• 专利附录
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    • 专利摘要:
    ELECTRICALLY CONDUCTIVE INTEGRATED SURFACE MATERIAL, COMPOSITE STRUCTURE, METHOD FOR FORMING A COMPOSITE STRUCTURE, AND, COMPOSITE PANEL. Multifunctional surface materials for use in composite structures are described. In one embodiment, the surface material includes (a) a stiffening layer, (b) a curable resin layer, (c) a conductive layer, and (d) a non-woven layer, wherein the stiffening layer ( a) and the non-woven layer (d) are outermost layers, and the exposed surfaces of the outermost layers are substantially free of tack at room temperature (20°C to 25°C). The conductive layer may be interposed between the curable resin layer and the stiffening layer or embedded in the curable resin layer. In another embodiment, the surface material includes a fluid barrier film between two curable resin layers. Surface materials can be in the form of an elongated or continuous ribbon that is suitable for automated positioning.
    公开号:BR112018010824B1
    申请号:R112018010824-3
    申请日:2016-11-29
    公开日:2022-02-01
    发明作者:Junjie Jeffrey Sang；Dalip Kumar Kohli；Kevin R. Mullery
    申请人:Cytec Industries Inc；
    IPC主号:
    专利说明:

    [001] In recent years, resin-impregnated fiber-reinforced composite materials have been used in the manufacture of aerospace structural parts, such as aircraft wings and fuselage. Composite materials used in the manufacture of aerospace component parts must have certain characteristics to protect the parts from damage or scratches caused by common environmental occurrences such as lightning strikes, rain, snow and moisture. Lightning strikes can severely damage and/or pass through component parts if such parts are not properly conductive and grounded throughout the aircraft. Fluid and hydration ingress into composite sandwich panels that contain foam or honeycomb core is a common problem. Accordingly, it is desirable that such component parts be manufactured to have features that, among other features, prevent or alleviate damage caused by lightning strikes and fluid ingress. BRIEF DESCRIPTION OF THE DRAWINGS
    [002] Figure 1 schematically shows the components of an integrated conductive surface material according to one embodiment.
    [003] Figure 2 schematically shows the cross-section of an integrated conductive surface material according to another embodiment.
    [004] Figure 3 schematically shows the components of a fluid barrier surface material according to another embodiment.
    [005] Figure 4 schematically shows the components of a conductive fluid barrier surface material according to another embodiment.
    [006] Figure 5 schematically shows the components of a composite honeycomb sandwich structure panel with a fluid barrier surface material.
    [007] Figure 6 is a photographic image of the surface tape that was cut for Automated Fiber Positioning (AFP) application, which shows clean edges.
    [008] Figure 7 is a photographic image of two AFP surface tapes with PEKK surfaces facing up. DETAILED DESCRIPTION
    [009] To minimize lightning strike damage to a composite structure, there is a need to enhance the electrical conductivity of the composite structure to provide lightning strike protection (LSP) for aerospace composite parts. It is not desirable, however, to incorporate conductive material that will significantly increase the overall weight of the aircraft.
    [0010] One aspect of the present description relates to an integrated electrically conductive surface material that has the ability to provide protection for lightning strikes. This surface material can be applied over an outer surface of a composite structure, for example a composite aircraft part, as a protective material.
    [0011] The conductive surface material can be in the form of a flexible tape, which is light weight and is configured for an automated positioning process, such as Automated Tape Placement (ATL) or Automated Fiber Placement (AFP). Due to its property of flexibility and light weight, the surface tape can be deposited at a significantly faster rate as compared to conventional resin impregnated pre-preg tapes. The surface tape may have a width of from about 3.17 mm to about 305 mm (or 0.125 in to about 12 in). In one embodiment, the surface tape has a width of about 3.17 mm to about 38.1 mm (or about 0.125 in to about 1.5 in), which includes about 6.35 mm to about 6.35 mm to about 1.5 in. from 12.77 mm (or about 0.25 in to about 0.50 in). In another embodiment, the surface tape has a width of from about 152 mm to about 305 mm (or about 6 in to about 12 in). The length of the tape is continuous or quite long in relation to its width, eg 100 to 100,000 times its width. Continuously, the surface tape can be wound onto a reel for storage prior to application in an automated process.
    [0012] ATL and AFP are processes that use computer-guided robotics to deposit the continuous tapes onto a mold surface (eg, a mandrel) to build a composite structure or fibrous preform. The ATL/AFP process involves laying one or more tapes side by side over a mandrel surface to create a layer of desired width and length, and then additional layers are stacked on top of a previous layer to provide a laminate stacking sequence of a desired thickness. Subsequent tapes can be oriented at different angles to the previous tapes. The ATL/AFP system is equipped with means for distributing and compacting the tapes directly onto the mandrel surface.
    [0013] AFP can automatically deposit multiple individual tows (or very narrow cut tapes) (e.g. 0.125 in to 1.5 in) on a mandrel to constitute a given total bandwidth. Material positioning is performed at high speed, using a numerically controlled positioning head to distribute, grip, cut and restart each tow during positioning. The ATL machine can deposit resin impregnated tapes or continuous strips of cloth, which are wider than the tows used in AFP. Typically, with both processes, material is applied via a robotically controlled head, which contains the necessary mechanism for material positioning. AFP is traditionally used on very complex surfaces.
    [0014] According to one embodiment, which is schematically illustrated by Figure 1, the conductive surface material is an integrated structure comprising a very thin conductive layer 11 sandwiched between a stiffening layer 12 and a curable resin layer 13 and a non-woven layer 14 in contact with the curable resin layer 13. When the surface material is applied onto a composite substrate, the stiffening layer 12 is in contact with the composite substrate so that the non-woven layer 14 is the outermost layer on the composite substrate after positioning the surface material. The outer surfaces of stiffening layer 12 and non-woven layer 14 are substantially or completely free of tack.
    [0015] The conductive layer may be a continuous non-porous layer of metal or non-metallic conductive material with a thickness of less than about 102 μm, in some embodiments in the range of about 5 μm to about 75 μm, or about from 3 μm to about 5 μm. Alternatively, the conductive layer may be a porous layer, for example, a fabric having a regional weight within the range of about 60 gsm to about 350 gsm, in some embodiments, about 60 gsm to about 195 gsm. Also, the porous conductive layer may have a thickness within the range of about 50 µm to about 102 µm (or 2-4 mils). “Gsm” refers to g/m2. When the conductive layer is a metal layer, the metal can be selected from copper, aluminum, bronze, titanium and alloys thereof. In some embodiments, the porous conductive layer is a metal screen or expanded metal laminate. In other embodiments, the conductive layer is formed of a non-metallic material with intrinsic electrical conductivity, such as sheet-shaped carbon, which includes graphene sheet and carbon nanotube (CNT) paper. A specific example of CNT paper is flexible CNT Buckypaper.
    [0016] The curable resin layer 13 may have a regional weight of less than about 500 gsm, for example, about 50 gsm to about 150 gsm. It is free from any reinforcing fibers such as carbon fibers. The composition of the curable resin layer is discussed in more detail below.
    [0017] When the conductive surface material is in the form of elongated or continuous tape, the entire tape may have a total regional weight of about 270 gsm to about 380 gsm. The total tape thickness can be in the range of about 76 μm to about 229 μm (or 3 to 9 mils).
