but are not limited to liquid-crystal polymers (LCP); fluoroplastics, including polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy resin (PFA), and polychlorotrifluoroethylene (PCTFE), and polytetrafluoroethylene-perfluoromethylvinylether (MFATM); ketone-based resins, including polyetheretherketone (PEEKTM); polyamides (for example nylon-6/6, 30% glass fiber); polyethersulfones (PES); polyamideimides (PAIS), polyethylenes (PE); polyester thermoplastics, including polybutylene terephthalate (PBT), polyethylene terephthalate (PET), and poly henylene terephthalates); polysulfones (PSU); poly(phenylene sulfides) (PPS).
• LCP liquid-crystal polymers
• Polyetheretherketone fluoropolymer is available as PEEKTM polymer from Victrex Pic, Greenville, SC.
• PEEKTM polymer is easy to process and has good chemical resistance, abrasion resistance, high-temperature resistance, hydrolysis resistance, flame resistance with low smoke and toxic gases, excellent electrical properties, and excellent resistance to gamma rays.
• PEEKTM polymer may be mixed with other resins or fillers, such as glass or carbon, through known methods, such as via melt compounding.
• the polymer matrix of the composite can be reinforced with a wide variety of fiber materials, e.g., glass, metal, minerals, and both conductive and non-conductive graphite fibers, to meet a diverse range of mechanical, physical, chemical, thermal, and electrical requirements. While certain fiber additives provide additional strength, others address electromagnetic and radio frequency shielding. Additives can also be used to increase flame retardency, to improve lubricity or, in the case of pigments, simply to change the color of the final product. Depending on the polymer of the matrix, different amounts of fiber reinforcement provide improved stress cracking, cut-through resistance, dimensional stability, creep, warpage, heat deflection, tensile strength, and flex modulus.
• fiber materials e.g., glass, metal, minerals, and both conductive and non-conductive graphite fibers
• a coating material is provided, preferably in solution so that it may be readily and evenly applied.
• the usual function of the coating material is to protect the base material, to which it is applied from corrosion, including, for example, conventional electrolytic corrosion, galvanic corrosion, and stress corrosion.
• the coating material is a formulation that is primarily of an organic composition, but which may contain additives to improve the properties of the final coating.
• the coating is initially dissolved in a carrier liquid so that it can be applied to a substrate.
• the coating material is applied to the untreated fastener in coating step 24.
• Any suitable coating approach such as dipping, spraying, brushing, or a fluidized bed method can be used.
• the solution of coating material dissolved in solvent is sprayed onto the rivet precursor.
• the majority of solvent in the coating may be removed from the as-applied coating by drying or "flash cure" 25, either at room temperature or slightly elevated temperature, so that the coated article is dry to the touch.
• Flash cure or drying may be achieved at about 200°F for about 1 to 2 minutes and accomplishes evaporation of the majority of solvent allowing the coated article to be handled without altering or damaging the coating layer.
• the coated component may still not be suitable for service after drying or flash cure, because the coating may not have sufficiently cured and adhered to the surface of the composite component and because the coating itself is not sufficiently coherent to resist corrosion or mechanical damage in installation or subsequent service.
• the coating material should eventually be subjected to a formal curing protocol to effect structural changes within the organic component, typically cross-linking of the organic molecules to improve the adhesion and cohesion of the coating.
• the coating is heated to and maintained above the curing temperature of the coating material.
• cure time will vary with the coating material used and the associated cure temperature selected. Typical cure temperatures range from about 250°F to about 425°F, and typical cure times range from about 1 hour to about 4 hours, not respective, and more typically from about 375°F to about 425°F for about 1 to about 1.5 hours, not respective. It is understood that the term “pre-coated” or “pre-coating” refers to the coating process of the fastener prior to installation and assembly in its final use. After curing, the coated component may be installed 28 in a composite or composite/metallic structure in the manner appropriate to its type and use. The installation step 28 reflects one of the advantages of the present invention.
• the precursor or composite component of the invention may advantageously be a fastener, such as a rivet, threaded pin, lockbolt, bolt, screw, etc., which may have threads or concentric grooves, and have female mating components such as nuts, collars, lock washers, etc., or other article manufactured to any conventional shape and size.
