Integral forming die for U-shaped stiffened wall plate

Abstract

The invention provides an integral forming die for a U-shaped stiffened wallboard. The integral forming die comprises a wallboard appearance die, a stringer rigid die, a stringer flexible die and a stringer positioning assembly. The wall plate appearance mold is used for positioning and mounting a skin preform, and the inner molded surface of the wall plate appearance mold is matched with the design appearance of the skin preform; the stringer rigid mold is arranged in the stringer pre-forming body, and the stringer rigid mold is positioned and connected to the wallboard appearance mold; the stringer flexible dies are arranged in the stringer preformed body, and the stringer rigid dies and the stringer flexible dies are arranged in a staggered mode; the stringer positioning assembly comprises a transverse positioning beam and a plurality of stringer limiting blocks, the transverse positioning beam is connected to the wallboard appearance mold, the stringer limiting blocks are installed and connected to the transverse positioning beam, and the stringer limiting blocks and the stringer rigid molds are clamped in a one-to-one correspondence mode. According to the U-shaped stiffened wallboard forming device, integral forming of the U-shaped stiffened wallboard can be achieved, the forming quality is good, the forming efficiency is high, and the operation risk is low.

Description

Technical Field

[0001] The present invention relates to the technical field of composite panel forming, and more specifically, to an integral forming mold for a U-shaped stiffened panel. Background Art

[0002] Composite stiffened panels are typical structural forms of aircraft composites and have been widely used in aircraft structures such as fuselages and wing surfaces. By strengthening thin-walled skins with stiffeners, while meeting the requirements of structural strength and stiffness, the weight reduction efficiency of the structure is improved. According to the different cross-sectional forms of the stiffeners, conventional stiffened panels can be divided into various stiffened panel structures such as "L"-type, "J"-type, "T"-type, and "I"-type. The stiffeners and the skin are usually relatively independent. The forming methods mainly include: ① secondary bonding and forming after the ribs and the skin are cured separately; ② one of the ribs or the skin is cured first, and is bonded and cured with the uncured ribs or skin while curing, that is, co-bonding and forming; ③ the skin and the ribs are laid separately, and the laid skin and ribs are combined together for co-curing and forming.

[0003] A U-shaped stiffened panel refers to a stiffened panel with a "U"-shaped cross-section. The adjacent two "U"-shaped web surfaces form a stiffened vertical edge, and the bottom surface is integrated with the skin and becomes a part of the skin ply, as Figure 1 shown. There are also three forming schemes for the U-shaped stiffened panel: secondary bonding, co-bonding, and co-curing. Compared with the relatively independent conventional "L"-type, "J"-type, "T"-type, and "I"-type stiffened panels, since the bottom surface of the U-shaped stiffener has been used as a part of the skin ply, the wall panel structure of the "U"-shaped stiffener + skin has better integrity, higher structural efficiency, and more obvious weight reduction effect. However, the "U"-shaped stiffeners in this structural form restrict each other. If the forming method of secondary bonding or co-bonding the cured "U"-shaped stiffeners with the skin is adopted, the forming mold for a single "U"-shaped stiffener unit is relatively simple, the pressurization is relatively easy, and the flatness is easy to guarantee. Because each "U"-shaped stiffener unit is cured and shaped, and its thickness has also been pressurized and compacted, when bonding and assembling with the skin, the "U"-shaped stiffeners can be combined in place, and there is no problem of pressurizing each surface of the "U"-shaped stiffeners during bonding. At this time, it is relatively easy to realize the secondary bonding and co-bonding of the U-shaped stiffened panel.

[0004] With the increasing use of composite materials, higher requirements are put forward for the weight reduction efficiency and cost of composite material structures. Integral forming of stiffened panels can further reduce the number of equipment uses and shorten the manufacturing cycle. Achieving integral forming of composite material structures has become a trend in the development of composite materials. In a certain project, "U"-shaped panel structures are widely used in the fuselage, wings and other panels, and integral forming of multiple "U"-shaped ribs and skins is required to reduce the manufacturing cost of composite materials. However, for "U"-shaped stiffened panels, when the "U"-shaped ribs are not cured, since each "U"-shaped rib unit has not been pressurized and compacted, its thickness is still greater than the theoretical thickness. When co-bonding with the cured skin or co-curing and assembling with the uncured skin, there will be cumulative deviations when the "U"-shaped ribs are combined together, resulting in the situation that they cannot be assembled in place, leading to the inability to position the ribs. At the same time, during the curing process, the pressurization of each surface of the "U"-shaped rib and the surface flatness problem also need to be considered. The co-bonding and co-curing forming of the uncured "U"-shaped rib and the skin is difficult, which is prominently manifested in the difficulty of combining the "U"-shaped ribs, the problem that the positioning device cannot be normally assembled due to the improper combination, and the difficulty in ensuring the position accuracy of the "U"-shaped stringers. On the other hand, the traditional positioning method usually designs positioning keels to position the ribs. When vacuum bag packaging, the keels are sealed outside the vacuum bag. For multi-ribbed stiffened panels with a large number of stringers and high density, the number of positioning points is large, and each positioning point needs to be sealed with the vacuum bag, with many risk points. Moreover, the prominent positioning keels interfere with the vacuum bag packaging operation or even make it impossible to operate.

[0005] It can be seen that for the integral forming of "U"-shaped stiffened panels, during the curing process, it is necessary to simultaneously ensure the pressurization of each area of the "U"-shaped stringers, the stringer profiling, and the stringer positioning. During the process, it is necessary to solve the problem that multiple "U"-shaped stringers cannot be properly combined, and the resulting problems such as surface unevenness. For the integral forming of "U"-shaped stiffened panels, the design of the forming tooling and positioning method and the formulation of the forming process plan are the keys related to the forming quality of the panel. Summary of the Invention

[0006] (1) Technical Problems to be Solved

[0007] The technical problem to be solved by the present invention is that the existing forming molds are difficult to achieve the integral forming of "U"-shaped stiffened panels.

