Enhanced structure of superplastic forming and diffusion bonding

Abstract

The name of the present invention is an enhanced superplastic forming and diffusion bonding structure. An outer panel is formed from a superplastic material, which includes an outer skin of titanium to accommodate the high thermal stresses imposed on a hypersonic transport vehicle during hypersonic flight. The outer skin is secured to a underlying enhanced framework structure, which consists of a superplastic formable reinforcement (SFR) layer, such as a titanium, zirconium, and molybdenum (TZM) alloy, which supports the outer skin when the outer skin is heated to a temperature in excess of 1200 degrees Fahrenheit. The outer panel includes a separate inner skin, which is configured for attachment to framework members, such as ribs, stringers, or spars of a hypersonic transport vehicle. A multi-cell core is sandwiched between the outer skin and the inner skin to impart tensile and compressive strength to the outer panel. In one disclosed method, the core is superplastic formed and diffusion bonded to the outer skin and the inner skin.

Description

Technical Field

[0001] The present disclosure relates to superplastic forming and diffusion bonding (SPF / DB) sandwich structures for aerospace applications. Background Art

[0002] The thermal loads imposed on the outer surfaces of high-speed aerospace vehicles pose significant and ongoing requirements for improved thermal management strategies.

[0003] External structures formed from titanium alloys are known to be effective in accommodating the high heat flux environments at supersonic speeds. However, for hypersonic speeds, additional thermal compensation mechanisms are sought. Tiles have been used on spacecraft, particularly for managing the thermal loads upon re-entry into the atmosphere from space. Nickel alloys have also been used in some structures. However, in terms of their respective structural configurations and fuel requirements, traditional nickel alloy usage has proven to be heavier and more expensive. The thermal protection previously used for hypersonic vehicles is not reusable, which limits its usefulness in commercial applications.

[0004] Accordingly, there is a need for less expensive structures that can effectively accommodate the temperatures at hypersonic speeds. Summary of the Invention

[0005] In accordance with one aspect of the present disclosure, an outer panel for a vehicle includes an outer skin configured for atmospheric exposure and an inner skin configured for attachment to a structural frame member of the vehicle. A multicellular core is sandwiched between the outer skin and the inner skin, and a superplastic forming reinforced (SFR) layer is located beneath the outer skin and supports the outer skin. The multicellular core is superplastic formed and diffusion bonded to the outer skin and the inner skin.

[0006] In accordance with another aspect of the present disclosure, a vehicle includes at least one outer panel having an outer skin configured for atmospheric exposure. The outer panel includes an inner skin configured for attachment to a structural frame member of the vehicle. A multicellular core is sandwiched between the outer skin and the inner skin to impart tensile and compressive strength to the outer panel, and an SFR layer is located beneath the outer skin. The multicellular core is superplastic formed and diffusion bonded to the outer skin and the inner skin.

[0007] According to another aspect of the present disclosure, a method of manufacturing an outer panel for a transportation vehicle includes providing an outer skin of a superplastic material configured for atmospheric exposure and providing an SFR layer located beneath the outer skin and supporting the outer skin. The method further includes providing an inner skin of a superplastic material configured to be attached to a structural frame member of the transportation vehicle, and providing at least a pair of sheet layers of a superplastic material to form a multi-unit core between the outer skin and the inner skin. Next, the sheet layers are joined together by intermittent seam welding arranged in a predetermined pattern. An expansion tube is fixed to one edge of the layer, and a continuous fusion weld is applied around the edge of the sheet layers. Then, the outer skin and the inner skin together with the sheet layers are installed in a pressure containment device, and an inert gas is supplied to the expansion tube to superplastic form and diffusion bond (SPF / DB) the skins and the layers to form a multi-unit core that is integrally bonded to the outer skin and the inner skin. In the complete SPF / DB structure, the SFR layer is located beneath the outer skin and reinforces the outer skin.

