Structural bonded patch with tapered adhesive design

Mutual reference to related applications This application is a division of US application number 12 / 400,519 filed March 9, 2009, US patent number 8,449,703 issued May 28, 2013, and agent reference number 08-1011-US-NP. US Application No. 13 / 902,816, filed May 26, 2013, entitled "Predictable Bonded Rework of Composite Structures Using Tailored Patches," an application and disclosure incorporated by reference herein. No. 08-1011-US-DIV, US Patent Publication No. No. 2013/0337214 is a partial continuation application.

The present disclosure relates to composite structures in general, and in particular to reworking composite structures. More specifically, the present disclosure relates to methods and devices for reworking inconsistent areas of composite structures using patches of tapered adhesive design.

Composite structures may have localities containing one or more inconsistencies that may require rework to keep the structure within design tolerances. These inconsistencies can include, for example, but not limited to, cracks, delamination, and other types of inconsistencies formed during the life cycle of the composite structure.

Often, inconsistent areas of the composite structure are reworked using patches. The patch may include composites, metals, or combinations thereof. Various types of techniques can be used to rework composite structures using patches.

For example, patches may be placed to cover inconsistent areas and attached to the parent structure using mechanical fasteners. The condition of the patch may be monitored over time by visually inspecting the fasteners.

In other cases, rework patches may be attached to the parent structure using joints. This technique may also require the use of mechanical fasteners to provide ancillary load paths that form an arrestment mechanism to limit the growth of inconsistencies.

However, these types of patching techniques may not be performed as desired if the composite structure is an aircraft structure. For example, the use of fasteners may increase the weight of the aircraft, drag on the aircraft, or both more than desired. As another example, the joined patch may not reduce the spread of inconsistencies as desired. Therefore, it would be desirable to have a method and device that takes into account at least some of the problems mentioned above and other possible problems.

The embodiments of the present disclosure provide methods and devices for reworking inconsistent areas of structure. The structure can take the form of a composite structure used in an aircraft. In some cases, the structure may also be a metal structure.

The patch is joined to the inconsistent area of the structure. The patch has two or more regions with different structural properties. A tapered adhesive section is positioned between the patch and the structure. These tapered adhesive sections also have different structural properties. For example, the tapered adhesive section can have different kinematic constants, elastic constants, structural constants, interlayer fracture toughness, or a combination thereof.

Both the patch area and the tapered adhesive section can be adjusted to reduce the strain energy release rate in the inconsistent boundary area more effectively than a patch using fasteners or joints without the tapered adhesive section. .. Crack expansion can be reduced or eliminated. As such, patches with tapered adhesive sections substantially increase the damage resistance and durability of the structure throughout the life cycle of the aircraft. As a result, the tapered adhesive section extends patch life and reduces the number of rework on mismatched areas.

The properties and functions can be realized alone in the various embodiments of the present disclosure, or combined in yet another embodiment in which further details can be understood with reference to the following description and drawings. You may.

New features that are considered to be characteristics of the exemplary embodiment are specified in the appended claims. However, embodiments and preferred modes of use, as well as their objectives and features, will be best understood by reading the following detailed description of embodiments of the present invention with reference to the accompanying drawings.

<figref num="1">FIG. 5 is a diagram of a joined rework patch on a composite structure according to an exemplary embodiment.</figref><figref num="2">FIG. 6 is a cross-sectional view of a joined rework patch on a composite structure according to an exemplary embodiment.</figref><figref num="3">It is a top view of the adhesive layer by an exemplary embodiment.</figref><figref num="4">It is sectional drawing of the adhesive layer by an exemplary embodiment.</figref><figref num="5">It is a top view of the composite rework patch formation part of the rework patch by an exemplary embodiment.</figref><figref num="6">It is sectional drawing of the composite rework patch formation part of the rework patch by an exemplary embodiment.</figref><figref num="7">FIG. 5 is a cross-sectional view of an adjusted laminate patch divided into regions with different interlayer toughness according to an exemplary embodiment.</figref><figref num="8">It is a table which shows the ply schedule for the different region of the laminated laminated board patch adjusted by an exemplary embodiment.</figref><figref num="9">It is a top view which shows the ply in the laminated board patch by an exemplary embodiment.</figref><figref num="10">It is a top view which shows the ply in the laminated board patch by an exemplary embodiment.</figref><figref num="11">It is a top view which shows the ply in the laminated board patch by an exemplary embodiment.</figref><figref num="12">It is a top view which shows the ply in the laminated board patch by an exemplary embodiment.</figref><figref num="13">FIG. 5 is a plan view of a rework patch showing a typical propagation path of disjoint according to an exemplary embodiment.</figref><figref num="14">FIG. 5 is a cross-sectional view showing the gradual disassociation over the area of a patch according to an exemplary embodiment.</figref><figref num="15">FIG. 5 is a cross-sectional view showing the gradual disassociation over the area of a patch according to an exemplary embodiment.</figref><figref num="16">FIG. 5 is a cross-sectional view showing the gradual disassociation over the area of a patch according to an exemplary embodiment.</figref><figref num="17">FIG. 6 is a flow chart of a process for reworking an area of a composite structure containing inconsistencies using patches, according to an exemplary embodiment.</figref><figref num="18">FIG. 5 is a diagram of an aircraft according to an exemplary embodiment.</figref><figref num="19">It is a block diagram of the reworking environment by an exemplary embodiment.</figref><figref num="20">FIG. 5 is a diagram of a joined component rework patch according to an exemplary embodiment.</figref><figref num="21">FIG. 3 is a partial cross-sectional view of a tapered adhesive section according to an exemplary embodiment.</figref><figref num="22">It is a graph of the interplanar interlayer tensile stress inside the joint patch according to the exemplary embodiment.</figref><figref num="23">It is a graph of the interlayer shear stress inside the joint patch by an exemplary embodiment.</figref><figref num="24">FIG. 5 is an overall cross-sectional view of a joined composite rework patch on a composite structure according to an exemplary embodiment.</figref><figref num="25">It is a figure of the composite rework patch joined by an exemplary embodiment.</figref><figref num="26">FIG. 6 is a flow chart of a process for reworking a composite structure using a patch system with tapered adhesive sections, according to an exemplary embodiment.</figref><figref num="27">It is a block diagram of the manufacturing and maintenance method of an aircraft by an exemplary embodiment.</figref><figref num="28">It is a block diagram of an aircraft in which an exemplary embodiment can be implemented.</figref>

The exemplary embodiment recognizes and considers one or more different considerations. For example, exemplary embodiments recognize and consider that it is desirable to reduce or eliminate the spread of inconsistencies in aircraft structures. As an example, the exemplary embodiment recognizes and considers that it is desirable to provide a patch for inconsistent areas on a composite aircraft structure where disjoint does not occur during aircraft operation. In this exemplary embodiment, "disjoint" may refer to the separation of the patch at the junction between the patch and the overlying composite structure.

The exemplary embodiment further recognizes and considers that it is desirable to reduce stress in the patch, composite structure, or both in order to substantially prevent the spread of inconsistencies within the composite structure. For example, the exemplary embodiments recognize that it is desirable to design patches and lower adhesive layers that release strain energy in a desired manner that substantially prevents expansion through the composite structure of the crack, without limitation. And consider.

