Crack arrest design method and crack arrest structure for bonding area of pressure-bearing wall plate structure
By setting crack-arresting notches in the bonding area between the stringer and the wall panel, and by setting gaskets and transition plates in the cap bottom plate, the crack-arresting area and notch shape were determined through finite element analysis. The method of using transition plates solved the problem of crack propagation in the bonding area between the stringer and the wall panel under compressive load, thus achieving structural stability and economy.
Patent Information
- Application Number
- CN202511609767.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-05
- Publication Date
- 2025-12-16
AI Technical Summary
In the prior art, the bonding area between the stringer and the wall panel is prone to crack propagation under compressive load, leading to premature structural failure. Existing methods, such as driving in rivets, are prone to collapse under excessive load and cannot effectively prevent crack propagation.
Crack arresting notches are set in the bonding area between the stringer and the wall panel, and gaskets and transition plates of the same material as the cap base plate are set at the notches. The crack arresting area and the shape of the notches are determined by finite element analysis. The transition plates are used to uniformly transfer the load and prevent crack propagation.
It effectively prevents crack propagation in the bonding area between the stringer and the wall panel, has a simple structure, low cost, is stable and reliable, does not affect the structural integrity, and avoids structural collapse under excessive load.
Smart Images
Figure CN121133984A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aircraft parts maintenance, specifically to a crack-stopping design method and structure for the bonding area of a pressure-bearing wall panel. Background Technology
[0002] Currently, the composite material wing or fuselage panel structures of large aircraft typically employ a stiffened panel design, with the basic load-bearing structure formed by the combination of panels and stringers. The stringers are usually connected to the panels using adhesive bonding; see appendix. Figure 1 and attached Figure 2 As shown, the girder has cap plates on both sides, which are bonded to the wall panels to form a bonding zone, thus greatly improving manufacturing efficiency and reducing weight. However, during load-bearing, especially under excessive compressive loads, the wall panels buckle, causing cracks in the bonding zone between the girder and the wall panels. These cracks propagate rapidly along the girder direction, eventually separating the girder from the wall panels completely. At this point, the girder cannot distribute the load on the wall panels, leading to premature structural failure and the inability to continue bearing loads after buckling. Current crack-prevention methods involve inserting rivets into the bonding zone between the girder and the wall panels. This method can prevent cracks caused by localized stress concentration. However, if the load is too large, the rivets will break, causing instantaneous structural failure and failing to reduce the localized load level. Summary of the Invention
[0003] In view of the shortcomings of the prior art described above, the technical problem to be solved by the present invention is to provide a crack-stopping design method and crack-stopping structure for the bonding area of a pressure-bearing wall panel structure, which can effectively solve the problem of crack propagation caused by excessive compressive load in the bonding area between the stringer and the wall panel. The structure is simple, low in cost, stable and reliable.
[0004] To achieve the above objectives, the present invention provides a crack-arresting design method for the bonding zone of a pressure-bearing wall panel structure. The pressure-bearing wall panel structure includes a stringer and wall panels, and the stringer has cap plates on both sides that are bonded to the wall panels. The crack-arresting design method includes the following steps:
[0005] S1. Determine the buckling deformation profile of the pressure-bearing wall panel structure under compressive load, determine the location of the minimum deformation along the length of the stringer, and determine the crack arrest area accordingly.
[0006] S2. A crack-stopping notch is set on the outer edge of the cap bottom plate in the crack-stopping area. The crack-stopping notch gradually decreases in size from the outside to the inside and the edge transitions smoothly.
[0007] S3. Use the same material as the cap base plate to make a gasket. The gasket is adapted to the shape of the crack arresting notch and has the same thickness. Place the gasket in the crack arresting notch and bond it to the wall panel. The edge of the gasket is not fixedly connected to the edge of the crack arresting notch.
[0008] S4. A layup is placed on the cap bottom plate in the crack arrest area as a transition strip. The transition strip completely covers the crack arrest gap and is bonded and fixed to the cap bottom plate.
[0009] Furthermore, in step S1, the buckling deformation profile of the pressure-bearing wall panel structure under compressive load is determined by the finite element analysis method.
[0010] Furthermore, in step S2, the crack-stopping notch is scalloped.
[0011] Furthermore, in step S2, the distance between the inner side of the crack-stopping notch and the inner side of the cap base plate is 0.1~0.5mm.
[0012] Furthermore, in step S2, the maximum dimension H of the crack-stopping notch in the length direction of the stringer is 3W~4W, where W is the width of the cap bottom plate.
