A method for predicting the compressive failure load of a composite stiffened panel in an aircraft structure

Abstract

The application belongs to the technical field of aircraft structure design, and particularly relates to a method for predicting compression failure load of a composite stiffened panel in an aircraft structure, comprising the following steps: Step 1, screening important related parameters related to compression failure of the composite stiffened panel; Step 2, determining the value range of the important related parameters, sampling and constructing a simulation sample set; Step 3, constructing a finite element model of the composite stiffened panel, and calculating the compression failure load of each sample in the simulation sample set; Step 4, collecting test samples of the existing composite stiffened panel compression failure, and constructing a test sample set; Step 5, based on each sample in the simulation sample set and the test sample set and the corresponding compression failure load, constructing a composite stiffened panel compression failure load prediction model; and Step 6, taking the important related parameters as input, and based on the composite stiffened panel compression failure load prediction model, calculating the compression failure load of the composite stiffened panel.

Description

Technical Field

[0001] This application belongs to the field of aircraft structural design technology, specifically relating to a method for predicting the compressive failure load of composite stiffening plates in aircraft structures. Background Technology

[0002] Composite stiffened plates are used as key load-bearing components in aircraft structures such as fuselages and wings, bearing and transmitting compressive, bending and torsional loads. Among these, compressive load is the most significant factor leading to the failure of composite stiffened plates.

[0003] The failure modes of composite stiffeners in aircraft structures are complex, typically including instability, laminate material failure, and interface debonding. Taking fuselage panels as an example, these are thin-walled stiffened structures. Under axial pressure, the skin buckles first, and the subsequent load is shared by the unbuckled stringers and surrounding skin, eventually leading to overall instability and failure. Failure of composite stiffeners can cause severe stress concentration, significantly increasing the load on other components, shortening aircraft lifespan, and even causing disintegration, posing a threat to flight safety.

[0004] Efficient and accurate analysis of the compressive failure behavior of composite stiffened plates is of great significance for promoting their application in aircraft structures. Currently, in aircraft structural design, engineering estimation methods and finite element simulation methods are commonly used to predict the compressive failure load of composite stiffened plates.

[0005] Engineering estimation methods originated in early aircraft design. They primarily rely on engineering manuals and empirical formulas, summarizing key characteristics based on historical data and combining experimental data to construct empirical models for estimation, predicting the compressive failure load of composite stiffened plates. While engineering estimation methods have low computational resource requirements and are easy to use, their accuracy is highly dependent on continuously revised historical experimental data, resulting in long cycles, high costs, insufficient cross-scenario adaptability, and the neglect of anisotropy and simplification of damage evolution to represent the complex behavior of composite materials. Furthermore, they cannot demonstrate the damage evolution of composite stiffened plates, making them unsuitable for the rapid iterative design requirements of aircraft structures.

[0006] Finite element simulation can accurately simulate the entire process of load response and failure of composite stiffened plates through mesh generation and parameter setting. However, the multi-scale characteristics and anisotropy of composite materials significantly increase the complexity of finite element simulation modeling. The construction and calculation of high-fidelity models require professional personnel. For the prediction of compressive failure loads of large-scale composite stiffened plates, the calculation of detailed finite element simulation models requires a lot of computing resources, resulting in high computing costs and long calculation cycles. This also makes it difficult to meet the needs of rapid iterative design of aircraft structures.

[0007] This application is made in view of the aforementioned technical deficiencies. Summary of the Invention

[0008] The purpose of this application is to provide a method for predicting the compressive failure load of composite stiffened plates in aircraft structures, so as to quickly and accurately predict the compressive failure load of composite stiffened plates and effectively support the rapid iterative design of aircraft structures.

[0009] The technical solution of this application is:

[0010] A method for predicting the compressive failure load of composite stiffening plates in aircraft structures includes:

[0011] Step 1: Screen out the key relevant parameters associated with compressive failure of composite stiffened plates;

[0012] Step 2: Determine the value range of important relevant parameters, perform sampling, and construct a simulation sample set;

[0013] Step 3: Construct a finite element model of the composite stiffened plate and calculate the compressive failure load of each sample in the simulation sample set;

[0014] Step 4: Collect existing test samples of composite stiffened plates under compression failure and construct a test sample set;

[0015] Step 5: Based on each sample in the simulation sample set and the experimental sample set, and their corresponding compressive failure loads, construct a compressive failure load prediction model for composite stiffened plates;

[0016] Step 6: Using key relevant parameters as input, calculate the compressive failure load of the composite stiffened plate based on the composite stiffened plate compression failure load prediction model.

