Bearing and manufacturing integrated design method for asymmetric variable-stiffness carbon fiber laminated plate

Abstract

The invention discloses a bearing and manufacturing integrated design method of an asymmetric variable stiffness carbon fiber laminated plate. According to stretching-bending, stretching-shearing and bending-shearing coupling deformation characteristics caused by asymmetric layering, an in-plane and out-of-plane coupling stiffness matrix is introduced in the material modeling process, and the influence of the coupling effect is considered. In addition, in order to effectively describe the influence of the direction change of fibers in each layer in the variable stiffness composite material, the local fiber angle of each layer is defined at the design point of the analysis model. In the analysis model, the material rigidity characteristic in a local area is calculated through multiple feasible interpolation methods according to the material rigidity at the design point, and the mechanical characteristic of the asymmetric variable-rigidity laminated plate can be effectively represented.

Description

Technical Field

[0001] The present invention belongs to the field of material structure optimization, and more specifically, relates to a load-bearing manufacturing integrated design method for an asymmetric variable-rigidity carbon fiber laminate. Background Art

[0002] In the field of aerospace, carbon fiber composite materials have made significant contributions to the lightweighting of fuselage structures due to their excellent specific strength and specific stiffness. Since any potential failure in the fuselage due to structural strength failure may lead to a huge disaster, strength is an important factor to be considered in the optimization design of lightweight composite structures.

[0003] Asymmetric laminate composite structures have relatively complex tensile-bending, tensile-shear, and bending-shear coupled deformation characteristics. In order to avoid abnormal responses caused by such coupled deformations, aerospace structures often use symmetrical laminated composite structures. Existing research results and design methods are only applicable to composite structures that are symmetrical relative to the neutral plane. However, the coupled deformation effect of asymmetric laminates can be used for stress redistribution design under extreme load conditions (such as stress concentration), thereby indirectly improving the ultimate bearing capacity of composite structures. At present, there is a lack of strength optimization design methods for asymmetric laminated carbon fiber structures. The strength optimization design of this type of composite structure is a new challenge to improve the ultimate bearing capacity of lightweight aerospace structures.

[0004] In recent years, the research on the optimization design of composite materials for fiber placement manufacturing technology has gradually deepened, and a variable angle placement path design method suitable for improving strength has been proposed. The existing method can be used to design a fiber variable angle placement path that is symmetrical relative to the neutral plane. However, there is still a blank in the research on the design of variable stiffness carbon fiber plies for asymmetric plies. Mechanical simulation results show that with the coupled deformation of tension-bending, tension-shear, and bending-shear, asymmetric composite structures can improve the structural bearing capacity of aviation structures under extreme load conditions.

[0005] Although the existing gradient-based and data-driven variable stiffness composite design methods have laid a theoretical foundation for the design of symmetric variable stiffness composites, there are still three numerical method problems for the design of asymmetric variable stiffness composite structures: 1) There is a lack of structural modeling methods that effectively characterize the mechanical properties of asymmetric variable stiffness composites; 2) There is a lack of strength criterion models that consider the coupled deformation effects of asymmetric carbon fiber composite structures in iterative optimization calculations; 3) There is a need to build a load-bearing manufacturing integrated design method framework suitable for asymmetric variable stiffness composite structures. The above problems limit the potential design capabilities for fully exploring the strength optimization of asymmetric variable stiffness composite structures. Summary of the invention

[0006] In view of the defects of the prior art and the need for improvement, the present invention provides an integrated load-bearing manufacturing design method for asymmetric variable stiffness carbon fiber laminates, with the aim of constructing a complete design method framework suitable for strength optimization of asymmetric variable stiffness composite materials, and applying it to actual aviation structure design, thereby improving the ultimate load-bearing capacity of aviation structures by integrating coupled deformation effects.

