Integrated Design Method for Load-Bearing Manufacturing of Asymmetric Variable-Stiffness Carbon Fiber Laminates

Abstract

The present invention discloses a bearing and manufacturing integrated design method for an asymmetric variable-stiffness carbon fiber laminate. In view of the tensile-bending, tensile-shear, and bending-shear coupling deformation characteristics caused by the asymmetric layup in the present invention, during the material modeling process, the in-plane and out-of-plane coupling stiffness matrix is introduced to consider the influence of the above coupling effects. In addition, to effectively describe the influence of the change in the fiber direction within each ply of the variable-stiffness composite material, the local fiber angle of each ply is defined at the design points of the analysis model. In the analysis model, by calculating the material stiffness characteristics in the local area through various feasible interpolation methods for the material stiffness at the design points, the mechanical characteristics of the asymmetric variable-stiffness laminate can be effectively characterized.

Description

Technical Field

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

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

[0003] Asymmetrically laminated composite structures have relatively complex tensile-bending, tensile-shear, and bending-shear coupling deformation characteristics. To avoid abnormal responses caused by such coupling deformations, aerospace structures often adopt composite structures with symmetric layup forms. Existing research results and design methods are only applicable to composite structures that are symmetric with respect to the neutral plane. However, the coupling deformation effect of asymmetric layups can be used for stress redistribution design under extreme load conditions (such as stress concentration), thereby indirectly enhancing the ultimate load-bearing capacity of composite structures. Currently, there is a lack of strength optimization design methods for asymmetrically laminated carbon fiber structures, and the strength optimization design of composite structures in this form is a new challenge for enhancing the ultimate load-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 been gradually deepened, and a variable angle placement path design method suitable for improving strength has been proposed. Existing methods can be used to design fiber variable angle placement paths that are symmetric with respect to the neutral plane. However, the research on the design of variable-stiffness carbon fiber layups for asymmetric layups is still blank. Mechanical simulation results show that along with the coupling deformations of tensile-bending, tensile-shear, and bending-shear, asymmetric composite structures can improve the structural load-bearing capacity under extreme load conditions of aerospace structures.

[0005] Although existing gradient-based and data-driven variable-stiffness composite design methods have laid a relevant theoretical foundation for symmetric variable-stiffness composite design. For the design of asymmetric variable-stiffness composite structures, there are still the following three numerical method problems: 1) There is a lack of structural modeling methods that can effectively characterize the mechanical properties of asymmetric variable-stiffness composites; 2) There is a lack of strength criterion models that consider the coupling deformation effect of asymmetric carbon fiber composite structures in iterative optimization calculations; 3) It is necessary to construct an integrated design method framework for load-bearing manufacturing suitable for asymmetric variable-stiffness composite structures. The above problems limit the full exploration of the potential design capabilities of strength optimization of asymmetric variable-stiffness composite structures. Summary of the Invention

[0006] In view of the defects of the existing technology and the improvement requirements, the present invention provides an integrated design method for load-bearing manufacturing of an asymmetric variable-stiffness carbon fiber laminate, aiming to construct a complete set of design method frameworks suitable for strength optimization of asymmetric variable-stiffness composite materials and apply them to actual aircraft structure design, so as to improve the ultimate load-bearing capacity of aircraft structures by integrating the coupling deformation effect.

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

[0008] S1. Based on the composite laminate theory and combined with the interpolation method, establish three types of matrices characterizing the material properties of the asymmetric variable-stiffness laminate, and consider the deformation coupling effects of tension-bending, tension-shear, and bending-shear during the material modeling process;

[0009] S2. Conduct structural mechanics analysis on the variable-stiffness laminate structure based on mechanical methods (such as the finite element plate and shell theory), and consider the above deformation coupling effects in the structural model;

[0010] S3. Construct a material failure criterion suitable for iterative optimization of the asymmetric carbon fiber laminate structure, construct a strain-based strength failure envelope based on conventional failure criteria (such as the Tsai-Wu criterion), check the structural strength of the carbon fiber laminate by calculating the corresponding strength failure factor, and calculate the global strength failure factor characterizing the laminate structure through aggregation methods (such as the p-norm function) to simplify the strength check;

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

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

[0013] S6. Construct the fiber placement path in each ply through the flow potential function or spline construction method, combined with the optimal fiber angle distribution in each ply.

