METHOD FOR FORMING A COMPOSITE ELEMENT HAVING DISCONTINUOUS REINFORCING FIBERS, AND APPARATUS FOR DEPOSITING A COMPOSITE STRUCTURE

Abstract

1 / 1 ABSTRACT “METHOD FOR FORMING A COMPOSITE ELEMENT THAT HAS DISCONTINUOUS REINFORCEMENT FIBERS, DEPOSITION OF LAMINATED COMPOSITE STRUCTURE, AND APPARATUS FOR DEPOSITING A COMPOUND STRUCTURE†Interlaminar elements of a composite structure are deposited by placing and directing individual segments of chopped fiber pre-preg onto a substrate.

Description

METHOD FOR FORMING A COMPOSITE ELEMENT HAVING DISCONTINUOUS REINFORCING FIBERS, AND APPARATUS FOR DEPOSITING A COMPOSITE STRUCTURE BACKGROUND INFORMATION 1. Field

[001] The present description relates generally to the manufacture of composite laminate structures using fiber prepreg, and deals, more particularly, with a method and apparatus for forming composite structural elements by directing discontinuous fiber prepreg onto a substrate with desired fiber orientations. 2. Basis

[002] The strength, stiffness, and load transfer characteristics of a composite laminate structure can be utilized by controlling fiber orientation during the deposition process. Conventional composite laminates can be deposited using pre-preg tapes, trailers, or general merchandise, or by employing automated fiber placement equipment or manual placement techniques to deposit 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 to optimize its structural properties and / or account for higher local stresses.

[003] The ability to control local fiber thickness / orientation is limited using current manufacturing processes. For example, automated fiber placement equipment can be used to direct continuous fiber across the substrate, but the bending radius that can be achieved is limited, thus making it difficult to control fiber orientation in local areas with tight contours. Achieving Petition 870200029237, dated 04 / 03 / 2020, page 9 / 106 / 28 tight control over fiber thickness and / or orientation in local areas of laminate can also be expensive and time-consuming.

[004] Consequently, there is a need for a method and apparatus to control composite laminate thickness and / or fiber orientation in local areas of a laminate, in order to optimize the structural properties of the laminate. There is also a need for a method and apparatus of the type mentioned above, which is efficient, highly controllable and which can reduce labor and material costs. SUMMARY

[005] The embodiments described provide a method and apparatus for manufacturing composite laminate elements that provide increased control over element thickness and / or fiber orientation in local areas of a laminate structure such as in tight contours and / or within laminate thickness transitions. Composite material can be deposited so that fiber orientations are substantially aligned continuously with load vectors in selected local areas of a laminate, thereby optimizing the structural properties of the laminate.

[006] The amount of composite material required to provide local areas of a laminated structure with desired structural properties can be reduced by forming the composite elements using prepreg scrap derived from other products / processes. Recycling prepreg scrap for use in the described method can reduce material costs, thus optimizing the buy-to-fly ratio for aircraft applications in the embodiments. The embodiments allow composite material in the form of discontinuous fiber prepreg to be directed onto a substrate to achieve desired fiber orientations.

[007] The use of discontinuous fiber prepreg allows for greater Petition 870200029237, dated 03 / 04 / 2020, p. 10 / 106 / 28 control over variations in laminate thickness in local areas of the laminate, while allowing for local tailored selection of laminate thickness in three dimensions to provide smooth transitions between different elements of a laminated structure. Furthermore, the use of discontinuous fiber pre-preg allows for the formation of duplicators or other deposits that have tight contours and / or tapered edges to achieve smooth load transitions within a structure. Also, the use of discontinuous fiber pre-preg can result in composite elements that have a higher fiber content.

[008] According to one embodiment described, a method is provided for forming a composite element having discontinuous reinforcing 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 so that the reinforcing fibers of the resin-infused fiber segments placed on the substrate are substantially aligned with respect to the desired reference orientation. Producing the resin-infused fiber segments includes chopping fiber pre-preg scrap into individual pieces, which can be accomplished by breaking or splitting fiber pre-preg along and between the reinforcing fibers into individual pieces.Placing resin-infused fiber segments onto the substrate involves moving an applicator over the substrate and dispensing the resin-infused fiber segments from the applicator onto the substrate as the applicator moves across the substrate. Arranging the resin-infused fiber segments involves aligning the resin-infused fiber segments as they are being dispensed from the applicator onto the substrate. The production of resin-infused fiber segments is accomplished by stretching continuous fiber pre-preg tape from the applicator and chopping the pre-preg tape into fiber segments. Petition 870200029237, dated 04 / 03 / 2020, page 11 / 106 / 28 infused with resin when the resin-infused fiber segments are being dispensed from the applicator onto the substrate. Dispensing the resin-infused fiber segments from the applicator includes dispensing a bandwidth of the resin-infused fiber segments onto the substrate. The placement of the resin-infused fiber segments onto the substrate is formed by transferring the resin-infused fiber segments from an applicator head onto the substrate. The transfer of the resin-infused fiber segments is performed by introducing the resin-infused fiber segments into an air stream and using the air stream to project the resin-infused fiber segments onto the substrate. The resin-infused fiber segments are transformed 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 fiber segments are placed on the substrate. The method may also comprise applying resin to at least one end of each of the resin-infused fiber segments before they are placed on the substrate.

[009] According to another embodiment described, a method is provided for depositing composite material onto a substrate, the method comprising placing individual segments of chopped fiber prepreg onto the substrate and controlling the orientation of the prepreg segments onto the substrate. The placement of the prepreg segments onto the substrate is accomplished by moving an applicator head over the substrate along a desired path and dispensing the prepreg segments from the applicator head onto the substrate as the applicator moves over the substrate. Controlling the orientation of the prepreg segments is accomplished by aligning the prepreg segments being dispensed from the applicator head. Controlling the orientation of the prepreg segments includes changing the orientation of the prepreg segments after the prepreg segments Petition 870200029237, dated 04 / 03 / 2020, page 12 / 106 / 28 have been placed on the substrate.