    [0018] The stiffening layer 12 provides resistibility, rigidity and support to the surface tape during automated positioning, and prevents the “accordion” effect when surface material in the form of narrow-width tapes (or cut tows) is deposited by automated positioning. The “accordion” effect refers to the creping and buildup of the tape (or cut tow) during automated positioning, such as in the AFP or ATL process.
    [0019] The non-woven layer 14 is applied to the exposed surface of the curable resin layer 13 in order to inhibit the curable resin layer, which is adhesive, from adhering to other surfaces prior to the intended use of the surface material. However, the curable resin layer 13 does not penetrate through the thickness of the nonwoven layer 14. The nonwoven layer 14 is a nonwoven sheet of randomly oriented fibers, and can be manufactured by a conventional wet lay process. The fibers of the nonwoven layer 14 can be polymeric fibers, such as polyester and polyamide fibers, or inorganic fibers such as glass fibers and carbon fibers. A non-woven layer of metal-coated fibers, such as metal-coated carbon fibers, metal-coated polyester fibers, metal-coated glass fibers, and metal-coated polyamide fibers, is also contemplated. The metal coating on the fibers can be any metal that includes copper, nickel, silver and a combination thereof. The nonwoven layer 14 may have a regional weight of from about 10 gsm to about 50 gsm, in some embodiments, from about 10 gsm to about 22 gsm.
    [0020] In another embodiment, the nonwoven layer 14 is the layer of uncoated fibers, for example polymeric fibers or carbon fibers, coated with a thin metal coating on one or both surfaces after the nonwoven layer has been formed. For example, the nonwoven layer 14 can be a nonwoven sheet of carbon fibers or polyester fibers with a thin metal coating (e.g. copper, nickel, silver or a combination thereof) deposited on the surface which is not contact with curable layer 13. The regional weight of the metal coating may be in the range of about 1 gsm to about 25 gsm (or about 10% to about 50% by weight) of the metal coated nonwoven layer. MODALITIES WITH THERMOPLASTIC LAYER
    [0021] In one embodiment, the stiffening layer is a continuous non-porous thermoplastic layer that can also serve as a fluid barrier, and can improve the damage tolerance of composite structures. The thermoplastic layer can be from about 50 µm to about 153 µm thick (or about 2 to about 6 mils), particularly when the surface material is in the form of continuous or elongated ribbons for automated positioning. However, greater thickness is possible depending on the application of the surface material. In that embodiment, the thermoplastic layer does not contain any reinforcing fibers, and the integrated surface material also does not include any additional layer of reinforcing fibers, such as carbon fibers.
    [0022] The thermoplastic layer is characterized by the following structural properties: a tensile modulus from about 640 MPa (or 93 ksi) to about 2.1 GPa (or 305 ksi), as measured by ASTM D-882; a yield tensile strength of from about 27 MPa (or 4 ksi) to about 76 MPa (or 11 ksi) as measured by ASTM D-882, a break tensile strength of from about 76 MPa (or 11 ksi) 41 MPa (or 5.9 ksi) to about 110 MPa (or 16 ksi), as measured by ASTM D-882; and an elongation at deformation or breakage of from about 4% to about 10%, as measured by ASTM D-882, wherein all properties are determined at about 23°C. Furthermore, the thermoplastic layer is non-adhesive at room temperature (20°C to 25°C), which means that it is dry (i.e., non-sticky) to the touch.
    [0023] In one embodiment, the thermoplastic layer is formed from a semicrystalline thermoplastic polymer that has a melting temperature (Tm) greater than 280°C, more specifically, 280°C to 360°C, as measured by Differential Scanning Calorimetry (DSC) at an elevation rate of 10 °C/minute. A particularly suitable class of polymers is polyaryl ether ketone (PAEK).
    [0024] PAEK polymers are polymers that contain the unit -Ar-O-Ar-C(=O)-, where each Ar is independently an aromatic moiety. Specific examples of PAEK polymers include poly (ether ketone) ("PEK"), poly (ether ketone ether) ("PEEK"), poly (ether ketone ether) ("PEKK"), poly (ether ketone ether ketone) ( "PEKEKK"), poly (ether ketone ether ether ketone) ("PEEKEKK"), poly (diphenyl ether ketone ether) ("PEDK"), poly (diphenyl ether ketone ether) ("PEDEK"), poly (diphenyl ether ether ketone) ketone ketone) ("PEDEKK") and poly (naphthalene ether ketone ether) ("PEKEN"). Commercially available PAEK polymers include APC-2® PEEK, CYPEK®-DSM or DSE or FC, and CYPEK®-HTE, which are all commercially available from Cytec Industries Inc.
    [0025] Other thermoplastic polymers can be used to form the thermoplastic layer, as long as these polymers have the tensile modulus, tensile strength and elongation discussed above. Other suitable thermoplastic polymers include polyimide (e.g. Kapton® HN, and Dupont VN-type polyimide film), polyether-imide (e.g., SABIC PEI Ultem™ 1000B film), polyamide-imide (e.g. Torlon® 4000TF from Solvay), polyamide (e.g. Stanyl® high performance polyamide 46 film from DSM), polyester (e.g. Mylar® Polyethylene terephthalate (PET, PETP) polyester films from Valox ), polysulfone (e.g. Udel® PSU film from CS Hyde Company) and combinations thereof. MODALITIES WITH GLASS RESINS
    [0026] In another embodiment, the surface material comprises the components shown in Figure 1, wherein the stiffening layer 12 is composed of a woven cloth or non-woven veil that has been coated or infused with a curable resin-containing composition ( or resins) glassy thermosetting.
    [0027] The glassy thermosetting resin refers to a solid and brittle material at room temperature (20 °C to 25 °C). In addition, the woven cloth or non-woven veil coated/infused with the glass resin composition has minimal or no tack at room temperature (20°C to 25°C), meaning that it is substantially or completely dry (i.e. , not sticky) to the touch.
    [0028] Novolacs Epoxy Cresol represented by the following formula are particularly suitable:
    on what
    n = 1 to 6
    [0029] Examples of commercially available Cresol Epoxy Novolacs include Araldite® ECN 1273, 1280, 1299, 9511 from Ciba Specialty Chemicals.
    [0030] Other suitable glass thermoset resins are low hydration epoxy hydrocarbon novolac resins with a dicyclopentadiene backbone (DCPD) represented by the following formula:
    on what
    n = 1 to 3
    [0031] Examples of commercially available DPCD-based epoxy Novolacs include Huntsman's Tactix® 556 and Tactix® 756;
    [0032] Also suitable are solid epoxy adducts, which are solid reaction products (or condensation products) of epichlorohydrin and bisphenol A and are represented by the following formula:
    where n = 2 to 7.
    [0033] Such solid epoxy adducts may have an Epoxide Equivalent Weight (g/eq) of from about 500 to about 930, for example, 500-560 or 860-930, as determined by ASTM D-1652. These materials are solid at room temperature (20°C-25°C) and have a softening temperature above 60°C. In some embodiments, the epoxy adduct may have a softening temperature of about 65°C to about 140°C, for example, 75°C - 85°C or 100°C - 110°C, as determined by ASTM D-3104. Specific commercially available examples of such solid epoxy adducts are D.E.R.™ 661 and D.E.R.™ 664 from Dow Chemical Co.