[0013] Furthermore, in step S3, the mating distance between the edge of the gasket and the edge of the crack-stopping notch is 0.1-0.3 mm.
[0014] Further, in step S4, the front and rear edges of the transition strip plate extend out of the front and rear edges of the crack arresting notch along the length of the stringer, and the extension length L = P / (Fsu×W), where P is the structural strength of the transition strip plate, W is the width of the cap bottom plate, and Fsu is the shear strength of the adhesive film in the bonding area between the transition strip plate and the cap bottom plate.
[0015] Furthermore, in step S4, the front and rear edges of the transition strip plate extend out of the front and rear edges of the crack arresting notch along the length of the stringer, and the extension length L is greater than or equal to 20mm.
[0016] Furthermore, in step S4, the outer edge of the transition strip plate is flush with the outer edge of the cap bottom plate.
[0017] The present invention also provides a crack-stopping structure for the bonding area of a pressure-bearing wall panel structure, which is obtained by the crack-stopping design method described above.
[0018] As described above, the crack-arresting design method and crack-arresting structure of the present invention have the following beneficial effects:
[0019] It can effectively solve the problem of crack propagation caused by excessive compressive load in the bonding area between the stringer and the wall panel. Compared with the existing method of inserting rivets into the bonding area to prevent cracking, it has a simple structure, is easy to manufacture, has low cost, does not affect the normal use of the pressure-bearing wall panel structure, does not affect the structural integrity, and will not cause collapse when the load is too large, making it stable and reliable. Attached Figure Description
[0020] Figure 1This is a structural schematic diagram of a pressure-bearing wall panel structure.
[0021] Figure 2 This is a schematic cross-sectional view of a pressure-bearing wall panel structure.
[0022] Figure 3 This is a schematic diagram of the simulation of the pressure-bearing wall panel structure under buckling deformation in this invention.
[0023] Figure 4 This is a schematic diagram of the cap base plate in this invention.
[0024] Figure 5 This is a schematic diagram showing the arrangement of the gasket and transition plate in this invention.
[0025] Explanation of icon numbers:
[0026] 1-Wall panel, 2-Rack, 21-Cap base plate, 3-Crack arresting notch, 4-Shim, 5-Transition strip plate. Detailed Implementation
[0027] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.
[0028] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.
[0029] See Figures 1 to 5 This invention provides a crack-prevention design method for the bonding area of a pressure-bearing wall panel structure. The pressure-bearing wall panel structure includes a stringer 2 and a wall panel 1. The stringer 2 has cap plates 21 on both sides that are bonded to the wall panel 1, forming a bonding area at the cap plates 21. For ease of explanation, in this invention, the length direction of the stringer 2 is taken as the front-back direction, and the width direction as the left-right direction. The crack-prevention design method of this invention includes the following steps:
[0030] S1. Determine the buckling deformation profile of the pressure-bearing wall panel structure when it is subjected to compressive load, determine the location of the minimum buckling deformation along the length of the girder 2, and determine the crack arrest area accordingly.
[0031] For preferred design, see Figure 3 Finite element analysis was used to calculate and determine the buckling deformation profile of the pressure-bearing wall panel structure under compressive load, and to determine the locations of the peaks and troughs. During buckling deformation, multiple peaks and troughs will be formed along the length of the girder 2. The locations of the peaks and troughs are the locations of the maximum buckling deformation, and the areas between adjacent peaks and troughs are the locations of the minimum buckling deformation. The location of the maximum buckling deformation is where the initial crack will be generated, and the crack will propagate along the direction of the girder 2. An appropriate area before and after the location of the minimum buckling deformation was selected as the crack arresting area.
[0032] As a preferred design, the half-wave length is calculated using the following formula to accurately locate the position of minimum deformation based on the wave crest position, thereby determining the location of the crack arrest point. (Half-wave length) For a long strip plate like the cap base plate 21, which is constrained on both sides, and subjected to a compressive load N... x0 At that time, L x L is the half-wave length during buckling deformation. y D is the width of the long strip. 11 D 22 The stiffness matrix parameters of the composite laminate are calculated using classical laminate theory based on the structural ply and material properties. The calculation of the half-wavelength can be performed using existing methods; the specific principles will not be detailed here. After determining the location of the crack arrest point, a certain area before and after the crack arrest point along the length of stringer 2 is selected as the crack arrest region.
[0033] S2. A crack-stopping notch 3 is provided on the outer edge of the cap bottom plate 21 in the crack-stopping area. The crack-stopping notch 3 gradually decreases in size from the outside to the inside and the edge transitions smoothly.
