Composite layers with exposed reinforcement

A composite structure comprising a matrix and a reinforcement. The matrix comprises a substantially nonconductive material. The reinforcement comprises a conductive material. The reinforcement is located within the matrix to form a composite layer. A portion of the reinforcement is exposed at a surface of the composite layer such that electrical conductivity of the composite layer is increased in a direction substantially perpendicular to the composite layer.

BACKGROUND INFORMATION

The present disclosure relates generally to composite layers and, in particular, to a method and apparatus for conducting electrical energy using composite layers.

Composite materials may be used to form structures for different types of objects. As used herein, a “composite material”, also referred to as a “composite”, comprises two or more different types of materials. These materials have different physical and/or chemical properties which may remain separate and distinct within the composite material.

A structure formed using one or more composite materials is referred to as a composite structure. Composite materials may be used to form composite structures for objects, such as, for example, without limitation, an aerospace vehicle, an unmanned aerial vehicle (UAV), a space shuttle, a watercraft, a land vehicle, an automobile, a building, an electromechanical device, armor, and other suitable types of objects.

In one illustrative example, one or more composite materials may be used to form a composite structure for use in an aircraft. The composite structure may be, for example, a skin panel for a wing or fuselage of the aircraft. A structure formed using composite materials may have an increased strength as compared to the same structure formed using other materials, such as, for example, metal. Further, a structure formed using composite materials may have a reduced weight as compared to the same structure formed using these other materials.

However, in some cases, a composite structure may not provide a desired level of electrical conductivity. For example, a composite structure may be unable to conduct the electrical energy induced in the composite structure by an electromagnetic event that occurs around the composite structure. The electromagnetic event may be, for example, a lightning strike. The electrical energy generated by the electromagnetic event may take the form of electrical currents and/or electromagnetic forces.

As one illustrative example, some currently available composite skin panels for the fuselage of an aircraft are unable to provide a desired number of conductive pathways for the electrical currents and/or electromagnetic forces generated when lightning contacts the fuselage of the aircraft. These electrical currents and/or electromagnetic forces try to find the path of least resistance. In some cases, a portion of the path of least resistance passes through a matrix in a composite skin panel where little conductive material is present. The electrical currents and/or electromagnetic forces cause undesired inconsistencies in the matrix as the electrical currents and/or electromagnetic forces travel along this pathway.

Further, these electrical currents and/or electromagnetic forces may affect the composite structure and/or other components in the aircraft in an undesired manner, while trying to find the path of least resistance. For example, the electrical currents and/or electromagnetic forces may cause the composite structure and/or other components in the aircraft to overheat beyond selected tolerances. The other components that may be affected include, for example, without limitation, the composite skin panel, wiring, hinges, electrical systems, and/or other suitable components in the aircraft. Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above as well as possibly other issues.

SUMMARY

In one illustrative embodiment, an apparatus comprises a matrix and a reinforcement. The matrix comprises a substantially nonconductive material. The reinforcement comprises a conductive material. The reinforcement is located within the matrix to form a composite layer. A portion of the reinforcement is exposed at a surface of the composite layer such that electrical conductivity of the composite layer is increased in a direction substantially perpendicular to the composite layer.

In another illustrative embodiment, a composite structure comprises a plurality of composite layers. A composite layer in the plurality of composite layers comprises a matrix and a reinforcement. The matrix comprises a substantially nonconductive material. The reinforcement comprises a conductive material and is located within the matrix. A portion of the reinforcement is exposed at a surface of the composite layer such that electrical conductivity of the composite layer is increased in a direction substantially perpendicular to the composite layer. The portion of the reinforcement exposed at the surface of the composite layer electrically connects the composite layer to another composite layer in the plurality of composite layers such that the composite structure has a desired level of electrical conductivity in a direction substantially parallel to a z-axis for the composite structure.

In yet another illustrative embodiment, a method for conducting electrical energy using a composite structure is present. An object comprising the composite structure is operated. Electrical energy is induced in the composite structure in response to an electromagnetic event that occurs during operation of the object. The composite structure comprises a plurality of composite layers. A composite layer in the plurality of composite layers comprises a matrix and a reinforcement. The matrix comprises a substantially nonconductive material. The reinforcement comprises a conductive material and is located within the matrix. A portion of the reinforcement is exposed at a surface of the composite layer. The electrical energy induced in the composite structure in response to the electromagnetic event is conducted within the composite structure using the portion of the reinforcement exposed at the surface of the composite layer in the plurality of composite layers such that electrical conductivity of the composite structure is increased in a direction substantially parallel to a z-axis for the composite structure.

In yet another illustrative embodiment, a method for forming a composite layer is present. A reinforcement is embedded in a matrix to form the composite layer. The matrix comprises a substantially nonconductive material. The reinforcement comprises a conductive material. A portion of the reinforcement is exposed at a selected portion of a surface of the composite layer such that electrical conductivity of the composite layer is increased in a direction substantially perpendicular to the composite layer.

