Nano-reinforced filler material for epoxy resin systems and method for its manufacture - Patents.com

Abstract

To provide a method for producing a nano reinforcement filler material for epoxy resin for a composite structure.SOLUTION: A method includes a step of generating a polymer suspension of polymer nanoparticles suspended in deionization (DI) water, and a step of subjecting the polymer suspension to ultrasonic treatment. The method includes a step of generating a graphene oxide (GO) suspension of a GO sheet suspended in the DI water, and a step of subjecting the GO suspension to ultrasonic treatment. The method includes a step of mixing a polymer suspension subjected to the ultrasonic treatment and the GO suspension subjected to the ultrasonic treatment. The method includes a step of heating the mixture subjected to the ultrasonic treatment in an inert atmosphere at an effective temperature to obtain a nano reinforcement filler material containing polymer-GO core-shell nanoparticles using an electrostatic process by an electrostatic interaction reaction. The method includes a step of cleaning and drying the nano reinforcement filler material, and using the nano reinforcement filler material in an epoxy resin for a composite structure.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates generally to reinforcing or toughening materials for composite structures, and more particularly to nano-reinforcing filler materials for epoxy resin systems for composite structures, such as aircraft composite structures and other composite structures. [Background technology]

[0002] Due to their high strength to weight ratio, corrosion resistance and other advantageous properties, composite materials are used in a wide variety of structures and components, including their use in the manufacture of aircraft, spacecraft, rotorcraft, ships, automobiles, trucks and other vehicles. In particular, in aircraft construction, an increasing number of composite structures and components are being used to form fuselages, wings, tails, skin panels and other aircraft components.

[0003] Epoxy resins are commonly used as the matrix of fiber-reinforced composites due to their high temperature performance, chemical resistance and good adhesive properties. Such epoxy resins include epoxy polymers, which are structural thermosetting polymers that become permanently hard after curing. However, epoxy polymers have a three-dimensional cross-linked structure that can be vulnerable to crack propagation. Therefore, it may be necessary to add reinforcing or toughening filler materials to the epoxy resins to improve not only the fracture toughness but also other mechanical and physical properties.

[0004] There are known reinforcing or toughening filler materials for epoxy resins. For example, such known reinforcing or toughening filler materials may include carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber and core-shell glass beads-polymer microspheres. However, such known reinforcing or toughening filler materials may improve fracture toughness, but may adversely affect other physical properties, such as strength and thermal properties.

[0005] Furthermore, known reinforcing or toughening filler materials for epoxy resins include nano-reinforcing filler materials, such as inorganic silica nanoparticles. However, such inorganic silica nanoparticles have a high density that can result in undesirable composites with high weight. Heavy composite structures may be undesirable for aircraft, spacecraft, and other vehicles, as the increased weight leads to increased fuel usage and higher costs. Therefore, composite materials that allow for the production of structures with lower weight are advantageous and desirable.

[0006] Furthermore, known nano-reinforced filler materials for epoxy resins include graphene and modified graphene-reinforced filler materials such as graphene oxide (GO) nanosheets, i.e., GO sheets, obtained by oxidative exfoliation of graphite. Graphene oxide (GO) sheets have many hydroxyl, epoxy and carboxyl groups, which have chemical affinity with epoxy resins at their surface and edges, imparting good functionalization, processing and water solubility to GO sheets. Graphene oxide (GO) sheets have been investigated at extremely low loading levels of 0.1-3 wt% (weight percent) to improve mechanical properties without compromising other physical properties. However, various problems can exist, such as particle aggregation. Furthermore, it is not well understood how the shape and size of such GO sheets can be controlled, which can affect the resulting properties of the composite.

[0007] Furthermore, such known graphene oxide (GO) sheets (nanosheets) may undesirably self-stacking again after synthesis and drying process. To prevent or avoid the restacking of individual GO sheets, the use of a solvent may be necessary. However, the presence of any residual solvent may interfere with the crosslinking reaction between the GO sheets and the epoxy resin matrix, which may adversely affect the mechanical properties of the epoxy resin matrix. To prevent or avoid the presence of any residual solvent, solvent removal may be necessary. Such solvent removal may require the use of a vacuum oven or another solvent removal device to remove the solvent. Such solvent removal may be very time-consuming (i.e., 23h (23 hours) or more) and may be very expensive. Although solvent-free addition has been utilized for the synthesis of GO-coated inorganic silica nanoparticles, solvent-free addition is required for the synthesis of GO-coated organic nanoparticles, such as polymeric nanoparticles.

[0008] Additionally, known nano-reinforced filler materials for epoxy resins include known graphene oxide (GO) sheets (nanosheets) used with nanoparticles, such as polymer nanoparticles. However, such known GO-coated polymer nanoparticles include polymer nanoparticles ranging in size from 350 nm (nanometers) to several microns, which may require the use of large sized GO sheets. Large polymer nanoparticles may reduce the surface area of ​​the interaction or interface between the GO sheets and the epoxy resin matrix.

[0009] In addition, the large size of GO sheets may cover many particles in a single GO sheet, leading to agglomeration of particle structure. The covered agglomerated particles in a single GO sheet may interfere with the curing reaction of epoxy with the resin matrix, which may lead to unsatisfactory mechanical properties of the nano-reinforced filler materials.

[0010] Thus, there is a need in the art for improved nano-reinforced filler materials and methods of manufacture for use with epoxy resin systems for composite structures that provide improved interaction with the epoxy resin matrix, are solvent-free, reduce synthesis or production time, and reduce the weight of the composite structure, providing advantages over known nano-reinforced filler materials and methods. Summary of the Invention [Problem to be solved by the invention]

[0011] This need is met for improved nano-reinforced filler materials and methods of making same. As described in the detailed description below, embodiments of the improved nano-reinforced filler materials and methods of making same can provide significant advantages over known materials and methods. [Means for solving the problem]

[0012] In an embodiment of the present disclosure, a method for producing a nano-reinforced filler material for an epoxy resin system for composite structures is provided. The method includes generating a polymer suspension including a plurality of polymer nanoparticles suspended in deionized (DI) water. The method further includes sonicating the polymer suspension to obtain an ultrasonicated polymer suspension.

[0013] The method further includes generating a graphene oxide (GO) suspension comprising a plurality of graphene oxide (GO) sheets suspended in deionized (DI) water, and sonicating the graphene oxide (GO) suspension to obtain a sonicated graphene oxide (GO) suspension.

[0014] The method further comprises mixing the sonicated polymer suspension and the sonicated graphene oxide (GO) suspension together in a mixing vessel to obtain an sonicated mixture, and heating the sonicated mixture in an inert atmosphere at an effective temperature and utilizing an electrostatic process to uniformly coat the individual polymer nanoparticles with individual graphene oxide (GO) sheets by electrostatic interaction reaction to obtain a nano-reinforced filler material comprising polymer-GO core-shell nanoparticles.

[0015] The method further includes washing the nano-reinforced filler material and drying the nano-reinforced filler material. The method further includes using the nano-reinforced filler material in an epoxy resin system for a composite structure to provide a toughening nano-reinforcement to the epoxy resin system.

[0016] In another embodiment of the present disclosure, a method for producing a nano-reinforced filler material for an epoxy resin system for composite structures is provided. The method includes generating a polystyrene (PS) suspension including a plurality of polystyrene (PS) nanoparticles suspended in deionized (DI) water. Each of the plurality of polystyrene (PS) nanoparticles has a particle size within a range of about 40 nm (40 nanometers) to about 150 nm (150 nanometers). The method further includes sonicating the polystyrene (PS) suspension to obtain an sonicated polystyrene (PS) suspension.

[0017] The method further includes generating a graphene oxide (GO) suspension comprising a plurality of graphene oxide (GO) sheets suspended in deionized (DI) water, and sonicating the graphene oxide (GO) suspension to obtain a sonicated graphene oxide (GO) suspension.

[0018] The method further includes mixing the sonicated polystyrene (PS) suspension and the sonicated graphene oxide (GO) suspension together in a mixing vessel to obtain a sonicated mixture, and heating the sonicated mixture in an inert atmosphere at an effective temperature within a range of about 70° C. (seventy degrees Celsius) to about 100° C. (one hundred degrees Celsius) and utilizing an electrostatic process to uniformly coat the individual polystyrene (PS) nanoparticles with individual graphene oxide (GO) sheets by electrostatic interaction reaction to obtain a nano-reinforced filler material comprising polystyrene-GO core-shell nanoparticles.

[0019] The method further includes washing the nano-reinforced filler material and drying the nano-reinforced filler material. The method further includes using the nano-reinforced filler material in an epoxy resin system for a composite structure to provide a toughening nano-reinforcement to the epoxy resin system.

[0020] In another embodiment of the present disclosure, a nano-reinforced filler material for an epoxy resin system for composite structures is provided, the nano-reinforced filler material comprising a plurality of polymer-graphene oxide (GO) core-shell nanoparticles, each of which comprises a polymer core portion and a graphene oxide (GO) shell portion.

[0021] The plurality of polymer-graphene oxide (GO) core-shell nanoparticles includes a plurality of polymer nanoparticles prepared by suspending in deionized (DI) water and then sonicating via a sonication process to obtain an ultrasonicated polymer suspension. Each polymer nanoparticle has a particle size within a range of about 40 nm (40 nanometers) to about 150 nm (150 nanometers), and each has a spherical shape (84).

[0022] The plurality of polymer-graphene oxide (GO) core-shell nanoparticles further comprise a plurality of graphene oxide (GO) sheets by suspending in deionized (DI) water (102) and then sonicating via a sonication process to obtain an ultrasonicated graphene oxide (GO) suspension. The ultrasonicated graphene oxide (GO) suspension is prepared separately from the ultrasonicated polymer suspension. Each GO sheet has a sheet size within a range of about 50 nm (50 nanometers) to about 350 nm (350 nanometers), and each has a planar shape.

[0023] The ultrasonicated polymer suspension and the ultrasonicated GO suspension are mixed together to obtain an ultrasonicated mixture, which is heated in an inert atmosphere and undergoes an electrostatic process to uniformly coat the individual polymer nanoparticles with individual graphene oxide (GO) sheets through an electrostatic interaction reaction to obtain a nano-reinforced filler material, which is further washed, dried, and used in an epoxy resin system for composite structures.