[0010] According to yet another embodiment, a laminated composite structure deposition is provided comprising a plurality of composite material layers, each of the layers including a plurality of individual chopped fiber prepreg segments that have aligned fiber orientations. The fiber orientations of the chopped fiber prepreg segments are substantially aligned with a non-linear load path through the laminated composite structure. Each of the individual chopped fiber prepreg segments may have an aspect ratio of approximately 6:1. The plurality of composite material layers has a tailored cross-sectional shape and is profiled along a length of the deposition.

[0011] According to yet another embodiment described, an apparatus is provided for depositing a composite structure. The apparatus comprises an applicator adapted for moving over the surface of a substrate and dispensing 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 pre-selected 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. The applicator may further include an air current generator for carrying the resin-infused fiber segments from the applicator onto the substrate.The applicator can be adapted to simultaneously dispense several streams of substantially aligned resin-infused fiber segments applied to the substrate. The elements, functions, and advantages can be achieved independently in various embodiments of the present description, or can be combined in still other embodiments where other details are provided. Petition 870200029237, dated 03 / 04 / 2020, p. 13 / 106 / 28 can be viewed with reference to the description and drawings below.

[0012] In summary, according to one aspect of the invention, a method is provided for forming a composite element having discontinuous reinforcing fibers, which includes 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 so that the reinforcing fibers of resin-infused fiber segments placed on the substrate are substantially aligned with respect to the desired reference orientation.

[0013] Advantageously, the method of producing resin-infused fiber segments involves chopping up pre-preg fiber scrap into individual pieces.

[0014] Advantageously, the method of producing resin-infused fiber segments is carried out by splitting pre-preg fiber along and between the reinforcing fibers into individual pieces.

[0015] Advantageously, the method of placing resin-infused fiber segments onto the substrate involves 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.

[0016] Advantageously, the method of arranging the resin-infused fiber segments includes aligning the resin-infused fiber segments as they are being dispensed from the applicator onto the substrate.

[0017] Advantageously, the method in which the production of resin-infused fiber segments is carried out by stretching a continuous strip of pre-preg fiber from the applicator and chopping the pre-preg strip into resin-infused fiber segments when the fiber segments Petition 870200029237, dated 04 / 03 / 2020, page 14 / 106 / 28 resin-infused fiber segments are being dispensed from the applicator onto the substrate.

[0018] Advantageously, the method of dispensing resin-infused fiber segments from the applicator includes dispensing a bandwidth of resin-infused fiber segments onto the substrate.

[0019] Advantageously, the method in which the placement of resin-infused fiber segments onto the substrate is carried out by introducing the resin-infused fiber segments into an air stream and using the air stream to project the resin-infused fiber segments from an applicator head onto the substrate.

[0020] Advantageously, the method in which the transfer of resin-infused fiber segments is carried out by introducing the resin-infused fiber segments into an air stream and using the air stream to project the resin-infused fiber segments onto the substrate.

[0021] Advantageously, the method in which the arrangement of the resin-infused fiber segments is carried out after the resin-infused fiber segments have been placed on the substrate.

[0022] Advantageously, the method additionally includes applying resin to the substrate before the resin-infused fiber segments are placed on the substrate.

[0023] Advantageously, the method further comprises applying a resin to at least one end of each of the resin-infused fiber segments before they are placed on the substrate.

[0024] According to another aspect of the invention, a method is provided for depositing composite material onto a substrate, which includes placing individual segments of chopped fiber pre-preg onto the substrate and controlling the orientation of the pre-preg segments onto the substrate. Petition 870200029237, dated 04 / 03 / 2020, page 15 / 106 / 28

[0025] Advantageously, the method in which the placement of the pre-preg segments onto the substrate is carried out 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.

[0026] Advantageously, the method in which the control of an orientation of the pre-preg segments is achieved substantially by aligning the pre-preg segments being dispensed from the applicator head with respect to a desired orientation.

[0027] Advantageously, the method in which controlling the orientation of the pre-preg segments involves changing the orientation of the pre-preg segments after the pre-preg segments have been placed on the substrate.

[0028] According to yet another aspect of the invention, a composite laminated structure deposition is provided which includes a plurality of layers of composite material, each of the layers including a plurality of individual chopped fiber prepreg segments having substantially aligned fiber orientations.

[0029] Advantageously depositing the laminated composite structure in which the fiber orientations of the chopped pre-preg segments are substantially aligned with a non-linear load path through the laminated composite structure.

[0030] Advantageously depositing a laminated composite structure in which each of the individual chopped fiber prepreg segments has an aspect ratio of approximately 6:1.

[0031] Advantageously depositing a laminated composite structure in which the plurality of composite material layers have a custom-made cross-sectional shape and are profiled along a length of the deposition. Petition 870200029237, dated 04 / 03 / 2020, page 16 / 106 / 28

[0032] According to yet another aspect of the invention, an apparatus is provided for depositing a composite structure which includes an applicator adapted for moving over a substrate and dispensing at least one stream of substantially aligned chopped resin-infused fiber segments onto the substrate.

[0033] Advantageously, the apparatus additionally comprises a computer-controlled manipulator for moving the applicator along a pre-selected path over the substrate.

[0034] Advantageously, the apparatus in which 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.

[0035] Advantageously, the device in which the applicator includes an air current generator to transfer resin-infused fiber segments from the applicator onto the substrate.

[0036] Advantageously, the apparatus in which the applicator is adapted to simultaneously dispense several streams of substantially aligned, chopped resin-infused fiber segments onto the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The innovative elements considered characteristic of the illustrative embodiments are described in the appended claims. The illustrative embodiments, however, as well as a preferred mode of use and other objectives and advantages thereof, will be better understood by reference to the detailed description that follows of an illustrative embodiment of the present description when read in conjunction with the accompanying drawings, in which: Figure 1 is an illustration of a combined and diagrammatic block of discontinuous fiber prepreg being applied to a substrate. Petition 870200029237, dated 03 / 04 / 2020, p. 17 / 106 / 28 along a tight outline.