DETAILED DESCRIPTION

The different illustrative embodiments recognize and take into account different considerations. For example, the different illustrative embodiments recognize and take into account that some currently available composite structures do not have a desired level of electrical conductivity. In particular, these composite structures may not provide a desired level of electrical conductivity in a direction substantially perpendicular to these composite structures. The direction substantially perpendicular to these composite structures may be a direction substantially parallel to a z-axis for these composite structures.

As one illustrative example, a composite structure may be unable to conduct the electrical currents and/or electromagnetic forces induced in a composite structure in a direction substantially parallel to a z-axis for the composite structure. These electrical currents and/or electromagnetic forces may be induced in the composite structure in response to an electromagnetic event that occurs in an environment around the composite structure. The electromagnetic event is any event that generates electrical currents, electromagnetic forces, and/or produces an electrical field. For example, the electromagnetic event may be a lightning strike, a short circuit, an overloaded circuit, mismatched loads in a circuit, an electrical field, or some other type of electromagnetic event.

The different illustrative embodiments recognize and take into account that a composite structure having an increased electrical conductivity in the direction substantially perpendicular to the composite structure may be desirable for providing a desired level of protection from undesired effects caused by electromagnetic events. These undesired effects include, for example, without limitation, delamination, cracks, tearing, wear, and/or other types of undesired effects with respect to the composite structure.

For example, the different illustrative embodiments recognize and take into account that an increased electrical conductivity with respect to a z-axis for a composite structure may be useful for dissipating the electrical currents and/or electromagnetic forces generated by a lightning strike contacting the composite structure. Further, the different illustrative embodiments recognize and take into account that increasing the electrical conductivity of a composite structure without increasing the weight and/or reducing the strength of the composite structure outside of selected tolerances may be desirable.

Thus, the different illustrative embodiments provide a method and apparatus for conducting electrical energy. In one illustrative embodiment, an apparatus comprises a matrix and a reinforcement. The matrix comprises a substantially nonconductive material. The reinforcement comprises a conductive material. The reinforcement is located within the matrix to form a composite layer. A portion of the reinforcement is exposed at a surface of the composite layer such that electrical conductivity of the composite layer is increased in a direction substantially perpendicular to the composite layer.

In another illustrative embodiment, a composite structure comprises a plurality of composite layers. Each composite layer in the plurality of composite layers comprises a matrix and a reinforcement. The matrix comprises a substantially nonconductive material. The reinforcement comprises a conductive material and is located within the matrix. A first portion of the reinforcement is exposed at a first surface of each composite layer, and a second portion of the reinforcement is exposed at a second surface of each composite layer such that the electrical conductivity of each composite layer is increased in a direction substantially perpendicular to the composite layer. The first portion and the second portion of the reinforcement in each composite layer in the plurality of composite layers is configured to electrically connect the plurality of composite layers to each other such that the composite structure has a desired level of electrical conductivity in a direction substantially perpendicular to the composite structure.

With reference now to the figures and, in particular, with reference now toFIG. 1, an illustration of a composite structure in the form of a block diagram is depicted in accordance with an illustrative embodiment. Composite structure100is configured for use in an object, such as, for example, object102.

Object102may take a number of different forms. For example, without limitation, object102may be an aerospace vehicle, an unmanned aerial vehicle (UAV), a helicopter, a satellite, a space shuttle, a watercraft, a train, a land vehicle, an automobile, a building, an electromechanical device, armor, or some other suitable type of object. As one illustrative example, when object102takes the form of an aerospace vehicle, composite structure100may be a skin panel for the aerospace vehicle.

In these illustrative examples, composite structure100comprises composite material104. Composite material104takes the form of one or more composite layers, such as composite layer106. For example, in one illustrative example, composite layer106is the only layer of composite material104in composite material104.

In other illustrative examples, composite layer106may be one composite layer in a plurality of composite layers, such as plurality of composite layers108. As used herein, a “plurality of” means two or more. For example, plurality of composite layers108means two or more composite layers. In some illustrative examples, a composite layer may also be referred to as a composite ply. Plurality of composite layers108may include two, three, four, 10, 20, 50, 100, or some other number of composite layers, depending on the implementation.

As depicted, composite layer106comprises matrix110and reinforcement112. Reinforcement112is located within matrix110to form composite layer106. In particular, matrix110is a monolithic material into which reinforcement112is embedded in these illustrative examples. Further, matrix110is substantially continuous. In other words, a path may be present from any point in matrix110to any other point in matrix110. Matrix110provides support for reinforcement112. Matrix110is sometimes referred to as a binder for reinforcement112.

