Composite panels with titanium ends

Abstract

To provide a composite structure.SOLUTION: A composite structure and methods of forming are presented. A composite structure comprises: structural supports and a structural skin formed by a plurality of composite panels fastened to the structural supports. Each composite panel of the plurality of composite panels comprises: a first titanium end; a second titanium end; and a composite skin joined to and extending between the first titanium end and the second titanium end.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 660,313, filed June 14, 2024, which is incorporated herein by reference in its entirety. This application is related to the following U.S. patent application entitled "Metal to Composite Joints," Serial No. ________, Attorney Docket No. 23-2202-US-NP, filed on even date herewith, assigned to the same assignee, and incorporated herein by reference in its entirety:

[0002] 1. Field FIELD OF THE DISCLOSURE The present disclosure relates generally to composite skins, and more particularly to composite panels. [Background technology]

[0003] 2.Background Composite manufacturing presents challenges for large structures. Traditionally, large composite skins have been manufactured as a single, large, continuous piece. Manufacturing large, continuous composite skins can present challenges for maintaining timelines, reducing costs, and maintenance or repair.

[0004] Manufacturing a composite skin as multiple separate pieces presents challenges in joining: conventional fasteners introduce mismatch points within the composite skin. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the above-mentioned problems, as well as other possible problems. It would be desirable to have an improved method of composite manufacturing. It would be desirable to have a method of manufacturing composite skins. [Means for solving the problem]

[0006] One embodiment of the present disclosure provides a composite structure comprising a structural support and a structural skin comprising a composite panel fastened to the structural support, the composite panel comprising a first titanium end, a second titanium end, and a composite skin joined to the first titanium end and the second titanium end and extending between the first titanium end and the second titanium end.

[0007] Another embodiment of the present disclosure provides a composite structure comprising a composite panel fastened to the composite structure at titanium edges, the composite panel comprising two titanium edges and a composite skin joined to and extending between the two titanium edges.

[0008] Yet another embodiment of the present disclosure provides a method of forming a composite structure, the method including: bonding composite skins to respective first titanium ends and respective second titanium ends to form a plurality of composite panels; and fastening the plurality of composite panels to structural supports to form a structural skin of the composite structure.

[0009] Yet another embodiment of the present disclosure provides a method for accessing an interior volume of a composite structure. Fasteners on one side of a composite panel are released. The composite panel includes a first titanium end, a second titanium end, and a composite skin joined to the first titanium end and the second titanium end and extending between the first titanium end and the second titanium end. The composite panel is removed from the composite structure to create an opening after the fasteners on one side are released. The interior volume of the composite structure is accessed through the opening.

[0010] The above forms and functions may be realized independently in various embodiments of the present disclosure or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings.

[0011] The novel features believed characteristic of the exemplary embodiments are set forth in the appended claims. However, the exemplary embodiments, as well as preferred modes of use, further objects and features of these exemplary embodiments, will best be understood by reference to the following detailed description of exemplary embodiments of the present disclosure when read in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an illustration of an aircraft in accordance with an illustrative embodiment; [Figure 2] FIG. 1 is a block diagram of a manufacturing environment in accordance with an illustrative embodiment. [Figure 3] 1 is a top view of an aircraft wing having a wing skin comprising a plurality of composite panels in accordance with an illustrative embodiment; [Figure 4] 1 is an illustration of a cross section of a composite panel having a metal to composite joint according to an illustrative embodiment; [Figure 5] FIG. 1 is an illustration of a cross-sectional view of a composite panel fastened to a structural support in accordance with an illustrative embodiment. [Figure 6] FIG. 1 is a block diagram of a manufacturing environment in accordance with an illustrative embodiment. [Figure 7] 1 is an illustration of a cross-sectional view of a metal to composite joint in accordance with an illustrative embodiment; [Figure 8] 1 is an illustration of a cross-sectional view of a metal to composite joint in accordance with an illustrative embodiment; [Figure 9] 1 is an illustration of a cross-sectional view of a metal to composite joint in accordance with an illustrative embodiment; [Figure 10] 1 is a flowchart of a method for forming a composite structure in accordance with an illustrative embodiment. [Figure 11] 1 is a flowchart of a method for accessing an interior volume of a composite structure in accordance with an illustrative embodiment. [Figure 12] FIG. 1 is an illustration of an aircraft manufacturing and service method in the form of a block diagram in accordance with an illustrative embodiment. [Figure 13] FIG. 1 is an illustration of an aircraft in the form of a block diagram in which an illustrative embodiment may be implemented; DETAILED DESCRIPTION OF THE INVENTION

[0013] The illustrative examples recognize and take into account one or more considerations. The illustrative examples recognize and take into account that in an aircraft, a metal-to-composite joint can be used to join a wing to the aircraft fuselage. The illustrative examples recognize and take into account that a metal-to-composite joint can be a step-lap joint between a composite ply and a metal component. The illustrative examples recognize and take into account that in large structures, metal-to-composite joints present manufacturing challenges.

[0014] The illustrative example recognizes and takes into account that gaps can be created at each step of the step-lap metal-to-composite joint, allowing air to be introduced into the laminate. The illustrative example recognizes and takes into account that on thick, large parts, it can be unnecessarily difficult to evacuate air and volatiles within the laminate at the steps during fabrication and autoclave curing. Residual air and volatiles can result in undesirable conditions, such as porosity. To reduce inconsistencies, multiple curing cycles may be used, which increases cycle time and utilizes more resources.

[0015] The illustrative examples recognize and take into account that smaller composite parts have less of a problem emitting volatiles. The illustrative examples recognize and take into account that smaller composite parts have fewer volatiles because volatiles travel between the plies as opposed to through the thickness. The illustrative examples recognize and take into account that air / volatiles travel significantly better between the plies than through the thickness.

[0016] The illustrative examples recognize and take into account that volatiles cannot migrate through titanium. The illustrative examples recognize and take into account that hybrid titanium composite parts help reduce weight when compared to titanium parts.

[0017] Illustrative examples provide new designs that include titanium and carbon fiber composites that may be used in airplane wing skins. In these illustrative examples, the titanium is spliced ​​to at least one edge of a large composite structure.

[0018] The illustrative example presents a metal-to-composite joint having two or more titanium components through the thickness. The illustrative example "splits" a large titanium part into two pieces to allow for composite between them. The illustrative example provides an escape path for air and volatiles through the composite layer between the titanium parts.

[0019] Illustrative examples improve both the manufacturability and damage tolerance of titanium and composite structures. Separating titanium and using composite layers between titanium components helps manage scale for designs with titanium on the inboard sides of large wing skins or other sizeable parts. Illustrative examples may be used on the inboard and outboard ends of wing skins to reduce weight.

[0020] Turning now to Figure 1 , an illustration of an aircraft is shown in accordance with an illustrative embodiment. Aircraft 100 has wing 102 and wing 104 attached to fuselage 106. Aircraft 100 includes engine 108 attached to wing 102 and engine 110 attached to wing 104.

[0021] The fuselage 106 has a tail section 112. A horizontal stabilizer 114, a horizontal stabilizer 116, and a vertical stabilizer 118 are attached to the tail section 112 of the fuselage 106.

[0022] Aircraft 100 is an example of an aircraft that may have composite panels. The illustrative example composite panels may be used to form wing skins for at least one of wing 102 and wing 104.

[0023] Turning now to Figure 2, an illustration of a block diagram of a manufacturing environment is depicted in accordance with an illustrative embodiment.

[0024] Composite structure 202 comprises structural supports 254 and a structural skin 266 comprising composite panels 212 fastened to structural supports 254. Composite panel 212 of the plurality of composite panels 210 comprises a first titanium end 214, a second titanium end 216, and a composite skin 218 joined to and extending between first titanium end 214 and second titanium end 216. Structural skin 266 comprises any desired number of composite panels and is not limited by the depiction provided in the figures.

[0025] In some illustrative examples, composite structure 202 comprises structural supports 253 and a structural skin 266 formed by a plurality of composite panels 210 fastened to structural supports 253. Each composite panel of plurality of composite panels 210 comprises a first titanium end, a second titanium end, and a composite skin joined to the first and second titanium ends and extending between the first and second titanium ends. For example, composite panel 212 of plurality of composite panels 210 comprises a first titanium end 214, a second titanium end 216, and a composite skin 218 joined to the first and second titanium ends 214, 216 and extending between the first and second titanium ends 214, 216. As another example, composite panel 224 of plurality of composite panels 210 comprises first titanium end 226, second titanium end 228, and composite skin 230 joined to first titanium end 226 and second titanium end 228 and extending between first titanium end 226 and second titanium end 228. As yet another example, composite panel 236 of plurality of composite panels 210 comprises first titanium end 238, second titanium end 240, and composite skin 242 joined to first titanium end 238 and second titanium end 240 and extending between first titanium end 238 and second titanium end 240.

