Method for predicting mechanical property of woven composite material structure

Abstract

The invention relates to a mechanical property prediction method for a woven composite material structure, and the method comprises the steps: obtaining a microscopic CT image of the woven composite material structure; carrying out image preprocessing on the CT image; segmenting a fiber bundle in the preprocessed image to obtain a segmented fiber bundle image; extracting a fiber bundle trend center line from the segmented fiber bundle image; establishing a macroscopic geometric model of the woven composite material structure, and performing unit grid division on the geometric model; establishing a relation between a fiber bundle trend center line and a geometric model unit; calculating mechanical property parameters of each unit one by one; and calculating the macromechanical response of the composite material structure. According to the method for predicting the mechanical property of the woven composite material structure, the grid division independent of the microstructure characteristics is adopted, so that the modeling efficiency can be improved, the modeling difficulty can be reduced, and the method is easy to implement.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material structure mechanical property prediction methods, and in particular relates to a woven composite material mechanical property prediction method. Background Art

[0002] In the field of engineering, understanding the mechanical properties of materials is of great significance to the design and application of materials. Woven composites are a type of composite material composed of fibers and a matrix, in which the fibers are interwoven in a woven manner and then cured by a matrix material. Woven composites have the advantages of high strength, high stiffness, low specific gravity, and corrosion resistance, and are widely used in aerospace, automobiles, ships, construction, sporting goods and other fields. Accurate prediction of the mechanical properties of woven composites is crucial for material performance evaluation and structural design. Woven composites are typical anisotropic materials, and the microstructure of woven composites is complex. The presence of irregular and irregular pores and the interlacing, extrusion and interference between fiber bundles will affect the mechanical properties of woven composites. Accurate prediction of the performance of woven composites is complex and difficult.

[0003] The existing mechanical property prediction methods of woven composite materials are generally based on the equivalent average method, and the overall mechanical properties of the material are obtained by studying the mechanical properties of the representative volume element (RVE). However, the above methods generally obtain the mechanical properties of woven composite materials based on the periodicity of the microstructure of woven composite materials. In fact, woven composite materials have complex microstructures, and differences are easily generated during the molding process of woven composite materials, resulting in significant non-uniformity in woven composite materials. These non-uniformities are difficult to accurately consider in the mechanical property prediction method based on RVE, and bring many difficulties to the establishment of the model, resulting in errors in the prediction of the mechanical properties of woven composite materials. Summary of the invention

[0004] The purpose of the present invention is to provide a method for predicting the mechanical properties of a woven composite material based on the center line of a fiber bundle orientation, which improves the modeling efficiency and reduces the difficulty of modeling.

[0005] The technical solution proposed by the present invention is a method for predicting the mechanical properties of woven composite materials, comprising:

[0006] Step 101, obtaining a CT image of the woven composite material;

[0007] Step 102, performing image preprocessing on the CT image;

[0008] Step 103, segmenting the fiber bundles in the preprocessed image to obtain a segmented fiber bundle image;

[0009] Step 104, extracting the fiber bundle direction center line from the segmented fiber bundle image;

[0010] Step 105, establishing a macroscopic geometric model of the woven composite material structure, and performing unit mesh division on the geometric model;

[0011] Step 106, establishing a connection between the fiber bundle centerline and the geometric model unit;

[0012] Step 107, calculating the mechanical performance parameters of each unit one by one;

[0013] Step 108, calculating the macroscopic mechanical response of the composite material structure.

[0014] Furthermore, step 101, obtaining a CT image of the woven composite material, further includes: the resolution of the CT image is at least sub-millimeter level.

[0015] Furthermore, step 102, performing image preprocessing on the CT image, also includes: the image preprocessing method includes a noise removal algorithm and a contrast enhancement algorithm.

[0016] Furthermore, step 103, segmenting the fiber bundles in the preprocessed image to obtain a segmented fiber bundle image, also includes: segmenting the fiber bundles may apply one or more segmentation methods such as threshold segmentation, region growing, edge detection, and a deep learning-based segmentation method.

[0017] Furthermore, step 104, extracting the center line of the fiber bundle from the segmented fiber bundle image, also includes: extracting the center line of the fiber bundle may apply one or more algorithms such as a skeleton extraction algorithm, a thinning algorithm, a distance transformation algorithm, and a medial axis transformation algorithm.