[0008] (2) Technical Solutions

[0009] To achieve the above object, the technical solution adopted by the present invention is:

[0010] Provided is an integral forming die for a U-shaped stiffened panel, which is used to position and fix a skin preform and a plurality of stringer preforms, and includes a panel profile die, a stringer rigid die, a stringer flexible die and a stringer positioning component; the panel profile die is used to position and install the skin preform, and the inner profile surface of the panel profile die is adapted to the designed profile of the skin preform; the stringer rigid die is arranged inside the stringer preform, and the stringer rigid die is positioned and connected to the panel profile die; the stringer flexible die is arranged inside the stringer preform, and a plurality of the stringer rigid dies and a plurality of the stringer flexible dies are arranged alternately; the stringer positioning component includes a transverse positioning beam and a plurality of stringer limit blocks, the transverse positioning beam is connected to the panel profile die, a plurality of the stringer limit blocks are installed and connected to the transverse positioning beam, and a plurality of the stringer limit blocks are respectively and correspondingly clamped with a plurality of the stringer rigid dies.

[0011] Preferably, a plurality of stringer rigid dies are sequentially spliced end to end along the length direction of the stringer rigid die, inverted trapezoidal grooves are provided at both ends of the splicing part of the stringer rigid dies, the stringer limit blocks are inverted trapezoidal blocks, and the stringer limit blocks are clamped in the inverted trapezoidal grooves.

[0012] Preferably, the taper of the inverted trapezoidal groove is 2°-6°.

[0013] Preferably, the length of each stringer rigid die is not greater than 1200 mm, and the splicing parts of the plurality of stringer rigid dies in the width direction are coplanar.

[0014] Preferably, it further includes a uniform pressing plate, and the uniform pressing plate is arranged at the splicing part of two adjacent stringer rigid dies.

[0015] Preferably, the stringer positioning component further includes a connecting block and a positioning block, the connecting block is connected to the transverse positioning beam, the stringer limit block is connected to the connecting block, positioning blocks are respectively arranged at both ends of the transverse positioning beam, and the positioning blocks are used for positioning and installing on the panel profile die.

[0016] Preferably, it further includes a positioning plate, the positioning plates are respectively arranged at both ends of the panel profile die, and the end part of the stringer rigid die is positioned and connected to the positioning plate.

[0017] Preferably, it further includes a plurality of positioning pins, the positioning plate is provided with a plurality of pin holes, and a plurality of the positioning pins are respectively and correspondingly positioned and connected to a plurality of stringer rigid dies and a plurality of pin holes.

[0018] Preferably, the cross section of the stringer rigid die is a U-shaped hollow structure, the thickness of the stringer rigid die is not greater than 8 mm, and both ends of the stringer rigid die are flush with the outer edge of the positioning plate.

[0019] Preferably, the material of the stringer rigid mold is steel or aluminum, and / or the stringer flexible mold is a combination of rubber, fiber cloth and rubber, or fiberglass.

[0020] (III) Beneficial effects

[0021] The above technical solutions of the present invention have at least the following advantages:

[0022] 1. In the present invention, by the way of staggered arrangement and alternating layout of multiple stringer rigid molds and multiple flexible molds, and by using the stringer positioning component to constrain the stringer rigid mold, while ensuring the flatness of the stringer profile, the problem of uniform pressure in each area of the large-size U-shaped stiffened panel is solved. At the same time, it is convenient for the positioning and assembly of the mold and the demolding after forming.

[0023] 2. In the present invention, in the middle section of the long and slender stringer preform, a stringer limiting mold with a trapezoidal cross-section is used to position the stringer rigid mold, which solves the problem that the pin positioning cannot be used for the stringer rigid mold with a hollow structure. The trapezoidal cross-section cooperates with the stringer rigid mold, which is convenient for assembly and demolding. In addition, the stringer limiting mold can simultaneously position the adjacent stringer rigid molds that have been segmented, avoiding the step difference on the part surface caused by the misalignment of the segmented stringer rigid molds at the docking position.

[0024] 3. In the present invention, the stringer limiting mold is designed on one side of the transverse positioning beam and is encapsulated in the vacuum bag. During the forming process, it can move together with the stringer rigid mold under the action of vacuum and external pressure. The movement along the normal direction of the skin can make the stringer rigid mold reach the theoretical position, ensuring the positioning and limiting effect of the stringer limiting mold on the stringer rigid mold. The movement along the longitudinal direction can eliminate the deviation caused by the inconsistent thermal expansion between the molds during the heating and cooling process.

[0025] 4. In the present invention, the stringer limiting mold is designed on one side of the transverse positioning beam. When the normals of the skins in each stringer preform area are inconsistent, the stringer limiting mold is designed to be detachably connected to the connecting block of the transverse positioning beam, which can realize the assembly positioning and demolding of all stringer rigid molds in different normal areas with the transverse positioning beam.

[0026] 5. In the present invention, while meeting the structural positioning requirements, the positioning combination of this structural form can be completely encapsulated in the vacuum bag, overcoming the problems of difficult or even impossible vacuum bag encapsulation operation, low encapsulation efficiency, and air leakage risk when using the traditional gantry positioning method. Especially for the integral forming of the stiffened panel with a large number of stringers, small spacing and high density, it provides an operable, efficient and low-risk positioning method. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0028] Figure 1 It is a schematic structural diagram of the U-shaped stiffened panel provided in Embodiment 1 of the present invention.

[0029] Figure 2 It is a schematic structural diagram of the integral forming die of the U-shaped stiffened panel provided in Embodiment 1 of the present invention.

[0030] Figure 3 It is a schematic layout diagram of the stringer rigid die and the stringer flexible die provided in Embodiment 1 of the present invention.

[0031] Figure 4 It is a schematic diagram of the positioning method for the middle part of the stringer preform provided in Embodiment 1 of the present invention.

[0032] Figure 5 It is a schematic structural diagram of the U-shaped stiffened panel provided in Embodiment 2 of the present invention.

[0033] Figure 6 It is a schematic structural diagram of the integral forming die of the U-shaped stiffened panel provided in Embodiment 2 of the present invention.

