Finite element simulation method for initial layering damage fatigue expansion of composite T-shaped stiffened plate structure

Abstract

The invention discloses a finite element simulation method for initial layering damage fatigue extension of a composite T-shaped stiffened plate structure. The method comprises the steps that ABAQUS is adopted to establish a finite element model of the composite T-shaped stiffened plate structure containing initial layering; according to the method, ABAQUS is subjected to secondary development, a UMIXMODEFATIGUE subprogram is compiled based on a virtual crack closure (VCCT) technology, a BK criterion is selected as a mixed mode criterion, and a Paris criterion is selected as a damage fatigue extension criterion; the subprogram is called, the finite element model of the composite T-shaped stiffened plate structure is calculated, and simulation analysis of initial layering damage fatigue extension of the composite T-shaped stiffened plate structure is achieved. According to the method, the evolution path, the expansion rate and the damage morphology of the initial layering damage of the rib-skin interface of the composite T-shaped stiffened plate structure under the fatigue load can be simulated, and the method has great engineering value.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a finite element simulation method for initial delamination damage fatigue propagation in a composite T-shaped stiffened plate structure. Background Technology

[0002] Composite materials, with their superior specific strength, specific stiffness, and designability, have become one of the key materials for modern aerospace vehicles. Their application can significantly reduce structural weight, thereby effectively improving the fuel economy, load capacity, and overall performance of aircraft. As the performance requirements for aircraft continue to increase, the application scope of composite materials is expanding from secondary load-bearing structures to primary load-bearing structures such as wings and fuselages, which places higher demands on the design, analysis, and verification of structures.

[0003] In composite material load-bearing structures, stiffened plates are a typical structural element for improving the stability and load-bearing efficiency of thin-walled structures. Among them, T-shaped stiffened plates are widely used in practice due to their simple configuration, clear force transmission path, and ease of manufacturing and assembly. This type of structure provides stable support to the skin through stiffeners, allowing the skin to continue bearing loads after buckling, achieving efficient material utilization and further weight reduction. However, during manufacturing, assembly, or service, the interface between the stiffeners and the skin is highly susceptible to initial delamination damage due to low-energy impacts and other factors. This damage is highly concealed and difficult to visually inspect, posing a potential safety hazard.

[0004] When a composite T-stiffened plate structure with initial delamination is subjected to fatigue loads, the initial delamination will propagate along the interface. In engineering, predicting the evolution path, propagation rate, and damage morphology of the initial delamination under fatigue loads is crucial. Relying solely on subsequent testing is not only costly and time-consuming, but also fails to provide complete, visualized damage evolution data, resulting in a lack of forward-looking and accurate data support for damage tolerance assessment and maintenance strategy development. Therefore, developing a dedicated finite element simulation method capable of accurately simulating the entire process of initial delamination damage propagation in composite T-stiffened plate structures is of significant engineering value for achieving safe design and condition-based maintenance of such structures. Summary of the Invention

[0005] The finite element method for fatigue propagation of initial delamination damage in composite T-stiffened plate structures provided by this invention can simulate the evolution path, propagation rate, and damage morphology of initial delamination damage at the stiffener-skin interface under fatigue loads. This provides engineers with visualized damage evolution data throughout the entire process, which is difficult to capture using traditional testing methods. This has direct guiding significance for accurately assessing damage tolerance, locating key maintenance areas, and developing targeted non-destructive testing plans, thereby significantly improving the accuracy of safety maintenance and condition assessment of such structures during service.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a finite element simulation method for initial delamination damage fatigue propagation in a composite T-shaped stiffened plate structure, comprising the following steps:

[0008] 1) A finite element model of a composite T-shaped stiffened plate structure with initial layering was established using ABAQUS;

[0009] 2) Secondary development of ABAQUS was carried out, and the UMIXMODEFATIGUE subroutine was written based on the virtual crack closure technology VCCT. The BK criterion was selected as the mixed mode criterion, and the Paris criterion was selected as the damage fatigue propagation criterion.

[0010] 3) Call the subroutine to calculate the finite element model of the composite T-shaped stiffened plate structure, and realize the simulation analysis of the initial delamination damage fatigue propagation of the composite T-shaped stiffened plate structure.

