Three-dimensional filament network for a composite laminate

A method and apparatus for forming a composite structure. The apparatus comprises a fiber layer. The fiber layer comprises a plurality of fiber bundles and a number of filler portions. The plurality of fiber bundles has a number of spaces between the plurality of fiber bundles. A number of filler is comprised of discontinuous filaments that substantially fill the number of spaces between the plurality of fiber bundles.

BACKGROUND INFORMATION

The present disclosure relates generally to composite structures and, in particular, to composite laminates. Still more particularly, the present disclosure relates to a method and apparatus for improving the through-thickness strength of a composite laminate using a filament network.

A composite laminate is formed by one or more composite layers, which are also referred to as plies or lamina. Each composite layer includes a reinforcement material and a matrix material. The reinforcement material may take the form of, for example, fibers, which may be oriented in a single direction to make the composite layer unidirectional or in two directions to make the composite layer bidirectional. The matrix material may take the form of, for example, a resin.

Fiber bundles may be laid up in layers to form a reinforcement layup, which may be referred to as a preform. The preform may be a referred to as a wet preform when the fiber bundles have been pre-impregnated with resin that has been partially cured for handling or a dry preform when no resin is present. Resin is infused within the spaces between the fiber bundles of the preform to form an integrated preform. The integrated preform may be partially cured to form a partially cured composite laminate or fully cured to form a fully cured composite laminate. A carbon fiber-reinforced polymer (CFRP) laminate is an example of one type of composite laminate.

In some cases, an undesired inconsistency may develop within the composite laminate. An undesired inconsistency is an inconsistency that is outside of selected tolerances or beyond some selected threshold for the inconsistency. An undesired inconsistency may take the form of, for example, a crack, a thermally-induced crack, a notch, a delamination, or some other type of inconsistency that is outside of selected tolerances.

The ability of a composite laminate to absorb energy in the presence of an undesired inconsistency, while still performing within selected tolerances, is commonly referred to as the notch toughness of the composite laminate. Improving the notch toughness of a composite laminate, while still allowing a resin to be effectively infused between and around the fibers, may be more difficult than desired. Some currently available methods for improving the notch toughness of a composite laminate may reduce the performance of the composite laminate in other areas.

For example, one currently available solution includes laying up a sheet of discontinuous fibers between each pair of composite layers in the composite laminate. However, this type of solution improves the notch toughness of the composite laminate but reduces the resistance of the composite laminate to the formation of undesired inconsistencies.

Other currently available solutions include Z-pinning, stitching, and tufting. Z-pinning includes forcing pins through the reinforcement layup or the uncured preform in a Z direction. Stitching and tufting include threading fibers through the reinforcement layup or the uncured preform in the Z direction. However, these types of solutions may still reduce the resistance of the composite laminate to the formation of undesired inconsistencies, cause undesired effects to the fibers, and limit the sizes and positioning of the pins or threads that can be used. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.

SUMMARY

In one illustrative embodiment, an apparatus comprises a fiber layer. The fiber layer comprises a plurality of fiber bundles and a number of filler portions. The plurality of fiber bundles has a number of spaces between the plurality of fiber bundles. A number of filler portions is comprised of discontinuous filaments that substantially fill the number of spaces between the plurality of fiber bundles.

In another illustrative embodiment, a composite structure comprises a number of fiber layers, a filament network associated with the number of fiber layers, and a resin. Each fiber layer in the number of fiber layers includes a plurality of fiber bundles having a number of spaces between the plurality of fiber bundles. The filament network is configured to improve a notch toughness of the composite structure and a resistance of the composite structure to a number of undesired inconsistencies. The filament network comprises a number of filler portions that fill the number of spaces between the plurality of fiber bundles in each of the number of fiber layers. A filler portion in the number of filler portions comprises a plurality of discontinuous filaments and a binding material. The binding material is configured to hold the plurality of discontinuous filaments together. The binding material is further configured to bind the plurality of discontinuous filaments to at least one of the plurality of fiber bundles. The resin binds the number of fiber layers and the filament network associated with the number of fiber layers together.