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

[0015] A material modeling module for establishing three types of matrices characterizing the material properties of the asymmetric variable-stiffness laminate based on the composite laminate theory and combined with the interpolation method;

[0016] A structural mechanics analysis module for performing structural mechanics analysis on a variable stiffness laminated plate structure based on mechanical methods;

[0017] A strength failure criterion construction module for constructing a material failure criterion applicable to iterative optimization of an asymmetric carbon fiber laminate structure;

[0018] A strength optimization model construction module for constructing a strength optimization model for calculating the fiber distribution within each ply of an asymmetric variable stiffness laminated plate structure;

[0019] An optimization calculation module for performing sensitivity analysis of the strength failure coefficient, establishing an approximate calculation of the strength optimization objective function and manufacturing constraints, and using a gradient-based optimization method to optimize the fiber ply angle distribution within each ply;

[0020] A fiber placement path construction module for constructing the fiber placement path within each ply by means of a flow potential function or a spline construction method, in combination with the optimal fiber angle distribution within each ply.

[0021] The third aspect of the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the integrated design method for load-bearing manufacturing of an asymmetric variable stiffness carbon fiber laminate is implemented.

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

[0023] A memory for storing a computer program;

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

[0025] An input module for receiving the initial ply parameters, material mechanical property parameters, and design constraint conditions of the composite material;

[0026] An output module for outputting the optimized fiber ply angle distribution and the corresponding fiber placement path;

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

[0028] Through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0029] (1) The present invention provides a modeling and analysis method applicable to the asymmetric variable stiffness laminated plate structure. Aiming at the tensile-bending, tensile-shear, and bending-shear coupling deformation characteristics caused by asymmetric layup, an in-plane and out-of-plane coupling stiffness matrix is introduced during the material modeling process to consider the influence of the above coupling effects. In addition, to effectively describe the influence of the change in the fiber direction within each ply of the variable stiffness composite material, local fiber angles of each ply are defined at the design points of the analysis model. In the analysis model, by calculating the material stiffness characteristics in the local area through various feasible interpolation methods based on the material stiffness at the design points, the mechanical properties of the asymmetric variable stiffness laminated plate can be effectively characterized.

[0030] (2) The present invention also provides a strength checking method applicable to the performance iterative optimization of the asymmetric variable stiffness laminated plate structure. Aiming at the tensile-bending, tensile-shear, and bending-shear coupling deformation characteristics caused by asymmetric layup, a Tsai-Wu failure criterion method based on strain is designed. By checking the strength of the composite material structure through the strain field, the distortion of the stress field approximation during the iterative process can be effectively avoided. On this basis, a conservative failure envelope that satisfies any fiber angle is constructed, thus simplifying the complex process of separately checking and calculating each ply required by the Tsai-Wu failure criterion, and further simplifying the strength calculation through the aggregation of failure factors.

[0031] (3) The present invention also provides a framework for an integrated load-bearing manufacturing method applicable to the asymmetric variable stiffness laminated plate structure. During the optimization modeling process, the approximate model constructed for the global strength failure factor considers the coupling deformation effect of the asymmetric composite structure, with the goal of minimizing the global strength failure factor. In addition, to control defects such as fiber wrinkling, fiber gaps, and overlaps caused by variable angle fiber placement, constraint strategies for controlling the fiber curvature and parallelism within each ply are added to the optimization model; while improving the structural strength, the defects that may be introduced by variable angle design are reduced; for manufacturing constraints, feasible implementation methods are pointed out to ensure the manufacturability of the optimal design. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flowchart of an integrated load-bearing manufacturing design method for an asymmetric variable stiffness carbon fiber laminated plate provided by an embodiment of the present invention;