[0017] Optionally, in the above-mentioned method for predicting the compressive failure load of composite stiffened plates in aircraft structures, step one involves screening out important relevant parameters associated with the compressive failure of the composite stiffened plates, including the tensile stiffness in the direction of the stiffeners within the plate surface. Tensile stiffness in the direction perpendicular to the stiffeners within the plate surface The ratio of the tensile stiffness of the inner stiffeners to the tensile stiffness perpendicular to the stiffeners. Section modulus of stiffeners Bending stiffness of the skin in the direction perpendicular to the stiffeners The ratio of the section modulus of the stiffener to the bending stiffness of the skin in the direction perpendicular to the stiffener. In-plane tensile / compressive modulus of elasticity of ribs In-plane tensile / compressive elastic modulus of skin The elastic modulus of tension / compression in the equivalent plane of the ribs and skin , width of the skin Width of the lower edge strip Width of the web Width of the upper edge strip Number of reinforcing bars and the length of the reinforcing bars .

[0018] Optionally, in the above-mentioned method for predicting the compressive failure load of composite stiffening plates in aircraft structures, step five involves constructing a model for predicting the compressive failure load of composite stiffening plates based on an artificial neural network.

[0019] Optionally, in the above-mentioned method for predicting the compressive failure load of composite stiffening plates in aircraft structures, in step five, four sets of samples are randomly selected from the test sample set and twelve sets of samples are randomly selected from the simulation sample set, and a test set is constructed using the selected samples and their corresponding compressive failure loads.

[0020] A training set is constructed using the remaining samples from the experimental sample set and the simulation sample set, and their corresponding compressive failure loads.

[0021] The model for predicting the compressive failure load of composite stiffened plates was trained using training set data, and tested using test set data.

[0022] Optionally, in the above-mentioned method for predicting the compressive failure load of composite stiffened plates in aircraft structures, step five uses mean square error, coefficient of determination, average error percentage, and maximum error percentage as indicators to evaluate the performance of the composite stiffened plate compressive failure load prediction model.

[0023] Optionally, in the above-mentioned method for predicting the compressive failure load of composite stiffening plates in aircraft structures, step five involves using a grid search method or a neural architecture search method to optimize and iterate the prediction model for the compressive failure load of composite stiffening plates until the predetermined accuracy requirements are met.

[0024] This application has at least the following beneficial technical effects:

[0025] This paper presents a method for predicting the compressive failure load of composite stiffened plates in aircraft structures. By integrating finite element simulation data and physical test data, a high-precision and high-efficiency model for predicting the compressive failure load of composite stiffened plates is constructed. This model can be used to predict the compressive failure load of composite stiffened plates while ensuring prediction accuracy. It can effectively support the rapid iterative design of aircraft structures. Attached Figure Description

[0026] Figure 1 This is a flowchart of the method for predicting the compressive failure load of composite stiffening plates in aircraft structures provided in this application embodiment;

[0027] Figure 2This is a top view of the composite material stiffened plate provided in the embodiments of this application;

[0028] Figure 3 This is a cross-sectional view of the composite material stiffened plate provided in the embodiments of this application.

[0029] 1-Skin; 2-Firming strip; 3-Upper edge strip; 4-Body plate; 5-Lower edge strip.

[0030] To better illustrate this embodiment, some content in the accompanying drawings may be omitted, enlarged, or reduced. They are for illustrative purposes only and should not be construed as limiting the scope of this application. Detailed Implementation

[0031] To make the technical solution and advantages of this application clearer, the technical solution of this application will be described in a clearer and more complete manner below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of this application, and are only used to explain this application, not to limit this application. It should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings, and other related parts can be referred to the general design.

[0032] Furthermore, unless otherwise defined, the technical or scientific terms used in this application description shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The word "comprising" as used in this application description indicates that the concept preceding the word encompasses the concepts listed following the word and their equivalents, without excluding other related concepts.

[0033] A method for predicting compressive failure load of composite stiffened plates in aircraft structures, such as Figure 1 As shown.

[0034] Step 1: Screen out the important relevant parameters associated with the compressive failure of composite stiffened plates.

[0035] Determine the configuration of the composite stiffened plate, such as Figure 1-2 As shown, it includes a skin 1 and a rib 2, wherein the rib 2 further includes an upper edge strip 3, a web 4, and a lower edge strip 5, and the material is CCF300.