In yet another illustrative embodiment, a method for forming a composite structure is provided. A number of filament layers comprised of discontinuous filaments is positioned relative to a plurality of fiber bundles to form a fiber layer having a number of filler portions that substantially fill a number of spaces between the plurality of fiber bundles. A reinforcement layup is formed for the composite structure using the fiber layer.

DETAILED DESCRIPTION

The illustrative embodiments recognize and take into account different considerations. For example, the illustrative embodiments recognize and take into account that it may be desirable to have a method and apparatus for improving the notch toughness of a composite laminate, while also maintaining at least a desired level of resistance to the formation and growth of undesired inconsistencies. In particular, the illustrative embodiments recognize and take into account that it may be desirable to improve the notch toughness of a composite laminate, while still allowing a resin to be effectively infused within the reinforcement layup for the composite laminate.

Thus, the illustrative embodiments provide a method and apparatus for forming a reinforcement layup for a composite laminate that allows a resin to be infused within the layup with a desired level of ease and improves the notch toughness of the composite laminate formed using the reinforcement layup. In one illustrative example, a number of fiber layers are laid up to form a reinforcement layup. Each fiber layer in the number of fiber layers may include a plurality of fiber bundles having a number of spaces between the plurality of fiber bundles and filament filters comprised of discontinuous filaments that fill the number of spaces between the plurality of fiber bundles. A resin may be infused into the reinforcement layup to form an uncured preform. The uncured preform may then be cured to form the composite laminate.

Referring now to the figures and, in particular, with reference toFIG. 1, an illustration of a manufacturing environment is depicted in the form of a block diagram in accordance with an illustrative embodiment. In this illustrative example, manufacturing environment100is an example of an environment in which composite structure102may be manufactured. Composite structure102takes the form of composite laminate104in this illustrative example.

As depicted, composite structure102is formed by integrating resin108with reinforcement layup106. Reinforcement layup106may also be referred to as a preform. As used herein, “integrating” resin108with reinforcement layup106means causing resin108to be located within reinforcement layup106. This integration may be performed by, for example, without limitation, infusing reinforcement layup106with resin108, injecting resin108into reinforcement layup106, saturating reinforcement layup106with resin108, mixing resin108with reinforcement layup106, impregnating resin108with reinforcement layup106, or some combination thereof.

In this illustrative example, reinforcement layup106is infused with resin108. Resin108is comprised of at least one polymer. For example, resin108may be a polymeric resin comprised of at least one of a thermosetting polymer, a thermoplastic polymer, or some other type of polymer.

As used herein, the phrase “at least one of,” when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, action, process, or category. In other words, “at least one of” means any combination of items or number of items may be used from the list, but not all of the items in the list may be required.

For example, “at least one of item A, item B, and item C” may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, “at least one of item A, item B, and item C” may mean, for example, without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

Infusing resin108within reinforcement layup106forms composite structure102that may then be left uncured, partially cured, or fully cured, depending on the implementation. This composite structure102may be referred to as an integrated preform. When left uncured, composite structure102may be referred to as an integrated preform or an uncured composite structure. The integrated preform may be partially cured to take the form of a partially cured composite structure. This partial curing may be performed to allow easier transport and handling of the composite structure. The integrated preform may be fully cured to take the form of a fully cured composite structure.

In this illustrative example, reinforcement layup106includes fiber bundles107and filament network110that together form number of fiber layers112. As used herein, a “number of” items may include one or more items. In this manner, number of fiber layers112may include one or more layers.

Filament network110is comprised of discontinuous filaments111and binding material113. Discontinuous filaments111may be fibers that do not extend the entire length or width of composite structure102. Discontinuous filaments111may include filaments of at least one of different sizes, different diameters, different cross-sectional shapes, different types, or some combination thereof. Discontinuous filaments111may include at least one of carbon fibers, silica fibers, glass fibers, polyamide fibers, polyether ketone fibers, polyester fibers, polyether sulfone fibers, polyimide fibers, polyurethane fibers, or other types of fibers.