[0038] Figure 1A is an illustration of a plan view showing one shape of the pre-preg segments.

[0039] Figure 1B is an illustration of a plan view showing another form of the pre-preg segments.

[0040] Figure 1C is an illustration of a plan view showing another additional form of the pre-preg segments.

[0041] Figure 2 is an illustration of a perspective view of a barrel section of an aircraft fuselage showing loads applied to the fuselage.

[0042] Figure 3 is an illustration of a diagrammatic view of one of the window openings in the fuselage of Figure 2, also showing load vectors around the window opening.

[0043] Figure 4 is an illustration of an elevation view of one of the window openings in the fuselage shown in Figure 2, also showing a surrounding duplicator formed of discontinuous fiber pre-preg.

[0044] Figure 5 is an illustration of the area indicated as “figure 5” in figure 4.

[0045] Figure 6 is an illustration of a sectional view taken along line 6-6 in Figure 5.

[0046] Figure 7 is an illustration of a cross-sectional view of a composite structure showing a discontinuous interlaminar fiber infill and transition in an interstice within the thickness of a laminated composite structure.

[0047] Figure 8 is an illustration of a flowchart of a method for depositing interlaminar composite elements using the described method.

[0048] Figure 9 is an illustration of a perspective view of a portion of a section of an aircraft fuselage structure, in lines Petition 870200029237, dated 04 / 03 / 2020, page 18 / 106 / 28 interrupted indicating areas where interlaminar structural elements can be formed using the described method.

[0049] Figure 10 is an illustration of a sectional view taken along line 10-10 in Figure 9 showing an interlaminar structural element, shaped using the method described.

[0050] Figure 11 is an illustration of a sectional view taken along line 11-11 in Figure 9.

[0051] Figure 12 is an illustration of a combined block and diagrammatic view of a system for placing discontinuous fiber prepregs.

[0052] Figure 13 is an illustration of a combined block and diagrammatic view of an alternative embodiment of the system for placing discontinuous fiber prepreg.

[0053] Figure 14 is an illustration of a flowchart of a method for depositing composite laminates using discontinuous fiber prepreg derived from prepreg scrap.

[0054] Figure 15 is an illustration of a plan view showing various forms of pre-preg scrap that can be used in the method shown in Figure 14.

[0055] Figure 16 is an illustration of a plan view showing randomly oriented fiber prepreg segments formed by chopping the scrap shown in Figure 15.

[0056] Figure 17 is an illustration of a plan view similar to Figure 16, but showing the fiber orientations of the fiber pre-preg segments that have been aligned in preparation for application to a substrate.

[0057] Figure 18 is an illustration of a diagrammatic view of a method for converting fiber pre-preg scrap into segments and preparing it for application to a substrate.

[0058] Figure 19A is an illustration of a diagrammatic side view of an applicator applying resin onto a substrate. Petition 870200029237, dated 04 / 03 / 2020, page 19 / 106 / 28

[0059] Figure 19B is an illustration of a plan view of the resin applied to the substrate shown in Figure 19A.

[0060] Figure 20A is an illustration of a diagrammatic side view showing chopped fiber pre-preg segments being applied over the resin shown in Figure 19B.

[0061] Figure 20B is an illustration of a plan view of the substrate in Figure 20A, showing the random orientation of the chopped fiber pre-preg segments.

[0062] Figure 21A is an illustration of a diagrammatic side view showing the fiber segment aligner aligning chopped fiber pre-preg segments.

[0063] Figure 21B is an illustration of a plan view showing the chopped fiber pre-preg segments of Figure 21A that have been aligned by the fiber segment aligner.

[0064] Figure 22A is an illustration of a side view of a chopped fiber prepreg segment with a drop of resin placed on one end thereof.

[0065] Figure 22B is an illustration of a bottom view of the chopped fiber pre-preg segment shown in Figure 22A.

[0066] Figure 23A is an illustration of a side view of the chopped fiber prepreg segment of Figure 22A that has been placed on a substrate, but before its rotation.

[0067] Figure 23B is an illustration of a plan view of the chopped fiber prepreg segment shown in Figure 23A.

[0068] Figure 24A is an illustration of a side view similar to Figure 23A, but after the chopped fiber pre-preg segment has been rotated.

[0069] Figure 24B is an illustration similar to Figure 23B, but showing the fiber pre-preg segment having been rotated, the position of Petition 870200029237, dated 04 / 03 / 2020, page 20 / 106 / 28 segment of chopped fiber pre-preg before rotation being indicated in spectrum.

[0070] Figure 25 is an illustration of a flowchart of aircraft production and service methodology.

[0071] Figure 26 is an illustration of a block diagram of an aircraft. DETAILED DESCRIPTION

[0072] The embodiments described provide a method and apparatus for manufacturing fiber-reinforced resin laminates that provides increased control over laminate thickness, contour, width, cross-sectional profile, and / or fiber orientation in local areas of a laminated structure. Referring to Figure 1, a composite element 30 comprises discontinuous resin-infused fibers that may be in the form of chopped fiber prepreg segments 32 having unidirectional reinforcing fibers 25. Each of the fiber prepreg segments 32 is elongated having a length L that is greater than its width W. Each of the fiber prepreg segments 32 may have an aspect ratio (L / W) in the range of approximately 6:1; however, this particular ratio is merely illustrative.Fiber prepreg segments 32 may have other element relationships that are selected and / or optimized for the application, including structural requirements and the equipment used to position or place the segments 32. In some embodiments, the fiber prepreg segments 32 may have a length that is equal to or less than their width. For convenience and ease of description, the illustrative examples of composite elements 30 that will be discussed below utilize unidirectional fiber prepreg. However, it should be noted here that the principles of the embodiments described can be employed to form composite elements 30 that utilize other types of fiber prepreg segments 32, including resins that are reinforced with fibers that have various orientations. Petition 870200029237, dated 04 / 03 / 2020, page 21 / 106 / 28 of fiber such as, for example, and without limitation, bidirectional fibers that are woven (pre-preg cloth) and / or otherwise combined in a manner to suit a particular application.

