A ply drop optimization design method for composite materials based on ply database

Abstract

The present application provides a composite material ply drop optimization design method based on a ply database. The composite material ply drop optimization design method based on a ply database of the present application uses a dual isogenic genetic algorithm to generate a composite material ply database that meets engineering requirements, and then uses a finite element method to obtain the ply thickness and ply ratio of each ply area, divides different types of plies through a connection matrix, and determines the ply data of each type of ply. The ply sequence of each type of ply is obtained by matching the ply data in the composite material ply database, and the finite element method is used to verify the ply sequence to obtain the optimal ply design scheme. The present application can quickly realize the composite material ply drop optimization design, give full play to the advantages of the engineering ply database, avoid the low efficiency of the optimization algorithm in the ply drop processing, and provide an efficient means for the ply optimization design of large composite material structures.

Description

Technical Field

[0001] The present application belongs to the field of composite material ply design, and in particular relates to a composite material ply drop optimization design method based on a ply database. Background Art

[0002] Composite materials are widely used in aircraft structural design due to their excellent specific strength, specific stiffness, fatigue and other performance advantages. With the improvement of structural bearing capacity and lightweight requirements, thin-walled structures made of composite materials are becoming more and more complex. In the thin-walled composite structures of aerospace, multiple partitions can often be divided, and each partition is optimized with different thicknesses according to the load form it bears. Since the fibers in the composite ply are the main body of force transmission, designing each thickness partition separately will cause part of the ply to be cut off at the partition connection, which is called ply loss, resulting in discontinuous ply force transmission, stress concentration at the boundary, damage to the composite matrix, and affecting the bearing capacity of the structure.

[0003] In the current ply dropping optimization design methods, intelligent optimization algorithms or designed ply dropping sequences are often used to optimize the ply sequence of variable thickness composite structures. The existing design methods have low computational efficiency and are difficult to converge after the introduction of engineering constraints.

[0004] Therefore, it is desired to have a technical solution to overcome or at least alleviate at least one of the above-mentioned defects of the prior art. Summary of the invention

[0005] The purpose of this application is to provide a composite material ply drop optimization design method based on a ply database to solve at least one problem existing in the prior art.

[0006] The technical solution of this application is:

[0007] A composite material ply loss optimization design method based on a ply database, comprising:

[0008] Step 1: Build a composite material layup database;

[0009] Step 2: obtaining multiple ply regions of the variable thickness composite material structure, and determining the ply thickness and ply ratio of each ply region;

[0010] Step 3: Generate a connection matrix according to the connection relationship between each ply area, and divide the plies in each ply area into three types: global shared plies, local shared plies and unique plies according to the connection matrix, and determine the ply thickness and ply ratio of the global shared plies, the ply thickness and ply ratio of the local shared plies, and the ply thickness and ply ratio of the unique plies in each ply area;

[0011] Step 4: matching a global shared ply sequence having the same ply thickness and ply ratio as the global shared ply in the composite material ply database;

[0012] Matching a local shared ply sequence having the same ply thickness and ply ratio as the local shared ply in the composite material ply database;

[0013] Matching a unique ply sequence having the same ply thickness and ply ratio as the unique ply in the composite material ply database;

[0014] Step 5: Select a set of global shared ply sequence, local shared ply sequence and unique ply sequence to generate an overall ply sequence;

[0015] Step 6: constructing a finite element model of a variable thickness composite material structure according to the overall ply sequence;

[0016] Step 7: Determine whether each ply area of ​​the variable thickness composite material structure finite element model meets the strength, stiffness and stability requirements at the same time;

[0017] If so, retain the overall ply sequence;

[0018] Calculate the mass of the finite element model of the variable thickness composite material structure corresponding to the retained overall ply sequence;

[0019] Return to step five, reselect a set of global shared layup sequences, local shared layup sequences and unique layup sequences to generate a new overall layup sequence, until all combinations of global shared layup sequences, local shared layup sequences and unique layup sequences are traversed, and the overall layup sequence corresponding to the variable thickness composite material structure finite element model with the smallest mass is screened out.