Further, in this illustrative example, discontinuous filaments111may have a random orientation relative to each other. However, in other illustrative examples, discontinuous filaments111may not be randomly oriented relative to each other.

Binding material113is configured to bind filament network110to fiber bundles107and fiber bundles107to each other. Binding material113is configured to hold discontinuous filaments111together in response to at least one of heat, pressure, or a chemical reaction being applied to binding material113. Binding material113holds discontinuous filaments111together during handling.

Binding material113may take a number of different forms. For example, binding material113may be comprised of at least one of a thermoset material, a thermoplastic material, or some other type of binding material. Further, binding material113may be implemented in a form selected from at least one of beads, threads, pieces of tape, or some other form, depending on the implementation.

Fiber layer114is an example of one of number of fiber layers112. Fiber layer114includes plurality of fiber bundles116having number of spaces118between plurality of fiber bundles116. In this illustrative example, a fiber bundle in plurality of fiber bundles116is an untwisted grouping of fibers that run substantially parallel to each other. The fibers that form a fiber bundle in plurality of fiber bundles116may be continuous fibers. As used herein, a “continuous fiber” may be a long fiber that extends across substantially the entire length or width of composite structure102.

A fiber bundle in plurality of fiber bundles116may be selected from at least one of a tow, a ribbon, or a piece of tape, depending on the implementation. A fiber bundle may be implemented as a unidirectional tow in some cases. Depending on the implementation, plurality of fiber bundles116may include the same or different types of fiber bundles. In other illustrative examples, a fiber bundle may be a twisted grouping of fibers, a braided grouping of fibers, or some other type of grouping of fibers.

In this illustrative example, the density of continuous fibers in a fiber bundle in plurality of fiber bundles116is sufficiently high such that the porosity of the fiber bundle is below a selected threshold. This selected threshold may be selected such that the permeability of the fiber bundle with respect to resin108is below a selected threshold.

As used herein, the “porosity” of an item is the measure of how much open space is present within the item. The open space may be in the form of, for example, without limitation, openings, voids, gaps, or some other type of open space. Further, as used herein, the “permeability” of an item may be the measure of the ease with which a fluid, resin108in these illustrative examples, can move through the item. Typically, increased porosity results in increased permeability.

In this illustrative example, the porosity and permeability of each of plurality of fiber bundles116may be low. In particular, the permeability of a fiber bundle in plurality of fiber bundles116may be sufficiently low such that resin108permeates, or flows, through a fiber bundle in plurality of fiber bundles116very slowly when resin108is infused within reinforcement layup106.

In other illustrative examples, one or more of plurality of fiber bundles116may be pre-impregnated with a resin that is the same type as or a different type than resin108. When plurality of fiber bundles116is pre-impregnated with a resin, reinforcement layup106may be referred to as a wet preform. When plurality of fiber bundles116is not pre-impregnated with a resin, reinforcement layup106may be referred to as a dry preform.

Plurality of fiber bundles116may be arranged such that plurality of fiber bundles116run substantially parallel to each other and have number of spaces118between plurality of fiber bundles116. In one illustrative example, the fibers in plurality of fiber bundles116include, for example, without limitation, carbon fibers, glass fibers, boron fibers, other types of fibers, or some combination thereof.

Fiber layer114also includes number of filler portions120of filament network110that substantially fill number of spaces118between plurality of fiber bundles116. As used herein, a filler portion in number of filler portions120is a portion of filament network110.

Plurality of filament layers121are positioned relative to the plurality of fiber bundles in each fiber layer in number of fiber layers112to form filament network110. In particular, plurality of filament layers121are positioned relative to the plurality of fiber bundles in each fiber layer in number of fiber layers112and the number of filler portions that fill the number of spaces between the plurality of fiber bundles in each of number of fiber layers112.

For example, number of filament layers122in plurality of filament layers121may be used to form at least one of number of fiber layers112. For example, number of filament layers122may be positioned relative to plurality of fiber bundles116to form fiber layer114. Each of number of filler portions120is formed by one or more portions of one or more filament layers in number of filament layers122. In one illustrative example, one portion of one filament layer is used to form one portion of number of filler portions120. In another illustrative example, portions of two different filament layers may be used to form one portion of number of filler portions120.