• a fastener such as a rivet, threaded pin, lockbolt, bolt, screw, etc., which may have threads or concentric grooves, and have female mating components such as nuts, collars, lock washers, etc., or other article manufactured to any conventional shape and size.
• One advantageous embodiment of the invention relates to the preparation of composite fasteners such as solid rivets and the use of the composite fasteners to fasten or join composite or composite-metallic components or structural stackup materials to one another.
• the use of the invention is not limited to rivets, or even fasteners, and, instead, is more broadly applicable.
• its use in composite fasteners, and preferably solid composite rivets offers particular advantages that will be discussed. While the following discussion emphasizes composite fasteners, the invention is broadly applicable to a vast array of composite components or precursors.
• the methods and techniques discussed herein may be used to produce a wide range of pre-coated composite components other than fasteners.
• High-strength composite fasteners are currently available in a limited variety of shapes and configurations.
• composite fasteners are available from Tiodize Co, Inc. of Huntington Beach, CA. Further, composite fasteners may be found in U.S. Pat. No.
• FIG. 1 illustrates a solid composite rivet, wherein the rod of the fastener is formed of a woven composite material.
• U.S. Pat. No. 4,861,211 discloses a composite rivet comprising a tubular or cylindrical preform composed of a composite material.
• U.S. Pat. No. 4,717,302 discloses a bolt and nut formed from a block or rod of resin-impregnated fibers woven in first, second and third planes, each perpendicular to the other.
• Figures 2-5 illustrate three exemplary embodiments of pre-coated rivets with three types of rivets 40, each with a coating 48 at an intermediate state of their installation to join a first piece 42 to a second piece 44 after installation to the first and second pieces but before being upset.
• the rivet 40 of Figure 2 has a pre-manufactured protruding head 46 on one end and a cylindrical shank at the opposite end.
• the rivet 40 of Figure 3 is a slug rivet having uniform cylindrical shank.
• the rivet 40 of Figure 4 has a pre-manufactured flush head 46 on one end that resides in a countersink of similar configuration in the piece 42.
• Figure 5 shows a flush head rivet following installation in the two joined workpieces 42, 44 and with the cylindrical shank end having been permanently upset 40.
• the present invention may be used with these and other types of fasteners.
• the surface of the fastener that will come into contact with the composite components or structures being fastened or joined is pre-coated with a coating.
• the surfaces of the fastener that may come into contact with the composite structure or composite/metallic stackup when installed are referred to as the "outer surfaces" of the fastener. What is or is not an outer surface will vary according to the type of fastener and the manner in which the fastener is installed. For instance, the outer surfaces of solid rivets typically contact the structures being joined. Because the body of the standard solid rivet, including portions of the head 46 and tail 40, contact the joined structure 42, 44, the surface of the solid rivet is considered the outer surface of the fastener and is advantageously completely pre-coated 48. A number of curable, organic coating materials are available and operable in the present process.
• the coating material may be any of a wide variety of curable organic coating materials having aromatic resins, such as phenolics, polyamides, polybenoxazoles, etc.
• the resin or resins are preferably mixed with one or more plasticizers, other organic components such as polytetrafluoroethylene, and inorganic additives such as aluminum powder and/or strontium chromate or other corrosion-inhibiting additives.
• These coating compounds are preferably dissolved in a suitable solvent present in an amount to produce a desired application consistency.
• the solvent is advantageously a mixture of ethanol, toluene, and methyl ethyl ketone (MEK).
• a typical sprayable coating solution preferably has about 30% by weight ethanol, about 7% by weight toluene, about 45% by weight methyl ethyl ketone (MEK) as the solvent; and about 2% by weight strontium chromate, about 2% by weight aluminum powder, with the balance being mixed with phenolic resin and at least one plasticizer.
• MEK methyl ethyl ketone
• strontium chromate about 2% by weight aluminum powder, with the balance being mixed with phenolic resin and at least one plasticizer.
• a small amount of polytetrafluoroethylene may optionally be added.
• Hi-Kote 1TM from Hi-Shear Corp., Torrance, Calif. This product has a standard elevated temperature curing treatment of 1 hour at 400°F +/-25°F as recommended by the manufacturer.