[0034] The reference numerals in the figure are as follows:

[0035] 1, panel outer die; 2, stringer rigid die; 3, stringer flexible die; 4, equalizing plate; 5, transverse positioning beam; 6, positioning block; 7, stringer limiting block; 8, connecting block; 9, positioning plate; 2-1, first stringer rigid die; 2-2, second stringer rigid die; 3-1, second stringer flexible die; 3-2, first stringer flexible die; 7-1, first stringer limiting block; 7-2, second stringer limiting block; 8-1, first connecting block; 8-2, second connecting block. Detailed implementation manners

[0036] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as "connected to" another element, it can be directly connected or indirectly connected to the other element.

[0038] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention, rather than indicating that the device or component must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0039] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating relative importance or indicating the quantity of technical features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined. The following describes the specific implementation of the present invention in more detail with reference to specific embodiments:

[0040] As Figure 1 shown, a typical U-shaped stiffened panel a structure is composed of a skin preform c and a plurality of stringer preforms a-1 to a-9 arranged in parallel thereon. The bottom surface of the stringer preform is integrated with the skin preform c as part of the skin, and integral forming is carried out by means of an autoclave process. According to different process designs, the stringer preform can be a U-shaped stringer preform and an L-shaped stringer preform, or can be formed by combining a plurality of stringer preforms of other shapes.

[0041] As Figure 1 、 Figure 2 and Figure 3 shown, an embodiment of the present invention provides an integral forming die for a U-shaped stiffened panel, which is used to position and fix the skin preform c and a plurality of stringer preforms (a-1 to a-9). The integral forming die for the U-shaped stiffened panel includes a panel outer shape die 1, a stringer rigid die 2, a stringer flexible die 3, and a stringer positioning component; the panel outer shape die 1 is used to position and install the skin preform c, and the inner surface of the panel outer shape die 1 is adapted to the designed outer shape of the skin preform c; the stringer rigid die 2 is arranged inside the stringer preform, and the stringer rigid die 2 is positioned and connected to the panel outer shape die 1; the stringer flexible die 3 is arranged inside the stringer preform, and a plurality of stringer rigid dies 2 and a plurality of stringer flexible dies 3 are arranged alternately; the stringer positioning component includes a transverse positioning beam 5 and a plurality of stringer limiting blocks 7. The transverse positioning beam 5 is connected to the panel outer shape die 1, and a plurality of stringer limiting blocks 7 are installed and connected to the transverse positioning beam 5, and a plurality of stringer limiting blocks 7 are in one-to-one clamping connection with a plurality of stringer rigid dies 2.

[0042] Specifically, in this embodiment, the panel contour die 1 is used to form the aerodynamic surface of the panel, ensure the aerodynamic contour requirements of the panel, and serve as the positioning reference for other components. The panel contour die 1 adopts a frame structure, and the surface of the panel contour die 1 is designed after reserving the thickness of the demolding material according to the external surface of the panel.

[0043] In this embodiment, the stringer rigid die 2 and the stringer flexible die 3 are located inside the stringer preform. To balance the requirements of ensuring stringer pressing and surface, the stringer rigid die 2 and the stringer flexible die 3 are arranged in a staggered manner, as Figure 3 shown.

[0044] As a preferred implementation, when the bottom surface of some stringer preforms is relatively complex, such as a large curvature surface or a composite surface, the stringer flexible die 3 is preferably arranged inside the more complex stringer preform, and the stringer rigid die 2 is arranged inside the adjacent stringer preform, and so on.

[0045] As a preferred implementation, when the bottom surfaces of all stringer preforms are relatively simple, such as all bottom surfaces are flat or single curvature surfaces, the stringer rigid die 2 can be sequentially selected and arranged inside the 1st, 3rd... stringer preforms from one side of the U-shaped stiffened panel, and the stringer flexible die 3 is arranged inside the adjacent stringer preform, and so on.

[0046] Furthermore, the stringer rigid die 2 preferably avoids the closed corner area. When the stringer rigid die 2 must be in the closed corner area, the stringer rigid die 2 in this area is designed with a transverse split design during design, and the integral structure is split into multiple components to facilitate demolding.

[0047] In one of the embodiments, multiple stringer rigid dies 2 are sequentially spliced end to end along the length direction of the stringer rigid die 2. The stringer rigid dies 2 at both ends of the splicing position are provided with inverted trapezoidal grooves 21, and the stringer limit block 7 is an inverted trapezoidal block, and the stringer limit block 7 is clamped in the inverted trapezoidal groove.

[0048] In one of the embodiments, the taper of the inverted trapezoidal groove is 2° - 6°. At the segmented position of the stringer rigid die 2, the cavity on both sides within 30 mm of the adjacent stringer rigid die 2 and the stringer limit block 7 is designed as a trapezoid with a wider upper part and a narrower lower part, and the taper is not greater than 2° - 6°, which is consistent with the taper of the corresponding stringer limit block 7.

[0049] In one embodiment, the length of each stringer rigid die 2 is not greater than 1200 mm, and the joints of multiple stringer rigid dies 2 in the width direction are coplanar. To reduce the processing difficulty of the stringer rigid die 2 and minimize the adverse effects of the deformation of the stringer rigid die 2 on the pressurization of the part, the stringer rigid die 2 is butt-jointed after being segmented in the length direction, so that the length of each segment is not greater than 1200 mm. The segmented positions are preferably the positions of the frames and ribs that have an assembly relationship with the stringer preform, and the segmented positions of multiple stringer rigid dies 2 are required to be coplanar.

[0050] In one embodiment, it further includes a pressure equalizing plate 4, and the pressure equalizing plate 4 is arranged at the joint of two adjacent stringer rigid dies 2. Specifically, the pressure equalizing plate 4 is made of a rigid material, located at the butt-joint of the segmented stringer rigid die 2 and the bottom surface of the inner cavity of the stringer rigid die 2. Its length is not greater than the distance between the tangent points of the lower R corner of the inner cavity of the stringer rigid die 2. The width is not less than 10 mm on one side compared with the width of the stringer limit block 7 at its position, and the thickness is preferably 1.0 mm - 3.0 mm.