[0008] The features, functions, and advantages disclosed herein can be achieved in the examples presented herein, or can be provided by other variations, the details of which can be better understood with reference to the following description and the drawings. Brief Description of the Drawings

[0009] Figure 1 is a perspective view of an example of an outer panel constructed in accordance with the present disclosure for use as an aerodynamic exposure surface of a hypersonic transportation vehicle.

[0010] Figure 2 is a type of hypersonic transportation vehicle that can employ Figure 1 the outer panel.

[0011] Figure 2A is Figure 2 an enlarged view of an illustrated portion of

[0012] Figure 3 is Figure 1 a perspective exploded view of the components of the outer panel as they would appear during an initial manufacturing step, which includes an outer skin and an inner skin, with upper and lower core sheets sandwiched between the skins, and depicts an SFR layer located beneath the outer skin and supporting the outer skin.

[0013] Figure 4 is a side cross-sectional view of a forming fixture containing Figure 3 the components during the manufacture of the outer panel.

[0014] Figure 5 is a schematic perspective view of how the core sheet may behave during its expansion during the manufacture of the outer panel.

[0015] Figure 6 is a perspective view of the outer panel including the SFR layer just after manufacture, which shows the multi - cell core formed by the upper and lower core sheets that have fully expanded between the outer skin and the inner skin.

[0016] Figure 7 depicts a forming press for the Figure 4 fixture to accommodate the superplastic forming and diffusion bonding processes to manufacture the outer panel of the present disclosure.

[0017] Figure 8 is a perspective view of another example of an SFR layer having a different geometric pattern from the Figure 1 SFR layer.

[0018] Figure 9 shows a sequence of method steps for manufacturing an Figure 1 exemplary outer panel.

[0019] The reference drawings are not necessarily to scale, and any disclosed examples are shown schematically. Aspects of the disclosed examples may be combined with or substituted for one another and may be within various systems and environments not shown or described herein. Accordingly, the following detailed description is merely exemplary and is not intended to be restrictive in application or use. Detailed Description

[0020] The following detailed description includes apparatuses and methods for carrying out the present disclosure. The actual scope of the present disclosure is as defined in the appended claims.

[0021] Figure 1Shows an example of an outer panel 10 of a reusable outer surface that can be used as a hypersonic transport vehicle. The outer panel 10 includes an outer skin 12, an inner skin 14, and a multi-cell core 16, all of which can be formed of a titanium alloy. Located between the multi-cell core 16 and the outer skin 12, a superplastic formable reinforced (SFR) layer 18 is secured to the outer skin 12. The SFR layer 18 can be formed of a dissimilar alloy such as a titanium-zirconium-molybdenum (TZM) alloy. The latter can consist of, for example, at least 99% molybdenum, 0.5% titanium, and 0.08% zirconium. In the disclosed example, the SFR layer 18 is designed to reinforce the outer skin 12 whenever and if the atmospheric friction temperature of the outer skin 12 exceeds the functional limit of titanium, i.e., when the temperature of the outer skin exceeds a predetermined threshold. In the first disclosed example, the SFR layer 18 includes a rectilinear framework structure that is at least located under the edges and inner portions of the shown outer skin 12. When exposed to temperatures in excess of 1200°F, the outer skin 12 may begin to lose strength. Since the exposed outer skin 12 is subjected to the greatest amount of heat flux generated by hypersonic travel through the atmosphere, the SFR layer 18, which acts as a ridge or framework support structure, is configured to reinforce, i.e., support, the outer skin when the temperature on the outer skin may exceed the material strength limit of titanium. When using TZM material, it is particularly desirable to place the SFR layer 18 under the outer skin 12 because, if TZM is directly exposed to the atmosphere, the TZM, as a metal alloy, may experience significant oxidation.

[0022] Although the SFR layer 18 can use TZM material as described in the first disclosed embodiment, other materials that exhibit high strength and tensile properties at elevated temperatures can be used instead of the described SFR layer 18 to reinforce the outer skin 12. For example, although heavier, Incoloy 909, which consists of an iron-nickel-cobalt alloy, can be used instead. The iron-nickel-cobalt alloy has a composition of 42% iron, 38% nickel, 13% cobalt, and 4.7% niobium.

