A method of modeling a fiber preform

Abstract

The application relates to a fiber preform modeling method, which comprises the following steps: marking the mass center and the contour point coordinates of each yarn cross section in a fiber preform CT image, tracking the position of each yarn cross section in the CT image, and matching the mass center and the contour point information; using a polynomial function to fit the mass center and the contour point coordinates of each yarn to make the yarn path smooth; and inhibiting the interference phenomenon between yarn entities, first inhibiting the interference between warp yarns or weft yarns, then inhibiting the interference between the warp yarns and the weft yarns, and finally generating a textile composite material model. The application is based on the CT image of the fiber preform to establish a model, has higher simulation accuracy, and the model has stronger adaptability, and the established model accuracy can be modified by itself; meanwhile, the overlapping interference problem in the model is inhibited through the contour point determination of the overlapping area between the fiber bundle cross sections and the offset processing of the contour points, and the interference for the subsequent model grid division is excluded.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, and more specifically to a method for modeling fiber preforms. Background Technology

[0002] Textile composites are frequently used in high-tech industries due to their high strength-to-weight ratio, superior mechanical properties, customizability, and versatility. By altering the weaving pattern and fabric structure of woven composites, a range of materials with varying mechanical properties can be obtained for different applications. However, the different microstructures of textile composites significantly impact their mechanical properties. Due to their complex structures, predicting their mechanical properties and service life is difficult in many applications. Therefore, modeling and simulating composite textile materials has become an effective method for studying their mechanical properties and damage evolution.

[0003] Traditional modeling methods primarily consider the spatial weaving structure of fiber bundles, using geometric shapes like ellipses or circles to represent the cross-sections of these bundles. However, this idealized model with regular cross-sections cannot accurately reflect the microscopic geometric stress-strain of composite materials under external loads. Furthermore, composite materials undergo geometric deformation under external loads, leading to interference defects within the material, a problem not addressed in existing modeling methods. In summary, these shortcomings in current modeling methods often result in significant discrepancies between simulated and experimental results. Summary of the Invention

[0004] This invention discloses a fiber preform modeling method, which establishes a model based on CT images of the fiber preform, can restore the true morphology of the fiber bundles in the fiber preform, and also solves the interference problem between fiber bundles, making the simulation accuracy of the model higher.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for modeling fiber preforms, comprising:

[0007] Step 1: Acquire CT images of the fiber preform and extract cross-sectional data of each fiber bundle from the CT images, and calculate the centroid coordinates and contour point coordinates of the cross-section of each fiber bundle;

[0008] Step 2: Match the cross-sectional information of the fiber bundles in the CT image to determine the fiber bundle entity to which the cross-section belongs, and make sure that the centroid coordinates and contour point coordinates of the matching cross-sections correspond one-to-one.

[0009] Step 3: Fit the centroid coordinates and contour point coordinates of the cross section along the fiber bundle axial direction using a polynomial function;

[0010] Step 4: Locate the overlapping sections between warp fiber bundles and between weft fiber bundles in the CT image, modify the coordinate data of the overlapping sections to avoid model overlap between warp entities and model overlap between weft entities.

[0011] Step 5: Locate the corresponding cross-sections in the CT image where the warp fiber bundle cross-sections overlap with the weft fiber bundle cross-sections, and modify the coordinate data of the overlapping cross-sections to avoid model overlap between the warp and weft entities;

[0012] Step 6: Generate a fiber preform model from the processed data.

[0013] Furthermore, in step 1, the centroid coordinates of the cross section in the CT image are calculated using the following formula:

[0014] M ji =∑ x，y (array(x, y)*x) j *y i ) (Formula 1)

[0015]

[0016]

[0017] In the above formula, M is the image moment, array(x, y) is the pixel value at (x, y) in the image, and C... x Let C be the x-coordinate of the centroid. y Let y be the centroid.

[0018] The coordinates of the contour points of the cross section in the CT image are determined as follows: the number of contour points is determined, the contour point located directly above the centroid coordinate of the cross section is taken as the first contour point, and the remaining contour points are evenly distributed on the cross section contour in a counterclockwise direction starting from the first contour point. The coordinates of the contour points are determined by fitting the fiber bundle cross section with a polygon.