[0073] The embodiments described are particularly well suited for forming any of a variety of interlaminated elements 30, that is, elements 30 that are located between two continuous plies. However, the embodiments can also be employed to form composite elements 30 that are partially or completely exposed, such as external elements. In some applications it may be useful or desirable to employ pre-preg segments 32 that have fibers of different lengths. Different fiber lengths in a segment 32 can be achieved, for example, without limitation, by shaping the segment 32 such as by chopping, in a manner that results in some of the fibers being either longer or shorter than other fibers. Three illustrative examples of pre-preg segments 32 that have shapes configured to produce reinforcing fibers of different lengths are shown respectively in figures 1A-1C.Other segment shapes resulting in different fiber lengths are possible. As mentioned earlier, although the 32 pre-preg segments shown in Figures 1A-1C employ unidirectional reinforcing fibers, other fiber arrangements are possible, such as woven fibers (not shown).

[0074] Reinforcing fibers 25 may comprise high-strength fibers such as glass or carbon fibers, graphite, aromatic polyamide fiber, glass fiber, or other suitable reinforcing material. The resin matrix in which the fibers 25 are held may comprise thermoplastic or thermally curing polymeric resins. Thermally curing resins taken as examples may include allyls, alkyd polyesters, bismaleimides (BMI), epoxies, phenolic resins, polyesters, polyurethanes (PUR), polyurea-formaldehyde, cyanate ester, and vinyl ester resin. Resins Petition 870200029237, dated 04 / 03 / 2020, page 22 / 106 / 28 thermoplastics taken as examples may include liquid crystal polymers (LCP), fluoroplastics, which include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), and polytetrafluoroethylene perfluoromethyl vinyl ether (MFA), ketone-based resins including polyetheretherketone; polyamides such as nylon-6 / 6, 30% glass fiber, polyethersulfones (PES), polyamideimides (PAIS), polyethylenes (PE); thermoplastic polyester, including polybutylene terephthalate (PBT), polyethylene terephthalate (PET) and poly(phenylene terephthalates); polysulfones (PSU) or poly(phenylene sulfides) (PPS).

[0075] As used herein, “pre-preg” means fibers that have been impregnated with an uncured or partially cured resin that acts as a matrix to hold the fibers and that is flexible enough to be conformed into a desired shape. The resin is then “cured,” for example, by applying heat in an oven or autoclave, to harden the resin into a strong, rigid, fiber-reinforced structure. In the case of pre-preg segments 32 that have unidirectional fibers, the fibers extend substantially parallel to each other and for the purposes of this description have an axial orientation of 0°, referred to hereafter as the fiber direction or orientation of the pre-preg segments 32.Where pre-preg segments 32 are used that have several sets of fiber orientations, typically one or more of these sets of fiber orientations will be used to align and orient the segments 32 when they are being placed on a substrate 34 during the deposition process.

[0076] Fiber prepreg segments 32 can be deposited onto a substrate 34 which may comprise a tool or an underlying continuous composite sheet, using a suitable applicator system 38 that “directs” the fiber prepreg segments 32 onto the substrate 34. The applicator system 38 dispenses, places and aligns the prepreg segments of Petition 870200029237, dated 04 / 03 / 2020, page 23 / 106 / 28 fiber 32 on the substrate 34, so that the direction of the fibers 25 in each of the fiber prepreg segments 32 is substantially aligned in a desired orientation. For example, in the example shown in Figure 1, the fiber orientations of the fiber prepreg segments 32 are substantially aligned with a curved central geometric axis 36 that forms a relatively tight contour 35, with the fiber orientations of the segments 32 changing direction along the contour 35 to remain substantially aligned in a desired orientation relative to the central geometric axis 36. The degree to which a chosen set of fiber orientations of the prepreg segments 32 are aligned with respect to a desired orientation, direction, or geometric axis will depend on the application.In some applications, the orientations of the pre-preg segments 32 may vary to some extent in one or more locations of a composite element 30. In fact, in some applications some degree of variation in pre-preg segment orientation relative to a desired reference orientation may be useful or desirable within a specified variation tolerance.

[0077] In one embodiment, the applicator system 38 dispenses a serial stream 40 of pre-aligned fiber prepreg segments 32 which are then directed and placed onto the substrate 34 by moving an applicator head (not shown) that is part of the applicator system 38 along a desired path over the substrate 34 which, in the example illustrated, is along or parallel to the central geometric axis 36. Repeated passes of the applicator head over the substrate 34 result in successive layers or plies being deposited, each comprising aligned fiber prepreg segments 32. Thus, the composite element 30 comprises several layers or plies of discontinuous fibers infused with resin.

[0078] Although not shown in Figure 1, as will become evident later in the description, the modalities described may also be Petition 870200029237, dated 04 / 03 / 2020, page 24 / 106 / 28 employed to fill voids or interstices (not shown) in composite structures, as well as to form transitions (not shown) in laminate thicknesses by directing discontinuous resin-infused fibers such as chopped fiber pre-preg, onto a substrate. By continuously directing the orientation of the fiber pre-preg segments 32 as they are being placed, the structural properties of the laminate can be closely controlled on a local basis and thus optimized. These void or interstitial fillers, as well as elements such as bulky doubling areas that include transitions in laminate thicknesses, will typically be interlaminar elements located between continuous plies; however, in some applications, as mentioned above, it is possible that they may be exposed external elements.