    [0034] Woven cloth that can be coated or infused with the glass resin composition is a lightweight woven cloth composed of continuous fibers such as glass fibers, particularly E-glass fibers, which have a regional weight within in the range of about 10 gsm to about 50 gsm. E-glass is an alumino-borosilicate glass with less than 1% by weight alkali oxides. In addition to glass fibers, other suitable fibers include carbon fibers, thermoplastic fibers such as polyamide fibers and polyester fibers. Metal coated fibers or metallic fibers are also contemplated. Examples of metal-coated fibers include metal-coated carbon fibers, metal-coated polyester fibers, metal-coated glass fibers, and metal-coated polyamide fibers. The metal coating on the fibers can be copper, nickel, silver, copper-silver and a combination thereof. Woven fibers can have diameters within the range of about 10 μm to about 15 μm (microns).
    [0035] The non-woven web suitable for the purpose herein is a lightweight, highly porous non-woven material composed of chopped fibers, which are randomly oriented and held together by a small amount of binder, such as PVA (poly vinyl alcohol). ). The fibers of the web may be polymeric fibers, inorganic fibers, or metal coated fibers, as described for the non-woven layer 14. Like the non-woven layer 14, the non-woven web may be manufactured by a conventional wet lay process. The fibers can have lengths within the range of about 10 mm to about 15 mm, and diameters within the range of 10 μm to 15 μm. In preferred embodiments, the nonwoven web has a regional weight within the range of about 10 gsm to about 50 gsm, in some embodiments, about 10 gsm to about 35 gsm.
    [0036] In one embodiment, one or more thermosetting resins described above (Novolac Epoxy Cresol, DCPD backbone epoxy novolac, or solid epoxy adduct) is/are mixed with a curing agent, an organic solvent and, optionally, a flow control agent, to form a coating solution that contains about 65% to about 75% solids by weight. The coating solution may additionally include a small amount of a thermoplastic polymer. The components can be mixed in a shear mixer at room temperature until a substantially homogeneous mixture is formed. When solid epoxy adduct is used, the epoxy adduct is optionally further ground into a fine powder before being mixed with the other components. The resulting resin solution is then coated on both sides of a glass cloth or veil, followed by drying.
    [0037] Suitable curing agents for epoxy novolacs and epoxy adducts can be selected from amine curing agents, e.g. dicyandiamide (DICY), 4,4'-diaminodiphenylsulfone (4,4'DDS) and 3 ,3'-diaminodiphenylsulfone (3,3'DDS), guanamine, guanidine, aminoguanidine, piperidine and non-amine curing agents such as boron trifluoride (BF3) or complexes thereof, and acid anhydrides. In one embodiment, the curing agent is dicyandiamide. The ratio of resin to curing agent in the coating solution is such that there are about 5 parts to about 30 parts curing agent per 100 parts of glassy resin (or resins) by weight.
    [0038] Suitable organic solvents include, but are not limited to, Methyl Ethyl Ketone (MEK), Acetone, Toluene, PMA, Chloroform, Toluene-MIBK, Ethylene Chloride, and Xylene-MIBK. The Cresol Epoxy Novolacs, DCPD backbone epoxy novolac and solid epoxy adduct described herein are soluble in such solvents.
    [0039] Suitable flow control agents include inorganic fillers in particulate form (eg, powder). Such a flow control agent is added to the coating solution as a rheology modifying component to control the flow of the resin composition and to prevent agglomeration therein. Suitable inorganic fillers that can be used in the resin coating composition include talc, mica, calcium carbonate, alumina and fumed silica. In one embodiment, hydrophobic fumed silica powder (eg, Cab-O-Sil® TS-720 from Cabot Corporation) is used as the flow control agent. The amount of flow control agent can be within the range of about 1 part to about 5 parts by weight based on 100 parts of the glassy thermosetting resin (or resins). A flow control agent in particulate form, such as fumed silica powder, is particularly suitable.
    [0040] The thermoplastic polymer can be selected from polyaryl sulfones such as polyether sulfone (PES), polyether ether sulfone (PEES), and a copolymer of PES and PEES, polyether imide (PEI) (e.g. Ultem ™ by General Electric). The amount of thermoplastic polymer can be from about 1 part to about 20 parts per 100 parts of thermosetting resin (or resins).
    [0041] The glassy resin composition may additionally include a small amount (less than 20 parts per 100 parts of glassy thermosetting resin) of bismaleimide or BMI, e.g. Huntsman's Matrimid ® 5292A, in powder form as a quenching agent .
    [0042] Table 1 describes some exemplary solvent based resin formulations for coating woven cloth or non-woven web. TABLE 1

    [0043] In an alternative embodiment, the thermosetting glass resin (cresol epoxy novolac, DCPD-based epoxy novolacs or epoxy adduct) is mixed with a curing agent and, optionally, a flow control agent and/or a polymer. thermoplastic, without the use of solvent to form a molten mixture. Mixing of the components is performed in a mixer capable of heating/cooling and vacuum to mix the resin mix components evenly. The molten mixture is then used to form a solid resin layer, for example by coating with thermofused film over a backing layer (glass cloth or veil carrier) or removable paper, followed by cooling to solidify the resin. . The solid resin layer is then contacted with a woven cloth or non-woven veil. Heat and pressure are applied to melt the resin layer and infuse the cloth or veil with the molten resin. One layer of resin can be pressed against one side of the cloth/veil or two layers of resin can be pressed against opposite sides of the cloth/veil. MODALITIES WITH VEILS/GLASS CLOTH AND NON-WOVEN LAYER
    [0044] In yet another embodiment, depicted by Figure 2, the integrated surface material is a surface material comprising a porous conductive layer 21 embedded in a curable resin layer 22, an outer woven cloth or non-woven veil 23 ( hereinafter referred to as the "fibrous layer"), and an outer nonwoven layer 24. The outer surfaces of the fibrous layer 23 and the nonwoven layer 24 are substantially or completely free of tack. And the curable resin 22 does not penetrate through the thickness of either the fibrous layer 23 or the nonwoven layer 24. When this surface material is positioned on a composite substrate, the fibrous layer 23 is in contact with the composite substrate to provide rigidity and strength. non-woven layer 24 becomes the outermost layer of the composite part. The porous conductive layer 21 is as described previously with reference to Figure 1. In one embodiment, the porous conductive layer is a metal screen. The woven cloth or non-woven veil 23 is as previously described for other embodiments. The non-woven layer 24 is as described previously with reference to the non-woven layer 14 in Figure 1. In one embodiment, the layers 23 and 24 are non-woven webs of the same or different regional weights. When layers 23 and 24 are nonwoven webs with different regional weights, the nonwoven web with the highest regional weight will be in contact with the composite substrate and the nonwoven web with the lowest regional weight will be the outermost layer in the final composite. after the surface material has been applied. This surface material may be in the form of a narrow width tape for automated positioning such as ATL or AFP as described previously.