Filament layer124is an example of one of number of filament layers122. Filament layer124may be implemented as at least one of a veil, a nonwoven mat, a web, a sheet, a tape, or some other type of collection of discontinuous filaments.

The density of discontinuous filaments in a filament layer in plurality of filament layers121, such as filament layer124, is lower than the density of continuous fibers in a fiber bundle in plurality of fiber bundles116. In particular, the density of discontinuous filaments in plurality of filament layers121is sufficiently low such that the porosity of each of plurality of filament layers121is above a selected threshold.

This selected threshold may be selected such that the permeability of each of plurality of filament layers121with respect to resin108is above a selected threshold. In particular, in this illustrative example, each of plurality of filament layers121may have a permeability sufficiently high to allow resin108to permeate, or flow through, the filament layer when resin108is infused within reinforcement layup106.

The porosity of plurality of filament layers121may provide open spaces through which a fluid, such as resin108, may flow. Other types of fluids may also be allowed to flow through the open spaces within plurality of filament layers121. For example, air and gases may be allowed to permeate through plurality of filament layers121. Further, in some cases, these open spaces may be used to remove at least one of air, undesired gases, or excess moisture from reinforcement layup106.

In one illustrative example, filament layer124is wrapped around a fiber bundle in plurality of fiber bundles116such that filament layer124covers an entirety of the outer surface of the fiber bundle. This process may be repeated for each fiber bundle in plurality of fiber bundles116. In other words, a filament layer in number of filament layers122may be wrapped around each of plurality of fiber bundles116. Plurality of fiber bundles116are then arranged relative to each other such that fiber layer114is formed.

In one illustrative example, plurality of fiber bundles116is arranged such that the fiber bundles in plurality of fiber bundles116run substantially parallel to each other. In this example, each of number of filler portions120is formed by a first portion of a first filament layer in number of filament layers122and a second portion of a second filament layer in number of filament layers122. Of course, in other illustrative examples, number of filament layers122may be used to form fiber layer114in other ways.

In this illustrative example, each of number of fiber layers112is formed in a manner similar to fiber layer114such that each of number of fiber layers112includes a plurality of fiber bundles having a number of spaces between the plurality of fiber bundles that are filled by a number of filler portions of filament network110.

Number of fiber layers112is then laid up to form reinforcement layup106. In other words, the fiber layers in number of fiber layers112are stacked at least one of, for example, without limitation, one on top of the other or side-by-side to form reinforcement layup106. In forming reinforcement layup106, filament network110is formed. In particular, plurality of filament layers121may be positioned relative to the plurality of fiber bundles in each of number of fiber layers112such that filament network110includes number of interlayer filler portions126and number of outer filler portions130, in addition to the number of filler portions in the number of spaces between the plurality of fiber bundles in each of number of fiber layers112.

Number of interlayer filler portions126substantially fills number of interlayer spaces128between number of fiber layers112. Number of outer filler portions130substantially fills number of outer spaces132around number of fiber layers112. In this illustrative example, filament network110includes the number of filler portions in each of number of fiber layers112, number of interlayer filler portions126, and number of outer filler portions130. Filament network110may take the form of three-dimensional filament network134.

Once reinforcement layup106has been formed, reinforcement layup106is cured such that binding material113binds filament network110to fiber bundles107, fiber bundles107to each other, and number of fiber layers112to each other. The three-dimensional nature of filament network110strengthens reinforcement layup106in the three dimensions.

Resin108may be infused within reinforcement layup106such that resin108fills the open spaces of filament network110to form composite structure102. These open spaces are the open spaces within plurality of filament layers121. Additionally, depending on the implementation, resin108may also fill any spaces within each of the fiber bundles in reinforcement layup106.

