Patent Description:
The strength, stiffness and load transfer characteristics of a composite laminate structure may be optimized through control of fiber orientation during the layup process. Conventional composite laminates may be laid up using pre-preg tapes, tows or broad goods, employing either automated fiber placement equipment or hand placement techniques to layup the material. Generally, the resulting composite structure exhibits substantially consistent structural properties throughout. In some cases, however, it may be necessary or desirable to control the thickness and/or fiber orientation in local areas of a composite laminate in order to optimize its structural properties and/or account for higher local stresses.

The ability to control local thickness/fiber orientation is limited using current fabrication processes. For example, automated fiber placement equipment may be used to steer continuous tows onto the substrate, but the radius of curvature that can be achieved is limited, thus making control of fiber orientation difficult in local areas having tight contours. Achieving close control over thickness and/or fiber orientation in local areas of laminate may also be costly and timeconsuming.

Accordingly, there is a need for a method and apparatus for controlling composite laminate thickness and/or fiber orientation in local areas of a laminate in order to optimize the laminate's structural properties. There is also a need for a method and apparatus of the type mentioned above which is efficient, highly controllable and which may reduce labor and material costs.

<CIT>, in accordance with its abstract, states a process and device for producing a starting material for forming a fibre-reinforced part. Continuous fibre strands are impregnated with a resin and then cut up into segments of predetermined length. The segments are collected in such a manner that they are piled up to form the starting material.

The fibres are collected in a controlled manner so that they have a fibre orientation preselected for the moulded part.

<CIT>, in accordance with its abstract, states a method of producing a laminate comprising the following steps: (a) Forming patches from a substantially unidirectional fabric, treated with a resin; (b) Substantially randomizing the orientation of said patches; (c) Distributing a plurality of said patches in layers around a former; (d) Causing said layers of patches to amalgamate by means of activation of the resin treatment.

<CIT>, in accordance with its abstract, states a trough-like deflector is attached to the body of a fiber chopper and extends outwardly from the lower portion of the chopper nozzle opening. The sides of the deflector are upwardly divergent to form a trough extending generally in the direction of the flow path of fibers normally ejected from the nozzle. The deflector skews the flow path of fibers ejected from the sides of the nozzle in an upward and inward direction. The deflector aims to prevent the loss of chopped fibers to spurious air currents created by the ejected fiber stream and aims to promote a more uniform lay-down of fibers onto a substrate.

<CIT>, in accordance with its abstract, states a chopped fiber bundle including a large number of unidirectionally arranged reinforced fibers. The length of each of the reinforced fibers is in the range of <NUM> to <NUM>. The chopped fiber bundle has a transition segment in which the number of the reinforced fibers increases toward the central part of the chopped fiber bundle in the aligned direction of the reinforced fibers with both ends in the aligned of the reinforced fibers in the chopped fiber bundle being a starting point. The level of a change in total sectional area of the large number of reinforced fibers is not more than <NUM><NUM> per mm in the aligned direction of the reinforced fibers over the whole area in the longitudinal direction of the chopped fiber bundle.

There is described herein a method of forming a composite feature having discontinuous reinforcement fibers. The method comprises: (a) producing a plurality of resin infused fiber segments each having unidirectional reinforcing fibers, wherein the fibers extend substantially parallel to each other, and wherein producing the resin infused fiber segments comprises chopping fiber pre-preg into individual resin infused fiber segments ; (b) placing the resin infused fiber segments on a substrate by introducing the resin infused fiber segments into an airstream, and using the airstream to stream the resin infused fiber segments from an applicator onto the substrate; and (c) after the resin infused fiber segments have been placed on the substrate, rotating the resin infused fiber segments so as to arrange the resin infused fiber segments such that the reinforcing fibers of the resin infused fiber segments placed on the substrate are substantially aligned relative to a desired reference orientation.

There is also described herein apparatus for laying up a composite structure. The apparatus comprises an applicator adapted to move over a substrate, and dispense at least one stream of substantially aligned chopped, resin infused fiber segments onto the substrate. The applicator includes: (a) a supply of continuous resin infused fiber; (b) a chopper for chopping the continuous resin infused fiber into individual resin infused fiber segments each having unidirectional reinforcing fibers, wherein the fibers extend substantially parallel to each other; and (c) an airstream generator for streaming the resin infused fiber segments from the applicator onto the substrate such that the reinforcing fibers of the resin infused fiber segments placed on the substrate are substantially aligned relative to a desired reference orientation; and orientation means for rotating the resin infused fiber segments after the resin infused fiber segments have been placed on the substrate so as to arrange the resin infused fiber segments such that the reinforcing fibers of the resin infused fiber segments placed on the substrate are substantially aligned relative to a desired reference orientation.

