A method for quickly determining the repair tolerance value of a honeycomb sandwich structure perforation damage

Abstract

The application belongs to the technical field of helicopter structure repair, and particularly relates to a method for quickly determining a repair tolerance value of a honeycomb sandwich structure perforation damage, ABAQUS modeling of a composite material honeycomb sandwich structure is performed to obtain a repair model; an ABAQUS script is written to realize parameterization of the repair model; on the basis of meeting 100% strength recovery rate, the key parameters are optimized to realize minimization of the weight of the repaired structure, and an optimal mathematical model of the patch repair of the honeycomb sandwich structure containing the perforation damage is obtained; the NSGA-II genetic algorithm is used to realize quick optimization of the repair scheme; on the basis of the quick optimization of the repair scheme combined with the genetic algorithm, the calling function of the Python language is used to drive the automatic modeling of the ABAQUS kernel, and then a process for determining the upper limit of the repair tolerance of the honeycomb sandwich structure perforation damage is established; the dichotomy method is used to change the radius R of the perforation damage to determine the upper limit of the repair tolerance. The method can obtain the repair optimization scheme of different perforation damages and realize quick determination of the repair tolerance.

Description

Technical Field

[0001] This invention belongs to the field of helicopter structural repair technology, specifically involving a rapid method for determining the repair tolerance value of perforation damage in a honeycomb sandwich structure. Background Technology

[0002] Composite honeycomb sandwich structures are widely used in aircraft such as helicopters. During use, they are likely to suffer perforation damage from impacts such as ground gravel, hail, bird strikes, projectile strikes, and collisions with ground equipment. Accurately and quickly determining whether damage is permissible, repairable, or irreparable, especially the boundary between repairable and irreparable damage (i.e., the upper limit of repair tolerance), is crucial for the engineering community.

[0003] If the repair tolerance limit is set unreasonably, two outcomes may occur: If the repair tolerance limit is set too high, it will be assumed that all damage that is practically impossible to repair can be restored to its original performance, leading to structural safety hazards. If the repair tolerance limit is set too conservatively, all repairable damage will be handled by replacement or scrapping, resulting in economic losses.

[0004] In the prior art, the disclosed patents mainly include methods for determining the repair tolerance of laminates and composite material structures. Among them, patent CN202110181634.1 introduces a method for determining the repair tolerance of composite material laminates, which combines the design allowable strain value with a combination of static testing and ABAQUS simulation to obtain the lower and upper limits of the repair tolerance.

[0005] Patent CN202111238101.9 introduces a method for determining the repair tolerance of composite material structural components. This method combines failure probability and maintenance cost assessment based on Bayesian theory to determine the lower limit of repair from a safety perspective and the upper limit of repair from an economic perspective.

[0006] The aforementioned patents mainly describe methods for determining repair tolerance of composite material structures. However, patent CN202110181634.1 is only applicable to the repair of laminates with pore damage. It uses a method of testing and simulation after repairing damaged parts with different degrees of damage to determine the upper limit of the repair tolerance. It lacks the process of optimizing the repair scheme design. Patent CN202111238101.9 is applicable to the repair of composite material structures. It focuses on determining the upper limit of the repair tolerance from the perspective of failure probability and maintenance economy. It uses a method of solving the failure probability and maintenance cost average through multiple simulations. It does not optimize the repair design scheme from the perspective of strength analysis. Summary of the Invention

[0007] The purpose of this invention is to provide a method for determining the repair tolerance of composite honeycomb sandwich structures for perforation damage, which can not only obtain the repair optimization scheme for different perforation damages, but also realize the rapid determination of the repair tolerance (upper limit).

[0008] The technical solution of the present invention: a method for rapidly determining the repair tolerance value of perforation damage in a honeycomb sandwich structure, the method comprising the following steps:

[0009] Step S1: Perform ABAQUS modeling of the composite honeycomb sandwich structure to obtain the repair model;

[0010] Step S2: Write an ABAQUS script using Python to parameterize the repair model;

[0011] Step S3: Based on achieving a 100% strength recovery rate, the repair structure weight is minimized by optimizing key parameters, resulting in an optimized mathematical model for patching and repairing honeycomb sandwich structures with perforation damage.