[0019] Furthermore, in step 2, the affiliation between two sections is determined by calculating the change in centroid coordinates of the sections on two adjacent CT images.

[0020] Furthermore, when matching cross-sectional information, if a new cross-section cannot be matched, a matching cross-section is generated based on the average offset value of the centroids of the multiple successfully matched fiber bundles.

[0021] Furthermore, in step 4, the determination of overlapping sections is based on whether the polygonal regions enclosed by the section contour points intersect. If there is an intersection, it indicates that there is an overlapping section. After determining the overlapping section, the contour points that need to be offset are determined by traversing the contour points of the two overlapping sections to see if they are located within the contour region of the other section. The contour points that need to be offset are offset along the centroid direction of the fiber bundle section. The offset contour points are then combined with the remaining contour points in the original contour to form a new polygon until the final polygon no longer overlaps.

[0022] Furthermore, the offset of the contour points is calculated using the following formula:

[0023] a = C X -P x (Formula 4)

[0024] b = C y -P y (Formula 5)

[0025]

[0026] In the above formula, NP represents the coordinates of the offset contour points, and P... x P y These are the x and y coordinates of the contour points, respectively, and C. x C y These are the x and y coordinates of the centroid. This represents the percentage offset, meaning the distance the contour point is offset is equal to the current distance from the centroid. times.

[0027] Furthermore, in step 5, the determination of overlapping sections is based on whether the polygonal regions enclosed by the profile points of the sections intersect. If there is an intersection, it indicates that there is an overlapping section. After determining the overlapping warp fiber bundle sections and weft fiber bundle sections, the width, height, and thickness of each segment of the warp fiber bundle are calculated. The fiber bundle segments on the weft fiber bundle that overlap with the warp fiber bundle are found. The overlapping warp fiber bundle regions and weft fiber bundle regions are projected onto the front view and side view, respectively. It is determined whether the profile points of the two types of fiber bundle sections in the two views are located in the quadrilateral plane tangent to the other fiber bundle entity. The profile points that need to be offset are determined. The profile points that need to be offset are offset along the centroid direction of the fiber bundle section. The offset profile points are then combined with the remaining profile points in the original profile to form a new polygon until the final polygon no longer overlaps.

[0028] Furthermore, the extent of the tangent quadrilateral planar region is determined according to the following formula:

[0029]

[0030] Polygon[(y max ,x0),(y min ,x0),(y min ,x1),(y max ,x1)] (Formula 8)

[0031] In the above formula, x represents the x-coordinate of the left and right sides of the tangent quadrilateral plane, and y represents the y-coordinate of the top and bottom sides of the tangent quadrilateral plane. Let be the equation of the contour line segment of the tangent quadrilateral plane, and let Polygon be the region of the tangent quadrilateral plane.

[0032] Furthermore, the offset of the contour points is calculated using the following formula:

[0033] a = C X -P x (Formula 4)

[0034] b = C y -P y (Formula 5)

[0035]

[0036] In the above formula, NP represents the coordinates of the offset contour points, and P... x P y These are the x and y coordinates of the contour points, respectively, and C. x C y These are the x and y coordinates of the centroid. This represents the percentage offset, meaning the distance the contour point is offset is equal to the current distance from the centroid. times.

[0037] This invention establishes a model based on CT images of fiber preforms, which can restore the true shape of fiber bundles in the fiber preforms. Compared with traditional modeling that uses regular geometric shapes such as ellipses or circles to represent fiber bundle cross-sections, it has higher simulation accuracy and stronger model adaptability. The accuracy of the established model can be modified by the user. At the same time, this invention also fully considers the overlap problem between fiber bundle cross-sections during the modeling process. By determining the contour points of the overlapping area and by offsetting the contour points, the overlap interference problem in the model is suppressed, eliminating interference for subsequent model mesh generation. Attached Figure Description

[0038] Figure 1 This is a flowchart of the fiber preform modeling method of the present invention;

[0039] Figure 2 This is a schematic diagram illustrating the suppression of cross-sectional interference between fiber bundles of the same type during the modeling process.

[0040] Figure 3 This is a schematic diagram illustrating the suppression of cross-sectional interference between different types of fiber bundles during the modeling process.