[0033] Figure 2 is a schematic diagram of local material property modeling calculation for the mechanical analysis of an asymmetric variable stiffness laminated plate provided by an embodiment of the present invention;

[0034] FIG. 3(a) is a composite material structure to be optimized;

[0035] FIG. 3(b) is the distribution of the strength failure factor of the L-shaped plate;

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

[0037] Figure 3(d) shows the distribution of the strength failure factor corresponding to the final result. Specific implementation manners

[0038] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to 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 used 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 integrated design method for load-bearing manufacturing of an asymmetric variable-stiffness carbon fiber laminate provided by this application has a process as Figure 1 shown, and includes the following steps:

[0040] Step S1: Based on the composite laminate theory and combined with the interpolation method, establish the A, B, and D matrices characterizing the material properties of the asymmetric variable-stiffness laminate, and consider the deformation coupling effects of tension-bending, tension-shear, and bending-shear during the material modeling process.

[0041] Furthermore, the implementation manner of step S1 includes:

[0042] S1.1: Use the composite laminate theory to model the material properties of the asymmetric variable-stiffness laminate to obtain the material constitutive model of the asymmetric variable-stiffness laminate:

[0043]

[0044] In the formula, represents the in-plane force along the direction, represents the in-plane force along the direction, represents the in-plane shear force along the axis perpendicular to the direction; represents the out-of-plane bending moment about the axis, represents the out-of-plane bending moment about the axis, represents the torque formed by the shear stress; represents the in-plane strain of the neutral plane along the direction, represents the in-plane strain of the neutral plane along the direction, represents the in-plane shear strain in the neutral plane; represents the rotation of the neutral plane about the The external curvature of the shaft represents the neutral plane rotating around the external curvature of the shaft represents the torsional curvature of the neutral plane; ( ) respectively represent the in-plane internal force and the in-plane modulus of plane strain of the material; represents the internal force of the material and the coupling modulus of the out-of-plane curvature of the material; represents the out-of-plane bending moment of the material and the bending modulus of the out-of-plane curvature of the material.

[0045] From we can obtain the A matrix characterizing the in-plane properties of the material, and through we can obtain the B matrix characterizing the coupling effect between the in-plane and out-of-plane of the material. From we can obtain the D matrix characterizing the out-of-plane bending properties of the material. Among them, the B matrix is the key to characterizing the tensile-bending deformation coupling effect of asymmetrically laminated composites and cannot be ignored in the modeling process.

[0046] Furthermore, the implementation method of the step S2 includes:

[0047] S2.1. Discretize the asymmetric variable stiffness laminated plate structure by using the finite element method. To characterize the material mechanical properties of the variable stiffness carbon fiber laminated plate in each element, it can be achieved in two ways, as Figure 2 shown:

[0048] First, independently define the fiber angle representing the fiber laying direction in each element, and calculate the in-plane, in-plane-out-of-plane coupling, and out-of-plane stiffness matrices in any element , , ;

[0049] Second, define the fiber angle representing the fiber laying direction at the nodes of each element, and calculate the A, B, and D matrices at the nodes. The stiffness matrices , , in the element are calculated by interpolation, such as:

[0050] or

[0051] In the formula, represents the A matrix of the th node, Denote the total number of nodes in the element, and the corresponding interpolation method is also applicable to calculation.

[0052] For matrix calculation, linear interpolation is used:

[0053]

[0054] S2.2. To perform mechanical analysis on the asymmetric variable stiffness laminated plate structure, based on the , , matrix obtained in S2.1, combined with the plate and shell theory to construct the stiffness matrix of each element, and assemble the global stiffness matrix K according to the degrees of freedom of each node. The structural displacement field can be obtained by solving the equilibrium equation: ; By solving the displacement field of the structure, the strain of the structure is further calculated. In the formula, is the external force vector on the model, and the structural analysis of the asymmetric variable stiffness laminated plate is realized based on the above model.