[0012] Step S4: Use the NSGA-II genetic algorithm to quickly optimize the repair scheme;

[0013] Step S5: Based on the rapid optimization of the repair scheme combined with the NSGA-II genetic algorithm, the modeFRONTIER multi-objective optimization software is used to drive the automatic modeling of the ABAQUS kernel through the calling function of the Python language, and then integrates and establishes a process to determine the upper limit of the repair tolerance for perforation damage in the honeycomb sandwich structure.

[0014] Step S6: Use the bisection method to change the perforation damage radius R and determine the upper limit of the repair tolerance. Specifically, when the result of the repair optimization scheme meets the constraint conditions, the perforation damage radius R is increased. If the increased perforation damage radius R still meets the constraint conditions, the perforation damage radius R is further increased until the constraint conditions can no longer be met. Then, the perforation damage radius R is reduced in reverse. That is, the intermediate value is taken between the minimum perforation damage radius R that does not meet the constraint conditions and the maximum perforation damage radius R that meets the constraint conditions. Iterative calculations are carried out to obtain the repair optimization scheme results for different perforation damage radii R. Based on the criterion that the perforation damage radius that cannot be further increased through structural repair optimization under the premise of meeting the constraint conditions is the upper limit of the perforation damage repair tolerance of the honeycomb sandwich structure, the final upper limit of the repair tolerance is obtained.

[0015] Furthermore, in step S3, the key parameters include at least the size, angle, and number of layers of the repair patch.

[0016] Furthermore, in step S6, the cyclic calculation is a sequential repetition of the above process for determining the repair tolerance limit, i.e., steps S4 to S6.

[0017] The beneficial effects of this invention are as follows: By integrating the ABAQUS finite element software and the modeFRONTIER multi-objective optimization software, along with the parameterization and automation of finite element simulation modeling using Python and the NSGA-II genetic algorithm, the computational efficiency of structural repair scheme optimization can be significantly improved, thereby enabling the rapid determination of the repair tolerance (upper limit) for perforation damage in composite honeycomb sandwich structures. Furthermore, this method can be extended to determine the structural repair tolerance (upper limit) for various damage modes in honeycomb sandwich structures, including single-sided perforation damage, large-area core debonding damage, and panel scratches.

[0018] This invention has at least the following advantages:

[0019] 1. When optimizing structural repairs and determining repair tolerances (upper limits), it can quickly find the optimal solution without traversing all repair schemes. Only a small number of calculations are needed, significantly reducing computational load and demonstrating high efficiency. For example: assuming the perforation damage radius R is 30mm, the internal and external repair layers are 4 layers, and the optimization step size R1 is 1mm, the step size l is 5mm, and θ... n or θ′ n The step size is 15°, and R1 is 10mm to 15mm larger than R, l is 10mm to 25mm, and θ n or θ′ n If the angle is -45° to 45°, 153,664 combinations of calculations are required (2,401 combinations for repairing patch layup angles alone) to obtain the optimal repair optimization scheme. However, using this algorithm, only 237 combinations need to be calculated.

[0020] 2. This method for rapidly determining the repair tolerance (upper limit) is universal and can be applied to damage modes of other composite material structures;

[0021] 3. A relatively complete process and method for determining the repair tolerance (upper limit) of perforation damage in honeycomb sandwich structures has been developed. Attached Figure Description

[0022] Figure 1 It is a composite material honeycomb sandwich structure;

[0023] Figure 2 It is a honeycomb sandwich structure containing perforation damage;

[0024] Figure 3 Geometry settings for repair patch layup (parameters);

[0025] Figure 4 A flowchart for determining the repair tolerance (upper limit) for perforation damage in a honeycomb sandwich structure. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] See appendix Figure 1-4 This invention specifically proposes a rapid method for determining the repair tolerance value of perforation damage in a honeycomb sandwich structure. The implementation process of the method includes the following steps:

