Composite materials

Abstract

A composite material, the composite material comprising a prepreg, said prepreg comprising at least one polymeric resin and at least one conductive fibrous reinforcement, electrically conducting particles dispersed in the polymeric resin and a top layer of a metal-coated carbon fibre comprising a further resin component, wherein the metal comprises one or more metals selected from nickel, copper, gold, platinum, palladium, indium and silver.

1 . A method for making a composite assembly for use in making a lightning strike tolerant composite material, said method comprising the steps of:
 providing an interleaf structured panel comprising a first fibrous layer comprising an upper surface and a lower surface and a second fibrous layer comprising an upper surface and a lower surface, said first and second fibrous layers being electrically conductive and wherein the lower surface of said first fibrous layer is separated from the upper surface of said second fibrous layer;   locating a resin layer between the lower surface of said first fibrous layer and the upper surface of said second fibrous layers, said resin layer comprising an electrically insulating polymeric resin and having a thickness;   forming electrically conductive bridges that extend across said resin layer from the lower surface of said first fibrous layer to the upper surface of said second fibrous layer in order to provide electrical connections between said fibrous layers, wherein at least one of said electrically conductive bridges comprises an electrically conductive particle which has a particle size that is substantially equal to the thickness of said resin layer; and   locating a top layer next to the upper surface of said first fibrous layer, said top layer comprising metal-coated carbon fiber and a resin component.   
     
     
         2 . A method for making a composite assembly according to  claim 1 , wherein the electrically conductive particles comprise metal-coated conducting particles or non-metallic conducting particles. 
     
     
         3 . A method for making a composite assembly according to  claim 2 , wherein said non-metallic conducting particles are selected from carbon particles, graphite flakes, graphite powders, graphite particles, graphene sheets, fullerenes, carbon black, intrinsically conducting polymers, charge transfer complexes, or any combination thereof. 
     
     
         4 . A method for making a composite assembly according to  claim 1 , wherein the interleaf structured panel further comprises carbon nanomaterials. 
     
     
         5 . A method for making a composite assembly according to  claim 4 , wherein the carbon nanomaterials are selected from carbon nanofibers, carbon nanotubes, or a combination thereof. 
     
     
         6 . A method for making composite assembly according to  claim 1 , wherein the electrically insulating polymeric resin includes additional ingredients selected from flexibilizers, toughening agents/particles, additional accelerators, core shell rubbers, flame retardants, wetting agents, pigments/dyes, flame retardants, plasticizers, UV absorbers, anti-fungal compounds, fillers, viscosity modifiers/flow control agents, tackifiers, stabilisers, inhibitors, or a combination of any two or more thereof 
     
     
         7 . A method for making a composite assembly according to  claim 6 , wherein the toughening agents/particles include any of the following either alone or in combination: polyamides, copolyamides, polyimides, aramids, polyketones, polyetheretherketones, polyarylene ethers, polyesters, polyurethanes, polysulphones, high performance hydrocarbon polymers, liquid crystal polymers, polytetrafluoroethylene, elastomers, and segmented elastomers. 
     
     
         8 . A method for making a lightning strike tolerant composite material that comprises the step of curing a composite assembly according to  claim 1 . 
     
     
         9 . A method for making an aerospace component that comprises the method of making a lightning strike tolerant composite material according to  claim 8 . 
     
     
         10 . A method for making an airplane that comprises the method of making a lightning strike tolerant composite material according to  claim 8 . 
     
     
         11 . A method for making a composite assembly according to  claim 1  wherein at least 50 percent of the electrically conductive particles have a particle size that is within 10 microns of the thickness of the resin layer. 
     
     
         12 . A method for making a composite assembly according to  claim 3  wherein said non-metallic conducting particles comprise carbon. 
     
     
         13 . A method for making a composite assembly according to  claim 1  wherein said electrically conductive particles are present in the range of 0.2 vol. % to 20 vol. % of the composite assembly. 
     
     
         14 . A method for making a composite assembly according to  claim 1  wherein said electrically conductive particles have a diameter in the range of 5 microns to 40 microns. 
     
     
         15 . A method for making a composite assembly according to  claim 1  wherein said fibrous layers comprise carbon fibers that are formed substantially from carbon. 
     
     
         16 . A method for making a composite assembly according to  claim 1  wherein said metal-coated carbon fibers comprise carbon fibers coated with copper and nickel. 
     
     
         17 . A method for making a composite assembly according to  claim 1  wherein said electrically insulating polymer resin comprises an epoxy resin. 
     
     
         18 . A method for making a composite assembly according to  claim 17  wherein said electrically insulting polymer resin comprises polyethersulfone. 
     
     
         19 . A method for making a composite assembly according to  claim 1  which includes the step of locating an additional resin layer between said top layer and the upper surface of said first fibrous layer, said additional resin layer comprising an electrically insulating polymeric resin and having a thickness, wherein electrically conductive bridges are provided that extend across said additional resin layer from the upper surface of said first fibrous layer to said top layer in order to provide electrical connections between said first fibrous layer and said top layer, wherein at least one of said electrically conductive bridges comprises an electrically conductive particle which has a particle size that is substantially equal to the thickness of said additional resin layer.