[0011] Furthermore, the steps for establishing the finite element model of the composite T-shaped stiffened plate structure using ABAQUS in step 1) are as follows:

[0012] 11) Establish a geometric model of the composite T-shaped stiffened plate structure, which is assembled from two parts: stiffeners and skin;

[0013] 12) Determine the material parameters of the composite ribs and skin, and establish the composite layer of composite ribs and skin;

[0014] 13) Mesh the geometric model of the composite T-shaped stiffened plate structure;

[0015] 14) Set the interaction and contact properties between the ribs and the skin;

[0016] 15) Set the static general analysis step and the direct cycle analysis step in sequence;

[0017] 16) Cut out clamping areas at both ends of the finite element model of the composite T-shaped stiffened plate structure, set the boundary conditions as follows: the lower clamping area is fixed and the upper clamping area is subjected to displacement loading.

[0018] 17) Modify the keywords; the keywords include *Fracture Criterion, type=fatigue, mixedmode behavior=USER, properties=6, position=nonlocal; then enter user-defined data, including Paris criterion parameters, critical energy release rate, and BK criterion parameters.

[0019] Furthermore, in step 12), the stiffeners and skin of the composite T-shaped stiffened plate structure are all obtained by laying carbon fiber unidirectional tapes in a predetermined layup sequence, and a composite layer is established according to the unidirectional tape material and layup sequence of the actual structure.

[0020] Furthermore, in step 13), SC8R cells are selected, and the mesh type is a hexahedral swept mesh.

[0021] Furthermore, in step 14), the ribs and skin are set to surface-to-surface contact, the slip formula is small slip, the discretization method is nodal surface, the initial bonding node set is set to all nodes between the ribs and skin except for the initial layered region, the contact property normal behavior is hard contact, and the fracture criterion is VCCT.

[0022] Furthermore, in step 16), the static general analysis step applies a static load to the average fatigue load level, and the direct cyclic analysis step applies a sinusoidal fatigue load.

[0023] Furthermore, the specific steps for writing the UMIXMODEFATIGUE subroutine based on the virtual crack closure technology VCCT in step 2) are as follows:

[0024] 21) Open the Visual Studio compiler and enter the ABAQUS solver UMIXMODEFATIGUE subroutine interface code;

[0025] 22) Define the variables to be used in the program and read the user-defined attribute parameters in ABAQUS;

[0026] 23) Input the BK criterion code and calculate the critical energy release rate driving stratification propagation under mixed damage mode. And determine the total energy release rate. Is it higher than Enter the Paris criterion code, if Below Then no extension behavior will occur, if Higher than The extent of layered damage propagation is then calculated according to the Paris criterion.

[0027] Furthermore, step 23) is as follows:

[0028] Total energy release rate The calculation formula is as follows:

[0029] ;

[0030] In the formula, , , These are the differences between the maximum and minimum energy release rates of types I, II, and III in each load cycle, respectively, and are called the energy release rate amplitude; the critical energy release rate value driving hierarchical expansion under the mixed damage mode in the BK criterion. The calculation formula is as follows:

[0031] ;

[0032] In the formula, η is a user-defined parameter of the BK criterion; , , The critical energy release rates are for damage modes I, II, and III, respectively; the Paris criterion is used to calculate the layer propagation rate, and the calculation formula is as follows:

[0033] ;

[0034] In the formula, C and m are custom parameters of the Paris criterion, representing the damage propagation rate for each cycle.

[0035] The beneficial effects of this invention are:

[0036] The finite element method for fatigue propagation of initial delamination damage in composite T-stiffened plate structures provided by this invention can simulate the evolution path, propagation rate, and damage morphology of initial delamination damage at the stiffener-skin interface under fatigue loads. This provides engineers with visualized damage evolution data throughout the entire process, which is difficult to capture using traditional testing methods. This has direct guiding significance for accurately assessing damage tolerance, locating key maintenance areas, and developing targeted non-destructive testing plans, thereby significantly improving the accuracy of safety maintenance and condition assessment of such structures during service. Attached Figure Description

[0037] Figure 1 This is a flowchart of the method of the present invention;

[0038] Figure 2 This is a schematic diagram of the composite T-shaped stiffened plate structure in the embodiment;

[0039] Figure 3 This is a mesh diagram of the finite element model of the composite T-shaped stiffened plate structure in the embodiment;

[0040] Figure 4 This is a boundary condition diagram of the finite element model of the composite T-shaped stiffened plate structure in the embodiment;

[0041] Figure 5 This is a delamination damage propagation diagram of the finite element model of the composite T-shaped stiffened plate structure in the embodiment. Detailed Implementation

[0042] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0043] The present invention provides a finite element simulation method for initial delamination damage fatigue propagation in a composite T-shaped stiffened plate structure, comprising the following steps:

[0044] 1) A finite element model of a composite T-shaped stiffened plate structure with initial layering was established using ABAQUS;

[0045] 2) Secondary development of ABAQUS was carried out, and the UMIXMODEFATIGUE subroutine was written based on the virtual crack closure technology VCCT. The BK criterion was selected as the mixed mode criterion, and the Paris criterion was selected as the damage fatigue propagation criterion.