[0055] Furthermore, the implementation method of step S3 includes:

[0056] S3.1. Use the Tsai-Wu failure criterion of composite materials to check the strength of the composite structure. Due to the coupled mechanical properties of tensile-bending, tensile-shear, and bending-shear of asymmetric laminates, 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, and it needs to be transformed into the strain in the structural reference coordinate system during the calculation (the same as the strain in the material constitutive equation

[0059] S3.2. To ensure that the above failure criterion is applicable to each ply in the thickness direction, construct a conservative failure envelope. The derivation method can be to calculate the partial derivative of the strain-based Tsai-Wu failure criterion with respect to the fiber angle , and make it take the extreme value:

[0060] ;

[0061] The conservative failure envelope satisfying any ply direction and the corresponding strength failure factor can be derived from the above formula. ( indicating that the material does not fail); Based on the conservative failure envelope, only one strength failure factor can be used to perform strength verification on each ply in the local thickness direction.

[0062] S3.3. Due to the coupled deformation of the asymmetric ply structure, when calculating the strength failure factor in the above formula, the strain on the outer surface should be taken 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 verification calculation, the local strength failure factors are aggregated using an aggregation method (such as the p-norm function) to obtain the global strength failure factor .

[0066] Furthermore, the implementation manner of step S4 includes:

[0067] S4.1. Construct variable stiffness composite manufacturing constraints: For variable angle plies of composite structures, if the curvature of the laying path is too large, fiber wrinkling defects are likely to occur; To avoid fiber wrinkling defects in the laying structure, it is necessary to constrain the curvature of the laying path;

[0068] Among them, the curvature of the laying path can be calculated by characterizing 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 element:

[0069]

[0070] In the formula, represents the path direction gradient calculated from the fiber distribution in each element, and represent spatial coordinates. When is less than the allowable gradient upper limit, the fiber path meets the curvature requirements;

[0071] S4.2. To avoid fiber overlap or gaps between laying paths, it is necessary to estimate and constrain the parallelism of the laying paths; The parallelism can be characterized by the divergence of the fiber direction, and the calculation method can also be through the fiber path direction Calculate the corresponding divergence:

[0072]

[0073] In the formula, and represent spatial coordinates. When , it represents fiber overlap; when , it represents a gap between fibers. If it is desired that the fiber overlap or gap is within the allowable range, then control the upper and lower bounds of to be within the given range.

[0074] Furthermore, the implementation method of step S5 includes:

[0075] S5.1. Construct an approximate model of the global strength failure factor of the asymmetric variable stiffness carbon fiber laminate, for example, an approximate polynomial can be constructed using the series method. The construction of the approximate model first requires calculating the global strength failure factor for the fiber direction at the design points in each ply.

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

[0077] ,

[0078] Based on this, the sensitivity of for any can be obtained through chain differentiation:

[0079] ,

[0080] Furthermore, an approximate model can be constructed through the series method;

[0081] S5.2. With the minimization of the global strength failure factor as the objective and the fiber angle feasible region and the parameter indexes for reducing the manufacturing defects of variable angle placement as the constraint conditions, construct the following optimization model:

[0082]

[0083] Among them, is the total number of design nodes, is the total number of elements, is the design layer number, and are the upper and lower bounds of the fiber angle respectively, represents each unit inside the layer fiber curvature, which is used to avoid fiber wrinkling, represents the unit inside the layer fiber parallelism, which is used to control the gap and overlap between fibers, represents the maximum allowable fiber curvature, represents the upper limit of fiber divergence. In the above formula, by changing the fiber angle of the design points in each ply the global strength failure factor is reduced ; by considering the fiber curvature within each local range , and fiber divergence ; it is ensured that the optimal design can improve the structural strength while reducing fiber wrinkling, gap and overlap defects in the laying path.