Accordingly, exemplary embodiments provide methods and devices for reworking structures. The structure can be a composite structure of an aircraft. The device includes a composite rework patch and a plurality of adhesive layers. The composite rework patch includes a first aspect having an outer shape that matches the inconsistent area on the composite structure. The composite rework patch contains multiple regions with different structural properties. Multiple adhesive layers are located on the first side of the patch. The multiple adhesive layers vary in thickness within at least one region of the composite rework patch to form a tapered adhesive section.

See drawings here, in particular FIGS. 1 and 2. According to the disclosed embodiments, the composite rework patch 30 is used to rework the inconsistent area 22 of the composite structure 24. As used herein, "inconsistent area" and "inconsistency (singular and plural)" each refer to the local area of the composite structure 24, which may be outside the designed margin of error. The mismatched area 22 may include, for example, but not limited to, gaps, depressions, and porosity that may occur when the composite structure 24 is manufactured or during the useful life of the composite structure 24.

The composite rework patch 30 is joined to the composite structure 24 by an adhesive layer 34 that includes a laminate layer 32 that covers the inconsistent area 22 and contains a structural adhesive that forms the junction 42. The size of the composite rework patch 30 may vary depending on the application and dimensions of the inconsistent area 22.

The adhesive layer 34 can significantly reduce the transition load transmitted between the composite structure 24 and the composite rework patch 30 at the joint 42 and the mismatched area 22, respectively, in the first, second, and third Divide into control areas 36, 38, 40. The first control area 36 is centrally located so as to cover the inconsistent area 22, and the second and third control areas 38 and 40 surround the centrally located first control area 36. Each can include concentric rings.

Control areas 36, 38, 40 are shown as general circular in exemplary embodiments, but various other shapes may be formed. Also, in other embodiments, the composite rework patch 30 may have only two control regions, or may have more than three control regions, as shown in FIG. ..

The first control region 36 may exhibit a favorable in-plane adhesive stress. The second control area 38 is sometimes referred to as the "durability area" and any dejunction within this area between the laminate layer 32 and the composite structure 24 determines whether rework should be performed. Therefore, it may be necessary to evaluate and quantify. A third control region 40, which can be dominated by in-plane shear and delamination moments, can affect the overall action of the structural junction between the laminate layer 32 and the composite structure 24.

Here, with particular reference to FIGS. 2-4, the adhesive layer 34 may include a central first adhesive section 44 surrounded by second and third adhesive sections 46 and 48 in the shape of a concentric ring. The sizes and shapes of the first, second, and third bonding sections 44, 46, and 48 generally correspond to the first, second, and third control areas 36, 38, and 40 of the composite rework patch 30, respectively. To do. Each of the first, second, and third adhesive sections 44, 46, 48 is one or more of commercially available structural adhesives generally available in film or sheet shapes that can be cut into the desired shape. May include ply.

The first, second, and third adhesive sections 44, 46, 48 may also be formed from commercially available structural adhesive pastes. As specified earlier, multiple plies (not shown) or layers of adhesive sheet material have the desired thickness for each of the first, second, and third adhesive sections 44, 46, 48. Can be augmented to form a "t". Bond strength can be adjusted using the thickness "t" between the laminate layer 32 and the composite structure 24. Some applications may require only a single ply of the adhesive sheet material, while other applications require multiple plies, depending on the application and thickness of the adhesive sheet. There are times.

In one embodiment, the circumferential gap "g" is the first, second, and third bonding sections to help prevent the growth of potential unbonding between the laminate layer 32 and the composite structure 24. It can be formed between 44, 46 and 48. The filler 50 may be placed in one or both of the gaps "g" to assist in blocking.

The characteristics of the first, second, and third bonding sections 44, 46, and 48 are the rates at which the first, second, and third control regions 36, 38, and 40 of the joint 42 release strain energy, respectively. Can be adjusted to affect. Adjustments of the first, second, and third adhesive sections 44, 46, 48 respectively include first, second, and third adhesive sections 44, 46, such as thickness "t" or width "w". , 48 By changing the dimensions of each, or by changing the morphology of films, pastes, scrims, etc., and by changing the structural properties of the adhesive layer, such as fracture toughness, peeling or shearing properties, or This can be achieved by providing a gap "g" between the first, second and third bonding sections 44, 46, 48. In addition, the spacer or filler 50 may be inserted between the first, second and third bonding sections 44, 46, 48 to assist in growth inhibition of disjoint.

By using the adjusted first, second, and third bonding sections 44, 46, 48, the result is multiple control regions 36, 38, 40, each emitting strain energy at different rates. A joined composite rework patch 30 that is split can result. The first, second, and third control regions 36, 38, and 40 not only significantly reduce the transition load between patch 30 and composite structure 24, but also make the course of dejunction extension predictable. Allows condition assessment of composite rework patch 30 via simple visual inspection or other non-destructive inspection techniques. Three control regions are illustrated and discussed, but there may be more or less control regions.

The first control region 36 of the composite rework patch 30 covering the inconsistent area 22 shows a favorable in-plane stress that can suppress stress concentration around the unjoined boundary of the joint 42. The total adhesive stress inside the first control region 36 can reduce the strain energy release rate required to extend the dejunction under the maximum load limit applied to the composite structure 24.

The properties of the composite rework patch 30 inside the second control region 38 can result in strain energy emissions at a higher rate than the first control region 36. Any disjunction that can occur at the junction 42 inside the second control region 38 is predicted by a fatigue-durable junction disengagement curve (not shown) that defines the work input required to initiate the disassociation growth. sell. The characteristic of the third control region 40 is that the strain energy release rate inside the third control region 40 prevents not only the in-plane shear moment and the peeling moment, but also the initiation and growth of the unbonding. Is selected to be greater than the rate of control area 38 of.

Focusing here on FIGS. 5 and 6, in FIGS. 5 and 6, the first, second, and third control regions 36, 38, in which the ply 52 has a designed strain energy release rate. , 40 Illustrates a laminate layer 32 containing multiple plies 52 of fiber reinforced polymer that can be adjusted to assist in the realization of each.

The strain energy release rate inside the laminate layer 32 selects the plies so that the plies in each of the first, second, and third control regions 36, 38, and 40 have different characteristics, and the plies are arranged. , Or both, can be tuned within control areas 36, 38, 40. In short, each of the first, second, and third control regions 36, 38, and 40 may have ply characteristics that are unique to those regions.

For example, but not limited to, the ply in the second control region 38 has characteristics different from those of the first or third control region 36 or 40, and the ply in the first control region 36 is It may have characteristics different from those of the second and third control regions 38 and 40. As used herein, "property" and "ply property" are, for example, but not limited to, the type, size or quality of fiber reinforcement in the ply, the thickness of the ply, the gap between the plies, the ply. The material, element or structure placed between them, the number of plies, the type or density of the matrix used in the plies, the layup orientation (angle) of each ply, the order of the ply orientations in the ply stack. , Or at least one of the other properties.

As used herein, the expression "at least one of" used with the listed items can be used in various combinations of one or more of the listed items. And it means that you only need one of the listed items. An item is a particular object, article, or category. That is, "at least one of" means any combination of items, some items may be used from the enumeration, but not all of the enumerated items are required.

For example, "at least one of item A, item B, and item C" is, for example, "item A", "item A and item B", "item B", "item A and item B and item C". , Or "item B and item C". In some cases, "at least one of item A, item B, and item C" is, for example, but not limited to, "two items A, one item B, and ten." Item C "," 4 item B and 7 item C ", or any other suitable combination.