    [0045] The integrated surface material of Figure 2 can be manufactured by first forming a layer of curable resin over a removable backing layer, for example a release paper. A porous conductive sheet, for example a metal screen, is positioned on the exposed surface of the curable resin layer, then heat and pressure are applied to the bundled layers in order to insert the porous conductive sheet into the resin layer. Subsequently, each of the fibrous layer 23 and the non-woven layer 24 is laminated separately on an opposite side of the resulting resin layer. The pressure is applied to bond the fibrous layer 23 and the nonwoven layer 24 to the resin layer, however, it is not high enough to cause substantial or complete penetration of the resin into both the fibrous layer 23 and the nonwoven layer 24. FLUID BARRIER
    [0046] Another aspect of the present description relates to a surface material that functions as an external fluid barrier in a composite structure. Such a fluid barrier is particularly useful for a composite sandwich panel that contains a porous core. Composite sandwich panels typically have composite shells cured with adhesives to the core through autoclave processing. The core material can take a variety of forms, such as a lightweight blister, rigid foam, paper, or wood. Preferably, the core is a honeycomb material, as it provides ideal structural properties for a very low weight of material. Composite sandwich panels find wide use in aerospace structural components due to their high stiffness-to-weight and strength-to-weight ratios.
    [0047] Figure 3 illustrates an embodiment of a fluid barrier surface material 30 that includes a first layer of curable resin 31, a second layer of curable resin 32 and a barrier film 33 sandwiched between the layers of resin. The curable resin layers and barrier film form an integrated structure. The first and second resin layers each contain one or more thermosetting resins and a curing agent, and do not contain any reinforcing fibers.
    [0048] In some embodiments, at least one of the first and second resin layers additionally comprises an inorganic filler in particulate form selected from: TiO2 powder, nanosized silica, nanosized clay, carbon, graphite, graphene, nanotubes carbon (CNT) and combinations thereof. The presence of such an inorganic filler increases the hydrophobicity of the resin layers and provides synergy with the barrier film to eliminate any fluid ingress into the composite structure below the surface material.
    [0049] The barrier film is formed of a polymeric material that is impermeable to liquid. Preferred properties for the polymeric material include high Tg, e.g. within 140 °C to 170 °C), or 150 °C to 162 °C, as measured by DSC at a rise rate of 10 °C/minute according to with ASTM D3418. Another preferred property is 3% to 50% crystallinity, which includes 10% to 40%, or 20% to 30%, as measured by DSC at a rise rate of 10°C/minute per ASTM D3418.
    [0050] As examples, the barrier film can be manufactured from a thermoplastic material selected from: Polyaryl-ether-ketone (PAEK) polymers, polyamide, poly-imide, poly-ether-imide (PEI), polyamide-imide, polyester and combinations thereof. In some embodiments, the barrier film composition contains a PAEK polymer selected from: poly (ether ketone) ("PEK"), poly (ether ketone ether) ("PEEK"), poly (ether ketone ether) (" PEKK"), poly (ether ketone ether ketone ether) ("PEKEKK"), poly (ether ketone ether ether ketone ether) ("PEEKEEK"), poly (diphenyl ether ketone ether) ("PEDK"), poly (diphenyl ether ether ketone ketone) ("PEDEK"), poly (diphenyl ether ketone ether ketone) ("PEDEKK"), and poly (naphthalene ether ether ketone ether) ("PEKEN") and combinations thereof.
    [0051] Figure 4 illustrates another embodiment of fluid barrier surface material 40, which includes a first curable resin layer 41, a second curable resin layer 42, a barrier film 43, and a conductive layer 44. Four layers form an integrated structure. Barrier film 43 and conductive layer 44 are positioned between the two resin layers. The curable resin layers and barrier film are as previously described. Conductive layer 44 is as described above with reference to Figure 1. In this embodiment, the surface material may provide LSP in addition to providing a fluid barrier.
    [0052] Figure 5 shows the components of an exemplary composite sandwich panel having the fluid barrier surface material of Figure 3 or Figure 4 incorporated therein. As shown in Figure 5, the composite sandwich panel includes a surface material (50), a first prepreg skin 51, a second prepreg skin 52, a honeycomb core 53 and adhesive films 54, 55 to bond ( by means of co-curing or secondary bonding) the pre-impregnated shells to the honeycomb core. Each pre-impregnated shell is composed of several curable pre-impregnated tarpaulins.
    [0053] The general method for producing the honeycomb sandwich panel includes laminating the honeycomb core with the prepreg shells and adhesive films on both sides, the fluid barrier surface material on one of the shells, and curing all components. to link them together. Another way to manufacture the same honeycomb sandwich panel is through secondary bonding, as in the case of panel repair. In this secondary bonding process, pre-preg pre-cured shell surfaces are treated with mechanical abrasion (eg, sanding or abrasive blasting) or a peel-off tarpaulin to create a surface ready for bonding. Then, the pre-cured shells are bonded with honeycomb core by means of an adhesive film through a curing process. Then, the fluid barrier surface material is applied to an outer surface of the cured honeycomb sandwich panel followed by curing the surface material to form a hardened protective outer layer.
    [0054] The adhesive for bonding the honeycomb core to the pre-impregnated shells can be formed from a thermosetting composition that contains one or more thermosetting resins, for example epoxy resins and a curing agent. For example, commercially available epoxy based adhesives FM 309-1 and FM 300 from Cytec Engineered Material Inc. can be used. CURABLE RESIN
    [0055] The terms "curing" and "curing" as used herein refer to the irreversible hardening of a prepolymer material or a resin precursor generated by heating at elevated temperatures, exposure to ultraviolet light and radiation or chemical additives. The term “curable” means capable of being cured into a hardened material. "Partially cured" as used herein refers to less than 100% degree of cure.
    [0056] Each of the curable resin layer described in the various embodiments, particularly with reference to Figures 1 to 4, is formed from a thermosetting composition that contains one or more thermosetting resins and a curing agent.
    [0057] Examples of suitable thermosetting resins include, but are not limited to, epoxies, phenolic resins, cyanate esters, bismaleimides, benzoxazines (which include polybenzoxazines), unsaturated polyesters, vinyl ester resins, and combinations thereof.
    [0058] In some embodiments, the thermosetting composition contains one or more multifunctional epoxy resins. Multifunctional epoxy resin (or polyepoxide) contains two or more epoxy functional groups per molecule.
    [0059] Examples of suitable multifunctional epoxy resins include polyglycidyl ethers, which are prepared by reacting epichlorohydrin or epibromohydrin with a polyphenol in the presence of alkali. Suitable polyphenols are, for example, resorcinol, pyrocatechol, hydroquinone, bisphenol A (bis(4-hydroxyphenyl)-2,2-propane), bisphenol F (bis(4-hydroxyphenyl)methane), bis(4-hydroxyphenyl)-1 ,1-isobutane, 4,4'-dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,1-ethane and 1,5-hydroxynaphthalene.
    [0060] Also included are polyglycidyl ethers of polyalcohols. Such polyalcohols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, and trimethylolpropane.
    [0061] Additional epoxy resins include polyglycidyl esters of polycarboxylic acids, for example, reaction products of glycidol or epichlorohydrin with aliphatic or aromatic polycarboxylic acids, such as oxalic acid, succinic acid, glutaric acid, terephthalic acid or a dimeric fatty acid.
    [0062] Other epoxides may include those derived from the epoxidation products of olefinically unsaturated cycloaliphatic compounds or from natural oils and fats.
    [0063] Also included are liquid epoxy resins, which are reaction products of bisphenol A or bisphenol F and epichlorohydrin. Such epoxy resins are liquid at room temperature and generally have an epoxy equivalent weight (g/eq) of from about 150 to about 480 as determined by ASTM D-1652.