[0026] In each composite panel of the plurality of composite panels 210, the composite skin is joined to the first titanium end and the second titanium end in any desired manner. In some illustrative examples, in at least one composite panel of the plurality of composite panels 210, the respective composite skin is bonded to the first titanium end and the second titanium end. In some illustrative examples, in at least one composite panel of the plurality of composite panels 210, the respective composite skin is bonded to the first titanium end and the second titanium end. In some illustrative examples, in at least one composite panel of the plurality of composite panels 210, the respective composite skin is fastened to the first titanium end and the second titanium end.

[0027] Composite structure 202 may take any desirable form. In some illustrative examples, the composite structure may form part of or all of a mobile platform, a fixed platform, a land structure, an aquatic structure, a space structure, an aircraft, a commercial aircraft, a rotorcraft, a tiltrotor aircraft, a tiltwing aircraft, a vertical take-off and landing aircraft, a powered vertical take-off and landing vehicle, a personal air vehicle, a tanker aircraft, a surface ship, a tank, a personnel carrier, a train, a spacecraft, a space station, a satellite, a submarine, an automobile, a power plant, a bridge, a dam, a house, a manufacturing facility, a building, a robot, a robotic arm, a crane, or other suitable type of structure.

[0028] In some illustrative examples, composite structure 202 may be aircraft 204. In some illustrative examples, composite structure 202 is wing 206 of aircraft 204. In some illustrative examples, structural skin 266 comprises wing skin 208 of aircraft 204.

[0029] In certain illustrative examples, each composite panel further comprises a first stepped lap joint between the first titanium end and the composite skin and a second stepped lap joint between the second titanium end and the composite skin. For example, composite panel 212 further comprises stepped lap joint 220 between first titanium end 214 and composite skin 218 and stepped lap joint 222 between second titanium end 216 and composite skin 218. For example, composite panel 224 further comprises stepped lap joint 232 between first titanium end 226 and composite skin 230 and stepped lap joint 234 between second titanium end 228 and composite skin 230. For example, composite panel 236 further comprises stepped lap joint 244 between first titanium end 238 and composite skin 218 and stepped lap joint 222 between second titanium end 216 and composite skin 218.

[0030] Structural supports 253 can take any desired form. In some illustrative examples, structural supports 253 comprise ribs. In some illustrative examples, structural supports 253 comprise spars. Structural supports 253 include any desired material. In some illustrative examples, structural supports 253 include metal. In some illustrative examples, structural supports 253 include titanium. In some illustrative examples, structural supports 253 include a material other than titanium. In some illustrative examples, when structural supports 253 are a material other than titanium, a titanium splice plate is present between structural supports 253 and the plurality of composite panels 210.

[0031] In some illustrative examples, composite panel 212 and composite panel 224 are fastened to structural support 254. In some illustrative examples, composite panel 212 and composite panel 224 are fastened directly to structural support 254. In some illustrative examples, second titanium end 216 of composite panel 212 and first titanium end 226 of composite panel 224 are fastened directly to structural support 254. In some illustrative examples, composite panel 212 and composite panel 224 are fastened to titanium splice plate 248 and structural support 254.

[0032] In some illustrative examples, composite panel 224 and composite panel 236 are fastened to structural support 256. In some illustrative examples, composite panel 224 and composite panel 236 are fastened directly to structural support 256. In some illustrative examples, second titanium end 228 of composite panel 224 and first titanium end 238 of composite panel 236 are fastened directly to structural support 256. In some illustrative examples, composite panel 224 and composite panel 236 are fastened to titanium splice plate 250 and structural support 256.

[0033] In some illustrative examples, each composite panel of plurality of composite panels 210 is removably fastened to a titanium splice plate of a plurality of titanium splice plates. In this illustrative example, composite panel 212 is fastened to titanium splice plate 248. In this illustrative example, composite panel 224 is attached to titanium splice plate 248 and titanium splice plate 250. In this illustrative example, composite panel 236 is attached to titanium splice plate 250.

[0034] Composite structure 202 further includes fasteners 264 extending through first and second titanium ends of each composite panel to connect the plurality of composite panels 210 to structural support 253. Fasteners 264 extend through second titanium ends 216 of composite panel 212 to connect composite panel 212 to structural support 253. Fasteners 264 extend through first and second titanium ends 226, 228 of composite panel 224 to connect composite panel 224 to structural support 253. Fasteners 264 extend through first titanium ends 238 of composite panel 236 to connect composite panel 236 to structural support 253.

[0035] In some illustrative examples, fasteners 264 are single-sided fasteners 270. Single-sided fasteners 270 allow single-sided fasteners 270 to be installed from one side of each composite panel. Single-sided fasteners 270 provide the advantage of not needing to access the inside of composite structure 202 for each composite panel.

[0036] In some illustrative examples, at least one composite panel of plurality of composite panels 210 includes two or more titanium structural components forming one of first titanium end and second titanium end. In this illustrative example, composite panel 236 of plurality of composite panels 210 includes two or more titanium structural components forming second titanium end. In this illustrative example, composite panel 236 includes titanium structural component 258 forming second titanium end 240.

[0037] In some illustrative examples, a segmented set of composite plies extends between two or more titanium structural components to provide an escape path for volatiles. In this illustrative example, a segmented set of composite plies 259 extends between titanium structural components 258 to provide an escape path 260 for volatiles 262. While only one titanium edge is shown as having multiple titanium structural components, in some illustrative examples, two or more titanium edges include multiple titanium structural components. In some illustrative examples, each composite panel in plurality of composite panels 210 has at least one titanium edge that includes multiple titanium structural components. In some illustrative examples, each composite panel in plurality of composite panels 210 has both titanium edges that include two or more titanium structural components, thereby providing each titanium edge with an escape path for volatiles.

[0038] In some illustrative examples, composite panels 210 comprise a plurality of access panels 252 removably connected to provide interior access to composite structure 202. In these illustrative examples, each of composite panels 210 is removable. Removing a composite panel of composite panels 210 provides access to composite structure 202 for performing maintenance or repairs within composite structure 202. In some illustrative examples, access panels 252 allow for servicing without accessing composite structure 202 through an opposing surface or opposing skin. For example, in the case of composite panels 210 from structural skin 266 on the top surface of composite structure 202, in some illustrative examples, servicing may be performed through the top surface without accessing through the bottom surface of composite structure 202.

[0039] To remove a composite panel, such as composite panel 212, the one-sided fasteners 270 of the composite panel are loosened. After unclamping the one-sided fasteners 270, the composite panel, such as composite panel 212, is removed from the composite structure 202 to create an opening 272. The interior volume 268 of the composite structure 202 can be accessed through the opening 272.

[0040] In some illustrative examples, composite structure 202 comprises a plurality of composite panels 210 fastened at respective titanium ends to composite structure 202. In some illustrative examples, each composite panel of plurality of composite panels 210 comprises two titanium ends and a composite skin joined to and extending between the two titanium ends.

[0041] The illustration of manufacturing environment 200 in FIG. 2 is not meant to imply physical or architectural limitations to the manner in which an illustrative embodiment may be implemented. Other components in addition to or in place of the illustrated components may be used. Some components may be unnecessary. Also, the blocks are presented to illustrate some functional components. One or more of these blocks may be combined, divided, or combined and divided into different blocks when implemented in an illustrative embodiment.

[0042] For example, although three composite panels are shown in plurality of composite panels 210, there may be any desired number of composite panels. In some illustrative examples, plurality of composite panels 210 comprises four or more composite panels. In some illustrative examples, plurality of composite panels 210 comprises fewer than three composite panels.

[0043] Turning now to Figure 3, an illustration of a top view of an aircraft wing having a wing skin comprising a plurality of composite panels is shown in accordance with an illustrative embodiment. View 300 may be a top view of wing 102 or wing 104 of aircraft 100 in Figure 1. View 300 may be a top view of wing 206 of aircraft 204 in Figure 2.