[0028] First, a composite honeycomb sandwich structure 1 (such as...) is constructed. Figure 1 The ABAQUS modeling process for the example shown is as follows:

[0029] Step 1: Use S4R shell elements to simulate outer panel 2 and inner panel 3, and use the two-dimensional Hashin criterion as the criterion for the initiation and evolution of panel damage;

[0030] Step 2: Using the sandwich panel theory, the honeycomb core 4 is equivalent to a uniform, continuous, and uniformly thick orthotropic anisotropic layer, and simulated with C3D8R solid elements to give it three-dimensional engineering constant properties and orientation;

[0031] Step 3: Use structural adhesive film to bind and constrain the panels and honeycomb cores, as well as the laminated areas between panels;

[0032] Step 4: Remove a through-hole from the center of the undamaged model to simulate a through-hole damage of radius R (e.g., ...). Figure 2 (as shown);

[0033] Step 5: Simulate repair of patch 6 using S4R shell unit (e.g., Figure 3 (as shown);

[0034] Step 6: Simulate the repair of patch film 7 using cohesive interfacial contact, predict initial damage using the Quadratic Nominal Stress criterion (QUADS), and perform damage evolution analysis using the BK criterion;

[0035] Step 7: Simulate expanding foam 8 using binding constraints;

[0036] Step 8: Simulate the honeycomb core plug 9 using C3D8R solid elements and assign it three-dimensional engineering constant properties and orientation;

[0037] Step 9: First, conduct a preliminary assessment of the most severe load conditions (i.e., dangerous conditions) that the damaged composite honeycomb sandwich structure may withstand, and define the corresponding boundary conditions.

[0038] Step 10: Simulate and evaluate the strength of the non-destructive model to determine a baseline value for subsequent repair scheme optimization.

[0039] Step 11: Simulate and evaluate the strength of the model with perforation damage and the repair model.

[0040] Then, an ABAQUS script was written in Python to implement the parameterization of the repair model. The main steps are as follows:

[0041] Step 1: def Ct(self, lm, lp, lh = R): # Define function Ct() to perform preprocessing and computation submission;

[0042] Step 2: s.RadialDimension(,, radius=R1) # The geometry creation of the first repair layer ply radius R1 is similar to that of the lap length l and the perforation damage radius R.

[0043] Step 3: compositeLayup.Compositeply(,,orientationValue=θn,,) # Repair the ply angle θn in the geometric establishment of the model;

[0044] Step 4: p.generateMesh() # Perform model mesh generation;

[0045] Step 5: rf = region.historyOutputs['RF1'].data # Read the failure load F from the finite element simulation analysis;

[0046] Step 6: ms = myodb.steps['Step-1'].mass # Read the weight M of the repair structure from the finite element simulation analysis;

[0047] Step 7: def getIVal(self): # Define the function getIVal() to obtain the specific values ​​of the repair patch layup parameters from the input file;

[0048] Step 8: def wrtVal(self, v): # Define the function wrtVal(), which writes the destructive load F and the repair structure weight M to the output file.

[0049] Next, a repair optimization analysis is performed. This involves minimizing the weight of the repaired structure by optimizing the size, angle, and number of repair patch layers while maintaining a 100% strength recovery rate. The mathematical model for optimizing the patch repair of a honeycomb sandwich structure with perforated damage is set as follows:

[0050] Objective function: f(x) → min;

[0051] Constraint: F ≥ S;

[0052] Design variables R1, l, O1, O2...O n O′1, O′2...O′ n n:;

[0053] In the formula, f(x) = M = f(R1, l, n);

[0054] F = g(R1, l, θ1, θ2...θ) n , θ′1, θ′2...θ′ n (n).

