Parametric variable sequence modeling method for composite material thickness-gradient ply structures

Abstract

This invention provides two parametric variable layer sequence modeling methods for composite material thickness-varying ply structures, addressing different scenarios. These methods comprehensively consider factors such as the geometric shape and single-layer ply thickness of the thickness-varying ply structure. A control point matrix corresponding to the cross-section of the composite material thickness-varying ply structure and its associated control point numbering matrix are constructed. By adjusting the positions of elements in the control point numbering matrix, parametric control of the composite material ply sequence variation can be achieved. In practical implementation, only parameters such as single-layer ply thickness need to be adjusted according to the actual situation to quickly establish solid models of ply schemes with different stacking orders. This significantly reduces repetitive modeling work and helps improve the efficiency of the composite material ply optimization process.

Description

Technical Field

[0001] This invention belongs to the field of composite material structure design, specifically involving a method for modeling variable layer sequence of composite material thickness-gradient layup structures. Background Technology

[0002] Composite materials are a large class of new materials, characterized by high strength, high stiffness, and light weight. They also possess a range of advantages such as fatigue resistance, vibration reduction, high temperature resistance, and designability, leading to their widespread application in industries such as aerospace. Typical composite material structures are mostly ply-layout structures, composed of multiple single-layer plates, each with the same thickness. However, in complex structures, thickness gradients are often present to meet component shape and assembly requirements, thus the application of thickness-gradient ply-layout structures is becoming increasingly widespread.

[0003] With the increasing demands for the performance of composite material structures, it is often necessary to optimize the stacking sequence of ply structures in practical applications. However, for thickness-gradient ply structures, there is currently no efficient parametric variable layer sequence modeling method, which makes it impossible to quickly iterate the design variable of ply stacking sequence during the optimization process, thus hindering the further application of thickness-gradient ply structures.

[0004] Therefore, how to achieve parametric variable layer sequence modeling of thickness-gradient ply structures and accelerate the structural optimization design process is an important and difficult-to-solve key technology in this field. Summary of the Invention

[0005] In response to the problems raised in the background art, and in order to improve the modeling efficiency of composite material structures with gradually varying thickness and reduce the amount of manual work in the modeling process, this invention proposes two parametric variable layer sequence modeling methods for composite material structures with gradually varying thickness under different conditions, so as to meet the need for rapid iteration of the stacking order as a design variable in the process of efficient optimization.

[0006] To achieve the above objectives, the present invention has designed the following technical solution:

[0007] Option 1:

[0008] A parametric variable-sequence modeling method for composite material thickness-gradient ply structures is provided for thickness-gradient ply structures composed of several plyes, with cross-sections extracted from different locations resulting in identical cross-sectional shapes. The modeling method is characterized by the following steps:

[0009] Step 1. Extract any cross section from the solid model of the thickness-gradient plywood structure;

[0010] Step 2. Based on the current cross-sectional dimensions and the thickness of each ply layer, generate a rectangular planar dot matrix, wherein the spacing between adjacent points in the planar dot matrix is ​​equal to the thickness of each ply layer; combining the initial distribution state of each ply's cross-section on the current cross-section, select points at corresponding positions from the planar dot matrix to serve as control points for each ply on the current cross-section, forming a control point matrix, and assigning a number to each control point; the outer contour of the control point matrix is ​​adapted to the shape of the current cross-section.

[0011] Step 3. Construct an initial control point numbering matrix. The initial control point numbering matrix consists of control point numbers and empty space symbols. The position of each control point number in the matrix corresponds to the position of the control point in the planar point matrix. The empty space symbols correspond to the points in the planar point matrix that have not been selected as control points and are filled in the matrix.

[0012] Step 4. Based on the initial control point numbering matrix of the current cross section, perform parameterized change sequence operation on the control points of the corresponding ply on the current cross section;

[0013] The parameterized change sequence operation is as follows: according to the change sequence scheme, adjust the position of the control point number of the corresponding ply in the initial control point number matrix to obtain the target control point number matrix. Then, according to the position of the control point number of each ply in the target control point number matrix, determine the new position of the control point of each ply in the control point matrix, and connect the new positions to obtain the projection line of each ply on the current cross section after the change sequence.

[0014] Step 5. Following the direction of the thickness-gradient ply structure, stretch the projection lines of each ply after the change of ply sequence to generate the corresponding layer structure of each ply, and obtain the target ply scheme.

[0015] Based on Option 1, further improvements or preferred options include:

[0016] Furthermore, step 2 includes the following steps:

[0017] Step 2.1. For the extracted current cross-section k, generate a planar dot matrix, where the cross-section k is located within the area covered by the planar dot matrix;

[0018] The planar lattice includes There are 10 points, of which 10 are points. The symbol is for rounding up; a is the maximum thickness of cross section k; b is the minimum thickness of cross section k; h is the height of cross section k; and x is the thickness of a single layer of the ply.

[0019] The row direction of the planar point lattice is parallel to the thickness direction of the cross-section k, and the column direction of the planar point lattice is parallel to the height direction of the cross-section k. All points of the planar point lattice are numbered a. ij , where i is the row of the point. j represents the column where the point is located. Obtain an initial numbering matrix;

[0020] Step 2.2. Select suitable points from the planar point lattice as control points for each ply of cross section k, forming a control point lattice, including:

[0021] Step 2.2.1. Determine the control points of the outermost ply

[0022] For the left and right sides of cross section k, in the planar point lattice, the point closest to one side of the cross section is determined row by row as a candidate point for the outermost ply control point of the cross section on that side; among the remaining points, the point closest to the other side of cross section k is determined row by row as a candidate point for the outermost ply control point of the other side of the cross section.

[0023] Then delete the points that are outside the outermost ply candidate points on the left and right sides, and use the points that are between the outermost ply candidate points on the left and right sides as candidate points for intermediate ply control points.

[0024] Determine whether the distance deviation between each candidate point of the outermost ply and its corresponding side is within a preset range. If the distance deviation of the candidate point exceeds the preset range, then delete it.

[0025] Step 2.2.2. Determine the control points of the intermediate ply

[0026] Among the candidate points for intermediate ply control points, points located in the same column are used as control points for the same intermediate ply. If there is only one remaining intermediate ply control point candidate point in the column, it is deleted.

[0027] The control point matrix has now been obtained.

[0028] Furthermore, assuming the side of the cross-section k with the maximum thickness a is the bottom edge of the cross-section, in step 2.1, when generating the planar point matrix, the first or last point of the bottom row of the planar point matrix is ​​placed on the starting or ending point of the bottom edge, with the starting or ending position of the bottom edge as a reference.