[0044] View 300 is a top view of a wing 318. Wing 318 has an inboard end 302 and an outboard end 304. Wing 318 is a physical implementation of composite structure 202 of FIG. 2. Wing 318 includes a structural support (not shown) and a structural skin 306 formed by a plurality of composite panels 305 fastened to the structural support. Each composite panel of the plurality of composite panels 305 includes a first titanium end, a second titanium end, and a composite skin joined to and extending between the first titanium end and the second titanium end.

[0045] In this illustrative example, plurality of composite panels 305 includes composite panel 308, composite panel 310, and composite panel 312. Each composite panel in plurality of composite panels 305 is fastened to a metal structural support. In this illustrative example, plurality of composite panels 305 is fastened at their titanium ends to wing 318.

[0046] In this illustrative example, composite panel 308 and composite panel 310 are joined at joint 314. In this illustrative example, composite panel 310 and composite panel 312 are joined at joint 316.

[0047] In this illustrative example, wing 318 takes the form of composite structure 320. In some illustrative examples, plurality of composite panels 305 comprises a plurality of access panels that are removably connected to provide interior access to composite structure 320. When plurality of composite panels 305 are removably connected to form a plurality of access panels, plurality of composite panels 305 provide interior access to wing 318.

[0048] Attention is now directed to Figure 4, which illustrates a cross-sectional view of a composite panel having a metal-to-composite joint, according to an illustrative embodiment. View 400 is a cross-sectional view of composite panel 401. Composite panel 401 may be a physical implementation of one of composite panels 210 in Figure 2. Composite panel 401 may be one of composite panels 305 in Figure 3.

[0049] Composite panel 401 includes titanium edges 404 joined to composite skin 402. Composite panel 401 includes first titanium edges 406, second titanium edges 408, and composite skin 402 joined to and extending between first titanium edges 406 and second titanium edges 408. In some illustrative examples, titanium edges 404 form inboard and outboard edges of composite panel 401.

[0050] Composite panel 401 includes first titanium edge 406, composite skin 402, and second titanium edge 408. Composite panel 401 includes first stepped lap joint 410 between first titanium edge 406 and composite skin 402, and second stepped lap joint 412 between second titanium edge 408 and composite skin 402.

[0051] Attention is now directed to Figure 5, which illustrates a cross-sectional view of a composite panel fastened to a structural support, according to an illustrative embodiment. View 500 is a cross-sectional view of a physical implementation of multiple composite panels 210 fastened to a structural support 253. View 500 may be a view within one of wing 102 and wing 104 of Figure 1. View 500 may be a cross-sectional view along BB of Figure 3. View 500 may be a cross-sectional view of an end of composite panel 401 of Figure 4 fastened to a structural support.

[0052] In view 500, composite panel 502 and composite panel 504 are fastened to structural support 506. In view 500, joint 501 is formed by fastening composite panel 502 and composite panel 504 to a structural support of a composite structure. In this illustrative example, fastener 510 extends through titanium end 516 of composite panel 502. Composite panel 502 is fastened to structural support 506 using fastener 510. In this illustrative example, fastener 512 extends through titanium end 520 of composite panel 504. Composite panel 504 is fastened to structural support 506 using fastener 512.

[0053] In this illustrative example, titanium splice plate 508 is present between composite panel 502 and structural support 506. Titanium splice plate 508 may be present to allow connection of titanium end 516 to a structural support 506 formed of a material other than titanium. In some illustrative examples, titanium splice plate 508 may allow connection of titanium end 516 to a structural support 506 formed of aluminum.

[0054] Turning now to FIG. 6 , a block diagram of a manufacturing environment is depicted in accordance with an illustrative embodiment. A metal-to-composite joint 610 of a platform 602 may be formed in manufacturing environment 600. The metal-to-composite joint 610 of the platform 602 may be a joint within a composite panel of the plurality of composite panels 210 of FIG. 2 . In some illustrative examples, the first metal structural component 612 and the second metal structural component 614 are titanium structural components 258 of FIG. 2 . The metal-to-composite joint 610 of the platform 602 may be a joint within a composite panel of the plurality of composite panels 305 of FIG. 3 . The metal-to-composite joint 610 of the platform 602 may be an alternative joint within a composite panel to those depicted in FIGS. 4 and 5 . In some illustrative examples, the metal-to-composite joint 610 may alternatively be present within the composite panel 401 of FIG. 4 . In some illustrative examples, metal to composite joint 610 may alternatively be present in at least one of composite panel 502 and composite panel 504 in Figure 5 .

[0055] Platform 602 can take a number of different forms. For example, platform 602 can be selected from the group including a mobile platform, a fixed platform, a land structure, an aquatic structure, a space structure, an aircraft, a commercial aircraft, a rotorcraft, a tilt rotor aircraft, a tilt wing aircraft, a vertical take-off and landing aircraft, a powered vertical take-off and landing vehicle, a personal air vehicle, a tanker aircraft, a surface ship, a tank, a personnel carrier, a train, a spacecraft, a space station, a satellite, a submarine, an automobile, a power plant, a bridge, a dam, a house, a manufacturing facility, a building, a robot, a robotic arm, a crane, and other suitable types of platforms.

[0056] In some illustrative examples, platform 602 may be aircraft 604. In some illustrative examples, platform 602 is wing 606 of aircraft 604.

[0057] 1 may be a physical implementation of aircraft 604. In some illustrative examples, if metal-to-composite joint 610 is part of aircraft 604, metal-to-composite joint 610 may connect wing 606 to fuselage 608 of aircraft 604.

[0058] The metal-to-composite joint 610 for the platform 602 comprises a first metal structural component 612 and a second metal structural component 614, with a segmented set of composite plies 622 between the first metal structural component 612 and the second metal structural component 614. As used herein, a "set" of an item means one or more items. The segmented set of composite plies 622 comprises one or more composite plies. The segmented set of composite plies 622 provides an escape path 624 for volatiles 623 within the metal-to-composite joint 610. The escape path 624 extends between layers within the metal-to-composite joint 610 for the platform 602.

[0059] The metal-to-composite joint 610 for the platform 602 includes a first metal structural component 612, a first set of composite plies 630, a second metal structural component 614, a second set of composite plies 632, and a split set of composite plies 622. The first metal structural component 612 includes a stepped surface 616 and a flat surface 618. The first set of composite plies 630 includes a joining surface that is complementary to the stepped surface 616 of the first metal structural component 612. The second metal structural component 614 includes a stepped surface 661 and a flat surface 620. The second set of composite plies 632 includes a joining surface that is complementary to the stepped surface 661 of the second metal structural component 614. The split set of composite plies 622 between the two metal structural components provides an escape path 624 for volatiles 623 between the two metal structural components. In some illustrative examples, first set of composite plies 630 are described as abutting stepped surface 616 of first metal structural component 612. In some illustrative examples, second set of composite plies 632 are described as abutting stepped surface 661 of second metal structural component 614.

[0060] In some illustrative examples, first set of composite plies 630 are complementary to first metal structural component 612 to form lap joint 642. Lap joint 642 comprises a faying surface 648 between first metal structural component 612 and first set of composite plies 630. In some illustrative examples, second set of composite plies 632 are complementary to second metal structural component 614 to form lap joint 643. Lap joint 643 comprises a faying surface 650 between second metal structural component 614 and second set of composite plies 632. Split set of composite plies 622 extends between first set of composite plies 630 and second set of composite plies 632.

[0061] In some illustrative examples, segmented set of composite plies 622 extends between and is bonded to the flat surfaces 618 of first metal structural component 612 and flat surface 620 of second metal structural component 614. In some illustrative examples, segmented set of composite plies 622 extends between and is bonded to the stepped surfaces 616 of first metal structural component 612 and stepped surface 661 of second metal structural component 614.

[0062] In some illustrative examples, first metal structural component 612 and second metal structural component 614 include titanium. As shown, first metal structural component 612 includes titanium 613. As shown, second metal structural component 614 includes titanium 615.

[0063] Metal-to-composite joint 610 comprises any desired number of metal structural components with split composite plies between them. In some illustrative examples, metal-to-composite joint 610 for platform 602 comprises two metal structural components forming a portion of a first surface 626 and a portion of a second surface 628 of metal-to-composite joint 610, and a split set of composite plies 622 between the two metal structural components that provide an escape path 624 for volatiles 623 between the two metal structural components.