[0020] In at least one embodiment of the present application, in step 1, a dual isogenic genetic algorithm is used to construct a composite material ply database, wherein the constraints include: equilibrium constraint, symmetry constraint, outer surface ±45 degree constraint, continuous ply number constraint, and ply ratio constraint;

[0021] The fitness functions include: compression fitness function and shear fitness function;

[0022] The penalty functions include: continuous ply penalty function, outer surface ±45 degree penalty function, and adjacent ply angle penalty function.

[0023] In at least one embodiment of the present application, in step 2, obtaining multiple ply regions of a variable thickness composite material structure and determining the ply thickness and ply ratio of each ply region includes:

[0024] Acquire multiple ply regions of a composite structure with variable thickness;

[0025] The various ply regions of the variable thickness composite material structure are set to a balanced symmetrical laminate structure;

[0026] Determine the initial ply thickness and ply ratio for each ply area;

[0027] The plying order of each ply area of ​​the variable thickness composite material structure is set to 0° plying, +45° plying, -45° plying, and 90° plying from the outer surface to the middle surface;

[0028] Constructing a finite element model of a composite material structure with variable thickness, optimizing the finite element model of the composite material structure with variable thickness, and outputting the ply thickness and ply ratio of each ply area that simultaneously meets the requirements of strength, stiffness, and stability;

[0029] The ply thickness of each ply area is rounded off to obtain the number of plies at each angle.

[0030] In at least one embodiment of the present application, in step 3, the connection matrix is ​​an n×n matrix, where n is the number of ply regions;

[0031] In the connection matrix:

[0032] The first identifier indicates that there is a connection relationship between the two ply regions;

[0033] The second identifier indicates that there is no connection relationship between the two ply regions.

[0034] In at least one embodiment of the present application, in step three, the global shared plies in the ply area are plies shared by all ply areas;

[0035] The local shared plies in the ply area are plies shared by the ply area and other ply areas having a connection relationship;

[0036] A unique ply in a ply zone is a ply that is unique to that ply zone.

[0037] In at least one embodiment of the present application, in step six, constructing a variable thickness composite material structure finite element model according to the overall ply sequence includes:

[0038] Obtaining an initial finite element model;

[0039] A variable thickness composite material structure finite element model is constructed based on the initial finite element model according to the overall ply sequence.

[0040] In at least one embodiment of the present application, in step seven, it is determined whether each ply region of the variable thickness composite material structure finite element model satisfies the strength, stiffness, and stability requirements at the same time;

[0041] If yes, before preserving the overall ply order also include:

[0042] The number of unique plies in the ply area where the design margin meets the requirements is reduced to obtain an adjusted overall ply sequence, a finite element model of a variable thickness composite material structure is constructed according to the adjusted overall ply sequence, and it is determined whether each ply area of ​​the finite element model of the variable thickness composite material structure meets the strength, stiffness and stability requirements at the same time. If so, the adjusted overall ply sequence is retained; if not, the overall ply sequence before adjustment is retained.

[0043] In at least one embodiment of the present application, in step seven, it is determined whether each ply region of the variable thickness composite material structure finite element model satisfies the strength, stiffness, and stability requirements at the same time;

[0044] If not, increase the number of unique plies in the ply areas that cannot simultaneously meet the strength, stiffness and stability requirements to obtain an adjusted overall ply sequence, and construct a finite element model of a variable thickness composite material structure according to the adjusted overall ply sequence to determine whether each ply area of ​​the finite element model of the variable thickness composite material structure simultaneously meets the strength, stiffness and stability requirements; if so, retain the adjusted overall ply sequence; if not, delete the overall ply sequence before adjustment.