[0051] In one embodiment, the stringer positioning assembly further includes a connecting block 8 and a positioning block 6. The connecting block 8 is connected to the transverse positioning beam 5, the stringer limit block 7 is connected to the connecting block 8, and positioning blocks 6 are respectively arranged at both ends of the transverse positioning beam 5. The positioning blocks 6 are used for positioning and installing on the skin profile die 1. Between the two side part margin lines of the skin profile die 1 perpendicular to the stringer and the vacuum bag sealing position, corresponding to both ends of the transverse positioning beam 5, positions for positioning the positioning blocks 6 for the transverse positioning beam 5 are reserved for the positioning and installation of the positioning blocks 6. Specifically, the transverse positioning beam 5 spans across all stringer preforms, and both ends are positioned and connected to the skin profile die 1 through the cylindrical pins on the two side positioning blocks 6. The height of the positioning pins is not greater than 5 mm. The pin holes at both ends of the transverse positioning beam 5 have a circular hole at one end and a long circular hole at the other end. The connecting block 8 is located above the stringer limit block 7 and is fixed or connected to the side surface of the transverse positioning beam 5. The connecting block 8 serves as a link for the transverse positioning beam 5 to position the stringer limit block 7. After the connecting block 8 is fixed to the transverse positioning beam 5, the axis direction of the pin hole is along the normal direction of the skin in this area, and it combines with the stringer limit block 7 to achieve the positioning of the stringer rigid die 2.

[0052] As a preferred implementation manner, when the axis direction of the pin hole of the connecting block 8 is the same as the axis direction of the pins on the two side positioning blocks 6, the connecting block 8 can be designed as a fixed type or a detachable type.

[0053] As a preferred implementation manner, when the axis direction of the pin hole of the connecting block 8 is different from the axis direction of the pins on the two side positioning blocks 6, the connecting block 8 is designed as a detachable type. During assembly, this type of connecting block 8 needs to be combined with the stringer rigid die 2 first, and then connected and fixed to the transverse positioning beam 5.

[0054] In one embodiment, it further includes a positioning plate 9 which is respectively arranged at both ends of the skin profile die 1, and the end part of the stringer rigid die 2 is positioned and connected to the positioning plate 9. Specifically, between the part allowance lines at both ends of the stringer of the skin profile die 1 and the vacuum bag sealing position, a position for the positioning plate 9 for positioning the end part of the stringer rigid die 2 is reserved for the positioning and installation of the positioning plate 9. Further, the skin profile die 1 is designed with leak-proof blocks under the position templates corresponding to the two side positioning blocks 6 and the end positioning plate 8, and the leak-proof blocks are welded during die welding, and it is required to meet the vacuum degree requirements for part forming within the skin sealing area including all positioning blocks and positioning plates. The positioning plate 9 is fixed on the skin profile die 1. The minimum length of the positioning plate 9 is not less than the outer edge length of the outermost stringer rigid die 2, the width is preferably 30 mm to 50 mm, and the thickness of the positioning plate 9 is not greater than the lower limit of the skin thickness of the wall panel. A cylindrical pin is fixed at the midline position of the positioning plate 9 corresponding to the stringer rigid die 2. The length of the cylindrical pin is not greater than the bottom thickness of the end stringer rigid die. A positioning hole is designed at the end part of the corresponding stringer rigid die 2, and the end stringer rigid die 2 is positioned and connected to the skin profile die 1 through the positioning pin.

[0055] In one embodiment, it further includes a plurality of positioning pins (not shown). The positioning plate 9 is provided with a plurality of pin holes, and the plurality of positioning pins are respectively and correspondingly positioned and connected to the plurality of stringer rigid dies 2 and the plurality of pin holes.

[0056] In one embodiment, the cross-section of the stringer rigid die 2 is a U-shaped hollow structure. The thickness of the stringer rigid die 2 is not greater than 8 mm to facilitate heat transfer and is beneficial to pressure uniformity. The outer profile surface is designed according to the shape and size of the inner cavity of the stringer preform after reserving the thickness of the isolation material. The two ends of the stringer rigid die 2 are flush with the outer edge of the positioning plate 9, and the upper edges on both sides are not lower than the allowance edges of the stringer preform.

[0057] In one embodiment, the material of the stringer rigid die 2 is steel or aluminum; in one embodiment, the stringer flexible die 3 is a combination of rubber, fiber cloth and rubber, or fiberglass.

[0058] Specifically, the two ends of the stringer flexible die 3 are flush with the skin allowance line of the wall panel, and the edges on both sides are consistent with the edges of the adjacent stringer rigid dies 2. The stringer flexible die 3 is preferably made of rubber, fiber cloth + rubber, fiberglass integral die or a combined die of fiberglass plates. When the stringer flexible die 3 is made of rubber, fiber cloth + rubber, fiberglass integral die or a combined die of fiberglass plates, it can better ensure the flatness of the inner surface of the part while ensuring part pressing. When the flatness requirement of the inner surface of the part is relatively low, release cloth, PTFE cloth and other isolation materials, or isolation materials + polyester film can be directly used.

[0059] Furthermore, the stringer flexible mold 3 made of rubber, fiber cloth + rubber, and fiberglass material as a whole needs to be fabricated through a soft mold forming mold with a profile consistent with the inner cavity of the stringer preform, resulting in a relatively high cost. Considering cost factors, when the bottom surface of the stringer preform is flat or has a small curvature, the stringer flexible mold 3 preferably selects a combined mold made of fiberglass plates. When the bottom surface of the stringer preform has a large curvature, the stringer flexible mold 3 selects a mold made of rubber, fiber cloth + rubber, and fiberglass material as a whole, and is fabricated through a soft mold forming mold into a stringer flexible mold 3 with the same shape and size as the inner cavity.