[0041] Figure 4 Simulation diagram of the geometric model of the warp fiber bundle before interference suppression; (Top image is color, bottom image is black and white)

[0042] Figure 5 Simulation diagram of the geometric model of the warp fiber bundles to suppress interference; (Top image is color, bottom image is black and white)

[0043] Figure 6 Simulation diagram of the geometric model of the weft fiber bundle before interference suppression; (Top image is color, bottom image is black and white)

[0044] Figure 7 A simulation diagram of the geometric model of the weft fiber bundles after interference suppression. (The top image is in color, the bottom image is in black and white) Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0046] This embodiment discloses a method for modeling fiber preforms, such as... Figure 1 As shown, the method includes the following steps:

[0047] Step 1: Obtain CT images of the fiber preform and extract the cross-sectional data of each fiber bundle in the CT images. Calculate the centroid coordinates and contour point coordinates of the cross-section of each fiber bundle.

[0048] Specifically, the centroid coordinates of a cross section in a CT image are calculated using the following formula:

[0049] M ji =∑ x，y (array(x, y)*x) j *y i ) (Formula 1)

[0050]

[0051]

[0052] In the above formula, M is the image moment, array(x, y) is the pixel value at (x, y) in the image, and C... x Let C be the x-coordinate of the centroid. y Let y be the centroid.

[0053] The coordinates of the contour points in the cross section in the CT image are determined as follows: First, determine the number of contour points. The specific number of contour points is set as needed. Taking 30 contour points as an example, the contour point located directly above the centroid coordinate of the cross section is taken as the first contour point. The remaining contour points are evenly distributed on the cross section contour in a counterclockwise direction starting from the first contour point. The coordinates of each contour point are determined by fitting the fiber bundle cross section with a polygon.

[0054] Step 2: Match the cross-sectional information of the fiber bundles in the CT image to determine the fiber bundle entity to which the cross-section belongs, and make the centroid coordinates and contour point coordinates of the matching cross-sections correspond one-to-one.

[0055] Specifically, the affiliation of two sections is determined by calculating the change in centroid coordinates of the sections on two adjacent CT images. During the matching process, if a new section cannot be matched, a matching section is automatically generated based on the average offset value of the centroids of the fiber bundles from the previous successfully matched images (such as the first 5 images).

[0056] Step 3: Fit the centroid coordinates and contour point coordinates of the cross section to the fiber bundle axial direction using a polynomial function to make the surface of the subsequently generated fiber bundle solid model smooth.

[0057] Step 4: Locate the overlapping sections between warp fiber bundles and between weft fiber bundles in the CT image, modify the coordinate data of the overlapping sections, and avoid model overlap between warp entities and between weft entities.

[0058] Specifically, the determination of overlapping sections is based on whether the polygonal regions enclosed by the section contour points in each CT image after smoothing in step 3 intersect. If there is an intersection, it indicates that there is an overlapping section. After determining the overlapping section, the contour points that need to be offset are determined by traversing the contour points of the two overlapping sections to see if they are located within the contour region of the other section. Then, the contour points that need to be offset are offset along the centroid direction of their respective fiber bundle sections. The offset contour points are then combined with the remaining contour points in the original contour to form a new polygon until the final polygon no longer overlaps.

[0059] The offset of the contour points in this embodiment is determined by the following formula:

[0060] a = C X -P x (Formula 4)

[0061] b = C y -P y (Formula 5)

[0062]

[0063] In the above formula, NP represents the coordinates of the offset contour points, and P... x P y These are the x and y coordinates of the contour points, respectively, and C. x C y These are the x and y coordinates of the centroid. This represents the percentage offset, meaning the distance the contour point is offset is equal to the current distance from the centroid. times.