    [0064] Particularly suitable are epoxy novolac resins that are polyglycidyl derivatives of phenol-formaldehyde novolacs or cresol-formaldehyde novolacs that have the following chemical structure:
    where n = 0 to 5, and R = H or CH 3 . When R=H, the resin is a novolac phenol resin. When R=CH3, the resin is a cresol novolac resin. Said is commercially available as DEN 428, DEN 431, DEN 438, DEN 439 and DEN 485 from Dow Chemical Co. The latter is commercially available as ECN 1235, ECN 1273 and ECN 1299 from Ciba-Geigy Corp. Other suitable novolacs that can be used include SU-8 from Celanese Polymer Specialty Co. In a preferred embodiment, the epoxy novolac resin has a viscosity of 4000-10,000 mPa/s at 25°C, and Epoxide Equivalent Weight (EEW) of from about 190 g/eq to about 235 g/eq as determined by ASTM D -1652.
    [0065] A particularly suitable multifunctional epoxy resin is a tetrafunctional aromatic epoxy resin having four epoxy functional groups per molecule and at least one glycidyl amine group. An example is methylene dianeline tetraglycidyl ether which has the following general chemical structure:

    [0066] The amine groups in structure are shown at the para- or 4,4' positions of the aromatic ring structures, however, it should be understood that other isomers such as 2,1', 2,3', 2,4' , 3.3', 3.4' are possible alternatives. Examples of commercially available tetra-functional epoxy resins are Araldite® MY 9663, MY 9634, MY 9655, MY-721, MY-720, MY-725 provided by Huntsman Advanced Materials.
    [0067] Another particularly suitable multifunctional epoxy resin is trifunctional epoxy resin, for example aminophenol triglycidyl ether. Specific examples of commercially available tri-functional epoxy resins are Araldite® MY 0510, MY 0500, MY 0600, MY 0610 provided by Huntsman Advanced Materials.
    [0068] The curable resin composition can be formulated to provide high Tg and high crosslink density. In some embodiments, a combination of epoxy novolac resin (or resins) and non-novolac multifunctional epoxy resin (or resins) (particularly tri-functional and/or tetra-functional epoxy) is used. The relative amounts of epoxy novolac resin and non-novolac multifunctional epoxy resin can be varied, however, it is preferred that the amount of epoxy novolac resin is in the range of about 80 to about 100 parts per 100 parts of non-novolac multifunctional epoxy resin. The combination of epoxy novolac resin and multifunctional epoxy resin in the specified ratio contributes to the desired high Tg and crosslink density upon cure.
    [0069] The total amount of all resins constitutes at least 15% by weight based on the total weight of the resin film composition. As an example, the total amount of resins can constitute from about 30% to about 60% by weight based on the total weight of the thermoset composition, or from about 15% to about 25% by weight.
    [0070] In some embodiments, the resin composition includes a combination of certain multifunctional thermosetting resins, a polymeric hardening component to harden the resin matrix, a latent amine-based curing agent, ceramic microspheres as a fluid barrier component , and particulate inorganic fillers as a rheology modification component. The multifunctional resins and ceramic microspheres constitute more than 35% by weight of the total composition, preferably more than 45% by weight. POLYMERIC TEMPERING AGENTS
    [0071] The thermosetting composition may additionally include one or more polymeric tempering agents. The polymeric quenching agents can be selected from the group consisting of: thermoplastic polymers, elastomers, shell-core rubber particles, a pre-reacted adduct which is a reaction product of an epoxy resin, a bisphenol, and a elastomeric polymer and combinations thereof. In some embodiments, a combination of two different quenching agents from this group is used. The total amount of tempering agent (or agents) can be from about 1% to about 30%, in some cases, from about 10% to about 20% by weight based on the total weight of the composition. With respect to the pre-reacted adduct, suitable epoxy resins include bisphenol A diglycidyl ether, bisphenol A tetrabromo diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, or hydrogenated bisphenol F diglycidyl ether. Cycloaliphatic epoxies, which include compounds that contain at least one cycloaliphatic group and at least two oxirane rings per molecule, are also suitable. Specific examples include cycloaliphatic alcohol diepoxide, hydrogenated bisphenol A represented by the following structure:

    [0072] An example of such a cycloaliphatic epoxy resin is EPALLOY® 5000 (a cycloaliphatic epoxy prepared by hydrogenating bisphenol A diglycidyl ether) available from CVC Thermoset Specialties. Other cycloaliphatic epoxides suitable for use in the pre-reacted adduct may include EPONEX cycloaliphatic epoxy resins, for example, EPONEX Resin 1510 provided by Momentive Specialty Chemicals.
    [0073] The bisphenol in the pre-reacted adduct functions as a chain extending agent for linear or cycloaliphatic epoxy. Suitable bisphenols include bisphenol A, tetrabromo bisphenol A (TBBA), Bisphenol Z, and tetramethyl bisphenol A (TMBP-A).
    [0074] Suitable elastomers to form the pre-reacted adduct include, but are not limited to, liquid elastomers such as amine terminated acrylonitrile butadiene (ATBN), carboxyl terminated acrylonitrile butadiene (CTBN), and carboxyl terminated butadiene ( CTB). Fluorocarbon elastomers, silicone elastomers and styrene-butadiene polymers are also possible. In one embodiment, the elastomer used in the pre-reacted adduct is ATNB, CTBN, or CTB.
    [0075] In one embodiment, the epoxy resin is reacted with the bisphenol chain-extending agent and the polymer elastomer in the presence of a catalyst, such as triphenyl phosphine (TPP), at about 300°F (or 148.9°C). ) to chain the epoxy resins together and to form a high-molecular-weight, film-forming, high-viscosity, pre-reacted epoxy resin adduct. The pre-reacted adduct is then mixed with the remaining components of the thermosetting composition.
    [0076] Suitable thermoplastic hardeners include polyarylsulfone polymers such as polyether sulfone (PES) and polyether ether sulfone (PEES). In some embodiments, the quenching agent is a copolymer of PES and PEES, which is described in US Patent No. 7084213. In some embodiments, the hardener is poly(oxy-1,4-phenylenesulfonyl-1,4-phenylene), which has a Tg of about 200°C as measured by DSC.
    [0077] The hardener component may be shell-core rubber (CSR) particles that have a particle size of 300 nm or less. CSR particles can be any of the shell-core particles in which a soft core is surrounded by a hard capsule. Preferred CSR particles are those having a polybutadiene rubber core or acrylonitrile-butadiene rubber core and a polyacrylate shell. CSR particles that have a hard core surrounded by a soft capsule can also be used, however. CSR particles can be supplied as 25% to 40% by weight percentage of CSR particles dispersed in a liquid epoxy resin. CSR particles that have rubber cores and polyacrylate shells are commercially available from Kaneka Texas Corporation (Houston, Tex.) under the trademarks Kane Ace MX. It is preferred, but not required, that the shell-core rubber particles be added to the surface film composition as a suspension of particles in a suitable liquid epoxy resin. Kane Ace MX 411 is a suspension of 25% by weight shell-core rubber particles in MY 721 epoxy resin and is a suitable source of shell-core rubber particles. Kane Ace MX 120, MX 125, or MX 156, which contain 25 to 37% by weight of the same shell-core rubber particles dispersed in DER 331 resin, is also a suitable source of shell-core rubber particles. Another suitable source of shell-core rubber particles, such as MX 257, MX 215, MX217 and MX 451, can also be used. Another commercial source of shell-core rubber particles is Paraloid™ EXL-2691 from Dow Chemical Co. (CSR methacrylate-butadiene-styrene particles with an average particle size of about 200 nm). HEALING AGENTS
    [0078] Multifunctional epoxy resins can be cured by a variety of latent amine-based curing agents, which are activated at elevated temperatures (eg, temperature above 150°F (65°C)). Examples of suitable curing agents include dicyandiamide (DICY), guanamine, guanidine, aminoguanidine and derivatives thereof. Compounds in the imidazole class and amine complexes can also be used. In one embodiment, the curing agent is dicyandiamide. The amine-based curing agent is present in an amount within the range of about 1% to about 5% by weight based on the total weight of the resin film composition.