[0024] The described features, functions, and advantages can be realized independently in various embodiments of the present disclosure or may be combined in yet further embodiments, further details of which can be seen by reference to the following description and drawings.

[0025] The present disclosure will be better understood with reference to the following more detailed description taken in conjunction with the accompanying drawings, which illustrate preferred exemplary embodiments, and which are not necessarily drawn to scale, in which: [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is an illustration of a perspective view of an aviation vehicle that may incorporate one or more composite structures reinforced with embodiments of the reinforcing filler material of the present disclosure. [Diagram 2] FIG. 1 is a flow diagram of an aircraft production and service method. [Diagram 3] 1 is an illustration of a block diagram of an aircraft. [Figure 4] FIG. 1 is a schematic diagram illustrating the production of an embodiment of a nano-reinforced filler material of the present disclosure. [Diagram 5] 1 is an illustration of a functional box diagram showing an embodiment of a nano-reinforced filler material and production system of the present disclosure. [Figure 6A] 1 is a flow diagram illustration of an exemplary embodiment of the method of the present disclosure. [Figure 6B] 1 is a flow diagram illustration of another exemplary embodiment of the method of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The disclosed embodiments will now be described in more detail below with reference to the accompanying drawings, which show some, but not all, of the disclosed embodiments. Indeed, several different embodiments may be described, and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are described so that this disclosure will be complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0028] 1 is an illustration of a perspective view of an air vehicle 10, such as in the form of an aircraft 12, that may incorporate one or more composite structures 28, such as in the form of an epoxy composite structure 28a, reinforced with an embodiment of a nano-reinforced filler material 150 (see FIGS. 4, 5) of the present disclosure. As further shown in FIG. 1, the air vehicle 10, such as in the form of an aircraft 12, includes a fuselage 14, a nose 16, wings 18, engines 20, and a tail 22 including a horizontal stabilizer 24 and a vertical stabilizer 26.

[0029] 1 generally represents a commercial passenger aircraft, the teachings of the disclosed embodiments may be applied to other passenger aircraft, cargo aircraft, military aircraft, rotorcraft, and other types of aircraft or air vehicles, as well as aerospace vehicles, satellites, space launch vehicles, rockets, and other aerospace vehicles. It can also be understood that composite structures reinforced with one or more embodiments of the nano-reinforced filler material 150 (see FIGS. 4, 5) in accordance with the present disclosure may be utilized in other transportation vehicles, such as boats and other watercraft, trains, cars, trucks, buses, or other suitable transportation vehicles.

[0030] 2 and 3, FIG. 2 is a flow diagram of an aircraft manufacturing and service method 30 and FIG. 3 is an exemplary block diagram of an aircraft 46. An embodiment of the present disclosure may be described in the context of the aircraft manufacturing and service method 30 shown in FIG. 2 and the aircraft 46 shown in FIG. 3. During up-front production, the exemplary aircraft manufacturing and service method 30 (see FIG. 2) may include specification and design 32 (see FIG. 2) and material procurement 34 (see FIG. 2) of the aircraft 46 (see FIG. 3). During production, component and subassembly manufacturing 36 (see FIG. 2) and system integration 38 (see FIG. 2) of the aircraft 46 (see FIG. 3) occurs. The aircraft 46 (see FIG. 3) may then undergo certification and delivery 40 (see FIG. 2) to be placed in service 42 (see FIG. 2). While in service 42 (see FIG. 2) by a customer, the aircraft 46 (see FIG. 3) may be scheduled for routine maintenance and service inspections 44 (see FIG. 2), which may include modifications, reconfigurations, modifications, and other suitable maintenance inspections.

[0031] Each of the processes of aircraft manufacturing and service method 30 (see FIG. 2 ) may be performed or carried out by a system integrator, a third party, and / or an operator (e.g., a customer). In this description, a system integrator may include, without limitation, any number of aircraft manufacturers and major system subcontractors, a third party may include, without limitation, any number of distributors, subcontractors, and suppliers, and an operator may include, without limitation, airlines, leasing companies, military entities, service organizations, and other suitable operators.

[0032] As shown in Figure 3, an aircraft 46 produced by the exemplary aircraft manufacturing and service method 30 may include an airframe 48 with a number of systems 50 and an interior 52. As further shown in Figure 3, example systems 50 may include one or more of a propulsion system 54, an electrical system 56, a hydraulic system 58, and an environmental system 60. Any number of other systems may be included. Although an aerospace example is shown, the principles of the present disclosure may be applied to other industries, such as the automotive industry.

[0033] Methods and systems embodied herein may be used during any one or more stages of aircraft manufacturing and service method 30 (see FIG. 2). For example, components or subassemblies corresponding to component and subassembly manufacturing 36 (see FIG. 2) may be produced or manufactured in a manner similar to components or subassemblies produced while aircraft 46 (see FIG. 3) is in service 42 (see FIG. 2). Also, one or more apparatus embodiments, method embodiments, or combinations thereof may be utilized during component and subassembly manufacturing 36 (see FIG. 2) as well as system integration 38 (see FIG. 2), for example, by significantly speeding up or reducing the cost of assembly of aircraft 46 (see FIG. 3). Similarly, one or more apparatus embodiments, method embodiments, or combinations thereof may be utilized during aircraft 46 (see FIG. 3) in service 42 (see FIG. 2), for example, without limitation, maintenance and service 44 (see FIG. 2).

[0034] 4 and 5, FIG. 4 is a schematic diagram illustrating the production of an embodiment of the nano-reinforced filler material 150 of the present disclosure. FIG. 5 is a functional box diagram illustration of an embodiment of the nano-reinforced filler material 150, 150a and production system 76 of the present disclosure. The nano-reinforced filler material 150 will be described in conjunction with FIG. 4 and FIG.

[0035] 4 shows a plurality of polymeric nanoparticles 80. Each of the plurality of polymeric nanoparticles 80 (see FIGS. 4 and 5) has a positive charge 82 (see FIGS. 4 and 5), a spherical shape 84 (see FIGS. 4 and 5), e.g., a microsphere shape, and a surface 86 (see FIG. 5), e.g., a curved surface.

[0036] Each of the plurality of polymeric nanoparticles 80 (see FIGS. 4 and 5) includes a polymer 78 (see FIG. 5) that forms a polymeric core portion 154 (see FIG. 5) of the nano-reinforced filler material 150 (see FIGS. 4 and 5).

[0037] The polymer 78 (see FIG. 5) is selected from the group consisting of polystyrene (PS) 78a (see FIG. 5), poly(methyl methacrylate) (PMMA), poly(butyl acrylate) (PBA), poly(butyl acrylate) (PBA)-poly(methyl methacrylate) (PMMA) (PBA-PMMA), butyl methyl acrylate (BMA), polyvinyl acetate, polyvinyl acetate copolymer, polychloroprene (neoprene), nitrile rubber, acrylic rubber, fluoroelastomer (FKM), polyisoprene, polyvinylidene fluoride, polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), styrene-butadiene or another suitable polymer. The polymer 78 (see FIG. 5) is preferably an allylic polymer with or without surface functionalization. Preferably, the polymer 78 is polystyrene (PS) 78a (see FIG. 5). The polystyrene nanoparticles 81 (see FIG. 5) used in the nano-reinforced filler material 150a (see FIG. 5) disclosed herein are available from Polysciences, Inc. of Warrington, Pennsylvania.

[0038] Preferably, each polymeric nanoparticle 80 (see FIGS. 4, 5) has a particle size 88 (see FIG. 5) within the range of about 30 nm (30 nanometers) to about 180 nm (180 nanometers). More preferably, each polymeric nanoparticle 80 (see FIGS. 4, 5) has a particle size 88 (see FIG. 5) within the range of about 40 nm (40 nanometers) to about 150 nm (150 nanometers). Most preferably, each polymeric nanoparticle 80 has a particle size 88 within the range of about 80 nm (80 nanometers) to about 100 nm (100 nanometers).

[0039] 4 further shows a plurality of polymer nanoparticles 80 suspended in deionized (DI) water 102 in a first container 104 to produce a polymer suspension 100. The production system 76 (see FIG. 5) includes DI water 102 (see FIG. 5). Preferably, the polymer suspension 100 (see FIG. 5) is a polystyrene suspension 101 (see FIG. 5). In one example of a step of producing or preparing the polymer suspension 100 (see FIG. 5), polystyrene (PS) nanoparticles 81 (see FIG. 5) have a concentration of 12 mg / ml (twelve milligrams per milliliter) and are suspended in 200 ml (two hundred milliliters) of DI water 102 (see FIG. 5) at ambient or room temperature.

[0040] 4 further illustrates a polymer suspension 100 including a plurality of polymer nanoparticles 80 suspended in DI water 102 via a sonication process 112 (see also FIG. 5), such as a bath sonication process using an ultrasonic processor 110 (see also FIG. 5), such as a bath sonication device. As used herein, "sonication process" refers to a process for applying energy, such as acoustic energy by ultrasound or other ultrasonic means, to agitate a suspension of particles, such as nanoparticles, in a liquid, such as deionized (DI) water, for the purposes of uniformly dispersing the nanoparticles in the liquid and breaking down any agglomerates of the nanoparticles, and / or to provide energy to drive certain chemical reactions.