In these illustrative examples, matrix110comprises substantially nonconductive material113. Substantially nonconductive material113may comprise any number of materials that are substantially nonconductive. In particular, substantially nonconductive material113may not have a desired level of conductivity. Further, substantially nonconductive material113may be selected to support reinforcement112.

For example, without limitation, matrix110may comprise at least one of a polymer, a plastic, a ceramic material, and some other suitable type of material. In particular, matrix110may comprise one or more polymers selected from at least one of, for example, without limitation, a resin, polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, a polyether ether ketone (PEEK), polypropylene, a polyester thermosetting plastic, and some other suitable type of polymer material that is substantially nonconductive.

Reinforcement112comprises one or more materials embedded in matrix110. Reinforcement112is configured to provide structural support and strength for composite layer106. In some illustrative examples, reinforcement112is used to introduce desirable properties into composite layer106. For example, reinforcement112may be used to change the physical properties of composite layer106. These physical properties may include, for example, without limitation, electrical conductivity, wear resistance, a friction coefficient, thermal conductivity, and other suitable physical properties.

In these illustrative examples, reinforcement112is comprised of a number of materials selected from at least one of carbon, glass, silicon carbide, boron, a metallic material, a ceramic material, a metal alloy, a synthetic material, a para-aramid synthetic material, and some other suitable type of material. These materials may take the form of at least one of fibers, flakes, particles, and fillers within reinforcement112. Depending on the arrangement of these fibers, flakes, particles, and/or fillers in reinforcement112, reinforcement112may be continuous or discontinuous.

In these illustrative examples, reinforcement112comprises conductive material114. Conductive material114may be any material configured to conduct an electrical current. Conductive material114may be carbon in these illustrative examples. Of course, in other illustrative examples, conductive material114may comprise a number of other conductive materials in addition to and/or in place of carbon. Further, in some cases, reinforcement112may comprise other materials in addition to conductive material114.

In one illustrative example, composite structure100may be a carbon fiber reinforced plastic (CFRP). Reinforcement112in each composite layer in the carbon fiber reinforced plastic comprises carbon fibers, while matrix110comprises a plastic material.

As depicted, composite layer106has first surface116and second surface118. First portion120of reinforcement112may be exposed at first surface116. Further, second portion121of reinforcement112may be exposed at second surface118.

As used herein, a portion of reinforcement112is “exposed” when that portion is in contact with the environment around reinforcement112. For example, when first portion120of reinforcement112is exposed at first surface116, some other component may come into contact with first portion120of reinforcement112at first surface116.

In one illustrative example, reinforcement112comprises plurality of fibers132. In this example, first portion120and second portion121of plurality of fibers132may each include a group of fibers in plurality of fibers132. This group of fibers may include fibrils. In some cases, a fiber in plurality of fibers132that is exposed at first surface116may also be exposed at second surface118.

First portion120and/or second portion121of reinforcement112may be exposed at first surface116and/or second surface118, respectively, using a number of different processes. For example, a mechanical process, a chemical process, a laser surface ablation process, an etching process, a threading process, a stitching process, an abrasion process, a sanding process, a raking process, and/or some other suitable type of process may be used to expose first portion120of reinforcement112at first surface116and/or second portion121of reinforcement112at second surface118.

As one illustrative example, first portion120of plurality of fibers132is exposed at first surface116of composite layer106by mechanically wearing away a portion of first surface116to expose a portion of plurality of fibers132near first surface116. The portion of first surface116that is worn away may be a portion of matrix110at first surface116. First surface116may be mechanically worn away using, for example, abrasion, mechanical raking, or some other suitable type of process for wearing away and/or roughening a surface.

In another illustrative example, first portion120is exposed at first surface116by applying a chemical to first surface116of composite layer106. The chemical may chemically remove or dissolve away a portion of first surface116to expose first portion120of reinforcement112. In particular, this chemical process may chemically remove or dissolve away a portion of matrix110at first surface116to expose first portion120of reinforcement112.

In some illustrative examples, a laser is used to ablate or remove a portion of first surface116to expose first portion120of reinforcement112. In still other illustrative examples, one or more portions of first surface116are etched away to expose first portion120of reinforcement112.

Additionally, in some cases, a group of fibers in plurality of fibers132for reinforcement112is threaded through matrix110such that a first portion of the group of fibers is exposed at first surface116while a second portion of the group of fibers remains substantially embedded in matrix110in composite layer106. The different processes described for exposing first portion120of reinforcement112at first surface116of composite layer106may be implemented in a similar manner to expose second portion121of reinforcement112at second surface118of composite layer106.

First portion120of reinforcement112exposed at first surface116increases electrical conductivity122of composite layer106in a direction substantially perpendicular to composite layer106. Further, second portion121of reinforcement112exposed at second surface118of composite layer106increases electrical conductivity122of composite layer106in the direction substantially perpendicular to composite layer106.

