Strength analysis method of carbon fiber laminated plate and foam sandwich structure rivet-bonded joint

Abstract

The present application provides a kind of carbon fiber laminated plate and foam sandwich structure glue rivet joint strength analysis method, including predetermined test condition to test specimen is carried out shear strength test, based on test condition establishes the test finite element model corresponding to test specimen, runs test finite element model and carries out simulation calculation etc.Steps.The present application reveals the difference of carrying capacity and failure mode of glue rivet joint in carbon fiber laminated plate and foam sandwich structure of glue rivet connection under shear and pull load by test and simulation combined analysis, establishes high-precision finite element model, can accurately predict glue rivet joint performance, optimize key design parameters provide possibility, break through the limitation of existing theoretical model or simplified model.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of structural strength simulation and analysis, in particular to a carbon fiber laminate and foam sandwich structure adhesive-riveted joint strength analysis method. BACKGROUND

[0002] The content of this part only provides background information related to the present application, which may not constitute prior art.

[0003] With the development of rail transit equipment towards high speed and light weight, carbon fiber laminates made of carbon fiber composite materials have been widely used in main load-bearing structures such as car bodies and bogies due to their high specific strength, high specific stiffness and excellent fatigue resistance. In order to further improve the bending stiffness of these main load-bearing structures and control the weight, the use of composite structures composed of carbon fiber laminates and foam sandwich structures has become the mainstream design. In such composite structures, the connection between the carbon fiber laminate and the foam sandwich structure is a key weak link that affects the overall reliability of the structure.

[0004] Due to the characteristics of carbon fiber composite materials, the carbon fiber laminate and the foam sandwich structure can only be connected by adhesive bonding, mechanical connection or adhesive-riveted connection combining both. Among them, adhesive-riveted connection combines the advantages of uniform stress distribution of adhesive bonding and high reliability of mechanical connection, and becomes an effective connection solution. However, in adhesive-riveted connection, the strength performance of the adhesive-riveted joint is affected by the coupling of multiple parameters such as adhesive layer thickness, rivet diameter, overlap area and sandwich thickness, and its mechanical behavior and failure mode are extremely complex.

[0005] Currently, there are many challenges in the strength analysis of such adhesive-riveted joints: first, there is a lack of systematic experimental research and accurate evaluation methods for the load-bearing capacity of adhesive-riveted joints under complex load conditions such as shear, tension and their coupling; second, existing theoretical models or simplified finite element models are difficult to accurately simulate the progressive damage process of adhesive-riveted joints, especially in predicting the anisotropic failure of carbon fiber laminates, the compression shear behavior of foam sandwich structures and the interfacial fracture of adhesive layers, resulting in conservative design or potential risks; third, due to the lack of high-precision simulation models that have been fully verified, it is difficult to carry out effective parameterized design and optimization, which restricts the further improvement of adhesive-riveted joint performance and its standardized and reliable application in major equipment. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a carbon fiber laminate and foam sandwich structure adhesive-riveted joint strength analysis method to overcome the technical problem that existing methods are difficult to accurately analyze the strength of the adhesive-riveted joint formed after the carbon fiber laminate and foam sandwich structure are connected.

[0007] The object of the present application is achieved by the following technical solutions.

[0008] In a first aspect, the present application provides a method for analyzing the strength of a carbon fiber laminate and foam sandwich structure adhesive-riveted joint, comprising the following steps:

[0009] Performing a shear strength test on a test specimen under predetermined test conditions to obtain a failure mode corresponding to the test specimen and test load-displacement data; the test specimen comprises a carbon fiber laminate and a foam sandwich structure, and the carbon fiber laminate and the foam sandwich structure are connected by a glue layer and a rivet;

[0010] Based on the test conditions, a test finite element model corresponding to the test specimen is established; in the test finite element model, a user-defined subroutine is used to simulate the anisotropic progressive damage behavior of the carbon fiber laminate, the three-dimensional Hashin criterion is used as the failure criterion of the carbon fiber laminate, and the energy dissipation controlled linear degradation method is used to describe the damage evolution process of the carbon fiber laminate; the foam core in the foam sandwich structure is simulated by a compressible foam model; the glue layer is modeled by a three-dimensional cohesive element based on the cohesive theory, the initial damage criterion is a quadratic criterion based on the nominal stress, and the damage evolution process is described by the Benzeggagh-Kenane criterion;

[0011] Running the test finite element model to perform simulation calculation to obtain simulation load-displacement data corresponding to the test specimen; comparing the simulation load-displacement data with the test load-displacement data to verify the accuracy of the simulation calculation results.

[0012] Optionally, the user-defined subroutine is VUMAT; and in the test finite element model, the glue layer is bound by Tie constraints between the adjacent carbon fiber laminate and foam sandwich structure.

[0013] Optionally, the method for analyzing the strength of the carbon fiber laminate and foam sandwich structure adhesive-riveted joint further comprises the following steps:

[0014] Establishing a global finite element model corresponding to an actual engineering structure, and intercepting a local area containing the adhesive-riveted joint in the global finite element model as a main finite element model; the adhesive-riveted joint in the global finite element model is simplified;

[0015] Refining the modeling of the main finite element model by using the method for establishing the test finite element model to obtain a sub finite element model;

[0016] Running the global finite element model and the sub finite element model to perform simulation calculation to obtain displacement contour maps and stress contour maps in each direction corresponding to the global finite element model, and displacement contour maps and stress contour maps in each direction corresponding to the sub finite element model;

[0017] The displacement nephogram and the stress nephogram in each direction of the whole finite element model and the sub finite element model are compared and analyzed to verify the accuracy of the sub finite element model.