    [0079] A curing accelerator can be used in conjunction with the amine-based curing agent to promote the curing reaction between the epoxy resins and the amine-based curing agent. Suitable curing accelerators may include alkyl and aryl substituted ureas (which include aromatic or alicyclic dimethyl urea), and bisureas based on toluenediamine or methylene dianelline. An example of a bisurea is 4,4'-methylene bis(phenyl dimethyl urea), commercially available as Omicure U-52 or CA 152 from CVC Chemicals, which is a suitable accelerator for dicyandiamide. Another example is 2,4-toluene bis(dimethyl urea), commercially available as Omicure U-24 or CA 150 from CVC Chemicals. The curing accelerator may be present in an amount within the range of from about 0.5% to about 3% by weight based on the total weight of the heat-setting composition. CERAMIC MICROSPHERES
    [0080] Ceramic microspheres can be added to the thermosetting composition to improve the surface smoothness of the resin film formed therefrom. They can be hollow or solid ceramic microspheres. In one embodiment, hollow ceramic microspheres fabricated from an inert silica-alumina ceramic material are used. Ceramic microspheres can have a crush strength of over 60,000 psi, a dielectric constant of about 3.7 to 4.6, a softening point in the range of 1,000 to 1,100 °C (or 1,832 to 2,012 °F) , and particle diameters ranging from 0.1 micron to 50 microns, or 1 to 50 microns. The high softening point of ceramic microspheres makes them non-absorbent to solvents, non-flammable and highly resistant to chemicals. Microspheres having diameters ranging from about 0.1 µm to about 20 µm, and preferably from about 1 µm to about 15 µm, have been found to be particularly suitable. An example of commercially available ceramic microspheres that are particularly suitable for use in the present resin film composition are sold by Zeelan Industries, Inc. under the Zeeospheres ® trademark, eg G-200, G210 and W-200. These are thick-walled, odorless, light gray, hollow silica-alumina spheres. In a preferred embodiment, the combination of the multifunctional resins and ceramic microspheres constitutes more than 50% by weight, preferably more than 60% by weight, of the resin film composition. In certain embodiments, the amount of ceramic microspheres is at least 20% by weight, based on the total weight of the resin film composition. In some embodiments, the amount of ceramic microspheres can be within the range of about 20% to about 40% by weight, or about 25% to about 35% by weight based on the total weight of the thermoset composition. In other embodiments, the amount of ceramic microspheres can be within the range of about 3% to about 15% by weight, or about 5% to about 10% by weight. FLOW CONTROL AGENTS
    [0081] Inorganic fillers in particulate form (eg, powder) are added to the thermoset composition as a rheology modifying component to control the flow of the resin composition and to prevent agglomeration therein. Suitable inorganic fillers that can be used in the resin film composition include talc, mica, calcium carbonate, alumina and fumed silica. In one embodiment, hydrophobic fumed silica (eg, Cab-O-Sil TS-720) is used as the inorganic filler. The amount of inorganic fillers can be within the range of about 1% to about 5% by weight based on the total weight of the thermosetting composition. OPTIONAL ADDITIVES
    [0082] The thermosetting composition may additionally include one or more optional additives that affect one or more of the mechanical, electrical, optical and thermal properties of the cured or uncured resin film. Such additives include, but are not limited to, ultraviolet (UV) stabilizers, pigments/dyes, and conductive materials. When such additives are used, their total amount is less than about 5% by weight based on the total weight of the thermosetting composition.
    [0083] Examples of UV stabilizers that can be added to the resin composition include butylated hydroxytoluene (BHT); 2-hydroxy-4-methoxy-benzophenone (eg UV-9); 2,4-bis(2,4-dimethylphenyl)-6-(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine (e.g. UV-1164 CYASORB® light absorber); 3,5-di-tert-butyl-4-hydroxybenzoic acid; n-hexadecyl ester (eg UV-2908 CYASORB ® light stabilizer); Pentaerythritol Tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (e.g. IRGANOX 1010) Liquid hindered amine-based photostabilizer from Ciba Specialty Chemicals, such as 2-(2H-benzotriazole- 2-yl)-4,6-ditertpentylphenol (e.g. TINUVIN 328), methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate (e.g. TINUVIN 292). Decanedioic acid, BIS(2, 2,6,6-Tetramethyl-1-(octyloxy)-4-piperidinyl ester (eg TINUVIN 123) can also be used as suitable UV stabilizers. In addition, nanosized zinc oxide (n-ZnO), for example , NanoSunGuard 3015 and titanium oxide nanoparticles (n-TiO2) can also be used as UV stabilizers.
    [0084] Pigments and/or dyes known in the art to add color to resin systems can be added to the resin film composition. Examples of pigments and/or dyes include, but are not limited to, iron oxide red, chromium green, carbon black and titanium oxide. In one embodiment, titanium oxide pigment (white) is added to the resin film composition. In another embodiment, carbon black pigment is added.
    [0085] Conductive materials in particulate form, eg particles or flakes, can also be added to the resin film composition to impart electrical conductivity to the final resin film. Examples of suitable conductive materials include metals such as silver, gold, nickel, copper, aluminum, bronze and alloys thereof, in the form of flakes or particles. Carbon-based materials such as carbon nanotubes (single wall nanotubes or multiwall nanotubes), carbon nanofibers and graphene can also be used as conductive additives to impart electrical conductivity to the resin film. Nanofibers can have diameters ranging from 70 to 200 nanometers and a length of around 50-200 microns. Nanotubes can have an outside diameter of about 10 nanometers, a length of about 10,000 nanometers, and an aspect ratio (L/D) of about 1000. In addition, conductive additives can also include carbon black particles (such as such as DeGussa's Printex XE2).
    [0086] In one embodiment, the heat-setting composition to form the curable resin layer or matrix has the following formulation, in percent by weight based on the total weight of the composition: 20% to 25% epoxy phenol novolac resin; 20% to 25% tetra-functional epoxy resin; 10% to 15% pre-reacted adduct, 1% to 3% PES-PEES copolymer, 25% to 35% ceramic microspheres; 1% to 5% latent amine curing agent; 0.5% to 3% curing accelerator; 1% to 3% inorganic fillers; and, optionally, 0.1 to 1% color pigment.
    [0087] In another embodiment, the thermosetting composition has the following formulation, in percent by weight based on the total weight of the composition: 5% to 15% epoxy phenol novolac resin; 5% to 15% tetra-functional epoxy resin; 10% to 20% pre-reacted adduct, 1% to 3% PES-PEES copolymer, 25% to 35% ceramic microspheres; 1% to 5% latent amine curing agent; 0.5% to 3% curing accelerator; 1% to 3% inorganic fillers; and 45% to 70% conductive additives, such as silver flakes or silver-copper flakes, or carbon-based nanosized materials discussed above.