[0029] Furthermore, step 3 includes the following steps:

[0030] In the initial numbering matrix of the current cross section k, the numbers corresponding to the points deleted in step 2 are adjusted to empty symbols to obtain the initial control point numbering matrix.

[0031] Furthermore, step 4 includes the following steps:

[0032] Step 4.1. Suppose that the two intermediate plies that need to be swapped according to the variable sequence scheme are ply M and ply N, and that the number of control points contained in ply N on the cross section k is greater than or equal to the number of control points contained in ply M.

[0033] In the initial control point numbering matrix, the control point numbers corresponding to ply M and ply N are adjusted row by row in matrix A. k The adjusted control point numbering matrix will be used as the target control point numbering matrix, and the adjustment rules are as follows:

[0034] 1) If the row contains both control point numbers for ply M and ply N, then directly swap the positions of the control point numbers for ply M and ply N in the initial control point number matrix.

[0035] 2) If there is a control point number for ply N but no control point number for ply M in the row, then determine whether there are control point numbers for other intermediate ply between ply N and the control point number of the outermost ply closest to ply M.

[0036] If there are control point numbers for other intermediate plies, first move the control point number of ply N out of the row, then move the control point numbers of the other intermediate plies in the row one point towards ply N, and then fill the new empty space created by the shifting of the control point numbers of the other intermediate plies in the row with the control point numbers of ply N.

[0037] If there are no other intermediate ply control point numbers, then the position of the control point number of ply N remains unchanged;

[0038] Step 4.2. Based on the position of the control point number corresponding to each ply in the target control point number matrix, reconnect the control points of each ply in the control point matrix of cross section k to obtain the projection lines of each ply on the cross section k after the ply sequence is changed.

[0039] Option 2:

[0040] A parametric variable-sequence modeling method for composite material thickness-gradient ply structures is provided for thickness-gradient ply structures composed of several ply layers, from which cross-sections are extracted at different locations, resulting in cross-sectional shapes that are not entirely identical. The modeling method is characterized by the following steps:

[0041] Step 1. Extract n cross sections from the solid model of the thickness-gradient ply structure, where n is a natural number greater than 1. For the n cross sections, perform steps 2 to 3 respectively through a loop operation.

[0042] Step 2. Based on the current cross-sectional dimensions and the thickness of each ply layer, generate a rectangular planar dot matrix. The spacing between adjacent points in the planar dot matrix is ​​equal to the thickness of each ply layer. Combining the initial distribution of each ply section on the current cross-section, select points at corresponding positions from the planar dot matrix to serve as control points for each ply on the current cross-section, forming a control point matrix. Assign a number to each control point, and ensure that the outer contour of the control point matrix matches the shape of the current cross-section.

[0043] Step 3. Construct an initial control point numbering matrix. The initial control point numbering matrix consists of control point numbers and empty space symbols. The position of each control point number in the matrix corresponds to the position of the control point in the planar point matrix. The empty space symbols correspond to points in the planar point matrix that have not been selected as control points.

[0044] Step 4. Determine the ply correspondence between each cross section and its adjacent cross sections, including:

[0045] The line connecting the control points of each ply on the cross section is regarded as the projection line of that ply on the cross section.

[0046] If the current cross section contains the same number of projection lines as its adjacent cross section, then it is determined that the projection lines of the current cross section and the adjacent cross section are in a one-to-one correspondence in the front-back direction.

[0047] If the number of projection lines contained in the current cross section is different from that in its adjacent cross section, let the current cross section contain two outermost plies and s middle plies, and the adjacent cross section contain two outermost plies and t middle plies, where s≠t. Then, first determine the correspondence between the projection lines of the outermost plies on the left and right sides of the current cross section and the adjacent cross section. For the remaining middle plies, take the value of o equal to the smaller value of s and t. Using the projection line of the outermost ply on one side as the reference, determine whether the projection lines of the o middle plies closest to the reference in the current cross section and its adjacent cross section are in a one-to-one correspondence in the front-back direction.

[0048] The projection lines in the front-to-back direction between the current cross section and its adjacent cross section belong to the same ply.

[0049] Step 5. Based on the preset variable sequence scheme and the ply correspondence between cross sections, determine the cross section to be executed for variable sequence, as well as the ply control points that need to be changed on the corresponding cross section. Then, based on the initial control point number matrix, perform parameterized variable sequence operation on the corresponding ply control points on the corresponding cross section.

[0050] The parameterized layer sequence change operation is as follows: adjust the position of the control point number of the corresponding ply in the initial control point number matrix of the current cross section to obtain the target control point number matrix. Then, based on the position of the control point number of each ply in the target control point number matrix, determine the new position of the control point of each ply in the control point matrix, and connect the new positions to obtain the projection line of each ply on the current cross section after the layer sequence change.

[0051] Step 6. After changing the layer sequence, connect the projection lines of each cross section corresponding to the same ply by connecting control points one by one to generate the layer structure corresponding to each ply and obtain the target ply scheme.

[0052] Based on Option 2, further improvements or preferred options include:

[0053] Furthermore, step 2 includes the following steps:

[0054] Step 2.1. For the extracted current cross-section k, generate a planar dot matrix, where the cross-section k is located within the area covered by the planar dot matrix;

[0055] The planar lattice includes There are 10 points, of which 10 are points. The symbol is for rounding up; a is the maximum thickness of cross section k; b is the minimum thickness of cross section k; h is the height of cross section k; and x is the thickness of a single layer of the ply.

[0056] The row direction of the planar point lattice is parallel to the thickness direction of the cross-section k, and the column direction of the planar point lattice is parallel to the height direction of the cross-section k. All points of the planar point lattice are numbered a. ij , where i is the row of the point. j represents the column where the point is located. Obtain an initial numbering matrix;

[0057] Step 2.2. From the planar point lattice, select suitable points as control points for each ply of cross section k, forming a control point lattice, including:

[0058] Step 2.2.1. Determine the control points of the outermost ply

[0059] For the left and right sides of cross section k, in the planar point lattice, the point closest to one side of the cross section is determined row by row as a candidate point for the outermost ply control point of the cross section on that side; among the remaining points, the point closest to the other side of cross section k is determined row by row as a candidate point for the outermost ply control point of the other side of the cross section.

[0060] Then delete the points that are outside the outermost ply candidate points on the left and right sides, and use the points that are between the outermost ply candidate points on the left and right sides as candidate points for intermediate ply control points.

[0061] Determine whether the distance deviation between each candidate point of the outermost ply and its corresponding side is within a preset range. If the distance deviation of the candidate point exceeds the preset range, then delete it.

[0062] Step 2.2.2. Determine the control points of the intermediate ply

[0063] Among the candidate points for intermediate ply control points, points located in the same column are used as control points for the same intermediate ply. If there is only one remaining intermediate ply control point candidate point in the column, it is deleted.