[0034] As a preferred design, the innermost side of the crack-stopping notch 3 can also have an appropriate distance between it and the inner edge of the cap base plate 21, which is 0.1~0.5mm. The width of the cap base plate 21 of the stringer 2 is W, and the maximum dimension H of the crack-stopping notch 3 in the front-back direction is 3W~4W. The crack-stopping notch 3 is a front-back symmetrical structure, with its center line of symmetry along the left-right direction and passing through the crack-stopping point. The crack-stopping notch 3 is preferably scalloped, see [reference]. Figure 4 Furthermore, the edges of the crack-stopping notch 3, from front to back, are respectively an arc segment with radius W, an arc segment with radius W / 2, and an arc segment with radius W, and adjacent arc segments are tangent to each other. The front and rear arc segments are tangent to the outer edge of the cap base plate 21. The entire edge transition of the crack-stopping notch 3 is smooth and easy to process. In other embodiments, the crack-stopping notch 3 can also be semi-circular, semi-elliptical, or other suitable shapes.
[0035] S3. A gasket 4 is made using the same material as the cap base plate 21. The gasket 4 is shaped to match the crack arresting notch 3 and has the same thickness. The gasket 4 is placed in the crack arresting notch 3 and bonded to the wall plate 1. The edge of the gasket 4 is not fixedly connected to the edge of the crack arresting notch 3, and the mating gap between the two is 0.1-0.3mm. Preferably, the outer edge of the gasket 4 is flush with the outer edge of the cap base plate 21, that is, the shape of the gasket 4 is consistent with the crack arresting notch 3. The purpose of setting the gasket 4 is to fill the original part that was removed from the cap base plate 21, so that the outer edge of the stringer 2 returns to its original configuration. However, this part is independent of the stringer 2, and the internal stress of the stringer 2 during deformation will not be directly transmitted to the gasket 4.
[0036] S4. A layup is placed on the cap bottom plate 21 in the crack arresting area as a transition strip plate 5. The transition strip plate 5 completely covers the crack arresting notch 3 and is bonded and fixed to the cap bottom plate 21.
[0037] For preferred design, see Figure 5 The transition strip 5 extends from the front and rear edges of the crack arresting notch 3 along the length of the stringer 2, with an extension length L = P / (Fsu×W), where P is the structural strength of the transition strip 5, determined by its material and layup configuration. If the configuration of the transition strip 5 is consistent with that of the stringer 2, then the value of P is consistent with the structural strength of the stringer 2. Fsu is the shear strength of the adhesive film in the bonding area between the transition strip 5 and the cap bottom plate 21. Preferably, the length L is at least 20 mm. The outer edge of the transition strip 5 is flush with the outer edge of the cap bottom plate 21, and the inner edge is flush with the inner edge of the cap bottom plate 21, meaning the width of the transition strip 5 is consistent with that of the cap bottom plate 21. The thickness of the transition strip 5 is consistent with that of the cap bottom plate 21. The purpose of setting the transition strip 5 is to evenly transfer the load originally pressing on the stringer 2 to the stringer 2 and the gasket 4 through the transition strip 5.
[0038] This invention also provides a crack-stopping structure for the bonding area of a pressure-bearing wall panel structure. The pressure-bearing wall panel structure includes a stringer 2 and a wall panel 1. The crack-stopping structure is obtained through the aforementioned crack-stopping design method, namely, the crack-stopping structure includes a crack-stopping notch 3 opened on the outer side of the cap bottom plate 21, a gasket 4 disposed in the crack-stopping notch 3, and a transition strip plate 5 covering the gasket 4. Multiple crack-stopping structures can be provided along the length of a stringer 2 according to its buckling deformation profile under compressive load, and crack-stopping structures are provided on both sides of the cap bottom plate 21 at the minimum deformation position of the stringer 2, with the crack-stopping structures on the two cap bottom plates 21 maintaining left-right symmetry. The pressure-bearing wall panel structure of this invention is preferably a stiffened wall panel 1 for a large aircraft composite wing or fuselage, wherein the wall panel 1 is a composite material layer.