[0018] Optionally, in the sub finite element model, the carbon fiber laminated plate, the foam sandwich structure, the rivet and the adhesive layer contained therein are modeled by using solid elements; the boundary constraint of the sub finite element model is inherited from the displacement information extracted from the whole finite element model.

[0019] Optionally, the simplified modeling specifically is that the carbon fiber laminated plate is simulated by using a shell element, the foam sandwich structure is simulated by using a solid element, the rivet is simulated by using a beam element and a rigid element, and the adhesive layer is not modeled separately.

[0020] Optionally, the test specimen includes a first test specimen, a second test specimen and a third test specimen; the thickness of the foam sandwich structure in the first test specimen is less than the thickness of the foam sandwich structure in the second test specimen; the thickness of the foam sandwich structure in the second test specimen is equal to the thickness of the foam sandwich structure in the third test specimen.

[0021] Optionally, the shear strength test on the test specimen is performed by using an MTS tension-torsion testing machine.

[0022] In the shear strength test on the first test specimen, the testing machine applies a plane shear load to the first test specimen.

[0023] In the shear strength test on the second test specimen, the testing machine applies a plane shear load to the second test specimen.

[0024] In the shear strength test on the third test specimen, the testing machine applies a vertical pulling load to the third test specimen.

[0025] Optionally, in the test finite element model, the carbon fiber laminated plate, the foam sandwich structure and the rivet in the test specimen are modeled by using three-dimensional solid elements; the boundary condition of the test finite element model is set with reference to the shear strength test.

[0026] In a second aspect, the present application provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the strength analysis method of the carbon fiber laminated plate and the foam sandwich structure adhesive-riveted joint when executing the computer program.

[0027] In a third aspect, the present application provides a readable storage medium, which stores a computer program, and the computer program implements the strength analysis method of the carbon fiber laminated plate and the foam sandwich structure adhesive-riveted joint when executed by a processor.

[0028] The technical scheme of the embodiment of the present application has at least the following advantages and beneficial effects:

[0029] The present application discloses a strength analysis method for a carbon fiber laminated plate and a foam sandwich structure adhesive rivet joint, which is characterized by the following steps: (1) constructing a high-precision test finite element model corresponding to the test specimen based on the test conditions; (2) testing three test specimens by shear strength test; (3) revealing the bearing capacity difference and failure mode of the adhesive rivet joint in the carbon fiber laminated plate and the foam sandwich structure under shear and pull-off load; (4) quantifying the influence of the foam sandwich structure with different thicknesses on the residual bearing capacity; and (5) solving the problem of performance evaluation deviation caused by load condition difference in traditional design. The method can accurately predict the failure risk of the adhesive rivet joint under complex service conditions, and significantly improve the reliability and safety of such lightweight composite structures.

[0030] The present application discloses a strength analysis method for a carbon fiber laminated plate and a foam sandwich structure adhesive rivet joint, which is characterized by the following steps: (1) constructing a high-precision test finite element model corresponding to the test specimen based on the test conditions; (2) testing three test specimens by shear strength test; (3) revealing the bearing capacity difference and failure mode of the adhesive rivet joint in the carbon fiber laminated plate and the foam sandwich structure under shear and pull-off load; (4) quantifying the influence of the foam sandwich structure with different thicknesses on the residual bearing capacity; and (5) solving the problem of performance evaluation deviation caused by load condition difference in traditional design. The method can accurately predict the failure risk of the adhesive rivet joint under complex service conditions, and significantly improve the reliability and safety of such lightweight composite structures.

[0031] The present application discloses a strength analysis method for a carbon fiber laminated plate and a foam sandwich structure adhesive rivet joint, which is characterized by the following steps: (1) constructing a high-precision test finite element model corresponding to the test specimen based on the test conditions; (2) testing three test specimens by shear strength test; (3) revealing the bearing capacity difference and failure mode of the adhesive rivet joint in the carbon fiber laminated plate and the foam sandwich structure under shear and pull-off load; (4) quantifying the influence of the foam sandwich structure with different thicknesses on the residual bearing capacity; and (5) solving the problem of performance evaluation deviation caused by load condition difference in traditional design. The method can accurately predict the failure risk of the adhesive rivet joint under complex service conditions, and significantly improve the reliability and safety of such lightweight composite structures. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The flowchart of the strength analysis method for a carbon fiber laminated plate and a foam sandwich structure adhesive rivet joint provided by the embodiment of the present application is shown in the figure.

[0033] Figure 2 The three-dimensional geometric model diagram of the first test specimen provided by the embodiment of the present application is shown in the figure.

[0034] Figure 3 The size diagram of the first test specimen is shown in the figure, wherein, Figure 3 (a) is the front view of the first test specimen; Figure 3 (b) is the top view of the first test specimen;

[0035] Figure 4 The three-dimensional geometric model diagram of the second test specimen provided by the embodiment of the present application is shown in the figure.