[0055] Where M is the weight of the repaired structure; F is the destructive load of the repaired structure; S is the destructive load of the undamaged structure; R1 is the radius of the first repair layer ply; l is the overlap length; θ1, θ2...θ n θ1, θ2...θ′ n These are the repair ply angles from layer 1 to layer n (from smallest to largest area). These repair ply angles can be the same or different. Superscripts indicate the repair ply angles on the inner panel; and the number of repair ply layers on both sides of the panel can be different. (e.g.) Figure 3 (As shown)

[0056] Next, the NSGA-II genetic algorithm is used to quickly optimize the repair scheme, specifically as follows:

[0057] Step 1: Parameter Encoding. Since integer encoding is most effective in combinatorial optimization problems, the design variables for repair optimization are set to integer encoding;

[0058] Step 2: Generate the initial population. The function rand() can be used to randomly generate integers within the interval [n_1, n_2], where n_1 and n_2 represent the upper and lower limits of the design variables, respectively.

[0059] Step 3: Fast Non-Dominated Sort. To reduce the computational complexity of repair optimization, the population is sorted based on the dominance relationships between individuals before executing the selection operator;

[0060] Step 4: Calculate congestion. To improve the convergence of repair optimization calculations, it is necessary to calculate congestion.

[0061] Step 5: Execute the selection operator. This is done so that superior individuals have a higher probability of being retained.

[0062] Step Six: Execute the crossover and mutation operators. The combined execution of the crossover and mutation operators enhances the algorithm's ability to globally and locally search for and repair optimal solutions.

[0063] Step 7: Adopt an elite strategy. An elite strategy can expand the sampling space and further ensure that excellent individuals in the parent generation are inherited by the offspring, thereby improving the accuracy of repair optimization calculations.

[0064] Subsequently, based on the rapid optimization of repair schemes using the NSGA-II genetic algorithm, the modeFRONTIER multi-objective optimization software was employed, using Python's calling functionality (e.g., `abaqus cae nogui=F:\Abz\HoneycombZ.py`) to drive the automatic modeling of the ABAQUS kernel. This, in turn, integrated and established a process for determining the repair tolerance (upper limit) of perforation damage in honeycomb sandwich structures (e.g., ...). Figure 4 As shown in the figure, the main steps are as follows:

[0065] Step 1: For the honeycomb sandwich structure with perforation damage radius R, perform ABAQUS modeling, repair model parameterization, and repair optimization analysis;

[0066] Step 2: Based on the actual dimensions and repairability of the honeycomb sandwich structure, set the upper and lower limits of the design variables, the optimization step size, and the constraints and objective function in the modeFRONTIER software;

[0067] Step 3: The modeFRONTIER software uses the uniform Latin hypercube sampling method (ULH) to select n1 (20≤n1≤100) sets of design variable values ​​as the initial sample (i.e., the initial parent generation) of the design space;

[0068] Step 4: The modeFRONTIER software writes the initial samples into the parameterized repair model implemented using the Python language, and performs batch finite element simulation calculations using the ABAQUS software kernel;

[0069] Step 5: The modeFRONTIER software reads the parent characteristics from the finite element simulation results, such as the weight M of the repaired honeycomb sandwich structure and whether it meets the constraint conditions;

[0070] Step Six: The modeFRONTIER software uses the NSGA-II genetic algorithm to perform fast non-dominated sorting, selection, crossover, mutation, and elitist strategies on the initial samples to regenerate the parent population as the initial samples for the new cycle.

[0071] Step 7: Iterate through steps 4 to 6 until the optimal repair optimization scheme for the perforation damage radius (i.e., the scheme in which the repair structure can achieve the maximum load-bearing level with the lightest weight under the premise of meeting the constraints) or the maximum load-bearing repair optimization scheme (i.e., the scheme in which the repair structure has the maximum load-bearing level under the premise of not meeting the constraints) is obtained.

[0072] Finally, a bisection method is used to change the perforation damage radius R to determine the repair tolerance (upper limit). When the repair optimization scheme meets the constraints, the perforation damage radius R is increased. If the increased perforation damage radius R still meets the constraints, it is further increased until the constraints can no longer be met. Then, the perforation damage radius R is reduced in reverse, that is, the intermediate value is taken between the minimum perforation damage radius R that does not meet the constraints and the maximum perforation damage radius R that meets the constraints. Iterative calculations are carried out (i.e., the above process of determining the repair tolerance (upper limit) is repeated sequentially) to obtain the repair optimization scheme results for different perforation damage radii R. Based on the criterion that the perforation damage radius that cannot be further increased through structural repair optimization under the premise of meeting the constraints is the upper limit of the perforation damage repair tolerance for this honeycomb sandwich structure, the final upper limit of the repair tolerance is obtained.