[0079] Attention is now directed to figures 2-6 which illustrate the use of the described method and apparatus in connection with the manufacture of an aircraft fuselage 44 (figure 2). The fuselage 44 comprises an outer skin 46 supported on an inner frame 45 which includes barrel-shaped structures 64 and longitudinally extending stringers 47. The skin 46 may include one or more discontinuities such as window openings 42, cargo doors (not shown), etc. The pressure on the fuselage 49 results in an arc load 50 that is applied to the circumference 55 of the fuselage 44 passing through the windows 48 or other openings in the skin 46. Furthermore, during flight, the crown 54 of the fuselage 44 is placed under tension 75 while the belly 56 of the fuselage 44 is placed under compression 77, resulting in shear loads 52 (figure 3) that must pass through the window openings 42.As shown in Figure 3, the arch loads 50 and the shear loads 52 are transferred around the perimeter of the window openings 42. Consequently, the corners 58 around the window openings 42 are more highly stressed 59, since they must transfer both loads. Petition 870200029237, dated 04 / 03 / 2020, page 25 / 106 / 28 of jump 50 and shear loads 52. As will be discussed below, the method and apparatus described can be employed to deposit composite duplicators that form an interlaminar shim element 30 around the window openings 42 that stiffens and reinforces the fuselage 44 around the window opening 42, enabling the skin 46 to transfer the required loads through the corners 58.

[0080] Referring particularly to Figure 5, the wedge element 30 is formed of a discontinuous fiber prepreg comprising a plurality of oriented fiber prepreg segments 32 similar to the fiber prepreg segments 32 previously discussed in connection with Figure 1. The fiber prepreg segments 32 are oriented when they are being placed over an underlying tool (not shown) or canvas (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 profiled geometric axis 36 at the corners 58. The number of layers or canvases of fiber prepreg segments 32 that are oriented over the substrate 34 will vary with the application and the desired thickness of the wedge element 30.In some applications it may be desirable to tailor the cross-sectional area of ​​the wedge element 30 formed by directing two fiber pre-preg segments 30 onto the substrate 34. For example, referring to Figure 6, the wedge element 30 shown in Figures 4 and 5 may be deposited on one or more underlying full plies 60 and may be covered by one or more overlying full plies. The wedge element 30 comprises a double taper 64 which is formed by depositing layers of fiber pre-preg segments 32 that are successively narrower in width W. Tapering of the wedge element 30 allows the resulting duplicator to conform better to the full plies 60, 62.

[0081] For example, referring to figure 7, two segments of Petition 870200029237, dated 04 / 03 / 2020, page 26 / 106 / 28 pre-preg fiber 32 can be directed and deposited to form cross-sectional shapes that are suitable for filling gaps or voids 52 in a composite laminate, such as gaps 82 that may be formed at transitions in the thickness of a laminated structure 85. In the example shown in Figure 7, the composite sandwich laminated structure 85 comprises a core 86 sandwiched between two composite plies 60, 62. A gap 82 is formed as the laminated structure 85 changes from the core 86 to a solid laminate 87. The gap 82 forms a structural discontinuity that may require increased strength and reinforcement to carry the required loads. The interstitium 82 can be filled with layers of fiber prepreg segments 32 to form a discontinuous fiber prepreg filler element 30 which, in this example, has a single taper 84.

[0082] Figure 8 illustrates the overall steps of a method for making a discontinuous fiber composite element 30 by directing fiber prepreg segments 32 onto a substrate 34. Starting at 66, fiber prepreg segments 32 are produced by, for example, chopping the fiber prepreg to a desired dimension and aspect ratio. At 68, discontinuous fiber plies are deposited by placing the fiber prepreg segments 32 onto a substrate 34 at step 70 and at 72 arranging the fiber prepreg segments 32 so that the fiber orientations of the reinforcing fibers are aligned in a desired direction. As will be discussed in more detail below, the fiber prepreg segments 32 can be placed on the substrate 34 using an applicator head which can also be used to direct the fiber prepreg segments 32 and align them along load paths through a structure.

[0083] Attention is now directed to figures 9-11 which illustrate a portion of the cross-section of a 74 frame section which has a section Petition 870200029237, dated 04 / 03 / 2020, page 27 / 106 / 28 transversely shaped in a generic Z shape. The frame section 74 can form a portion of a barrel-shaped structure 65 so that it is used in the fuselage 44 shown in Figure 1. The frame section 74 includes upper and lower flanges that extend in opposite directions 76, 78 connected by a screen 80. “Rat hole” openings 82 can be provided in the screen 80 and flange 76 to provide interstices for longitudinally extending stringers 47 (Figure 2) in the fuselage 44. The method and apparatus described can be employed to form discontinuous resin-infused fiber elements 30 to selectively reinforce portions of the frame section 74, particularly in local areas that may experience higher stresses.Thus, one side of a central portion of the screen 80 may be provided with a profiled wedge element, which extends longitudinally 30a, formed by several discontinuous layers of fiber pre-preg comprising fiber pre-preg segments 32 and are directed over the screen 80 when the reinforcement section 74 is being deposited.

[0084] In the illustrated embodiment, as is evident from Figures 10 and 11, the wedge element 30a varies in cross-sectional shape along its length; however, in other embodiments, the cross-sectional shape of the wedge element 30a may be constant along its length. Similarly, wedge elements 30b, 30c comprising layers of fiber pre-preg segments 32, such as chopped pre-preg, may be directed over the screen 80 in profiled patterns surrounding the “rat holes” 82. Wedge elements 30a, 30b, and 30c may have any desired cross-sectional geometry, selected to optimize local structural properties of the frame section 74. Any of the wedge elements 30b, 30c may vary in cross-sectional size and / or shape along their length.

[0085] Attention is now directed to figure 12 which illustrates a Petition 870200029237, dated 04 / 03 / 2020, page 28 / 106 / 28 embodiment of a system 88 that can be employed to form discontinuous elements of resin-infused fiber 30, of the type previously described, which includes local elements of a structure that may require strengthening, stiffening and / or reinforcement. The system 88 broadly comprises an applicator head 90 that is adapted to place fiber pre-preg segments 32, such as chopped pre-preg 32, onto a substrate 34, forming several layers or plies 96. The applicator head 90 is placed in X, Y and Z directions onto the substrate 34 by means of an automated manipulator 92 which may comprise, for example, and without limitation, a robot.