[0039] The working principle of the crack-arresting structure obtained by this invention is as follows: During normal operation, the load on the stringer 2 is transferred from the transition plate 5 to the cap plate 21 and the gasket 4 at the crack-arresting structure. The cap plate 21 and the wall panel 1 in the remaining bonded area of the stringer 2 (the area outside the crack-arresting notch 3) continue to bear the load as a whole structure. When the buckling deformation does not reach a severe state, the load on the stringer 2 can be smoothly transferred through the transition plate 5 at the crack-arresting point without affecting the structural integrity. When faced with excessive compressive load, the wall panel 1 buckles. When the crack occurs at the location of maximum buckling deformation and begins to propagate towards the crack arrest point, the crack cannot continue to propagate through the cap bottom plate 21 because the portion of the cap bottom plate 21 at the crack arrest point is removed. As a result, the load of the crack can only be transmitted from the transition band plate 5 above the gasket 4. However, excessive load will cause the bonding between the transition band plate 5 and the cap bottom plate 21 to break. Therefore, the stress transmission inside the cap bottom plate 21 stops at the gasket 4, and the stress cannot be transmitted to the next buckling deformation peak area, thus causing the crack to stop at the crack arrest point.
[0040] As can be seen from the above, the crack-stopping design method and crack-stopping structure of the present invention have the following beneficial effects:
[0041] It can effectively solve the problem of crack propagation caused by excessive compressive load in the bonding area between the girder 2 and the wall panel 1. Compared with the existing method of inserting rivets into the bonding area to prevent cracking, it has a simple structure, is easy to manufacture, has low cost, does not affect the normal use of the pressure-bearing wall panel structure, does not affect the structural integrity, and will not cause collapse when the load is too large, making it stable and reliable.
[0042] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.
[0043] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method for designing crack prevention in the bonding zone of a pressure-bearing wall panel structure, wherein the pressure-bearing wall panel structure includes a stringer (2) and a wall panel (1), and the stringer (2) has cap plates (21) on both sides that are bonded to the wall panel (1), characterized in that: The crack arrest design method includes the following steps: S1. Determine the buckling deformation profile of the pressure-bearing wall panel structure when bearing compressive load, determine the location of the minimum deformation in the length direction of the stringer (2), and determine the crack arrest area accordingly. S2. A crack-stopping notch (3) is set on the outer edge of the cap bottom plate (21) in the crack-stopping area. The crack-stopping notch (3) gradually decreases in size from the outside to the inside and the edge transitions smoothly. S3. Use the same material as the cap base plate (21) to make a gasket (4). The gasket (4) is compatible with the shape of the crack-stopping notch (3) and has the same thickness. Place the gasket (4) in the crack-stopping notch (3) and bond it to the wall plate (1). The edge of the gasket (4) is not fixedly connected to the edge of the crack-stopping notch (3). S4. A layup is placed on the cap bottom plate (21) in the crack arrest area as a transition strip plate (5). The transition strip plate (5) completely covers the crack arrest notch (3) and is bonded and fixed to the cap bottom plate (21).
2. The crack arrest design method according to claim 1, characterized in that: In step S1, the buckling deformation profile of the pressure-bearing wall panel structure under compressive load is determined by the finite element analysis method.
3. The crack arrest design method according to claim 1, characterized in that: In step S2, the crack-stopping notch (3) is scallop-shaped.
4. The crack arrest design method according to claim 1, characterized in that: In step S2, the distance between the inner side of the crack-stopping notch (3) and the inner side of the cap bottom plate (21) is 0.1~0.5mm.
5. The crack arrest design method according to claim 1, characterized in that: In step S2, the maximum dimension H of the crack-stopping notch (3) in the length direction of the stringer (2) is 3W~4W, where W is the width of the cap bottom plate (21).
6. The crack arrest design method according to claim 1, characterized in that: In step S3, the mating distance between the edge of the gasket (4) and the edge of the crack-stopping notch (3) is 0.1-0.3 mm.
7. The crack arrest design method according to claim 1, characterized in that: In step S4, the front and rear edges of the transition strip plate (5) extend out of the front and rear edges of the crack arresting notch (3) along the length direction of the stringer (2), and the extension length L = P / (Fsu×W), where P is the structural strength of the transition strip plate (5), W is the width of the cap bottom plate (21), and Fsu is the shear strength of the adhesive film in the bonding area between the transition strip plate (5) and the cap bottom plate (21).
8. The crack arrest design method according to claim 1, characterized in that: In step S4, the front and rear edges of the transition strip plate (5) extend out of the front and rear edges of the crack arresting notch (3) along the length of the stringer (2), and the extension length L is greater than or equal to 20mm.
9. The crack arrest design method according to claim 1 or 4, characterized in that: In step S4, the outer edge of the transition strip plate (5) is flush with the outer edge of the cap bottom plate (21).
10. A crack-arresting structure for the bonding zone of a pressure-bearing wall panel, characterized in that: The crack-arresting structure is obtained by the crack-arresting design method according to any one of claims 1 to 9.