[0036] Figure 5 The size diagram of the second test specimen is shown in the figure, wherein, Figure 5 (a) is the front view of the second test specimen; Figure 5 (b) is the side view of the second test specimen,Figure 5 (c) is a plan view of the second test piece;

[0037] Figure 6 a three-dimensional geometric model diagram of a third test piece provided for an embodiment of the present application;

[0038] Figure 7 a size diagram of the third test piece; wherein, Figure 7 (a) is a front view of the third test piece; Figure 7 (b) is a side view of the third test piece, Figure 7 (c) is a plan view of the third test piece;

[0039] Figure 8 a test finite element model diagram corresponding to the first test piece;

[0040] Figure 9 a boundary condition diagram of the test finite element model corresponding to the first test piece;

[0041] Figure 10 a test finite element model diagram corresponding to the second test piece;

[0042] Figure 11 a boundary condition diagram of the test finite element model corresponding to the second test piece;

[0043] Figure 12 a test finite element model diagram corresponding to the third test piece;

[0044] Figure 13 a boundary condition diagram of the test finite element model corresponding to the third test piece;

[0045] Figure 14 a load-displacement curve comparison diagram of the first test piece under test and simulation analysis conditions;

[0046] Figure 15 a load-displacement curve comparison diagram of the second test piece under test and simulation analysis conditions;

[0047] Figure 16 a load-displacement curve comparison diagram of the third test piece under test and simulation analysis conditions;

[0048] Figure 17 a whole finite element model diagram of a certain actual engineering structure provided for an embodiment of the present application;

[0049] Figure 18 is Figure 17 a main finite element model diagram in a whole finite element model of a certain actual engineering structure shown;

[0050] Figure 19 a sub finite element model diagram corresponding to the main finite element model;

[0051] Figure 20 a displacement contour corresponding to the main finite element model;

[0052] Figure 21 a displacement contour corresponding to the sub finite element model.

[0053] Legend: 100 - first test specimen, 200 - second test specimen, 300 - third test specimen, 10 - carbon fiber laminate, 20 - foam sandwich structure, 30 - rivet, 40 - glue layer. DETAILED DESCRIPTION

[0054] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below in conjunction with specific embodiments. The same reference signs in the drawings represent the same components. It should be noted that the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0055] Compared with the embodiments shown in the drawings, the feasible implementation schemes within the protection scope of the present application can have fewer components, have other components not shown in the drawings, have different components, have differently arranged components or differently connected components, etc. In addition, two or more components in the drawings can be implemented in a single component, or a single component shown in the drawings can be implemented as multiple separate components.

[0056] Embodiment 1

[0057] Embodiment 1 of the present application provides a strength analysis method of a carbon fiber laminate 10 and foam sandwich structure 20 glue-rivet joint. The foam sandwich structure 20 described in the present application can also be understood as a foam sandwich plate. Figure 1 A flowchart schematically shows the strength analysis method provided by Embodiment 1 of the present application.

[0058] As shown in Figure 1 According to the embodiment of the present application, the strength analysis method can include the following steps:

[0059] Step S100. Preparing a test specimen.

[0060] Specifically, the test specimen described in the embodiment of the present application includes a carbon fiber laminate 10 and a foam sandwich structure 20. The carbon fiber laminate 10 and the foam sandwich structure 20 are connected by a glue layer 40 and a rivet 30. The glue layer 40 and the rivet 30 together constitute a glue-rivet joint.

[0061] In order to simplify the structure of the test specimen as much as possible and cover the typical working conditions of such composite structures, the present application preliminarily designs three typical test specimens containing the glue-riveted joints, which are a first test specimen 100, a second test specimen 200 and a third test specimen 300. Among them, the thickness of the foam core structure 20 in the first test specimen 100 is much smaller than that of the foam core structure 20 in the second test specimen 200 and the third test specimen 300, and the thickness of the foam core structure 20 in the second test specimen 200 and the third test specimen 300 is equal.

[0062] The first test specimen 100 is mainly used to simulate the composite structure formed after the thin foam core structure 20 is glued and riveted with the carbon fiber laminated plate 10. As shown in Figure 2 the foam core structure 20 in the first test specimen 100 is overlapped on one side of the carbon fiber composite plate of the test specimen in the length direction of the foam core structure 20, and the two are mechanically fixed by the rivet 30 and further enhance the strength of the connection by the glue layer 40 to ensure the high strength and light weight characteristics of the composite structure and provide additional support through the foam core structure 20. This design not only enhances the overall carrying capacity of the composite structure, but also effectively reduces the self-weight of the test specimen, which is suitable for use in light-weight high-strength structures.

[0063] Among them, the size parameters of the foam core structure 20 and the carbon fiber laminated plate 10 in the first test specimen 100 can refer to Figure 3 . Specifically, the length and width of the foam core structure 20 of the first test specimen 100 can be 120mm and 33mm, respectively, and the thickness is 4mm; further, the foam core material thickness of the foam core structure 20 is 2.8mm, and the thickness of the carbon fiber panel on both sides of the foam core material is 0.6mm; the length and width of the carbon fiber laminated plate 10 of the first test specimen 100 can be 120mm and 33mm, respectively, and the thickness is 2mm. In the subsequent shear strength test of the first test specimen 100, the load applied to the first test specimen 100 is the plane shear load.