The disclosed examples provide a method and apparatus for fabricating composite features of laminates which provide increased control over feature thickness and/or fiber orientation in local areas of a laminate structure, such as in tight contours and/or within transitions in laminate thickness. Composite material may be laid up such that fiber orientations are substantially continuously aligned with load vectors in selected local areas of a laminate, thereby optimizing the laminate's structural properties.

The amount of composite material required to provide local areas of a laminate structure with desired structural properties may be reduced by forming the composite features using scrap pre-preg derived from other products/processes. Recycling of scrap pre-preg for use in the disclosed method may reduce material costs, thus optimizing the buy-to-fly ratio (the ratio of materials weight procured to the weight of the finished product) for aircraft applications of the examples. The examples allow composite material in the form of discontinuous fiber pre-preg to be "steered" onto a substrate in order to achieve desired fiber orientations.

The use of discontinuous fiber pre-preg allows greater control over laminate thickness variations in local areas of the laminate, while allowing local tailoring of laminate thickness in three dimensions to provide smooth transitions between differing features of a laminate structure. Moreover, the use of discontinuous fiber pre-preg permits the formation of doublers or other padups having tight contours and/or tapered edges to achieve smooth load transitions within a structure. Also, the use of discontinuous fiber pre-preg may result in composite features having a higher fiber content.

According to one disclosed example, a method is provided of forming a composite feature having discontinuous reinforcement fibers. The method comprises producing a plurality of resin infused fiber segments each having unidirectional reinforcing fibers, placing the resin infused fiber segments on a substrate, and arranging the resin infused fiber segments such that the reinforcing fibers of resin infused fiber segments placed on the substrate are substantially aligned relative to a desired reference orientation. Producing the resin infused fiber segments includes chopping scrap fiber pre- preg into individual pieces, which may be performed by breaking or splitting fiber pre-preg along and between the reinforcing fibers into individual pieces. Placing the resin infused fiber segments on the substrate includes moving an applicator over the substrate, and dispensing the resin infused fiber segments from the applicator onto the substrate as the applicator moves over the substrate. Arranging the resin infused fiber segments includes aligning the resin infused fiber segments as they are being dispensed from the applicator onto the substrate. Producing the resin infused fiber segments is performed by drawing continuous fiber pre-preg tape from the applicator, and chopping the pre-preg tape into the resin infused fiber segments as the resin infused fiber segments are being dispensed from the applicator onto the substrate. Dispensing the resin infused segments from the applicator includes dispensing a bandwidth of the resin infused fiber segments onto the substrate. Placing the resin infused fiber segments on the substrate is formed of by streaming the resin infused fiber segments from an applicator head onto the substrate. Streaming the resin infused fiber segments is performed by introducing the resin infused fiber segments into an airstream, and using the airstream to project the resin infused fiber segments onto the substrate. The resin infused fiber segments is performed after the resin infused fiber segments have been placed on the substrate. The method may further comprise applying resin to the substrate before the resin infused segments are placed on the substrate. The method may also comprise applying a resin on at least one end of each of the resin infused fiber segments before they are placed on the substrate.

According to another disclosed example, a method is provided of laying up composite material on a substrate the method comprises placing individual chopped fiber pre-preg segments on the substrate, and controlling the orientation of the pre-preg segments on the substrate. Placing the pre-preg segments on the substrate is performed by moving an applicator head over the substrate along a desired path, and dispensing the pre-preg segments from the applicator head onto the substrate as the applicator moves over the substrate. Controlling the orientation of the pre-preg segments is performed by aligning the pre-preg segments being dispensed from the applicator head. Controlling the orientation of the pre-preg segments includes changing the orientation of the pre-preg segments after the pre-preg segments have been placed on the substrate.

According to still another example, a composite laminate structure layup is provided comprising a plurality of layers of composite material, each of the layers including a plurality individual chopped fiber pre-preg segments having aligned fiber orientations. The fiber orientations of the chopped fiber pre-preg segments are substantially aligned with a non-linear load path through the composite laminate structure. Each of the individual chopped fiber pre-preg segments may have an aspect ratio of approximately <NUM>:<NUM>. The plurality of layers of composite material have a tailored cross- sectional shape and is contoured along a length of the layup.

According to still another disclosed example, apparatus is provided for laying up a composite structure. The apparatus comprises an applicator adapted to move over the surface of a substrate, and dispense at least one stream of substantially aligned chopped, resin infused fiber segments onto the surface of a substrate. The apparatus may also comprise a computer controlled manipulator for moving the applicator along a preselected path over the substrate. The applicator includes a supply of continuous resin infused fiber, and a chopper for chopping the continuous resin infused fiber into individual resin infused fiber segments. Applicator may further include an airstream generator for carrying the resin infused fiber segments from the applicator onto the substrate. The applicator may be adapted to simultaneously dispense multiple streams of substantially aligned chopped, resin infused fiber segments onto the substrate. The features, functions, and advantages can be achieved independently in various examples of the present disclosure or may be combined in yet other examples in which further details can be seen with reference to the following description and drawings.