[0064] In some illustrative examples, stepped surface 616 of first metal structural component 612 forms a portion of first surface 626. In some illustrative examples, flat surface 618 forms a portion of first surface 626. The remainder of first surface 626 is formed by first set of composite plies 630. In some illustrative examples, first ply stack 634 of first set of composite plies 630 forms a portion of first surface 626.

[0065] In some illustrative examples, stepped surface 661 of second metal structural component 614 forms a portion of second surface 628. In some illustrative examples, flat surface 620 forms a portion of second surface 628. The remainder of second surface 628 is formed by second set of composite plies 632. In some illustrative examples, first ply stack 634 of first set of composite plies 630 forms a portion of first surface 626.

[0066] First set of composite plies 630 comprises a faying surface 648 with first one of the metal structural components 612, and second set of composite plies 632 comprises a faying surface 650 with second one of the metal structural components 614, to form lap joint 642 and lap joint 643. In some illustrative examples, first set of composite plies 630 may be described as abutting first one of the metal structural components 612, and second set of composite plies 632 may be described as abutting second one of the metal structural components 614, to form lap joint 642 and lap joint 643. First set of composite plies 630 forms lap joint 642 with stepped surface 616 of first metal structural component 612. At lap joint 642, the ply stack of first set of composite plies 630 changes length to form a joint with stepped surface 616 of first metal structural component 612. Second set of composite plies 632 forms lap joint 643 with stepped surface 661 of second metal structural component 614. At lap joint 643, the ply stack of second set of composite plies 632 changes length to form a joint with stepped surface 661 of second metal structural component 614.

[0067] When stepped surface 616 forms a portion of first surface 626, first metal structural component 612 extends into first set of composite plies 630. When stepped surface 616 forms a portion of first surface 626, the longest ply of first set of composite plies 630 forms a portion of first surface 626. In these illustrative examples, length 635 of first ply stack 634 forming a portion of first surface 626 is longer than ply length 637 of second ply stack 636. Second ply stack 636 is further interior of metal-to-composite joint 610 in the direction of thickness 646 moving from first surface 626 to second surface 628.

[0068] When stepped surface 661 forms a portion of second surface 628, second metal structural component 614 extends into second set of composite plies 632. When stepped surface 661 forms a portion of second surface 628, the longest ply of second set of composite plies 632 forms a portion of second surface 628. In these illustrative examples, length 241 of fourth ply stack 640, which forms a portion of second surface 628, is longer than ply length 639 of third ply stack 638. Third ply stack 638 is further inside metal-to-composite joint 610 in the direction of thickness 646 moving from second surface 628 to first surface 626.

[0069] In these illustrative examples, first metallic structural component 612 and second metallic structural component 614 are seen to extend within the composite material of first set of composite plies 630 and second set of composite plies 632. In other illustrative examples, the composite material of first set of composite plies 630 and second set of composite plies 632 are seen to extend between first metallic structural component 612 and second metallic structural component 614.

[0070] When the composite material of the first set of composite plies 630 and the second set of composite plies 632 is viewed as extending between the first metal structural component 612 and the second metal structural component 614, the composite plies forming the first surface 626 and the second surface 628 have the shortest length of the first set of composite plies 630 and the second set of composite plies 632.

[0071] In some illustrative examples, segmented set of composite plies 622 is bonded to two metal structural components. In some illustrative examples, structural adhesive 644 is applied to at least one of segmented set of composite plies 622, first metal structural component 612, and second metal structural component 614.

[0072] Although not shown in metal-to-composite joint 610, a third metallic structural component may be present between the two metallic structural components. In these illustrative examples, split set 622 of composite plies is bonded to one of the two metallic structural components and to the third metallic structural component.

[0073] In some illustrative examples, the two metal structural components, the first metal structural component 612 and the second metal structural component 614, are symmetrical about the center of the metal-to-composite joint 610 in the direction of thickness 646. In other illustrative examples, the two metal structural components, the first metal structural component 612 and the second metal structural component 614, are asymmetrical about the center of the metal-to-composite joint 610 in the direction of thickness 646. In some illustrative examples, the two metal structural components, the first metal structural component 612 and the second metal structural component 614, have the same design. In other illustrative examples, the two metal structural components, the first metal structural component 612 and the second metal structural component 614, have different designs.

[0074] In some illustrative examples, structural adhesive 644 covers the faying surfaces of the two metal structural components, first set of composite plies 630 and second set of composite plies 632. In some illustrative examples, structural adhesive 644 extends at least partially between first set of composite plies 630 and segmented set of composite plies 622. In some illustrative examples, structural adhesive 644 extends partially within first set of composite plies 630. In some illustrative examples, structural adhesive 644 extends at least partially between second set of composite plies 632 and segmented set of composite plies 622. In some illustrative examples, structural adhesive 644 extends partially within second set of composite plies 632.

[0075] In some illustrative examples, segmented sets of composite plies 622 are bonded to flat surfaces of first metal structural component 612 and second metal structural component 614. In some illustrative examples, segmented sets of composite plies 622 are bonded to stepped surfaces of first metal structural component 612 and second metal structural component 614.

[0076] The illustration of manufacturing environment 600 in FIG. 6 is not meant to imply physical or architectural limitations to the manner in which an illustrative embodiment may be implemented. Other components in addition to or in place of the illustrated components may be used. Some components may be unnecessary. Also, the blocks are presented to illustrate some functional components. One or more of these blocks may be combined, divided, or combined and divided into different blocks when implemented in an illustrative embodiment.

[0077] For example, there may be more than two metal structural components. As another example, when there are more than two metal structural components, there may be more than two sets of split composite plies.

[0078] Attention is now directed to FIG. 7 , which illustrates a cross-sectional view of a metal-to-composite joint according to an illustrative embodiment. Metal-to-composite joint 700 is a physical implementation of metal-to-composite joint 610 of FIG. 6 . Metal-to-composite joint 700 may be a joint within a composite panel of plurality of composite panels 210 of FIG. 2 . In some illustrative examples, first metal structural component 706 and second metal structural component 708 are titanium structural components 258 of FIG. 2 . Metal-to-composite joint 700 may be a joint within a composite panel of plurality of composite panels 305 of FIG. 3 . Metal-to-composite joint 700 may be an alternative joint in a composite panel to those shown in FIGS. 4 and 5 . In some illustrative examples, metal-to-composite joint 700 may alternatively be present within composite panel 401 of FIG. 4 . In some illustrative examples, metal to composite joint 700 may alternatively be present in at least one of composite panel 502 and composite panel 504 in Figure 5 .

[0079] The metal to composite joint 700 comprises a metal structural component 702 and a composite material 704. The metal structural component 702 comprises a first metal structural component 706 and a second metal structural component 708.

[0080] Two metallic structural components, first metallic structural component 706 and second metallic structural component 708, form a portion of a first surface 716 and a portion of a second surface 718 of metal-to-composite joint 700. A segmented set of composite plies 710 is between the two metallic structural components and provides an escape path 711 for volatiles between the two metallic structural components. In this illustrative example, volatiles can escape metal-to-composite joint 700 by traveling between layers along segmented set of composite plies 710.

[0081] In this illustrative example, segmented-set of composite plies 710 is adhered to two metallic structural components, first metallic structural component 706 and second metallic structural component 708. In this illustrative example, segmented-set of composite plies 710 is bonded to a flat surface 722 of first metallic structural component 706 and a flat surface 726 of second metallic structural component 708. In this illustrative example, structural adhesive 728 adheres segmented-set of composite plies 710 to each of flat surfaces 722 and 726.

[0082] Sub-set of composite plies 710 may comprise any desired number of composite plies, hi some illustrative examples, sub-set of composite plies 710 may comprise a stackup of six composite plies.

[0083] The first metal structural component 706 comprises a stepped surface 720 and a flat surface 722. The second metal structural component 708 comprises a stepped surface 724 and a flat surface 726. The first set of composite plies 712 comprises a joining surface that is complementary to the first metal structural component 706 of the two metal structural components. The second set of composite plies 714 comprises a joining surface that is complementary to the second metal structural component 708 of the two metal structural components. The first set of composite plies 712 is complementary to the first metal structural component 706. The second set of composite plies 714 is complementary to the second metal structural component 708.

[0084] The first set of composite plies 712 includes a first ply stack 770, a second ply stack 772, a third ply stack 774, and a fourth ply stack 776. The second set of composite plies 714 includes a fifth ply stack 778, a sixth ply stack 740, a seventh ply stack 742, and an eighth ply stack 744.