[0064] The second test specimen 200 is mainly used to simulate the composite structure formed after the thick foam core structure 20 is glued and riveted with the carbon fiber laminated plate 10. As shown in Figure 4As shown, the foam sandwich structure 20 in the second test piece 200 is located at the bottom of the carbon fiber composite plate and is basically a cube. The foam sandwich structure 20 is provided with connecting holes at four corners to facilitate connection with the clamps of the testing machine when the shear strength test is carried out. The carbon fiber laminated plate 10 of the second test piece 200 is borne on the foam sandwich structure 20 of the test piece, and one side of the carbon fiber laminated plate 10 in the length direction of the carbon fiber laminated plate 10 is flush with one side of the foam sandwich structure 20, and the other side of the carbon fiber laminated plate 10 in the length direction of the carbon fiber laminated plate 10 protrudes from the foam sandwich structure 20. Among them, the top center of the foam sandwich structure 20 of the second test piece 200 is connected to the carbon fiber laminated plate 10 by adhesive riveting. By using a thicker foam sandwich structure 20, the tensile strength and stiffness of the composite structure can be effectively improved, and the entire composite structure exhibits the characteristics of high stiffness and light weight. The design purpose of the second test piece 200 is to test the performance of the adhesive rivet joint in the thick foam sandwich structure 20 under the action of the plane shear load. By using a high-strength carbon fiber laminated plate 10, the foam sandwich structure 20 can effectively bear the plane shear load from the outside, and the foam core material in the foam sandwich structure 20 provides support and absorbs part of the energy. In the subsequent shear strength test, the second test piece 200 will bear the plane shear load, and the failure mode under the limit plane shear load will be analyzed.

[0065] Among them, the size parameters of the foam sandwich structure 20 and the carbon fiber laminated plate 10 in the second test piece 200 can refer to Figure 5 As shown. Specifically, the length and width of the foam sandwich structure 20 of the second test piece 200 can be 80mm, 80mm, and the thickness can be 44mm; further, the thickness of the foam core material of the foam sandwich structure 20 can be 40mm, and the thickness of the carbon fiber panel on both sides of the foam core material can be 2mm; the length and width of the carbon fiber laminated plate 10 of the second test piece 200 can be 140mm, 20mm, and the thickness can be 2mm.

[0066] The third test piece 300 is similar in structure to the second test piece 200 and is also used to simulate the composite structure formed after the thick foam sandwich structure 20 and the carbon fiber laminated plate 10 are connected by adhesive riveting. Different from the second test piece 200, since in the subsequent shear strength test of the third test piece 300, the loading direction of the load is vertical pulling, in order to study the anti-pulling performance of the thick foam sandwich structure 20 under the vertical pulling load. Therefore, in order to facilitate the loading of the vertical pulling load, as Figure 6 As shown, both sides of the carbon fiber laminated plate 10 in the length direction of the carbon fiber laminated plate 10 protrude from the foam sandwich structure 20.

[0067] Among them, the size parameters of the foam sandwich structure 20 and the carbon fiber laminated plate 10 in the third test piece 300 can refer to Figure 7The length and width of the foam sandwich structure 20 of the third test piece 300 can be 80 mm and 80 mm respectively, and the thickness can be 44 mm. Further, the thickness of the foam core material of the foam sandwich structure 20 can be 2.8 mm, and the thickness of the carbon fiber panel on both sides of the foam core material can be 0.6 mm. The length and width of the carbon fiber laminate sheet 10 of the third test piece 300 can be 140 mm and 20 mm respectively, and the thickness can be 2 mm.

[0068] Step S200. Perform a shear strength test.

[0069] After the test piece is prepared based on step S100, a shear strength test is performed on the test piece under predetermined test conditions to obtain the failure mode corresponding to the test piece and the test load-displacement data.

[0070] The shear strength test of the three test pieces described above can be performed using an MTS tension-torsion testing machine, and the test conditions corresponding to each test piece are different.

[0071] Specifically, in the shear strength test of the first test piece 100, the test conditions corresponding to the first test piece 100 are that the foam sandwich structure 20 in the first test piece 100 is clamped by the upper end clamp of the testing machine, and the carbon fiber laminate sheet 10 in the first test piece 100 is clamped by the lower end clamp of the testing machine. The lower end clamp of the testing machine stretches the first test piece 100 at a constant rate, and the loading rate of the testing machine can be set to 2 mm / min to apply a plane shear load to the first test piece 100 until the first test piece 100 fails. The failure mode of the first test piece 100 is recorded during the test to analyze the failure mode of the first test piece 100, and the load-displacement curve corresponding to the first test piece 100 is derived from the testing machine after the test to obtain the test load-displacement data corresponding to the first test piece 100.

[0072] Referring to Figure 14 , the first test piece 100 shows elastic deformation in the initial loading stage, and the load approximately linearly increases, indicating that the adhesive layer 40 mainly bears the load at this time. With the increase of the load, the adhesive layer 40 reaches the ultimate bearing capacity and instantaneously breaks, and the load sharply decreases. After the adhesive layer 40 breaks, the rivet 30 begins to bear the load, and the foam sandwich structure 20 is subjected to the extrusion action of the rivet 30. With the continuation of the loading, the foam sandwich structure 20 gradually deforms plastically, and the load gradually decreases, and finally the first test piece 100 completely fails.