[0064] This gives us the control point lattice for the current cross-section k.

[0065] Furthermore, assuming the side of the cross-section k with the maximum thickness a is the bottom edge of the cross-section, in step 2.1, when generating the planar point matrix, the first or last point of the bottom row of the planar point matrix is ​​placed on the starting or ending point of the bottom edge, with the starting or ending position of the bottom edge as a reference.

[0066] Furthermore, step 3 includes the following steps:

[0067] In the initial numbering matrix of the current cross section k, the numbers corresponding to the points deleted in step 2 are adjusted to empty symbols to obtain the initial control point numbering matrix.

[0068] Furthermore, in step 5, the parameterized variable sequence operation includes the following steps:

[0069] Step 5.1. Let the two intermediate plies that need to be swapped according to the variable sequence scheme be ply M and ply N, and the number of control points of ply N on the current cross section k is greater than or equal to that of ply M;

[0070] In the initial control point numbering matrix of cross section k, the control point numbers corresponding to ply M and ply N are adjusted row by row in matrix A. k The adjusted control point numbering matrix will be used as the target control point numbering matrix, and the adjustment rules are as follows:

[0071] 1) If the row contains both control point numbers for ply M and ply N, then directly swap the positions of the control point numbers for ply M and ply N in the initial control point number matrix.

[0072] 2) If there is a control point number for ply N but no control point number for ply M in the row, then determine whether there are control point numbers for other intermediate ply between ply N and the control point number of the outermost ply closest to ply M.

[0073] If there are control point numbers for other intermediate plies, first move the control point number of ply N out of the row, then move the control point numbers of the other intermediate plies in the row one point towards ply N, and then fill the new empty space created by the shifting of the control point numbers of the other intermediate plies in the row with the control point numbers of ply N.

[0074] If there are no other intermediate ply control point numbers, then the position of the control point number of ply N remains unchanged;

[0075] Step 5.2. Based on the position of the control point number corresponding to each ply in the target control point number matrix, reconnect the control points of each ply in the control point matrix of cross section k to obtain the projection lines of each ply on the current cross section k after the ply sequence is changed.

[0076] The beneficial effects of this invention are:

[0077] Based on the same core technology concept, this invention provides two parametric variable-sequence modeling methods for composite material thickness-gradient ply structures under different conditions. Taking into account factors such as the geometric shape and single-layer ply thickness of the thickness-gradient ply structure, a control point matrix corresponding to the cross-section of the composite material thickness-gradient ply structure and its associated control point numbering matrix are constructed. By adjusting the positions of elements in the control point numbering matrix, parametric control of the ply sequence variation of the composite material can be achieved. In practical implementation, only the input parameters such as single-layer ply thickness need to be adjusted according to the actual situation to quickly establish solid models of ply schemes with different stacking sequences. This significantly reduces repetitive modeling work and helps improve the efficiency of the composite material ply optimization process.

[0078] Furthermore, the method proposed in this invention is applicable not only to planar ply structures, but also to variable sequence parametric modeling of complex curved ply structures. Attached Figure Description

[0079] Figure 1 This is a flowchart of the parametric variable layer sequence modeling method for composite material thickness-gradient layup structures according to the present invention;

[0080] Figure 2 This is a schematic diagram of the solid model and extracted cross-section of the composite material thickness gradient layup structure in Example 1;

[0081] Figure 3 This is a schematic diagram of the structure of any cross-section in Example 1;

[0082] Figure 4 This is a schematic diagram of the formation process of the control point lattice and ply projection lines in Example 1;

[0083] Figure 5This is a schematic diagram of the control point connection lines and projection lines of each ply after the ply sequence was changed in Example 1;

[0084] Figure 6 This is a schematic diagram (top view) showing the ply correspondence between cross sections in Example 2;

[0085] Figure 7 This is a schematic diagram (side view) showing the connection of control points for the projection lines of the same ply between cross sections in Example 2. Detailed Implementation

[0086] To clarify the technical solution of the present invention, the present invention will be further explained below with reference to specific embodiments.

[0087] This invention discloses a parametric variable-sequence modeling method for composite material thickness-gradient ply structures. This method is applied to composite materials with thickness-gradient ply structures, establishing different stacking orders in their solid model (geometric model). The method is implemented using a computer device capable of running material analysis software. The thickness-gradient ply structure meets the following conditions: the overall thickness of any cross-section continuously changes from one end to the other; and the perpendicular projection of the side with the smaller thickness onto the side with the larger thickness falls within the range of the side with the larger thickness.

[0088] like Figure 1 The flowchart shown is for a thickness-gradient layup structure where the cross-sectional shape is uncertain. The process of this invention is as follows:

[0089] First, for the solid model of the thickness gradient layup structure in the input system, n cross sections are extracted along the extension direction of the thickness gradient layup structure, and it is determined whether the shapes of the n cross sections are the same (the shape includes size factors, that is, the same shape also includes the same size). The cross section refers to the section perpendicular to the extension direction of the thickness gradient layup structure.

[0090] If the shapes of the n cross sections are exactly the same, then refer to Example 1 (Scheme 1 Example);

[0091] If the shapes of the n cross sections are not exactly the same, then refer to Example 2 (Scheme 2 Example).

[0092] This invention is applicable to the parametric modeling of the layer sequence of continuously varying ply structures with single-layer planar equal thickness and single-layer curved equal thickness. Ply structures with the same cross-sectional shape correspond to single-layer planar equal thickness, while ply structures with different cross-sectional shapes correspond to single-layer curved equal thickness.

[0093] Based on the aforementioned judgment results:

[0094] If the n cross-sections have the same shape, then the control point layout scheme of the n cross-sections is also the same. Therefore, the control point layout scheme of any cross-section can be determined. The line connecting the control points of each ply is the projection line of the ply on the current cross-section. To obtain the ply scheme of the solid model, the projection lines of each ply are stretched in the direction of the thickness gradient ply structure. From the line to the surface, the ply scheme of the solid model can be obtained, including the initial ply scheme and the ply scheme after changing the layer sequence.

[0095] If the shapes of the n cross sections are not completely the same, then the control point layout schemes of the n cross sections are also not completely the same. Therefore, for each extracted cross section, it is necessary to determine its control point layout scheme separately. To obtain the layup scheme of the solid model, it is necessary to connect the control points of each layup on each cross section as the projection line of the layup on the current cross section. Then, connect the control points of the projection lines of the same layup on each cross section to obtain the layup scheme of the solid model, including the initial layup scheme and the layup scheme after changing the layer order.