In summary, according to one aspect there is provided a method of forming a composite feature having discontinuous reinforcement fibers, including producing a plurality of resin infused fiber segments each having unidirectional reinforcing fibers; placing the resin infused fiber segments on a substrate; and, arranging the resin infused fiber segments such that the reinforcing fibers of resin infused fiber segments placed on the substrate are substantially aligned relative to a desired reference orientation.

Advantageously the method wherein producing the resin infused fiber segments includes chopping scrap fiber pre-preg into individual pieces.

Advantageously the method wherein producing the resin infused fiber segments is performed by splitting fiber pre-preg along and between the reinforcing fibers into individual pieces.

Advantageously the method wherein placing the resin infused fiber segments on the substrate includes moving a applicator over the substrate, and dispensing the resin infused fiber segments from the applicator onto the substrate as the applicator moves over the substrate.

Advantageously the method wherein arranging the resin infused fiber segments includes aligning the resin infused fiber segments as they are being dispensed from the applicator onto the substrate.

Advantageously the method wherein producing the resin infused fiber segments is performed by drawing continuous fiber pre-preg tape from the applicator, and chopping the prepreg tape into the resin infused fiber segments as the resin infused fiber segments are being dispensed from the applicator onto the substrate.

Advantageously the method wherein dispensing the resin infused fiber segments from the applicator includes dispensing a bandwidth of the resin infused fiber segments onto the substrate.

Advantageously the method wherein placing the resin infused fiber segments on the substrate is performed by introducing the resin infused fiber segments into an airstream, and using the airstream to stream the resin infused fiber segments from an applicator head onto the substrate.

Advantageously the method wherein streaming the resin infused fiber segments is performed by introducing the resin infused fiber segments into an airstream, and using the airstream to project the resin infused fiber segments onto the substrate.

Advantageously the method wherein arranging the resin infused fiber segments is performed after the resin infused fiber segments have been placed on the substrate.

Advantageously the method further including applying resin to the substrate before the resin infused fiber segments are placed on the substrate.

Advantageously the method further comprising applying a resin on at least one end of each of the resin infused fiber segments before they are placed on the substrate.

According to another aspect there is provided a method of laying up composite material on a substrate, including placing individual chopped fiber pre-preg segments on the substrate; and, controlling an orientation of the pre-preg segments on the substrate.

Advantageously the method wherein placing the pre-preg segments on the substrate is performed by moving an applicator head over the substrate along a desired path, and dispensing the pre-preg segments from the applicator head onto the substrate as the applicator moves over the substrate.

Advantageously the method wherein controlling an orientation of the pre-preg segments is performed by substantially aligning the pre-preg segments being dispensed from the applicator head relative to a desired orientation.

Advantageously the method wherein controlling an orientation of the pre-preg segments includes changing the orientation of the pre-preg segments after the pre-preg segments have been placed on the substrate.

According to yet another aspect there is provided a composite laminate structure layup, including a plurality of layers of composite material, each of the layers including a plurality individual chopped fiber pre-preg segments having substantially aligned fiber orientations.

Advantageously the composite laminate structure layup wherein the fiber orientations of the chopped fiber pre-preg segments are substantially aligned with a non-linear load path through the composite laminate structure.

Advantageously the composite laminate structure layup wherein each of the individual chopped fiber pre-preg segments has an aspect ratio of approximately <NUM>:<NUM>.

Advantageously the composite laminate structure layup wherein the plurality of layers of composite material have a tailored cross-sectional shape and is contoured along a length of the layup.

According to still another aspect there is provided an apparatus for laying up a composite structure, including an applicator adapted to move over a substrate, and dispense at least one stream of substantially aligned chopped, resin infused fiber segments onto the substrate.

Advantageously the apparatus further comprising a computer controlled manipulator for moving the applicator along a preselected path over the substrate.

Advantageously the apparatus wherein the applicator includes a supply of continuous resin infused fiber, and a chopper for chopping the continuous resin infused fiber into individual resin infused fiber segments.

Advantageously the apparatus wherein the applicator includes an airstream generator for streaming the resin infused fiber segments from the applicator onto the substrate.

Advantageously the apparatus wherein the applicator is adapted to simultaneously dispense multiple streams of substantially aligned chopped, resin infused fiber segments onto the substrate.