[0073] In the shear strength test of the second test piece 200, the test conditions corresponding to the second test piece 200 are that one end of the carbon fiber laminate 10 in the second test piece 200 protruding from the foam sandwich structure 20 is clamped by the upper end clamp of the testing machine, and the foam sandwich structure 20 in the second test piece 200 is connected to the lower end clamp of the testing machine by bolts; the lower end clamp of the testing machine stretches the second test piece at a constant rate, and the loading rate of the testing machine can also be set to 2 mm / min to apply a plane shear load to the second test piece 200 until the second test piece 200 fails. The failure mode of the second test piece 200 is recorded during the test to analyze the failure mode of the second test piece 200, and the load-displacement curve corresponding to the second test piece 200 is derived from the testing machine after the test to obtain the test load-displacement data corresponding to the second test piece 200.

[0074] Referring to Figure 15 , the second test piece 200 has similar mechanical characteristics as the first test piece 100 before the adhesive layer 40 fails, the initial load rises linearly, which shows that the adhesive layer 40 dominates the bonding strength, and after reaching the limit load, the adhesive layer 40 breaks and enters the second stage, and the rivet 30 begins to bear the load. Because the carbon fiber laminate 10 of the second test piece 200 is thinner than its own foam sandwich structure 20, the extrusion of the rivet 30 causes the carbon fiber laminate 10 to break, which eventually leads to the failure of the second test piece 200.

[0075] In the shear strength test of the third test piece 300, the test conditions corresponding to the third test piece 300 are that both ends of the carbon fiber laminate 10 in the third test piece 300 protruding from the foam sandwich structure 20 are clamped by the upper end clamp of the testing machine, and the foam sandwich structure 20 in the third test piece 300 is connected to the lower end clamp of the testing machine by bolts; the lower end clamp of the testing machine stretches the third test piece at a constant rate, and the loading rate of the testing machine can also be set to 2 mm / min to apply a vertical pulling load to the third test piece 300 until the third test piece 300 fails. The failure mode of the third test piece 300 is recorded during the test to analyze the failure mode of the third test piece 300, and the load-displacement curve corresponding to the third test piece 300 is derived from the testing machine after the test to obtain the test load-displacement data corresponding to the third test piece 300.

[0076] Referring to Figure 16 , the load-displacement curve of the third test piece 300 is basically the same as the first test piece 100 and the second test piece 200, and also shows a two-stage bearing trend. The difference is that the third test piece 300 bears a vertical pulling load, so that the adhesive layer 40 fails brittlely under a lower load, and the overall limit bearing level is also significantly lower.

[0077] It is worth noting that by adopting the shear strength test to test the three test specimens, the differences in bearing capacity and failure modes of the adhesive rivet joints in the carbon fiber laminated plate 10 and the foam sandwich structure 20 of the adhesive rivet connection under shear and pull-off load are revealed, the influence of the foam sandwich structure 20 with different thicknesses on the residual bearing capacity is quantified, and the deviation problem of structural performance evaluation caused by the difference in load conditions in the traditional design is solved. The method can accurately predict the failure risk of the adhesive rivet joint under complex service conditions, and significantly improve the reliability and safety of such lightweight composite structures.

[0078] Step S300. Establish a test finite element model corresponding to the test specimen;

[0079] Based on the test conditions corresponding to the test specimen in step S200, a corresponding test finite element model is established in ABAQUS based on the three-dimensional geometric model of each test specimen, and the carbon fiber laminated plate 10, the foam sandwich structure 20, the rivet 30 and the adhesive layer 40 in the test specimen are modeled respectively.

[0080] In the test finite element model, the carbon fiber laminated plate 10, the foam sandwich structure 20 and the rivet 30 in the test specimen are modeled by using three-dimensional solid elements (C3D8R), and the boundary conditions of the test finite element model are set with reference to the shear strength test in step S200. The elastic constants and strength parameters of the carbon fiber laminated plate 10 can be obtained by corresponding tests, and the anisotropic progressive damage behavior of the carbon fiber laminated plate 10 is simulated by using a user-defined subroutine VUMAT. The three-dimensional Hashin criterion is used as the failure criterion of the carbon fiber laminated plate 10, and the damage evolution process of the carbon fiber laminated plate 10 is described by combining the energy dissipation control linear degradation method.

[0081] The foam core material in the foam sandwich structure 20 can be simulated by using the built-in compressible foam model in ABAQUS to fully consider its nonlinear compression response and shear damage mechanism. The adhesive layer 40 is modeled based on the cohesive force theory by using three-dimensional cohesive elements (COH3D8R). The initial damage criterion adopts a quadratic criterion based on the nominal stress, and the damage evolution process is described by using the Benzeggagh-Kenane (B-K) criterion, which can reflect the crack propagation behavior under shear and peeling modes. The adhesive layer 40 and the adjacent carbon fiber laminated plate 10 and foam sandwich structure 20 can be bound by Tie constraint.

[0082] It is worth noting that since no rivet 30 failure was observed in the shear strength test carried out in the foregoing step S200, only the elastic response of the rivet 30 is considered in the simulation analysis, and the damage behavior is not considered.