• the Hi-Kote 1 coating and other similar coatings are described in commonly assigned U.S.
• the coating material is preferably provided in solution so as to be evenly applied.
• the coating material preferably is a formulation that is primarily of an organic nature, but may also contain additives to improve the properties of the final coating.
• a TeflonTM compound may be added to improve lubricity and to allow for better hole fill and sheet take-up.
• aluminum powder pigment may be added to improve coating material integrity.
• the coating is desirably dissolved initially in a carrier liquid to facilitate various methods of deposition on a substrate.
• the coating material is curable to effect structural changes within the organic coating material, typically cross-linking of organic molecules to improve the adhesion and cohesion of the coating material to the applied substrate.
• a flash cure temperature of 200°F for 1 to 2 minutes or full cure temperature of 400°F for approximately 1 hour are exemplary.
• the majority of the solvent portion of the coating is removed by a "flash-cure" drying process at a slightly elevated temperature of +200°F for 1 to 2 minutes. Flash curing volatizes the volatile portion of the coating solvent and allows handling of the coated fastener prior to full curing.
• the outer surface of the composite fastener is soap cleaned and dried (i.e., degreased) prior to application of the coating. Degreasing cleans the composite surface of oils or other contaminants that may be present upon the outer surface of the fastener. Degreasing increases the mechanical bonding of the coating to the fastener.
• the coatings of the present invention are internally coherent and are uniformly deposited at a preferred thickness of from about 0.0003 to about 0.0005 inch, though the coating may have other thicknesses if desired. Surprisingly, it has been demonstrated through testing that the coating deposited onto a rivet-type fastener, and subsequently cured, is able to withstand the installation forces placed upon the pre-coated rivet during upset. For example, the pre-coated fastener components of one embodiment of the present invention meet required ultimate double shear strength requirements useful in aircraft primary structural applications.
• the fasteners of this embodiment must meet the ultimate shear strength requirements for uncoated rivets of a minimum of 34,500 lbs./in while exhibiting no perceptible impact on the coating integrity even if the protruding shanks of the rivets are expanded during installation to a diameter of about 1.6 times their initial diameters.
• the ultimate shear strength values ranged from 34,900 lbs./in to 40,400 lbs./in with an average of 37,400 lbs./in . No evidence of spalling or other unsatisfactory conditions regarding the coating adherence was evident upon inspection of the rivet upsets after installations.
• the pre-coated composite components may be installed or assembled with composite structures, including composite/metallic stackups, according to installation methods previously used in the art.
• sealing with wet polysulfide sealants in those situations that previously required the use of sealants is no longer required due to the beneficial aspects achieved by the pre-coating of the components.
• the coating is sufficiently durable to survive the impact of upsetting a solid rivet or the torque applied when installing a threaded fastener.
• the installation step reflects one of the advantages of the present invention.
• the coating were not applied to the fastener, it would be necessary to place a viscous wet-sealant material into the hole and onto the rivet prior to its installation, which in turn coats the contacting adjacent surfaces of the metallic and/or non-metallic components.
• the wet- sealant material is potentially toxic to workers, messy, difficult to work with, and necessitates the use of extensive cleanup tools as well as exposing surfaces of the pieces 42 and 44 to caustic chemical solutions after installation of the fastener.
• the presence of residual wet-sealant inhibits the adhesion of later-applied paint and other topcoats applied over the bolt heads.
• the pre-coating process of the present invention overcomes these problems confronted by the use of wet-sealants.
• wet-sealant is not needed or used during fastener installations and subsequent component assembly.
• the later-applied paint or other topcoats adhere well over the pre-coated bolt heads.
• a large cargo aircraft might have in excess of 1,000,000 fasteners.
• aircraft composite fasteners the elimination of the requirement for the wet-sealant installation approach for a large portion of those fasteners offers a significant cost savings.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Paints Or Removers (AREA)

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• 2005
  • 2005-02-22 WO PCT/US2005/005566 patent/WO2005092517A1/en not_active Ceased
  • 2005-02-22 EP EP05713920A patent/EP1735111A1/de not_active Withdrawn

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