[0085] In some illustrative examples, a manufacturable gap may exist between first set of composite plies 712 and stepped surface 720 of first metallic structural component 706. In some illustrative examples, a manufacturable gap may exist between second set of composite plies 714 and stepped surface 724 of second metallic structural component 708. Volatiles from the gap may be vented through escape path 711 during processing of metal-to-composite joint 700.

[0086] In this illustrative example, two metallic structural components, first metallic structural component 706 and second metallic structural component 708, are symmetrical about center 748 of metal-to-composite joint 700 in the direction of thickness 746. In this illustrative example, flat surface 722 faces flat surface 726, centered at center 748 of metal-to-composite joint 700 in the direction of thickness 746. In this illustrative example, the longest composite ply of first set of composite plies 712 forms a portion of first surface 716. In this illustrative example, the longest composite ply of second set of composite plies 714 forms a portion of second surface 718. In this illustrative example, the longest portions of stepped surface 720 and stepped surface 724 are near center 748, so the two metallic structural components appear to “extend into” the composite.

[0087] A split set of composite plies 710 extends between a first set of composite plies 712 and a second set of composite plies 714. The first set of composite plies 712 forms a lap joint with a stepped surface 720 of the first metal structural component 706. The second set of composite plies 714 forms a lap joint with a stepped surface 724 of the second metal structural component 708.

[0088] In this illustrative example, structural adhesive 728 covers the bonding surfaces of two metal structural components, first metal structural component 706 and second metal structural component 708, with first set of composite plies 712 and second set of composite plies 714. In this illustrative example, structural adhesive 728 bonds first set of composite plies 712 to first metal structural component 706. In this illustrative example, structural adhesive 728 bonds second set of composite plies 714 to second metal structural component 708. In this illustrative example, structural adhesive 728 extends partially between some ply stacks of first set of composite plies 712. As shown, structural adhesive 728 extends partially between third ply stack 774 and fourth ply stack 776. As shown, structural adhesive 728 extends partially between fourth ply stack 776 and split set of composite plies 710. As shown, the structural adhesive 728 extends partially between the split set of composite plies 710 and the fifth ply stack 778. As shown, the structural adhesive 728 extends partially between the fifth ply stack 778 and the sixth ply stack 740.

[0089] In some illustrative examples, the two metal structural components, first metal structural component 706 and second metal structural component 708, comprise titanium. In some illustrative examples, titanium is used based on its compressive strength.

[0090] In some illustrative examples, metal to composite joint 700 may be a component of an aircraft wing, hi some illustrative examples, metal to composite joint 700 may connect an aircraft wing to an aircraft fuselage.

[0091] As shown, the two metal structural components include a first metal structural component 706 having a stepped surface 720 and a flat surface 722, and a second metal structural component 708 having a stepped surface 724 and a flat surface 726. In this illustrative example, the flat surfaces of the first metal structural component 706 and the second metal structural component 708 are interior to the platform. In this illustrative example, the stepped surfaces of the first metal structural component 706 and the second metal structural component 708 form part of the surface of the platform.

[0092] Metal-to-composite joint 700 is a non-limiting example. In this illustrative example, metal-to-composite joint 700 is symmetrical about center 748 in the direction of thickness 746. In other illustrative examples, metal-to-composite joint 700 may be asymmetrical. While four metal structural components are shown, the metal-to-composite joint of the illustrative example may have any desired number of metal structural components. Furthermore, although metal structural components 702 each extend an equal distance into the composite, in other illustrative examples, at least one metal structural component may be of a different size, shape, or other configuration.

[0093] Attention is now directed to FIG. 8 , which illustrates a cross-sectional view of a metal-to-composite joint according to an illustrative embodiment. Metal-to-composite joint 800 is a physical implementation of metal-to-composite joint 610 of FIG. 6 . Metal-to-composite joint 800 may be a joint within a composite panel of plurality of composite panels 210 of FIG. 2 . In some illustrative examples, first metal structural component 806 and second metal structural component 808 are titanium structural components 258 of FIG. 2 . Metal-to-composite joint 800 may be a joint within a composite panel of plurality of composite panels 305 of FIG. 3 . Metal-to-composite joint 800 may be an alternative joint within a composite panel to those shown in FIGS. 4 and 5 . In some illustrative examples, metal-to-composite joint 800 may alternatively be present within composite panel 401 of FIG. 4 . In some illustrative examples, metal to composite joint 800 may alternatively be present in at least one of composite panel 502 and composite panel 504 in Figure 5 .

[0094] The metal to composite joint 800 comprises a metal structural component 802 and a composite material 804. The metal structural component 802 comprises a first metal structural component 806 and a second metal structural component 808.

[0095] Two metallic structural components, first metallic structural component 806 and second metallic structural component 808, form a portion of a first surface 816 and a portion of a second surface 818 of metal-to-composite joint 800. Segmented set of composite plies 810 are between the two metallic structural components and provide an escape path 811 for volatiles between the two metallic structural components. In this illustrative example, volatiles can escape metal-to-composite joint 800 by traveling between layers along segmented set of composite plies 810.

[0096] In this illustrative example, segmented-set of composite plies 810 is adhered to two metallic structural components, first metallic structural component 806 and second metallic structural component 808. In this illustrative example, segmented-set of composite plies 810 is bonded to stepped surface 820 of first metallic structural component 806 and stepped surface 824 of second metallic structural component 808. In this illustrative example, structural adhesive 828 adheres segmented-set of composite plies 810 to each of stepped surface 820 and stepped surface 824.

[0097] Sub-set of composite plies 810 comprises any desired number of composite plies, hi some illustrative examples, sub-set of composite plies 810 comprises a stackup of six composite plies.

[0098] First metal structural component 806 comprises a stepped surface 820 and a flat surface 822. Second metal structural component 808 comprises a stepped surface 824 and a flat surface 826. First set of composite plies 812 comprise a joining surface that is complementary to first metal structural component 806 of the two metal structural components. Second set of composite plies 814 comprise a joining surface that is complementary to second metal structural component 808 of the two metal structural components. First set of composite plies 812 are complementary to first metal structural component 806. Second set of composite plies 814 are complementary to second metal structural component 808.

[0099] First set of composite plies 812 includes a first ply stack 830, a second ply stack 832, a third ply stack 834, and a fourth ply stack 836. Each stack of plies in the first set of composite plies includes any desired number of plies. In some illustrative examples, each stack of plies includes six plies. Second set of composite plies 814 includes a fifth ply stack 838, a sixth ply stack 840, a seventh ply stack 842, and an eighth ply stack 844.

[0100] In some illustrative examples, a manufacturable gap may exist between first set of composite plies 812 and stepped surface 820 of first metallic structural component 806. In some illustrative examples, a manufacturable gap may exist between second set of composite plies 814 and stepped surface 824 of second metallic structural component 808. Volatiles from the gap may be vented through escape path 811 during processing of metal-to-composite joint 800.

[0101] In this illustrative example, two metallic structural components, first metallic structural component 806 and second metallic structural component 808, are symmetrical about a center 848 of metal-to-composite joint 800 in the thickness direction 846. In this illustrative example, flat surface 822 faces away from flat surface 826 about center 848 of metal-to-composite joint 800 in the thickness direction 846. In this illustrative example, stepped surface 820 faces toward stepped surface 824 about center 848 of metal-to-composite joint 800 in the thickness direction 846. In this illustrative example, flat surface 822 forms a portion of first surface 816. In this illustrative example, the shortest composite ply of first set of composite plies 812 forms a portion of first surface 816. In this illustrative example, the shortest composite ply of second set of composite plies 814 forms a portion of second surface 818. In this illustrative example, the longest portions of stepped surface 820 and stepped surface 824 are near center 848, so the two metal structural components appear to "extend into" the composite material.

[0102] A split set of composite plies 810 extends between a first set of composite plies 812 and a second set of composite plies 814. The first set of composite plies 812 forms a lap joint with a stepped surface 820 of the first metal structural component 806. The second set of composite plies 814 forms a lap joint with a stepped surface 824 of the second metal structural component 808.

[0103] In this illustrative example, structural adhesive 828 covers the bonding surfaces of two metal structural components, first metal structural component 806 and second metal structural component 808, with first set of composite plies 812 and second set of composite plies 814. In this illustrative example, structural adhesive 828 bonds first set of composite plies 812 to first metal structural component 806. In this illustrative example, structural adhesive 828 bonds second set of composite plies 814 to second metal structural component 808. As shown, structural adhesive 828 extends partially between fourth ply stack 836 and segmented set of composite plies 810. As shown, structural adhesive 828 extends partially between segmented set of composite plies 810 and fifth ply stack 838.