[0045] The invention has at least the following beneficial technical effects:

[0046] The composite material ply dropping optimization design method based on the ply database of the present application can quickly realize the composite material ply dropping optimization design, give full play to the advantages of the engineering ply database, avoid the low efficiency of the ply dropping processing optimization algorithm and other problems, and provide an efficient means for the ply optimization design of large composite material structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a flow chart of a composite material ply loss optimization design method based on a ply database according to one embodiment of the present application. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the embodiment of this application will be described in more detail below in conjunction with the drawings in the embodiment of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of this application, not all of them. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain this application, and should not be construed as limitations on this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The embodiments of this application are described in detail below in conjunction with the drawings.

[0049] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the scope of protection of the present application.

[0050] The following is combined with Figure 1 This application is described in further detail.

[0051] The present application provides a composite material layer loss optimization design method based on a layer database, comprising the following steps:

[0052] Step 1: Build a composite material layup database;

[0053] Step 2: obtaining multiple ply regions of the variable thickness composite material structure, and determining the ply thickness and ply ratio of each ply region;

[0054] Step 3: Generate a connection matrix according to the connection relationship between each ply area, and divide the plies in each ply area into three types: global shared plies, local shared plies, and unique plies according to the connection matrix, and determine the ply thickness and ply ratio of the global shared plies, the ply thickness and ply ratio of the local shared plies, and the ply thickness and ply ratio of the unique plies in each ply area;

[0055] Step 4: Match the global shared ply sequence with the same ply thickness and ply ratio as the global shared ply in the composite material ply database;

[0056] Matching the local shared ply sequence with the same ply thickness and ply ratio as the local shared ply in the composite material ply database;

[0057] Matching a unique ply sequence with the same ply thickness and ply ratio as the unique ply in the composite ply database;

[0058] Step 5: Select a set of global shared ply sequence, local shared ply sequence and unique ply sequence to generate an overall ply sequence;

[0059] Step 6: construct a finite element model of the variable thickness composite material structure according to the overall ply sequence;

[0060] Step 7: Determine whether each ply area of ​​the variable thickness composite material structure finite element model meets the strength, stiffness and stability requirements at the same time;

[0061] If so, retain the overall ply sequence;

[0062] Calculate the mass of the finite element model of the variable thickness composite structure corresponding to the retained overall ply sequence;

[0063] Return to step five, reselect a set of global shared layup sequences, local shared layup sequences and unique layup sequences to generate a new overall layup sequence, until all combinations of global shared layup sequences, local shared layup sequences and unique layup sequences are traversed, and the overall layup sequence corresponding to the variable thickness composite material structure finite element model with the smallest mass is screened out.

[0064] The composite material ply loss optimization design method based on the ply database of the present application, first, in step one, a dual isogenic genetic algorithm is used to construct a composite material ply database that meets engineering requirements based on appropriate constraints, fitness functions and penalty functions. Among them, the constraints of the ply sequence include: equilibrium constraints, symmetry constraints, external surface ±45 degree constraints, continuous ply number constraints, and ply ratio constraints; the fitness functions include: compression fitness function and shear fitness function; the penalty functions include: continuous ply penalty function, external surface ±45 degree penalty function, and adjacent ply angle penalty function. The penalty function is introduced on the basis of the fitness function to ensure the engineering applicability of the optimization result.

[0065] The composite material layer loss optimization design method based on the ply database of the present application, in step 2, divides each thickness zone of the variable thickness composite material structure into ply regions, and uses the finite element method to determine the ply thickness and ply ratio of each ply region. The specific process is as follows:

[0066] Acquire multiple ply regions of a composite structure with variable thickness;

[0067] The various ply regions of the variable thickness composite material structure are set to a balanced symmetrical laminate structure;

[0068] Determine the initial ply thickness and ply ratio for each ply area;

[0069] The plying order of each ply area of ​​the variable thickness composite material structure is set to 0° plying, +45° plying, -45° plying, and 90° plying from the outer surface to the middle surface;

[0070] Construct a finite element model of a composite material structure with variable thickness, optimize the finite element model of the composite material structure with variable thickness, and output the ply thickness and ply ratio of each ply area that simultaneously meets the requirements of strength, stiffness, and stability;

[0071] The ply thickness of each ply area is rounded off to obtain the number of plies at each angle.