    [0088] The components of the thermosetting composition can be added to a shear mixer equipped with mixing, heating and/or cooling mechanisms. In addition, one or more organic solvents may also be added to the mixture as needed to facilitate mixing of the components. Examples of such solvents may include, but are not limited to, methyl ethyl ketone (MEK), acetone, dimethylacetamide, and N-methylpyrrolidone.
    [0089] To facilitate manipulation of the resin layer, the thermosetting composition is applied over a removable backing layer as described above to form a resin layer. The resin layer can be formed using a hot melt coating process if no solvent is used or a solution coating process if solvent is used. If solvent is used, subsequent drying of the resin layer will be necessary to remove volatiles. APPLICATIONS
    [0090] The surface materials described herein may be applied over and cured with a fiber reinforced polymeric composite substrate at a temperature above 150°F (65°C), more particularly within the range of 200°F to 365°F (or 93°C to 185°C). The fiber reinforced polymeric composite substrate is composed of reinforcing fibers that have been impregnated or infused with a curable matrix resin. In some embodiments, the composite substrate may be a prepreg tarpaulin or prepreg laminate stacking sequence. The prepreg laminate stacking sequence is composed of a plurality of prepreg plies arranged in a stacking sequence. Each pre-impregnated tarpaulin is composed of reinforcing fibers in the form of a cloth or directionally aligned, continuous fibers that have been impregnated/infused with a matrix resin, eg epoxy resin. Directionally aligned fibers can be unidirectional or multidirectional fibers. In general, the curable conductive surface material can be applied over a fiber-reinforced polymer composite substrate, which is in an uncured or partially cured state, followed by cocuring to form a fully cured composite structure that has a hardened surface film attached. at the same as the outermost layer.
    [0091] In the form of continuous surface tape, surface material can be deposited onto a composite substrate by automated positioning, such as ATL and AFP processes. The surface tape can be incorporated into an ATL/AFP process that automatically deposits pre-preg, resin-impregnated, continuous tapes to form the composite structure. Each pre-impregnated tape is composed of unidirectional reinforcing fibers, eg carbon fibers, which are embedded in a curable resin matrix, eg epoxy-based matrix. In the automated positioning process, individual pre-preg strips are deposited directly onto a mandrel or mold surface at high speed, using one or more numerically controlled positioning heads to dispense, grip, cut and restart each strip during positioning. . The prepreg tapes are distributed side by side to create a layer of a desired width and length and then additional layers are stacked on top of a previous layer to provide a prepreg laminate stacking sequence of a desired thickness. Then, the surface tapes are deposited in the pre-preg laminate stacking sequence to form the outermost layer. Such an ATL/AFP process is conventionally used for the fabrication of large composite aerospace structures, such as fuselage cutouts or aircraft wing skins. This automated positioning process eliminates some of the intermediate p-steps that are typical in conventional methods of manually applying large surface films over an existing pre-preg laminate stacking sequence.
    [0092] For surface material with fluid barrier property, the described fluid barrier surface material can be used to manufacture aircraft structural parts (such as wing, fuselage, tail and engine nacelle structure, etc.). The use of such a multipurpose fluid barrier surface material as an outer protective layer provides multifaceted benefits, which include elimination of fluid ingress, good surface properties and LSP at significant cost savings. EXAMPLES
    [0093] The following examples serve to provide specific embodiments of the surface materials in accordance with the present description, however, they are not intended to limit the scope of the present description in any way. EXAMPLE 1
    [0094] PEKK in a pellet form was fed into a single vane extruder, which was heated to the temperatures required to melt the PEKK pellets as they travel through the extruder barrel. The molten material leaving the extruder enters a mold to form a PEKK film, which is subsequently cooled.
    [0095] The PEKK film was then laminated to a copper screen (73 gsm) and an SM 905 curable coating layer (90 gsm) from Cytec Industries Inc. with the copper screen sandwiched between the PEKK layer and the coating layer. A 12gsm non-woven polyester mat was laminated to the exposed surface of the surface film with application of heat and pressure, which resulted in an integrated laminated structure. Lamination did not cause the coating layer resin to penetrate through the thickness of the non-woven polyester mat. Also, the resulting laminate had external surfaces that were free of tack. The laminate was then cut into narrow strips about 6.35 mm (or 0.25 in) wide, which is suitable for an AFP process. Figure 6 shows the newly cut tape with PEKK surface described. It was observed that the side edges of the cut tape were clean and there was no deformation of the copper screen during slit cutting. Figure 7 is a photographic image of two cut strips of AFP with PEKK surfaces facing upwards. EXAMPLE 2
    [0096] A coating resin solution was prepared according to the following formulation: • Solid Epoxy Adduct (DER 661), jet-ground: 100g • MEK solvent: 50g • DICY: 15g • Fumed silica (Cabosil TS 720) : 5g
    [0097] The components were mixed at room temperature (23°C) in a high speed shear mixer until a substantially homogeneous resin solution was formed. The solids content of this solution was approximately 70% solids by weight.
    [0098] The resin solution was then coated onto both sides of glass cloth (Cloth of Glass 108 provided by BGF Industries) at a regional weight of 48 gsm. The total regional weight of resin coated glass cloth was approximately 100 gsm, and the thickness was approximately 102 μm (or 4 mils).
    [0099] The resin coated glass cloth was then combined with a copper screen (175gsm), a SM 905 curable coating layer (90gsm) from Cytec Industries Inc., and a 10 gsm non-woven glass mat. gsm, wherein the copper screen is sandwiched between the resin-coated glass cloth and the coating layer, and the coating layer is in contact with the non-woven glass mat. Heat and pressure were applied to the bundled layers to form an integrated laminated structure. However, the resin of the coating layer did not penetrate through the thickness of the non-woven polyester mat. The laminate was then cut into narrow strips 6.35 mm (or 0.25 in) wide. EXAMPLE 3
    [00100] A copper screen (175 gsm) was embedded in a surface curable SM 905 film (90 gsm) by applying heat and pressure. A non-woven glass veil with a regional weight of 17 gsm (Optiveil® by Technical Fiber Products) was laminated to one side of the screen-containing resin layer, with the application of heat and pressure, to bond the glass veil to the fiber layer. resin, however, the resin of the coating layer did not penetrate through the thickness of the glass veil and so a 10 gsm glass veil (Optiveil® from Technical Fiber Products) was similarly bonded to the opposite side of the resin layer. The resulting laminate was cut into narrow strips 6.35 mm (or 0.25 in) wide. The 10gsm glass veil will be the outermost surface layer after the surface tape has been applied to a composite substrate, and the 17gsm glass veil will be in contact with the composite substrate. EXAMPLE 4
    [00101] A copper screen (175 gsm) was embedded in a surface curable SM 905 film (90 gsm) by applying heat and pressure. A non-woven carbon web with a regional weight of 8 gsm (Optiveil® by Technical Fiber Products) was laminated to one side of the screen-containing resin layer, with the application of heat and pressure, to bond the web to the resin layer, however, the resin from the coating layer did not penetrate through the thickness of the web, so another 8 gsm carbon web (Optiveil® from Technical Fiber Products) was similarly bonded to the opposite side of the resin layer. The resulting laminate was cut into narrow strips 6.35 mm (or 0.25 in) wide. One of the carbon veils will be the outermost surface layer after the surface tape has been applied to a composite substrate, and the other will be in contact with the composite substrate. EXAMPLE 5
    [00102] A copper screen (175 gsm) was embedded in a surface curable SM 905 film (90 gsm) by applying heat and pressure. A copper-clad carbon veil (i.e., non-woven copper-clad carbon fibers) with a regional weight of 12 gsm (Optiveil® by Technical Fiber Products) was laminated to one side of the screen-containing resin layer, with application heat and pressure to bond the web to the resin layer, however, the resin from the coating layer did not penetrate through the web thickness and then another copper coated carbon web, regional weight 12 gsm (Optiveil® from Technical Fiber Products) was similarly bonded to the opposite side of the resin layer. The resulting laminate was cut into narrow strips 6.35 mm (or 0.25 in) wide. One of the copper coated carbon veils will be the outermost surface layer after the surface tape has been applied to a composite substrate, and the other will be in contact with the composite substrate. TERMS, DEFINITIONS AND ABBREVIATIONS
    [00103] In the present description, the modifier “approximately” and “about” used in connection with a quantity is inclusive of the declared value and has the meaning dictated by the context, (e.g. includes the degree of error associated with the measurement of the quantity private). For example, a number followed by “about” could mean the mentioned number plus or minus 0.1% to 1% of that mentioned number. The suffix “(s)” as used herein is intended to include both the singular and the plural of the term it modifies, which thus includes one or more of that term (e.g., the metal (or metals) includes one or more more metals). The ranges described in this document are inclusive of the endpoints and all values in between ranges, for example, “1% to 10%” includes 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, etc.