Filament network110may improve notch toughness138of composite structure102, resistance140of composite structure102to one or more types of undesired inconsistencies, or both. Notch toughness138is the ability of composite structure102to absorb energy in the presence of one or more undesired inconsistencies. For example, filament network110may improve notch toughness138of composite structure102with respect to delamination, cracking, micro-cracking, and other types of undesired inconsistencies.

In one illustrative example, discontinuous filaments111of filament network110toughen composite structure102, while also maintaining at least a desired level of resistance140to undesired inconsistencies. Resistance140is the ability of composite structure102to prevent the formation, growth, or both of one or more types of undesired inconsistencies. Filament network110may help reduce or prevent the growth of undesired inconsistencies. Reducing or preventing the growth of undesired inconsistencies may reduce or prevent affecting a larger area of composite structure102than desired.

In one illustrative example, when composite structure102is substantially planar, resistance140may be increased such that the area of composite structure102, with respect to the x-y plane of composite structure102, affected by an undesired inconsistency does not increase in size more than desired.

For example, in some cases, filament network110may only include number of interlayer filler portions126and the number of filler portions in each of number of fiber layers112. In some illustrative examples, filament network110may be configured to improve other mechanical properties of composite structure102in addition to notch toughness138and resistance140.

With reference now toFIG. 2, an illustration of a portion of a reinforcement layup is depicted in accordance with an illustrative embodiment. In this illustrative example, reinforcement layup200is an example of one implementation for reinforcement layup106inFIG. 1.

As depicted, reinforcement layup200includes number of fiber layers202and filament network203. Number of fiber layers202and filament network203are examples of implementations for number of fiber layers112and filament network110, respectively, inFIG. 1.

Number of fiber layers202includes fiber layers204,206,208,210, and212. Fiber layer204includes plurality of fiber bundles214that run substantially parallel to each other. Fiber layer206includes plurality of fiber bundles216that run substantially parallel to each other. Similarly, fiber layer208includes plurality of fiber bundles218that run substantially parallel to each other. Fiber layer210includes plurality of fiber bundles220that run substantially parallel to each other. Fiber layer212includes plurality of fiber bundles222that run substantially parallel to each other.

Plurality of fiber bundles214run substantially parallel to x-axis224. Plurality of fiber bundles216and plurality of fiber bundles218run at a 45 degree angle relative to x-axis224. Plurality of fiber bundles220and plurality of fiber bundles222run substantially parallel to y-axis226. Thus, plurality of fiber bundles220and plurality of fiber bundles222run substantially perpendicular to plurality of fiber bundles214.

In this illustrative example, filament network203includes filler portions230, number of interlayer filler portions232, and number of outer filler portions234. Filler portions230, number of interlayer filler portions232, and number of outer filler portions234are examples of one implementation for the number of filler portions in each of number of fiber layers112, number of interlayer filler portions126, and number of outer filler portions130, respectively, inFIG. 1.

Filler portions230run substantially parallel to z-axis228in this illustrative example. Filler portion236is an example of one of filler portions230. Filler portion236fills the space between fiber bundle238and fiber bundle240, which may be examples of two fiber bundles in plurality of fiber bundles216.

Number of interlayer filler portions232includes interlayer filler portions242,244,246, and248. These interlayer filler portions fill the interlayer spaces between number of fiber layers202. Number of outer filler portions234includes outer filler portion250and outer filler portion252. These outer filler portions fill the outer spaces around number of fiber layers202. A cutaway view of reinforcement layup200with portion254of fiber layer210, outer filler portion250, and interlayer filler portion242cutaway is depicted inFIG. 3below.

Resin may be infused within reinforcement layup200to form a composite structure. Filament network203provides a plurality of pathways that allow resin to be infused within reinforcement layup200. Filament network203increases the notch toughness of the composite structure formed when resin108fromFIG. 1, is infused within reinforcement layup200. Further, filament network203may also increase the resistance of the composite structure to the formation, growth, or both of undesired inconsistencies.

With reference now toFIG. 3, an illustration of a cutaway view of reinforcement layup200with portion254of reinforcement layup200fromFIG. 2removed is depicted in accordance with an illustrative embodiment. In this illustrative example, a cross-sectional view of reinforcement layup200fromFIG. 2is depicted taken along lines3-3inFIG. 2.