[0007] To achieve the above objectives, the present invention provides, in a first aspect, a load-bearing manufacturing integrated design method for an asymmetric variable stiffness carbon fiber laminate, comprising:

[0008] S1. Based on the composite laminate theory and combined with the interpolation method, three types of matrices are established to characterize the material properties of asymmetric variable stiffness laminates. The deformation coupling effects of stretching-bending, stretching-shearing, and bending-shearing are considered in the material modeling process.

[0009] S2. Perform structural mechanics analysis on variable stiffness laminate structures based on mechanical methods (e.g., finite element plate and shell theory), and consider the above-mentioned deformation coupling effect in the structural model;

[0010] S3. Construct material failure criteria suitable for iterative optimization of asymmetric carbon fiber laminate structures, construct strain-based strength failure envelopes based on conventional failure criteria (such as Tsai-Wu criteria), verify the structural strength of carbon fiber laminates by calculating the corresponding strength failure factors, and calculate the global strength failure factors that characterize the laminate structure by aggregation methods (such as p-norm function) to simplify strength verification;

[0011] S4. Construct a strength optimization model for calculating the fiber distribution in each ply of an asymmetric variable stiffness laminate structure. To avoid manufacturing defects caused by variable angle fiber placement, add constraints related to key manufacturing indicators to ensure the manufacturability of the optimal variable stiffness fiber angle distribution.

[0012] S5. Conduct sensitivity analysis of strength failure coefficient, establish approximate calculation of strength optimization objective function and manufacturing constraints, use gradient-based optimization method to optimize the fiber angle distribution in each layer, and obtain the optimal fiber angle distribution under manufacturing constraints;

[0013] S6. Construct the fiber placement path in each ply by using the flow potential function or spline construction method and combining the optimal fiber angle distribution in each ply.

[0014] The second aspect of the present invention provides a load-bearing manufacturing integrated design system for an asymmetric variable stiffness carbon fiber laminate, comprising:

[0015] Material modeling module, which is used to establish three types of matrices to characterize the material properties of asymmetric variable stiffness laminates based on composite laminate theory and combined with interpolation methods;

[0016] Structural mechanics analysis module, used to perform structural mechanics analysis of variable stiffness laminate structures based on mechanical methods;

[0017] Strength failure criterion building module, used to build material failure criteria suitable for iterative optimization of asymmetric carbon fiber laminate structures;

[0018] A strength optimization model building module is used to build a strength optimization model for calculating the fiber distribution in each ply of an asymmetric variable stiffness laminate structure;

[0019] The optimization calculation module is used to carry out sensitivity analysis of the strength failure coefficient, establish approximate calculations of the strength optimization objective function and manufacturing constraints, and use a gradient-based optimization method to optimize the fiber angle distribution within each layer;

[0020] The fiber placement path construction module is used to construct the fiber placement path in each ply by combining the optimal fiber angle distribution in each ply through the flow potential function or spline construction method.

[0021] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the load-bearing manufacturing integrated design method of the asymmetric variable-rigidity carbon fiber laminate is implemented.

[0022] A fourth aspect of the present invention provides a load-bearing manufacturing integrated design device for an asymmetric variable stiffness carbon fiber laminate, comprising:

[0023] Memory for storing computer programs;

[0024] A processor, configured to execute the computer program to implement the load-bearing manufacturing integrated design method for the asymmetric variable stiffness carbon fiber laminate;

[0025] An input module, used for receiving initial layup parameters of composite materials, material mechanical property parameters and design constraints;

[0026] An output module is used to output the optimized fiber layer angle distribution and the corresponding fiber placement path;

[0027] The device executes a computer program in a memory through a processor, combines the parameters and constraints received by an input module, performs calculations and optimizations according to the steps of the method, and provides optimization results through an output module, thereby realizing a load-bearing manufacturing integrated design method for asymmetric variable stiffness carbon fiber laminates.