The disclosed embodiments provide a method and apparatus for fabricating fiber reinforced resin laminates which provide increased control over laminate thickness, contour, width, cross-sectional profile and/or fiber orientation in local areas of a laminate structure. Referring to <FIG>, a composite feature <NUM> comprises discontinuous, resin infused fibers which may be in the form of chopped fiber pre-preg segments <NUM> having unidirectional reinforcing fibers <NUM>. Each of the fiber pre-preg segments <NUM> is elongate, having a length L that is greater than its width W. Each of the fiber pre-preg segments <NUM> may have an aspect ratio (L/W) in the range of approximately <NUM>:<NUM>, however this particular ratio is merely illustrative. The fiber pre-preg segments <NUM> may have other aspect ratios that are selected and/or optimized for the application, including structural requirements and the equipment used to position or place the segments <NUM>. In some embodiments, the fiber pre-preg segments <NUM> may have a length that is equal to or less than its width. For convenience and ease of description, the illustrative examples of composite features <NUM> that will be discussed below utilize unidirectional fiber pre-preg.

The disclosed embodiments are particularly well-suited for forming any of a variety of interlaminate features <NUM>, i.e. features <NUM> that are located between two continuous plies. However, the embodiments may also be employed to form composite features <NUM> that are partially or fully exposed, such as external features. In some applications, it may be useful or desirable to employ pre-preg segments <NUM> having fibers of differing lengths. Differing fiber lengths in a segment <NUM> may be achieved by, for example and without limitation, shaping the segment <NUM>, such as by chopping, in a manner that results in some of the fibers being longer or shorter than other fibers. Three illustrative examples of pre-preg segments <NUM> having shapes configured to produce reinforcing fibers of differing lengths are respectively shown in <FIG>. Other segment shapes resulting in differing fiber lengths are possible.

The reinforcing fibers <NUM> may comprise high-strength fibers, such as glass or carbon fibers, graphite, aromatic polyamide fiber, fiberglass, or another suitable reinforcement material. The resin matrix in which the fibers <NUM> are held may comprise thermoplastic or thermoset polymeric resins. Exemplary thermosetting resins may include allyls, alkyd polyesters, bismaleimides (BMI), epoxies, phenolic resins, polyesters, polyurethanes (PUR), polyureaformaldehyde, cyanate ester, and vinyl ester resin. Exemplary thermoplastic resins may include liquid-crystal polymers (LCP); fluoroplastics, including polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), and polytetrafluoroethylene-perfluoromethylvinylether (MFA); ketone-based resins, including polyetheretherketone; polyamides such as nylon-<NUM>/<NUM>, <NUM>% glass fiber; polyethersulfones (PES); polyamideimides (PAIS), polyethylenes (PE); polyester thermoplastics, including polybutylene terephthalate (PBT), polyethylene terephthalate (PET), and poly(phenylene terephthalates); polysulfones (PSU); or poly(phenylene sulfides) (PPS).

As used herein, "pre-preg" means fibers that have been impregnated with an uncured or partially cured resin which acts as a matrix to hold the fibers and which is flexible enough to be formed into a desired shape. The resin is then "cured," e.g., by the application of heat in an oven or an autoclave, to harden the resin into a strong, rigid, fiber-reinforced structure. In the case of pre-preg segments <NUM> having unidirectional fibers, the fibers extend substantially parallel to each other and, for purposes of this description, have a <NUM>° axial orientation, referred to hereinafter as the fiber direction or orientation of the pre-preg segments <NUM>.

The fiber pre-preg segments <NUM> may be laid up on a substrate <NUM> that may comprise a tool or an underlying continuous composite ply, using a suitable applicator system <NUM> which "steers" the fiber pre-preg segments <NUM> onto the substrate <NUM>. The applicator system <NUM> dispenses, places and aligns the fiber pre-preg segments <NUM> on the substrate <NUM> such that the direction of the fibers <NUM> in each of the fiber pre-preg segments <NUM> is substantially aligned in a desired orientation. For example, in the example shown in <FIG>, the fiber orientations of the fiber pre-preg segments <NUM> are substantially aligned with a curved center axis <NUM> forming a relatively tight contour <NUM>, with the fiber orientations of the segments <NUM> changing in direction along the contour <NUM> to remain substantially aligned in a desired orientation relative to the center axis <NUM>. The degree to which a chosen set of the fiber orientations of the pre-preg segments <NUM> are aligned with respect to a desired orientation, direction, or axis will depend upon the application. In some applications, the orientations of the pre-preg segments <NUM> may vary to some extent at one or more locations of a composite feature <NUM>. In fact, in some applications, some degree of variation of pre-preg segment orientation relative to a desired, reference orientation may be useful or desirable within a specified tolerance of variation.