Electrical conductivity122is a measure of the ability of composite layer106to conduct an electrical current. Electrical conductivity122of composite layer106may be increased at first surface116and second surface118of composite layer106with respect to electrical currents124that may flow into and/or out of composite layer106at first surface116and second surface118.

Electrical currents124may flow into composite layer106from any direction relative to composite layer106. Conductive material114of reinforcement112allows electrical currents124that flow into composite layer106from any direction relative to composite layer106to be conducted within composite layer106. Further, electrical currents124may flow out of composite layer106in any direction relative to composite layer106.

In some illustrative examples, first portion120of reinforcement112may be exposed at a selected portion of first surface116. The portion of first surface116at which first portion120of reinforcement112is exposed may be selected to increase electrical conductivity122of composite layer106in the direction substantially perpendicular to composite layer106at this selected portion of first surface116and not at other portions of first surface116.

Similarly, second portion121of reinforcement112may be exposed at a selected portion of second surface118. The portion of second surface118at which second portion121of reinforcement112is exposed may be selected to increase electrical conductivity122of composite layer106in the direction substantially perpendicular to composite layer106at this selected portion of second surface118and not at other portions of first surface116.

The selected portions of first surface116and second surface118at which reinforcement112is exposed may comprise one portion of each of these surfaces or discontinuous portions of each of these surfaces. In some cases, the selected portion for at least one of first surface116and second surface118may form a pattern on the surface.

Of course, in other cases, the selected portion for at least one of first surface116and second surface118may be substantially the entire surface. In this manner, electrical conductivity122of composite layer106in the direction substantially perpendicular to composite layer106may be specifically tailored based on, for example, without limitation, a policy, certain requirements, and/or the particular usage for composite structure100.

When composite structure100takes the form of composite laminate107with plurality of composite layers108, a first portion and/or a second portion of the reinforcement in each composite layer in plurality of composite layers108may be exposed at the first surface and/or second surface, respectively, of each composite layer. The portions of reinforcement exposed at the first surface and/or the second surface of each composite layer in plurality of composite layers108electrically connect plurality of composite layers108to each other.

With plurality of composite layers108electrically connected to each other, electrical currents124are allowed to flow between the different composite layers in plurality of composite layers108. In particular, the portions of reinforcement exposed at the first surface and/or the second surface of each composite layer in plurality of composite layers108increase the ability of composite laminate107to conduct electrical currents124in a direction substantially perpendicular to composite laminate107. Consequently, composite laminate107has an increased electrical conductivity122with respect to the direction substantially perpendicular to composite laminate107.

In this manner, the exposed portions of reinforcement for the different composite layers in plurality of composite layers108may provide desired level of electrical conductivity135for composite laminate107in the direction substantially perpendicular to composite laminate107. Further, with the portions of reinforcement exposed at the first surface and/or second surface of each composite layer in plurality of composite layers108, additional layers between the different composite layers in plurality of composite layers108may not be needed to provide desired level of electrical conductivity135.

Depending on the implementation, not all of the composite layers in plurality of composite layers108may have reinforcement exposed at both surfaces of the composite layers. In some cases, only a portion of the composite layers in plurality of composite layers108has reinforcement exposed at both surfaces. Further, in other examples, a portion of the composite layers in plurality of composite layers108has reinforcement exposed at only one surface.

Any reinforcement exposed at the surface of a composite layer in plurality of composite layers108may increase the electrical conductivity of composite laminate107in the direction substantially perpendicular to composite laminate107. Further, depending on the type and/or configuration of the reinforcement in each of plurality of composite layers108, an increased electrical conductivity of composite laminate107in the direction substantially perpendicular to composite laminate107may increase the electrical conductivity of composite laminate107in any number of other directions with respect to composite laminate107.

In these illustrative examples, the direction that is substantially perpendicular to composite laminate107may be a direction substantially parallel to z-axis126for composite laminate107. Z-axis126is an axis that is substantially perpendicular to x-axis128and y-axis130for composite laminate107. In these illustrative examples, x-axis128and y-axis130lie along the plane through composite laminate107.

In one illustrative example, composite layer106may be a first composite layer in plurality of composite layers108. Matrix110and reinforcement112may be a first matrix and a first reinforcement, respectively. Further, electrical conductivity122for composite layer106may be a first electrical conductivity.

Plurality of composite layers108may also include second composite layer134comprising second matrix136and second reinforcement138. Second reinforcement138may be embedded in second matrix136. In this illustrative example, first portion140of second reinforcement138may be exposed at first surface142of second composite layer134such that second electrical conductivity144of second composite layer134is increased in the direction substantially perpendicular to second composite layer134.

Further, second portion146of second reinforcement138may be exposed at second surface148of second composite layer134such that second electrical conductivity144of second composite layer134is increased in the direction substantially perpendicular to second composite layer134. In these illustrative examples, first portion140and/or second portion146of second reinforcement138may be exposed at first surface142and/or second surface148, respectively, using any of the processes described above for exposing first portion120and second portion121of reinforcement112.