[0028] The above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0029] (1) The present invention provides a modeling and analysis method for asymmetric variable stiffness laminate structures. In view of the tensile-bending, tensile-shearing, and bending-shearing coupled deformation characteristics caused by asymmetric ply, an in-plane and out-of-plane coupling stiffness matrix is ​​introduced in the material modeling process. , considering the influence of the above coupling effect. In addition, in order to effectively describe the influence of the change of fiber direction in each ply in the variable stiffness composite material, the local fiber angle of each ply is defined at the design point of the analysis model. In the analysis model, the material stiffness characteristics in the local area are calculated by a variety of feasible interpolation methods of the material stiffness at the design point, which can effectively characterize the mechanical properties of the asymmetric variable stiffness laminate.

[0030] (2) The present invention also provides a strength verification method suitable for iterative optimization of asymmetric variable stiffness laminate structure performance. Aiming at the tensile-bending, tensile-shearing, and bending-shearing coupled deformation characteristics caused by asymmetric ply, a strain-based Tsai-Wu failure criterion method is designed. By verifying the strength of the composite material structure through the strain field, the fiber angle can be effectively avoided. The distortion of the stress field approximation during the iteration process. On this basis, a method that satisfies any fiber angle is constructed. The conservative failure envelope of the composite material is obtained by simplifies the complicated process of Tsai-Wu failure criterion which requires individual verification and calculation of each ply, and further simplifies the strength calculation by aggregation of failure factors.

[0031] (3) The present invention also provides a load-bearing manufacturing integrated method framework applicable to asymmetric variable stiffness laminate structures. In the optimization modeling process, the approximate model constructed for the global strength failure factor takes into account the coupled deformation effect of the asymmetric composite structure, and minimizes the global strength failure factor. In addition, in order to control defects such as fiber wrinkles, fiber gaps, and overlaps caused by variable angle fiber placement, a constraint strategy for controlling the curvature and parallelism of fibers in each layer is added to the optimization model; while improving the structural strength, it reduces the defects that may be introduced by the variable angle design; and for manufacturing constraints, a feasible implementation method is pointed out to ensure the manufacturability of the optimal design. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A flow chart of a load-bearing manufacturing integrated design method for an asymmetric variable-rigidity carbon fiber laminate provided by an embodiment of the present invention;

[0033] Figure 2 A schematic diagram of local material performance modeling and calculation for mechanical analysis of asymmetric variable stiffness laminates provided in an embodiment of the present invention;

[0034] Figure 3 (a) shows the composite material structure to be optimized;

[0035] Figure 3 (b) shows the strength failure factor distribution of the L-shaped plate;

[0036] Figure 3 (c) shows the path distribution after optimization;

[0037] Figure 3 (d) shows the strength failure factor distribution corresponding to the final result. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0039] The present application provides a load-bearing manufacturing integrated design method for asymmetric variable stiffness carbon fiber laminates, the process of which is as follows: Figure 1 As shown, the following steps are included:

[0040] Step S1, based on the composite laminate theory and combined with the interpolation method, the A, B, and D matrices characterizing the material performance of the asymmetric variable stiffness laminate are established, and the deformation coupling effects of stretching-bending, stretching-shearing, and bending-shearing are considered in the material modeling process.

[0041] Further, the implementation of step S1 includes:

[0042] S1.1. The material properties of asymmetric variable stiffness laminates are modeled using composite laminate theory to obtain the material constitutive model of asymmetric variable stiffness laminates:

[0043]

[0044] In the formula, Indicates along The internal force in the plane of Indicates along The internal force in the plane of Indicates perpendicular to Inner edge of the axis Plane shear force in the direction; Indicates winding Out-of-plane bending moment of the shaft, Indicates winding Out-of-plane bending moment of the shaft, Represents the torque caused by shear stress; Indicates the neutral plane edge The plane strain in the direction, Indicates the neutral plane edge The plane strain in the direction, represents the in-plane shear strain in the neutral plane; Indicates neutral plane winding The outer curvature of the axis, Indicates neutral plane winding The outer curvature of the axis, represents the torsional curvature of the neutral plane; ( ) represent the internal forces in the material plane With plane strain The in-plane modulus of Indicates the internal force of the material Out-of-plane curvature The coupling modulus of Out-of-plane bending moment Out-of-plane curvature Flexural modulus.