[0064] like Figure 2 The diagram shown illustrates the process of removing interference between fiber bundles of the same type. Here, "same type" refers to either warp fiber bundles or weft fiber bundles, and removing interference means separating overlapping areas from each other. Figure 2 Section 1 and Section 2 represent the two overlapping sections. Figure 2 The intersection area of ​​the two sections in Figure A is the overlapping area. Within the overlapping area, the contour point P in section 1 that needs to be offset is determined. 11 P 12 P 13 P 14 ,from Figure 2 As shown in Figure B below, the coordinates of the four contour points are already embedded in section 2. These four contour points are then offset towards the centroid C1 of section 1 according to Formula 6, where the offset percentage is... The value is 0.02; similarly, find the contour points P in section 2 that need to be offset. 21 P 22 P 23 Similarly, the offset is made in the direction of the centroid C2 of section 2 according to formula 6.

[0065] Step 5: Locate the corresponding cross-sections in the CT image where the warp fiber bundle cross-sections overlap with the weft fiber bundle cross-sections, and modify the coordinate data of the overlapping cross-sections to avoid model overlap between the warp and weft entities.

[0066] Specifically, in step 5, the judgment of overlapping cross-sections of different types of fiber bundles is the same as in step 4. Here, the different types refer to the overlap between warp fiber bundles and weft fiber bundles. After determining the overlapping warp and weft fiber bundle cross-sections, the width, height, and thickness of each segment of the warp fiber bundle are calculated. Using the geometric information mentioned above, the fiber bundle segments on each segment of the weft fiber bundle that overlap with the warp fiber bundle are found. The overlapping warp and weft fiber bundle regions are projected onto the front and side views, respectively. It is determined whether the contour points of the two types of fiber bundle cross-sections in the two views are located in the quadrilateral plane tangent to the other fiber bundle entity. The contour points that need to be offset are then determined. The contour points that need to be offset are offset along the centroid direction of the fiber bundle cross-section. The offset contour points are then combined with the remaining contour points in the original contour to form a new polygon until the final polygon no longer overlaps.

[0067] To be more specific, such as Figure 3 As shown, Figure 3 In the top left corner, in diagram A, fiber bundle 1 and fiber bundle 2 represent the warp and weft fiber bundles, respectively. The dark area in the diagram represents overlapping fiber bundle segments, which are displayed separately (e.g., Figure 3 (As shown in Figure B in the upper right corner). Projecting Figure B as a front view and a side view, it can be seen from the front view of Figure C that the coordinates of the contour point P1 in fiber bundle 1 are located within the quadrilateral plane tangent to the cross-section of fiber bundle 1 and the solid of fiber bundle 2. The coordinates of P1 are shifted along the centroid C1 direction according to Formula 6 until P1 leaves the quadrilateral plane tangent to the solid of fiber bundle 2. Similarly, from the side view of Figure D, it can be seen that the coordinates of the contour point P2 in fiber bundle 2 are located within the quadrilateral plane tangent to the cross-section of fiber bundle 2 and the solid of fiber bundle 1. The coordinates of P2 are shifted along the centroid C2 direction according to Formula 6 until P2 leaves the quadrilateral plane tangent to the solid of fiber bundle 1.

[0068] The extent of the aforementioned tangent quadrilateral planar region is determined using the following formula:

[0069]

[0070] Polygon[(y max ,x0),(y min ,x0),(y min ,x1),(y max ,x1)] (Formula 8)

[0071] In the above formula, x represents the x-coordinate of the left and right sides of the tangent quadrilateral plane, and y represents the y-coordinate of the top and bottom sides of the tangent quadrilateral plane. Let be the equation of the contour line segment of the tangent quadrilateral plane, and let Polygon be the region of the tangent quadrilateral plane.

[0072] Step 6: Generate an STL file from the processed data to establish a fiber preform model.