[0018] Furthermore, step 106, establishing a connection between the center line of the fiber bundle and the geometric model unit, also includes: setting a range for calculating the distance; establishing the center line of the fiber bundle contained in the range of the center point of the geometric model unit; and calculating the distance from the center point of the geometric model unit to the center line of the fiber bundle contained in the range.

[0019] Further, in step 107, the mechanical performance parameters of each unit are calculated one by one. The mechanical properties of composite materials generally include the stiffness, strength, toughness, thermal expansion and other properties of the material. Taking the stiffness performance of the material as an example, the calculation idea of ​​this patent is introduced, and the calculation formula is:

[0020]

[0021] [C m ] is the stiffness matrix of the geometric model unit of the woven composite material;

[0022] i=1-n represents the centerline of the fiber bundle within the center point of the geometric model unit;

[0023] f i It represents the weighting factor of the fiber bundle centerline. Its value depends on the distance from the fiber bundle centerline to the center point of the geometric model unit. It is used to determine the influence of each fiber bundle centerline on the mechanical properties of the geometric model unit.

[0024] [C i ] is the stiffness matrix of the fiber bundle of the woven composite material in its own local coordinate system;

[0025] [T i ] is the coordinate transformation matrix, which is used to transform the stiffness matrix of the fiber bundle from the local coordinate system to the global coordinate system;

[0026] [T i ] -1 is the inverse matrix of the coordinate transformation matrix, which is used to transform the stiffness matrix of the fiber bundle from the local coordinate system to the global coordinate system.

[0027] Other mechanical properties parameters can refer to the stiffness parameter calculation method, such as the thermal expansion coefficient of the material:

[0028]

[0029] α m is the thermal expansion coefficient of the geometric model unit of the woven composite material;

[0030] i=1-n represents the centerline of the fiber bundle within the center point of the geometric model unit;

[0031] f i It represents the weighting factor of the centerline of the fiber bundle. Its value depends on the distance from the centerline of the fiber bundle to the center point of the geometric model unit. It is used to determine the influence of the centerline of each fiber bundle on the mechanical properties of the geometric model unit. It should be noted that the weighting coefficients of different mechanical property parameters are not the same.

[0032] α f is the coefficient of thermal expansion of the fiber bundle of the woven composite material, usually determined by experiment;

[0033] Furthermore, in step 108, the macroscopic mechanical response of the composite material structure is calculated. The macroscopic mechanical response includes the stress-strain field and the overall deformation of the composite material structure, which can be directly calculated by the finite element method based on the unit mechanical performance parameters obtained in step 107.

[0034] The beneficial effects of the present invention are as follows: by establishing a connection between the geometric model unit of the woven composite material and the center line of the fiber bundle, the mechanical properties of the woven composite material are calculated, and a regular grid division independent of the microscopic structural characteristics is adopted, thereby improving the modeling efficiency of the mechanical analysis of the woven composite material structure, reducing the difficulty of modeling, facilitating the preform process design during the initial configuration design of the woven composite material structure, and the method is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 CT images of woven composite specimens;

[0036] Figure 2 is the CT image of the initial woven composite specimen;

[0037] Figure 3 This is the CT image of the woven composite specimen after pretreatment;

[0038] Figure 4 is the fiber bundle image after segmentation;

[0039] Figure 5 This is a schematic diagram of the centerline of the fiber bundle of the woven composite material specimen;

[0040] Figure 6 It is the unit mesh diagram of the geometric model of the woven composite material specimen;

[0041] Figure 7 It is a schematic diagram of the projection distance from the center point of the geometric model unit to the center line of the fiber bundle;

[0042] Figure 8 This is a flow chart of the mechanical properties prediction method. DETAILED DESCRIPTION

[0043] The drawings are only used for illustrative purposes and should not be construed as limitations on this patent. In order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged, or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0044] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. It can be said that the internal connection of two components is connected. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The technical solution of the present invention is further explained below in conjunction with the accompanying drawings and embodiments.

[0045] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. Figure 8 As shown, the present invention provides a method for predicting mechanical properties of a woven composite material structure, the method comprising the following steps:

[0046] Step 101, obtaining a CT image of a woven composite material structure;

[0047] Step 102, performing image preprocessing on the CT image;

[0048] Step 103, segmenting the fiber bundles in the preprocessed image to obtain a segmented fiber bundle image;

[0049] Step 104, extracting the fiber bundle direction center line from the segmented fiber bundle image;

[0050] Step 105, establishing a geometric model of the woven composite material, and performing unit mesh division on the geometric model;

[0051] Step 106, establishing a connection between the fiber bundle centerline and the geometric model unit;

[0052] Step 107, calculating the mechanical performance parameters of each unit one by one;

[0053] Step 108, calculating the macroscopic mechanical response of the composite material structure.