[0036] Based on mechanical analysis and empirical formulas, correlation analysis using the mutual information method was employed to generate a correlation heatmap. Parameters with the highest correlation to compressive failure of composite stiffened plates were selected as key correlation parameters, including the tensile stiffness in the direction of the inner stiffeners. Tensile stiffness in the direction perpendicular to the stiffeners within the plate surface The ratio of the tensile stiffness of the inner stiffeners to the tensile stiffness perpendicular to the stiffeners. Section modulus of stiffeners Bending stiffness of the skin in the direction perpendicular to the stiffeners The ratio of the section modulus of the stiffener to the bending stiffness of the skin in the direction perpendicular to the stiffener. In-plane tensile / compressive modulus of elasticity of ribs In-plane tensile / compressive elastic modulus of skin The elastic modulus of tension / compression in the equivalent plane of the ribs and skin , width of the skin Width of the lower edge strip Width of the web Width of the upper edge strip Number of reinforcing bars and the length of the reinforcing bars .

[0037] Step 2: Determine the value range of important relevant parameters, perform sampling, and construct a simulation sample set.

[0038] Collect parameter information of composite stiffening plates in aircraft structures, determine the value range of important relevant parameters, perform sampling, and construct a simulation sample set.

[0039] Can Take a fixed value, Take 1~4, and... , , , , , , , , Take the numerical values ​​corresponding to the four layup sequences of the composite material. , , , Ten discrete values ​​were selected, and orthogonal experimental design was used to sample them, resulting in 1904 samples, which were then used to construct a simulation sample set.

[0040] Step 3: Construct a finite element model of the composite stiffened plate and calculate the compressive failure load of each sample in the simulation sample set.

[0041] Referring to existing physical test specimens of composite stiffened plates, a finite element model is constructed to ensure that the details of the finite element model meet the analysis requirements, including the structural shape, internal structure, and connection parts. Axial compression tests are conducted on the physical test specimens, and simulation calculations are performed based on the finite element model. The axial compression test results are compared with the simulation calculation results, the parameters of the finite element model are adjusted, and the finite element model is calibrated to ensure that the calculation accuracy of the finite element model meets the analysis requirements.

[0042] Based on the parameterization method, the finite element model corresponding to each sample in the simulation sample set is constructed in batches, and the compressive failure load of each sample is calculated. The compressive failure load mentioned here is the compressive load when the composite stiffened plate fails initially.

[0043] Step 4: Collect existing test samples of composite stiffened plates under compression failure and construct a test sample set.

[0044] Collect test samples of composite stiffened plates under compression failure from publicly available literature and testing units, construct a test sample set, and record the important relevant parameters and compression failure load of each sample.

[0045] Step 5: Based on each sample in the simulation sample set and the experimental sample set, and their corresponding compressive failure loads, construct a compressive failure load prediction model for composite stiffened plates.

[0046] Artificial neural network models, through regularization techniques such as Dropout and L2 regularization, and feature dimensionality reduction techniques such as autoencoders, suppress the curse of dimensionality and possess efficient processing capabilities for high-dimensional inputs. Furthermore, through nonlinear activation functions such as ReLU, Sigmoid, and TanH, and multi-layer network structures, they can capture the complex nonlinear relationships between input and output. Based on the characteristics of the task of predicting the compressive failure load of composite stiffened plates and the applicability of various regression models, an artificial neural network-based model for predicting the compressive failure load of composite stiffened plates is chosen.

[0047] Since there are few test samples of composite stiffened plates that meet the requirements for compression failure, the test sample set cannot independently support the construction of a compression failure load prediction model for composite stiffened plates. Therefore, in this application, a finite element model of composite stiffened plates is constructed, and the compression failure load of each sample in the simulation sample set is calculated to construct a compression failure load prediction model for composite stiffened plates.

[0048] Due to the significant difference in sample size between the experimental and simulation sample sets, the following design is proposed to provide sufficient information for constructing a compressive failure load prediction model for composite stiffened plates, and to fully utilize experimental sample data to refine the model and improve its applicability:

[0049] Z-Score normalization was used to preprocess each sample in the simulation sample set and the experimental sample set, as well as their corresponding compressive failure load data.

[0050] Four sets of samples were randomly selected from the experimental sample set and twelve sets of samples were randomly selected from the simulation sample set. The selected samples and their corresponding compressive failure loads were used to construct a test set.

[0051] A training set is constructed using the remaining samples from the experimental sample set and the simulation sample set, and their corresponding compressive failure loads.