Strain energy release rates within one or more of the first, second, and third control areas 36, 38, 40 are scarf or tapered joints (not shown) between the laminate layer 32 and the composite structure 24. ) Can be adjusted. The strain energy release rate also has a gap in some area between the plies 52 so that the mechanical properties of the laminated layers 32 in each of the first, second, and third control regions 36, 38, 40 can be changed. It may be adjusted by providing (not shown).

Also, different operating sequences of the plies 52 may be desired to assist in the realization of the defined first, second and third control regions 36, 38, 40. Orientation refers to the layup angle or direction of the reinforcing fibers in the ply from the central axis of the ply. For example, but not limited to, the angle of the reinforcing fibers in each region is selected from 0 degrees, 30 degrees, 60 degrees, 90 degrees, 0 degrees, +45 degrees, -45 degrees, 90 degrees, and other suitable angles. sell.

In the examples shown in FIGS. 5 and 6, the highest rate of strain relief is achieved by the material used in the ply 52 inside the first control region 36, the orientation order of the plies 52, or both. Brought to you. The selection of these materials, the order of the ply orientations, or both in the second control region 38 and the third control region 40 results in intermediate and minimum rate strain energies, respectively. In other embodiments, depending on the application, the third control region 40 may have the highest rate of strain energy reduction, while the first control region 36 may have the lowest rate of strain energy reduction. In short, the region-by-region ply 52 may be configured in a manner different from that shown herein.

Focusing on FIG. 7, FIG. 7 shows a typical tuned laminate patch 32a containing eight plies 52 of fiber reinforced polymer before being compressed and cured to a compacted laminate. ing. When viewed in plan, the shape of the tuned laminate patch 32a, which includes the first, second, and third control areas 36, 38, 40, is substantially the same as the shape of the composite rework patch 32 shown in FIG. Can be the same as. The ply 52 forming the adjusted laminate patch 32a is sometimes referred to as ply # 1- # 8. FIG. 8 is a table showing the orientation of the plies with respect to the laminated patch 32a inside the first, second, and third control regions 36, 38, and 40 for each ply # 1- # 8, while FIGS. 9 to 9. 12 shows the configuration section of ply 1-4.

As mentioned earlier in connection with FIGS. 5 and 6, the characteristics of the ply 52 can vary from first, second, and third control regions 36, 38, 40. The strain energy release rates in the first, second, and third regions 36, 38, 40 are adjusted laminates in the first, second, and third control regions 36, 38, 40, respectively. It is related to the coefficient or rigidity that defines the interlayer toughness of patch 32a.

In the exemplary example, the first control region 36 has the highest delamination toughness, while the third control region 40 has the lowest delamination toughness. In the illustrated example, the interlayer fracture toughness of the third control region 40 is approximately 0.5 in-# / in.²From 1.0 in-# / in²Can be up to. The interlayer fracture toughness of the second control region 38 is approximately 1.5 in-# / in.²From 2.0 in-# / in²Can be up to. The first control area 36 is approximately 2.5 in-# / in²It can have the above interlayer fracture toughness.

However, in another exemplary example, the third control region 40 may have the highest delamination toughness and the first control region 36 may have the lowest delamination toughness. In this case, the interlayer fracture toughness of the second control region 38 can be between the interlayer fracture toughness of the first control region 36 and the interlayer fracture toughness of the third control region 40.

Specific values for interlayer fracture toughness in the first, second, and third control regions 36, 38, 40 are plies 52 present within the first, second, and third control regions 36, 38, 40. Will depend on the application and specific mechanical properties. However, the values of interlayer fracture toughness inside the first, second and third control regions 36, 38 and 40 are the characteristics of the adhesive layer 34 as shown in FIGS. 3, 3A, 3B and 3C. Can be adjusted to. For example, the patch has the mechanical properties of sections 44, 46, 48 of the adhesive layer 34 and the mechanical properties of the adjusted laminated patch 32a inside the first, second, and third control areas 36, 38, 40. And can be configured to best match to provide maximum performance. Although not shown in FIG. 7, the first, second, and third adhesive sections 44, 46, and 48 of the adhesive layer 34 are the first, second, and third control regions of the laminate patch 32a, respectively. It is the basis for 36, 38 and 40 and can have substantially the same extent as them.

As discussed earlier, the interlaminar fracture toughness inside the first, second, and third control regions 36, 38, 40 is achieved by using different prepreg materials at the ply 52, the first, second, and By stacking plies 52 between adjacent third control regions 36, 38, 40, the order of different ply orientations within each of the first, second, and third control regions 36, 38, 40. Can be controlled by using or a combination thereof. For example, FIG. 8 illustrates the order of the different ply orientations of the plies # 1- # 8 inside each of the first, second, and third control regions 36, 38, and 40.

For example, comparing the order of the orientation of the ply 52 of each of the second control region 38 and the third control region 40, the orientation of the ply # 4 and ply # 5 is 90 degrees in the third control region 40. However, it can be understood that it is 0 degrees in the second control area 38. As mentioned earlier, the ply orientation points to the direction of the unidirectional reinforcing fiber orientation held in the polymer matrix, usually the prepreg, that forms each of the plies 52. The order of the orientations of the plies # 1 to # 8 with respect to the first control region 36 is different from the order of the orientations of the second control region 38 and the third control region 40.

Here, referring to FIGS. 7 and 9 to 12, ply # 1 extends 0 degrees with respect to the orientation reference direction 69, extending over the entire first, second, and third control regions 36, 38, and 40. Includes a single circular section 51 shown in FIG. 9, having a fiber orientation of. Ply # 2 includes a circular center section 53 shown in FIG. 10, with a fiber orientation of +45 degrees. Ply # 2 also has an outer ring-shaped section 55 with a 90 degree fiber orientation. As a result of the configuration of ply # 2, the control region 36 has a fiber orientation that combines 90 degrees and +45 degrees, whereas the control regions 38 and 40 both have a fiber orientation of 90 degrees. doing.

Ply # 3 contains a single section 57 (FIG. 11) inside a first control region 36 with a fiber orientation of -45 degrees, whereas a second control region 38 and a third control region 40 There is a gap 49 (Fig. 7) in. Finally, ply # 4 (FIG. 12) includes a section 59 with 0 degree fiber orientation extending through the first control region 36 and the second control region 38. Section 59 is surrounded by section 61 with a 90 degree fiber orientation confined to the third control region 40. Ply # 5- # 8 shown in FIG. 7 is essentially a mirror image of the above-mentioned ply # 1- # 4.

In this exemplary embodiment, the first, second, and third control regions 36, 38, and 40 each have different interlayer fractures in the conditioned laminate patch 32a, joint 42, or both (FIG. 2). Has toughness. The interlaminar fracture toughness inside the first, second, and third control regions 36, 38, and 40 of the tuned laminate patch 32a is the growth of inconsistencies in either the tuned laminate patch 32a or the joint 42. Can be configured to respond to the overall adhesive stress at the joint 42 to include and resist it.

FIG. 13 illustrates how disjunction starting at point 60 and growing inward at the outer edge of the third control region 40 can be prevented. The disconnection starting at the outer edge 54 grows inward as shown in the direction of arrow 62 until boundary 64 reaches between the second control area 38 and the third control area 40. It can be illustrated in the examples. Material differences in the first, second and third control regions 36, 38, 40, the presence of a gap "g" or filler 50 (FIG. 4), or the first, first of the adhesive layer 34 (FIG. 2). As a result of at least one of the differences in the bonding properties of the second and third bonding sections 44, 46, 48, the unbonding is blocked and the third control area 40 is shown in the direction of arrow 63. Can move around the boundary 64 in the circumferential direction.