[0096] Example 1:

[0097] like Figure 2 The diagram shows a thickness-gradient plywood structure that extends longitudinally along a horizontal plane. By extracting and comparing its cross-sections, it is determined that the cross-sectional shapes are identical at all points. The parametric variable sequence modeling method for this thickness-gradient plywood structure is as follows:

[0098] Step 1. Extract any cross section from the solid model of the thickness-gradient ply structure.

[0099] Step 2. Based on the current cross-sectional dimensions and the thickness of each ply layer, generate a rectangular planar dot matrix. The spacing between adjacent points in the planar dot matrix is ​​equal to the thickness of each ply layer. Combining the initial distribution of each ply section on the current cross-section, select points at corresponding positions from the planar dot matrix to serve as control points for each ply on the current cross-section, forming a control point matrix. Assign numbers to each control point, and ensure that the outer contour of the control point matrix matches the shape of the current cross-section.

[0100] The specific implementation process of step 2 includes the following steps:

[0101] Step 2.1. Extract any cross section k, where k is a natural number from 1 to n. Based on the given thickness x of a single ply, divide its height and thickness equally. Generate a planar lattice based on the position of cross section k in its Cartesian coordinate system. This planar lattice contains... There are 10 points, of which 10 are points. The symbol is for rounding up. a is the maximum thickness of cross-section k, b is the minimum thickness of cross-section k, a>b>0, and h is the height of cross-section k.

[0102] A planar lattice is superimposed on a cross-section k, and the cross-section k is covered by the planar lattice. The row direction of the planar lattice is parallel to the thickness direction of the cross-section k, and the column direction of the planar lattice is parallel to the height direction of the cross-section k; all points of this planar lattice are numbered a. ij Let i be the row of the point and j be the column of the point. At this point, we can obtain an initial numbering matrix.

[0103] like Figure 3 In the example shown, the left side of the cross section k is a curve extending downward and to the left, and the right side is a vertical line perpendicular to the top and bottom edges. Its thickness gradually increases from top to bottom. If the top edge is projected vertically onto the bottom edge, it falls within the range of the bottom edge, which meets the conditions for the application of the method of the present invention. Figure 3 The overall shape of the cross section k shown is approximately a right trapezoid, with a maximum thickness a of 2.5 mm, a minimum thickness b of 0.5 mm, and a height h of 3 mm. In this embodiment, the given value of x is 0.5 mm.

[0104] Substituting the above dimensions into the formula for the planar dot matrix, we obtain that the planar dot matrix contains 7×6 points. 7 is the total number of rows in the planar dot matrix, which is obtained by adding 1 to the height h of the equally divided cross-section, i.e., 1≤i≤7; 6 is the total number of columns in the planar dot matrix, which is obtained by adding 1 to the maximum thickness of the equally divided cross-section, i.e., 1≤j≤6; in this planar dot matrix, the distance between two adjacent points is equal to x, i.e., 0.5mm.

[0105] Step 2.2. Select suitable points from the planar point lattice as control points for each ply to form a control point lattice for cross-section k. The specific process includes:

[0106] Step 2.2.1. Determine the control points of the outermost ply

[0107] For the left and right sides of cross section k, in the planar point lattice, firstly, determine the point closest to the left or right side of cross section k row by row as the candidate point for the outermost ply control point on the left or right side of the cross section. Then, among the remaining points, determine the point closest to the other side of cross section k row by row as the candidate point for the outermost ply control point on the other side of the cross section. Then, retain the points between the candidate points for the outermost ply control points on the left and right sides as the candidate points for the middle ply control point, and delete the points outside the candidate points for the outermost ply control points on the left and right sides to obtain a coarse registration point lattice whose outer contour basically corresponds to the cross section k.

[0108] Determine whether the distance deviation between each candidate control point and its corresponding side is within a preset range. If the distance deviation of a control point exceeds the preset range, then remove it from the candidate points.

[0109] The preset range of the distance deviation is a value set manually, which can be obtained based on experience or multiple experiments;

[0110] In this embodiment: as Figure 4 As shown in the dot matrix on the left, the first point on the far left of each row is the point closest to the left side of the cross-section k. However, since the distance deviation between the first point on the left of the second and fourth rows and the left side of the cross-section is large, exceeding the preset range of this embodiment, they are deleted from the dot matrix. The first point on the far right of each row is the point closest to the right side of the cross-section k. They are all on a vertical line and coincide with the right side of the cross-section k. The distance deviation does not exceed the preset range, so they are all selected as control points for the right side.

[0111] Step 2.2.2. Determine the control points of the intermediate ply

[0112] Among the candidate points for intermediate ply control points, points located in the same column are considered control points for the same ply. If only one intermediate ply control point candidate remains in that column, it is deleted. Figure 4 The second point from the left in the bottom row of the left section is the control point for the outermost ply on the left. Connecting upwards, there are no other points in the vertical direction that can serve as control points for intermediate plies, so this point is deleted. The final control point matrix and its connections are as follows: Figure 4 As shown in the middle section.

[0113] Step 3. Construct an initial control point numbering matrix. The initial control point numbering matrix consists of control point numbers and empty space symbols. The position of each control point number in the matrix corresponds to the position of the control point in the planar point matrix. The empty space symbols correspond to the points in the planar point matrix that have not been selected as control points and are filled in the matrix.

[0114] The specific implementation process of step 3 is as follows:

[0115] For the cross section k, based on the planar point matrix obtained in step 2.1, an initial numbering matrix is ​​constructed. The numbering positions of the points deleted in step 2 are all set to 0, which are regarded as empty positions, and the following initial control point numbering matrix A is obtained:

[0116]

[0117] In the cross section k, the position of each ply section is determined by its control points, and the position of each ply control point in the control point matrix corresponds to the position of its number in the control point numbering matrix. As shown in the control point numbering matrix A, there are five plies from left to right, and their corresponding control point numbering sets are: {a 71 ,a 62 ,a 53 ,a 34 ,a 15}、{a 73 ,a 63}、{a 74 ,a 64 ,a 54}、{a 75 ,a 65 ,a 55 ,a 45 ,a 35}、{a 76 ,a 66 ,a 56 ,a 46 ,a 36 ,a 26 ,a 16 This enables the parameterization of thickness-gradient ply structures.

[0118] Step 4. Based on the initial control point numbering matrix of the current cross section, perform parameterized change sequence operation on the control points of the corresponding ply on the current cross section;

[0119] The specific implementation process of the parameterized variable order operation is as follows:

[0120] Step 4.1. Suppose that according to the variable sequence scheme, the two plies that need to be swapped are plies M and plies N. Both plies M and plies N are intermediate plies, and on the cross section k, the number of control points contained in plies N is greater than or equal to the number of control points contained in plies M.