[0023] The described TZM and Incoloy materials are generally referred to herein as superplastic formable reinforced (SFR) materials because of their respective combinations of high strength, ductility, and tensile properties at elevated temperatures that exceed the functional capabilities of titanium.

[0024] Now also referring Figure 2 , an exemplary passenger hypersonic transport vehicle 20 includes structural frame members that include a pair of wings 22 that support the transport vehicle 20 in flight. The transport vehicle 20 includes a fuselage 24, a nose 26, and a thrust nozzle 28 for an engine (not shown) to accommodate travel at speeds of 3 to 5 Mach at altitudes in the stratosphere, i.e., at least 100,000 feet. Figure 2A ShowsFigure 2 The illustrated portion depicts an arrangement of a plurality of outer panels 10 that cover and include at least a portion of the wing 22. In the latter, an exemplary orientation of the otherwise hidden skeleton SFR layer 18 can be as Figure 2A shown. In this case, the inner skin 14 of the outer panel 10 can be fusion welded or otherwise fixed to the structural frame members of the transport vehicle 20, i.e., the wing 22. Additionally, each outer panel 10 can be fusion welded to one or more adjacent outer panels 10.

[0025] Figure 3 depicts the above-described assembly of the outer panel 10 prior to forming the multi-cell core 16, which includes an outer skin 12, an SFR layer 18 (e.g., consisting of one of the aforementioned TZM or Incoloy 909 materials), and an inner skin 14. As Figure 1 disclosed in the example, the core 16 of the outer panel 10 consists of a pair of upper and lower core sheets 30, 32 ( Figure 3 ), which are composed of a superplastic material such as a titanium alloy. The formation of the core 16 occurs during the process of superplastic forming and diffusion bonding (SPF / DB) of the core sheets 30, 32 to the outer skin 12, the SFR layer 18, and the inner skin 14 in a forming press as described below, to ensure the permanent integration of the core 16 with the outer and inner skins 12, 14. For this purpose, the upper and lower core sheets 30, 32 are initially fusion welded together along first and second arrays 34, 36 of intermittent seam welds. Intermittent seam welding is essentially spot welding, which creates small vent holes for balancing air pressure during the SPF / DB manufacturing process. The first array 34 and the second array 36 are orthogonally oriented relative to each other in a predetermined pattern such that applying air pressure between the core sheets 30, 32 will result in a multi-cell core defined by a uniformly arranged single cell, as further detailed below.

[0026] Titanium is a material that is both superplastic and suitable for diffusion bonding. Thus, the term "SPF / DB" as applied herein refers to a manufacturing process in which solid-state bonding of metal surfaces occurs while applying heat and pressure for a duration sufficient to create atomic blending at the bonding interface of the joined components. Thus, the SPF / DB process involves a diffusion process during superplastic expansion, but it is not sufficient to physically melt the joined surfaces. In contrast, fusion bonding or fusion welding as applied herein refers to metallurgical bonding of metal surfaces by applying sufficient heat to physically melt the materials at their bonding interface, i.e., reaching a liquid or plastic state when joined together.

[0027] Now referring to Figure 4 shown, a fixing device 40 can be used to accommodate during the manufacture of the outer panel 10 Figure 3The components. The fixing device 40 is defined by an upper frame member 42 and a lower frame member 44, which are used to support the respective outer skin and inner skin 12, 14. The upper and lower spacers 46, 48 are used as standoff supports to ensure a predetermined desired spacing between the outer skin 12 and the inner skin 14 reinforced by the SFR layer 18, while the core sheets 30, 32 are transformed into the multi-cell core 16 of the outer panel 10 during the high-pressure, high-temperature SPF / DB manufacturing process. Although the use of the standoff supports 46, 48 is shown in the disclosed fixing device 40, it is also feasible to manufacture without such standoff supports.