[0054] In this embodiment, a woven composite material specimen is selected as a research object, and a CT scan is performed on the woven composite material specimen to obtain a high-resolution CT image, such as Figure 1 shown.

[0055] The CT image resolution of the woven composite material structure in step 101 needs to reach at least the sub-millimeter level to clearly display the microscopic features such as the fiber arrangement of the woven composite material for analysis. At the same time, the most appropriate resolution level needs to be determined according to the specific application. The initial CT image of the woven composite material specimen is as follows: Figure 2 As shown, the woven composite material structure in this embodiment is a long strip test piece of a woven ceramic-based composite material.

[0056] Step 102: perform image preprocessing on the CT image.

[0057] In this embodiment, the CT image obtained in step 101 is preprocessed using Avizo software. The image preprocessing method includes removing noise by adjusting parameters such as the size of Gaussian filtering and median filtering, wherein the Gaussian kernel size and the neighborhood size are usually selected between 3x3 and 7x7. The method of enhancing contrast includes methods such as histogram equalization and contrast stretching. According to the noise level and contrast change degree of the image after image preprocessing, step-by-step attempts and evaluations are made to achieve the effect that the fiber bundles are clearly visible, the fiber bundles are clearly distinguished from the background, and the details and shapes of the fiber bundles are retained. The preprocessed image is as follows Figure 3 shown.

[0058] Step 103, segmenting the fiber bundles in the preprocessed image to obtain a segmented fiber bundle image.

[0059] In this embodiment, the image processed in step 102 is imported into the Avizo software, and the image is converted into a binary image using the threshold segmentation technology. Based on the difference between the grayscale characteristics of the fiber bundle and the background grayscale, the automatic threshold segmentation technology such as Otsu and Triangle of the Avizo software is used to automatically select an appropriate threshold according to the statistical characteristics of the image, and then the effect of the binary image is observed by visually adjusting the threshold. Multiple tests and adjustments are performed to achieve the best segmentation effect. Pixels above the threshold are marked as fiber bundles, and pixels below the threshold are marked as background, so that the fiber bundles are separated from the image to ensure that the fiber bundles are separated from other materials as accurately as possible. The segmented fiber bundle image is as shown in FIG. Figure 4 shown.

[0060] In step 103, the segmentation algorithm in the three-dimensional data visualization and analysis software Avizo is used to separate the fiber bundles from the image, which is only a common method. According to the actual situation, the fiber bundles can be separated from the image by using segmentation methods including but not limited to threshold segmentation, region growing, edge detection and deep learning-based segmentation methods.

[0061] Step 104, extract the fiber bundle centerline from the segmented fiber bundle image, such as Figure 5 shown.

[0062] The fiber bundle direction center line includes the warp yarn direction center line X1 and the weft yarn direction center line Y1. In this embodiment, the "skeletonization" tool provided by the Avizo software is used to perform "Thinning Algorithm" processing on the image data obtained in step 103. Select appropriate parameter settings, including parameters such as the number of iterations, threshold, and domain size. Regarding the setting of the number of iterations parameter, the number of iterations is set within a range of 10 to 100, and the changes in the extraction results are observed and the most appropriate number of iterations is selected. Regarding the setting of the threshold parameter, the threshold parameter is based on the threshold obtained in step 103, and then continuously debugged according to the changes in the brightness and contrast of the image to obtain a suitable threshold. Regarding the setting of the neighborhood size parameter, the neighborhood size is set within a range of 1 to 10 pixels, and the changes in the extraction results are observed to select a suitable neighborhood size. Through the iterative process, the boundary of the fiber bundle is gradually "eroded", and finally the fiber bundle direction center line information is obtained, and the extraction results are optimized and adjusted, including removing possible noise and interference to obtain more accurate fiber bundle direction center line information.

[0063] The fiber bundle centerline information in step 104 refers to the extracted center axis information of the fiber bundle in the form of a series of spatial coordinate values ​​of points. Through these spatial coordinate values, various geometric parameters of the fiber bundle can be obtained, including length, radius of curvature, and curvature.