The orientation of plurality of fiber bundles216may be more clearly seen in this illustrative example. Further, as depicted, filament network203is a three-dimensional filament network.

With reference now toFIG. 4, an illustration of a side view of reinforcement layup200fromFIG. 2is depicted in accordance with an illustrative embodiment. In this illustrative example, a side view of reinforcement layup200fromFIG. 2is depicted in the direction of lines4-4inFIG. 2.

With reference now toFIGS. 5-11, illustrations of different ways in which a filament layer may be positioned relative to a fiber bundle are depicted in accordance with an illustrative embodiment. The manner in which a filament layer is positioned relative to a fiber bundle inFIGS. 5-11may be used in multiple fiber bundles that may then be arranged to form one or more fiber layers, such as number of fiber layers112inFIG. 1.

Referring now toFIG. 5, an illustration of a filament layer positioned relative to a fiber bundle is depicted in accordance with an illustrative embodiment. In this illustrative example, fiber bundle500is an example of one implementation for a fiber bundle in plurality of fiber bundles116inFIG. 1.

Filament layer502is positioned relative to fiber bundle500. Filament layer502is an example of one implementation for a filament layer in plurality of filament layers121inFIG. 1. As depicted, filament layer502is comprised of discontinuous filaments504, binding material506, and openings508.

With reference now toFIG. 6, an illustration of a filament layer positioned relative to a fiber bundle is depicted in accordance with an illustrative embodiment. In this illustrative example, filament layer502is positioned relative to fiber bundle500such that exposed portion600of outer surface510of fiber bundle500is formed at side516. More specifically, filament layer502is wrapped around outer surface510in a manner that leaves a portion of outer surface510at side516exposed. This portion may be exposed portion600.

Exposed portion600may help increase the permeability of the reinforcement layup formed using fiber bundle500and filament layer502, prevent changes in the thickness of the reinforcement layup thickness that would arise from overlaying multiple filament layers under or over fiber bundle500, and facilitate a wider manufacturing window than only using an overlapped or pinched format.

With reference now toFIG. 7, an illustration of a filament layer positioned relative to a fiber bundle is depicted in accordance with an illustrative embodiment. In this illustrative example, filament layer502is positioned relative to fiber bundle500such that pinched portion700is formed.

In particular, filament layer502is wrapped around outer surface510of fiber bundle500such that a first end and a second end of filament layer502are located at side518of fiber bundle500. The first end and the second end of filament layer502are pinched together at side518of fiber bundle500to form pinched portion700.

With reference now toFIG. 8, an illustration of two filament layers positioned relative to a fiber bundle is depicted in accordance with an illustrative embodiment. In this illustrative example, filament layer502and filament layer800are positioned relative to side510and side516, respectively, of fiber bundle500. In this manner, filament layer502may be a first filament layer positioned relative to a first side of fiber bundle500and filament layer800may be a second filament layer positioned relative to a second side of fiber bundle500.

Filament layer800includes discontinuous filaments802, binding material804, and openings806. As depicted, a first end of filament layer502and a first end of filament layer800are pinched together to form first pinched portion808. Further, a second end of filament layer502and a second end filament layer800are pinched together to form second pinched portion810. In particular, the ends of filament layer502and filament layer800are pinched together at side514to form first pinched portion808and at side518to form second pinched portion810.

With reference now toFIG. 9, an illustration of a filament layer positioned relative to a fiber bundle is depicted in accordance with an illustrative embodiment. In this illustrative example, filament layer502is positioned relative to fiber bundle500such that overlap portion900is formed. In particular, filament layer502is wrapped around outer surface510relative to fiber bundle500such that a first end and a second end of filament layer502overlap at side516of fiber bundle500to form overlap portion900.

With reference now toFIG. 10, an illustration of a filament layer positioned relative to a fiber bundle is depicted in accordance with an illustrative embodiment. In this illustrative example, filament layer502is positioned relative to fiber bundle500. As depicted, filament layer502is positioned relative to fiber bundle500such that filament layer502has an S-shape.