[0041] As shown in FIG. 4, the sonication device 110 includes a sonication probe portion 114, such as a sonicator, partially submerged in the polymer suspension 100 in the first container 104. The sonication probe portion 114 provides a highly localized intensity directly above or adjacent the sonication zone or region being sonicated. However, the sonication device 110 may use other suitable types of devices in addition to the sonication probe portion acting as a sonicator, or the sonication device may be in the form of a sonication bath with a bath sonicator. As further shown in FIG. 4, the sonication probe portion 114 is connected to a sonication controller portion 116 of the sonication device 110. As further shown in FIG. 4, the first container 104 containing the polymer suspension 100 is placed on a sonication platform 118 of the sonication device 110. The sonication probe portion 114 emits acoustic energy 120 into the polymer suspension 100 during the sonication process 112. The polymer suspension 100 undergoes an ultrasonic treatment process 112 (see FIG. 4, FIG. 5) to obtain an ultrasonically treated polymer suspension 100a (see FIG. 4, FIG. 5). The ultrasonically treated polymer suspension 100a (see FIG. 5) is a well-dispersed suspension of polymer particles. When the polymer suspension 100 includes a polystyrene suspension 101 (see FIG. 5), and the polystyrene suspension 101 undergoes an ultrasonic treatment process 112 (see FIG. 4, FIG. 5), an ultrasonically treated polystyrene suspension 101a (see FIG. 5) is obtained. The ultrasonically treated polystyrene suspension 101a (see FIG. 5) is a well-dispersed suspension of polystyrene particles. Preferably, the polymer suspension 100 undergoes an ultrasonic treatment process 112 at ambient or room temperature for a time in the range of about 15 minutes to about 60 minutes, more preferably for a time of 15 minutes. The ultrasonic treatment process 112 helps to prevent the formation of agglomerates of the polymer nanoparticles 80 (i.e., multiple nanoparticles stuck together) and helps to remove any agglomerates of the polymer nanoparticles 80 that have formed. However, one may wish to avoid performing the ultrasonic treatment process 112 on the polymer suspension 100 for more than 60 minutes, as excessive exposure to ultrasonic waves may distort the morphology of the polymer nanoparticles 80.

[0042] 4 further illustrates a plurality of graphene oxide (GO) sheets 90, also referred to as GO nanosheets. Each of the plurality of GO sheets 90 (see FIGS. 4, 5) has a negative charge 92 (see FIGS. 4, 5), a planar shape 94 (see FIG. 5), e.g., a planar sheet shape, and a smooth surface 96 (see FIG. 5). Each of the GO sheets 90 forms a graphene oxide (GO) shell portion 156 (see FIG. 5) of the nano-reinforced filler material 150 (see FIGS. 4, 5).

[0043] Each of the plurality of GO sheets 90 (see Figs. 4, 5) comprises graphene oxide (GO), an oxidized form of graphene produced by oxidative exfoliation or oxidation of graphite in the presence of strong acids. GO contains a variety of oxygen-containing functional groups (e.g., hydroxyl, epoxy, carboxyl, ketone) that have chemical affinity with epoxy resins at its surface and edges. GO is preferably functionalized with small molecules or polymers for incorporation into an organic matrix, such as an epoxy resin matrix. Reduction of GO by chemical or thermal methods allows partial recovery of the original graphene framework. GO sheets improve mechanical properties at extremely low loading levels of 0.1-3 wt% (weight percent) without compromising other physical properties.

[0044] 4 further shows a plurality of graphene oxide (GO) sheets 90 suspended in deionized (DI) water 102 in a second container 108 to produce a graphene oxide (GO) suspension 106. In one example of producing or preparing a GO suspension 106 (see FIGS. 4, 5), GO sheets 90 (see FIG. 5) have a concentration of 1 mg / ml and are suspended in 200 ml of DI water 102 (see FIG. 5) at ambient or room temperature. The stability of the GO suspension 106 is very high and can be suspended for more than three months before use.

[0045] FIG. 4 further illustrates a GO suspension 106 including a plurality of GO sheets 90 suspended in DI water 102 via an ultrasonication process 112 (see also FIG. 5), such as a bath sonication process using an ultrasonicator 110 (see also FIG. 5), such as a bath sonication process. As shown in FIG. 4, the ultrasonicator 110 includes an ultrasonication probe portion 114, such as a sonicator, partially submerged in the GO suspension 106 in a second container 108. However, the ultrasonicator 110 may use other suitable types of devices in addition to the ultrasonication probe portion acting as a sonicator. As further shown in FIG. 4, the ultrasonication probe portion 114 is connected to an ultrasonication controller portion 116 of the ultrasonicator 110. As further shown in FIG. 4, the second container 108 containing the GO suspension 106 is placed on an ultrasonication platform 118 of the ultrasonicator 110. The ultrasonication probe portion 114 emits acoustic energy 120 into the GO suspension 106 during the ultrasonication process 112. The GO suspension 106 undergoes an ultrasonication process 112 (see FIGS. 4 and 5) to obtain an ultrasonicated GO suspension 106a (see FIGS. 4 and 5).

[0046] Preferably, the GO suspension 106 (see FIG. 5) undergoes an ultrasonic treatment process 112 (see FIG. 5) for an effective time to obtain the desired nano-sized GO sheets 90 for coating the polymer nanoparticles 80, such as polystyrene (PS) nanoparticles 81. When used to generate the GO suspension 106, prior to the ultrasonic treatment process 112, the GO sheets 90 initially have a sheet size 98 (see FIG. 5) in the range of about 500 nm (500 nanometers) to about 5 microns. The GO suspension 106 undergoes an ultrasonic treatment process 112 for an effective time to reduce the sheet size 98 (see FIG. 5) of the GO sheets 90, such as the lateral dimensions of the GO sheets 90. After undergoing an ultrasonic treatment process 112 for an effective time, the GO sheet 90 (see FIGS. 4, 5) has a sheet size 98 (see FIG. 5) that is preferably in the range of about 50 nm (50 nanometers) to about 350 nm (350 nanometers), more preferably in the range of about 150 nm (150 nanometers) to about 300 nm (300 nanometers), and most preferably in the range of about 200 nm (200 nanometers) to about 300 nm (300 nanometers).

[0047] As used herein, the "sheet size" of a GO sheet refers to the average sheet diameter or characteristic length scale of the GO sheet, including the lateral dimensions of the GO sheet. The sheet size 98 (see FIG. 5) of an individual or single GO sheet 90a (see FIG. 5) should be sufficient to completely and fully cover the surface 86 (see FIG. 5) of each individual polymeric nanoparticle 80a (see FIG. 5), with each polymeric nanoparticle 80 having a particle size 88 (see FIG. 5) in the range of about 30 nm (30 nanometers) to about 180 nm (180 nanometers). Each GO sheet 90 preferably has a thickness in the range of about 1 nm (1 nanometer) to about 5 nm (5 nanometers).

[0048] Preferably, the GO suspension 106 undergoes ultrasonication process 112 at ambient or room temperature for a time period ranging from about 1 h (one hour) to about 6 h (six hours). Preferably, during the ultrasonication process 112 of the GO suspension 106, the room temperature is kept below the thermal stability threshold of the GO sheets 90, e.g., below 50° C. (fifty degrees Celsius). In one example, to reduce the lateral dimensions of the GO sheets 90, the GO suspension 106 is first sonicated in ultrasonication process 112 (see FIGS. 4, 5) using an ultrasonicator 110 (see FIGS. 4, 5) in the form of a bath sonicator at room temperature for 2 h (two hours), and then subsequently sonicated in ultrasonication process 112 using the ultrasonicator 110 and ultrasonication probe unit 114 (see FIG. 4) at room temperature for 3 h (three hours).

[0049] The ultrasonicated GO suspension 106a (see FIG. 4, FIG. 5) is prepared separately from the ultrasonicated polymer suspension 100a at a different time and / or using a different ultrasonic processing device 110 (see FIG. 4). Preferably, the ultrasonication process 112 (see FIG. 4, FIG. 5) reduces the lateral size of the individual GO sheets 90a (see FIG. 5) to a desired acceptable size that effectively and uniformly covers or coats the individual polymer nanoparticles 80a (see FIG. 5), such as the individual polystyrene (PS) nanoparticles 81a (see FIG. 5). When the GO sheets 90 are in the form of the GO suspension 106 (see FIG. 4, FIG. 5), the ultrasonication process 112 is the preferred method for reducing the lateral size of the GO sheets 90.

[0050] As an alternative to the ultrasonication process 112, the GO sheets 90 (see FIG. 5) may be subjected to a ball milling process 122 (see FIG. 5). For example, the ball milling process 122 of graphite to nano-sized platelets may provide nano-sized GO sheets 90 without the ultrasonication process 112. As used herein, "ball milling process" refers to the use of a ball mill grinder to grind and blend materials for use in a process such as an electrostatic process. A ball mill is a cylindrical device used for grinding or mixing materials, partially filled with the material to be ground and grinding media, which rotates around a horizontal axis. A variety of materials are used as media, including ceramic balls, flint balls, and stainless steel balls. An internal cascade effect reduces the material to a fine powder.

[0051] As further shown in FIG. 4, when the ultrasonicated polymer suspension 100a (see FIG. 5) and the ultrasonicated GO suspension 106a (see FIG. 5) are combined, such as in a mixing vessel 124 containing DI water 102, and heated with a heating device 126, such as a hot plate 126a or another suitable heating device 126, a ultrasonicated mixture 130, such as a physical mixture, is obtained. The ultrasonicated mixture 130 (see FIG. 4, FIG. 5) is heated in an inert atmosphere 132 (see FIG. 5) and undergoes an electrostatic process 140 (see FIG. 4, FIG. 5) or phenomenon, whereby the individual polymer nanoparticles 80a (see FIG. 4, FIG. 5) are uniformly coated with individual graphene oxide (GO) sheets 90a (see FIG. 4, FIG. 5) by electrostatic interaction reaction 142 to obtain the nano-reinforced filler material 150. As used herein, an electrostatic process or phenomenon refers to the force that electric charges exert on each other, involving the accumulation of electric charges on the surfaces of objects due to contact with other surfaces.

[0052] The electrostatic process 140 (see FIG. 4, FIG. 5) causes an electrostatic interaction reaction 142 (see FIG. 5) between the positively charged polymer nanoparticles 80 (see FIG. 4, FIG. 5), such as polystyrene (PS) nanoparticles 81a, and the negatively charged GO sheets 90 (see FIG. 4, FIG. 5), resulting in a nano-reinforced filler material 150 (see FIG. 4, FIG. 5) including polymer-GO core-shell nanoparticles 152 (see FIG. 4, FIG. 5). The electrostatic interaction reaction 142 (see FIG. 5) between the oppositely charged polymer nanoparticles 80 and the GO sheets 90 results in self-assembled polymer-GO core-shell nanoparticles 152b (see FIG. 5). The sheet size 98 (see FIG. 5) of each of the plurality of graphene oxide (GO) sheets 90 is preferably matched with the particle size 88 of each of the plurality of polymer nanoparticles 80 to facilitate uniform and complete coverage or coating of the individual polymer nanoparticles 80a by the individual graphene oxide (GO) sheets 90a.