[0121] In the initial control point numbering matrix A of the cross section k, the positions of the control point numbers contained in ply M and ply N in the matrix are adjusted row by row to obtain the target control point numbering matrix B. The adjustment rules are as follows:

[0122] 1) If the row contains both control point numbers for ply M and ply N, then directly swap the positions of the control point numbers for ply M and ply N in matrix A.

[0123] 2) If there is a control point number for ply N but no control point number for ply M in the row, then determine whether there are control point numbers for other intermediate ply between ply N and the control point number of the outermost ply closest to ply M, and ensure that the number of positions occupied by the control point number in matrix A remains unchanged.

[0124] If there are control point numbers for other intermediate plies, first move the control point number of ply N out of the row, then move the control point numbers of the other intermediate plies in the row one point towards ply N, and then fill the control point numbers of ply N in the row into the newly vacated positions in the row after the other intermediate plies have been moved.

[0125] If there are no other intermediate ply control point numbers, then the position of the control point number of ply N in the matrix remains unchanged;

[0126] Step 4.2. Based on the position of the control point number corresponding to each ply in the target control point number matrix B, reconnect the control points of each ply in the control point matrix on the cross section k to obtain the projection line of each ply on the cross section k after the ply sequence is changed.

[0127] This embodiment uses the variation of the second and fourth plies from left to right as an example for illustration:

[0128] In the 6th and 7th rows of the initial control point numbering matrix A, the control point numbers for the second and fourth plies are both included. According to the rules described above, the control point numbers for the second ply are assigned to {a}. 63 ,a 73} and the control point number of the fourth ply {a 65 ,a 75 Simply swap their positions;

[0129] In rows 5, 4, and 3 of matrix A, only the control point numbers for the fourth ply are present, while the control point numbers for the second ply are absent. The control point number for the fourth ply is a. 35 a 45 a 55 Directly swapping these three points would exceed the boundary, so we first move them out to create empty spaces. The control point numbering matrix at this point is as follows:

[0130]

[0131] In the 5th row of matrix A, the control point number of the fourth ply is a. 55 Control point number a of the outermost ply on the left 53 Between them, there is also a control point numbered a for the third ply. 54 Therefore, a 54 Move to the original matrix A a 55 At this location, the control point numbering matrix is ​​as follows:

[0132]

[0133] Next, a 55 Fill a into the original matrix A 54 In position a 54 The empty space created after translation;

[0134] In rows 4 and 3 of matrix A, since there are no control point numbers for other intermediate plies between the control point numbers of the fourth ply and the outermost ply on the left, the control point number of the fourth ply is set to a. 35 and a 45Returning them to their original positions, the final target control point numbering matrix B is formed, and its construction is as follows:

[0135]

[0136] Then, according to the construction of matrix B, the new positions of each ply control point in the control point lattice after the change of ply sequence can be determined.

[0137] Step 5. Generate the target layup scheme after the change of layup sequence based on the layup projection lines after the change of layup sequence.

[0138] In this embodiment, the ply projection lines after the change of layer sequence are as follows: Figure 5 As shown, the method for generating the target ply scheme based on the ply projection lines after the change of ply sequence is as follows: stretch the ply projection lines after the change of ply sequence longitudinally to the front and rear end faces of the solid model to generate the layer structure of each ply, thus obtaining the ply scheme after the change of ply sequence for the thickness gradient ply structure.

[0139] Example 2:

[0140] The thickness-gradient layup structure involved in this embodiment has n cross-sectional shapes that are not completely identical. The parameterized variable sequence modeling method for this thickness-gradient layup structure is as follows:

[0141] Step 1. Extract n cross sections from the solid model of the thickness-gradient ply structure, where n is a natural number greater than 1, and perform steps 2 to 3 for each of the n cross sections.

[0142] Step 2. Based on the current cross-sectional dimensions and the single-layer thickness of the ply, generate a rectangular planar dot matrix, wherein the spacing between adjacent points in the planar dot matrix is ​​equal to the single-layer thickness of the ply; combining the initial distribution state of each ply section on the current cross-section, select points at corresponding positions from the planar dot matrix to serve as control points for each ply on the current cross-section, forming a control point matrix, and assigning a number to each control point; the outer contour of the control point matrix is ​​adapted to the shape of the current cross-section.

[0143] The specific implementation process of step 2 includes the following steps:

[0144] Step 2.1. Extract one cross section from the n cross sections. For the currently extracted cross section k, where k is a natural number from 1 to n, divide its height and thickness equally based on the given thickness x of a single layer. Generate a planar point matrix according to the position of cross section k in its Cartesian coordinate system. The planar point matrix contains... There are 10 points, of which 10 are points. The symbol is for rounding up; a is the maximum thickness of cross-section k; b is the minimum thickness of cross-section k; and h is the height of cross-section k.

[0145] After the cross-section k is superimposed on the planar lattice, it is covered by the planar lattice. The row direction of the planar lattice is parallel to the thickness direction of the cross-section k, and the column direction of the planar lattice is parallel to the height direction of the cross-section k. All points of this planar lattice are numbered a. ij , where i is the row of the point. j represents the column where the point is located. At this point, an initial numbering matrix can be obtained;

[0146] Step 2.2. From the planar point lattice, select suitable points as control points for each ply to form a control point lattice for cross-section k, including:

[0147] Step 2.2.1. Determine the control points of the outermost ply

[0148] For the left and right sides of cross section k, in the planar point lattice, firstly, determine the point closest to the left or right side of cross section k row by row as the candidate point for the outermost ply control point on the left or right side of the cross section. Then, among the remaining points, determine the point closest to the other side of cross section k row by row as the candidate point for the outermost ply control point on the other side of the cross section. Then, retain the points between the candidate points for the outermost ply control points on the left and right sides as the candidate points for the middle ply control point, and delete the points outside the candidate points for the outermost ply control points on the left and right sides.

[0149] Determine whether the distance deviation between each candidate control point and its corresponding side is within a preset range. If the distance deviation of a candidate point exceeds the preset range, then delete it from the candidate points.

[0150] Step 2.2.2. Determine the control points of the intermediate ply

[0151] Among the candidate points for intermediate ply control points, points in the same column are used as control points for the same ply. If there is only one remaining intermediate ply control point candidate point in the column, it is deleted.

[0152] Use the resulting dot matrix as the control dot matrix.

[0153] A sample example of step 2 can be found in step 2 of Example 1.

[0154] Step 3. Construct an initial control point numbering matrix. The initial control point numbering matrix consists of control point numbers and empty space symbols. The position of each control point number in the matrix corresponds to the position of the control point in the planar point matrix. The empty space symbols correspond to the points in the planar point matrix that have not been selected as control points and are filled in the matrix.