In another exemplary embodiment, disjoint proceeds inward from the third control region 40 into the second control region 38 and then towards the first control region 36, as indicated by arrow 66. sell. The progress of disassociation is blocked when it reaches the boundary 67 between the first control area 36 and the second control area 38, and can move circumferentially around the boundary 67, as indicated by arrow 68. ..

With reference to FIGS. 13 and 14, as the dejunction 72 moves inward from point 60, the outer edge 54 of the composite rework patch may peel upward. This peeling can cause cracks in a portion of the overcoating paint (not shown), which visually represents the initiation or growth of debonding within the third control area 40. This visual indication of disjunction can be terminated at the boundary 64 between the second control area 38 and the third control area 40.

As shown in FIG. 15, when the uncoupling 72 continues within the second control region 38 toward the boundary 67, the compound rework of the areas of the second control region 38 and the third control region 40 is performed. Patch 30 may peel upwards. Further cracks may occur in the overlying paint, and it may be visually indicated that the dejunction 72 has progressed within or through the second control area 38.

FIG. 16 shows the dejunction 72 that has progressed to boundary 75 of the inconsistent area 22. At this point, the composite rework patch 30, and all three areas of the first, second, and third control areas 36, 38, and 40, peeled upwards and further cracked the overlying paint. May occur. This move is a clearer visual indication that the compound rework patch 30 has progressed to a point where it may need repair.

In this exemplary embodiment, the first, second, and third control regions 36, 38, and 40 of the composite rework patch 30 include a junction 42 between the composite rework patch 30 and the composite structure 24. Provides a means to enable non-destructive visual inspection of the condition of the composite rework patch 30. In other exemplary embodiments, other non-destructive inspection techniques can be used to assess the condition of the composite rework patch 30 in addition to or in place of visual inspection.

FIG. 17 shows a flow chart of the process for reworking areas of a composite structure containing inconsistencies using patches. The patch used can be the tuned rework patch 32a shown in Figure 7. The laminate layer is formed by a series of steps 74 starting by laying up the plies in step 78, using a ply schedule and orientation sequence that may be similar to those shown in FIGS. 7 and 8.

As shown in step 80, the ply is divided into multiple regions as part of the ply layup from step 78. Also, the regions are provided with the different interlayer fracture toughness shown in step 82 by using the different material and / or ply orientation sequences discussed earlier.

In step 84, a layer of adhesive is formed, and in step 86, the adhesive layer is divided into a plurality of sections. The region is then aligned with the section of the adhesive layer as shown in step 88. The adhesive layer is used to join the patch to the structure, as shown in step 90. In step 92, the patch can be visually inspected over time to determine the state of the patch on a region-by-region basis.

With reference to FIG. 18, a diagram of the aircraft is shown according to an exemplary embodiment. In this exemplary embodiment, aircraft 100 has wings 102 and wings 104 attached to airframe 106. Aircraft 100 includes engine 108 mounted on wing 102 and engine 110 mounted on wing 104.

Aircraft 106 has a tail 112. The horizontal stabilizer 114, the horizontal stabilizer 116, and the vertical stabilizer 118 are attached to the tail 112 of the airframe 106.

In this exemplary embodiment, the wing 104 comprises a composite structure 24. The composite structure 24 takes the form of a composite skin panel in this exemplary embodiment. As shown, the mismatched area 22 resides in the composite structure 24 on the wing 104.

In this illustrated embodiment, the composite rework patch 119 is used to patch the inconsistent area 22. The composite rework patch 119 includes a first control area, a second control area, and a third control area. The composite rework patch 119 also includes a tapered adhesive section (not shown in this figure). These tapered adhesive sections join the composite rework patch 119 to the mismatched area 22 and are inconsistent with the composite rework patch 119 to reduce the force acting on the mismatched area 22 during the operation of the aircraft 100. It is positioned between the area 22 and the area 22.

With reference to FIG. 19, a block diagram of the rework environment is shown according to an exemplary embodiment. In this illustrated embodiment, the rework environment 130 is an environment in which the patch system 132 can be used to rework parts of the aircraft 134.

Aircraft 100 shown in FIG. 18 is an example of a physical embodiment for aircraft 134 shown in this figure. The composite rework patch 30 shown in FIGS. 1 to 16 and the composite rework patch 119 shown in FIG. 18 are examples of embodiments for the patch system 132 of this figure.

As illustrated, the patch system 132 is used to rework the structure 136 inside the aircraft 134. The structure 136 can take various forms in this exemplary embodiment. For example, the structure 136 may take the form of another type of structure, such as a composite structure 138, a metal structure 140, or an aircraft 134. In particular, the structure 136 of the aircraft 134 can be selected from one of control structural surfaces, structural skin panels, wing structures, structural tails, and other suitable types of structures.

In this illustrated embodiment, the structure 136 has a surface 142. Surface 142 faces the exterior of aircraft 134 in this exemplary embodiment.

The inconsistent area 144 is in structure 136. The inconsistent area 22 shown in FIGS. 1 to 16 and 18 is an example of an embodiment for the inconsistent area 144 illustrated in the block format of this figure. In some exemplary embodiments, the inconsistent area 144 can be extended from below the surface 142 into the structure 136 through additional structures connected to the structure 136, or both.

As shown, the inconsistent area 144 includes a crack 146. The crack 146 is a crack in the structure 136. Other inconsistencies may be present in the inconsistent area 144 in addition to or in place of the cracks 146 of other exemplary embodiments.

In this exemplary embodiment, the crack 146 has a crack tip 148 at each end of the crack 146. It may be desirable to substantially prevent the crack 146 from expanding inside the crack boundary of the surface 142 of the structure 136. In particular, it may be desirable to substantially prevent the crack tip 148 at each end of the crack 146 from further expanding along the surface 142 of the structure 136.

In this illustrated example, the patch system 132 can be used to rework the inconsistent area 144 and substantially prevent the expansion of the crack 146. The patch system 132 contains several different components. As used herein, the "several" items can be one or more items. For example, some component means one or more components.

As illustrated, patch system 132 includes patch 149. The patch 149 is a structure that is positioned so as to cover the inconsistent area 144 and is configured to be joined to the inconsistent area 144 by using a plurality of adhesive layers 152. Patch 149 can include a variety of materials, including metals, composites, and other suitable materials.

As illustrated, patch 149 takes the form of a composite rework patch 150 configured to be joined to composite structure 138 using multiple adhesive layers 152. In this exemplary embodiment, the composite rework patch 30 of FIGS. 1 to 16 is an example of an embodiment for the composite rework patch 150 of this figure.

In this illustrated example, the composite rework patch 150 has a composite layer 151. The composite layer 151 may include group 153 of composite plies. The ply 52 in the laminate layer 32 shown in FIG. 7 may be an example of an embodiment for a composite layer 151 having a group of composite plies 153.

As used herein, the "group" of items means one or more items. For example, the composite ply group 153 includes one or more composite plies.

In this exemplary embodiment, the composite rework patch 150 includes a first side surface 154 and a second side surface 155. The second side surface 155 faces the first side surface 154. In this exemplary embodiment, the first side surface 154 of the composite rework patch 150 faces inward with respect to the structure 136 and is connected to the tapered adhesive section 156. The first side surface 154 of the composite rework patch 150 may have an outer shape 157 that matches the inconsistent area on the structure 136.