[0060] More specifically, the stringer limit block 7 is designed at the segmented position of the stringer rigid mold 2, and positions two adjacent segments of the stringer rigid mold 2 simultaneously through two side surfaces. The two side surfaces cooperating with the stringer rigid mold 2 are designed as trapezoids with a wider upper part and a narrower lower part, and the taper is not greater than 2° - 6°, which is consistent with the taper on both sides of the cavity of the stringer rigid mold 2 at the corresponding position. A positioning pin is fixed at the mid-axis position of the top surface of the stringer limit block 7. The positioning pin is a cylindrical pin with a length of not less than 20 mm, and the axis of the positioning pin is parallel to the normal of the skin of the panel at this position. After the stringer limit block 7 and the stringer rigid mold 2 are combined, the gap between the bottom surface of the stringer limit block 7 and the cavity of the stringer rigid mold 2 is not less than the thickness of the equalizing plate 4. The top surface of the stringer limit block 7 is 10 mm - 15 mm higher than the upper edges on both sides of the stringer rigid mold 2, and the width of the stringer limit block 7 is preferably 20 mm - 40 mm. The transverse positioning beam 5 and the positioning blocks 6 on both sides are located on the side of the stringer limit block 7 away from the stringer preform, and are 0.5 mm - 2 mm away from the side surface of the stringer limit block 7. The bottom surface of the transverse positioning beam 5 is not less than 5 mm lower than the top surface of the stringer limit block 7 and not less than 5 mm higher than the upper edge of the stringer rigid mold 2. The width of the transverse positioning beam 5 is not greater than 40 mm, and the thickness is preferably not less than 30 mm. A connecting block 8 is fixed on the transverse positioning beam 5 above the stringer limit block 7. The mating surfaces with the positioning blocks are reserved at the opposite side and both ends of the bottom surface, and the rest of the area is chamfered.

[0061] In this embodiment, according to the different characteristics of the middle and end parts of the U-shaped stiffened panel, the middle part of the stringer preform is positioned by the stringer positioning assembly, and the end part of the stringer preform is positioned by the positioning plate 9. The positioning combinations of the middle and end parts both meet the encapsulation requirements. After the positioning combination is completed, the overall forming mold and the preform are encapsulated together in a vacuum bag, which is convenient for vacuum packaging and can avoid the risk of air leakage.

[0062] The following further elaborates on the present invention with specific embodiments:

[0063] Embodiment 1

[0064] As Figure 1The U-shaped stiffened panel a structure shown has a length of 6000 mm, a span of 806 mm, an unfolded width of 1008 mm, and is provided with 9 continuous stringer preforms a-1 to a-9, where a-2 and a-8 are in the profile change area. The stringer preforms are of a closed-angle structure, with 2 L-shaped stringer preforms on both sides. The length of the stringers is equal to that of the skin. The width of each U-shaped stringer preform is 100 mm and the height is 35 mm. The bottom surfaces of the U-shaped stringer preforms and the L-shaped stringer preforms are integrated with the skin ply as part of the skin, and the integral forming is carried out by the autoclave process. It is required that 30 mm of allowance be left around the panel during forming, and 10 mm of allowance be left at the upper edge of the stringers. The integral forming of this panel uses the integral forming die for the U-shaped stiffened panel provided by the present invention for integral forming, as Figure 2 shown, and the specific operation method is as follows:

[0065] I. Design the integral forming die for the U-shaped stiffened panel

[0066] 1-A. Design the outer panel die

[0067] The design of the outer panel die 1 needs to meet the requirements of the aerodynamic profile of the panel and serve as the positioning reference for all positioning devices. The outer panel die 1 adopts a frame structure. When forming, a release agent is intended to be used as the release material, so the profile of the outer panel die 1 is selected according to the outer profile of the U-shaped stiffened panel.

[0068] The two side profiles of the outer panel die 1 extend 20 mm along the part allowance line, and platform areas parallel to the bottom surface of the U-shaped stiffened panel are designed on both sides. The width of the platform area is 150 mm, and about 50 mm from the inner edge of the platform is reserved for fixing the positioning block 6.

[0069] The two ends of the outer panel die 1 extend 150 mm along the part allowance line, and 10 - 60 mm outside the part allowance line is used for fixing the positioning plate 9.

[0070] Leakage prevention blocks are designed below the outer panel die 1 at the positions of the corresponding positioning blocks 6 on both sides and the end positioning plate 8. The leakage prevention blocks are welded during die welding, and it is required that the vacuum degree requirements for part forming be met within the panel sealing area including all positioning blocks 6 and positioning plates 9.

[0071] 1-B. Design the inner panel die

[0072] ①. Considering the requirements of ensuring stringer pressing and the surface profile, multiple stringer rigid dies 2 and multiple stringer flexible dies 3 are arranged alternately, that is, in an alternating layout. The bottom surface profiles of the stringer preforms a-2 and a-8 are complex. In this area, the first stringer flexible die 3-2 is designed. For the stringer preforms a-2, a-9 adjacent to it, the stringer preforms a-3, a-7 at the bottom, and the stringer preform a-5 in the middle, stringer rigid dies 2 are designed. For a-4 and a-6 in the alternating positions, the second stringer flexible die 3-1 is designed. The stringer flexible die 3 is also used in the L-shaped stringer preform areas on both sides. The distribution of the stringer rigid dies 2 and stringer flexible dies 3 of this panel is as Figure 3 shown.

[0073] ②. The stringer rigid die 2 is made of aluminum alloy LY12CZ. The cross-section of the stringer rigid die 2 is designed as a U-shaped hollow structure, which is convenient for heat transfer and beneficial to the uniformity of pressing. The maximum thickness is 8 mm. The outer surface profile is offset 0.1 mm inward according to the inner surface profile of the U-shaped stringer preform. The upper edges on both sides are 5 mm higher than the margin line of the stringer allowance, and extend to be flush with the outer edge of the positioning plate 9 at both ends. The length of the stringer of this panel reaches 6000 mm, and the stringer rigid die 2 extends 75 mm at both ends, reaching 6150 mm. To reduce the processing difficulty of the rigid die and at the same time reduce the adverse impact of the deformation of the rigid die on the pressing of the part, each stringer rigid die is equally divided into 6 segments, each segment is 1025 mm long, and the stringer rigid die is butt-jointed after segmentation.

[0074] At the segmented position of the stringer rigid die 2, within 30 mm on both sides of the cavity where the adjacent stringer rigid die 2 cooperates with the stringer limit block 7, it is designed as a trapezoid with a wider upper part and a narrower lower part, and the taper is 3°, which is the same as the taper of the corresponding stringer limit block 7.

[0075] At the position where the stringer rigid die 2 is segmented and butt-jointed, on the inner cavity bottom surface of the stringer rigid die at the segmented butt-joint position of the stringer rigid die 2, an equalizing plate 4 is designed. The equalizing plate 4 is made of LY12CZ aluminum plate with a thickness of 2.0 mm. The length is not greater than the distance between the tangent points of the lower R corners of the inner cavity of the stringer rigid die 2, taking 60 mm. The width is not less than 10 mm on one side compared with the width of the stringer limit block 7 at the corresponding position, taking 50 mm.