[0046] 3) Call the subroutine to calculate the finite element model of the composite T-shaped stiffened plate structure, and realize the simulation analysis of the initial delamination damage fatigue propagation of the composite T-shaped stiffened plate structure.

[0047] Furthermore, the steps for establishing the finite element model of the composite T-shaped stiffened plate structure using ABAQUS in step 1) are as follows:

[0048] 11) Establish a geometric model of the composite T-shaped stiffened plate structure, which is assembled from two parts: stiffeners and skin;

[0049] 12) Determine the material parameters of the composite ribs and skin, and establish the composite layer of composite ribs and skin;

[0050] 13) Mesh the geometric model of the composite T-shaped stiffened plate structure;

[0051] 14) Set the interaction and contact properties between the ribs and the skin;

[0052] 15) Set the static general analysis step and the direct cycle analysis step in sequence;

[0053] 16) Cut out clamping areas at both ends of the finite element model of the composite T-shaped stiffened plate structure, set the boundary conditions as follows: the lower clamping area is fixed and the upper clamping area is subjected to displacement loading.

[0054] 17) Modify the keywords; the keywords include *Fracture Criterion, type=fatigue, mixedmode behavior=USER, properties=6, position=nonlocal; then enter user-defined data, including Paris criterion parameters, critical energy release rate, and BK criterion parameters.

[0055] Furthermore, in step 12), the stiffeners and skin of the composite T-shaped stiffened plate structure are all obtained by laying carbon fiber unidirectional tapes in a predetermined layup sequence, and a composite layer is established according to the unidirectional tape material and layup sequence of the actual structure.

[0056] Furthermore, in step 13), SC8R cells are selected, and the mesh type is a hexahedral swept mesh.

[0057] Furthermore, in step 14), the ribs and skin are set to surface-to-surface contact, the slip formula is small slip, the discretization method is nodal surface, the initial bonding node set is set to all nodes between the ribs and skin except for the initial layered region, the contact property normal behavior is hard contact, and the fracture criterion is VCCT.

[0058] Furthermore, in step 16), the static general analysis step applies a static load to the average fatigue load level, and the direct cyclic analysis step applies a sinusoidal fatigue load.

[0059] Furthermore, the specific steps for writing the UMIXMODEFATIGUE subroutine based on the virtual crack closure technology VCCT in step 2) are as follows:

[0060] 21) Open the Visual Studio compiler and enter the ABAQUS solver UMIXMODEFATIGUE subroutine interface code;

[0061] 22) Define the variables to be used in the program and read the user-defined attribute parameters in ABAQUS;

[0062] 23) Input the BK criterion code and calculate the critical energy release rate driving stratification propagation under mixed damage mode. And determine the total energy release rate. Is it higher than Enter the Paris criterion code, if Below Then no extension behavior will occur, if Higher than The extent of layered damage propagation is then calculated according to the Paris criterion.

[0063] Furthermore, step 23) is as follows:

[0064] Total energy release rate The calculation formula is as follows:

[0065] ;

[0066] In the formula, , , These are the differences between the maximum and minimum energy release rates of types I, II, and III in each load cycle, respectively, and are called the energy release rate amplitude; the critical energy release rate value driving hierarchical expansion under the mixed damage mode in the BK criterion. The calculation formula is as follows:

[0067] ;

[0068] In the formula, η is a user-defined parameter of the BK criterion; , , The critical energy release rates are for damage modes I, II, and III, respectively; the Paris criterion is used to calculate the layer propagation rate, and the calculation formula is as follows:

[0069] ;

[0070] In the formula, C and m are custom parameters of the Paris criterion, representing the damage propagation rate for each cycle.

[0071] Example: This example describes a composite T-shaped stiffened plate structure. Both the stiffeners and the skin material are T300 / YB01 carbon fiber laminates. The stiffeners are bonded to the middle of the skin, with a layup of [45 / -45 / 0 / -45 / 45]s. The edge strip dimensions are 65.5mm*300mm*1.45mm, and the web dimensions are 45mm*300mm*1.45mm. The skin layup is [45 / -45 / 0 / 45 / 90 / -45 / 0]s, with dimensions of 165.5mm*300mm*2.1mm. The initial layer area is 30mm*30mm. A schematic diagram is shown below. Figure 2 As shown.