[0028] Now referring to Figure 5 , a perspective cross-sectional view of the upper and lower core sheets 30, 32 shows the expansion of the core sheets during the manufacturing process after the expansion tube 50 has been fixed to one edge by fusion welding. The peripheries of the core sheets 30, 32 are joined together, and an inert gas G is supplied to the expansion tube 50 at high pressure. Now referring to Figure 6 , the pressure of the gas G on the first and second arrays 34, 36 of intermittent seam welding produces the protruding portions 52 of the lower core sheet 32 and the corresponding protruding portions 54 of the upper core sheet 30, and finally transforms the core sheets into the fully formed unit structure 52' ( Figure 6 ) of the multi-cell core 16 ( Figure 6 ). In addition, it should be understood that the visible contour lines or dividing lines between the components, namely the outer skin 12, the SFR layer 18, the inner skin 14, and the upper and lower core sheets 30, 32 - all as Figure 6 schematically shown, are only used to describe how the components are assembled together after the SPF / DB manufacturing process. In fact, after the manufacturing of such an outer panel 10, any cross-section taken will not show visible dividing lines because the components will subsequently be integrally joined together into a unified structure.

[0029] Continuing to refer to Figure 6 , it should be understood that the intermittent seam welding of each of the first and second arrays 34, 36, the upper outer skin 12 with the enhanced SFR layer 18, and the lower inner skin 14 limit the individual units 52' of the core 16 of the superplastic formed and diffusion bonded outer panel 10. In the example, the SFR layer can be fusion welded or at least spot welded to the outer skin 12 before the assembly of the components and before the entry of the inert gas G.

[0030] Now also referring to Figure 7 , the pressure containment device, such as the superplastic forming press 60, includes a lower member such as the containment box 62, and an upper member such as the containment box cover 64, which is configured to be fixed to the containment box 62. It should be understood that Figure 4 the fixing device 40 - containing the prefabricated outer panel 10 ( Figure 3) Each of the above components is inserted into a superplastic forming press 60 to fabricate each finished outer panel 10 through the SPF / DB process. For this purpose, an inert gas G (such as argon) can be used to pressurize and form the outer panel 10, especially if such a structure is composed of superplastic formidable materials (such as the described titanium alloy and SFR components). Other inert gases may also be suitable for the above components.

[0031] Continuing to refer to Figure 7 , before pressurizing the superplastic forming press 60, the atmosphere is first purged from the superplastic forming press 60 using a non-corrosive gas (such as argon) because the atmosphere can be corrosive at the SPF / DB manufacturing temperature approaching 1700°F. For this purpose, purge and vacuum tubes such as vacuum tube 56, lower purge tube 58, upper purge tube 66, and purge vent 68 are all schematically shown as exemplary structures for accommodating prefabricated purging. After each instance of SPF / DB manufacturing of the outer panel 10 is completed, the finished outer panel 10 (such as Figure 1 ) is removed from the superplastic forming press and trimmed. Thus, Figure 1 depicts the completed and fully trimmed outer panel 10, that is, it has been removed from the superplastic forming press 60 and the fixture 40, and the expansion tube 50 has been removed.

[0032] It can be noted that during hypersonic flight, the steady-state operating temperature of the outer skin 12 of the outer panel 10 made of titanium alloy can be as high as in the range of 1100 to 1200°F. The thickness of the outer skin 12 can range from five thousandths of an inch to about sixty thousandths of an inch, while the SFR layer (18) can be in the range of 80% to 150% of the thickness of the outer skin (12). In addition, the SFR layer (18) can be located at least 20% to 80% below the outer skin (12). The thickness of the core wafers 30, 32 can be in the range of 1 mm or forty thousandths of an inch, and the thickness of the inner skin 14 can be comparable to or slightly smaller than the thickness of the outer skin 12. The pressure of the gas G during the SPF / DB manufacturing process can be in the range between 200 - 500 psi.

[0033] Now referring to Figure 8 , an alternative enhanced SFR layer 78 is shown. The SFR layer 78 is formed using the SPF / DB manufacturing process, which is similar to the previously described example, that is, Figure 1 the SFR layer 18, but can include a plurality of circular holes 80, shown only as an example in Figure 8 .