[0076] ③. The stringer flexible die 3 is flush with the skin margin line of the panel at both ends, and the edges on both sides are the same as the corresponding edges of the adjacent stringer rigid die 2. The second stringer flexible die 3-1 at the bottom of the panel and the first stringer flexible die 3-1 on both sides are combined molds made of glass fiber reinforced plastic plates. The thickness of the bottom plate is 5 mm, and the thickness on both sides is 2 mm. For the first stringer flexible die 3-2 on both sides, an integral mold made of glass fiber pre-impregnated material + rubber is used and vulcanized through a soft mold forming die.

[0077] II. Design of the overall forming positioning method for the panel

[0078] According to the different characteristics of the middle and end parts of the U-shaped stiffened panel, the middle part of the stringer preform is positioned by the stringer positioning component, and the end part of the stringer preform is positioned by the positioning plate 9. The positioning combinations of the middle and end parts both meet the encapsulation requirements. After the positioning combination is completed, the overall forming die and the preform are encapsulated together in a vacuum bag, which is convenient for vacuum packaging and can avoid the risk of air leakage.

[0079] 2-A. Positioning method for the middle part of the stringer

[0080] The middle part of the stringer is positioned by the stringer positioning component. The stringer positioning component includes: a transverse positioning beam 5, positioning blocks 6, stringer limiting blocks 7, connection blocks 8 and connecting parts, as Figure 4 shown.

[0081] ①. The stringer limiting block 7 is designed at the segmented position of the stringer rigid die 2, and positions the adjacent two segments of the stringer rigid die 2 through both side surfaces at the same time. The two side surfaces cooperating with the stringer rigid die 2 are designed as trapezoids with a wider upper part and a narrower lower part, and the taper is 3°, which is consistent with both sides of the cavity of the stringer rigid die 2 at the corresponding position. A positioning pin is fixed at the mid-axis position of the top surface of the stringer limiting block 7. The positioning pin is a cylindrical pin with a length of 25 mm, and the axis of the positioning pin is parallel to the normal of the skin of the panel at this position.

[0082] After the stringer limiting block 7 is combined with the stringer rigid die 2, the gap between the bottom surface of the stringer limiting block 7 and the cavity of the stringer rigid die 2 is not less than the thickness of the equalizing plate 4, taking 3 mm. The top surface of the stringer limiting block 7 is 15 mm higher than the upper edges on both sides of the stringer rigid die 2. The width of the stringer limiting block 7 is taken as 30 mm.

[0083] ②. The transverse positioning beam 5 and the positioning blocks 6 on both sides are located on one side of the stringer limiting block 7, 1.5 mm away from the side surface of the stringer limiting block 7. The bottom surface of the transverse positioning beam 5 is 5 mm lower than the top surface of the stringer limiting block 7, and the top surface is 10 mm higher than the upper edge of the stringer rigid die 2. The width of the transverse positioning beam 5 is 30 mm and the thickness is 40 mm. A connection block 8 is fixed on the transverse positioning beam 5 above the stringer limiting block 7, and the mating surfaces with the positioning blocks are reserved at the opposite side and both ends of the bottom surface, and the rest of the area is chamfered.

[0084] The transverse positioning beam 5 spans across all stringer preforms and is positioned with the panel outer shape die 1 through the cylindrical pins on the positioning blocks 6 on both sides at both ends. The height of the positioning pins is 4 mm. The pin holes at both ends of the transverse positioning beam 5 are circular holes at one end and oblong holes at the other end.

[0085] ③. The connecting block 8 is located above the stringer limiting block 7 and is fixed or connected to the side surface of the transverse positioning beam 5. The connecting block 8 serves as a link for the transverse positioning beam 5 to position the stringer limiting block 7. After the connecting block 8 is fixed to the transverse positioning beam 5, the axis direction of its pin hole is along the normal direction of the skin in this area. After being combined with the stringer limiting block 7, the positioning of the stringer rigid die 2 is achieved.

[0086] The axis direction of the pin hole of the first connecting block 8-1 for positioning the first stringer rigid die 2-1 at the bottom of the panel is the same as the axis direction of the pins on the positioning blocks 6 on both sides. The first connecting block 8-1 is designed to be fixed and is directly fixed on the transverse positioning beam 5 to position the first stringer limiting block 7-1.

[0087] The axis direction of the pin hole of the second connecting block 8-2 for positioning the second stringer rigid die 2-2 on both sides of the panel is not the same as the axis direction of the pins on the positioning blocks 6 on both sides. The second connecting block 8-2 is designed to be detachable. The second connecting block 8-2 is first combined with the second stringer rigid die 2-2 and then connected and fixed to the transverse positioning beam 5.

[0088] 2-B. Positioning method for the end of the stringer

[0089] The end of the stringer is positioned by a positioning plate 9. The positioning plate 9 is fixed on the panel outer shape die 1. The length of the positioning plate 9 is the outer edge length of the outermost second rigid die 2-2, the width is 30 mm, and the thickness is not greater than the lower limit of the thickness of the panel skin area, which is 4.0 mm, and 4.5 mm is taken. The positioning plate 9 fixes a cylindrical pin at the midline position corresponding to the stringer rigid die 2. The length of the cylindrical pin is 6 mm, and a positioning hole is designed at the end of the corresponding stringer rigid die 2. The end of the stringer rigid die 2 is positioned and connected to the panel outer shape die 1 through the positioning pin.