[0053] Preferably, the sonicated mixture 130 (see FIG. 4, FIG. 5) is heated in an inert atmosphere 132 (see FIG. 5) at an effective temperature 136 (see FIG. 5) in the range of about 70° C. (seventy degrees Celsius) to about 100° C. (one hundred degrees Celsius), at an effective pressure 134 (see FIG. 5) including an atmosphere 135 (see FIG. 5) in the range of about 1 atm (one atmosphere) to about 12 atm (twelve atmospheres), more preferably at an atmosphere 135 (see FIG. 5) of one atm (one atmosphere), and for an effective time 138 (see FIG. 5) in the range of about 3 h (three hours) to about 6 h (six hours). Preferably, the heating of the sonicated mixture 130 (see FIG. 4, FIG. 5) is performed at a mixing speed 133 (see FIG. 5) of about 400 rpm (four hundred revolutions per minute). Self-assembly of the self-assembled polymer-GO core-shell nanoparticles 152b (see FIG. 5) resulting in polymer nanoparticles 80 wrapped or coated with GO sheets 90 preferably takes between about 3 h (three hours) and about 6 h (six hours).

[0054] Preferably, the sonicated mixture 130 (see FIGS. 4 and 5) has a ratio of the plurality of polymeric nanoparticles 80 (see FIGS. 4 and 5) to the plurality of graphene oxide (GO) sheets 90 (see FIGS. 4 and 5) in the range of about 5.58:1.12 (w / w) to about 6.09:0.91 (w / w). More preferably, the sonicated mixture 130 (see FIGS. 4 and 5) has a ratio of the plurality of polymeric nanoparticles 80 (see FIGS. 4 and 5) to the plurality of graphene oxide (GO) sheets 90 (see FIGS. 4 and 5) of about 6:1 (w / w).

[0055] Moreover, preferably, the ratio of polystyrene nanoparticles 81 to GO sheets 90 is 6:1, an optimized ratio such that the smooth surface 96 (see FIG. 5) of each GO sheet 90 is greater than that of polystyrene (PS) nanoparticles 81. Therefore, about 6 parts by weight of polystyrene (PS) nanoparticles 81 are needed per 1 part by weight of GO sheets 90. Thus, 14.3% by weight (weight percent) of GO sheets 90 are needed for 85.7% by weight of PS nanoparticles 81. Thus, the ratio can vary from 13% by weight of GO sheets 90 to 16% by weight of GO sheets to cover the upper and lower limits. This results in a PS nanoparticle to GO sheet range of 1.12-5.58 to 0.91-6.09. Ratios beyond this limit may result in uncoated PS nanoparticles 81 or loss of GO sheets 90 in the sonicated mixture 130 (see FIG. 5).

[0056] As further shown in Figure 4, the nano-reinforced filler material 150 is then washed, dried, and used or incorporated into an epoxy resin system 62 (see Figure 5) for a composite structure 28, such as epoxy composite structure 28a. Drying of the nano-reinforced filler material 150 (see Figures 4, 5) is preferably performed in a hot air oven or other drying device at 45°C (45 degrees Celsius) or another suitable temperature for about 6-12 hours.

[0057] 4, the nano-reinforced filler material 150 includes polymer-GO core-shell nanoparticles 152, each of which includes a polymer core portion 154 and a graphene oxide (GO) shell portion 156. Each GO shell portion 156 (see FIGS. 4, 5) has a smooth surface 96 (see FIG. 5) and completely and sufficiently covers or coats the polymer core portion 154 (see FIGS. 4, 5).

[0058] The nano-reinforced filler material 150 (see FIG. 4, FIG. 5) is preferably for use in an epoxy resin system 62 (see FIG. 5) for a composite structure 28 (see FIG. 4, FIG. 5), such as an epoxy composite structure (see FIG. 4, FIG. 5). As shown in FIG. 5, the epoxy resin system 62 includes an epoxy polymer 63 having a three-dimensional (3D) crosslinked structure 68. As further shown in FIG. 5, the epoxy resin system 62 includes a matrix resin 64, such as in the form of an epoxy resin 66. The epoxy resin (see FIG. 5), when reinforced with the nano-reinforced filler material 150 (see FIG. 5), may include a reinforced epoxy resin 66a (see FIG. 5). The epoxy resin system 62 (see FIG. 5) has mechanical properties 72, such as an epoxy cure temperature 70, a fracture toughness 72a, a strength 72b, and other suitable mechanical properties, and thermal properties 74, such as a thermal stability 74a and other suitable thermal properties.

[0059] The nano-reinforced filler material 150 (see FIG. 5 ) and the nano-reinforced filler material 150a (see FIG. 5 ) are used in an epoxy resin system 62 (see FIG. 5 ) for a composite structure 28, preferably in an air vehicle 10 (see FIG. 1 , FIG. 5 ), such as an aircraft 12 (see FIG. 1 , FIG. 5 ). The nano-reinforced filler material 150 (see FIG. 5 ) and the nano-reinforced filler material 150a (see FIG. 5 ) have an improved interface area 158 (see FIG. 5 ) between the GO sheet 90 and the epoxy resin 66 (see FIG. 5 ) of the epoxy resin system 62 (see FIG. 5 ). The nano-reinforced filler material 150 (see FIG. 5 ) and the nano-reinforced filler material 150a (see FIG. 5 ) further have a uniform coverage 160 and a dense coverage or coating of the plurality of polymer nanoparticles 80 by the GO sheet 90, and the GO sheet 90 has a smooth coverage surface 162 (see FIG. 5 ).

[0060] The nano-reinforced filler material 150 (see FIG. 5) and nano-reinforced filler material 150a (see FIG. 5) are prepared by a DI water 102 (see FIGS. 4, 5) suspension and an ultrasonication process 112 and an electrostatic process 140 that achieve reduced wrinkling 164 (see FIG. 5) of the GO sheets 90 (see FIG. 5), reduced restacking 166 (see FIG. 5) of the GO sheets 90 (see FIG. 5), reduced production time 168 (see FIG. 5), reduced defect structure level 170 (see FIG. 5), and toughened nano-reinforcement 172 by the nano-reinforced filler material 150 (see FIG. 5) and nano-reinforced filler material 150a (see FIG. 5) using a solvent-free process 144 (see FIG. 5).

[0061] 6A, in another embodiment, a method 200 for manufacturing a nano-reinforced filler material 150 (see FIG. 4, FIG. 5) for an epoxy resin system 62 (see FIG. 4) for a composite structure 28 (see FIG. 4, FIG. 5) is provided. FIG. 6A is an illustration of a flow diagram of an exemplary embodiment of the method 200 of the present disclosure.

[0062] As shown in FIG. 6A, the method 200 includes a step 202 of generating or preparing a polymer suspension 100 (see FIG. 4, FIG. 5) including a plurality of polymer nanoparticles 80 (see FIG. 4, FIG. 5) suspended in deionized (DI) water 102 (see FIG. 4, FIG. 5). The generating step 202 further includes a step of generating a polymer suspension 100 including each of the plurality of polymer nanoparticles 80. Preferably, each polymer nanoparticle 80 (see FIG. 4, FIG. 5) has a particle size 88 (see FIG. 5) within a range of about 30 nm (30 nanometers) to about 180 nm (180 nanometers). More preferably, each polymer nanoparticle 80 (see FIG. 4, FIG. 5) has a particle size 88 (see FIG. 5) within a range of about 40 nm (40 nanometers) to about 150 nm (150 nanometers). Most preferably, each polymer nanoparticle 80 has a particle size 88 within a range of about 80 nm (80 nanometers) to about 100 nm (100 nanometers).

[0063] The generating step 202 further includes generating a polymer suspension 100 (see FIGS. 4, 5) including a plurality of polymeric nanoparticles each including a polymer 78 (see FIG. 5) selected from the group consisting of polystyrene 78a (see FIG. 5), poly(methyl methacrylate) (PMMA), poly(butyl acrylate) (PBA), poly(butyl acrylate) (PBA)-poly(methyl methacrylate) (PMMA) (PBA-PMMA), butyl methyl acrylate (BMA), polyvinyl acetate, polyvinyl acetate copolymer, polychloroprene (neoprene), nitrile rubber, acrylic rubber, fluoroelastomer (FKM), polyisoprene, polyvinylidene fluoride, polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), styrene-butadiene, or another suitable polymer.

[0064] As shown in Figure 6A, the method 200 further includes a step 204 of sonicating the polymer suspension 100 (see Figures 4, 5) to obtain a sonicated polymer suspension 100a (see Figures 4, 5). The sonicated polymer suspension 100a (see Figure 5) is a well-dispersed polymer particle suspension. The sonication process 112 (see Figures 4, 5) and the sonication device 110 (see Figures 4, 5) are described in detail above with reference to Figures 4 and 5.

[0065] As shown in FIG. 6A, the method 200 further includes a step 206 of generating or preparing a graphene oxide (GO) suspension 106 (see FIG. 4, FIG. 5) including a plurality of graphene oxide (GO) sheets 90 (see FIG. 4, FIG. 5) suspended in deionized (DI) water 102 (see FIG. 4, FIG. 5). The generating step 206 further includes a step of generating a graphene oxide (GO) suspension 106 including each of the plurality of graphene oxide (GO) sheets 90. The GO suspension 106 includes a plurality of GO sheets 90 suspended in the DI water 102, and may utilize an ultrasonic treatment process 112 (see also FIG. 5), such as a bath sonication process using an ultrasonic treatment device 110 (see also FIG. 5), such as a bath sonication device, to suspend or mix the plurality of GO sheets 90 in the DI water 102.

[0066] As shown in FIG. 6A, the method 200 further includes a step 208 of sonicating the graphene oxide (GO) suspension 106 (see FIG. 4, FIG. 5) to obtain a sonicated graphene oxide (GO) suspension 106a (see FIG. 4, FIG. 5). The sonicated graphene oxide (GO) suspension 106a preferably has a lateral dimension or size of the reduced GO sheets 90. Based on the process parameters (sonication energy and time), the sheet size 98 (see FIG. 5) of the GO sheets 90 may be adjusted or adapted as desired. The sonication process 112 (see FIG. 4, FIG. 5) and the sonication device 110 (see FIG. 4, FIG. 5) are described in detail above with reference to FIG. 4 and FIG. 5.