In one embodiment, the applicator system <NUM> dispenses a serial stream <NUM> of pre-aligned fiber pre-preg segments <NUM>, which are then steered and placed onto substrate <NUM> by moving an applicator head (not shown) forming part of the applicator system <NUM> in a desired path over the substrate <NUM>, which in the illustrated example, is along, or parallel to the center axis <NUM>. Repeated passes of the applicator head over the substrate <NUM> result in successive layers or plies being laid up, each comprising aligned fiber pre-preg segments <NUM>. Thus, the composite feature <NUM> comprises multiple layers or plies of discontinuous fibers infused with resin.

Although not shown in <FIG>, as will become apparent later in the description, the disclosed embodiments may also be employed to fill voids or gaps (not shown) in composite structures as well as to form transitions (not shown) in laminate thicknesses by steering resin infused, discontinuous fibers such as chopped fiber pre-preg onto a substrate. By continuously steering the orientation of the fiber pre-preg segments <NUM> as they are being placed, structural properties of the laminate may be closely controlled on a local basis and therefore optimized. These void or gap fillers, as well as features such as bulk doubler areas that include transitions in laminate thicknesses will typically be interlaminar features (located between continuous plies), however in some applications as previously mentioned, it is possible that they may be exposed, external features.

Attention is now directed to <FIG> which illustrate use of the disclosed method and apparatus in connection with the fabrication of an aircraft fuselage <NUM> (<FIG>). The fuselage <NUM> comprises an outer skin <NUM> supported on internal framework <NUM> which includes barrel shaped frames <NUM> and longitudinally extending stringers <NUM>. The skin <NUM> may include one or more discontinuities, such as window openings <NUM>, cargo doors (not shown), etc. Fuselage pressure <NUM> results in a hoop load <NUM> being applied to the circumference <NUM> of the fuselage <NUM>, passing through the windows <NUM> or other openings in the skin <NUM>. Further, during flight, the crown <NUM> of the fuselage <NUM> is placed under tension <NUM>, while the belly <NUM> of the fuselage <NUM> is placed under compression <NUM>, resulting in shear loads <NUM> (<FIG>) that must traverse the window openings <NUM>. As shown in <FIG>, the hoop loads <NUM> and shear loads <NUM> are transferred around the perimeter of the window openings <NUM>. Consequently, the corners <NUM> around the window openings <NUM> are more highly stressed <NUM> because they must transfer both the hoop loads <NUM> and the shear loads <NUM>. As will be discussed below, the disclosed method and apparatus may be employed to layup composite doublers forming an interlaminar pad-up feature <NUM> around the window openings <NUM> that stiffens and strengthens the fuselage <NUM> around the window opening <NUM>, enabling the skin <NUM> to transfer the required loads through the corners <NUM>.

Referring particularly to <FIG>, the pad-up feature <NUM> is formed of a discontinuous fiber pre-preg comprising a plurality of steered fiber pre-preg segments <NUM> similar to the fiber pre-preg segments <NUM> previously discussed in connection with <FIG>. The fiber pre-preg segments <NUM> are steered as they are being placed on a tool (not shown) or underlying ply (not shown) so that their respective fiber orientations are substantially aligned with structural load paths, which in this example, is along or parallel to a contoured axis <NUM> at the corners <NUM>. The number of layers or plies of fiber pre-preg segments <NUM> that are steered onto the substrate <NUM> will vary with the application, and the desired thickness of the pad-up feature <NUM>. In some applications, it may be desirable to tailor the cross-sectional area of the pad-up feature <NUM> formed by steering the fiber pre-preg segments <NUM> onto the substrate <NUM>. For example, referring to <FIG>, the pad-up feature <NUM> shown in <FIG> and <FIG> may be laid up on one or more underlying full plies <NUM> and may be covered by one or more overlying full plies <NUM>. The pad-up feature <NUM> comprises a double taper <NUM> that is formed by laying down layers of the fiber pre-preg segments <NUM> that are successively narrower in width "W". Tapering of the pad-up feature <NUM> allows the resulting doubler to better conform to the full plies <NUM>, <NUM>.

For example, referring to <FIG>, the fiber pre-preg segments <NUM> may be steered and layered to form cross-sectional shapes that are suitable for filling gaps or voids <NUM> in a composite laminate, such as gaps <NUM> that may be formed in transitions in the thickness of a laminate structure <NUM>. In the example shown in <FIG>, the composite sandwich laminate structure <NUM> comprises a core <NUM> sandwiched between two composite plies <NUM>, <NUM>. A gap <NUM> is formed as the laminate structure <NUM> as it transitions from the core <NUM> to a solid laminate <NUM>. The gap <NUM> forms a structural discontinuity that may require strengthening and reinforcement in order to carry the required loads. The gap <NUM> may be filled with layers of the fiber pre-preg segments <NUM> to form a discontinuous fiber pre-preg filler feature <NUM>, which in this example, has a single taper <NUM>.