[0090] Embodiment 2

[0091] Figure 1 For the U-shaped stiffened panel shown, the bottom surfaces of all the ribs are used as part of the skin and are integrated with the skin ply. The prepreg with a single-layer thickness of 0.125 mm is laid up and integrally formed by the autoclave process. This test piece is prepared by using the integral forming die for the U-shaped stiffened panel provided by the present invention. The specific operation method is as follows:

[0092] Figure 5Shown is the test piece b of the U-shaped stiffened panel, with dimensions of 3200mm * 720mm. The skin surface of the panel is flat, with 5 continuous stringer preforms b-1 to b-5, and 2 L-shaped stringer preforms on both sides. The width of each U-shaped stringer preform is 120mm, and the height is 40mm. The bottom surfaces of the U-shaped stringer preforms and the L-shaped stringer preforms are integrated with the skin ply as part of the skin, and the integral forming is carried out by the autoclave process. It is required that a 20mm margin is left around the panel during forming, and a 10mm margin is left at the upper edge of the stringer. The integral forming of this panel is prepared using the integral forming die for the U-shaped stiffened panel provided by the present invention, as Figure 6 shown below. The specific operation method is as follows:

[0093] I. Design the integral forming die for the U-shaped stiffened panel

[0094] 1-A. Design the outer shape die of the panel

[0095] The design of the outer shape die 1 of the panel needs to meet the requirements of the aerodynamic shape of the panel and serve as the positioning reference for all positioning devices. The outer shape die 1 of the panel is designed as a platform with a square steel frame structure. On both sides of the outer shape die 1, it extends 180mm along the part margin line, and the area about 100mm - 150mm inward from the edge of the outer shape die 1 is used to fix the positioning block 6.

[0096] At both ends of the outer shape die 1 of the panel, it extends 180mm along the part margin line, and 10 - 60mm outside the part margin line is used to fix the positioning plate 9.

[0097] Leakage prevention blocks are designed below the positions of the positioning block 6 and the positioning plate 9 on both corresponding sides of the outer shape die 1 of the panel, and the leakage prevention blocks are welded during die welding. It is required that the vacuum degree requirement for part forming is met within the wall panel sealing area including all positioning blocks 6 and positioning plates 9.

[0098] 1-B. Design the inner shape die of the panel

[0099] ①. Considering the need to ensure stringer pressurization and the surface, multiple stringer rigid dies 2 and multiple stringer flexible dies 3 are arranged alternately, that is, in an alternating arrangement form, Figure 5 As shown, the bottom surfaces of the U-shaped stringers of the U-shaped stiffened panel are all flat. Select the 1st, 3rd, and 5th U-shaped stringer preforms from the left side of the U-shaped stiffened panel to design the stringer rigid die 2, and the remaining adjacent U-shaped stringer preforms are designed with the first stringer flexible die 3-2. The L-shaped stringer preform areas on both sides also use the stringer flexible die 3.

[0100] ②. The longeron rigid die 2 is made of aluminum alloy LY12CZ, and its cross-section is designed as a U-shaped hollow structure, which is convenient for heat transfer and beneficial to the pressure uniformity. The maximum thickness is 6 mm. The outer surface of the longeron rigid die 2 is offset 0.1 mm inward according to the inner surface of the U-shaped longeron preform. The upper edges on both sides of the longeron rigid die 2 are 5 mm higher than the margin line of the longeron margin. The length of the longeron is 3200 mm, and it extends to be flush with the outer edge of the positioning plate 9 at both ends, with an extension of 60 mm at each end. The length of the longeron is 3320 mm. Each longeron rigid die 2 is divided into 3 segments. The length of the middle segment is 1100 mm, and the lengths of both ends are 1110 mm. After the longeron rigid die 2 is segmented, it is butt-jointed.

[0101] At the segmented position of the longeron rigid die 2, within the range of 20 mm on both sides of the cavity where the adjacent longeron rigid die 2 cooperates with the longeron limit block 7, it is designed as a trapezoid with a wider upper part and a narrower lower part, and the taper is 3°, which is consistent with the taper of the corresponding longeron limit block 7.

[0102] At the butt-jointed position of the segmented longeron rigid die 2, on the bottom surface of the inner cavity of the longeron rigid die at the butt-joint of the longeron rigid die segments, a pressure equalizing plate 4 is designed. The pressure equalizing plate 4 is made of LY12CZ aluminum plate with a thickness of 1.5 mm. The length is not greater than the distance between the tangent points of the lower R corners of the inner cavity of the longeron rigid die 2, taking 80 mm. The width is not less than 10 mm on each side compared to the width of the longeron limit block 7 at the corresponding position, taking 60 mm.

[0103] ③. The longeron flexible die 3 is flush with the margin line of the panel skin at both ends, and the edges on both sides are consistent with the edges at the corresponding positions of the adjacent longeron rigid die 2. The longeron flexible die 3 in the U-shaped longeron preform and the longeron flexible die 3 in the L-shaped longeron preforms on both sides are both combined molds made of fiberglass plates. The thickness of the bottom plate of the longeron flexible die 3 in the U-shaped longeron preform is 4 mm, and the thickness of the bottom plate of the longeron flexible die 3 in the L-shaped longeron preforms on both sides is 1.5 mm.

[0104] II. Design of the positioning method for the integral forming of the panel

[0105] Aiming at the different characteristics of the middle and end parts of the U-shaped stiffened panel, the middle part of the longeron preform is positioned by the longeron positioning assembly, and the end part of the longeron preform is positioned by the positioning plate 9. The positioning combinations of the middle and end parts both meet the encapsulation requirements. After the positioning combination is completed, the integral forming die and the preform are encapsulated together in a vacuum bag, which is convenient for vacuum packaging and can avoid the risk of air leakage.

[0106] 2-A. Positioning method for the middle part of the longeron

[0107] The middle part of the longeron is positioned by the longeron positioning assembly. The longeron positioning assembly includes: a transverse positioning beam 5, a positioning block 6, a longeron limit block 7, a connecting block 8 and connecting parts.

[0108] ①. The stringer limit block 7 is designed at the segmented position of the stringer rigid die 2, and positions the adjacent two segments of the stringer rigid die 2 simultaneously through two side surfaces. The two side surfaces that cooperate with the stringer rigid die 2 are designed as trapezoids with a wider upper part and a narrower lower part, and the taper is 3°, which is consistent with the two sides of the cavity of the stringer rigid die 2 at the corresponding position. A positioning pin is fixed at the central axis position of the top surface of the stringer limit block 7. The positioning pin is a cylindrical pin with a length of 20 mm, and the axis of the positioning pin is parallel to the normal of the skin of the panel at this position.