[0104] In some illustrative examples, the two metal structural components, first metal structural component 806 and second metal structural component 808, comprise titanium.

[0105] In some illustrative examples, metal-to-composite joint 800 may be a component of an aircraft wing, hi some illustrative examples, metal-to-composite joint 800 may connect an aircraft wing to an aircraft fuselage.

[0106] As shown, the two metal structural components include a first metal structural component 806 having a stepped surface 820 and a flat surface 822, and a second metal structural component 808 having a stepped surface 824 and a flat surface 826. In this illustrative example, the flat surfaces of first metal structural component 806 and second metal structural component 808 are interior to the platform. In this illustrative example, the stepped surfaces of first metal structural component 806 and second metal structural component 808 form part of the surface of the platform.

[0107] Metal-to-composite joint 800 is a non-limiting example. In this illustrative example, metal-to-composite joint 800 is symmetrical about center 848 in the direction of thickness 846. In other illustrative examples, metal-to-composite joint 800 may be asymmetrical. While four metal structural components are shown, the metal-to-composite joint of the illustrative example may have any desired number of metal structural components. Furthermore, although metal structural components 802 each extend an equal distance into the composite, in other illustrative examples, at least one metal structural component may be of a different size, shape, or other configuration.

[0108] Attention is now directed to FIG. 9 , which illustrates a cross-sectional view of a metal-to-composite joint according to an illustrative embodiment. Metal-to-composite joint 900 is a physical implementation of metal-to-composite joint 610 of FIG. 6 . Metal-to-composite joint 900 may be a joint within a composite panel of plurality of composite panels 210 of FIG. 2 . In some illustrative examples, first metal structural component 904 and second metal structural component 906 are titanium structural component 258 of FIG. 2 . Metal-to-composite joint 900 may be a joint within a composite panel of plurality of composite panels 305 of FIG. 3 . Metal-to-composite joint 900 may be an alternative joint within a composite panel to those shown in FIGS. 4 and 5 . In some illustrative examples, metal-to-composite joint 900 may alternatively be present within composite panel 401 of FIG. 4 . In some illustrative examples, metal to composite joint 900 may alternatively be present in at least one of composite panel 502 and composite panel 504 in Figure 5 .

[0109] Metal-to-composite joint 900 comprises metal structural components 902 separated by sets of segmented composite plies. Metal structural components 902 comprise a first metal structural component 904, a second metal structural component 906, a third metal structural component 908, and a fourth metal structural component 910. In this illustrative example, the sets of segmented composite plies comprise segmented set of composite plies 912, segmented set of composite plies 914, and segmented set of composite plies 916.

[0110] In this illustrative example, metal-to-composite joint 900 further comprises a first set of composite plies 918, a second set of composite plies 920, a third set of composite plies 922, and a fourth set of composite plies 924. In this illustrative example, metal-to-composite joint 900 comprises a first surface 926 and a second surface 928. Moving across thickness 930 from first surface 926 to second surface 928 of metal-to-composite joint 900, each of metal structural component 902, first set of composite plies 918, segmented set of composite plies 912, second set of composite plies 920, segmented set of composite plies 914, third set of composite plies 922, segmented set of composite plies 916, and fourth set of composite plies 924.

[0111] In this illustrative example, each of the sets of segmented composite plies provides an escape path for volatiles from metal-to-composite joint 900. Segmented set of composite plies 912 provides escape path 932 for volatile migration. Segmented set of composite plies 914 provides escape path 934 for volatile migration. Segmented set of composite plies 916 provides escape path 936 for volatile migration.

[0112] By migrating along escape paths 932, 934, or 936, volatiles migrate between layers through structure 938 having metal-to-composite joint 900. By providing composite ply segment set 912, composite ply segment set 914, and composite ply segment set 916, structure 938 has improved venting capabilities. Metal-to-composite joint 900 having composite ply segment set 912, composite ply segment set 914, and composite ply segment set 916 has lower porosity than a structure having a single titanium component extending through thickness 930 without split composite plies. Metal-to-composite joint 900 having composite ply segment set 912, composite ply segment set 914, and composite ply segment set 916 does not need to be repeatedly heated for venting, which can result in less manufacturing time. Metal-to-composite joint 900 having split composite ply set 912, split composite ply set 914, and split composite ply set 916 may have improved quality due to the presence of the split composite ply sets.

[0113] Metal-to-composite joint 900 is a non-limiting example. In this illustrative example, metal-to-composite joint 900 is symmetrical about the center of metal-to-composite joint 900 in the direction of thickness 930. In other illustrative examples, metal-to-composite joint 900 may be asymmetrical. While four metal structural components are shown, the metal-to-composite joint of the illustrative example may have any desired number of metal structural components. Furthermore, although metal structural components 902 each extend an equal distance into the composite, in other illustrative examples, at least one metal structural component may be of a different size, shape, or other configuration.

[0114] Attention is now directed to FIG. 10 , which depicts a flowchart of a method for forming a composite structure, in accordance with an illustrative embodiment. Method 1000 may be used to form composite structure 202 of FIG. 2 . Method 1000 may be used to form wing 318 of FIG. 3 . Composite panel 401 of FIG. 4 may be formed in method 1000. Joint 501 of FIG. 5 may be formed in method 1000. Metal-to-composite joint 610 of FIG. 6 may be formed in method 1000. Metal-to-composite joint 700 of FIG. 7 may be formed in method 1000. Metal-to-composite joint 800 of FIG. 8 may be formed in method 1000. Metal-to-composite joint 900 of FIG. 9 may be formed in method 1000.

[0115] The method 1000 bonds the composite skins to respective first titanium ends and respective second titanium ends to form a plurality of composite panels (operation 1002). The method 1000 fastens the plurality of composite panels to structural supports to form a structural skin of the composite structure (operation 1004). Thereafter, the method 1000 ends.

[0116] In some illustrative examples, fastening the plurality of composite panels to the structural support includes routing fasteners through the first titanium end and the second titanium end and into the structural support (Operation 1006). In some illustrative examples, fastening the plurality of composite panels to the structural support includes routing fasteners through the first titanium end and the second titanium end and into the titanium splice plate and the structural support (Operation 1008).

[0117] Turning now to FIG. 11 , a flowchart of a method for accessing an interior volume of a composite structure is depicted, in accordance with an illustrative embodiment. Method 1100 may be used to access interior volume 268 of composite structure 202 of FIG. 2 . Method 1100 may be used to access interior volume of wing 318 of FIG. 3 . In method 1100, composite panel 401 of FIG. 4 may be removed to access the interior volume. Fastener 510 or fastener 512 of FIG. 5 may be loosened or removed in method 1100. Metal-to-composite joint 610 of FIG. 6 may be made part of a composite panel in method 1100. Metal-to-composite joint 700 of FIG. 7 may be made part of a composite panel in method 1100. Metal-to-composite joint 800 of FIG. 8 may be made part of a composite panel in method 1100. Metal-to-composite joint 900 of FIG. 9 may be made part of a composite panel in method 1100.

[0118] In method 1100, one-sided fasteners of a composite panel are loosened, resulting in a composite panel comprising a first titanium end, a second titanium end, and a composite skin joined to the first titanium end and the second titanium end and extending between the first titanium end and the second titanium end (operation 1102). After the one-sided fasteners are released, method 1100 removes the composite panel from the composite structure to create an opening (operation 1104). Method 1100 accesses an interior volume of the composite structure through the opening (operation 1106). Method 1100 then ends.

[0119] In some illustrative examples, the composite panel may be referred to as an access panel, and removal of the composite panel provides access to an interior volume without a dedicated access hole.

[0120] In some illustrative examples, the composite structure includes a panelized structural skin. In some illustrative examples, the panelized structural skin comprises a plurality of composite panels.

[0121] In some illustrative examples, method 1100 fastens a plurality of composite panels to a structural support of a composite structure to form a structural skin of the composite structure, the plurality of composite panels comprising a composite panel (operation 1108). The plurality of composite panels can provide a plurality of points for accessing an interior volume of the composite structure.