[0155] For example, for the cross section k, based on the planar point matrix obtained in step 2.1, an initial numbering matrix is ​​constructed. The numbering positions of the points deleted in step 2 are all set to 0, which are regarded as empty positions, and the initial control point numbering matrix A of the cross section k can be obtained. k (k takes the value 1-n);

[0156] In the cross section k, the position of each ply section is determined by its control point, and the position of each ply control point on the cross section k corresponds to the position of its number in the control point numbering matrix, thereby realizing the parameterization of the thickness gradient ply structure.

[0157] An example of step 3 can be found in step 3 of embodiment 1.

[0158] Step 4. Determine the ply correspondence between each cross section and its adjacent cross sections. The specific method is as follows:

[0159] The line connecting the control points of each ply on the cross section is regarded as the projection line of that ply on the cross section.

[0160] If the current cross section contains the same number of projection lines as its adjacent cross section, then it is determined that the projection lines of the current cross section and the adjacent cross section are in a one-to-one correspondence in the front-back direction.

[0161] If the number of projection lines contained in the current cross section is different from that in its adjacent cross section, let the current cross section contain two outermost plies and s middle plies, and the adjacent cross section contain two outermost plies and t middle plies, where s≠t. Then, first determine the correspondence between the projection lines of the outermost plies on the left and right sides of the current cross section and the adjacent cross section. For the remaining middle plies, take the value of o equal to the smaller value of s and t. Using the projection line of the outermost ply on one side as the reference, determine whether the projection lines of the o middle plies closest to the reference in the current cross section and its adjacent cross section are in a one-to-one correspondence in the front-back direction.

[0162] The projection lines in the front-to-back direction between the current cross section and its adjacent cross sections belong to the same ply.

[0163] like Figure 6As shown, suppose that, following the aforementioned method, cross section k contains 5 ply projection lines, corresponding to 5 plies, including 2 outermost plies and 3 intermediate plies, while cross section k+1 contains 4 ply projection lines, including 2 outermost plies and 2 intermediate plies. In this case, when determining the ply correspondence between adjacent cross sections, the projection line of the outermost ply on one side can be used as a reference. The two intermediate ply projection lines in cross sections k and k+1 closest to this reference are considered to be in a one-to-one correspondence in the front-to-back direction. When constructing the ply layer structure, the corresponding front-to-back projection lines can be considered as projection lines of the same ply and connected together. For example... Figure 6 As shown on the left side, with the lower boundary of the figure as the reference, from bottom to top, the 1st, 2nd, 3rd, and 5th projection lines of cross-section k correspond to the same ply as the 1st, 2nd, 3rd, and 4th projection lines of cross-section k+1, respectively. If the upper boundary of the figure is used as the reference, then from top to bottom, the 1st, 2nd, 3rd, and 5th projection lines of cross-section k correspond to the same ply as the 1st, 2nd, 3rd, and 4th projection lines of cross-section k+1, respectively. It should be noted that, generally, in the thickness-gradient ply structure, the reference boundary selected for all cross-sections should remain consistent.

[0164] Step 5. Based on the preset variable sequence scheme and the ply correspondence between cross sections, determine the cross section to be executed for the variable sequence, as well as the ply control points that need to be changed on the corresponding cross section. Then, based on the initial control point number matrix, perform parameterized variable sequence operation on the corresponding ply control points on the corresponding cross section.

[0165] The parameterized variable order operation includes the following steps:

[0166] Step 5.1. Suppose that according to the predetermined variable sequence scheme, the two intermediate plies that need to be swapped are ply M and ply N. Ply M and ply N are intermediate plies, and on the cross section k, the number of control points contained in ply N is greater than or equal to the number of control points contained in ply M.

[0167] In the initial control point numbering matrix A k In the middle, the positions of the control point numbers contained in ply M and ply N in the matrix are adjusted row by row to obtain the target control point number matrix B. k The adjusted rules are as follows:

[0168] 1) If a row contains both control point numbers for ply M and ply N, then directly swap the control point numbers of ply M and ply N in matrix A. k The position in the middle;

[0169] 2) If there is a control point number for ply N but no control point number for ply M in the row, then determine whether there are control point numbers for other intermediate ply between ply N and the control point number of the outermost ply closest to ply M.

[0170] If there are control point numbers for other intermediate plies, first move the control point number of ply N out of the row, then move the control point numbers of the other intermediate plies in the row one point towards ply N, and then fill the control point numbers of ply N in the row into the newly vacated positions in the row after the other intermediate plies have been moved.

[0171] If there are no other intermediate ply control point numbers, then the position of the control point number of ply N in the matrix remains unchanged;

[0172] Step 5.2. Based on the control point numbers corresponding to each ply, in the target control point numbering matrix B k In the position of the control point lattice on the cross section k, the control points of each ply are reconnected to obtain the projection line of the ply on the cross section k after the change of ply sequence.

[0173] An example of step 5 can be found in step 4 of embodiment 1.

[0174] Step 6. After changing the layer sequence, connect the projection lines of each cross section corresponding to the same ply by connecting control points one by one to generate the layer structure corresponding to each ply and obtain the target ply scheme.

[0175] For each cross-section, steps 2 to 3 are repeated cyclically to obtain n variable-sequence projection lines for each cross-section. Since the shapes of each cross-section are not exactly the same, the positions of the projection lines on each cross-section are not aligned front to back. Therefore, when connecting the projection lines of the same ply on different cross-sections, it is necessary to operate sequentially along the direction of extension of the thickness-gradient ply structure.

[0176] For two projection lines corresponding to the same ply on two adjacent cross sections, the layer structure corresponding to the ply can be reconstructed based on the control points contained in the two projection lines using a triangular facet construction method. Each control point is connected to at least two other adjacent control points, including one control point on the same cross section and one control point on an adjacent cross section. Figure 7 As shown, the projection line corresponding to the ply c on cross section k includes 5 control points, and the projection line corresponding to the ply c on cross section k+1 includes 4 control points. By connecting the control points on the two projection lines, the area between them is divided into multiple triangular facets. The layer structure of the ply between two adjacent cross sections is formed by splicing together the multiple triangular facets.

[0177] Then, following one direction, connect the projection lines of each cross-section with the corresponding ply on the next cross-section one by one to obtain the ply sequence scheme of the thickness-gradient ply structure in this embodiment.

[0178] The operating principles of Embodiment 2 and Embodiment 1 for each cross-section are basically the same. The difference lies in the operation method of generating the ply plot based on the projection lines when obtaining the ply plot of the solid model. In Embodiment 1, the projection lines of each ply are stretched in the direction of the thickness-gradient ply structure. The surface is extended based on the projection lines, which is equivalent to directly mapping the projection lines of each ply of the current cross-section onto the cross-sections at other locations. Then, the projection lines of each ply are connected to obtain the corresponding layer structure of each ply, but the processing efficiency is higher.