[0072] The composite material ply loss optimization design method based on the ply database of the present application adopts the finite element method to continuously optimize the ply thickness and ply ratio of each ply area through strength, stiffness and stability indicators, and finally obtains the ply thickness and ply ratio of each ply area that meet the requirements of multiple indicators. In this embodiment, the numerical optimization function of the SABRE finite element software is preferably used to obtain the real value of the ply thickness and ply ratio of each ply area of ​​the variable thickness composite material structure that is lightweight and meets the mechanical requirements. At the same time, the software can also output the area, mass, in-plane stiffness parameters and out-of-plane stiffness parameters of each ply area. It can be understood that in this embodiment, the ply thickness of each ply area obtained by the finite element method is rounded and discretized, so that the ply thickness of the plies at different angles in each ply area can be equal to the overall ply thickness of the ply area after superposition.

[0073] In the composite material ply loss optimization design method based on the ply database of the present application, in step three, the connection matrix generated according to the connection relationship between each ply area is an n×n matrix, where n is the number of ply areas. In the connection matrix, different identifiers are used to represent the relationship between two ply areas. In one embodiment of the present application, the first identifier is used to represent that there is a connection relationship between the two ply areas; the second identifier is used to represent that there is no connection relationship between the two ply areas. According to the connection matrix, the plies in each ply area are divided into three types: global shared plies, local shared plies, and unique plies. The global shared plies in the ply area are the plies shared by all ply areas; the local shared plies in the ply area are the plies shared by the ply area and other ply areas with a connection relationship; the unique plies in the ply area are the unique plies in the ply area. Finally, the overall ply thickness and ply ratio of each ply area are allocated to obtain the ply thickness and ply ratio of different types of plies in the ply area.

[0074] In the composite material layer loss optimization design method based on the ply database of the present application, in step 4, the ply sequence of different types of plies is matched in the composite material ply database according to the ply thickness and ply ratio, and each type of ply may match multiple ply sequences. If the corresponding ply thickness and ply ratio data do not exist in the composite material ply database, the corresponding ply data in the composite material ply database can be expanded using a fast generation algorithm. In step 5, a group is selected from the ply sequence of each type of ply to generate the overall ply sequence.

[0075] In the composite material layer loss optimization design method based on the ply database of the present application, in step six, constructing a variable thickness composite material structure finite element model according to the overall ply sequence includes: obtaining an initial finite element model; constructing a variable thickness composite material structure finite element model based on the initial finite element model according to the overall ply sequence. The variable thickness composite material structure finite element model can be quickly obtained by simply updating the ply information of the initial finite element model according to the overall ply sequence.

[0076] The composite material ply loss optimization design method based on the ply database of the present application preferably adds an overall ply sequence adjustment step in step seven, specifically:

[0077] Determine whether each ply area of ​​the finite element model of a variable thickness composite material structure meets the strength, stiffness and stability requirements at the same time;

[0078] If yes, before preserving the overall ply order also include:

[0079] The number of unique plies in the ply area where the design margin meets the requirements is reduced to obtain the adjusted overall ply sequence, and a finite element model of the variable thickness composite material structure is constructed according to the adjusted overall ply sequence. It is determined whether each ply area of ​​the finite element model of the variable thickness composite material structure meets the strength, stiffness and stability requirements at the same time. If so, the adjusted overall ply sequence is retained; if not, the overall ply sequence before adjustment is retained.