[0109] After the stringer limit block 7 and the stringer rigid die 2 are combined, the clearance between the bottom surface of the stringer limit block 7 and the cavity of the stringer rigid die 2 is not less than the thickness of the equalizing plate 4, taking 3 mm. The top surface of the stringer limit block 7 is 15 mm higher than the upper edges on both sides of the stringer rigid die 2. The width of the stringer limit block 7 is taken as 20 mm.

[0110] ②. The transverse positioning beam 5 and the positioning blocks 6 on both sides are located on one side of the stringer limit block 7, 1 mm away from the side surface of the stringer limit block 7. The bottom surface of the transverse positioning beam 5 is 5 mm lower than the top surface of the stringer limit block 7, and the top surface is 10 mm higher than the upper edge of the stringer rigid die 2. The width of the transverse positioning beam 5 is 20 mm, and the thickness is 30 mm. A connecting block 8 is fixed on the transverse positioning beam 5 above the stringer limit block 7. The mating surfaces with the positioning blocks are reserved at the opposite side and both ends of the bottom surface, and the rest of the area is chamfered.

[0111] The transverse positioning beam 5 spans across all stringer preforms and is positioned with the panel profile die 1 through the cylindrical pins on the positioning blocks 6 on both sides at both ends. The height of the positioning pin is 3 mm. One end of the pin holes at both ends of the transverse positioning beam 5 is opened as a round hole, and the other end is opened as a long round hole.

[0112] ③. The connecting block 8 is located above the stringer limit block 7 and is fixed or connected to the side surface of the transverse positioning beam 5. The connecting block 8 serves as a link for the transverse positioning beam 5 to position the stringer limit block 7. After the connecting block 8 is fixed to the transverse positioning beam 5, the axis direction of its pin hole is along the normal of the skin in this area. After being combined with the stringer limit block 7, it realizes the positioning of the stringer rigid die 2.

[0113] The axis directions of the pin holes of all the connecting blocks 8 that position the stringer rigid die 2 are consistent with the axis directions of the pins on the positioning blocks 6 on both sides. The connecting block 8 is designed as a fixed type and is directly fixed on the transverse positioning beam 5 to position the stringer limit block 7.

[0114] 2-B. Positioning method for the end of the stringer

[0115] The end of the longeron is positioned by the positioning plate 9. The positioning plate 9 is fixed on the skin outer shape die 1. The length of the positioning plate 9 is the outer edge length of the second outermost rigid die 2-2, the width is 30 mm, and the thickness is not greater than the lower limit of the thickness of the skin area of the panel, taking 3 mm. The positioning plate 9 fixes a cylindrical pin at the midline position corresponding to the longeron rigid die 2. The length of the cylindrical pin is 8 mm. A positioning hole is designed at the end of the corresponding longeron rigid die 2. The end of the longeron rigid die 2 is positioned and connected to the skin outer shape die 1 through the positioning pin.

[0116] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. An integral forming die for a U-shaped stiffened panel, which is used to position and fix a skin preform and a plurality of stringer preforms, and is characterized in that Including: A panel outer shape mold for positioning and installing the skin preform, wherein the inner surface of the panel outer shape mold is adapted to the designed outer shape of the skin preform; A stringer rigid mold disposed within the stringer preform, and the stringer rigid mold is positioned and connected to the panel outer shape mold; A stringer flexible mold disposed within the stringer preform, and a plurality of the stringer rigid molds and a plurality of the stringer flexible molds are arranged alternately; A stringer positioning assembly including a transverse positioning beam and a plurality of stringer limiting blocks, the transverse positioning beam is connected to the panel outer shape mold, the plurality of stringer limiting blocks are installed and connected to the transverse positioning beam, and the plurality of stringer limiting blocks are respectively and correspondingly clamped with the plurality of stringer rigid molds.

2. The integral forming die for the U-shaped stiffened wall panel according to claim 1, characterized in that, A plurality of stringer rigid molds are sequentially spliced end to end along the length direction of the stringer rigid mold, and inverted trapezoidal grooves are provided at both ends of the splicing part of the stringer rigid molds at both ends. The stringer limiting block is an inverted trapezoidal block, and the stringer limiting block is clamped in the inverted trapezoidal groove.

3. The integral forming die for the U-shaped stiffened wall panel according to claim 2, characterized in that, The taper of the inverted trapezoidal groove is 2° to 6°.

4. The integral forming die for the U-shaped stiffened wall panel according to claim 2, wherein The length of each stringer rigid mold is not greater than 1200 mm, and the splicing parts of the plurality of stringer rigid molds in the width direction are coplanar.

5. The integral forming die for the U-shaped stiffened wall panel according to claim 2, wherein It further includes a uniform pressing plate, and the uniform pressing plate is disposed at the splicing part of two adjacent stringer rigid molds.

6. The integral forming die for the U-shaped stiffened wall panel according to claim 1, characterized in that The stringer positioning assembly further includes a connecting block and a positioning block. The connecting block is connected to the transverse positioning beam, the stringer limiting block is connected to the connecting block, and positioning blocks are respectively provided at both ends of the transverse positioning beam. The positioning blocks are used for positioning and installing on the panel outer shape mold.

7. The integral forming die for the U-shaped stiffened wall panel according to claim 1, characterized in that, It further includes a positioning plate, and the positioning plates are respectively disposed at both ends of the panel outer shape mold. The end part of the stringer rigid mold is positioned and connected to the positioning plate.

8. The integral forming die for the U-shaped stiffened wall panel according to claim 7, characterized in that, It further includes a plurality of positioning pins. The positioning plate is provided with a plurality of pin holes, and the plurality of positioning pins are respectively and correspondingly positioned and connected to the plurality of stringer rigid molds and the plurality of pin holes.

9. The integral forming die for the U-shaped stiffened wall panel according to claim 1, characterized in that, The cross section of the stringer rigid mold is a U-shaped hollow structure, the thickness of the stringer rigid mold is not greater than 8 mm, and both ends of the stringer rigid mold are flush with the outer edge of the positioning plate.

10. The integral forming die for the U-shaped stiffened wall panel according to any one of claims 1-9, characterized in that, The material of the stringer rigid mold is steel or aluminum, and / or, the stringer flexible mold is a combination of rubber, fiber cloth and rubber, or fiberglass.

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