[0179] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that the directional terms such as "upper," "lower," "left," "right," "front," and "rear" used in the present invention are only for clarity of description and are not intended to limit the scope of implementation of the present invention. Those skilled in the art will understand that the directional terms may change depending on the viewing angle, and changes or adjustments to the relative positional relationships do not constitute substantial changes to the technical content. For those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A parametric variable-sequence modeling method for composite material thickness-gradient ply structures, used for thickness-gradient ply structures composed of multiple ply layers, with cross-sections extracted from different locations resulting in identical cross-sectional shapes, characterized in that... Includes the following steps: Step 1. Extract any cross section from the solid model of the thickness-gradient plywood structure; Step 2. Based on the current cross-sectional dimensions and the thickness of the single-layer ply, generate a rectangular planar lattice, wherein the spacing between adjacent points in the planar lattice is equal to the thickness of the single-layer ply; Based on the initial distribution of the cross-sections of each ply on the current cross-section, points at corresponding positions are selected from the planar point matrix to serve as control points for each ply on the current cross-section, forming a control point matrix, and each control point is assigned a number. The outer contour of the control point matrix is ​​adapted to the shape of the current cross-section. Step 3. Construct an initial control point numbering matrix. The initial control point numbering matrix consists of control point numbers and empty space symbols. The position of each control point number in the matrix corresponds to the position of the control point in the planar point matrix. The empty space symbols correspond to the points in the planar point matrix that have not been selected as control points and are filled in the matrix. Step 4. Based on the initial control point numbering matrix of the current cross section, perform parameterized change sequence operation on the control points of the corresponding ply on the current cross section; The parameterized change sequence operation is as follows: according to the change sequence scheme, adjust the position of the control point number of the corresponding ply in the initial control point number matrix to obtain the target control point number matrix. Then, according to the position of the control point number of each ply in the target control point number matrix, determine the new position of the control point of each ply in the control point matrix, and connect the new positions to obtain the projection line of each ply on the current cross section after the change sequence. Step 5. Following the direction of the thickness-gradient ply structure, stretch the projection lines of each ply after the change of ply sequence to generate the corresponding layer structure of each ply, and obtain the target ply scheme.

2. The parametric variable sequence modeling method for composite material thickness-gradient layup structures according to claim 1, characterized in that, Step 2 includes the following steps: Step 2.

1. For the extracted current cross-section k, generate a planar dot matrix, where the cross-section k is located within the area covered by the planar dot matrix; The planar lattice includes ( There are 10 points, of which 10 are points. The symbol is for rounding up; a is the maximum thickness of cross section k; h is the height of cross section k; x is the thickness of a single layer of the ply. The row direction of the planar point lattice is parallel to the thickness direction of the cross-section k, and the column direction of the planar point lattice is parallel to the height direction of the cross-section k. All points of the planar point lattice are numbered as follows: , The row containing the point, 1 , The column containing the point, 1 This yields an initial numbering matrix; Step 2.

2. Select suitable points from the planar point lattice as control points for each ply of cross section k, forming a control point lattice, including: Step 2.2.

1. Determine the control points of the outermost ply. For the left and right sides of cross section k, in the planar point lattice, the point closest to one side of the cross section is determined row by row as a candidate point for the outermost ply control point of the cross section on that side; among the remaining points, the point closest to the other side of cross section k is determined row by row as a candidate point for the outermost ply control point of the other side of the cross section. Then delete the points that are outside the outermost ply candidate points on the left and right sides, and use the points that are between the outermost ply candidate points on the left and right sides as candidate points for intermediate ply control points. Determine whether the distance deviation between each candidate point of the outermost ply and its corresponding side is within a preset range. If the distance deviation of the candidate point exceeds the preset range, then delete it. Step 2.2.

2. Determine the control points of the intermediate ply Among the candidate points for intermediate ply control points, points located in the same column are used as control points for the same intermediate ply. If there is only one remaining intermediate ply control point candidate point in the column, it is deleted. This gives us the control point lattice for the current cross-section k.

3. The parametric variable sequence modeling method for composite material thickness-gradient layup structures according to claim 2, characterized in that, Let the side with the maximum thickness a of the cross-section k be the bottom edge of the cross-section. In step 2.1, when generating the planar point matrix, the first or last point of the bottom row of the planar point matrix is ​​placed on the starting or ending point of the bottom edge, with the starting or ending position of the bottom edge as a reference.

4. The parametric variable sequence modeling method for composite material thickness-gradient layup structures according to claim 2, characterized in that, Step 3 includes the following steps: In the initial numbering matrix of the current cross section k, the numbers corresponding to the points deleted in step 2 are adjusted to empty symbols to obtain the initial control point numbering matrix.

5. The parametric variable sequence modeling method for composite material thickness-gradient layup structures according to claim 2, characterized in that, Step 4 includes the following steps: Step 4.

1. Let ply M and ply N be the two intermediate ply layers that need to be swapped according to the variable sequence scheme, and on the cross section k, the number of control points contained in ply N must be greater than or equal to the number of control points contained in ply M. In the initial control point numbering matrix, the control point numbers corresponding to ply M and ply N are adjusted row by row in the matrix. The adjusted control point numbering matrix will be used as the target control point numbering matrix, and the adjustment rules are as follows: 1) If the row contains both control point numbers for ply M and ply N, then directly swap the positions of the control point numbers for ply M and ply N in the initial control point number matrix; 2) If there is a control point number for ply N but no control point number for ply M in the row, then determine whether there are control point numbers for other intermediate ply between ply N and the control point number of the outermost ply closest to ply M. If there are control point numbers for other intermediate plies, first move the control point number of ply N out of the row, then move the control point numbers of the other intermediate plies in the row one point towards ply N, and then fill the new empty space created by the shifting of the control point numbers of the other intermediate plies in the row with the control point numbers of ply N. If there are no other intermediate ply control point numbers, then the position of the control point number of ply N remains unchanged; Step 4.

2. Based on the position of the control point number corresponding to each ply in the target control point number matrix, reconnect the control points of each ply in the control point matrix of cross section k to obtain the projection lines of each ply on the cross section k after the ply sequence is changed.