As depicted, second composite layer134may be positioned relative to composite layer106. In particular, second composite layer134may be laid up over composite layer106. When second composite layer134is positioned relative to composite layer106, first portion120of reinforcement112may contact second portion146of second reinforcement138at interface145between first surface116of composite layer106and second surface148of second composite layer134.

This contact may electrically connect composite layer106to second composite layer134at interface145. In these illustrative examples, this contact increases the electrical conductivity of plurality of composite layers108in the direction substantially parallel to z-axis126to provide desired level of electrical conductivity135for plurality of composite layers108.

In some cases, first portion120of reinforcement112may be near second portion146of second reinforcement138when second composite layer134is positioned relative to composite layer106but may not come into contact with second portion146. First portion120may be near enough to second portion146to allow electrical currents124to flow between first portion120and second portion146. In other words, in some illustrative examples, first portion120may not need to be in direct contact with second portion146to allow electrical currents124to flow between first portion120and second portion146.

For example, electrical energy149may be induced in composite structure100in response to electromagnetic event152. Electromagnetic event152may be, for example, without limitation, a lightning strike, a short circuit, an overloaded circuit, mismatched loads in a circuit, an electrical field near composite structure100, or some other suitable type of event that generates number of electrical currents150.

Electrical energy149is induced in composite structure100in the form of number of electrical currents150and/or electromagnetic forces151. In these illustrative examples, electromagnetic event152induces electrical energy149in composite structure100by generating number of electrical currents150that flow into composite structure100, inducing an electrical field within composite structure100, and/or inducing electrical energy149in composite structure100in some other suitable manner.

In one illustrative example, electromagnetic event152occurs above first surface142of second composite layer134. For example, lightning contacts first surface142of second composite layer134. In particular, lightning contacts first portion140of second reinforcement138when lightning contacts first surface142. This lightning strike generates number of electrical currents150that are conducted into second composite layer134.

Number of electrical currents150flow into second composite layer134through first portion140of second reinforcement138at first surface142of second composite layer134. Number of electrical currents150flow through second composite layer134in the direction substantially parallel to z-axis126.

Further, number of electrical currents150flow out of second composite layer134through second portion146of second reinforcement138at second surface148of second composite layer134and into composite layer106through first portion120of reinforcement112at first surface116of composite layer106. Number of electrical currents150flow through composite layer106in the direction substantially parallel to z-axis126. In some cases, number of electrical currents150flow out of composite layer106though second portion121of reinforcement112and into some other composite layer under composite layer106in composite structure100.

Further, in addition to number of electrical currents150flowing in the direction substantially parallel to z-axis126, number of electrical currents150may also be conducted within composite layer106and second composite layer134in any number of other directions relative to these composite layers. In some cases, increased electrical conductivity122and second electrical conductivity144in the direction substantially parallel to z-axis126increase electrical conductivity122and second electrical conductivity144in other directions.

In this manner, the physical proximity of first portion140and second portion146of second reinforcement138in second composite layer134and first portion120and second portion121of reinforcement112in composite layer106may provide conductive pathways for number of electrical currents150. These conductive pathways provide desired level of electrical conductivity135for composite structure100. Desired level of electrical conductivity135may be a higher electrical conductivity in the direction substantially perpendicular to composite structure100as compared to currently available composite structures.

For example, in some cases, plurality of composite layers108may include other composite layers in addition to composite layer106and second composite layer134. Further, in some illustrative examples, composite layer106may include other materials in addition to matrix110and reinforcement112.

In other illustrative examples, additional conductive material may be applied between composite layers in plurality of composite layers108. This additional conductive material may be used to increase the electrical conductivity of composite structure100in the direction substantially parallel to z-axis126. The conductive material applied between the composite layers may include, for example, without limitation, metal particles, chopped carbon fibers, carbon flakes, carbon particles, and/or other suitable types of conductive material.

With reference now toFIG. 2, an illustration of a partially-exposed isometric view of a composite layer is depicted in accordance with an illustrative embodiment. In this illustrative example, composite layer200is an example of one implementation for composite layer106inFIG. 1. As depicted, composite layer200comprises matrix202and reinforcement204. Reinforcement204comprises plurality of fibers206. As depicted, plurality of fibers206may be arranged in the form of mesh208.

Further, composite layer200has first surface210and second surface212. In this illustrative example, portions of reinforcement204have not yet been exposed at first surface210and second surface212. In particular, fibrils and/or fibers in plurality of fibers206are not in contact with first surface210or second surface212in this depicted example.