[0073] Figure 4 and Figure 6 The images show simulation diagrams of the warp fiber bundle geometry before and after interference removal, respectively. Figure 5 and Figure 7 The images shown are simulation diagrams of the corresponding geometric models of the warp and weft fiber bundles after interference removal according to the modeling method provided in this invention. These diagrams are intended to more clearly demonstrate the contrast between the changes before and after interference removal. Figures 4 to 7 The image provides both color and black-and-white comparison images. The top image is color, and the bottom image is black-and-white. The color image provides a more intuitive visual representation. Figures 4 to 7 The comparison results show that after interference is performed according to the method of the present invention, the overlap of fiber bundle entities is eliminated, thus removing interference for subsequent model mesh generation.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for modeling fiber preforms, characterized in that, include: Step 1: Acquire CT images of the fiber preform and extract cross-sectional data of each fiber bundle from the CT images, and calculate the centroid coordinates and contour point coordinates of the cross-section of each fiber bundle; Step 2: Match the cross-sectional information of the fiber bundles in the CT image to determine the fiber bundle entity to which the cross-section belongs, and make sure that the centroid coordinates and contour point coordinates of the matching cross-sections correspond one-to-one. Step 3: Fit the centroid coordinates and contour point coordinates of the cross section along the fiber bundle axial direction using a polynomial function; Step 4: Locate the overlapping sections between warp fiber bundles and between weft fiber bundles in the CT image, modify the coordinate data of the overlapping sections to avoid model overlap between warp entities and model overlap between weft entities. In step 4, the determination of overlapping sections is based on whether the polygonal regions enclosed by the section contour points intersect. If there is an intersection, it indicates that there is an overlapping section. After determining the overlapping section, the contour points that need to be shifted are determined by traversing the contour points of the two overlapping sections to see if they are located within the contour region of the other section. The contour points that need to be shifted are shifted along the centroid direction of the fiber bundle section. The shifted contour points are then combined with the remaining contour points in the original contour to form a new polygon until the final polygon no longer overlaps. The offset of the contour points is determined by the following formula: a = C x - P x (Official 4) (Official 5) (Official 6) In the above formula, NP These are the coordinates of the offset contour points. P x , P y These are the contour points. x , y coordinate, C x , C y These are the centroids. x , y coordinate, Percentage of offset; Step 5: Locate the corresponding cross-sections in the CT image where the warp fiber bundle cross-sections overlap with the weft fiber bundle cross-sections, and modify the coordinate data of the overlapping cross-sections to avoid model overlap between the warp and weft entities; In step 5, the determination of overlapping sections is based on whether the polygonal regions enclosed by the profile points of the sections intersect. If there is an intersection, it indicates that there is an overlapping section. After determining the overlapping warp fiber bundle sections and weft fiber bundle sections, the width, height, and thickness of each segment of the warp fiber bundle are calculated. The fiber bundle segments on the weft fiber bundle that overlap with the warp fiber bundle are found. The overlapping warp fiber bundle regions and weft fiber bundle regions are projected onto the front view and side view, respectively. It is determined whether the profile points of the two types of fiber bundle sections in the two views are located in the quadrilateral plane tangent to the other fiber bundle entity. The profile points that need to be offset are determined. The profile points that need to be offset are offset along the centroid direction of the fiber bundle section. The offset profile points are recombined with the remaining profile points in the original profile to form a new polygon until the final polygon no longer overlaps. The extent of the tangent quadrilateral planar region is determined by the following formula: (Official 7) (Official 8) In the above formula, x Let x be the x-coordinate of the left and right sides of the tangent quadrilateral plane, and y be the y-coordinate of the top and bottom sides of the tangent quadrilateral plane. l pipi+1 Let be the equation of the contour line segment of a tangent quadrilateral whose planes are tangent. Polygon The region is a tangent quadrilateral plane. Step 6: Generate a fiber preform model from the processed data.

2. The fiber preform modeling method according to claim 1, characterized in that: In step 1, the centroid coordinates of the cross section in the CT image are calculated using the following formula: (Official 1) (Official 2) (Official 3) In the above formula, M is the image moment, array( x , y ) is an image ( x , y The pixel value at () The coordinates of the contour points of the cross section in the CT image are determined as follows: the number of contour points is determined, the contour point located directly above the centroid coordinate of the cross section is taken as the first contour point, and the remaining contour points are evenly distributed on the cross section contour in a counterclockwise direction starting from the first contour point. The coordinates of the contour points are determined by fitting the fiber bundle cross section with a polygon.

3. The fiber preform modeling method according to claim 1, characterized in that: In step 2, the affiliation between two sections is determined by calculating the change in centroid coordinates of the sections on two adjacent CT images.

4. The fiber preform modeling method according to claim 3, characterized in that: When matching cross-sectional information, if a new cross-section cannot be matched, a cross-section that matches it is generated based on the average offset value of the centroids of the multiple fiber bundles that have been successfully matched.

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