[0067] Preferably, the GO suspension 106 (see FIG. 5) undergoes an ultrasonic treatment process 112 (see FIG. 5) for an effective time to obtain the desired nano-sized GO sheets 90 for coating the polymer nanoparticles 80, such as polystyrene (PS) nanoparticles 81. When used to generate the GO suspension 106, prior to the ultrasonic treatment process 112, the GO sheets 90 initially have a sheet size 98 (see FIG. 5) in the range of about 500 nm (500 nanometers) to about 5 microns. The GO suspension 106 undergoes an ultrasonic treatment process 112 for an effective time to reduce the sheet size 98 (see FIG. 5) of the GO sheets 90, such as the lateral dimensions of the GO sheets 90. After undergoing an ultrasonic treatment process 112 for an effective time, the GO sheet 90 (see FIGS. 4, 5) has a sheet size 98 (see FIG. 5) that is preferably in the range of about 50 nm (50 nanometers) to about 350 nm (350 nanometers), more preferably in the range of about 150 nm (150 nanometers) to about 300 nm (300 nanometers), and most preferably in the range of about 200 nm (200 nanometers) to about 300 nm (300 nanometers).

[0068] The sheet size 98 (see FIG. 5) of the individual or single GO sheets 90a (see FIG. 5) should be sufficient to completely and fully cover the surface 86 (see FIG. 5) of each individual polymeric nanoparticle 80a (see FIG. 5), with each polymeric nanoparticle 80 having a particle size 88 (see FIG. 5) within the range of about 30 nm (30 nanometers) to about 180 nm (180 nanometers). Each GO sheet 90 preferably has a thickness within the range of about 1 nm (1 nanometer) to about 5 nm (5 nanometers).

[0069] Preferably, the GO suspension 106 undergoes ultrasonication process 112 at ambient or room temperature for a time period ranging from about 1 h (one hour) to about 6 h (six hours). Preferably, during the ultrasonication process 112 of the GO suspension 106, the room temperature is kept below the thermal stability threshold of the GO sheets 90, e.g., below 50° C. (fifty degrees Celsius). In one example, to reduce the lateral dimensions of the GO sheets 90, the GO suspension 106 is first sonicated in ultrasonication process 112 (see FIGS. 4, 5) using an ultrasonicator 110 (see FIGS. 4, 5) in the form of a bath sonicator at room temperature for 2 h (two hours), and then subsequently sonicated in ultrasonication process 112 using the ultrasonicator 110 and ultrasonication probe unit 114 (see FIG. 4) at room temperature for 3 h (three hours).

[0070] As shown in FIG. 6A, the method 200 further includes a step 210 of mixing the sonicated polymer suspension 100a (see FIG. 4, FIG. 5) and the sonicated graphene oxide (GO) suspension 106a (see FIG. 4, FIG. 5) together in a mixing vessel 124 (see FIG. 4) to obtain a sonicated mixture 130 (see FIG. 4, FIG. 5), such as a physical mixture. The mixing step 210 of mixing the sonicated polymer suspension 100a and the sonicated graphene oxide (GO) suspension 106a includes mixing the sonicated polymer suspension 100a and the sonicated graphene oxide (GO) suspension 106a in a ratio of the plurality of polymer nanoparticles 80 to the plurality of graphene oxide (GO) sheets 90 in a range of about 5.58:1.12 (w / w) (polymer nanoparticles to GO sheets by weight) to about 6.09:0.91 (w / w) (polymer nanoparticles 80 to GO sheets by weight). Preferably, the ratio is 6:1 (w / w) (80 polymer nanoparticles to 90 GO sheets by weight).

[0071] As shown in FIG. 6A, the method 200 further includes a step 212 of heating the ultrasonicated mixture 130 (see FIGS. 4 and 5) in an inert atmosphere 132 (see FIG. 5) at an effective temperature 136 (see FIG. 5) and utilizing an electrostatic process 140 (see FIGS. 4 and 5) or electrostatic phenomenon to uniformly coat the individual polymer nanoparticles 80a (see FIG. 5) with individual graphene oxide (GO) sheets 90a (see FIG. 5) via an electrostatic interaction reaction 142 (see FIG. 5) to obtain a nano-reinforced filler material 150 (see FIGS. 4 and 5) comprising polymer-GO core-shell nanoparticles 152 (see FIGS. 4 and 5).

[0072] The heating step 212 further includes heating the sonicated mixture 130 at an effective temperature 136 in the range of about 70° C. to about 100° C. The heating step 212 further includes heating the sonicated mixture 130 at an effective pressure 134 (see FIG. 5) including an atmosphere 135 (see FIG. 5) in the range of about 1 atm to about 12 atm, more preferably at an atmosphere 135 (see FIG. 5) of 1 atm. The heating step 212 further includes heating the sonicated mixture 130 for an effective time 138 in the range of about 3 h to about 6 h. Preferably, the heating of the sonicated mixture 130 (see FIG. 4, FIG. 5) is performed at a mixing speed 133 (see FIG. 5) of about 400 rpm.

[0073] As shown in Figure 6A, the method 200 further includes the step 214 of washing the nano-reinforced filler material 150 (see Figures 4 and 5). As shown in Figure 6A, the method 200 further includes the step 216 of drying the nano-reinforced filler material 150 (see Figures 4 and 5). Drying the nano-reinforced filler material 150 (see Figures 4 and 5) is preferably performed in a hot air oven or other drying device at 45 degrees Celsius or another suitable temperature for about 6-12 hours.

[0074] As shown in Figure 6A, the method 200 further includes the step 218 of using or incorporating a nano-reinforcement filler material 150 (see Figures 4, 5) in an epoxy resin system 62 (see Figure 5) for the composite structure 28 (see Figures 4, 5). The nano-reinforcement filler material 150 (see Figures 4, 5) provides a toughening nano-reinforcement 172 (see Figure 5) to the epoxy resin system 62 (see Figure 5).

[0075] The using step 218 further includes using or incorporating the nano-reinforced filler material 150 in an epoxy resin system 62 for a composite structure 28 , including an epoxy composite structure 28 a within the aircraft 12 .

[0076] 6B, in another embodiment, a method 250 for manufacturing a nano-reinforced filler material 150 for an epoxy resin system 62 for a composite structure 28 is provided that uses a plurality of polystyrene (PS) nanoparticles 81. FIG 6B is an illustration of a flow diagram of another exemplary embodiment of the method 250 of the present disclosure.

[0077] As shown in FIG. 6B, the method 250 includes a step 252 of generating or preparing a polystyrene (PS) suspension 101 including a plurality of polystyrene (PS) nanoparticles 81 suspended in deionized (DI) water 102. Preferably, each PS nanoparticle 81 (see FIG. 5) has a particle size 88 (see FIG. 5) in the range of about 30 nm (30 nanometers) to about 180 nm (180 nanometers). More preferably, each PS nanoparticle 81 (see FIG. 5) has a particle size 88 (see FIG. 5) in the range of about 40 nm (40 nanometers) to about 150 nm (150 nanometers). Most preferably, each PS nanoparticle 80 has a particle size 88 in the range of about 80 nm (80 nanometers) to about 100 nm (100 nanometers). The step 252 of generating a PS suspension 101 of the method 250 further includes a step 252 of generating a PS suspension 101 having a concentration of 12 mg / ml (12 milligrams per milliliter). The PS nanoparticles 81 may be synthesized by emulsion polymerization. The polymerization and synthesis of the PS nanoparticles 81 may take 5h (five hours) to 12h (twelve hours).

[0078] As shown in Figure 6B, the method 250 further includes a step 254 of sonicating the polystyrene suspension 101 to obtain a sonicated polystyrene suspension 101a. The sonication process 112 (see Figures 4, 5) and the sonication device 110 (see Figures 4, 5) are described in detail above with reference to Figures 4 and 5.

[0079] As shown in FIG. 6B, the method 250 further includes a step 256 of generating or preparing a graphene oxide (GO) suspension 106 including a plurality of graphene oxide (GO) sheets 90 suspended in deionized (DI) water 102. The step 256 of generating a GO suspension 106 of the method 250 further includes a step of generating a GO suspension 106 including each of the plurality of graphene oxide (GO) sheets 90. The step 256 of generating a GO suspension 106 of the method 250 further includes a step of generating a GO suspension 106 having a concentration of 1 mg / ml (1 milligram per milliliter). The GO suspension 106 includes a plurality of GO sheets 90 suspended in the DI water 102, and may utilize an ultrasonication process 112 (see also FIG. 5), such as a bath sonication process using an ultrasonic processing device 110 (see also FIG. 5), such as a bath sonication device, to suspend or mix the plurality of GO sheets 90 in the DI water 102.

[0080] As shown in FIG. 6B, the method 250 further includes a step 258 of sonicating the graphene oxide (GO) suspension 106 to obtain a sonicated graphene oxide (GO) suspension 106a. The sonicated graphene oxide (GO) suspension 106a preferably has a lateral dimension or size of the reduced GO sheets 90. Based on the process parameters (sonication energy and time), the sheet size 98 (see FIG. 5) of the GO sheets 90 may be adjusted or adapted as desired. The sonication process 112 (see FIG. 4, FIG. 5) and the sonication device 110 (see FIG. 4, FIG. 5) are described in detail above with reference to FIG. 4 and FIG. 5.

[0081] Preferably, the GO suspension 106 (see FIG. 5) undergoes an ultrasonic treatment process 112 (see FIG. 5) for an effective time to obtain the desired nano-sized GO sheets 90 for coating the polymer nanoparticles 80, such as polystyrene (PS) nanoparticles 81. When used to generate the GO suspension 106, prior to the ultrasonic treatment process 112, the GO sheets 90 initially have a sheet size 98 (see FIG. 5) in the range of about 500 nm (500 nanometers) to about 5 microns. The GO suspension 106 undergoes an ultrasonic treatment process 112 for an effective time to reduce the sheet size 98 (see FIG. 5) of the GO sheets 90, such as the lateral dimensions of the GO sheets 90. After undergoing an ultrasonic treatment process 112 for an effective time, the GO sheet 90 (see FIGS. 4, 5) has a sheet size 98 (see FIG. 5) that is preferably in the range of about 50 nm (50 nanometers) to about 350 nm (350 nanometers), more preferably in the range of about 150 nm (150 nanometers) to about 300 nm (300 nanometers), and most preferably in the range of about 200 nm (200 nanometers) to about 300 nm (300 nanometers).