[0034] Now referring to Figure 9 , fabricating for a transportation vehicle 20 ( Figure 2)Exemplary outer panel 10( Figure 1 )The method includes step 150 of providing an outer skin 12 of a superplastic material (such as a titanium alloy) configured for atmospheric exposure. The method also provides step 152 of securing an SFR layer 18 to the outer skin 12 and step 154 of providing an inner skin 14. The inner skin is also made of a superplastic material and is configured to be attached to a structural frame member, such as a wing 22 of a transport vehicle 20. The method then includes step 156, which provides a pair of core sheets 30, 32 also made of a superplastic material for forming a multi-unit core 16 between the outer skin 12 and the inner skin 14. Next, according to step 158, the core sheets 30, 32 are joined together by intermittent seam welding arranged in a predetermined pattern, as exemplified by arrays 34 and 36( Figure 3 ).

[0035] According to step 160, an expansion tube 50 is then secured to one edge of the core sheets 30, 32, and then a continuous weld is applied around all edges of the layers in step 162. In step 164, the outer skin 12 and the inner skin 14 are inserted into a fixing device 40 together with the core sheets 30, 32, and then placed in a pressure containment device such as a superplastic forming press 60. In step 166, the superplastic forming press 60 is purged, and an inert gas G is supplied to the expansion tube 50 to superplastically pressurize the skins and layers to form a multi-unit core 16 that is integrally bonded to the outer skin and the inner skin 12, 14.

[0036] As described above, during the SPF / DB process, pressures of 200–500 psi may be reached during the superplastic forming of the above-described outer panel 10.

[0037] Although only a few examples and method steps are described herein, the present disclosure may permit other variations and modifications not described or implied. For example, although not described above, the outer panel 10 may have other multi-unit core configurations, which result in significantly lighter, simpler, and less expensive structures. For example, in some envisioned examples, the multi-unit core may be formed from only a single layer of core sheet. Additionally, inert gases other than argon may be used during the SPF / DB process to fabricate the outer panel 10. Further, it is foreseeable that material compositions other than the described TZM and Incoloy materials may be used for the disclosed superplastically formable reinforcement (SFR) layer 18 to support the outer skin 12 such that their high strength and tensile properties remain effective in environments exceeding 1200 degrees Fahrenheit. Finally, as will be understood by those skilled in the art, several other feasible methods not described herein may be envisioned for fabricating the outer panel 10.

[0038] Clause 1: An outer panel for a transportation vehicle, the outer panel including an outer skin configured for atmospheric exposure; an inner skin configured for attachment to a structural frame member of the transportation vehicle; a multi-cell core sandwiched between the outer skin and the inner skin; and a superplastic formable reinforcement (SFR) layer beneath the outer skin and supporting the outer skin, wherein the multi-cell core is superplastic formed and diffusion bonded to the outer skin and the inner skin.

[0039] Clause 2: The outer panel according to Clause 1, wherein all components other than the SFR layer are formed of a titanium alloy.

[0040] Clause 3: The outer panel according to Clause 1 or 2, wherein the SFR layer is formed of a superplastic formable alloy consisting of titanium, zirconium, and molybdenum (TZM).

[0041] Clause 4: The outer panel according to Clauses 1 - 3, wherein the SFR layer is formed of a superplastic formable alloy consisting of Incoloy 909.

[0042] Clause 5: The outer panel according to Clauses 1 - 4, wherein the SFR layer includes a skeletal structure located beneath 20% to 80% of the outer skin.

[0043] Clause 6: The outer panel according to Clauses 1 - 5, wherein the SFR layer is configured to reinforce the outer skin at temperatures in a range above 1200 degrees Fahrenheit.

[0044] Clause 7: The outer panel according to Clauses 1 - 6, wherein the SFR layer is 80% to 150% of the thickness of the outer skin.