[0072] The specific steps for the finite element simulation of the initial delamination damage fatigue propagation of the aforementioned composite T-stiffened plate structure are as follows:

[0073] 1) Perform secondary development on ABAQUS, write the UMIXMODEFATIGUE subroutine based on Virtual Crack Closure Technique (VCCT), select the BK criterion as the mixed mode criterion, and select the Paris criterion as the damage fatigue propagation criterion;

[0074] 2) A finite element model of the composite T-shaped stiffened plate structure with initial layering was established using ABAQUS;

[0075] 3) Call the subroutine to calculate the finite element model of the composite T-shaped stiffened plate structure, and realize the simulation analysis of the initial delamination damage fatigue propagation of the composite T-shaped stiffened plate structure;

[0076] Furthermore, the steps for writing the UMIXMODEFATIGUE subroutine in step 1) are as follows:

[0077] 11) Open the Visual Studio compiler and enter the ABAQUS solver UMIXMODEFATIGUE subroutine interface code;

[0078] 12) Read user-defined attribute parameters in ABAQUS, including critical energy release rate, BK criterion parameters, and Paris criterion parameters in different modes;

[0079] Table 1 User-defined attribute parameters

[0080]

[0081] 13) Input the BK criterion code and calculate the critical energy release rate driving stratification propagation under the mixed damage mode. And determine the total energy release rate. Is it higher than Enter the Paris criterion code, if Below Then it will not be expanded, if Higher than Then, the layered damage propagation is calculated according to the Paris criterion.

[0082] Furthermore, step 13) is as follows:

[0083] Total energy release rate The calculation formula is as follows:

[0084]

[0085] In the formula, , , These are the differences between the maximum and minimum energy release rates of types I, II, and III in each load cycle, respectively, and are called the energy release rate amplitude; the critical energy release rate value driving hierarchical expansion under the mixed damage mode in the BK criterion. The calculation formula is as follows:

[0086]

[0087] In the formula, η is a user-defined parameter of the BK criterion; , , The critical energy release rates are for damage modes I, II, and III, respectively; the Paris criterion is used to calculate the layer propagation rate, and the calculation formula is as follows:

[0088]

[0089] In the formula, C and m are custom parameters of the Paris criterion, representing the damage propagation rate for each cycle.

[0090] Furthermore, the steps for establishing the finite element model of the composite T-shaped stiffened plate structure using ABAQUS in step 2) are as follows:

[0091] 21) Establish a geometric model of the composite T-shaped stiffened plate structure, which is assembled from two parts: stiffeners and skin;

[0092] 22) In the composite T-shaped stiffened plate structure, the stiffeners and skin are all made of carbon fiber unidirectional tape laid in a predetermined layup sequence. Determine the material parameters of T300 / YB01 carbon fiber laminate for the composite stiffeners and skin, and establish the composite layer according to the unidirectional tape material and layup sequence of the actual structure.

[0093] Table 2 Material parameters of T300 / YB01 carbon fiber laminate

[0094]

[0095] 23) Mesh the composite T-shaped stiffened plate structure model, selecting SC8R elements and a hexahedral swept mesh type, such as... Figure 3 As shown;

[0096] 24) Set the interaction and contact properties between the ribs and skin. Set the contact between the ribs and skin to be surface-to-surface, the slip formula to be small slip, the discretization method to be node-surface, set the initial bonding node set to all nodes between the ribs and skin except for the initial layered region, set the contact property normal behavior to hard contact, and select VCCT as the fracture criterion.

[0097] 25) Set the static general analysis step and the direct cycle analysis step in sequence;

[0098] 26) Cut clamping zones at both ends of the model, set the boundary conditions as follows: the lower clamping zone is fixed, and the upper clamping zone is subjected to displacement loading. During the static general analysis step, apply static loads up to the average fatigue load level. During the direct cyclic analysis step, apply sinusoidal fatigue loads, such as... Figure 4 As shown.

[0099] 27) Modify the keywords *Fracture Criterion, type=fatigue, mixed mode behavior=USER, properties=6, position=nonlocal and enter user-defined data, including Paris criterion parameters, critical energy release rate and BK criterion parameters.

[0100] 28) In the job editing interface, call the subroutine file and submit the job for analysis. The layered damage propagation situation is as follows: Figure 5 As shown.