[0082] The sheet size 98 (see FIG. 5) of the individual or single GO sheets 90a (see FIG. 5) should be sufficient to completely and fully cover the surface 86 (see FIG. 5) of each individual polymeric nanoparticle 80a (see FIG. 5), with each polymeric nanoparticle 80 having a particle size 88 (see FIG. 5) within the range of about 30 nm (30 nanometers) to about 180 nm (180 nanometers). Each GO sheet 90 preferably has a thickness within the range of about 1 nm (1 nanometer) to about 5 nm (5 nanometers).

[0083] Preferably, the GO suspension 106 undergoes ultrasonication process 112 at ambient or room temperature for a time period ranging from about 1 h (one hour) to about 6 h (six hours). Preferably, during the ultrasonication process 112 of the GO suspension 106, the room temperature is kept below the thermal stability threshold of the GO sheets 90, e.g., below 50° C. (fifty degrees Celsius). In one example, to reduce the lateral dimensions of the GO sheets 90, the GO suspension 106 is first sonicated in ultrasonication process 112 (see FIGS. 4, 5) using an ultrasonicator 110 (see FIGS. 4, 5) in the form of a bath sonicator at room temperature for 2 h (two hours), and then subsequently sonicated in ultrasonication process 112 using the ultrasonicator 110 and ultrasonication probe unit 114 (see FIG. 4) at room temperature for 3 h (three hours).

[0084] As shown in Figure 6B, the method 250 further includes a step 260 of mixing the sonicated PS suspension 101a and the sonicated graphene oxide (GO) suspension 106a together in the mixing vessel 124 to obtain a sonicated mixture 130a. The sonication process 112 (see Figures 4, 5) and the sonication device 110 (see Figures 4, 5) are described in detail above with reference to Figures 4 and 5.

[0085] The step 260 of mixing the ultrasonicated PS suspension 101a and the ultrasonicated GO suspension 106a of the method 250 of claim 10 further comprises mixing the ultrasonicated PS suspension 101a and the ultrasonicated GO suspension 106a in a ratio of PS nanoparticles 80 to GO sheets 90 in a range of about 5.58:1.12 (w / w) (by weight, polystyrene (PS) nanoparticles to GO sheets) to about 6.09:0.91 (w / w) (by weight, polystyrene (PS) nanoparticles to GO sheets). Preferably, the ratio of PS nanoparticles 80 to GO sheets 90 is 6:1 (w / w).

[0086] As shown in FIG. 6B , the method 250 further includes a step 262 of heating the ultrasonicated mixture 130a in an inert atmosphere 132 at an effective temperature 136 within a range of about 70° C. (seventy degrees Celsius) to about 100° C. (one hundred degrees Celsius) and utilizing an electrostatic process 140 to uniformly coat the individual polystyrene nanoparticles 81a with individual graphene oxide (GO) sheets 90a through an electrostatic interaction reaction 142 to obtain a nano-reinforced filler material 150a comprising polystyrene-GO core-shell nanoparticles 152a.

[0087] The step 262 of heating the sonicated mixture 130a of the method 250 further includes heating at an effective pressure 134 (see FIG. 5) including an atmosphere 135 (see FIG. 5) in the range of about 1 atm (one atmosphere) to about 12 atm (twelve atmospheres), more preferably at an atmosphere 135 (see FIG. 5) of 1 atm (one atmosphere). The step 262 of heating the sonicated mixture 130a of the method 250 further includes heating for an effective time 138 in the range of about 3h (three hours) to about 6h (six hours). Preferably, the heating of the sonicated mixture 130 (see FIG. 4, FIG. 5) is performed at a mixing speed 133 (see FIG. 5) of about 400 rpm (four hundred revolutions per minute).

[0088] As shown in Figure 6B, the method 250 further includes the step of washing 264 the nano-reinforced filler material 150a. As shown in Figure 6B, the method 250 further includes the step of drying 266 the nano-reinforced filler material 150a. Drying of the nano-reinforced filler material 150 (see Figures 4, 5) is preferably performed in a hot air oven or other drying device at 45°C (45 degrees Celsius) or another suitable temperature.

[0089] 6B, the method 250 includes a step 268 of using or incorporating a nano-reinforcement filler material 150a in the epoxy resin system 62 for the composite structure 28. The nano-reinforcement filler material 150a provides toughening nano-reinforcement 172 to the epoxy resin system 62.

[0090] Working Example In one exemplary embodiment, polymer-graphene oxide (GO) core-shell nanoparticles 152 (see FIGS. 4 and 5) in the form of polystyrene (PS)-GO core-shell nanoparticles 152a (see FIG. 5) were prepared as a result of electrostatic interaction reaction 142 (see FIG. 5) (i.e., electrostatic forces).

[0091] Polystyrene (PS) nanoparticles 81 (see FIG. 5) were synthesized by emulsion polymerization process, i.e., dispersion of PS nanoparticles in deionized (DI) water 102 (see FIG. 4, FIG. 5). The PS nanoparticles 81 having a concentration of 12 mg / ml (12 milligrams per milliliter) suspended in 200 ml (two hundred milliliters) of DI water 102 in a first container 104 (see FIG. 4) in the form of a beaker at room temperature were used to generate the polystyrene (PS) suspension 101 (see FIG. 5). The PS nanoparticles 81 had a particle size 88 (see FIG. 5) of 130 nm (nanometers).

[0092] The PS suspension 101 (see FIG. 5) was then sonicated to obtain an ultrasonicated polystyrene (PS) suspension 101a (see FIG. 5). The PS suspension 101 was sonicated in a first container 104 (see FIG. 4) in an ultrasonic treatment process 112 (see FIG. 4, FIG. 5) using an ultrasonic treatment device 110 (see FIG. 4, FIG. 5) for 15 minutes at room temperature.

[0093] Graphene oxide (GO) sheets 90 (see FIG. 4, FIG. 5) were synthesized by a modified Hummer method, i.e., a chemical process in which potassium permanganate is added to a solution of graphite, sodium nitrate, and sulfuric acid to produce graphite oxide, which is then modified to produce graphene oxide. The synthesized GO sheets were suspended in 200 ml (two hundred milliliters) of deionized (DI) water 102 (see FIG. 4, FIG. 5) in a second container 108 (see FIG. 4), such as another beaker, at room temperature at a concentration of 1 mg / ml (ten milligrams per milliliter) to obtain a graphene oxide (GO) suspension 106 (see FIG. 5).

[0094] The GO suspension 106 (see FIG. 4, FIG. 5) was then sonicated to obtain an ultrasonicated graphene oxide (GO) suspension 106a (see FIG. 4, FIG. 5). To reduce the lateral dimensions of the synthesized GO sheets from an initial size of 500 nm (500 nanometers) to 200 nm (200 nanometers) to 300 nm (300 nanometers), the GO suspension 106 was first sonicated in an ultrasonication process 112 (see FIG. 4, FIG. 5) using an ultrasonication device 110 (see FIG. 4, FIG. 5) in the form of a bath sonicator for 2 h (2 hours) at room temperature, and then thereafter sonicated in an ultrasonication process 112 using an ultrasonication device 110 and an ultrasonication probe unit 114 (see FIG. 4) for 3 h (3 hours) at room temperature. The ultrasonicated GO suspension 106a and the ultrasonicated PS suspension 101a were prepared separately in separate beakers.

[0095] The ultrasonicated PS suspension 101a (see FIG. 5) and the ultrasonicated GO suspension 106a (see FIG. 5) were then mixed in a mixing vessel 124 (see FIG. 4), e.g., a separate beaker, containing DI water 102 (see FIG. 5) at a mixing speed of 400 rpm (400 revolutions per minute) to produce an ultrasonicated mixture 130 (see FIG. 4, FIG. 5). The ultrasonicated mixture 130 had a 1:6 ratio of 1 part GO sheets to 6 parts PS nanoparticles by weight. The ultrasonicated mixture 130 (see FIG. 4, FIG. 5) was mixed and heated in an inert atmosphere in a heating device 126 in the form of a hot plate at 70° C. (70 degrees Celsius) and 1 atm (1 atmosphere) pressure for 6 h (6 hours) to obtain a final product in the form of a nano-reinforced filler material 150a (see FIG. 5) comprising polystyrene (PS)-GO core-shell nanoparticles 152a (see FIG. 5). The final product in the form of nano-reinforced filler material 150a (see FIG. 5) comprising PS-GO core-shell nanoparticles 152a (see FIG. 5) was washed with deionized (DI) water. The final product in the form of nano-reinforced filler material 150a (see FIG. 5) comprising PS-GO core-shell nanoparticles 152a (see FIG. 5) was then dried overnight in a hot air oven at 45° C.

[0096] Characterization. The structure and morphology of PS-GO core-shell nanoparticles 152a (see FIG. 5) were investigated using a FEI Sirion XL30 FEG (field emission electron source) scanning electron microscope (SEM) obtained from FEI, Hillsboro, Oregon, USA. A sonication process, e.g., bath sonication, was used to disperse PS-GO core-shell nanoparticles 152a (see FIG. 5) in DI water for 30 minutes to obtain a PS-GO core-shell nanoparticle suspension. The PS-GO core-shell nanoparticle suspension was drop-cast onto a freshly cleaned silicon substrate. To avoid charge accumulation, the PS-GO core-shell nanoparticle suspension sample was coated with a 10 nm (ten nanometer) thick Au (gold) layer.

[0097] Results. FEI Sirion XL30 FEG Scanning Electron Microscope (SEM) observed PS-GO core-shell nanoparticles 152a (see FIG. 5) as discrete coated individual polystyrene (PS) nanoparticles 81a (see FIG. 5) coated with individual graphene oxide (GO) sheets 90a (see FIG. 5). The average size of the PS-GO core-shell nanoparticles 152a (see FIG. 5), i.e., GO coated PS nanoparticles, was 130 nm (130 nanometers) as measured by dynamic light scattering (DLS) method, which determines the size distribution profile of nanoparticles in suspension. FEI Sirion XL30 FEG-SEM micrographs confirmed that the size of the PS-GO core-shell nanoparticles 152a (see FIG. 5), i.e., GO coated PS nanoparticles, was the same size as obtained by DLS.