The second side 155 of the composite rework patch 150 faces outward with respect to the environment surrounding the structure 136. The second side 155 of the composite rework patch 150 may have a variety of contours 159, depending on the particular embodiment. In some cases, when joined to structure 136, the second side surface 155 of the composite rework patch 150 can be substantially parallel to the surface 142 of structure 136.

In another example, the second side surface 155 substantially coincides with the taper 161 in the inconsistent area 144 of the structure 136. In short, the second side surface 155 can match the taper 161 instead of being substantially parallel to the surface 142 once the composite rework patch 150 is joined to the structure 136. Taper 161 may be the result of a scarf repair operation performed on structure 136 prior to application of patch system 132.

As shown, the composite rework patch 150 includes a plurality of regions 158. The first, second, and third control regions 36, 38, and 40 shown in FIG. 1 are examples of embodiments for the plurality of regions 158.

In this exemplary embodiment, the plurality of adhesive layers 152 are located on the first side surface 154 of the composite rework patch 150. In particular, several adhesive layers are located inside each of the plurality of regions 158 of the composite rework patch 150. The plurality of adhesive layers 152 may have various configurations corresponding to each of the plurality of regions 158.

The plurality of adhesive layers 152 may include a film adhesive in this exemplary embodiment. The film adhesive may take the form of a tape or sheet placed in the mismatched area 144 prior to applying the composite rework patch 150.

In this exemplary embodiment, each of the plurality of adhesive layers 152 has a thickness of 160 and a width of 162. The thickness "t" and width "w" shown in FIG. 4 are examples of thickness 160 and width 162.

In this illustrated example, the plurality of adhesive layers 152 may vary in thickness 160 within at least one region of the composite rework patch 150. This change in thickness 160 forms a tapered adhesive section 156 under the composite rework patch 150.

In an exemplary embodiment, the adhesive has a varying thickness-to-width ratio of 165 inside each of the tapered adhesive sections 156. For example, different bonding sections can have a 30: 1 ratio, a 20: 1 ratio, a 10: 1 ratio, or other ratios, depending on the particular embodiment. As a result, the slope of each of the tapered adhesive sections 156 can be different.

In an exemplary embodiment, when the adhesive is placed on the composite structure 138, the thickness of each layer of the adhesive may be the same, but the width may be different. When the plurality of adhesive layers 152 are stacked on top of each other with different widths, the layers form a stack of adhesives with different thicknesses.

For example, when an adhesive is placed, each of the next layers of adhesive can be narrower than the previous layer. For example, the first layer may have a first width and the second layer resting on top of the first layer may have a second width that is less than the first width. In addition, the third layer resting on top of the second layer may have a smaller width, and so on. Thus, the plurality of adhesive layers 152 form a regular stair-stepped or tapered configuration within each of the tapered adhesive sections 156. Therefore, the thickness-to-width ratio 156 of each of the tapered adhesive sections 156 may vary based on the number of layers layered on top of each other, the width of these layers, or both. This concept is shown in FIGS. 21 and 24.

In an exemplary embodiment, the tapered adhesive section 156 formed by the plurality of adhesive layers 152 can generally correspond to the plurality of regions 158 of the composite rework patch 150. In short, one of the tapered adhesive sections 156 can be positioned directly below one of the multiple regions 158 in the composite rework patch 150.

In some cases, more tapered bonding sections 156 may be present in the patch system 132 than in multiple regions 158 in the composite rework patch 150. For example, but not limited to, three regions may be present within the composite rework patch 150, while five tapered adhesive sections 156 may be present below the composite rework patch 150. In a similar aspect, more regions may be present in the composite rework patch 150 than in the plurality of adhesive layers 152. As an example, four regions can be present within the composite rework patch 150, while no more than three tapered adhesive sections 156 can be present below the composite rework patch 150.

As shown, the tapered adhesive section 156 has a first section 166, a second section 168 that surrounds the first section 166, and a third section 170 that surrounds the second section 168. And include. In some exemplary embodiments, there may be some additional sections. For example, a fourth section 172 may surround a third section 170, and so on.

In some cases, the gap 173 may be between one or more of the tapered adhesive sections 156. An example of an embodiment for gap 173 is shown in FIG. 7 as "g". The gap 173 can be a circumferential gap between the tapered adhesive sections 156 that are configured to reduce the growth of the mismatched area 144. In other exemplary embodiments, the gap 173 may not be present or may have a different configuration than that shown in FIG.

In this exemplary embodiment, the patch system 132 emits strain energy 174 into the composite rework patch 150 and at different rates 176 from the composite rework patch 150, each of a plurality of regions 158 within the composite rework patch 150. Designed to do so. In a similar aspect, each of the tapered bonding sections 156 can be adjusted to release strain energy 174 at different rates 176.

In particular, the strain energy 174 can be released from the composite structure 138 into the composite rework patch 150 at different rates 176. The strain energy 174 is then returned from the inconsistent area 22 into the composite structure 138 again to prevent the unconformity area 22 from expanding and to prevent the composite rework patch 150 from breaking the bond between the composite structure 138. Can be done.

In this exemplary embodiment, the strain energy 174 is the energy stored by the system undergoing deformation under load 178. When the load 178 is removed, the strain energy 174 is gradually released as the system returns to its original shape.

The desired release of strain energy 174 prolongs the life of the patch system 132, reduces the risk of further inconsistency formation in the structure 136, or both. In order to prevent the unconformity area 22 from expanding, it may be desirable to release strain energy 174 at a higher rate in the section of the composite rework patch 150 far away from the unconformity area 22.

Each of the plurality of regions 158 may have a different characteristic 180 that allows the strain energy 174 to be released at different rates 176. Each of the tapered adhesive sections 156 can also have different properties 180.

In this exemplary embodiment, the property 180 can be tuned to produce a patch system 132 that is performed in the desired manner during the useful life of the aircraft 134. Property 180 may include at least one of structural property 182, interlayer fracture design 184, structural shape 186, or other suitable type of property.

In an exemplary embodiment, structural property 182 refers to various load handling and load transfer properties of the material. For example, structural property 182 may refer to a material's ability to resist elastic deformation and release strain energy 174, or any other property.

In this illustrated example, structural property 182 includes kinematic constants, elastic constants, structural constants, interlayer fracture toughness, and other suitable properties. In this exemplary example, the kinematic constant represents the relationship between material displacement and strain. Each of the tapered adhesive sections 156 has a different stress-strain relationship in this exemplary embodiment, resulting in different kinematic constants between the sections.

The elastic constant represents the degree to which the material has elasticity. In short, the elastic constant represents the extent to which the material will be expanded or consolidated when a load 178 is applied. Examples of elastic constants can include Poisson's ratio, elastic modulus, shear stiffness, and other constants. Each of the tapered bonding sections 156 can also have different elastic constants from each other.

Moreover, each of the tapered bonding sections 156 can also have different structural constants. Structural constants represent the bending properties of the material.

In an exemplary embodiment, the tapered bonding section 156 is also designed to have different interlayer fracture toughness. Interlayer fracture toughness can be described as the general resistance of a material to interlayer fracture.