Composite layer200inFIG. 2may be an example of a composite layer before fibers in plurality of fibers206have been exposed. A portion of plurality of fibers206near first surface210and a portion of plurality of fibers206near second surface212may be exposed using, for example, without limitation, a mechanical process, a laser process, a chemical process, or some other suitable type of process.

With reference now toFIG. 3, an illustration of a partially-exposed isometric view of a composite layer with portions of reinforcement exposed at surfaces of the composite layer is depicted in accordance with an illustrative embodiment. In this illustrative example, first surface210and second surface212of composite layer200have been roughened such that first portion300of reinforcement204is exposed at first surface210, and second portion302of reinforcement204is exposed at second surface212.

First surface210and second surface212may have been roughened using a number of different processes as described inFIG. 1. For example, first surface210and second surface212may have been roughened using at least one of an abrasion process, a raking process, or some other suitable type of mechanical process.

As depicted, first portion300and second portion302may include broken ends of fibers in plurality of fibers206in reinforcement204, loops of fibers in plurality of fibers206, and other portions or pieces of fibers in plurality of fibers206. First portion300of reinforcement204exposed at first surface210and second portion302of reinforcement204exposed at second surface212increase the electrical conductivity of composite layer200in a direction substantially parallel to z-axis304.

With reference now toFIG. 4, an illustration of a cross-sectional side view of a composite layer with portions of reinforcement exposed at surfaces of the composite layer is depicted in accordance with an illustrative embodiment. In this illustrative example, a cross-sectional side view of composite layer200taken along lines4-4inFIG. 3is depicted.

Turning now toFIG. 5, an illustration of a top view of a composite layer with portions of reinforcement exposed at surfaces of the composite layer is depicted in accordance with an illustrative embodiment. In this illustrative example, a top view of composite layer200fromFIG. 3is depicted.

With reference now toFIG. 6, an illustration of a partially-exposed isometric view of a composite layer with portions of reinforcement exposed at surfaces of the composite layer is depicted in accordance with an illustrative embodiment. In this illustrative example, composite layer600is an example of one implementation for composite layer106inFIG. 1.

As depicted, composite layer600comprises matrix602and reinforcement604. Reinforcement604comprises plurality of fibers606. As depicted, plurality of fibers606is not arranged in a mesh, such as mesh208inFIGS. 2-4. Instead, plurality of fibers606may have a random arrangement within reinforcement604.

Further, composite layer600has first surface610and second surface612. In this illustrative example, a portion of first surface610and a portion of second surface612have been removed such that first portion614of reinforcement604is exposed at first surface610and second portion616of reinforcement604is exposed at second surface612.

First portion614and second portion616may be exposed using a number of different processes. For example, a portion of first surface610and a portion of second surface612may have been removed using a chemical process, a laser ablation process, or some other suitable type of process to expose first portion614and second portion616.

As depicted, first portion614and second portion616may include broken ends of fibers in plurality of fibers606in reinforcement604, loops of fibers in plurality of fibers606, and other portions or pieces of fibers in plurality of fibers606. First portion614of reinforcement604exposed at first surface610and second portion616of reinforcement604exposed at second surface612increase the electrical conductivity of composite layer600in a direction substantially parallel to z-axis618.

With reference now toFIG. 7, an illustration of a cross-sectional side view of a composite layer with portions of reinforcement exposed at surfaces of the composite layer is depicted in accordance with an illustrative embodiment. In this illustrative example, a cross-sectional side view of composite layer600taken along lines7-7inFIG. 6is depicted.

With reference now toFIG. 8, an illustration of a partially-exposed isometric view of a composite structure comprising a plurality of composite layers is depicted in accordance with an illustrative embodiment. In this illustrative example, composite structure800may be a skin panel for an aircraft. As depicted, composite structure800comprises plurality of composite layers802. Consequently, composite structure800may be referred to as a composite laminate.

Each composite layer in plurality of composite layers802may be implemented using composite layer200fromFIG. 3. In this manner, conductive pathways may be formed by contact between the exposed portions of reinforcement at the surfaces of the different composite layers in composite structure800.

These exposed portions of reinforcement at the surfaces of the different composite layers in composite structure800increase the electrical conductivity of composite structure800in a direction substantially perpendicular to composite structure800. This direction may be substantially parallel to z-axis804for composite structure800.

The conductive pathways provided by the exposed portions of reinforcement at the surfaces of the different composite layers in composite structure800may allow a number of electrical currents and/or electromagnetic forces generated by an electromagnetic event to be conducted within composite structure800. The electromagnetic event may be, for example, without limitation, a lightning strike.

When lightning strikes composite structure800, the lightning may generate electrical currents that are dispersed through composite structure800in a direction substantially parallel to z-axis804. For example, when lightning strikes any surface of composite structure800, electrical currents may flow into composite structure800. These electrical currents may be conducted within composite structure800through the reinforcement in each of plurality of composite layers802.