[0098] To summarize this example, the electrostatic interaction reaction of oppositely charged GO sheets (negative charge) and PS nanoparticles (positive charge) was utilized to synthesize PS-GO core-shell nanoparticles 152a (see FIG. 5), i.e., GO-coated PS nanoparticles, and to obtain self-assembled PS-GO core-shell nanoparticles. The PS-GO core-shell nanoparticles 152a (see FIG. 5), i.e., GO-coated PS nanoparticles, were discrete and separated, and there were no aggregated GO-coated PS nanoparticles, because the sheet size of the GO sheets used was small, thereby avoiding and eliminating the coating of multiple PS nanoparticles in a single large GO sheet.

[0099] The disclosed embodiments of nano-reinforced filler material 150 (see FIG. 4, FIG. 5), nano-reinforced filler material 150a (see FIG. 4, FIG. 5), method 200 (see FIG. 6A), and method 250 (see FIG. 6B) provide novel organic toughened nano-reinforcement 172 (see FIG. 5) based on polymer nanoparticles 80 (see FIG. 4, FIG. 5), such as polystyrene (PS) nanoparticles 81 (see FIG. 5), smoothly, fully and completely covered or coated with graphene oxide (GO) sheets 90 (see FIG. 4, FIG. 5), having a smooth covered surface 162 (see FIG. 5) with no or reduced pleats or wrinkles of the GO sheets 90. The absence of pleats and agglomeration of the GO sheets 90 allows the full potential of the GO sheets 90 to be utilized. The reduced rugosity 164 (see FIG. 5) and reduced cohesion provide a more efficient mechanical interaction with the epoxy resin 66 (see FIG. 5) of the epoxy resin system 62 (see FIG. 5) and reduce the anisotropy that may be caused by the loosely arranged larger GO sheets. The nano-reinforced filler material 150 (see FIG. 4, FIG. 5) and the nano-reinforced filler material 150a (see FIG. 4, FIG. 5) improve the mechanical properties 72 (see FIG. 5) of the epoxy resin system 62 (see FIG. 5) compared to the known GO sheets, and provide a reduced defect structure level 170 (see FIG. 5) and an improved interfacial area 158 (see FIG. 5) at the interface between the graphene oxide (GO) sheet 90 and the epoxy resin system 62 (see FIG. 5) compared to the known GO sheets. Such enhanced interfacial area 158 and surface area of ​​GO sheet 90 for interaction with epoxy resin 66 of epoxy resin system 62 (see FIG. 5) can lead to reduced manufacturing costs, shortened production time 168 (see FIG. 5), leading to better mechanical properties 72 (see FIG. 5). Furthermore, the smooth coated surface 162 (see FIG. 5) of GO sheet 90 (see FIG. 5) can improve interaction with the epoxy resin system 62 (see FIG. 5) matrix, and the spherical morphology of nano-reinforced filler material 150 (see FIGS. 4, 5) and nano-reinforced filler material 150a (see FIGS. 4, 5) creates an increased surface area for better interaction.

[0100] Furthermore, the nano-reinforced filler material 150 (see FIG. 5) including the polymer-GO core-shell nanoparticles 152 (see FIG. 5) does not exhibit re-stacking or has reduced re-stacking 166 (see FIG. 5) of the GO sheets 90 (see FIG. 5). The smooth coating surface 162 (see FIG. 5) of the GO sheets 90 (see FIG. 5) allows for reduced re-stacking 166 (see FIG. 5) after the formation or synthesis of the GO sheets 90 upon drying of the nano-reinforced filler material 150, which is not avoided in the case of the known planar morphology of graphene sheets, since the known planar morphology of graphene sheets is strongly anchored to the surface of polymer nanoparticles such as PS nanoparticles. The reduced re-stacking 166 (see FIG. 5) of the GO sheets 90 allows for more efficient use of the GO sheets 90 (see FIG. 4, FIG. 5) in the composite structure 28 (see FIG. 1, FIG. 4, FIG. 5).

[0101] Additionally, the disclosed embodiments of nano-reinforced filler material 150 (see FIG. 4, FIG. 5), nano-reinforced filler material 150a (see FIG. 4, FIG. 5), method 200 (see FIG. 6A), and method 250 (see FIG. 6B) eliminate the need for solvents at any stage of polymer nanoparticle 80 production or synthesis, or for dispersion of GO sheets 90 (see FIG. 4, FIG. 5) in composite structure 28 (see FIG. 4, FIG. 5), resulting in a solvent-free process 144 (see FIG. 5). This is useful because the use of solvents can lead to residual solvents that can cause deterioration of the mechanical properties of epoxy resin system 62 (see FIG. 5) and composite structure 28 (see FIG. 5). Eliminating the solvent removal process reduces the production cost of nano-reinforced filler material 150 by eliminating the need for prolonged use of vacuum ovens for energy-consuming solvent removal. Additionally, method 200 (see FIG. 6A) and method 250 (see FIG. 6B) eliminate the need for solvents and therefore the time-consuming step of conditioning epoxy resin 66 after adding nano-reinforced filler material 150, making the manufacturing process of nano-reinforced filler material 150 and nanocomposites more time-efficient. Nano-reinforced filler material 150 (see FIGS. 4, 5) does not require separate surface functionalization.

[0102] Additionally, embodiments of the disclosed nano-reinforced filler material 150 (see FIGS. 4, 5), nano-reinforced filler material 150a (see FIGS. 4, 5), method 200 (see FIG. 6A), and method 250 (see FIG. 6B) allow for reduced production time 168 (see FIG. 5), or significantly reduced duration of the composite production process, for example, from 24h (24 hours) to 7h (7 hours), primarily due to the elimination of the solvent removal step, which is a time-consuming and expensive process that is avoided by the disclosed nano-reinforced filler material 150 (see FIGS. 4, 5), nano-reinforced filler material 150a (see FIGS. 4, 5), method 200 (see FIG. 6A), and method 250 (see FIG. 6B).

[0103] Furthermore, the disclosed embodiments of the nano-reinforced filler material 150 (see FIG. 4, FIG. 5), nano-reinforced filler material 150a (see FIG. 4, FIG. 5), method 200 (see FIG. 6A), and method 250 (see FIG. 6B) provide discrete individual polymer nanoparticles 80a (see FIG. 5) covered or coated by individual GO sheets 90a (see FIG. 5) with a low number of GO-coated polymer nanoparticle agglomerates. The size of the GO sheets 90 used matches the size of the polymer nanoparticles 80, such as PS nanoparticles 81, to facilitate the covering or coating of the individual polymer nanoparticles 80a (see FIG. 5). The smaller size of the polymer nanoparticles 80 (40 nm to 150 nm) compared to known nanoparticles provides a low level of defect structure and improved chemical bonding with the epoxy resin 66 (see FIG. 5), resulting in improved mechanical properties 72 (see FIG. 5) at the same loading level.

[0104] Further, the disclosure includes examples according to the following recited paragraphs: A1. A method for producing a nano-reinforced filler material for an epoxy resin system for composite structures, comprising the steps of: generating a polymer suspension comprising a plurality of polymer nanoparticles suspended in deionized (DI) water; sonicating the polymer suspension to obtain an ultrasonicated polymer suspension; generating a graphene oxide (GO) suspension comprising a plurality of graphene oxide (GO) sheets suspended in deionized (DI) water; sonicating the graphene oxide (GO) suspension to obtain an ultrasonicated graphene oxide (GO) suspension; and mixing the ultrasonicated polymer suspension and the ultrasonicated mixture to obtain an ultrasonicated mixture. The method includes mixing ultrasonicated graphene oxide (GO) suspensions together in a mixing vessel, heating the ultrasonicated mixture in an inert atmosphere at an effective temperature and utilizing an electrostatic process to uniformly coat individual polymer nanoparticles with individual graphene oxide (GO) sheets by an electrostatic interaction reaction to obtain a nano-reinforced filler material comprising polymer-GO core-shell nanoparticles, washing the nano-reinforced filler material, drying the nano-reinforced filler material, and using the nano-reinforced filler material in an epoxy resin system for composite structures to provide toughening nano-reinforcement to the epoxy resin system.

[0105] A2. The method according to A1., wherein the step of generating a polymer suspension includes a step of generating a polymer suspension including a plurality of polymer nanoparticles each having a particle size within a range of about 40 nm (40 nanometers) to about 150 nm (150 nanometers).

[0106] A3. The method of A1., wherein the step of generating a polymer suspension comprises generating a polymer suspension comprising each of a plurality of polymeric nanoparticles comprising a polymer selected from the group consisting of polystyrene, poly(methyl methacrylate) (PMMA), poly(butyl acrylate) (PBA), poly(butyl acrylate)-poly(methyl methacrylate) (PBA-PMMA), butyl methyl acrylate (BMA), polyvinyl acetate, polyvinyl acetate copolymer, polychloroprene (neoprene), nitrile rubber, acrylic rubber, fluoroelastomer (FKM), polyisoprene, polyvinylidene fluoride, polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), and styrene-butadiene.

[0107] A4. The method of A1., wherein the step of generating a graphene oxide (GO) suspension includes the step of generating a graphene oxide (GO) suspension comprising a plurality of graphene oxide (GO) sheets each having a sheet size within a range of about 50 nm (50 nanometers) to about 350 nm (350 nanometers).

[0108] A5. The method of A1., wherein the step of mixing the sonicated polymer suspension and the sonicated graphene oxide (GO) suspension comprises mixing the sonicated polymer suspension and the sonicated graphene oxide (GO) suspension in a ratio of polymer nanoparticles to graphene oxide (GO) sheets of 6:1 (w / w).

[0109] A6. The method of A1., wherein the step of heating the sonicated mixture includes heating at an effective temperature within the range of about 70° C. (seventy degrees Celsius) to about 100° C. (one hundred degrees Celsius).

[0110] A7. The method of A1., wherein the step of heating the sonicated mixture includes heating at an effective pressure including pressures in the range of about 1 atm (1 atmosphere) to about 12 atm (12 atmospheres).

[0111] A8. The method of A1., wherein the step of heating the sonicated mixture comprises heating for an effective time period within the range of about 3h (three hours) to about 6h (six hours).

[0112] A9. The method of A1., wherein using the nano-reinforced filler material includes using the nano-reinforced filler material in an epoxy resin system for composite structures, including epoxy composite structures in aircraft.