[0080] In this embodiment, when the overall ply sequence meets the index requirements, the weight reduction design is continued, and the design margin of each ply region is checked to determine whether the number of plies can be reduced in the ply region where the design margin meets the requirements, and redundant plies can be deleted to reduce the weight of the structure. If there is no weight reduction space, the overall ply sequence design scheme before adjustment is retained. In order to reduce the calculation time, the adjustment step of the overall ply sequence can be performed only once or a limited number of times. It can be understood that when judging whether the design margin meets the requirements, the strength design margin, stiffness design margin and stability design margin must all meet the requirements.

[0081] Further, it is determined whether each ply region of the finite element model of the variable thickness composite material structure satisfies the strength, stiffness and stability requirements at the same time;

[0082] If not, increase the number of unique plies in the ply areas that cannot simultaneously meet the strength, stiffness and stability requirements to obtain an adjusted overall ply sequence, and construct a finite element model of a variable thickness composite material structure according to the adjusted overall ply sequence to determine whether each ply area of ​​the finite element model of the variable thickness composite material structure simultaneously meets the strength, stiffness and stability requirements; if so, retain the adjusted overall ply sequence; if not, delete the overall ply sequence before adjustment.

[0083] In this embodiment, when the overall layup sequence does not meet the index requirements, under the premise of a given weight gain threshold, the unique layup in the corresponding layup area is appropriately increased so that each layup area of ​​the finite element model of the variable thickness composite material structure can simultaneously meet the strength, stiffness and stability requirements. If the overall layup sequence still cannot meet the requirements after adjustment, the overall layup sequence before adjustment is deleted.

[0084] The composite material ply dropping optimization design method based on the ply database of the present application selects the overall ply sequence corresponding to the variable thickness composite material structure finite element model with the minimum mass by traversing all combinations of the global shared ply sequence, the local shared ply sequence and the unique ply sequence.

[0085] The composite material ply dropping optimization design method based on the ply database of the present application adopts a dual isogenic genetic algorithm to generate a composite material ply database that meets engineering requirements, and then adopts the finite element method to obtain the ply thickness and ply ratio of each ply area, divides the different types of plies through the connection matrix, and determines the ply data of each type of ply. The ply sequence of each type of ply is obtained by matching the ply data in the composite material ply database, and the finite element method is used to check and verify the ply sequence to obtain the optimal ply design scheme. The present application can quickly realize the composite material ply dropping optimization design, give full play to the advantages of the engineering ply database, avoid the problems such as the low efficiency of the optimization algorithm in the ply dropping process, and provide an efficient means for the ply optimization design of large composite material structures.

[0086] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A composite material layer loss optimization design method based on a layer database, characterized in that: include: Step 1: Build a composite material layup database; Step 2: obtaining multiple ply regions of the variable thickness composite material structure, and determining the ply thickness and ply ratio of each ply region; Step 3: Generate a connection matrix according to the connection relationship between each ply area, and divide the plies in each ply area into three types: global shared plies, local shared plies and unique plies according to the connection matrix, and determine the ply thickness and ply ratio of the global shared plies, the ply thickness and ply ratio of the local shared plies, and the ply thickness and ply ratio of the unique plies in each ply area; Step 4: matching a global shared ply sequence having the same ply thickness and ply ratio as the global shared ply in the composite material ply database; Matching a local shared ply sequence having the same ply thickness and ply ratio as the local shared ply in the composite material ply database; Matching a unique ply sequence having the same ply thickness and ply ratio as the unique ply in the composite material ply database; Step 5: Select a set of global shared ply sequence, local shared ply sequence and unique ply sequence to generate an overall ply sequence; Step 6: constructing a finite element model of a variable thickness composite material structure according to the overall ply sequence; Step 7: Determine whether each ply area of ​​the variable thickness composite material structure finite element model meets the strength, stiffness and stability requirements at the same time; If so, retain the overall ply sequence; Calculate the mass of the finite element model of the variable thickness composite material structure corresponding to the retained overall ply sequence; Return to step five, reselect a set of global shared layup sequences, local shared layup sequences and unique layup sequences to generate a new overall layup sequence, until all combinations of global shared layup sequences, local shared layup sequences and unique layup sequences are traversed, and the overall layup sequence corresponding to the variable thickness composite material structure finite element model with the smallest mass is screened out.