[0083] Further, with reference to Figure 8 and Figure 9As shown in the establishment of the test finite element model corresponding to the first test piece 100, the grid size of the adhesive layer 40 and the bonding area of the first test piece 100 is 1mm; the grid size of the rivet 30 area is 1.5mm, and the grid size of the remaining area is 5mm. The model contains 37167 C3D8R units and 3166 COH3D8R units. The boundary conditions are set according to the shear strength test described above, and full constraints are applied to the upper and lower surfaces of the clamping section of the foam sandwich structure 20 to simulate the fixture fixing mode in the test; the upper and lower surfaces of the clamping section of the carbon fiber laminate 10 are coupled by reference points, and displacement load is applied to the reference points.

[0084] Referring to Figure 10 and Figure 11 As shown in the establishment of the test finite element model corresponding to the second test piece 200, the grid size of the adhesive layer 40 and the bonding area of the second test piece 200 is 0.6mm; the grid size of the rivet 30 area is 1.5mm, and the grid size of the remaining area is 4mm. The model contains 72033 C3D8R units and 5276 COH3D8R units. The boundary conditions are set according to the shear strength test described above, and full constraints are applied to the lower surface of the foam sandwich structure 20 and the bolt hole position, and the upper and lower surfaces of the clamping section of the carbon fiber laminate are coupled by reference points, and displacement load is applied to the reference points.

[0085] Referring to Figure 12 and Figure 13 As shown in the establishment of the test finite element model corresponding to the third test piece 300, the grid size of the adhesive layer 40 and the bonding area of the third test piece 300 is 0.6mm; the grid size of the rivet 30 area is 1.5mm, and the grid size of the remaining area is 4mm. The model contains 71642 C3D8R units and 3072 COH3D8R units. The boundary conditions are set according to the shear strength test described above, and in addition to applying full constraints to the lower surface of the foam sandwich structure 20 and the bolt hole position, a fixture model for applying vertical pulling load in the testing machine is also introduced, and is coupled to the surface of the fixture through reference points, and displacement load is applied.

[0086] It is worth noting that the present application successfully constructs a high-precision test finite element model corresponding to the test specimen based on the test conditions, which is beneficial to clearly understand the influence mechanism of key structural parameters such as the thickness of the adhesive layer 40, the diameter of the rivet 30, the overlap area and the thickness of the sandwich on the performance of the adhesive-riveted joint through parameterized analysis, and provides a scientific basis for the optimal design of the adhesive-riveted joint. The method can quickly identify the optimal structure parameter combination, shorten the research and development cycle and reduce the test cost, and significantly improve the design efficiency and engineering applicability.

[0087] Step S400. Carrying out finite element simulation analysis and verification.

[0088] Run the experimental finite element model corresponding to the test specimen to perform simulation calculations to obtain the simulated load-displacement data corresponding to the test specimen; compare the simulated load-displacement data with the test load-displacement data obtained in the aforementioned step S200 to verify the accuracy of the simulation calculation results.

[0089] The accuracy of the simulation results for the three test specimens will be analyzed below, based on specific experimental results and simulation calculation results.

[0090] Figure 14 A comparison of the load-displacement curves of the first specimen 100 under experimental and simulation analysis conditions is shown. According to the test results of the shear strength test on the first specimen 100, its ultimate tensile load ranges from 11.25 kN to 14.9 kN, with an average value of 12.63 kN. Based on the calculation results of the finite element simulation analysis, the ultimate tensile load of the first specimen 100 under the same loading conditions is 13.3 kN, and the error between the simulation calculation result and the experimental result is 5.3%.

[0091] Depend on Figure 14 It can be seen that in the initial loading stage, the load-displacement curves of both the experimental and simulation results exhibit approximately linear characteristics, indicating that the external load is mainly borne by the adhesive layer 40 at this stage. As the load increases, the adhesive layer 40 fractures after reaching its ultimate bearing capacity, and the rivet 30 begins to bear the main load-bearing function. The foam sandwich structure 20 is continuously damaged under the compression of the rivet 30, ultimately leading to the failure of the first specimen 100. A comparison shows that the overall trend of the load-displacement curves of the experimental and simulation results is consistent, thus proving the accuracy of the simulation results for the first specimen 100.

[0092] Figure 15 The load-displacement curves of the second specimen 200 under experimental and simulation analysis conditions are shown in the figure. According to the test results of the shear strength test on the second specimen 200, its ultimate tensile load ranges from 11.08 kN to 14.9 kN, with an average value of 11.87 kN. Based on the calculation results of the finite element simulation analysis, the ultimate tensile load of the second specimen 200 under the same loading conditions is 12.24 kN, and the error between the simulation calculation result and the experimental result is 3.12%.

[0093] Depend on Figure 15It can be seen that the second specimen 200 exhibits a similar failure mode to the first specimen 100. Specifically, the adhesive layer 40 bears the load initially, then fractures instantaneously upon reaching its limit. After the adhesive layer 40 fails, the rivet 30 begins to bear the load, compressing the carbon fiber laminate 10 and causing its failure. When the rivet 30 is completely pulled out of the second specimen 200, the load-bearing capacity of the second specimen 200 drops to zero. Overall, the test results of the second specimen 200 show a consistent trend with the load-displacement curves in the simulation calculations.