[0045] Depend on That is, we get the A matrix that characterizes the in-plane performance of the material. That is, the B matrix that characterizes the in-plane and out-of-plane coupling effects of the material is obtained, which is That is, the D matrix characterizing the out-of-plane bending performance of the material is obtained. Among them, the B matrix is ​​the key to characterizing the tensile-bending deformation coupling effect of asymmetric laminated composite materials and cannot be ignored in the modeling process.

[0046] Further, the implementation of step S2 includes:

[0047] S2.1. The finite element method is used to discretize the asymmetric variable stiffness laminate structure. In order to characterize the material mechanical properties of the variable stiffness carbon fiber laminate in each unit, it can be achieved in two ways, such as Figure 2 As shown:

[0048] First, the fiber angle representing the fiber laying direction is defined independently in each unit, and the calculation of any unit is performed separately. In-plane, in-plane-out-of-plane coupling, out-of-plane stiffness matrix , , ;

[0049] Second, define the fiber angle representing the fiber laying direction at the node of each unit, and calculate the A, B, and D matrices at the node and the stiffness matrix within the unit , , By interpolation calculation, such as:

[0050] or

[0051] In the formula, Indicates The A matrix of nodes, Represents the total number of nodes in the unit. The corresponding interpolation method is also applicable to Calculation.

[0052] for Matrix calculations use linear interpolation:

[0053]

[0054] S2.2, in order to realize the mechanical analysis of asymmetric variable stiffness laminate structure, based on S2.1 , , Matrix, combined with plate and shell theory to construct the stiffness matrix of each unit , assemble the overall stiffness matrix K according to the degrees of freedom of each node, and the structural displacement field It can be obtained by solving the equilibrium equation: ; By solving the displacement field of the structure , and then calculate the strain of the structure In the formula, is the external force vector on the model. Based on the above model, the structural analysis of the asymmetric variable stiffness laminate is realized.

[0055] Further, the implementation of step S3 includes:

[0056] S3.1. Use the Tsai-Wu failure criterion of composite materials to check the strength of composite structures. Due to the coupled mechanical properties of stretch-bend, stretch-shear, and bend-shear of asymmetric plies, the Tsai-Wu failure criterion is rewritten as a strain-based strength criterion:

[0057] ,

[0058] In the formula, the coefficient is the material property parameter, is the strain along the fiber direction, represents the strain perpendicular to the fiber direction, Represents the shear strain in the ply coordinate system, which needs to be converted into the strain in the structural reference coordinate system during the calculation process (Same as strain in material constitutive );

[0059] S3.2. To ensure that the above failure criteria are applicable to each ply in the thickness direction, a conservative failure envelope is constructed. The derivation method can be obtained by calculating the strain-based Tsai-Wu failure criterion Fiber Angle The partial derivative of is set to its extreme value:

[0060] ;

[0061] The above formula can be used to derive the conservative failure envelope that satisfies any ply direction and the corresponding strength failure factor: ( Indicates that the material does not fail); based on the conservative failure envelope, only one strength failure factor is used The strength of each ply in the local thickness direction can be checked.

[0062] S3.3. Due to the coupled deformation of the asymmetric laminate structure, the strength failure factor is calculated in the above formula. When To fully consider the out-of-plane bending effect:

[0063] ,

[0064] In the formula, is the thickness of the laminate;

[0065] S3.4. To further simplify the strength check calculation, use an aggregation method (such as the p-norm function) to convert the local strength failure factor Aggregate to obtain the global strength failure factor .

[0066] Further, the implementation of step S4 includes:

[0067] S4.1. Construct variable stiffness composite manufacturing constraints: For variable angle layup of composite structures, if the curvature of the layup path is too large, fiber wrinkle defects are likely to occur. To avoid wrinkle defects in the laid structure, the curvature of the layup path needs to be constrained.