As one specific example, when lightning strikes surface806of composite structure800, electrical currents may flow through plurality of composite layers802in the direction of arrow808. In particular, plurality of composite layers802may conduct these electrical currents in the direction of arrow808to disperse these electrical currents.

With reference now toFIG. 9, an illustration of a cross-sectional side view of a composite structure comprising a plurality of composite layers is depicted in accordance with an illustrative embodiment. InFIG. 9, a cross-sectional side view of composite structure800taken along lines9-9inFIG. 8is depicted.

The different components shown inFIGS. 2-9may be combined with components inFIG. 1, used with components inFIG. 1, or a combination of the two. Additionally, some of the components in these figures may be illustrative examples of how components shown in block form inFIG. 1can be implemented as physical structures.

With reference now toFIG. 10, an illustration of an aircraft comprising composite skin panels is depicted in accordance with an illustrative embodiment. In this illustrative example, aircraft1000has wing1002and wing1004attached to body1006. Aircraft1000includes engine1008attached to wing1002and engine1010attached to wing1004. Body1006has tail section1012. Horizontal stabilizer1014, horizontal stabilizer1016, and vertical stabilizer1018are attached to tail section1012of body1006.

Aircraft1000is an example of one implementation for object102inFIG. 1. Body1006of aircraft1000may have plurality of composite skin panels1020. Each composite skin panel in plurality of composite skin panels1020may be an example of one implementation for composite structure100inFIG. 1. Further, each composite skin panel in plurality of composite skin panels1020may be implemented using, for example, composite structure800inFIG. 8.

Plurality of composite skin panels1020may be configured to conduct electrical energy generated in response to an electromagnetic event. For example, when lightning1022strikes body1006of aircraft1000, lightning1022encounters plurality of composite skin panels1020. Plurality of composite skin panels1020is configured to conduct the electrical currents and/or electromagnetic forces generated by lightning1022. In this manner, plurality of composite skin panels1020may provide protection from lightning1022and other types of electromagnetic events.

Turning now toFIG. 11, an illustration of a process for forming a composite layer is depicted in the form of a flowchart in accordance with an illustrative embodiment. The process illustrated inFIG. 11may be used to form composite layer106inFIG. 1.

The process begins by embedding a reinforcement in a matrix to form the composite layer (operation1100). The reinforcement comprises a conductive material. In some illustrative examples, the conductive material may be carbon in the form of a plurality of fibers.

In operation1100, embedding the reinforcement in the matrix causes the reinforcement to be located within the matrix. In one illustrative example, when the reinforcement is embedded in the matrix, no portion of the reinforcement is exposed at any of the surfaces of the composite layer. The reinforcement may be embedded in the matrix in a number of different ways. For example, without limitation, the reinforcement may be embedded in the matrix using a resin bath process, a chemical vapor deposition process, a vacuum deposition process, a chemical solution deposition process, a chemical bath deposition process, or some other suitable type of process for embedding the reinforcement within the matrix.

The process then exposes a portion of the reinforcement at a surface of the composite layer to increase electrical conductivity of the composite layer in a direction substantially perpendicular to the composite layer (operation1102), with the process terminating thereafter. In some illustrative examples, operation1102may be performed a first time for a first surface of the composite layer and a second time for a second surface of the composite layer.

Operation1102may be performed in a number of different ways. For example, operation1102may be performed by roughening the surface of the composite layer to pull the portion of the reinforcement embedded in the matrix out of the composite layer through the surface. In another illustrative example, operation1102may be performed by applying a chemical to the surface of the composite layer to chemically remove a portion of the matrix at the surface of the composite layer to expose the portion of the reinforcement.

In still other illustrative examples, operation1102may be performed by removing a portion of the surface of the composite layer to expose the portion of the reinforcement using a laser ablation process. In some cases, operation1102may be performed by threading a group of fibers in a plurality of fibers that form the reinforcement through the composite layer such that a first portion of the group of fibers is exposed at the surface of the composite layer and a second portion of the group of fibers remains substantially embedded in the matrix in the composite layer.

With reference now toFIG. 12, an illustration of a process for conducting electrical energy using a composite structure in the form of a flowchart is depicted in accordance with an illustrative embodiment. The process illustrated inFIG. 12may be implemented using composite structure100inFIG. 1.

The process begins by operating an object comprising a composite structure in which an electromagnetic event that occurs during operation of the object induces electrical energy in the composite structure (operation1200). The composite structure may be, for example, composite structure100inFIG. 1. This composite structure may be implemented in the form of, for example, composite structure800inFIG. 8.

The composite structure comprises a plurality of composite layers. A composite layer in the plurality of composite layers may comprise a matrix and a reinforcement. The reinforcement may comprise a conductive material and is embedded in the matrix. A first portion of the reinforcement is exposed at a first surface of the composite layer, and a second portion of the reinforcement is exposed at a second surface of the composite layer to increase an electrical connectivity of the composite layer at the first surface and the second surface, respectively, of the composite layer.