[0084] Furthermore, the implementation method of the step S6 includes:

[0085] S6.1. According to the result of the optimal fiber angle, use the flow potential function to construct the reference path of fiber placement:

[0086] Calculate the key parameter variables caused by the change of fiber direction through numerical methods. For example, the influence of the angle on physical quantities can be characterized by the change of fiber thickness caused by the deflection of fiber direction;

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

[0088] ;

[0089] Finally, the calculated (wherein, represents the potential function value calculated according to and in the local area) the design point coordinates corresponding to the same are connected, and the reference line of the variable stiffness laying path is obtained. Since the fiber angles in all plies are used as design variables, therefore, the optimal design will form an asymmetric variable stiffness laminate structure; thus, the integrated design method for load-bearing manufacturing of asymmetric variable stiffness carbon fiber laminates is completed.

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

[0091] A material modeling module for establishing A, B, and D matrices characterizing the material properties of an asymmetric variable stiffness laminated plate based on the composite laminate theory and combined with an interpolation method;

[0092] A structural mechanics analysis module for performing structural mechanics analysis on the variable stiffness laminated plate structure based on mechanical methods;

[0093] A strength failure criterion construction module for constructing a material failure criterion applicable to the iterative optimization of an asymmetric carbon fiber laminate structure;

[0094] A strength optimization model construction module for constructing a strength optimization model for calculating the fiber distribution within each ply of an asymmetric variable stiffness laminated plate structure;

[0095] An optimization calculation module for conducting sensitivity analysis of the strength failure coefficient, establishing an approximate calculation of the strength optimization objective function and manufacturing constraints, and using a gradient-based optimization method to optimize the fiber ply angle distribution within each ply;

[0096] A fiber placement path construction module for constructing the fiber placement path within each ply by means of a flow potential function or a spline construction method in combination with the optimal fiber angle distribution within each ply.

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

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

[0099] A memory for storing a computer program;

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

[0101] An input module for receiving the initial ply parameters, material mechanical property parameters, and design constraint conditions of the composite material;

[0102] An output module for outputting the optimized fiber ply angle distribution and the corresponding fiber placement path;

[0103] The device executes the computer program in the memory by the processor, combines the parameters and constraint conditions received by the input module, performs calculations and optimizations according to the steps of the method, and provides the optimization result through the output module, thereby implementing the integrated load-bearing manufacturing design method of the asymmetric variable stiffness carbon fiber laminate.

[0104] Embodiment: The domain of the composite material structure to be optimized is an L-shaped plate structure. The top end of the plate is fixed, and a downward shear load is applied at the lower right corner. The structure is set to contain 12 design plies, and the initial ply orientations at each design point are: [0, 36, 72, 108, 144, 180]s, as shown in Fig. 3(a).

[0105] According to the method of the present application, before optimization, under the given working conditions, the strength failure factor distribution of the L-shaped plate is shown in Fig. 3(b). The failure coefficients on the left and right sides of the left vertical part are relatively large, and there is stress concentration at the shear notch of the L-shape. The optimized path distribution is shown in Fig. 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 sides with respect to the 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 fiber directions at the left ends of plies 2, 3, 9, and 11 are mainly vertical, mainly used to bear the tensile force in the vertical direction of this part; 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 directions of plies 3, 6, 7, and 9 deflect along the 45° direction at the shear notch of the L-shape, mainly used to disperse the stress concentration in this part. The strength failure factor distribution corresponding to the final result is shown in Fig. 3(d). The failure coefficient of the left vertical part is significantly reduced, and the stress concentration at the shear notch of the L-shape is reduced from the original 0.83 to 0.51, a reduction of 38.6%. The embodiment proves the feasibility and effectiveness of the integrated design method for load-bearing manufacturing of 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. It solves the problems of structural modeling of asymmetric variable stiffness laminate structures under the conditions of tensile-bending, tensile-shear, and bending-shear coupling deformations; and the problem that the stress approximation calculation is inaccurate due to the above-mentioned coupling deformation characteristics, so that the stress-based strength failure criterion cannot be used in the iterative optimization calculation. To address the above two problems, the present invention proposes to define the fiber ply angle at local design points and calculate the material stiffness by independently interpolating each element in the calculation model, so as to accurately capture the change in mechanical properties caused by the change in ply orientation; at the same time, the present invention avoids the problem of inaccurate stress approximation calculation during the iterative optimization calculation by rewriting the stress-based failure criterion as a strain-based failure criterion, ensuring the stable convergence of the calculation results.