6. A parametric variable-sequence modeling method for composite material thickness-gradient ply structures, used for thickness-gradient ply structures composed of several ply layers, with cross-sections extracted from different locations resulting in cross-sectional shapes that are not entirely identical, characterized in that... Includes the following steps: Step 1. Extract n cross sections from the solid model of the thickness-gradient ply structure, where n is a natural number greater than 1. For the n cross sections, perform steps 2 to 3 respectively through a loop operation. Step 2. Based on the current cross-sectional dimensions and the thickness of the single-layer ply, generate a rectangular planar lattice, wherein the spacing between adjacent points in the planar lattice is equal to the thickness of the single-layer ply; Based on the initial distribution of the cross-sections of each ply on the current cross-section, points at corresponding positions are selected from the planar point matrix to serve as control points for each ply on the current cross-section, forming a control point matrix, and each control point is assigned a number. The outer contour of the control point matrix is ​​adapted to the shape of the current cross-section. Step 3. Construct an initial control point numbering matrix. The initial control point numbering matrix consists of control point numbers and empty space symbols. The position of each control point number in the matrix corresponds to the position of the control point in the planar point matrix. The empty space symbols correspond to points in the planar point matrix that have not been selected as control points. Step 4. Determine the ply correspondence between each cross section and its adjacent cross sections, including: The line connecting the control points of each ply on the cross section is regarded as the projection line of that ply on the cross section. If the current cross section contains the same number of projection lines as its adjacent cross section, then it is determined that the projection lines of the current cross section and the adjacent cross section are in a one-to-one correspondence in the front-back direction. If the number of projection lines contained in the current cross section is different from that in its adjacent cross section, let the current cross section contain two outermost plies and s middle plies, and the adjacent cross section contain two outermost plies and t middle plies, where s≠t. Then, first determine the correspondence between the projection lines of the outermost plies on the left and right sides of the current cross section and the adjacent cross section. For the remaining middle plies, take the value of o equal to the smaller value of s and t. Using the projection line of the outermost ply on one side as the reference, determine whether the projection lines of the o middle plies closest to the reference in the current cross section and its adjacent cross section are in a one-to-one correspondence in the front-back direction. The projection lines in the front-to-back direction between the current cross section and its adjacent cross section belong to the same ply. Step 5. Based on the preset variable sequence scheme and the ply correspondence between cross sections, determine the cross section to be executed for the variable sequence, as well as the ply control points that need to be changed on the corresponding cross section. Then, based on the initial control point number matrix, perform parameterized variable sequence operation on the corresponding ply control points on the corresponding cross section. The parameterized layer sequence change operation is as follows: adjust the position of the control point number of the corresponding ply in the initial control point number matrix of the current cross section to obtain the target control point number matrix. Then, based on the position of the control point number of each ply in the target control point number matrix, determine the new position of the control point of each ply in the control point matrix, and connect the new positions to obtain the projection line of each ply on the current cross section after the layer sequence change. Step 6. After changing the layer sequence, connect the projection lines of each cross section corresponding to the same ply by connecting control points one by one to generate the layer structure corresponding to each ply and obtain the target ply scheme.

7. A parametric variable sequence modeling method for composite material thickness-gradient layup structures according to claim 6, characterized in that, Step 2 includes the following steps: Step 2.

1. For the extracted current cross-section k, generate a planar dot matrix, where the cross-section k is located within the area covered by the planar dot matrix; The planar lattice includes ( There are 10 points, of which 10 are points. The symbol is for rounding up; a is the maximum thickness of cross section k; h is the height of cross section k; x is the thickness of a single layer of the ply. The row direction of the planar point lattice is parallel to the thickness direction of the cross-section k, and the column direction of the planar point lattice is parallel to the height direction of the cross-section k. All points of the planar point lattice are numbered as follows: , The row containing the point, 1 , The column containing the point, 1 This yields an initial numbering matrix; Step 2.

2. From the planar point lattice, select suitable points as control points for each ply of cross section k, forming a control point lattice, including: Step 2.2.

1. Determine the control points of the outermost ply. For the left and right sides of cross section k, in the planar point lattice, the point closest to one side of the cross section is determined row by row as a candidate point for the outermost ply control point of the cross section on that side; among the remaining points, the point closest to the other side of cross section k is determined row by row as a candidate point for the outermost ply control point of the other side of the cross section. Then delete the points that are outside the outermost ply candidate points on the left and right sides, and use the points that are between the outermost ply candidate points on the left and right sides as candidate points for intermediate ply control points. Determine whether the distance deviation between each candidate point of the outermost ply and its corresponding side is within a preset range. If the distance deviation of the candidate point exceeds the preset range, then delete it. Step 2.2.

2. Determine the control points of the intermediate ply Among the candidate points for intermediate ply control points, points located in the same column are used as control points for the same intermediate ply. If there is only one remaining intermediate ply control point candidate point in the column, it is deleted. This gives us the control point lattice for the current cross-section k.

8. The parametric variable sequence modeling method for composite material thickness-gradient layup structures according to claim 7, characterized in that, Let the side with the maximum thickness a of the cross-section k be the bottom edge of the cross-section. In step 2.1, when generating the planar point matrix, the first or last point of the bottom row of the planar point matrix is ​​placed on the starting or ending point of the bottom edge, with the starting or ending position of the bottom edge as a reference.

9. A parametric variable sequence modeling method for composite material thickness-gradient layup structures according to claim 6, characterized in that, Step 3 includes the following steps: In the initial numbering matrix of the current cross section k, the numbers corresponding to the points deleted in step 2 are adjusted to empty symbols to obtain the initial control point numbering matrix.

10. A parametric variable sequence modeling method for composite material thickness-gradient layup structures according to claim 6, characterized in that, In step 5, the parameterized variable order operation includes the following steps: Step 5.

1. Let the two intermediate plies that need to be swapped according to the variable sequence scheme be ply M and ply N, and the number of control points of ply N on the current cross section k is greater than or equal to that of ply M; In the initial control point numbering matrix of cross section k, the control point numbers corresponding to ply M and ply N are adjusted row by row in the matrix. The adjusted control point numbering matrix will be used as the target control point numbering matrix, and the adjustment rules are as follows: 1) If the row contains both control point numbers for ply M and ply N, then directly swap the positions of the control point numbers for ply M and ply N in the initial control point number matrix; 2) If there is a control point number for ply N but no control point number for ply M in the row, then determine whether there are control point numbers for other intermediate ply between ply N and the control point number of the outermost ply closest to ply M. If there are control point numbers for other intermediate plies, first move the control point number of ply N out of the row, then move the control point numbers of the other intermediate plies in the row one point towards ply N, and then fill the new empty space created by the shifting of the control point numbers of the other intermediate plies in the row with the control point numbers of ply N. If there are no other intermediate ply control point numbers, then the position of the control point number of ply N remains unchanged; Step 5.

2. Based on the position of the control point number corresponding to each ply in the target control point number matrix, reconnect the control points of each ply in the control point matrix of cross section k to obtain the projection lines of each ply on the current cross section k after the ply sequence is changed.

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