<FIG> illustrates the overall steps of a method of making a discontinuous fiber composite feature <NUM> by steering fiber pre-preg segments <NUM> onto a substrate <NUM>. Beginning at <NUM>, fiber pre-preg segments <NUM> are produced, as by, for example, chopping the fiber pre-preg to a desired dimensions and a desired aspect ratio. At <NUM>, discontinuous fiber plies are laid up by placing the fiber pre-preg segments <NUM> on a substrate <NUM> at step <NUM>, and at <NUM>, arranging the fiber pre-preg segments <NUM> such that the fiber orientations of the reinforcing fibers are aligned in a desired direction. As will be discussed below in more detail, the fiber pre-preg segments <NUM> may be placed on the substrate <NUM> using an applicator head which may also be used to steer the fiber pre-preg segments <NUM> and align them along load paths through a structure.

Attention is now directed to <FIG> which illustrate a portion of a frame section <NUM> having a generally Z-shaped cross-section. The frame section <NUM> may form a portion of a barrel shaped frame <NUM> such that used in the fuselage <NUM> shown in <FIG>. The frame section <NUM> includes upper and lower, oppositely extending flanges <NUM>, <NUM> connected by a web <NUM>. "Mousehole" openings <NUM> may be provided in the web <NUM> and flange <NUM> in order to provide clearance for longitudinally extending stringers <NUM> (<FIG>) in the fuselage <NUM>. The disclosed method and apparatus may be employed to form discontinuous resin infused fiber features <NUM> selectively reinforce portions of the frame section <NUM>, particularly in local areas that may experience higher stresses. Thus, one side of a central portion of the web <NUM> may be provided with a longitudinally extending, contoured, pad-up feature 30a formed by multiple layers of discontinuous fiber pre-preg comprising fiber pre-preg segments <NUM> that are steered onto the web <NUM> as the frame section <NUM> is being laid up.

In the illustrated embodiment, as is apparent from <FIG>, the pad-up feature 30a varies in cross-sectional shape along its length, however in other embodiments the cross-sectional shape of the pad-up feature 30a may be constant along its length. Similarly, pad-up features 30b, 30c comprising layers of fiber pre-preg segments <NUM>, such as chopped pre-preg, may be steered onto the web <NUM> in contoured patterns surrounding the mouseholes <NUM>. The pad-up features 30a, 30b, 30c may have any desired cross-sectional geometry selected to optimize local structural properties of the frame section <NUM>. Any of the pad-up features 30b, 30c may vary in cross-sectional size and/or shape along its length.

Attention is now directed to <FIG> which illustrates one embodiment of a system <NUM> that may be employed to form discontinuous, resin infused fiber features <NUM> of the type previously described, including local features of a structure that may require strengthening, stiffening and/or reinforcement. The system <NUM> broadly comprises an applicator head <NUM> that is adapted to place fiber pre-preg segments <NUM>, such as chopped pre-preg <NUM>, onto a substrate <NUM>, forming multiple layers or plies <NUM>. Applicator head <NUM> is displaced in X, Y and Z directions over the substrate <NUM> by an automated manipulator <NUM> which may comprise, for example and without limitation, a robot.

The manipulator <NUM> as well as the applicator head <NUM> are operated by a programmed CNC (computer numerically controlled) controller <NUM>. The applicator head <NUM> includes a pre-preg tape supply <NUM> which supplies unidirectional fiber pre-preg tape <NUM> through guides <NUM> to a chopper <NUM>. The chopper <NUM> may comprise a conventional cutter mechanism (not shown) operated in synchronization with the movement the applicator head <NUM> to chop the pre-preg fiber tape <NUM> into fiber pre-preg segments of the desired size and shape. The chopped fiber pre-preg segments <NUM> are fed <NUM> into an airstream <NUM> generated by airstream generators <NUM> on the applicator head <NUM>. The airstream <NUM> propels and places the pre-aligned fiber pre-preg segments <NUM> through a nozzle <NUM> onto the substrate <NUM> as the applicator head <NUM> over the substrate <NUM>. The pre-preg segments <NUM> are applied to the substrate <NUM> in the desired orientation as they contact and adhere to the substrate <NUM>. Orienting the segments <NUM> as they are being placed on the substrate <NUM> may eliminate the need to subsequently adjust the orientation of the segments <NUM>. A heater <NUM> may be provided on the applicator head <NUM> in order to heat the pre-preg fiber segments <NUM> and thereby increase their tackiness. This increased tack may assist in adhering and holding the pre-preg fiber segments <NUM> in a desired orientation on the substrate <NUM>. The heater <NUM> may comprise any of a variety of devices suitable for the application, including but not limited to a hot air blower, a conduction rod, a focused infrared heater or a laser, to name only a few. The heater <NUM> may generally heat the entire area of the segments <NUM>, or may produce a focused beam (not shown), such as a laser beam, that heats only a portion of a segment <NUM> until it is "sticky" enough to adhere to the substrate when it is placed.