[0086] The manipulator 92, as well as the applicator head 90, are operated by a CNC (computer numerically controlled) programmed controller 94. The applicator head 90 includes a prepreg tape supply 98 that supplies the unidirectional fiber prepreg tape 100 through guides 102 to a chopper 103. The chopper 103 may comprise a conventional cutting mechanism (not shown) operated in synchronization with the movement of the applicator head 90 to chop the fiber prepreg tape 100 into fiber prepreg segments of the desired size and shape. The chopped fiber pre-preg segments 32 are fed 40 into an air stream 104 generated by air stream generators 106 over the applicator head 90. The air stream 104 propels and places the pre-aligned fiber pre-preg segments 32 through a nozzle 108 onto the substrate 34 as the applicator head 90 over the substrate 34.Prepreg segments 32 are applied to the substrate 34 in the desired orientation when they contact and adhere to the substrate 34. Orienting the segments 32 when they are being placed on the substrate 34 can eliminate the need to subsequently adjust the orientation of the segments 32. A heater 105 can be provided on the applicator head 30 to heat the fiber prepreg segments 32, thereby increasing their tackiness. This increased tack can be helpful. Petition 870200029237, dated 04 / 03 / 2020, page 29 / 106 / 28 to adhere and support the fiber pre-preg segments 32 in a desired orientation on the substrate 34. The heater 105 may comprise any of a variety of devices suitable for the application, including, but not limited to, a hot air blower and a driving rod, a focused infrared heater, or a laser, to name just a few. The heater 105 may, generically, heat the entire area of ​​the segments 32 or may produce a focused beam (not shown) such as a laser beam that heats only a portion of a segment 32 until it is sticky enough to adhere to the substrate when it is placed.

[0087] The applicator head 90 can move from side to side (in the Y direction) to apply a width of the applied pre-preg segments 32 in a desired orientation, while in other embodiments the applicator head 90 can be used to make several linear passes over the substrate 34 in the X direction to cover a desired width of the substrate 34 with the applied fiber pre-preg segments 32 for each layer or canvas 96. Although the applicator head 90 has been illustrated with air current generators 106 to place the fiber pre-preg segments 32, other means such as mechanical mechanisms can be employed to dispense, place and align the fiber pre-preg segments 32 when the applicator head 90 moves through, and directs the fiber pre-preg segments 32 over the substrate 34.It should be particularly noted here that system 88, which includes the applicator head 90 discussed above, is merely illustrative of a wide variety of equipment that can be used to place and position the pre-preg segments 32. The particular form of system 88 that is used will depend on the application, which includes specific structural requirements, and the deposition techniques that are employed. Furthermore, the manufacture of the pre-preg segments 32 and the equipment used to place and position the segments 32 on a substrate 34 can be implemented using a single machine or multiple machines. Petition 870200029237, dated 04 / 03 / 2020, page 30 / 106 / 28 different.

[0088] Figure 13 illustrates an alternative embodiment of the applicator head 90 shown in Figure 12, in which several rows of individual chopped fiber prepreg segments 32 can be simultaneously dispensed aligned in a desired orientation, and placed by the applicator head 90 to form a bandwidth 110 of segments 32 with each pass through the applicator head 90 via the substrate 34.

[0089] Referring now to figures 14-17, the described embodiments can be employed to deposit layers or plies of discontinuous fiber prepreg using prepreg scrap 124 (figure 15). Referring to figure 14, as shown in step 112, prepreg scrap 124 can be obtained from unshaped parts / prepreg scrap resulting from other production processes. Prepreg scrap 124 can have any of several shapes as shown in figure 15. In step 116 shown in figure 14, prepreg scrap 124 is chopped into individual fiber prepreg segments 32, and following this chopping process, the segments 32 can have a random fiber orientation 126 as shown in figure 16, and / or can have fibers of different lengths. In step 118 the indicated fiber pre-preg segments 32 are substantially aligned 128 with a desired fiber orientation, as shown in figure 17.In step 120, the aligned fiber prepreg segments 32 are fed into an applicator. In step 122, the applicator is used to dispense, direct, and place the fiber prepreg segments 32 onto the substrate 34, so that the fiber orientations of the fiber prepreg segments 32 are aligned in a desired direction.

[0090] The pre-preg of chopped fiber 32 derived from scrap, which is used in the described method, can be produced using any of several processes. For example, referring to figure 18, pre-preg scrap 124 can be introduced into a chopping device 130 which can Petition 870200029237, dated 04 / 03 / 2020, page 31 / 106 / 28 being similar to a mixer that has rotating blades 132 inside an open vessel 135. The blades 132 chop and break the fiber prepreg scrap 124 into individual fiber prepreg segments 32, breaking or splitting the prepreg along the lines of, and between the reinforcing fibers results in fiber prepreg segments that have a random orientation 126. With the prepreg scrap having been chopped into individual fiber prepreg segments 32, the randomly oriented fiber prepreg segments 32 are aligned, for example, by placing them in a mixing tray 134 that has a series of parallel channels 136.The agitator tray 134 is vibrated from side to side 138 causing the randomly oriented fiber prepreg segments 126 32 that were loaded onto the tray 134 to fall into and align within the channels 136, resulting in aligned rows 140 of fiber prepreg segments 32. The aligned rows 140 of fiber prepreg segments 32 can be fed to an applicator head 90 which dispenses, places and directs the fiber prepreg segments 32 onto the substrate 34 with desired fiber orientations.

[0091] Figures 19A-21B illustrate another embodiment of a method of directing chopped fiber prepreg segments 32 onto a substrate 34. As shown in Figures 19A-19B, an applicator 140 is used to apply 142 a suitable resin 144 onto the substrate 34 as the applicator 140 moves 150 across the substrate 34. The resin 144 can be applied by spraying the resin 144 onto the substrate 34, laminating the resin 144 onto the substrate 34, or using other application techniques. Then, as shown in Figures 20A-20B, chopped fiber prepreg segments 32 are applied to the substrate 34 by a suitable applicator 146 that moves 150 across the substrate 34. When initially applied in this manner, the fiber prepreg segments 32 can have random orientations as shown in Figure 20B. So, as shown in figures 21A and 21B, an aligner of Petition 870200029237, dated 04 / 03 / 2020, page 32 / 106 / 28 Fiber segment 148 is moved 150 over substrate 34 to align fiber pre-preg segments 32 in a desired direction, which in this case is along the geometric axis 36. The fiber segment aligner 148 may use one or more mechanical devices to contact and realign fiber pre-preg segments 32 or, alternatively, may use non-contact techniques such as an air current (not shown) to achieve the desired segment alignment. As discussed earlier, however, orienting the segments 32 when they are initially placed over substrate 34 may be desirable in some applications, as this technique may eliminate the need for the additional step of repositioning the segments 32 to the desired fiber orientations.