[0073] The key to applying this method lies in the initial assessment of the most severe load conditions that the damaged honeycomb sandwich composite structure may withstand. A process for determining the repair tolerance (upper limit) is then employed to establish the initial repair tolerance value. The optimized repair scheme under this condition is then substituted into other conditions for verification. If necessary, the repair optimization calculation is repeated. The upper limit of the structural repair tolerance is taken as the minimum value under each condition, thereby reducing the computational workload and improving the efficiency of determining the repair tolerance value.

[0074] The above description is merely a specific embodiment of the present invention, providing a detailed description of the invention. Parts not covered herein are conventional techniques. However, the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for rapidly determining the repair tolerance value of perforation damage in a honeycomb sandwich structure, characterized in that, The method includes the following steps: Step S1: Perform ABAQUS modeling of the composite honeycomb sandwich structure to obtain the repair model; Step S2: Write an ABAQUS script using Python to parameterize the repair model; Step S3: Based on achieving a 100% strength recovery rate, the repair structure weight is minimized by optimizing key parameters, resulting in an optimized mathematical model for patching and repairing honeycomb sandwich structures with perforation damage. Step S4: Use the NSGA-II genetic algorithm to quickly optimize the repair scheme; Step S5: Based on the rapid optimization of the repair scheme combined with the NSGA-II genetic algorithm, the modeFRONTIER multi-objective optimization software is used to drive the automatic modeling of the ABAQUS kernel through the calling function of the Python language, and then integrates and establishes a process to determine the upper limit of the repair tolerance for perforation damage in the honeycomb sandwich structure. Step S6: Use the bisection method to change the perforation damage radius R and determine the upper limit of the repair tolerance; The modeling process in step S1 specifically includes: Step 1: Use S4R shell elements to simulate the outer and inner panels, and use the two-dimensional Hashin criterion as the criterion for the initiation and evolution of panel damage; Step 2: Using the sandwich panel theory, the honeycomb core is equivalent to a uniform, continuous, and equally thick orthotropic anisotropic layer, and simulated with C3D8R solid elements to give it three-dimensional engineering constant properties and orientation; Step 3: Use structural adhesive film to bind and constrain the panels and honeycomb cores, as well as the laminated areas between panels; Step 4: Remove a through hole in the center of the undamaged model to simulate perforation damage with radius R; Step 5: Simulate patch repair using S4R shell unit; Step 6: Use the cohesive element interface contact simulation to repair the patch adhesive film, and use the secondary nominal stress criterion to predict the initial damage and the BK criterion to perform damage evolution analysis; Step 7: Simulate expanding foam using binding constraints; Step 8: Simulate the honeycomb core plug using C3D8R solid elements and assign it three-dimensional engineering constant properties and orientation; Step 9: First, conduct a preliminary assessment of the most severe load conditions that the damaged composite honeycomb sandwich structure may withstand, and define the corresponding boundary conditions; Step 10: Simulate and evaluate the strength of the non-destructive model to determine a baseline value for subsequent repair scheme optimization; Step 11: Simulate and evaluate the strength of the model with perforation damage and the repair model; In step S3, the key parameters include at least the size, angle, and number of repair patch layers; in step S3, the optimized mathematical model for patching and repairing honeycomb sandwich structures with perforated damage is set as follows: Objective function: ; Constraints: ; Design variables ; In the formula, ; ； Where M is the weight of the repaired structure; F is the destructive load of the repaired structure; S is the destructive load of the undamaged structure; R1 is the radius of the first repair layer ply; and l is the overlap length. These are the repair ply angles from the 1st to the nth layer, with superscripts indicating the repair ply angles on the inner panel. In step S6, when the repair optimization scheme result meets the constraint conditions, the perforation damage radius R is increased. If the increased perforation damage radius R still meets the constraint conditions, the perforation damage radius R is further increased until the constraint conditions can no longer be met. Then, the perforation damage radius R is reduced in reverse. That is, the intermediate value is taken between the minimum perforation damage radius that does not meet the constraint conditions and the maximum perforation damage radius that meets the constraint conditions. Iterative calculations are carried out to obtain the repair optimization scheme results for different perforation damage radii R. Based on the criterion that the perforation damage radius that cannot be further increased through structural repair optimization under the premise of meeting the constraint conditions is the upper limit of the perforation damage repair tolerance for the honeycomb sandwich structure, the final upper limit of the repair tolerance is obtained.