The applicator head <NUM> may move from side-to-side (in the Y direction) in order to apply a width of the chopped pre-preg segments <NUM> in a desired orientation, while in other embodiments, the applicator head <NUM> may be used to make multiple linear passes over the substrate <NUM> in the X direction, in order to cover a desired width of the substrate <NUM> with the chopped fiber pre-preg segments <NUM> for each layer or ply <NUM>. While the applicator head <NUM> has been illustrated with airstream generators <NUM> to place the fiber pre-preg segments <NUM>, other means such as mechanical mechanisms may be employed to dispense, place and align the fiber pre-preg segments <NUM>, as the applicator head <NUM> moves across, and steers the fiber pre-preg segments <NUM> onto the substrate <NUM>. It should be particularly noted here that the system <NUM>, including the applicator head <NUM> discussed above are merely illustrative of a wide variety of equipment may be used to place and position the pre-preg segments <NUM>. The particular form of the system <NUM> that is used will depend upon the application, including specific structural requirements and the layup techniques that are employed. Moreover, the fabrication of the pre-preg segments <NUM> and equipment used to place and position the segments <NUM> on a substrate <NUM> may be implemented using a single machine, or several different machines.

<FIG> illustrates an alternate embodiment of the applicator head <NUM> shown in <FIG>, in which multiple rows of individual chopped fiber pre-preg segments <NUM> may be simultaneously dispensed, aligned in a desired orientation and placed by the applicator head <NUM> to form a bandwidth <NUM> of segments <NUM> with each pass of the applicator head <NUM> across the substrate <NUM>.

Referring now to Figures of <NUM>-<NUM>, the disclosed embodiments may be employed to layup layers or plies of discontinuous fiber pre-preg using scrap pre-preg <NUM> (<FIG>). Referring to <FIG>, as shown at step <NUM>, the scrap pre-preg <NUM> may be obtained from non-conforming/scrap parts or from scrap pre-preg resulting from other production processes. The scrap pre-preg <NUM> may have any of various shapes, as shown in <FIG>. At step <NUM> shown in <FIG>, the scrap pre-preg <NUM> is chopped into individual fiber pre-preg segments <NUM>, and following this chopping process, the segments <NUM> may have a random fiber orientation <NUM>, as shown in <FIG> and/or may have fibers of differing lengths. At step <NUM>, the chopped fiber pre-preg segments <NUM> are substantially aligned <NUM> with a desired fiber orientation as shown in <FIG>. At step <NUM>, the aligned fiber pre-preg segments <NUM> are fed to an applicator. At step <NUM> the applicator is used to dispense, steer and place the fiber pre-preg segments <NUM> on the substrate <NUM>, such that fiber orientations of the fiber pre-preg segments <NUM> are aligned in a desired direction.

The chopped fiber pre-preg <NUM> derived from scrap that is used in the disclosed method may be produced using any of several processes. For example, referring to <FIG>, scrap pre-preg <NUM> may be introduced into a chopper device <NUM> which may be similar to a blender, having rotating blades <NUM> inside an open vessel <NUM>. The blades <NUM> chop and break the scrap fiber pre-preg <NUM> into individual fiber pre-preg segments <NUM>, breaking or splitting the pre-preg along the lines of, and between the reinforcing fibers, resulting in the fiber pre-preg segments that have a random orientation <NUM>. With the scrap pre-preg having been chopped into individual fiber pre-preg segments <NUM>, the randomly oriented <NUM> fiber pre-preg segments <NUM> are aligned, for example by placing them in a shaker tray <NUM> having a series of parallel channels <NUM>. The shaker tray <NUM> is vibrated side-to-side <NUM>, causing the randomly oriented <NUM> fiber pre-preg segments <NUM> that have been loaded onto the tray <NUM> to fall into and align themselves within the channels <NUM>, resulting in rows <NUM> of aligned, fiber pre-preg segments <NUM>. The aligned rows <NUM> of the fiber pre-preg segments <NUM> may be fed to an applicator head <NUM> which dispenses, places and steers the fiber pre-preg segments <NUM> on the substrate <NUM> with desired fiber orientations.