In this exemplary embodiment, "delamination" or delamination is the undesired separation of two layers of material. For example, interlayer fracture is the separation of two composite plies. As another example, interlayer fracture can occur between two of a plurality of adhesive layers 152. In some cases, interlayer fracture can occur due to high out-of-plane loads due to high peel stresses at the edges of the structure 136 under bending loads. The fluctuating tapered adhesive section is designed to effectively minimize these peel stresses.

In an exemplary embodiment, the interlayer fracture toughness can be a value determined by the type of interlayer fracture design 184 selected for the material. In this example, the interlayer failure design 184 refers to the configuration of each region designed to resist interlayer failure.

In this illustrated example, the interlayer failure design 184 for each of the regions 158 is the order of the orientation of the plies, the type of resin or matrix material used in each region, and the multiple adhesive layers in each of the tapered adhesive sections 156. It may include properties such as thickness 160 of 152, width 162 of each of the plurality of adhesive layers 152 of the tapered adhesive section 156, the position and sides of the gap 173, and other design characteristics.

The interlayer failure design 184 for each tapered bonding section 156 can have one of the mode I characteristics, the mode II characteristics, and the mode III characteristics. For example, each of the tapered adhesive sections 156 can be designed to resist tensile and shear loads (mode I), shear loads (mode II), or tensile and shear loads (mode III) in the desired manner.

In this illustrated example, structural shape 186 is the geometry of each region within the composite rework patch 150 and the tapered adhesive section 156. For example, but not limited to, the composite rework patch 150 may have a structural shape 186 selected from one of a circular, rectangular, square, or other suitable shape. The structural shape 186 of the tapered adhesive section 156 may be the same as or different from the corresponding region of the composite rework patch 150.

In some exemplary examples, the structural shape 186 of the composite rework patch 150 can vary between multiple regions 158. For example, one region may have a circle and the other region may have a rectangle. In another exemplary embodiment, the structural shape 186 for each region may be the same.

Using property 180, the patch system 132 can be designed to include a tapered adhesive section 156 to prevent the growth of inconsistent areas 144 in the structure 136. In particular, the structural property 182 of the tapered adhesive section 156 can help reduce the expansion of cracks 146 in the structure 136.

In some cases, when the structure 136 is a metal structure 140, the tapered adhesive section 156 can reduce the stress strength at the crack tip 148 at each end of the crack 146. In this exemplary embodiment, the stress intensity 188 is the amount of stress near the crack tip 148 caused by the load 178. A reduced stress strength of 188 is desired to prevent the growth of cracks 146.

The figure of the patch system 132, including the tapered adhesive section 156 of FIG. 19, is not intended to suggest physical or structural limitations to the methods in which the exemplary embodiments can be implemented. Other components may be used in addition to or in place of the components shown. Some components may be optional. Block diagrams are also presented to show some functional components. When implemented in an exemplary embodiment, one or more of these blocks may be combined, divided, or combined and divided into different blocks.

Next, with reference to FIG. 20, a diagram of the joined composite rework patch is shown according to an exemplary embodiment. In this illustrated example, an enlarged view of the composite rework patch 119 of FIG. 18 is shown. The composite rework patch 119 is joined to the composite structure 24 so as to cover the inconsistent area 22. In this exemplary embodiment, the composite rework patch 119 includes an area 200 arranged to cover the tapered adhesive section 202.

Region 200 is shown between the solid lines in this figure. In particular, the composite rework patch 119 includes a central portion 203, a first region 204, a second region 206, and a third region 208. Each subsequent region extends circumferentially around the previous region.

In this exemplary embodiment, the tapered adhesive section 202 is shown between the dashed lines. The tapered adhesive section 202 includes a first section 210, a second section 212, and a third section 214 in this exemplary embodiment.

As shown, the tapered adhesive section 202 substantially corresponds to region 200 of the composite rework patch 119. The corresponding tapered adhesive sections and patch areas are sometimes collectively referred to as "adhesive patch areas".

As shown, each of the individual tapered bonding sections 202 has different interlayer fracture toughness. In this exemplary embodiment, the third section 214 is about 4.5 in-lbs / in.²It has a mode I interlayer fracture toughness, and the second section 212 is about 13.5 in-lbs / in.²It has a mode II interlayer fracture toughness, and the first section 210 is about 20.5 in-lb / in.²It has the interlayer fracture toughness of Mode III. Other values of interlayer fracture toughness may be achieved depending on the particular embodiment.

In the illustrated examples, the region 200 can also be designed to have different levels of interlayer fracture toughness. For example, the interlayer fracture toughness of the third region 208 is about 1.75 in-lb / in.²From about 2.5 in-lb / in²Can be up to. The interlayer fracture toughness of the second region 206 is about 2.5 in-lb / in.²From about 3.5 in-lb / in²The first region 204, in this exemplary embodiment, is about 5.00 in-lb / in, whereas the first region 204 can be up to.²It can have the above interlayer fracture toughness. Thus, each of the different regions 200 of the ply and each of the different bonding sections applies strain energy at different rates from the composite structure 24 to the composite rework patch 119 to prevent the growth of the inconsistent area 22. It may have different properties configured to release.

FIG. 21 shows a partial cross-sectional view of the tapered adhesive section according to an exemplary embodiment. This illustrated example shows a cross-sectional view of the composite rework patch 119 along lines 21-21 of FIG. In particular, a cross-sectional view of the tapered adhesive inside the first section 210 is shown.

As shown, the composite rework patch 119 includes a composite layer 220 and an adhesive layer 222. In this exemplary embodiment, for simplicity, different plies inside the composite layer 220 are not shown. In this example, the tapered adhesive section includes several adhesive layers 222.

As illustrated, the first section 210 has a variable tapered thickness-to-width ratio as it tapers from the thickest to the thinnest. The adhesive layer 222 includes a high-variable tapered adhesive 221, an intermediate-variable tapered adhesive 223, and a small-variable tapered adhesive 225, and a tapered adhesive configuration is formed in the first section 210.

In this exemplary embodiment, there are no gaps between the adhesive layers 222. Further, a flat and uniform adhesive layer 224 is positioned directly on the mismatched area 22 so as to cover the central portion 203.

Inner Adhesion-Inside patch areas 210-204, airframe loads are transferred from inconsistent area 22 to compound rework patch 119. This region distributes the load first entering from the crack tip boundary 217-219 in the mismatched area 22 and minimizes the force at the crack tip. This effect is achieved by an increase in Mode III shear-shear capability combined with an improved Poisson's ratio elastic constant and a decrease in interlayer stress, as shown in FIGS. 22 and 23.

Thus, the adhesive-patch regions 210-204 substantially prevent unwanted structural plastic deformation in the composite rework patch 119. As a result, this region enhances and improves the damage resistance of the composite rework patch 119 to prevent the expansion of the inconsistent area 22. In addition, this region reduces or eliminates "thawing" of composite rework patches under various aerodynamic loads. "Thaw" can disjoint between the composite rework patch and the composite structure 24.

Next, referring to FIG. 22, a graph of interlayer tensile stress inside the joining patch is shown according to an exemplary embodiment. In this exemplary embodiment, graph 226 shows the out-of-plane interlayer tensile stress inside the composite rework patch 119.

As illustrated, Graph 226 shows distance vs. interlayer tensile stress (psi) across patch overlaps. In this example, the out-of-plane tensile stress inside the composite rework patch 119 is negative.

As shown by graph 226, the tapered adhesive layer 222 limits the stress profile. In short, the stress dispersion is reduced as a result of the inclination of the adhesive layer 222 so that the stress is less than the driving force. Compared to some currently used systems that do not have a tapered adhesive layer 222, an exemplary embodiment blocks driving force and prevents crack propagation.