In this illustrative example, the electromagnetic event may be, for example, a lightning strike, a short circuit, an overloaded circuit, or some other suitable type of event configured to generate electrical energy at a surface of the composite structure. The electrical energy may take the form of a number of electrical currents and/or electromagnetic forces.

The process conducts the electrical energy induced in the composite structure in response to the electromagnetic event within the composite structure such that electrical conductivity of the composite structure is increased in a direction substantially perpendicular to the composite structure (operation1202), with the process terminating thereafter. In particular, contact between the portions of the reinforcements for the different composite layers exposed at the surfaces of the composite layers in the plurality of composite layers provides conductive pathways for the electrical energy to be conducted.

The flowcharts and block diagrams in the different depicted embodiments illustrate the architecture, functionality, and operation of some possible implementations of the apparatuses and methods in an illustrative embodiment. In this regard, each block in the flowcharts or block diagrams may represent a module, segment, function, and/or a portion of an operation or step. For example, one or more of the blocks may be implemented as program code, in hardware, or as a combination of the program code and hardware. When implemented in hardware, the hardware may, for example, take the form of integrated circuits that are manufactured or configured to perform one or more operations in the flowcharts or block diagrams.

Illustrative embodiments of the disclosure may be described in the context of aircraft manufacturing and service method1300as shown inFIG. 13and aircraft1400as shown inFIG. 14. Turning first toFIG. 13, an illustration of an aircraft manufacturing and service method is depicted in accordance with an illustrative embodiment. During pre-production, aircraft manufacturing and service method1300may include specification and design1302of aircraft1400inFIG. 14and material procurement1304.

During production, component and subassembly manufacturing1306and system integration1308of aircraft1400takes place. Thereafter, aircraft1400may go through certification and delivery1310in order to be placed in service1312. While in service1312by a customer, aircraft1400is scheduled for routine maintenance and service1314, which may include modification, reconfiguration, refurbishment, and other maintenance or service.

With reference now toFIG. 14, an illustration of an aircraft is depicted in which an illustrative embodiment may be implemented. In this example, aircraft1400is produced by aircraft manufacturing and service method1300inFIG. 13and may include airframe1402with plurality of systems1404and interior1406. Examples of systems1404include one or more of propulsion system1408, electrical system1410, hydraulic system1412, and environmental system1414. Any number of other systems may be included. Although an aerospace example is shown, different illustrative embodiments may be applied to other industries, such as the automotive industry, the marine industry, the energy industry, the construction industry, or some other suitable type of industry.

Apparatuses and methods embodied herein may be employed during at least one of the stages of aircraft manufacturing and service method1300inFIG. 13. For example, without limitation, composite structure100fromFIG. 1may be designed, manufactured, and implemented in aircraft1400inFIG. 14during at least one of specification and design1302, material procurement1304, component and subassembly manufacturing1306, system integration1308, in service1312, and/or maintenance and service1314. For example, composite structure100inFIG. 1may be used to implement a plurality of skin panels for aircraft1400inFIG. 14.

In one illustrative example, components or subassemblies produced in component and subassembly manufacturing1306inFIG. 13may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft1400is in service1312inFIG. 13.

As yet another example, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during production stages, such as component and subassembly manufacturing1306and system integration1308inFIG. 13. One or more apparatus embodiments, method embodiments, or a combination thereof may be utilized while aircraft1400is in service1312and/or during maintenance and service1314inFIG. 13. The use of a number of the different illustrative embodiments may provide protection for aircraft1400from electromagnetic events, such as, for example, without limitation, lightning strikes.

Thus, the different illustrative embodiments provide a method and apparatus for conducting electrical energy. In one illustrative embodiment, an apparatus comprises a matrix and a reinforcement. The matrix comprises a nonconductive material. The reinforcement comprises a conductive material. The reinforcement is located within the matrix to form a composite layer. A portion of the reinforcement is exposed at a surface of the composite layer such that electrical conductivity of the composite layer is increased in a direction substantially perpendicular to the composite layer.

Further, this composite layer may be one composite layer in a plurality of composite layers for a composite structure. Each of the plurality of composite layers for the composite structure may be implemented in a manner similar to the composite layer described above. In particular, a first portion of the reinforcement is exposed at a first surface of each composite layer to increase electrical conductivity of each composite layer at the first surface of each composite layer. A second portion of the reinforcement is exposed at a second surface of each composite layer to increase the electrical conductivity of each composite layer at the second surface of each composite layer. The first portion and the second portion of the reinforcement in each composite layer in the plurality of composite layers is configured to electrically connect the plurality of composite layers to each other such that the composite structure has a desired level of electrical conductivity in a direction substantially perpendicular to the composite structure.