[0092] Figures 22A-24B illustrate an alternative technique for placing and aligning fiber prepreg segments 32 on the substrate 34. Referring to Figures 22A and 22B, a small amount such as a drop of resin 152 is placed on one end 154 of each of the fiber prepreg segments 32. Then, as shown in Figures 23A and 23B, the fiber segment 32 is placed on the substrate 34. At this point the fibers in the fiber segment 32 may not be aligned with the desired orientation, such as the geometric axis 36. As shown in Figures 24A and 24B, the fiber segment 32 is then rotated 156 so that the fiber orientation of the fiber segment 32 is aligned with the geometric axis 36. The orientation process can be performed using mechanical devices 49 or using non-contact techniques such as passing an air current over the substrate 34.

[0093] Modalities of the description may find use in a variety of potential applications, particularly in the transport industry, which include, for example, aerospace, marine, automotive, and other applications where composite structures may require local elements that demand tight contours, thickness and / or section control. Petition 870200029237, dated 04 / 03 / 2020, page 33 / 106 / 28 custom-made transversal. Thus, referring now to figures 25 and 26, embodiments of the description can be used in the context of a manufacturing and service method for aircraft 158 ​​as shown in figure 25 and an aircraft 160 as shown in figure 26. Applications of the embodiments described for the aircraft may include, for example, without limitation, various parts of the aircraft structure 176 such as structures, beams and masts and stringers to name just a few. During pre-production the method taken as example 158 may include specification and design 162 of the aircraft 160 and material procurement 164. During production and manufacturing of components and sub-assemblies 166 and systems integration 168 of the aircraft 160 take place. From then on, aircraft 160 goes through certification and delivery 170 to be put into service 172.While in service for a customer, aircraft 160 is scheduled for routine maintenance and servicing 174, which may also include modification, reconfiguration, refurbishment, repair and so on.

[0094] Each of the processes in method 158 can be performed or carried out by a system integrator, a third-party partner, and / or an operator, for example, a customer. For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and main system subcontractors; a third-party partner may include without limitation any number of subcontractors and suppliers, and an operator may be an airline, leasing company, military entity, service organization, and so forth.

[0095] As shown in Figure 26, the aircraft 160 produced by the method taken as example 158 may include an airframe 176 with a plurality of systems 178 and an interior 180. Examples of high-level systems 178 include one or more propulsion systems 182, an electrical system 184, a hydraulic system 188 and a system Petition 870200029237, dated 04 / 03 / 2020, page 34 / 106 / 28 environmental 190. Any number of other systems may be included. Although an aerospace example is shown, the principles of the description can be applied to other industries, such as the marine and automotive industries.

[0096] Systems and methods incorporated herein may be employed during any one or more of the stages of the production and service method 158. For example, components or subassemblies corresponding to the production process 166 may be manufactured or produced in a manner similar to components and subassemblies produced while the aircraft 160 is in service. Also, one or more apparatus modalities, method modalities, or a combination thereof, may be used during the production stages 166 and 168, for example, substantially speeding up assembly of or reducing the cost of an aircraft 160. Similarly, one or more apparatus modalities, method modalities, or a combination thereof, may be used while the aircraft 160 is in service, for example and without limitation, to perform maintenance and service 174, or to perform repair or refurbishment of structures at any time during the service life of the aircraft 160.

[0097] As used here, the phrase “at least one of” when used with a list of items means that different combinations of one or more of the listed items can be used, and only one of each item on the list can be required. For example, “at least one of item A, item B, and item C” can include, without limitation, item A, item B, item C, or item B. This example can also include item A, item B, and item C, or item B and item C. The item can be a particular object, thing, or category. In other words, at least one of means any combination of items and number of items can be used from the list, but not all items on the list are required.

[0098] The description of the different illustrative modalities was Petition 870200029237, dated 04 / 03 / 2020, page 35 / 106 / 28, presented for illustrative and descriptive purposes, is not intended to be exhaustive or limited to the modalities in the form described. Various modifications and variations will be evident to those of ordinary skill in the technique. Furthermore, different illustrative modalities may provide different advantages when compared to other illustrative modalities. The selected modality or modalities are chosen and described to better explain the principles of the modalities, their practical application, and to enable others of ordinary skill in the technique to understand the description for various modalities with various modifications, as they are suitable for the particular use considered.

Claims

CLAIMS 1. Method for forming a composite element (30) having discontinuous reinforcing fibers, comprising: producing a plurality of resin-infused fiber segments (32), each having unidirectional reinforcing fibers (25), wherein the unidirectional reinforcing fibers (25) extend parallel to each other, and wherein the production of the plurality of resin-infused fiber segments (32) comprises pre-preg chipping fiber into the plurality of resin-infused fiber segments (32), each having unidirectional reinforcing fibers (25);placing the plurality of resin-infused fiber segments (32) onto a substrate (34), wherein placing the plurality of resin-infused fiber segments (32) onto the substrate (34) comprises introducing the plurality of resin-infused fiber segments (32) into an air stream, and characterized by using the air stream to propel the plurality of resin-infused fiber segments (32) through a nozzle (108) in an applicator head (90) onto the substrate (34); and arranging the resin-infused fiber segments (32) so that the reinforcing fibers (25) of the plurality of resin-infused fiber segments (32) placed on the substrate (34) are aligned with respect to a desired reference orientation by rotating the plurality of resin-infused fiber segments (32) after the plurality of resin-infused fiber segments (32) have been placed on the substrate (34).