[0068] The curvature calculation of the placement path can be characterized by the gradient of the fiber angle in the finite element analysis model, for example, by calculating the gradient of the fiber direction angle in each unit:

[0069]

[0070] In the formula, represents the path direction gradient calculated from the fiber distribution in each unit, and represents the spatial coordinates, when When the value is less than the upper limit of the permissible gradient, the fiber path meets the curvature requirement;

[0071] S4.2. To avoid fiber overlap or gaps between placement paths, it is necessary to estimate and constrain the parallelism of the placement paths. The parallelism can be characterized by the divergence of the fiber direction. The calculation method can also be performed by calculating the fiber path direction in each unit. The corresponding divergence is calculated:

[0072]

[0073] In the formula, and represents the spatial coordinates, when When , it indicates fiber overlap; when If the overlap or gap of the fibers is expected to be within the allowable range, then control The upper and lower bounds of are within the given range.

[0074] Further, the implementation of step S5 includes:

[0075] S5.1. Constructing global strength failure factor for asymmetric variable stiffness carbon fiber laminates Approximate model of For example, the approximate polynomial can be constructed using the series method. The construction of the approximate model first requires the calculation of the global strength failure factor For each design point in the ply Fiber direction at sensitivity.

[0076] Based on S3.1, since the strain-based Tsai-Wu failure criterion is used for asymmetric variable stiffness carbon fiber laminates, the sensitivity should be calculated Relative to Sensitivity :

[0077] ,

[0078] On this basis, we can obtain For any Sensitivity:

[0079] ,

[0080] Then, an approximate model can be constructed by the series method. ;

[0081] S5.2. Global Strength Failure Factor With minimization as the goal, and the feasible domain of fiber angles and parameter indicators for reducing manufacturing defects of variable angle placement as constraints, the following optimization model is constructed:

[0082]

[0083] in, is the total number of design nodes, is the total number of units, is the number of design layers, and are the upper and lower bounds of the fiber angle, Indicates each unit Neidi The fiber curvature of the layer is used to avoid fiber wrinkles, Representation unit Neidi The fiber parallelism of the layer is used to control the gap and overlap between fibers. represents the maximum allowable fiber curvature, In the above formula, the fiber angle of the design point in each ply is changed. Reduce the global strength failure factor ; By considering the fiber curvature in each local area , and fiber divergence ; Ensure the optimal design while improving structural strength and reducing fiber wrinkles, gaps and overlap defects in the placement path.

[0084] Further, the implementation of step S6 includes:

[0085] S6.1. Based on the results of the optimal fiber angle, the flow potential function is used to construct the reference path for laying:

[0086] Numerical calculation of key parameter variables caused by fiber orientation changes, such as fiber thickness caused by fiber orientation deflection The change of represents the influence of angle on physical quantity;

[0087] S6.2, through thickness The flow function corresponding to the fiber ply at each local position can be calculated ,For example:

[0088] ;

[0089] Finally, the calculated (in, Indicates that in a local area and The calculated potential function value) is the same The corresponding design point coordinates are connected to obtain the reference line of the variable stiffness placement path. Since the fiber angles in all layers are used as design variables, the optimal design will form an asymmetric variable stiffness laminate structure. This completes the load-bearing manufacturing integrated design method of asymmetric variable stiffness carbon fiber laminates.