    [00104] While various embodiments are described herein, it will be understood from the specification that various combinations of elements, variations or improvements thereof can be made by those skilled in the art, and are within the scope of the invention. Additionally, many modifications can be made to adapt a particular situation or material to the teachings of the invention without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiment described as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments that fall within the scope of the appended claims.
    权利要求:
    Claims (15)
    [0001]
    1. Integrated electrically conductive surface material, characterized in that it comprises: (a) a stiffening layer; (b) a curable resin layer comprising one or more thermosetting resins and a curing agent; (c) a conductive layer between the stiffening layer and the curable resin layer; and (d) a non-woven layer laminated to the curable resin layer, wherein the stiffening layer (a) and the non-woven layer (d) are outermost layers, and the exposed surfaces of the outermost layers are substantially free of tack. at room temperature (20°C to 25°C), wherein the stiffening layer is a non-porous thermoplastic layer comprising one or more polyaryl ether ketone (PAEK) polymers.
    [0002]
    2. Electrically conductive surface material according to claim 1, characterized in that the PAEK polymers are selected from the group consisting of: poly (ether ketone) ("PEK"), poly (ether ketone ether) ("PEEK"), poly (ether ketone ether ketone) ("PEKK"), poly (ether ketone ether ether ketone) ("PEKEKK"), poly (ether ketone ether ether ketone) ("PEEKEEK"), poly (ether ketone ether ether ketone) diphenyl ketone) ("PEDK"), poly (diphenyl ether ketone ether) ("PEDEK"), poly (diphenyl ether ketone ether) ("PEDEKK") and poly (naphthalene ether ketone ether) ("PEKEN").
    [0003]
    3. Electrically conductive surface material according to claim 1 or 2, characterized in that the conductive layer is a porous or non-porous metallic layer of copper, aluminum, bronze, titanium or alloys thereof.
    [0004]
    4. Electrically conductive surface material according to any one of claims 1 to 3, characterized in that the conductive layer is a non-porous layer that has a thickness of less than 76 μm, preferably the conductive layer is a laminate of non-porous metal.
    [0005]
    5. Electrically conductive surface material according to any one of claims 1 to 3, characterized in that the conductive layer is a porous layer with a regional weight within the range of 60 gsm to 350 gsm, preferably, the conductive layer is a metal sheet or an expanded metal laminate.
    [0006]
    6. Electrically conductive surface material according to any one of the preceding claims, characterized in that the non-woven layer (d) comprises randomly oriented fibers selected from the group consisting of: polymeric fibers, inorganic fibers, fibers coated with metal and combinations thereof.
    [0007]
    7. Electrically conductive surface material according to claim 6, characterized in that the fibers of the non-woven layer (d) are selected from the group consisting of: carbon fibers, metal-coated carbon fibers, fibers metal-coated glass fibers, metal-coated polyester fibers, metal-coated polyamide fibers, and combinations thereof.
    [0008]
    8. Electrically conductive surface material according to claim 7, characterized in that the fibers of the non-woven layer (d) are selected from the group consisting of: polyamide fibers, polyester fibers, glass fibers and combinations thereof.
    [0009]
    9. Electrically conductive surface material according to any one of the preceding claims, characterized in that the non-woven layer (d) has a regional weight within the range of 10 gsm to 50 gsm.
    [0010]
    An electrically conductive surface material according to any one of the preceding claims, characterized in that the non-woven layer (d) additionally comprises a metal coating that is not in contact with the curable resin layer (b).
    [0011]
    11. Electrically conductive surface material according to any one of the preceding claims, characterized in that the surface material is in the form of an elongated or continuous tape which is suitable for automated positioning, preferably the tape has a width at range from 3.17 mm to 305 mm and a length that is at least ten (10) times its width.
    [0012]
    12. Electrically conductive surface material according to claim 11, characterized in that the total thickness of the tape is within the range of 76 μm to 229 μm.
    [0013]
    13. Composite structure, characterized in that it comprises: a composite substrate comprising reinforcing fibers impregnated with a curable matrix resin; electrically conductive surface material as defined in any one of claims 1 to 13, laminated to a surface of the composite substrate so that the stiffening layer is in contact with the composite substrate.
    [0014]
    14. Composite structure according to claim 13, characterized in that said composite substrate is a pre-preg laminate stacking sequence, comprising a plurality of pre-preg plies arranged in a stacking arrangement, each Pre-impregnated canvas comprises unidirectional reinforcing fibers impregnated with or embedded in a curable matrix resin.
    [0015]
    15. Method for forming a composite structure characterized in that it comprises: forming a composite substrate comprising reinforcing fibers impregnated with a curable matrix resin, preferably, the composite substrate is formed by laminating pre-impregnated tapes in a process of automated positioning, which includes dispensing and compacting prepreg tapes directly onto a molding surface; distributing a plurality of surface materials as defined in any one of claims 11 to 12, in the form of continuous or elongated strips, side by side, directly onto the composite substrate by an automated positioning process to form a protective coating layer on the substrate composite, wherein the stiffening layer on the surface material faces the composite substrate during automated positioning; and cure the protective coating layer and composite substrate.
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    EP3383640A1|2018-10-10|
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    WO2017095810A1|2017-06-08|
    AU2020233766A1|2020-10-15|
    JP6987761B2|2022-01-05|
    CN108367526A|2018-08-03|
    AU2016365119B2|2020-09-10|
    US20180346146A1|2018-12-06|
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    US20210253270A1|2021-08-19|
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    法律状态:
    2020-03-10| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2021-12-28| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2022-02-01| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 29/11/2016, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    US201562260824P| true| 2015-11-30|2015-11-30|
    US62/260824|2015-11-30|
    PCT/US2016/064002|WO2017095810A1|2015-11-30|2016-11-29|Surfacing materials for composite structures|
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