2. Method according to claim 1, characterized in that the production of the plurality of resin-infused fiber segments (32) comprises splitting pre-preg fiber along and between the reinforcing fibers (25) into individual pieces.

3. Method according to claim 1 or 2, characterized by Petition 870260044256, dated 11 / 05 / 2026, page 11 / 23 2 / 6 fact that placing the resin-infused fiber segments (32) on the substrate (34) comprises: moving the applicator head (90) over the substrate (34); and dispensing the plurality of resin-infused fiber segments (32) from an applicator head (90) onto the substrate (34) as the applicator head (90) moves over the substrate (34).

4. Method according to claim 3, characterized in that arranging the plurality of resin-infused fiber segments (32) comprises aligning the plurality of resin-infused fiber segments (32) as they are dispensed from the applicator head (90) onto the substrate (34).

5. Method according to claim 3 or 4, characterized in that the production of the plurality of resin-infused fiber segments (32) comprises: stretching a continuous fiber pre-preg tape from a pre-preg tape supply (98) onto the applicator head (90); and chopping the pre-preg tape into the plurality of resin-infused fiber segments (32) as the resin-infused fiber segments (32) are being dispensed from the applicator head (90) onto the substrate (34).

6. Method according to any one of claims 3 to 5, characterized in that dispensing the plurality of resin-infused fiber segments (32) from the applicator head (90) comprises dispensing a bandwidth of the plurality of resin-infused fiber segments (32) onto the substrate (34).

7. Method according to any one of claims 1 to 6, characterized in that it further comprises: applying resin to the substrate (34) before the plurality of resin-infused fiber segments (32) are placed on the substrate Petition 870260044256, dated 11 / 05 / 2026, page 12 / 23 3 / 6 (34).

8. Method according to any one of claims 1 to 7, characterized in that it further comprises applying a resin over at least one end of each of the plurality of resin-infused fiber segments (32) before they are placed on the substrate (34).

9. Method according to any one of claims 1 to 3, characterized in that arranging the plurality of resin-infused fiber segments (32) comprises placing the resin-infused fiber segments (32) in a shaking tray (134) having a series of parallel channels (136) and vibrating the shaking tray (134) from side to side.

10. Method according to claim 1, characterized in that it further comprises: placing a pre-preg tape in an applicator head (90); then chopping the pre-preg tape into a plurality of different resin-infused fiber segments (32), each having unidirectional reinforcing fibers (25) and each chopped to have a desired aspect ratio, wherein an aspect ratio comprises a length of an individual segment divided by a width of the individual segment; moving the applicator head (90) over the substrate (34); dispensing the plurality of different resin-infused fiber segments (32) from the applicator head (90) onto the substrate (34) as the applicator head (90) moves over the substrate (34);and direct, using the applicator head (90), the plurality of different resin-infused fiber segments (32) so that the unidirectional reinforcing fibers (25) of all the plurality of different resin-infused fiber segments (32) placed on the substrate (34) are aligned with respect to a desired reference orientation.; 11. Method according to claim 10, characterized Petition 870260044256, dated 11 / 05 / 2026, page 13 / 23 4 / 6 by the fact that chopping the plurality of different resin-infused fiber segments (32) comprises splitting the pre-preg tape along and between the reinforcing fibers (25) into individual pieces.

12. Method according to claim 10 or 11, characterized in that directing the plurality of different resin-infused fiber segments (32) comprises aligning the plurality of chopped resin-infused fiber segments (32) as they are dispensed from the applicator head onto the substrate (34).

13. Method according to any one of claims 10 to 12, characterized in that chopping the plurality of different resin-infused fiber segments (32) comprises: stretching the pre-preg tape from a pre-preg tape supply onto the applicator head; and chopping the pre-preg tape into a plurality of different resin-infused fiber segments (32) as the plurality of different resin-infused fiber segments (32) are being dispensed from the applicator head (90) onto the substrate (34).

14. Method according to any one of claims 10 to 13, characterized in that directing the plurality of resin-infused fiber segments (32) different from the applicator head (90) comprises dispensing a bandwidth of resin-infused fiber segments (32) onto the substrate (34).

15. Method according to any one of claims 10 to 14, characterized in that directing the plurality of different resin-infused fiber segments (32) comprises: introducing the plurality of different resin-infused fiber segments (32) into an air stream; and using the air stream to project the plurality of different resin-infused fiber segments (32) from the applicator head Petition 870260044256, dated 11 / 05 / 2026, page 14 / 23 5 / 6 onto the substrate (34).

16. Method according to claim 15, characterized in that projecting the plurality of different resin-infused fiber segments (32) comprises: using the air current to project the plurality of different resin-infused fiber segments (32) onto the substrate (34).

17. Method according to any one of claims 10 to 16, characterized in that it further comprises: applying resin to the substrate (34) before the plurality of different resin-infused fiber segments (32) are placed on the substrate (34).

18. Method according to any one of claims 10 to 17, characterized in that it further comprises applying a resin over at least one end of each of the plurality of different resin-infused fiber segments (32) before they are placed on the substrate (34).

19. Apparatus for depositing a composite structure for carrying out the method as defined in claim 1, characterized in that it comprises: an applicator head (90) adapted to move over a substrate (34) and dispense at least one stream of aligned resin-infused fiber segments (32) applied over the substrate (34), wherein the applicator head (90) includes: a supply (98) of continuous resin-infused fiber; a chopper (103) for chopping the continuous resin-infused fiber into individual resin-infused fiber segments (32), each of the resin-infused fiber segments (32) having Petition 870260044256, dated 11 / 05 / 2026, page.15 / 23 6 / 6 unidirectional reinforcing fibers (25); wherein the fibers extend parallel to each other; and an air current generator (106) to propel the resin-infused fiber segments (32) through a nozzle (108) in the applicator head (90) onto the substrate (34) so ​​that the reinforcing fibers (25) of the resin-infused fiber segments (32) placed on the substrate (34) are aligned with respect to a desired reference orientation by rotating the plurality of resin-infused fiber segments (32) after the plurality of resin-infused fiber segments (32) have been placed on the substrate (34).

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