[0090] Based on the same concept as the above method, the embodiment of the present application also provides a load-bearing manufacturing integrated design system for an asymmetric variable stiffness carbon fiber laminate, including:

[0091] Material modeling module, which is used to establish A, B, and D matrices to characterize the material performance of asymmetric variable stiffness laminates based on composite laminate theory and combined with interpolation methods;

[0092] Structural mechanics analysis module, used to perform structural mechanics analysis of variable stiffness laminate structures based on mechanical methods;

[0093] Strength failure criterion building module, used to build material failure criteria suitable for iterative optimization of asymmetric carbon fiber laminate structures;

[0094] A strength optimization model building module is used to build a strength optimization model for calculating the fiber distribution in each ply of an asymmetric variable stiffness laminate structure;

[0095] The optimization calculation module is used to carry out sensitivity analysis of the strength failure coefficient, establish approximate calculations of the strength optimization objective function and manufacturing constraints, and use a gradient-based optimization method to optimize the fiber angle distribution within each layer;

[0096] The fiber placement path construction module is used to construct the fiber placement path in each ply by combining the optimal fiber angle distribution in each ply through the flow potential function or spline construction method.

[0097] Based on the same concept as the above method, an embodiment of the present application also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the load-bearing manufacturing integrated design method of the asymmetric variable stiffness carbon fiber laminate is implemented.

[0098] Based on the same concept as the above method, the embodiment of the present application also provides an integrated design device for load-bearing manufacturing of an asymmetric variable stiffness carbon fiber laminate, including:

[0099] Memory for storing computer programs;

[0100] A processor, configured to execute the computer program to implement the load-bearing manufacturing integrated design method for the asymmetric variable stiffness carbon fiber laminate;

[0101] An input module, used for receiving initial layup parameters of composite materials, material mechanical property parameters and design constraints;

[0102] An output module is used to output the optimized fiber layer angle distribution and the corresponding fiber placement path;

[0103] The device executes a computer program in a memory through a processor, combines the parameters and constraints received by an input module, performs calculations and optimizations according to the steps of the method, and provides optimization results through an output module, thereby realizing a load-bearing manufacturing integrated design method for asymmetric variable stiffness carbon fiber laminates.

[0104] Example: The design domain of the composite material structure to be optimized is an L-shaped plate structure. The top of the plate is fixed and a downward shear load is applied to the lower right corner. The structure setting contains 12 design plies. The initial ply directions at each design point are: [0, 36, 72, 108, 144, 180] s, as shown in FIG3 (a).

[0105] According to the method of this application, before optimization, under given working conditions, the strength failure factor distribution of the L-shaped plate is shown in Figure 3 (b). The failure coefficients on the left and right sides of the left vertical part are large, and the L-shaped cutout has stress concentration. The path distribution after optimization is shown in Figure 3 (c). The paths on the upper and lower sides of different plies in the figure are the plies corresponding to the upper and lower neutral symmetry plane. It can be seen from the results in the figure that the paths of the corresponding plies are not the same. Therefore, the optimal design result belongs to the asymmetric variable stiffness ply design result. Among them, the left end fiber direction of plies 2, 3, 9, and 11 is mainly vertical, mainly used to bear the tension of this part in the vertical direction; the fiber direction of ply 12 is mainly horizontal, mainly used to bear the internal stress in the horizontal direction of the structure; the fiber direction of plies 3, 6, 7, and 9 is deflected along the 45° direction at the L-shaped cutout, mainly used to disperse the stress concentration of this part. The strength failure factor distribution corresponding to the final result is shown in Figure 3 (d). The failure coefficient of the left vertical part is significantly reduced, and the stress concentration at the L-shaped notch is reduced from the original 0.83 to 0.51, a decrease of 38.6%. The example demonstrates the feasibility and effectiveness of the load-bearing manufacturing integrated design method for asymmetric variable stiffness carbon fiber laminates.

[0106] In summary, the present invention is proposed to eliminate multiple numerical method problems in the strength optimization calculation of asymmetric variable stiffness laminate structures. The structural modeling problem of asymmetric variable stiffness laminate structures under the conditions of tension-bending, tension-shear, and bending-shear coupling deformation is solved; as well as the problem of inaccurate stress approximate calculation caused by the above-mentioned coupling deformation characteristics, which makes it impossible to use the stress-based strength failure criterion in iterative optimization calculations. In response to the above two problems, the present invention proposes to define the fiber layup angle at the local design point, and calculate the material stiffness by independently interpolating each unit in the calculation model, so as to accurately capture the changes in mechanical properties caused by changes in the layup direction; at the same time, the present invention rewrites the stress-based failure criterion into a strain-based failure criterion, thereby avoiding the problem of inaccurate stress approximate calculation in the iterative optimization calculation process, and ensuring stable convergence of the calculation results.