[0122] In some illustrative examples, unfastening the single-sided fasteners includes unfastening the single-sided fasteners extending through the first titanium end and the second titanium end (operation 1110). In some illustrative examples, unfastening the single-sided fasteners includes removing the single-sided fasteners from the composite panel and the structural support of the composite structure (operation 1112). In some illustrative examples, the single-sided fasteners can be reused to reinstall the composite panel.

[0123] In some illustrative examples, method 1100 further includes reinstalling the composite panel with single-sided fasteners to close the opening (operation 1114). In some illustrative examples, the composite panel is reinstalled with new single-sided fasteners.

[0124] As used herein, the phrase "at least one of," when used in conjunction with a list of items, means that various combinations of one or more of the listed items may be used, and that only one of each item in the list may be required. For example, "at least one of item A, item B, and item C" may include, but is not limited to, item A, item A and item B, or item B. This example may also include item A, item B, and item C, or item B and item C. Of course, any combination of these items may be present. In other examples, "at least one of" may be, for example, but is not limited to, two item A, one item B, and ten items C, four items B, and seven items C, or any other suitable combination. An item may be a specific object, thing, or category. In other words, at least one of means that any combination of items and some items may be used from the list, but not all of the items in the list are required.

[0125] As used herein, "some," when used in reference to an item, means one or more of the item.

[0126] The flowcharts and block diagrams in the various depicted embodiments illustrate the architecture, functionality, and operation of some possible implementations of apparatuses and methods in the illustrative embodiments. In this regard, each block in the flowcharts or block diagrams may represent a module, a segment, a function, and / or a portion of an operation or step.

[0127] In some alternative implementations of the illustrative embodiments, one or more functions noted in a block may occur out of the order noted in the figures. For example, in some cases, two blocks shown in succession may be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending on the functionality involved. Also, other blocks may be added in addition to the illustrated blocks in a flowchart or block diagram. Some blocks may be optional. For example, act 1006 through act 1008 may be optional.

[0128] An exemplary embodiment of the present disclosure may be described with reference to aircraft manufacturing and service method 1200 as shown in Figure 12 and aircraft 1300 as shown in Figure 13. Turning initially to Figure 12, an illustration of an aircraft manufacturing and service method in block diagram form is shown in accordance with an exemplary embodiment. During pre-production, aircraft manufacturing and service method 1200 may include specification and design 1202 and material procurement 1204 of aircraft 1300 in Figure 13.

[0129] During production, component and subassembly manufacturing 1206 and system integration 1208 of the aircraft 1300 occurs. The aircraft 1300 may then undergo certification and delivery 1210 for placement in service 1212. While in service 1212 by a customer, the aircraft 1300 is scheduled for routine maintenance and service 1214, which may include modification, reconfiguration, refurbishment, or other maintenance and service.

[0130] Each of the processes of aircraft manufacturing and service method 1200 may be performed or implemented by a system integrator, a third party, and / or an operator. In these examples, the operator may be a customer. For purposes of this description, a system integrator may include, but is not limited to, any number of aircraft manufacturers and major system subcontractors; a third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers; an operator may be an airline, a leasing company, the military, a service organization, etc.

[0131] Referring now to Figure 13, an illustration of an aircraft in block diagram form is shown in which an illustrative embodiment may be implemented. In this example, aircraft 1300 is produced by aircraft manufacturing and service method 1200 in Figure 12 and may include airframe 1302 having multiple systems 1304 and interior 1306. Example systems 1304 include one or more of propulsion system 1308, electrical system 1310, hydraulic system 1312, and environmental system 1314. Any number of other systems may also be included.

[0132] Apparatus and methods embodied herein may be employed during at least one of the stages of aircraft manufacturing and service method 1200. One or more illustrative embodiments may be manufactured or used during at least one of component and subassembly manufacturing 1206, system integration 1208, in-service 1212, and maintenance and service 1214 in Figure 12.

[0133] The illustrative examples allow for the design and fabrication of large-scale composite wing skins with titanium splices on both ends. The illustrative examples allow for the design and fabrication of large-scale composite wing skins with titanium splices on both ends (inboard end and outboard end). The illustrative examples can reduce weight. The illustrative example composite panels can allow for multi-piece wing boxes. The illustrative example composite panels can allow for panelization of wing skins.

[0134] The illustrative examples provide a method for panelizing the wing and using fasteners to the substructure (spars / ribs) via spliced ​​joints, doublers. The illustrative examples allow access to the interior of the wing without an access door. The panelization in the illustrative examples can allow for fewer skin access holes or even elimination of holes. The illustrative examples provide for two or more panels spliced ​​together chordwise.

[0135] Wing panelization allows for the construction of thinner wings than would be possible using conventional designs. Panelized wings allow access by removing wing skin panels instead of through-holes. A smaller profile wing can provide improved performance.

[0136] The composite panels are connected to a metal substructure, which in some illustrative examples may be aluminum and include titanium splice plates.

[0137] The illustrative example handles structural loads. The use of titanium edges allows for a reduction in panel gauge, particularly at the nacelle attachment points, landing gear attachment points, and outboard ends. Traditional composite joints increase the thickness / gauge of the joints, which increases weight. The use of titanium edges allows the illustrative example composite panels to be thinner with comparable strength to traditional composite joints. The illustrative example composite panels reduce weight and present a more efficient design. Weight and efficiency improvements were visible at the nacelle pads, landing gear, and outboard ends.

[0138] The description of various exemplary embodiments has been presented for purposes of illustration and description and is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those skilled in the art. Furthermore, different exemplary embodiments may provide different configurations compared to other exemplary embodiments. The selected embodiment or embodiments have been chosen and described in order to best explain the principles, practical applications of the embodiments, and to enable others skilled in the art to understand the disclosure of the various embodiments with various modifications suitable for the particular use contemplated. [Explanation of symbols]

[0139] 100 aircraft, 102 wing, 104 wing, 106 fuselage, 108 engine, 110 engine, 112 tail section, 114 horizontal stabilizer, 116 horizontal stabilizer, 118 vertical stabilizer, 200 manufacturing environment, 202 composite structure, 204 aircraft, 206 wing, 208 wing skin, 210 multiple composite panels, 212 composite panel, 214 first titanium edge, 216 second titanium edge, 218 composite skin, 220 stepped lap joint, 222 stepped lap joint, 224 composite panel, 226 first titanium edge, 228 second titanium edge, 230 composite skin, 232 stepped lap joint, 234 stepped lap joint, 236 composite panel, 238 first titanium edge, 240 second titanium end, 241 length, 242 composite skin, 244 stepped lap joint, 248 titanium splice plate, 250 titanium splice plate, 252 multiple access panels, 253 structural support, 254 structural support, 256 structural support, 258 titanium structural component, 259 split set of composite plies, 260 escape route, 262 volatile material, 264 fasteners, 266 structural skin, 268 interior volume, 270 single-sided fasteners, 272 opening, 300 view, 302 inboard end, 304 outboard end, 305 multiple composite panels, 306 structural skin, 308 composite panel, 310 composite panel, 312 composite panel, 314 joint, 316 joint, 318 wing, 320 composite structure, 400 view, 401 Composite panel, 402, composite skin, 404, titanium edge, 406, first titanium edge, 408, second titanium edge, 410, first stepped lap joint, 412, second stepped lap joint, 500, view, 501, joint, 502, composite panel, 504, composite panel, 506, structural support, 508, titanium splice plate, 510, fastener, 512, fastener, 516, titanium edge, 520, titanium edge, 600, manufacturing environment, 602, platform, 604, aircraft, 606, wing, 608, fuselage, 610, metal-to-composite joint, 612, first metallic structural component, 613, titanium, 614, second metallic structural component, 615, titanium, 616, stepped surface, 618, flat surface, 620, flat surface, 622, split set of composite plies, 623 Volatile substances, 624 Escape routes, 626First surface 628 Second surface 630 First set of composite plies 632 Second set of composite plies 634 First ply stack 635 Length 636 Second ply stack 637 Length 638 Third ply stack 639 Length 640 Fourth ply stack 642 Lap joint 643 Lap joint 644 Structural adhesive 646 Thickness 648 Bonding surface 650 Bonding surface 661 Stepped surface 700 Metal to composite joint 702 Metal structural component 704 Composite material 706 First metal structural component 708 Second metal structural component 710 Split set of composite plies 711 Escape path 712 First set of composite plies 714 Second set of composite plies 716 First surface 718 Second surface 720 Stepped surface 722 Flat surface, 724 Stepped surface, 726 Flat surface, 728 Structural adhesive, 740 Sixth ply stack, 742 Seventh ply stack, 744 Eighth ply stack, 746 Thickness, 748 Center, 770 First ply stack, 772 Second ply stack, 774 Third ply stack, 776 Fourth ply stack, 778 Fifth ply stack, 800 Metal to composite joint, 802 Metal structural component, 804 Composite material, 806 First metal structural component, 808 Second metal structural component, 810 Split set of composite plies, 811 Escape path, 812 First set of composite plies, 814 Second set of composite plies, 816 First surface, 818 Second surface, 820 Stepped surface, 822 Flat surface, 824 Stepped surface, 826 Flat surface, 828 Structural adhesive, 830; First ply stack, 832; Second ply stack, 834; Third ply stack, 836; Fourth ply stack, 838; Fifth ply stack, 840; Sixth ply stack, 842; Seventh ply stack, 844; Eighth ply stack, 846; Thickness, 848; Center, 900; Metal-to-composite joint, 902; Metal structural component, 904; First metal structural component, 906; Second metal structural component, 908; Third metal structural component, 910; Fourth metal structural component, 912; Composite ply split set, 914; Composite ply split set, 916; Composite ply split set, 918First set of composite plies, 920 Second set of composite plies, 922 Third set of composite plies, 924 Fourth set of composite plies, 926 First surface, 928 Second surface, 930 Thickness, 932 Escape route, 934 Escape route, 936 Escape route, 938 Structure, 1000 Method, 1002 Operation, 1004 Operation, 1006 Operation, 1008 Operation, 1100 Method, 1102 Operation, 1104 Operation, 1106 Operation, 1108 Operation, 1110 Operation, 1112 Operation, 1114 Operation, 1200 Aircraft manufacturing and maintenance methods, 1202 Specification and design, 1204 Material procurement, 1206 Component and subassembly manufacturing, 1208 System integration, 1210 Certification and delivery, 1212 In-service, 1214 Maintenance and Inspection, 1300 Aircraft, 1302 Airframe, 1304 Multiple Systems, 1306 Interior, 1308 Propulsion Systems, 1310 Electrical Systems, 1312 Hydraulic Systems, 1314 Environmental Systems