[0094] Figure 16 A comparison of the load-displacement curves of the third specimen 300 under experimental and simulation analysis conditions is shown. The test results of the shear strength test on the third specimen 300 show that its ultimate tensile load ranges from 0.69 kN to 0.92 kN, with an average value of 0.852 kN. According to the calculation results of the finite element simulation analysis, the ultimate tensile load of the second specimen 200 under the same loading conditions is 0.92 kN, and the error between the simulation calculation result and the experimental result is 7.98%. Although the simulation calculation result deviates slightly from the experimental result, it is still within a reasonable range, demonstrating that the finite element model corresponding to the third specimen 300 has good predictive ability for this type of connection.

[0095] Depend on Figure 16 It can be seen that in the initial loading stage, the load-displacement curves of both the experimental and simulation results exhibit approximately linear characteristics, indicating that the load is borne by the adhesive layer 40. After the adhesive layer 40 fails, the load is borne by the rivets 30. Under the action of the rivets 30, the carbon fiber laminate 10 gradually undergoes partial fracture, but still has load-bearing capacity. As the displacement load increases, the carbon fiber laminate 10 continuously fractures and fails, eventually reaching the ultimate complete failure. Overall, the load-displacement curves of the third specimen 300 show a consistent trend with the simulation results.

[0096] Based on the above analysis of the test results and simulation calculation results of the three test specimens, it can be seen that the finite element model established by this invention has high accuracy in predicting the mechanical behavior of the glued joint. The good consistency between the test results and the simulation calculation results indicates that the finite element model established based on the test conditions can truly reflect the stress state and failure mode of the test specimen under external load.

[0097] It is worth noting that this invention verifies the accuracy of the finite element model in predicting mechanical response and failure behavior through a combination of experiment and simulation, overcoming the limitations of existing theoretical or simplified models.

[0098] Step S500. Practical application analysis.

[0099] On the basis of the test specimen being respectively tested and the finite element simulation analysis being performed through the foregoing steps S100 to S400, and the effectiveness of the finite element simulation analysis method being verified, the strength of the glue-riveted joint in the actual engineering structure can be further analyzed in combination with the submodel method.

[0100] Step S500 specifically includes:

[0101] Step S501. Establishing a global finite element model corresponding to the actual engineering structure (see Figure 17 ), and intercepting a local region containing the glue-riveted joint in the global finite element model as a main finite element model. The glue-riveted joint is simplified in the global finite element model. Specifically, the carbon fiber laminated plate 10 is simulated by a shell element, the foam sandwich structure 20 is simulated by a solid element, the rivet 30 is simulated by a beam element and a rigid element, and the glue layer 40 is not modeled separately. Figure 18 A main finite element model containing a glue-riveted joint intercepted from a global finite element model of a certain actual engineering structure is shown in Figure 17 ; wherein the glue-riveted joint is a crossbeam made of a foam sandwich structure 20 and a skirt plate made of a carbon fiber laminated plate 10, and the two are connected by a rivet 30 and a glue layer 40 to realize glue-riveting connection.

[0102] Step S502. The method for establishing a test finite element model described in step S200 is used to refine the modeling of the main finite element model to obtain a subfinite element model. In the subfinite element model, the carbon fiber laminated plate 10, the foam sandwich structure 20, the rivet 30, and the glue layer 40 contained therein are all modeled by solid elements; at the same time, the boundary constraints of the subfinite element model are inherited from the displacement information extracted in the global finite element model to reproduce the stress state of the glue-riveted joint region as much as possible, see Figure 19 .

[0103] On this basis, the global finite element model and the subfinite element model of the actual engineering structure are respectively run for simulation calculation to obtain the displacement nephogram and the stress nephogram in each direction corresponding to the global finite element model, and the displacement nephogram and the stress nephogram in each direction corresponding to the subfinite element model.

[0104] The displacement nephograms and the stress nephograms in each direction of the global finite element model and the subfinite element model are compared and analyzed to verify the accuracy of the subfinite element model.

[0105] Figure 20 A displacement nephogram corresponding to the main finite element model in the global finite element model is shown in Figure 21 A displacement nephogram corresponding to the subfinite element model is shown in Figure 20 and Figure 21It can be seen that the main finite element model and the sub finite element model are basically consistent in the trend of deformation distribution, and the maximum deformation position appears in the area of the carbon fiber laminated plate 10 as a skirt plate. In the main finite element model corresponding to the overall finite element model of the actual engineering structure, the maximum deformation amount is 0.534 mm, and the maximum deformation amount of the position corresponding to the sub finite element model is 0.532, and the difference is only 0.002 mm, which shows that the boundary displacement data transmitted from the overall finite element model to the sub finite element model is accurate and effective, and can ensure the reliability of the subsequent stress analysis of the sub finite element model.

[0106] According to the embodiment of the application, by combining the sub-model technology to carry out local refined analysis on the key area containing the glue-riveted joint, the stress concentration area can be accurately captured, a reliable tool is provided for the strength checking of the complex structure, and it is ensured that the design result meets the safety requirements under the harsh working conditions of rail transit and the like.

[0107] The application realizes the refinement, parameterization and engineering of the strength analysis of the glue-riveted joint through the cooperation of test and simulation, significantly improves the scientificity and economy of the design of the composite material structure connection, and provides a key technical support for the safe and reliable operation of the lightweight equipment.