[0107] In addition, the present invention takes into account the manufacturability issues of variable stiffness laminate laying in the optimization calculation model, and reduces defects such as fiber wrinkles, fiber gaps and overlaps in the manufacturing process by introducing curvature constraints on the fiber path and parallel constraints between the tows. A limited constraint index calculation method is constructed for the above constraints, namely the gradient corresponding to the fiber angle and the divergence corresponding to the laying path. The optimal laying roadbed results show that the optimal laying path within each layer significantly eliminates excessive deflection and ensures parallelism between the laying paths. The proposed method thus realizes an integrated design method for load-bearing and manufacturing of asymmetric variable stiffness carbon fiber laminates.

[0108] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A load-bearing manufacturing integrated design method for an asymmetric variable stiffness carbon fiber laminate, characterized in that: The following steps are involved: Step S1. Based on the composite laminate theory and combined with the interpolation method, three types of matrices are established to characterize the material performance of asymmetric variable stiffness laminates, and the deformation coupling effects of stretching-bending, stretching-shearing, and bending-shearing are considered in the material modeling process; Step S2. Performing structural mechanics analysis on the variable stiffness laminate structure based on a mechanical method, and considering the above-mentioned deformation coupling effect in the structural model; Step S3. Constructing a material failure criterion suitable for iterative optimization of an asymmetric carbon fiber laminate structure, constructing a strain-based strength failure envelope based on conventional failure criteria, verifying the structural strength of the carbon fiber laminate by calculating the corresponding strength failure factor, and calculating the global strength failure factor that characterizes the laminate structure by a polymerization method; Step S4. construct a strength optimization model for calculating the fiber distribution in each ply of the asymmetric variable stiffness laminate structure, and add constraints related to key manufacturing indicators to ensure the manufacturability of the optimal variable stiffness fiber angle distribution; Step S5. Conduct sensitivity analysis of the strength failure coefficient, establish approximate calculations for the strength optimization objective function and manufacturing constraints, use a gradient-based optimization method to optimize the fiber angle distribution in each layer, and obtain the optimal fiber angle distribution under the manufacturing constraints; Step S6. Construct the fiber placement path in each ply by using the flow potential function or spline construction method and combining the optimal fiber angle distribution in each ply.

2. The load-bearing manufacturing integrated design method of an asymmetric variable stiffness carbon fiber laminate according to claim 1, characterized in that: In the step S1, the material properties of the asymmetric laminate are modeled using the composite laminate theory to obtain a material constitutive model of the asymmetric laminate; Based on the material constitutive model, the A matrix characterizing the in-plane performance of the material, the B matrix characterizing the in-plane and out-of-plane coupling effects of the material, and the D matrix characterizing the out-of-plane bending performance of the material are obtained.

3. The load-bearing manufacturing integrated design method of an asymmetric variable stiffness carbon fiber laminate according to claim 2, characterized in that: In step S2, the asymmetric carbon fiber laminate structure is discretized using the finite element method, specifically: The fiber angle representing the fiber laying direction is independently defined in each unit, and the corresponding A, B, and D matrices are calculated respectively; or the fiber angle representing the fiber laying direction is defined at the node of each unit, and the A, B, and D matrices are calculated, and the stiffness matrix in the unit is calculated by interpolation.