[0107] In addition, in the optimized calculation model of the present invention, the manufacturability problem of variable-stiffness laminated plates is considered. By introducing the curvature constraint of the fiber path and the parallel constraint between tows, defects such as fiber wrinkles, fiber gaps, and overlaps existing in the manufacturing process are reduced. A calculation method for defining constraint indexes 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 path results show that the optimal laying paths in each ply significantly eliminate excessive deflection and ensure the parallelism between the laying paths. Thus, the proposed method realizes the integrated design method of load-bearing manufacturing for asymmetric variable-stiffness carbon fiber laminated plates.

[0108] Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, 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. An integrated design method for load-bearing manufacturing of an asymmetric variable stiffness carbon fiber laminate, characterized in that, It includes the following steps: Step S1. Based on the composite laminate theory and combined with the interpolation method, three types of matrices characterizing the material properties of the asymmetric variable stiffness laminate are established, and the deformation coupling effects of tension-bending, tension-shear, and bending-shear are considered in the material modeling process; Step S2. Based on the mechanical method, structural mechanics analysis is carried out on the variable stiffness laminate structure, and the above deformation coupling effects are considered in the structural model; Step S3. Construct a material failure criterion applicable to the iterative optimization of the asymmetric carbon fiber laminate structure. Based on the conventional failure criterion, a strain-based strength failure envelope is constructed. The structural strength of the carbon fiber laminate is checked by calculating the corresponding strength failure factor, and the global strength failure factor characterizing the laminate structure is calculated by the aggregation 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 constraint conditions related to key manufacturing indicators to ensure the manufacturability of the optimal variable stiffness fiber angle distribution; Step S5. Conduct a sensitivity analysis of the strength failure coefficient, establish an approximate calculation of the strength optimization objective function and manufacturing constraints, and use the gradient-based optimization method to optimize the fiber laying angle distribution in each ply to obtain the optimal fiber angle distribution under the manufacturing constraint conditions; Step S6. Through the construction method of the flow potential function or spline curve, combined with the optimal fiber angle distribution in each ply, construct the fiber laying path in each ply; In the said Step S1, the composite laminate theory is used to model the material properties of the asymmetric laminate, and the material constitutive model of the asymmetric laminate is obtained; Based on the material constitutive model, the A matrix characterizing the in-plane properties 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 properties of the material are obtained.

2. The integrated design method for load-bearing manufacturing of the asymmetric variable stiffness carbon fiber laminate according to claim 1, wherein In the said Step S2, the finite element method is used to discretize the asymmetric ply carbon fiber laminate structure. Specifically: Independently define the fiber angle characterizing the fiber laying direction in each element, and calculate the corresponding A, B, D matrices respectively; or define the fiber angle characterizing the fiber laying direction at the nodes of each element, and calculate the A, B, D matrices, and the stiffness matrix within the element is calculated by interpolation.

3. The integrated design method for load-bearing manufacturing of the asymmetric variable-stiffness carbon fiber laminate according to claim 1, wherein In the said Step S3, the Tsai-Wu failure criterion of the composite material is used to check the strength of the composite structure. Specifically: Rewrite the Tsai-Wu criterion as a strain-based strength criterion, and by taking the partial derivative of the fiber angle and taking the extreme value, construct a conservative failure envelope and the corresponding strength failure factor that satisfy any laying direction; When calculating the strength failure factor, take the strain on the outer surface to fully consider the out-of-plane bending effect, and aggregate the local strength failure factors by the aggregation method to obtain the global strength failure factor.