[0101] This invention has many specific applications. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A finite element simulation method for initial delamination damage fatigue propagation in a composite T-shaped stiffened plate structure, characterized in that, The steps are as follows: 1) A finite element model of a composite T-shaped stiffened plate structure with initial layering was established using ABAQUS; 2) Secondary development of ABAQUS was carried out, and the UMIXMODEFATIGUE subroutine was written based on the virtual crack closure technology VCCT. The BK criterion was selected as the mixed mode criterion, and the Paris criterion was selected as the damage fatigue propagation criterion. 3) Call the subroutine to calculate the finite element model of the composite T-shaped stiffened plate structure, and realize the simulation analysis of the initial delamination damage fatigue propagation of the composite T-shaped stiffened plate structure.

2. The finite element simulation method for initial delamination damage fatigue propagation of composite T-shaped stiffened plate structures according to claim 1, characterized in that, The steps for establishing the finite element model of the composite T-shaped stiffened plate structure using ABAQUS in step 1) are as follows: 11) Establish a geometric model of the composite T-shaped stiffened plate structure, which is assembled from two parts: stiffeners and skin; 12) Determine the material parameters of the composite ribs and skin, and establish the composite layer of composite ribs and skin; 13) Mesh the geometric model of the composite T-shaped stiffened plate structure; 14) Set the interaction and contact properties between the ribs and the skin; 15) Set the static general analysis step and the direct cycle analysis step in sequence; 16) Cut out clamping areas at both ends of the finite element model of the composite T-shaped stiffened plate structure, set the boundary conditions as follows: the lower clamping area is fixed and the upper clamping area is subjected to displacement loading. 17) Modify the keywords; the keywords include *Fracture Criterion, type=fatigue, mixed modebehavior=USER, properties=6, position=nonlocal; then enter user-defined data, including Paris criterion parameters, critical energy release rate, and BK criterion parameters.

3. The finite element simulation method for initial delamination damage fatigue propagation of composite T-shaped stiffened plate structures according to claim 2, characterized in that, In step 12), the stiffeners and skin of the composite T-shaped stiffened plate structure are all obtained by laying carbon fiber unidirectional tapes in a predetermined layup sequence, and a composite layer is established according to the unidirectional tape material and layup sequence of the actual structure.

4. The finite element simulation method for initial delamination damage fatigue propagation of composite T-shaped stiffened plate structures according to claim 2, characterized in that, In step 13), select the SC8R element, and the mesh type is a hexahedral swept mesh.

5. The finite element simulation method for initial delamination damage fatigue propagation of composite T-shaped stiffened plate structures according to claim 2, characterized in that, In step 14), the ribs and skin are set to surface-to-surface contact, the slip formula is small slip, the discretization method is nodal surface, the initial bonding node set is set to all nodes between the ribs and skin except for the initial layered region, the contact property normal behavior is hard contact, and the fracture criterion is VCCT.

6. The finite element simulation method for initial delamination damage fatigue propagation of composite T-shaped stiffened plate structures according to claim 2, characterized in that, In step 16), the static general analysis step applies a static load to the average fatigue load level, and the direct cyclic analysis step applies a sinusoidal fatigue load.

7. The finite element simulation method for initial delamination damage fatigue propagation of composite T-shaped stiffened plate structures according to claim 1, characterized in that, The specific steps for writing the UMIXMODEFATIGUE subroutine based on the virtual crack closure technology VCCT in step 2) are as follows: 21) Open the Visual Studio compiler and enter the ABAQUS solver UMIXMODEFATIGUE subroutine interface code; 22) Define the variables to be used in the program and read the user-defined attribute parameters in ABAQUS; 23) Input the BK criterion code and calculate the critical energy release rate driving stratification propagation under mixed damage mode. And determine the total energy release rate. Is it higher than Enter the Paris criterion code, if Below Then no extension behavior will occur, if Higher than The extent of layered damage propagation is then calculated according to the Paris criterion.

8. The finite element simulation method for initial delamination damage fatigue propagation of composite T-shaped stiffened plate structures according to claim 7, characterized in that, Step 23) is as follows: Total energy release rate The calculation formula is as follows: ； In the formula, , , These are the differences between the maximum and minimum energy release rates of types I, II, and III in each load cycle, and are called the energy release rate amplitude. Critical energy release rate for driving layered propagation under mixed damage modes in the BK criterion The calculation formula is as follows: ； In the formula, η is a user-defined parameter of the BK criterion; , , The critical energy release rates are for damage modes I, II, and III, respectively; the Paris criterion is used to calculate the layer propagation rate, and the calculation formula is as follows: ； In the formula, C and m are custom parameters for the damage propagation rate in each cycle, defined by the Paris criterion.

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