[0045] Clause 8: A transportation vehicle having at least one outer panel, the at least one outer panel including an outer skin configured for atmospheric exposure; an inner skin configured for attachment to a structural frame member of the transportation vehicle; a multi-cell core configured to impart tensile and compressive strength to the outer panel, the multi-cell core being sandwiched between the outer skin and the inner skin; and an SFR layer beneath the outer skin and supporting the outer skin when the temperature on the outer skin exceeds a predetermined threshold temperature; wherein the multi-cell core is superplastic formed and diffusion bonded to the outer skin and the inner skin.

[0046] Clause 9: The transportation vehicle according to Clause 8, wherein the transportation vehicle is a hypersonic vehicle having a plurality of outer panels, and wherein each outer panel is fusion welded to at least one other outer panel.

[0047] Clause 10: The transport vehicle according to Clause 8 or 9, wherein each SFR layer of each outer panel among the plurality of outer panels includes an SFR layer that is diffusion-bonded to the outer skin to strengthen the outer skin at a temperature above 1200 degrees Fahrenheit.

[0048] Clause 11: The transport vehicle according to Clauses 8 - 10, wherein the SFR layer is formed of a TZM material.

[0049] Clause 12: The transport vehicle according to Clauses 8 - 11, wherein the SFR layer is formed of Incoloy 909.

[0050] Clause 13: A method of manufacturing an outer panel for a transport vehicle, the method comprising providing an outer skin of a superplastic material configured for atmospheric exposure; providing an SFR layer fixed adjacent to the outer skin; providing an inner skin of a superplastic material configured to be attached to a structural frame member of the transport vehicle; providing at least a pair of core sheets of a superplastic material for forming a multi-unit core between the outer skin and the inner skin; then fixing the SFR layer to the outer skin; joining the pair of core sheets together by intermittent seam welding arranged in a predetermined pattern, fixing an expansion tube on one edge of the sheets, and then applying continuous welding around the edges of the sheets; installing the outer skin, the inner skin, and the core sheets together into a pressure containment device, supplying an inert gas into the expansion tube to superplastic form and diffusion-bond the skins and the core sheets to form a multi-unit core that is integrally bonded to the outer skin and the inner skin.

[0051] Clause 14: The method according to Clause 13, wherein the SFR layer is configured to support the outer skin when the temperature of the outer skin exceeds a predetermined threshold.

[0052] Clause 15: The method according to Clause 13 or 14, wherein the SFR layer is formed of a TZM material.

[0053] Clause 16: The method according to Clauses 13 - 15, wherein the SFR layer is formed of Incoloy 909.

[0054] Clause 17: The method according to Clauses 13 - 16, wherein the SFR layer is 80% to 150% of the thickness of the outer skin.

[0055] Clause 18: The method according to Clauses 13 - 17, wherein the SFR layer is located 20% to 80% below the outer skin.

[0056] Clause 19: The method according to Clauses 13 - 18, wherein the SFR layer includes a skeleton structure located below the outer skin.

[0057] Clause 20: According to the method described in Clauses 13 - 19, wherein when the temperature of the outer skin exceeds 1200 degrees Fahrenheit, the SFR layer supports the outer skin.

Claims

1. An outer panel (10) for a transport vehicle (20), the outer panel comprising: An outer skin (12) configured for exposure to the atmosphere; An inner skin (14) configured to be attached to a structural frame member of the transport vehicle (20); A multi-unit core (16) sandwiched between the outer skin (12) and the inner skin (14), and the multi-unit core (16) includes at least a pair of core sheets (30, 32) of superplastic material joined together by intermittent seam welding arranged in a predetermined pattern; continuous welding around the edges of the core sheets (30, 32); and A superplastic formable reinforcement layer (18) under the outer skin (12) and supporting the outer skin (12), the superplastic formable reinforcement layer (18) being configured to support the outer skin (12) when the atmospheric friction temperature of the outer skin (12) exceeds 1200 degrees Fahrenheit. Wherein the multi-unit core (16) is superplastic formed and diffusion bonded to the outer skin (12) and the inner skin (14).

2. The outer panel (10) according to claim 1, wherein the outer skin (12), the inner skin (14) and the multi-unit core (16) except for the superplastic formable reinforcement layer (18) are all formed of a titanium alloy.