4. The load-bearing manufacturing integrated design method of an asymmetric variable stiffness carbon fiber laminate according to claim 1, characterized in that: In step S3, the strength of the composite structure is checked using the Tsai-Wu failure criterion of the composite material, specifically: The Tsai-Wu criterion is rewritten as a strain-based strength criterion. By taking the partial derivative of the fiber angle and taking the extreme value, a conservative failure envelope and the corresponding strength failure factor that meet any ply direction are constructed. When calculating the strength failure factor, the strain of the outer surface is taken to fully consider the out-of-plane bending effect, and the local strength failure factors are aggregated through the aggregation method to obtain the global strength failure factor.

5. The load-bearing manufacturing integrated design method of an asymmetric variable stiffness carbon fiber laminate according to claim 1 or 4, characterized in that: In step S4, the constraint condition is a variable stiffness composite structure manufacturing constraint, specifically: Constrain the curvature of the placement path by calculating the gradient of the fiber direction angle in each unit to ensure that the curvature of the fiber path meets the requirements; The parallelism of the placement path is estimated and constrained, and the overlap or gap of the fibers is controlled within the allowable range by calculating the divergence corresponding to the fiber path direction in each unit.

6. The load-bearing manufacturing integrated design method of an asymmetric variable stiffness carbon fiber laminate according to claim 5, characterized in that: In step S5, an approximate model for the global strength failure factor of the asymmetric variable stiffness composite material is constructed based on approximate calculation, specifically: The sensitivity of the global strength failure factor to the fiber direction at the design point in each ply is calculated, and the sensitivity of the global failure strength factor to any fiber direction is obtained by chain derivation, and then an approximate polynomial is constructed using the series method.

7. The load-bearing manufacturing integrated design method of an asymmetric variable stiffness carbon fiber laminate according to claim 1, characterized in that: In step S6, according to the result of the optimal fiber angle, a reference path for laying fibers is constructed using a flow potential function, specifically: The key parameter variables caused by the change of fiber orientation are calculated by numerical methods; By calculating the flow potential function corresponding to the fiber ply at each local position; The calculated flow potential function values ​​of the same coordinates are connected to obtain the reference line of the variable stiffness laying path.

8. The load-bearing manufacturing integrated design system of asymmetric variable stiffness carbon fiber laminates is characterized by: include: Material modeling module, which is used to establish three types of matrices to characterize the material properties of asymmetric variable stiffness laminates based on composite laminate theory and combined with interpolation methods; Structural mechanics analysis module, used to perform structural mechanics analysis of variable stiffness laminate structures based on mechanical methods; Strength failure criterion building module, used to build material failure criteria suitable for iterative optimization of asymmetric carbon fiber laminate structures; A strength optimization model building module is used to build a strength optimization model for calculating the fiber distribution in each ply of an asymmetric variable stiffness laminate structure; The optimization calculation module is used to carry out sensitivity analysis of the strength failure coefficient, establish approximate calculations of the strength optimization objective function and manufacturing constraints, and use a gradient-based optimization method to optimize the fiber angle distribution within each layer; The fiber placement path construction module is used to construct the fiber placement path in each ply by combining the optimal fiber angle distribution in each ply through the flow potential function or spline construction method.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the load-bearing manufacturing integrated design method for an asymmetric variable-rigidity carbon fiber laminate as claimed in any one of claims 1 to 7 is implemented.

10. An integrated design device for load-bearing manufacturing of asymmetric variable stiffness carbon fiber laminates, characterized in that: include: Memory for storing computer programs; A processor, configured to execute the computer program to implement the load-bearing manufacturing integrated design method for an asymmetric variable stiffness carbon fiber laminate as claimed in any one of claims 1 to 7; An input module, used for receiving initial layup parameters of composite materials, material mechanical property parameters and design constraints; An output module is used to output the optimized fiber layer angle distribution and the corresponding fiber placement path; The device executes a computer program in a memory through a processor, combines the parameters and constraints received by an input module, performs calculations and optimizations according to the steps of the method, and provides optimization results through an output module, thereby realizing a load-bearing manufacturing integrated design method for asymmetric variable stiffness carbon fiber laminates.

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