[0108] Embodiment 2

[0109] On the basis of embodiment 1, the embodiment 2 of the application further provides an electronic device. The electronic device includes a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the carbon fiber laminated plate and foam sandwich structure glue-riveted joint strength analysis method as described in embodiment 1 is realized.

[0110] The memory can be realized by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk.

[0111] Embodiment 3

[0112] Based on the embodiment 1, the embodiment 3 of the present application further provides a readable storage medium. The readable storage medium stores a computer program, and the computer program is executed by a processor to implement the strength analysis method of the carbon fiber laminated plate and foam sandwich structure glue-riveted joint described in the above embodiment 1.

[0113] The readable storage medium can be specifically a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various readable storage media capable of storing program codes.

[0114] The above only provides preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for strength analysis of adhesive-fitted joints in carbon fiber laminate and foam sandwich structures, characterized in that, Includes the following steps: Shear strength tests are conducted on the test specimens under predetermined test conditions to obtain the failure modes and test load-displacement data corresponding to the test specimens; the test specimens include carbon fiber laminates and foam sandwich structures, and the carbon fiber laminates and foam sandwich structures are connected by adhesive layers and rivets. Based on the aforementioned test conditions, an experimental finite element model corresponding to the test specimen was established. In the experimental finite element model, a custom subroutine was used to simulate the anisotropic progressive damage behavior of the carbon fiber laminate. The three-dimensional Hashin criterion was used as the failure criterion for the carbon fiber laminate, and the damage evolution process of the carbon fiber laminate was described by combining the linear degradation method controlled by energy dissipation. The foam core material in the foam sandwich structure was simulated using a compressible foam model. The adhesive layer was modeled using three-dimensional cohesive elements based on cohesion theory. Its initial damage criterion adopted a quadratic criterion based on nominal stress, and the damage evolution process was described by the Benzeggaggh-Kenane criterion. The experimental finite element model was run to perform simulation calculations to obtain simulated load-displacement data corresponding to the test specimen; the simulated load-displacement data was compared with the experimental load-displacement data to verify the accuracy of the simulation calculation results. A global finite element model corresponding to the actual engineering structure is established, and a local area containing the glued riveting joint in the global finite element model is extracted as the master finite element model; the glued riveting joint is simplified in the global finite element model. The method for establishing the experimental finite element model is used to refine the main finite element model to obtain the sub-finite element model; Simulation calculations were performed using the overall finite element model and the sub-finite element model to obtain displacement contour maps and stress contour maps in each direction corresponding to the overall finite element model, as well as displacement contour maps and stress contour maps in each direction corresponding to the sub-finite element model. The displacement contour maps and stress contour maps in each direction of the overall finite element model and the sub-finite element model are compared and analyzed to verify the accuracy of the sub-finite element model.

2. The method for strength analysis of the adhesive joint of carbon fiber laminate and foam sandwich structure according to claim 1, characterized in that, The custom subroutine is VUMAT; and in the experimental finite element model, the adhesive layer is bonded to the adjacent carbon fiber laminate and foam sandwich structure through tie constraints.

3. The method for strength analysis of the adhesive joint of carbon fiber laminate and foam sandwich structure according to claim 1, characterized in that, In the sub-finite element model, the carbon fiber laminate, foam sandwich structure, rivets and adhesive layer are all modeled using solid elements; the boundary constraints of the sub-finite element model are inherited from the displacement information extracted from the overall finite element model.

4. The method for strength analysis of the adhesive joint of carbon fiber laminate and foam sandwich structure according to claim 1, characterized in that, The simplified modeling is as follows: the carbon fiber laminate is simulated using shell elements, the foam sandwich structure is simulated using solid elements, the rivets are simulated using beam elements and rigid elements, and the adhesive layer is not modeled separately.

5. The method for strength analysis of the adhesive-fitted joint of carbon fiber laminate and foam sandwich structure according to claim 1, characterized in that, The test specimens include a first specimen, a second specimen, and a third specimen; the thickness of the foam sandwich structure in the first specimen is less than the thickness of the foam sandwich structure in the second specimen; the thickness of the foam sandwich structure in the second specimen is equal to the thickness of the foam sandwich structure in the third specimen.

6. The method for strength analysis of the adhesive joint of carbon fiber laminate and foam sandwich structure according to claim 5, characterized in that, The shear strength test of the test specimen was conducted using an MTS tensile-torsion testing machine. In the shear strength test of the first specimen, the testing machine applies a planar shear load to the first specimen; In the shear strength test of the second specimen, the testing machine applies a planar shear load to the second specimen; In the shear strength test of the third specimen, the testing machine applied a vertical pull-out load to the third specimen.

7. The method for strength analysis of the adhesive joint of carbon fiber laminate and foam sandwich structure according to claim 1, characterized in that, In the experimental finite element model, the carbon fiber laminate, foam sandwich structure, and rivets in the test specimen are all modeled using three-dimensional solid elements; the boundary conditions of the experimental finite element model are set with reference to the shear strength test.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the strength analysis method for the adhesive joint of the carbon fiber laminate and foam sandwich structure as described in any one of claims 1 to 7.

9. A readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the strength analysis method for the adhesive riveting joint of the carbon fiber laminate and foam sandwich structure as described in any one of claims 1 to 7.

Images