2. The composite material layer loss optimization design method based on the layer database according to claim 1 is characterized in that: In step 1, a dual isogenic genetic algorithm is used to construct a composite material ply database, where: Constraints include: balance constraint, symmetry constraint, outer surface ±45 degree constraint, continuous ply number constraint, and ply ratio constraint; The fitness functions include: compression fitness function and shear fitness function; The penalty functions include: continuous ply penalty function, outer surface ±45 degree penalty function, and adjacent ply angle penalty function.

3. The composite material layer loss optimization design method based on the layer database according to claim 2 is characterized in that: In step 2, a plurality of ply regions of the variable thickness composite material structure are obtained, and the ply thickness and ply ratio of each ply region are determined, including: Acquire multiple ply regions of a composite structure with variable thickness; The various ply regions of the variable thickness composite material structure are set to a balanced symmetrical laminate structure; Determine the initial ply thickness and ply ratio for each ply area; The plying order of each ply area of ​​the variable thickness composite material structure is set to 0° plying, +45° plying, -45° plying, and 90° plying from the outer surface to the middle surface; Constructing a finite element model of a composite material structure with variable thickness, optimizing the finite element model of the composite material structure with variable thickness, and outputting the ply thickness and ply ratio of each ply area that simultaneously meets the requirements of strength, stiffness, and stability; The ply thickness of each ply area is rounded off to obtain the number of plies at each angle.

4. The composite material layer loss optimization design method based on the layer database according to claim 3 is characterized in that: In step three, The connection matrix is ​​an n×n matrix, where n is the number of ply regions; In the connection matrix: The first identifier indicates that there is a connection relationship between the two ply regions; The second identifier indicates that there is no connection relationship between the two ply regions.

5. The composite material layer loss optimization design method based on the layer database according to claim 4 is characterized in that: In step three, The global shared plies in the ply area are the plies common to all ply areas; The local shared plies in the ply area are plies shared by the ply area and other ply areas having a connection relationship; A unique ply in a ply zone is a ply that is unique to that ply zone.

6. The composite material ply loss optimization design method based on ply database according to claim 5 is characterized in that: In step six, a finite element model of a variable thickness composite material structure is constructed according to the overall ply sequence, including: Obtaining an initial finite element model; A variable thickness composite material structure finite element model is constructed based on the initial finite element model according to the overall ply sequence.

7. The composite material ply loss optimization design method based on ply database according to claim 6 is characterized in that: In step seven, it is determined whether each ply region of the variable thickness composite material structure finite element model satisfies the strength, stiffness and stability requirements at the same time; If yes, before preserving the overall ply order also include: The number of unique plies in the ply area where the design margin meets the requirements is reduced to obtain an adjusted overall ply sequence, a finite element model of a variable thickness composite material structure is constructed according to the adjusted overall ply sequence, and it is determined whether each ply area of ​​the finite element model of the variable thickness composite material structure meets the strength, stiffness and stability requirements at the same time. If so, the adjusted overall ply sequence is retained; if not, the overall ply sequence before adjustment is retained.

8. The composite material ply loss optimization design method based on ply database according to claim 7 is characterized in that: In step seven, it is determined whether each ply region of the variable thickness composite material structure finite element model satisfies the strength, stiffness and stability requirements at the same time; If not, increase the number of unique plies in the ply areas that cannot simultaneously meet the strength, stiffness and stability requirements to obtain an adjusted overall ply sequence, and construct a finite element model of a variable thickness composite material structure according to the adjusted overall ply sequence to determine whether each ply area of ​​the finite element model of the variable thickness composite material structure simultaneously meets the strength, stiffness and stability requirements; if so, retain the adjusted overall ply sequence; if not, delete the overall ply sequence before adjustment.

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