[0052] The model for predicting the compressive failure load of composite stiffened plates was trained using training set data, and tested using test set data.

[0053] Since the prediction of compressive failure load of composite stiffened plates is a regression task, the mean square error, coefficient of determination, average error percentage, and maximum error percentage are selected as indicators to evaluate the performance of the composite stiffened plate compressive failure load prediction model.

[0054] An acceptable accuracy range can be set according to the requirements of aircraft structural design. The prediction model of compressive failure load of composite stiffened plate can be optimized and iterated by grid search method or neural architecture search method until the predetermined accuracy requirements are met.

[0055] In a specific example, the constructed composite stiffened plate compression failure load prediction model has an average error percentage of less than 5% for the test set.

[0056] Step 6: Using key relevant parameters as input, calculate the compressive failure load of the composite stiffened plate based on the composite stiffened plate compression failure load prediction model.

[0057] After completing the construction of the composite stiffened plate compression failure load prediction model, you only need to input the important relevant parameter values ​​of the composite stiffened plate into the composite stiffened plate compression failure load prediction model to quickly calculate the compression failure load of the composite stiffened plate. Moreover, the composite stiffened plate compression failure load prediction model can be continuously iterated and optimized as needed, and can be reused.

[0058] The method for predicting the compressive failure load of composite stiffening plates in aircraft structures disclosed in the above embodiments, by integrating finite element simulation data and physical test data, constructs a high-precision and high-efficiency model for predicting the compressive failure load of composite stiffening plates. This model can effectively support the rapid iterative design of aircraft structures while ensuring prediction accuracy.

[0059] The technical solution of this application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. A method of predicting the compressive failure load of a composite stiffened panel in an aircraft structure, characterised in that, The method comprises the following steps: Step one, screen out important related parameters related to the compression failure of the composite stiffened plate; Step two, determine the value range of the important related parameters, sample and construct the simulation sample set; Step three, construct the finite element model of the composite stiffened plate, and calculate the compression failure load of each sample in the simulation sample set; Step four, collect the existing test samples of the compression failure of the composite stiffened plate, and construct the test sample set; Step five, based on each sample in the simulation sample set and the test sample set, and the corresponding compression failure load, construct the compression failure load prediction model of the composite stiffened plate; Step six, taking the important related parameters as input, based on the compression failure load prediction model of the composite stiffened plate, calculate the compression failure load of the composite stiffened plate; In step five, the compression failure load prediction model of the composite stiffened plate is constructed based on artificial neural network.

2. The method of predicting the compressive failure load of a composite stiffened panel in an aircraft structure according to claim 1, wherein, In step one, key parameters related to compressive failure of composite stiffened plates are identified, including the tensile stiffness in the direction of the stiffeners within the plate surface. Tensile stiffness in the direction perpendicular to the stiffeners within the plate surface The ratio of the tensile stiffness of the inner stiffeners to the tensile stiffness perpendicular to the stiffeners. Section modulus of stiffeners Bending stiffness of the skin in the direction perpendicular to the stiffeners The ratio of the section modulus of the stiffener to the bending stiffness of the skin in the direction perpendicular to the stiffener. In-plane tensile / compressive modulus of elasticity of ribs In-plane tensile / compressive elastic modulus of skin The elastic modulus of tension / compression in the equivalent plane of the ribs and skin , width of the skin Width of the lower edge strip Width of the web Width of the upper edge strip Number of reinforcing bars and the length of the reinforcing bars .

3. The method of predicting the compressive failure load of a composite stiffened panel in an aircraft structure according to claim 2, wherein, In step five, 4 groups of samples are randomly selected from the test sample set, and 12 groups of samples are randomly selected from the simulation sample set, and the selected samples and the corresponding compression failure load are used to construct the test set; The remaining samples in the test sample set and the simulation sample set, and the corresponding compression failure load are used to construct the training set; The compression failure load prediction model of the composite stiffened plate is trained by using the training set data, and is tested by using the test set data.

4. The method of predicting the compressive failure load of a composite stiffened panel in an aircraft structure according to claim 3, wherein, In step five, the mean square error, the determination coefficient, the average error percentage and the maximum error percentage are selected as indexes to evaluate the performance of the compression failure load prediction model of the composite stiffened plate.

5. The method of predicting the compressive failure load of a composite stiffened panel in an aircraft structure according to claim 4, wherein, In step five, the grid search method or the neural architecture search method is adopted to optimize and iterate the compression failure load prediction model of the composite stiffened plate until the predetermined precision requirement is met.

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