Claims

1. a structural support (253); a structural skin (266) comprising a composite panel (212, 224, 236) comprising a first titanium end (214, 226, 238, 406), a second titanium end (216, 228, 240, 408), and a composite skin (218, 230, 242, 402) joined to said first titanium end (214, 226, 238, 406) and said second titanium end (216, 228, 240, 408) and extending between said first titanium end (214, 226, 238, 406) and said second titanium end (216, 228, 240, 408); A composite structure (202) comprising:

2. The composite structure (202) of claim 1, wherein the structural skin (266) comprises a wing skin (208) of an aircraft (204).

3. 2. The composite structure of claim 1, wherein the composite panel further comprises a first stepped lap joint between the first titanium end and the composite skin, and a second stepped lap joint between the second titanium end and the composite skin.

4. The composite structure (202) of claim 1, further comprising a titanium splice plate (248, 250) between the structural support (253) and the composite panel (212, 224, 236).

5. The composite structure (202) of claim 4, wherein the composite panels (212, 224, 236) are removably fastened to titanium splices (248, 250).

6. 2. The composite structure (202) of claim 1, further comprising fasteners (264, 510, 512) extending through the first titanium end (214, 226, 238, 406) and the second titanium end (216, 228, 240, 408) of the composite panel (212, 224, 236) to connect the composite panel (212, 224, 236) to the structural support (253).

7. The composite structure (202) of claim 1, wherein the composite panels (212, 224, 236) are bonded to the structural supports (253).

8. The composite structure (202) of claim 1, wherein the composite panels (212, 224, 236) are access panels (252) removably connected to provide interior access to the composite structure (202).

9. 2. The composite structure of claim 1, wherein the composite panel comprises two or more titanium structural components forming one of the first titanium end and the second titanium end.

10. 10. The composite structure (202) of claim 8, wherein a split set of composite plies (259, 622) extends between two or more of said titanium structural components (258, 612, 614) to provide an escape path (260, 624) for volatile materials (262, 623).

11. A composite structure (202) comprising: Composite panels (212, 224, 236) fastened to the composite structure at titanium ends, the composite panels (212, 224, 236) comprising: two titanium ends (220, 222, 226, 228, 238, 240); a composite skin (218, 230, 242, 402) joined to the two titanium ends (220, 222, 226, 228, 238, 240) and extending between the two titanium ends (220, 222, 226, 228, 238, 240); A composite structure (202) comprising:

12. 11. The composite structure (202) of claim 10, wherein each of the composite panels (212, 224, 236) further comprises a first stepped lap joint (220, 232, 244) between a first titanium end (214, 226, 238, 406) and the composite skin (218, 230, 242, 402) and a second stepped lap joint (222, 234, 246) between a second titanium end (216, 228, 240, 408) and the composite skin (218, 230, 242, 402).

13. 12. The composite structure (202) of claim 11, wherein the composite panel is one of a plurality of composite panels (210, 305), the plurality of composite panels (210, 305) comprising a wing skin (208) of an aircraft (204).

14. the composite panel is one of a plurality of composite panels (210, 305); The composite structure (202) of claim 11, further comprising a titanium splice plate (248, 250) joining a plurality of said composite panels (210, 305).

15. 15. The composite structure (202) of claim 14, wherein each composite panel (212, 224, 236) of the plurality of composite panels (210, 305) is removably fastened to one of the titanium splice plates (248, 250).

16. The composite structure (202) of claim 11, wherein the composite panel is an access panel (252) removably connected to provide interior access to the composite structure (202).

17. The composite structure (202) of claim 11, wherein the composite panel comprises two or more titanium structural components (258, 612, 614) forming a titanium end (240).

18. 20. The composite structure (202) of claim 17, wherein a segmented set of composite plies (259, 622) extends between two or more of said titanium structural components (258, 612, 614) to provide an escape path (260, 624) for volatile materials (262, 623).

19. A method of forming a composite structure (202), comprising: bonding composite skins (218, 230, 242, 402) to respective first titanium ends (214, 226, 238, 406) and respective second titanium ends (216, 228, 240, 408) to form a plurality of composite panels (210, 305); fastening a plurality of said composite panels (210, 305) to structural supports (253) to form a structural skin (266) of said composite structure (202); A method comprising:

20. 20. The method of claim 19, wherein the step of fastening the plurality of composite panels to the structural support comprises routing fasteners through the first titanium end and the second titanium end into the structural support.

21. 20. The method of claim 19, wherein the step of fastening the plurality of composite panels to the structural support includes routing fasteners through the first titanium end and the second titanium end into a titanium splice plate and the structural support.

22. 1. A method (1100) for accessing an interior volume of a composite structure, comprising: a step (1102) of unfastening one-sided fasteners (270, 510) of a composite panel (212, 224, or 236), the composite panel (212, 224, or 236) comprising a first titanium end (214, 226, 238, 406), a second titanium end (216, 228, 240, 408), and a composite skin (218, 230, 242, 402) joined to the first titanium end (214, 226, 238, 406) and the second titanium end (216, 228, 240, 408) and extending between the first titanium end (214, 226, 238, 406) and the second titanium end (216, 228, 240, 408); removing (1104) the composite panel (212, 224, or 236) from the composite structure (202) to create an opening (272) after unfastening the one-sided fasteners (270, 510); accessing (1106) the interior volume (268) of the composite structure through the opening (272); A method (1100) comprising:

23. 23. The method (1100) of claim 22, further comprising reinstalling (1114) the composite panel (212, 224, or 236) with single-sided fasteners (270) to close the opening (272).

24. 23. The method (1100) of claim 22, wherein unfastening (1110) the one-sided fastener (270) comprises unfastening a one-sided fastener (270) extending through the first titanium end (214, 226, 238, 406) and the second titanium end (216, 228, 240, 408).

25. 23. The method (1100) of claim 22, further comprising fastening (1108) a plurality of composite panels to structural supports of the composite structure to form a structural skin (266) of the composite structure (202), wherein a plurality of the composite panels (210, 305) comprise the composite panels.

26. 23. The method (1100) of claim 22, wherein unfastening (1112) the one-sided fasteners (270) comprises removing the one-sided fasteners (270) from the composite panels and structural supports (253, 506) of the composite structure (202).

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