4. The integrated design method for load-bearing manufacturing of the asymmetric variable-stiffness carbon fiber laminate according to claim 1 or 3, characterized in that In the said Step S4, the constraint condition is the manufacturing constraint of the variable stiffness composite structure. Specifically: Constrain the curvature of the laying path, and by calculating the gradient of the fiber direction angle in each element, ensure that the curvature of the fiber path meets the requirements; Estimate and constrain the parallelism of the laying path, and by calculating the divergence corresponding to the fiber path direction in each element, control the overlap or gap of the fibers within the allowable range.

5. The integrated design method for manufacturing and load-bearing of the asymmetric variable stiffness carbon fiber laminate according to claim 4, characterized in that, In step S5, an approximation model for the global strength failure factor of the asymmetric variable stiffness composite material is constructed based on approximate calculation, specifically as follows: Calculate the sensitivity of the global strength failure factor to the fiber direction at the design points within each ply. Through chain differentiation, obtain the sensitivity of the global strength failure factor to any fiber direction, and then use the series method to construct an approximate polynomial.

6. The integrated design method for load-bearing manufacturing of the asymmetric variable-stiffness carbon fiber laminate according to claim 1, wherein, In step S6, according to the result of the optimal fiber angle, use the flow potential function to construct the fiber placement reference path, specifically as follows: Calculate the key parameter variables caused by the change in fiber direction through numerical methods; Calculate the flow potential function corresponding to the fiber plies at each local position; Connect the calculated flow potential function values at the same coordinates to obtain the reference line of the variable stiffness placement path.

7. An integrated design system for load-bearing manufacturing of an asymmetric variable stiffness carbon fiber laminate, used to implement the method described in claim 1, characterized in that Including: A material modeling module for establishing three types of matrices characterizing the material properties of the asymmetric variable stiffness laminate based on the composite laminate theory and combined with the interpolation method; A structural mechanics analysis module for performing structural mechanics analysis on the variable stiffness laminate structure based on mechanical methods; A strength failure criterion construction module for constructing a material failure criterion applicable to the iterative optimization of the asymmetric carbon fiber laminate structure; A strength optimization model construction module for constructing a strength optimization model for calculating the fiber distribution within each ply of the asymmetric variable stiffness laminate structure; An optimization calculation module for conducting sensitivity analysis of the strength failure coefficient, establishing an approximate calculation of the strength optimization objective function and manufacturing constraints, and using the gradient-based optimization method to optimize the fiber placement angle distribution within each ply; A fiber placement path construction module for constructing the fiber placement path within each ply through the flow potential function or spline construction method, combined with the optimal fiber angle distribution within each ply.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the integrated load-bearing manufacturing design method of the asymmetric variable stiffness carbon fiber laminate as described in any one of claims 1 to 6.

9. The integrated design equipment for load-bearing manufacturing of an asymmetric variable stiffness carbon fiber laminate, characterized in that, Including: A memory for storing the computer program; A processor for executing the computer program to implement the integrated load-bearing manufacturing design method of the asymmetric variable stiffness carbon fiber laminate as described in any one of claims 1 to 6; An input module for receiving the initial ply parameters, material mechanical property parameters, and design constraint conditions of the composite material; An output module for outputting the optimized fiber ply angle distribution and the corresponding fiber placement path; The integrated load-bearing manufacturing design device executes the computer program in the memory through the processor, combines the parameters and constraint conditions received by the input module, performs calculations and optimizations according to the steps of the method, and provides the optimization results through the output module to achieve the integrated load-bearing manufacturing design of the asymmetric variable stiffness carbon fiber laminate.

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