2. The method for rapidly determining the repair tolerance value of perforation damage in a honeycomb sandwich structure as described in claim 1, characterized in that, In step S2, writing the ABAQUS script using Python includes: Step S21, def Ct(self, lm, lp, lh=R): # Define function Ct() to perform preprocessing and submission calculations; Step S22, s.RadialDimension( , , radius=R1) # The geometry creation of the first repair layer radius R1 is similar to that of the overlap length l and the perforation damage radius R. Step S23, compositeLayup.CompositePly( , ,orientationValue=θn, ,) # Repair the ply angle θn in the geometric establishment of the model; Step S24, p.generateMesh() # Perform model mesh generation; Step S25, rf=region.historyOutputs['RF1'].data #Read the failure load F from the finite element simulation analysis; Step S26, ms=myodb.steps['Step-1'].mass # Read the weight M of the repair structure from the finite element simulation analysis; Step S27, def getIVal(self): # Define the function getIVal() to obtain the specific values ​​of the repair patch layup parameters in the input file; Step S28, def wrtVal(self,v): # Define the function wrtVal() to write the destructive load F and the repair structure weight M to the output file.

3. The method for rapidly determining the repair tolerance value of perforation damage in a honeycomb sandwich structure as described in claim 1, characterized in that, The NSGA-II genetic algorithm optimization process in step S4 includes, Step S41, parameter encoding: Set the design variables for repair optimization to integer encoding; Step S42: Generate the initial population. Use the function rand() to randomly generate integers in the interval [n_1, n_2], where n_1 and n_2 represent the upper and lower limits of the design variables, respectively. Step S43: Fast non-dominated sorting, which sorts the population based on the dominance relationship between individuals before executing the selection operator; Step S44: Calculate the congestion level; Step S45: Execute the selection operator; Step S46: Execute the crossover and mutation operators; Step S47: Adopt an elite strategy.

4. The method for rapidly determining the repair tolerance value of perforation damage in a honeycomb sandwich structure as described in claim 1, characterized in that, The specific execution process of step S5 is as follows: Step S51: For the honeycomb sandwich structure with perforation damage radius R, perform ABAQUS modeling, repair model parameterization, and repair optimization analysis; Step S52: Based on the actual dimensions and repairability of the honeycomb sandwich structure, set the upper and lower limits of the design variables, the optimization step size, and the constraints and objective function in the modeFRONTIER software; Step S53: The modeFRONTIER software uses the uniform Latin hypercube sampling method to select n1 sets of design variable values, where 20≤n1≤100, as the initial sample of the design space; Step S54: The modeFRONTIER software writes the initial samples into the parameterized repair model implemented using the Python language, and performs batch finite element simulation calculations using the ABAQUS software kernel; Step S55: The modeFRONTIER software reads the parent traits from the finite element simulation results; Step S56: The modeFRONTIER software uses the NSGA-II genetic algorithm to perform fast non-dominated sorting, selection, crossover, mutation, and elitist strategy on the initial samples to regenerate the parent population as the initial samples for a new round of cycling. Step S57: Iterate through steps four to six until the optimal repair optimization scheme or the maximum load-bearing repair optimization scheme for the perforation damage radius is obtained.

5. The method for rapidly determining the repair tolerance value of perforation damage in a honeycomb sandwich structure as described in claim 1, characterized in that, In step S6, the cyclic calculation is a sequential repetition of steps S4 to S6 in the process of determining the repair tolerance limit.

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