Next, referring to FIG. 23, a graph of interlaminar shear stress inside the joint patch is shown according to an exemplary embodiment. In this exemplary embodiment, graph 227 shows the shear stress distribution inside the composite rework patch 119.

As illustrated, graph 227 shows distance vs. interlayer shear stress (psi) across patch overlaps. As shown by graph 227, the tapered adhesive layer 222 reduces the peak interstitial shear stress inside the composite rework patch 119. This reduction enhances the damage resistance and fatigue durability of the patch covering the inconsistent area 22.

In FIG. 24, an overall cross-sectional view of the joined composite rework patch on the composite structure is shown according to an exemplary embodiment. This illustrated example shows a cross section of the composite rework patch 119 along lines 24-24 of FIG.

Each of the tapered adhesive sections 202 has a tapered adhesive layer in this exemplary embodiment. In particular, the first section 210 has an adhesive layer 222, the second section 212 has an adhesive layer 228, and the third section 214 has an adhesive layer 229. The adhesive layer 228 and the adhesive layer 229 can be tapered in the same way as or differently from the adhesive layer 222.

Three adhesive layers are shown in each of the tapered adhesive sections 202, but there may be a number of other layers. There can be 5 layers, 9 layers, 14 layers, or another number of layers. Also, although three composite plies are shown in the composite layer 220, other numbers of plies may be used. Also, gaps may be present between the tapered adhesive sections 202 in some exemplary embodiments.

With the configurations shown in FIGS. 20-24, the composite rework patch 119 operates in the desired manner. Inner Adhesion-Inside patch areas 210-204, airframe loads are transferred from inconsistent area 22 to composite rework patch 119 to disperse the first incoming load from the crack tip boundary, as shown in Figures 21-23. Minimize the force at the crack tip, as illustrated and described with reference.

Adhesion-patch regions 212-206 in the middle of Mode II reduce the in-plane strain energy release rate of the inconsistent area 22. Thus, the adhesive-patch regions 212-206 reduce the rate of interfacial and interfacial growth of the mismatched area 22. This area enhances the fatigue durability of the entire composite skin of the airframe. As a result, the composite structure 24 can effectively carry the limiting load.

The outer adhesive-patch areas 214-208 are designed to minimize and control the thawing effect of the composite rework patch 119. Outer Adhesion-Patch Areas 214-208 are designed to mitigate the effects of high off-plane standard damage loads. This control is achieved by designing a combination of high mode I interlayer fracture toughness, elastic constants, and varying taper angles. This region is effective in reducing the strain energy release rate in the mismatched area 22 by redistributing the load on the aircraft skin. As a result, the adhesive-patch areas 214-208 maintain static strength under various aerodynamic conditions such as high gust loads and maneuvering flight loads.

Here, with reference to FIG. 25, a diagram of the joined composite rework patch is shown according to an exemplary embodiment. In this illustrated example, an enlarged view of the composite rework patch is shown. The composite rework patch 230 has been replaced with a composite rework patch 119 that covers the inconsistent area 22 in the composite structure 24.

The composite rework patch 230 is an example of another embodiment for the patch system 132 shown in the block format of FIG. The composite rework patch 230 is joined to the composite structure 24 so as to cover the inconsistent area 22.

In this exemplary embodiment, the composite rework patch 230 has a region 232 arranged to cover the tapered adhesive section 234. The region 232 shown between the solid lines includes the central region 236, the first region 238, the second region 240, the third region 242, and the fourth region 244. Each subsequent region extends circumferentially around the previous region.

In this exemplary embodiment, the tapered adhesive section 234 is shown between the dashed lines. The tapered adhesive section 234 includes a first section 246, a second section 248, a third section 250, and a fourth section 252 in this exemplary embodiment. As shown, the tapered adhesive section 234 substantially corresponds to region 232 of the composite rework patch 230.

As shown, each of the individual tapered bonding sections 234 has different interlayer fracture toughness. In this exemplary embodiment, the fourth section 252 is about 4.5 in-lbs / in.²It has a mode I interlayer fracture toughness, and the third section 250 is about 7.5 in-lbs / in.²It has a mode I interlayer fracture toughness, and the second section 248 is about 13.5 in-lb / in.²It has a mode II interlayer fracture toughness, and the first section 246 is about 20.5 in-lb / in.²It has the interlayer fracture toughness of Mode III. Other values of interlayer fracture toughness may be achieved depending on the particular embodiment.

Region 232 of the composite rework patch 230 can be substantially similar in interlayer fracture toughness to region 200 illustrated and described in FIG. In addition, the interlayer fracture toughness of the fourth region 244 is lower than the interlayer fracture toughness of the third region 242. In other exemplary examples, other values may be used.

In addition, the respective designs of region 232 and tapered adhesive section 234 may be modified based on the various loads applied to the substructure. For example, the design of a composite rework patch can vary based on where the composite rework patch is used on the aircraft. As an example, the structural design of a composite rework patch may differ when used on the structural skin panel of the wing than when used on the structural tail. As a result, one or more of the properties of region 232, the tapered adhesive section 234, or both can be modified to achieve the desired performance.

The various drawings shown in FIGS. 20-25 are shown to illustrate some of the various designs that can be provided by using exemplary embodiments. Also, various other configurations may be used to develop the desired structural properties of the composite rework patch 230.

In addition, similar configurations of patches may be used during metal application to patch metal structures. In such cases, the patch will be designed to reduce the stress strength in the inconsistent area. In particular, the tapered adhesive region is designed to prevent crack growth and extend the functional life of the patch by reducing stress strength at the crack tip.

The figures and descriptions of the composite rework patch 30, the composite rework patch 119, and the composite rework patch 230 of FIGS. 1 to 16 and 19 to 25 are the physical or structural to the methods in which the exemplary embodiments can be implemented. It is not intended to suggest a target limitation. Other components may be used in addition to or in place of the components shown. Some components may be optional.

The different components shown in FIGS. 1 to 16 and 20 to 25 are examples showing how the components shown in the block format of FIG. 19 can be implemented as physical structures. sell. In addition, some of the components of FIGS. 1-16 and 20-25 can be combined with, used with, or combined with the components of FIG.

Here, with reference to FIG. 26, a flow chart of the process for reworking a composite structure using a patch system with tapered adhesive sections is shown according to an exemplary embodiment. The process shown in FIG. 26 can be performed in the rework environment 130 of FIG. Different actions can be performed to form the patch system 132 on the structure 136 to prevent the growth of the inconsistent area 144.

In step 270, a plurality of adhesive layers are applied to the inconsistent area on the composite structure to form a tapered adhesive section. Multiple adhesive layers may be applied such that each of the tapered adhesive sections has different structural properties, different thickness-to-width ratios, or other suitable parameters.

The composite ply group is laid up in step 272 to form a composite rework patch that includes multiple regions with different structural properties. In step 274, the composite ply group and the tapered adhesive section are cured so that the tapered adhesive section reduces the spread of inconsistencies in the composite structure.

The flow charts and block diagrams in the different embodiments illustrated show the structure, function, and operation of some possible embodiments of the devices and methods of the exemplary embodiments. In this regard, each block in a flowchart or block diagram may represent at least one of a module, segment, function, or part or combination of action tails or steps.