With this S-shape, portion1000and portion1002of filament layer502cover fiber bundle500. Portion1000covers only a portion of side512of fiber bundle500. A portion of a different filament layer may be used to cover the rest of side512. In this illustrative example, portion1000may be used to form an interlayer filler portion in a filament network.

Portion1002covers the entire side514of fiber bundle500. Portion1002may be used to form a filler portion in the filament network.

Portion1004of filament layer502may be used to cover a portion of another fiber bundle. Portion1004may be used to form another interlayer filler portion in the filament network. As depicted, portion1002connects portion1004to portion1000.

With reference now toFIG. 11, an illustration of a filament layer positioned relative to a fiber bundle is depicted in accordance with an illustrative embodiment. In this illustrative example, filament layer502is positioned relative to fiber bundle500. As depicted, filament layer502is positioned such that filament layer502has a hat-shape.

Portion1100of filament layer502covers the entire outer surface510of sides512,514, and518of fiber bundle500. Side516of fiber bundle500is left exposed. Portion1102of filament layer502may be used to cover the side of another fiber bundle. Portion1104of filament layer502may be used to cover the side of yet another fiber bundle.

With reference now toFIG. 12, an illustration of a potential configuration for a filament layer is depicted in accordance with an illustrative embodiment. In this illustrative example, plurality of configurations1200includes illustrations of some configurations for a filament layer. As depicted, plurality of configurations1200includes configuration1202, configuration1204, configuration1206, and configuration1208. The binding material used in each of these configurations may be different.

With configuration1202, filament layer1203includes discontinuous filaments1210, binding material1212, and openings1214. Binding material1212takes the form of thermoplastic threads. With configuration1204, filament layer1205includes discontinuous filaments1216, binding material1218, and openings1220. Binding material1218takes the form of thermoset tape that has been arranged to form a grid.

With configuration1206, filament layer1207includes discontinuous filaments1222, binding material1224, and openings1226. Binding material1224takes the form of binding particles attached to discontinuous filaments1222. With configuration1208, filament layer1209includes discontinuous filaments1228, binding material1230, and openings1232. Binding material1230takes the form of a thermoset coating on discontinuous filaments1228in this illustrative example.

The illustrations of reinforcement layup200inFIGS. 2-3, filament layer502and fiber bundle500inFIGS. 5-11, and plurality of configurations1200for a filament layer inFIG. 12are not meant to imply physical or architectural limitations to the manner in which an illustrative embodiment may be implemented. Other components in addition to or in place of the ones illustrated may be used. Some components may be optional.

The different components shown inFIGS. 2-12may be illustrative examples of how components shown in block form inFIG. 1can be implemented as physical structures. Additionally, some of the components inFIGS. 2-12may be combined with components inFIG. 1, used with components inFIG. 1, or a combination of the two.

With reference now toFIG. 13, an illustration of a process for forming a composite structure is depicted in the form of a flowchart in accordance with an illustrative embodiment. The process illustrated inFIG. 13may be implemented to form composite structure102inFIG. 1.

The process may begin by positioning a number of filament layers relative to a plurality of fiber bundles to form a fiber layer having a number of filler portions comprised of discontinuous filaments that substantially fill a number of spaces between the plurality of fiber bundles (operation1300). Next, the fiber layer is used to form a reinforcement layup for a composite structure (operation1302).

A resin is integrated with the reinforcement layup to form the composite structure in which the filament network improves a notch toughness of the composite structure (operation1304), with the process terminating thereafter. The composite structure may be left uncured, partially cured, or fully cured, depending on the implementation.

With reference now toFIG. 14, an illustration of a process for forming a reinforcement layup is depicted in the form of a flowchart in accordance with an illustrative embodiment. The process illustrated inFIG. 14may be implemented to form composite structure102inFIG. 1.

The process may begin by positioning an initial filament layer for a fiber layer for a reinforcement layup over a selected layer (operation1400). The first time that operation1400is performed, the selected layer is the surface of a tooling apparatus, such as a mold. Any subsequent times that operation1400is performed, the selected layer may be the previous fiber layer formed.