[0113] B1. A method for producing a nano-reinforced filler material for an epoxy resin system for composite structures, comprising the steps of: generating a polystyrene (PS) suspension comprising a plurality of polystyrene (PS) nanoparticles suspended in deionized (DI) water, each having a particle size within a range of about 40 nm (40 nanometers) to 150 nm (150 nanometers); sonicating the polystyrene (PS) suspension to obtain an ultrasonicated polystyrene (PS) suspension; generating a graphene oxide (GO) suspension comprising a plurality of graphene oxide (GO) sheets suspended in deionized (DI) water; sonicating the graphene oxide (GO) suspension to obtain an ultrasonicated graphene oxide (GO) suspension; and sonicating the graphene oxide (GO) suspension to obtain an ultrasonicated graphene oxide (GO) suspension. The method includes mixing an ultrasonicated polystyrene suspension and an ultrasonicated graphene oxide (GO) suspension together in a mixing vessel, heating the ultrasonicated mixture in an inert atmosphere at an effective temperature in the range of about 70° C. (seventy degrees Celsius) to about 100° C. (one hundred degrees Celsius), and utilizing an electrostatic process to uniformly coat individual polystyrene (PS) nanoparticles with individual graphene oxide (GO) sheets by an electrostatic interaction reaction to obtain a nano-reinforced filler material comprising polystyrene-GO core-shell nanoparticles, washing the nano-reinforced filler material, drying the nano-reinforced filler material, and using the nano-reinforced filler material in an epoxy resin system for a composite structure to provide a toughening nano-reinforcement to the epoxy resin system.

[0114] B2. The method of B1, wherein the step of generating a graphene oxide (GO) suspension includes generating a graphene oxide (GO) suspension comprising a plurality of graphene oxide (GO) sheets each having a sheet size within a range of about 50 nm (50 nanometers) to about 350 nm (350 nanometers).

[0115] B3. The method of B1., wherein the step of generating a polystyrene suspension includes generating a polystyrene suspension having a concentration of 12 mg / ml (12 milligrams per milliliter), and further wherein the step of generating a graphene oxide (GO) suspension includes generating a graphene oxide (GO) suspension having a concentration of 1 mg / ml (1 milligram per milliliter).

[0116] B4. The method of B1., wherein the step of mixing the sonicated polystyrene (PS) suspension and the sonicated graphene oxide (GO) suspension comprises mixing the sonicated polystyrene (PS) suspension and the sonicated graphene oxide (GO) suspension in a ratio of polystyrene (PS) nanoparticles to graphene oxide (GO) sheets of 6:1 (w / w).

[0117] B5. The method of B1., wherein heating the sonicated mixture comprises heating at an effective pressure, including pressures in the range of about 1 atm (1 atmosphere) to about 12 atm (12 atmospheres).

[0118] B6. The method of B1., wherein the step of heating the sonicated mixture comprises heating for an effective time period within the range of about 3 h (three hours) to about 6 h (six hours).

[0119] C1. A nano-reinforced filler material for an epoxy resin system for composite structures, comprising a plurality of polymer nanoparticles, each having a particle size within a range of about 40 nm (40 nanometers) to about 150 nm (150 nanometers), each having a spherical shape, prepared by suspending in deionized (DI) water and then sonicating via a sonication process to obtain an ultrasonically treated polymer suspension, and a plurality of polymer nanoparticles, each having a particle size within a range of about 50 nm (50 nanometers) to about 350 nm (350 nanometers), each having a spherical shape, prepared by suspending in deionized (DI) water and then sonicating via a sonication process to obtain an ultrasonically treated graphene oxide (GO) suspension, prepared separately from the ultrasonically treated polymer suspension. a plurality of polymer-graphene oxide (GO) core-shell nanoparticles each having a polymer core portion and a graphene oxide (GO) shell portion, the polymer suspension being sonicated and the GO suspension being mixed together to obtain an ultrasonicated mixture, the ultrasonicated mixture being heated in an inert atmosphere and undergoing an electrostatic process, the individual polymer nanoparticles are uniformly coated with individual graphene oxide (GO) sheets through an electrostatic interaction reaction to obtain a nano-reinforced filler material, which is further washed and dried, and used in an epoxy resin system for composite structures.

[0120] C2. The nano-reinforced filler material of C1., wherein each of the plurality of polymeric nanoparticles comprises a polymer selected from the group consisting of polystyrene, poly(methyl methacrylate) (PMMA), poly(butyl acrylate) (PBA), poly(butyl acrylate)-poly(methyl methacrylate) (PBA-PMMA), butyl methyl acrylate (BMA), polyvinyl acetate, polyvinyl acetate copolymer, polychloroprene (neoprene), nitrile rubber, acrylic rubber, fluoroelastomer (FKM), polyisoprene, polyvinylidene fluoride, polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), and styrene-butadiene.

[0121] C3. The nano-reinforced filler material of C1., wherein the sonicated mixture has a ratio of polymer nanoparticles to graphene oxide (GO) sheets of 6:1 (w / w).

[0122] C4. The nano-reinforced filler material of C1., wherein the sheet size of each of the plurality of graphene oxide (GO) sheets is in harmony with the particle size of each of the plurality of polymer nanoparticles to facilitate uniform coverage of each individual graphene oxide (GO) sheet on each individual polymer nanoparticle.

[0123] C5. The nano-reinforced filler material of C1., wherein the sonicated mixture is heated at an effective temperature in the range of about 70° C. (seventy degrees Celsius) to about 100° C. (one hundred degrees Celsius), heated at an effective pressure including an atmosphere in the range of about 1 atm (one atmosphere) to about 12 atm (twelve atmospheres), and heated for an effective time in the range of about 3 h (three hours) to about 6 h (six hours).

[0124] Many modifications and other embodiments of the disclosure will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. The embodiments described herein are intended to be illustrative and not limiting or exhaustive. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. [Explanation of symbols]

[0125] 10 Air Vehicles 12 Aircraft 14. Torso 16 Nose 18 wings 20 Engine 22 tail fin 24 Horizontal stabilizer 26 Vertical stabilizer 28 Composite structure 28a Epoxy Composite Structure 30. Aircraft manufacturing and maintenance inspection methods 32 Specifications and Design 34 Material Procurement 36 Manufacturing of components and subassemblies 38 System Integration 40 Authentication and Delivery 42 in service 44 Maintenance and Inspection 46 Aircraft 48 Aircraft 50 Systems 52 Inside 54 Propulsion System 56 Electrical System 58 Hydraulic System 60 Environmental Systems 62 Epoxy resin 63 Epoxy Polymer 64 Matrix Resin 66 Epoxy Resin 66a Reinforced epoxy resin 68 Three-dimensional crosslinked structure 70 Epoxy curing temperature 72 Mechanical properties 72a Fracture toughness 72b Strength 74 Thermal properties 74a Thermal stability 76 Production System 78 Polymer 78a Polystyrene 80 Polymer Nanoparticles 80a Individual polymer nanoparticles 81 Polystyrene Nanoparticles 81a Individual polystyrene nanoparticles 82 positive charge 84 Spherical shape 86 Surface 88 particle size 90 Graphene oxide sheet 90a Individual graphene oxide sheets 92 negative charge 94 Planar shape 96 Smooth Surface 98 Sheet Size 100 Polymer Suspension 100a Sonicated polymer suspension 101 Polystyrene Suspension 101a Sonicated polystyrene suspension 102 Deionized Water 104 First Container 106 Graphene oxide suspension 106a Ultrasonicated graphene oxide suspension 108 Second Container 110 Ultrasonic processing device 112 Ultrasonic Processing 114 Ultrasonic processing probe part 116 Ultrasonic processing controller part 118 Sonication Platform 120 Acoustic Energy 122 Ball Mill Grinding Process 124 Mixing container 126 Heating device 126a Hot plate 130 Sonicated mixture 130a Sonicated mixture 131 ratio 132 Inert atmosphere 133 Mixing speed 134 Effective Pressure 135 ATM 136 Effective Temperature 138 Validity Period 140 Electrostatic Processes 142 Electrostatic Interaction Reactions 144 Solvent-free Processes 150 Nano-reinforced filler materials 150a Nano-reinforced filler material 152 Polymer-Graphene Oxide Core-Shell Nanoparticles 152a Polystyrene-graphene oxide core-shell nanoparticles 152b Self-assembled polymer-graphene oxide core-shell nanoparticles 154 Polymer core 154a Polystyrene core 156 Graphene oxide shell 158 Improved interface area 160 Uniform Coverage 162 Smooth coated surface 164 Reduced pleats 166 Reduced Restack 168 Reduced production time 170 Reduced defect structure level 172 Toughened Nano-Reinforcement 200 ways 250 methods

Claims

1. A nano-reinforced filler material (150) for an epoxy resin system (62) for a composite structure (28), comprising: A plurality of polymer-graphene oxide (GO) core-shell nanoparticles (152), each of which comprises a polymer core portion (154) and a graphene oxide (GO) shell portion (156). a plurality of polymeric nanoparticles (80) each having a particle size (88) within the range of 40 nm (40 nanometers) to 150 nm (150 nanometers), each having a spherical shape (84); a plurality of graphene oxide (GO) sheets (90) each having a lateral dimension within a range of 50 nm (50 nanometers) to 350 nm (350 nanometers), each having a planar shape (94); Including, The surface of each polymer nanoparticle (80a) is completely coated with each graphene oxide (GO) sheet (90a) by electrostatic interaction reaction (142), and used in the epoxy resin system (62) for the composite structure (28). Multiple polymer-graphene oxide (GO) core-shell nanoparticles (152) A nano-reinforced filler material (150) comprising:

2. 2. The nano-reinforced filler material of claim 1, wherein each of the plurality of polymeric nanoparticles comprises a polymer selected from the group consisting of polystyrene, poly(methyl methacrylate) (PMMA), poly(butyl acrylate) (PBA), poly(butyl acrylate)-poly(methyl methacrylate) (PBA-PMMA), butyl methyl acrylate (BMA), polyvinyl acetate, polyvinyl acetate copolymers, polychloroprene (neoprene), nitrile rubber, acrylic rubber, fluoroelastomers (FKM), polyisoprene, polyvinylidene fluoride, polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), and styrene-butadiene.

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