3. The outer panel (10) according to claim 1, wherein the superplastic formable reinforcement layer (18) is formed of a superplastic formable alloy consisting of titanium, zirconium and molybdenum (TZM) or is formed of a superplastic formable alloy consisting of Incoloy 909.

4. The outer panel (10) according to claim 1, wherein the superplastic formable reinforcement layer (18) includes a framework structure located under 20% to 80% of the outer skin (12).

5. The outer panel (10) according to any one of claims 1-4, wherein the superplastic formable reinforcement layer (18) is 80% to 150% of the thickness of the outer skin (12).

6. A transport vehicle (20) having at least one outer panel (10), the at least one outer panel comprising: An outer skin (12) configured for exposure to the atmosphere; An inner skin (14) configured to be attached to a structural frame member of the transport vehicle (20); A multi-unit core (16) configured to impart tensile and compressive strength to the outer panel (10), the multi-unit core (16) being sandwiched between the outer skin (12) and the inner skin (14), and the multi-unit core (16) includes at least a pair of core sheets (30, 32) of superplastic material joined together by intermittent seam welding arranged in a predetermined pattern; continuous welding around the edges of the core sheets (30, 32); and A superplastic formable reinforcement layer (18) under the outer skin and supporting the outer skin when the temperature on the outer skin exceeds 1200 degrees Fahrenheit. Wherein the multi-cell core (16) is superplastically formed and diffusion bonded to the outer skin (12) and the inner skin (14).

7. The vehicle (20) according to claim 6, wherein the vehicle is a hypersonic vehicle having a plurality of outer panels (10), and wherein each outer panel (10) is fusion welded to at least one other outer panel (10).

8. The vehicle (20) according to claim 7, wherein each outer panel of the plurality of outer panels (10) includes a superplastically formable reinforcement layer (18) that is diffusion bonded to the outer skin (12) to reinforce the outer skin (12) at a temperature above 1200 degrees Fahrenheit.

9. The vehicle (20) according to any one of claims 6 to 8, wherein the superplastically formable reinforcement layer (18) is formed of TZM material or Incoloy 909.

10. A method of manufacturing an outer panel (10) for a vehicle (20), the method comprising: Providing an outer skin (12) of superplastic material configured for atmospheric exposure; Providing a superplastically formable reinforcement layer (18) fixed adjacent to the outer skin (12), the superplastically formable reinforcement layer (18) configured to support the outer skin (12) when the atmospheric friction temperature of the outer skin (12) exceeds 1200 degrees Fahrenheit; Providing an inner skin (14) of superplastic material configured to be attached to a structural frame member of the vehicle (20); Providing at least a pair of core sheets (30, 32) of superplastic material for forming a multi-cell core (16) between the outer skin (12) and the inner skin (14); and then Fixing the superplastically formable reinforcement layer (18) to the outer skin (12); Bonding the pair of core sheets (30, 32) together by intermittent seam welding in a predetermined pattern, fixing an expansion tube (50) at one edge of the pair of core sheets (30, 32), and then applying continuous welding around the edge of the pair of core sheets (30, 32); and Mounting the outer skin (12), the inner skin (14), and the pair of core sheets (30, 32) together into a pressure containment device (60), supplying an inert gas into the expansion tube (50) to superplastically form and diffusion bond the outer skin (12), the inner skin (14), and the pair of core sheets (30, 32) to form a multi-cell core (16) that is integrally bonded to the outer skin (12) and the inner skin (14).

11. The method according to claim 10, wherein the superplastically formable reinforcement layer (18) is formed of TZM material or Incoloy 909.

12. The method according to claim 10, wherein the superplastically formable reinforcement layer (18) is 80% to 150% of the thickness of the outer skin (12).

13. The method according to claim 10, wherein the superplastic formable reinforcing layer (18) is located between 20% and 80% below the outer skin (12).

14. The method according to claim 10, wherein the superplastic formable reinforcing layer (18) comprises a framework structure below the outer skin (12).

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