A fiber bundle is then positioned over the initial filament layer (operation1402). Another filament layer is then positioned over the fiber bundle and the selected layer such that a portion of the next filament layer covers at least a portion of the fiber bundle and a portion of the selected layer (operation1404). In operation1404, the filament layer is positioned such that the filament layer has an S-shape.

Thereafter, a determination is made as to whether another fiber bundle is needed for the fiber layer (operation1406). If an additional fiber bundle is needed, another fiber bundle is positioned over the previously positioned filament layer (operation1408). The process then returns to operation1404as described above.

With respect to operation1406, if an additional fiber bundle is not needed for the initial fiber layer, a determination is made as to whether any more fiber layers are needed to form the reinforcement layup (operation1410). If no additional fiber layers are needed to form the reinforcement layup, the process terminates. A reinforcement layup is formed by performing the process described inFIG. 14. Resin may be infused within the reinforcement layup to form an integrated preform. The integrated preform may then be cured to form a composite structure, such as a composite laminate.

With reference again to operation1410, if any additional fiber layers are needed to form the reinforcement layup, the process returns to operation1400as described above. The process described inFIG. 14ensures that the discontinuous filaments in each of the filament layers used to form the reinforcement layup substantially fill the spaces between the fiber bundles within each fiber layer of the reinforcement layup.

The flowcharts and block diagrams in the different depicted embodiments illustrate the architecture, functionality, and operation of some possible implementations of apparatuses and methods in an illustrative embodiment. In this regard, each block in the flowcharts or block diagrams may represent a module, a segment, a function, a portion of an operation or step, some combination thereof.

Illustrative embodiments of the disclosure may be described in the context of aircraft manufacturing and service method1500as shown inFIG. 15and aircraft1600as shown inFIG. 16. Turning first toFIG. 15, an illustration of an aircraft manufacturing and service method is depicted in the form of a block diagram in accordance with an illustrative embodiment. During pre-production, aircraft manufacturing and service method1500may include specification and design1502of aircraft1600inFIG. 16and material procurement1504.

During production, component and subassembly manufacturing1506and system integration1508of aircraft1600inFIG. 16takes place. Thereafter, aircraft1600inFIG. 16may go through certification and delivery1510in order to be placed in service1512. While in service1512by a customer, aircraft1600inFIG. 16is scheduled for routine maintenance and service1514, which may include modification, reconfiguration, refurbishment, and other maintenance or service.

With reference now toFIG. 16, an illustration of an aircraft is depicted in the form of a block diagram in which an illustrative embodiment may be implemented. In this example, aircraft1600is produced by aircraft manufacturing and service method1500inFIG. 15and may include airframe1602with plurality of systems1604and interior1606. Examples of systems1604include one or more of propulsion system1608, electrical system1610, hydraulic system1612, and environmental system1614. 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.

Apparatuses and methods embodied herein may be employed during at least one of the stages of aircraft manufacturing and service method1500inFIG. 15. In particular, composite structure102fromFIG. 1may be manufactured during any one of the stages of aircraft manufacturing and service method1500. For example, without limitation, composite structure102fromFIG. 1may be manufactured during at least one of component and subassembly manufacturing1506, system integration1508, routine maintenance and service1514, or some other stage of aircraft manufacturing and service method1500. Still further, composite structure102fromFIG. 1may be used in one or more structures of aircraft1600. For example, composite structure102may be used to form a structure in airframe1602, interior1606, or some other part of aircraft1600.

In one illustrative example, components or subassemblies produced in component and subassembly manufacturing1506inFIG. 15may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft1600is in service1512inFIG. 15. 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 manufacturing1506and system integration1508inFIG. 15. One or more apparatus embodiments, method embodiments, or a combination thereof may be utilized while aircraft1600is in service1512, during maintenance and service1514inFIG. 15, or both. The use of a number of the different illustrative embodiments may substantially expedite the assembly of and reduce the cost of aircraft1600.