In some alternative embodiments of the exemplary embodiments, one or more functions described in the blocks may occur out of the order shown in the figures. For example, in some cases, two blocks shown in succession may be executed at substantially the same time, or sometimes the blocks may be executed in reverse order depending on the functions included. In addition to the blocks depicted in the flowchart or block diagram, other blocks may be added.

An exemplary embodiment of the present disclosure may be described in connection with the aircraft manufacturing and maintenance method 300 shown in FIG. 27 and the aircraft 320 shown in FIG. First, with reference to FIG. 27, aircraft manufacturing and maintenance methods are illustrated according to exemplary embodiments. In the pre-manufacturing phase, the aircraft manufacturing and maintenance method 300 may include the specification and design 302 of the aircraft 301 of FIG. 28 and the material procurement 304.

During the manufacturing phase, the components and subassemblies of aircraft 301 in FIG. 28 are manufactured 306 and system integration 308 is performed. The aircraft 301 of FIG. 28 may then undergo approval and delivery 310 to be put into service 312. During customer service 312, Aircraft 301 in Figure 28 is scheduled for regular maintenance and maintenance 314, which may include modifications, reconstructions, refurbishments, and other maintenance or maintenance.

Each process of aircraft manufacturing and maintenance method 300 may be performed or performed by a system integrator, a third party, an operator, or a combination thereof. In these examples, the operator may be a customer. For the purposes of this specification, system assemblers include, but are not limited to, any number of aircraft manufacturers, and major system subcontractors, and third parties, but not limited to, any number of vendors, subcontractors. , And suppliers, and workers can be airlines, leasing companies, military organizations, service agencies, and so on.

Here, with reference to FIG. 28, a diagram of an aircraft in which an exemplary embodiment can be implemented is shown. In this example, the aircraft 301 may include an airframe 316 manufactured by the aircraft manufacturing and maintenance method 300 of FIG. 27 and having a plurality of systems 318 and interior 320. Examples of system 318 include one or more of propulsion system 322, electrical system 324, hydraulic system 326, and environmental system 328. Any number of other systems may be included. Although an example of the aerospace industry is illustrated, different exemplary embodiments may also apply to other industries such as the automotive industry.

The devices and methods embodied herein can be used in at least one of the aircraft manufacturing and maintenance methods 300 of FIG. In particular, the patch system 132, including the tapered bonding section 156 of FIG. 19, can be installed at any one of the stages of aircraft manufacturing and maintenance method 300. For example, a patch system 132, including, but not limited to, a tapered adhesive section 156, is an aircraft at another stage of component and subassembly manufacturing 306, regular maintenance and maintenance 314, or aircraft manufacturing and maintenance method 300. Can be used to rework the structure of 301.

For example, patch system 132 can be used to find inconsistent areas in the structure of aircraft 301. This inconsistent area may have formed during the manufacture of components and subassemblies 306. Instead of disposing of the structure, the area is patched using patch system 132 and can still meet applicable criteria.

As another exemplary embodiment, inconsistent areas within the structure of Aircraft 301 may be found during regular maintenance and maintenance 314. In this case, the patch system 132 may be used instead of reworking all of the structure or replacing the structure. By using the tapered adhesive section 156, not only the structure of the aircraft 301 but also the life of the patch system 132 can be extended.

In one exemplary embodiment, the components or subassemblies manufactured during the manufacture of components and subassemblies in FIG. 27 are the components or subassemblies manufactured during the operation 312 of aircraft 301 in FIG. 27. It can be produced or manufactured in a similar manner. In yet another example, embodiments of one or more devices, embodiments of methods, or combinations thereof may be utilized in manufacturing steps such as manufacturing 306 and system integration 308 of the components and subassemblies of FIG. it can. Embodiments of one or more devices, embodiments of methods, or combinations thereof, may be utilized by Aircraft 301 during flight 312, maintenance and maintenance 314 in FIG. 27, or combinations thereof. The use of several different exemplary embodiments makes it possible to significantly streamline the assembly of aircraft 301, reduce costs, or both.

Accordingly, exemplary embodiments provide methods and devices for reworking structures. The structure can take the form of the composite structure 138 of the aircraft 134 of FIG. In one exemplary embodiment, the device comprises a composite rework patch 150 and a plurality of adhesive layers 152 on a first side surface 154 of the composite rework patch 150. The first side surface 154 of the composite rework patch 150 has an outer shape 157 that matches the inconsistent area 144 on the structure 138. The composite rework patch 150 includes a plurality of regions 158 with different structural properties 182. The plurality of adhesive layers 152 vary in thickness 160 within at least one region of the composite rework patch 150 to form the tapered adhesive section 156.

An exemplary embodiment is in a composite layer tuned to form a structural patch designed to substantially delay and prevent multi-site skin cracks and complex delamination of various models of aircraft. It provides a combination of integrated multi-structure recognized adhesives. This intricately combined and integrated composite adhesive rework with the outer region of static strength, the intermediate region of durable strength, and the inner central region with fail-safe damage resistance, as described in FIGS. 1-16. A patch (This combined complex integrated composite-adhesive rework patch) releases strain energy in the desired manner. As a result, patches last longer than some currently used systems and provide better structural integrity.

In addition, the integrated adhesive patch is designed with various taper angles in the adhesive, which reduces and reduces high damage interlayer shear and tensile stress at the cracked skin boundary. No bolts are used in the exemplary embodiments. As a result, the exemplary embodiment improves the overall structural damage tolerance capacity of the underlying composite skin.

With the introduction of the tapered adhesive area, the composite rework patch will meet the airworthiness standards published by the Federal Aviation Administration (FAA) and the European Union Aviation Safety Agency (EASA), among others. For example, the patch qualifies for FAA Federal Airline Regulation (FAR) 25-571e rating as a structurally integrated airframe or wing repaired skin capable of carrying a 150% limit load. become. The exemplary embodiments also meet a variety of other EASA and FAA airworthiness standards.

The description of the various exemplary embodiments described above is presented for purposes of illustration and description and is intended to be an exhaustive description or to limit these embodiments to the disclosed embodiments. Not. Many modifications and variations will be apparent to those skilled in the art. In addition, various exemplary embodiments can provide other advantages in the light of other preferred embodiments. The selected embodiment is intended to best explain the principles of the embodiment, the actual use, and to other skill in the art for a particular use considered to be the disclosure of the various embodiments. Selected and described to facilitate understanding of various suitable modifications.<u style="single"> In addition, the disclosure includes embodiments under the following provisions.</u><u style="single">(Clause 1)</u><u style="single"> A patch system for reworking structural inconsistencies</u><u style="single"> With patches containing multiple regions with different structural properties,</u><u style="single"> With a plurality of adhesive layers on the patch, the thickness of which varies within at least one region of the patch to form a tapered adhesive section.</u><u style="single">Patch system including.</u><u style="single">(Clause 2)</u><u style="single"> The patch system according to Clause 1, wherein the structure is a metal structure.</u><u style="single">(Clause 3)</u><u style="single"> The patch system according to Clause 2, wherein the tapered adhesive section reduces the stress strength in the mismatched area of the metal structure.</u><u style="single">(Clause 4)</u><u style="single"> The patch system according to Clause 1, wherein each of the tapered adhesive sections has different interlayer toughness.</u><u style="single">(Clause 5)</u><u style="single"> The patch system according to Clause 1, wherein the inconsistent area of the structure comprises a crack and the tapered adhesive section reduces the force at the tip of the crack in order to substantially prevent the expansion of the crack.</u>