<FIG> illustrate another embodiment of a method of steering chopped fiber prepreg segments <NUM> onto a substrate <NUM>. As shown in <FIG>, an applicator <NUM> is used to apply <NUM> a suitable resin <NUM> onto the substrate <NUM>, as the applicator <NUM> moves <NUM> across the substrate <NUM>. The resin <NUM> may be applied by spraying the resin <NUM> onto the substrate <NUM>, rolling the resin <NUM> onto the substrate <NUM> or using other application techniques. Next, as shown in <FIG>, chopped fiber pre-preg segments <NUM> are applied to the substrate <NUM> by a suitable applicator <NUM> that moves <NUM> over the substrate <NUM>. When initially applied in this manner, the fiber pre-preg segments <NUM> may have random orientations, as shown in <FIG>. Then, as shown in <FIG>, a fiber segment aligner <NUM> is moved <NUM> over the substrate <NUM> to align the fiber pre-preg segments <NUM> in a desired direction, which in this case, is along axis <NUM>. The fiber segment aligner <NUM> may use one or more mechanical devices to contact and realign the fiber pre-preg segments <NUM>, or alternatively may use noncontact techniques, such as an airstream (not shown) to achieve the desired segment alignment. As previously discussed, however, orienting the segments <NUM> as they are being initially placed on the substrate <NUM> may be desirable in some applications, since this technique may eliminate the need for the additional step of repositioning the segments <NUM> to the desired fiber orientations.

<FIG> illustrate an alternate technique for placing and aligning the fiber pre-preg segments <NUM> on the substrate <NUM>. Referring to <FIG>, a small quantity, such as a drop, of resin <NUM> is placed on one end <NUM> of each of the fiber pre-preg segments <NUM>. Then, as shown in <FIG>, the fiber segment <NUM> is placed on the substrate <NUM>. At this point, the fibers of the fiber segment <NUM> may not be aligned with the desired orientation, such as axis <NUM>. As shown in <FIG>, the fiber segment <NUM> is then rotated <NUM> so that the fiber orientation of the fiber segment <NUM> is aligned with the axis <NUM>. The orientation process may be performed using mechanical devices <NUM>, or using noncontact techniques such as streaming air over the substrate <NUM>.

Embodiments of the disclosure may find use in a variety of potential applications, particularly in the transportation industry, including for example, aerospace, marine, automotive applications and other application where composite structures may require local features requiring tight contours, thickness control and/or cross-sectional tailoring. Thus, referring now to <FIG>, embodiments of the disclosure may be used in the context of an aircraft manufacturing and service method <NUM> as shown in <FIG> and an aircraft <NUM> as shown in <FIG>. Aircraft applications of the disclosed embodiments may include, for example, without limitation, various parts of the airframe <NUM> such as frames, beams, spars, and stringers to name only a few. During pre-production, exemplary method <NUM> may include specification and design <NUM> of the aircraft <NUM> and material procurement <NUM>. During production, component and subassembly manufacturing <NUM> and system integration <NUM> of the aircraft <NUM> takes place. Thereafter, the aircraft <NUM> may go through certification and delivery <NUM> in order to be placed in service <NUM>. While in service by a customer, the aircraft <NUM> is scheduled for routine maintenance and service <NUM>, which may also include modification, reconfiguration, refurbishment, repair and so on.

As shown in <FIG>, the aircraft <NUM> produced by exemplary method <NUM> may include an airframe <NUM> with a plurality of systems <NUM> and an interior <NUM>. Examples of high-level systems <NUM> include one or more of a propulsion system <NUM>, an electrical system <NUM>, a hydraulic system <NUM>, and an environmental system <NUM>. Any number of other systems may be included. Although an aerospace example is shown, the principles of the disclosure may be applied to other industries, such as the marine and automotive industries.

Systems and methods embodied herein may be employed during any one or more of the stages of the production and service method <NUM>. For example, components or subassemblies corresponding to production process <NUM> may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft <NUM> is in service. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages <NUM> and <NUM>, for example, by substantially expediting assembly of or reducing the cost of an aircraft <NUM>. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft <NUM> is in service, for example and without limitation, to perform maintenance and service <NUM>, or to carry out repair or refurbishment of structures at any time during the service life of the aircraft <NUM>.

Claim 1:
A method of forming a composite feature (<NUM>) having discontinuous reinforcement fibers, comprising:
producing a plurality of resin infused fiber segments (<NUM>) each having unidirectional reinforcing fibers (<NUM>), wherein the fibers extend substantially parallel to each other, and wherein producing the resin infused fiber segments comprises chopping fiber pre-preg (<NUM>) into individual resin infused fiber segments;
placing the resin infused fiber segments on a substrate (<NUM>) by introducing the resin infused fiber segments into an airstream and using the airstream to stream the resin infused fiber segments from an applicator (<NUM>) onto the substrate; and
after the resin infused fiber segments have been placed on the substrate, rotating the resin infused fiber segments so as to arrange the resin infused fiber segments such that the reinforcing fibers of the resin infused fiber segments placed on the substrate are substantially aligned relative to a desired reference orientation.