[0064] In step 104, using the "skeletonization" tool in the three-dimensional data visualization and analysis software Avizo to obtain the centerline information of the fiber bundle of the woven composite material specimen is only a common method. According to the actual situation, one or more algorithms including but not limited to "Thinning Algorithm", "Distance Transform Algorithm" and "Medial Axis Transform Algorithm" can be used to extract the centerline information of the fiber bundle of the woven composite material. At the same time, this embodiment can also be used to predict the mechanical properties of self-designed woven composite materials.

[0065] Step 105, establishing a geometric model of the woven composite material, and performing unit mesh division on the geometric model; Figure 6 shown.

[0066] Using ABAQUS finite element analysis software, according to the macroscopic geometric characteristics of the woven composite specimens, the corresponding geometric model was established, and the appropriate grid density was selected for unit grid division.

[0067] In this embodiment, the size of the geometric model is 39*4.5*9.5, the unit grid shape of the geometric model is a hexahedral structure grid, the approximate global size is 1, and the unit is mm.

[0068] Mesh division is performed. For example, if the woven composite material specimen is a rectangular specimen, a rectangular geometric model with corresponding dimensions is established, and then the rectangular geometric model is imported into the ABAQUS finite element analysis software for mesh division, and the geometric model unit is m1.

[0069] Step 106, establishing a connection between the fiber bundle centerline and the geometric model unit.

[0070] The connection in step 106 refers to determining the fiber bundle center lines contained in the distance range of each geometric model unit, and determining the distances from the center points of the geometric model units to the fiber bundle center lines.

[0071] In this embodiment, based on the fiber bundle centerline information obtained in step 104 and the geometric model of the woven composite material specimen established in step 105, Visual Studio programming software is used to establish the connection between the geometric model unit of the woven composite material specimen and the fiber bundle centerline of the woven composite material specimen. Specifically, the parameter information of the geometric model unit is the coordinate of the unit center point, and a suitable distance range is selected, such as Figure 7 As shown in the middle circle, the size of the distance range is between half the fiber bundle width and one fiber bundle width. According to the distance range, the center line of the fiber bundle direction contained in the center point of the geometric model unit within the range is determined, and the distance from the center point of the geometric model unit to the center line of all fiber bundles contained in the range is calculated. The calculation method can adopt the mapping method.

[0072] Establish the distance from the coordinates of the center point of the geometric model unit to the center line of all fiber bundles contained in the range. The method for calculating the distance is as follows:

[0073] Calculate the distance from the center point coordinates of the geometric model unit to the projection coordinates, and set the distance as the distance from the center point of the geometric model unit to the center line of the fiber bundle. The schematic diagram of the distance calculation method is as follows: Figure 7 The fiber bundle centerline information here refers to the distance from the center point of the geometric model unit to the fiber bundle centerline, as well as the starting point coordinates and end point coordinates of the fiber bundle centerline within the geometric model unit.

[0074] Step 107, calculating the mechanical performance parameters of each unit one by one.

[0075] The mechanical properties of materials refer to the properties exhibited by materials when subjected to stress and deformation. Common mechanical properties of materials include stiffness, strength, toughness, thermal expansion and other properties. Among them, the stiffness performance of materials is mainly represented by the stiffness matrix of the material. The stiffness matrix of a material is a tensor that describes the stiffness characteristics of a material under small strains. It reflects the rigidity characteristics of a material or structure, that is, the degree of deformation under external forces. The mechanical properties of materials are indicators for evaluating the mechanical behavior and properties of materials under stress, which can be calculated and evaluated through the stiffness matrix of the material. Based on the geometric model unit of the woven composite specimen in step 106 and the centerline information of the fiber bundle orientation associated with it, the formula is used. The stiffness matrix of each geometric model unit of the woven composite specimen can be calculated to obtain the overall stiffness performance of the geometric model of the woven composite specimen. Common material mechanical properties include stiffness, strength, toughness, thermal expansion and other properties of the material. This embodiment takes the stiffness performance of the material as an example to introduce a method for predicting the mechanical properties of a woven composite material, so as to achieve the purpose of predicting the mechanical properties of a woven composite material.

[0076] [C m ] is the stiffness matrix of the geometric model unit of the woven composite material;

[0077] i=1-n represents the centerline of the fiber bundle within the center point of the geometric model unit;

[0078] f i It represents the weighting factor of the fiber bundle centerline. Its value depends on the distance from the fiber bundle centerline to the center point of the geometric model unit. It is used to determine the influence of each fiber bundle centerline on the mechanical properties of the geometric model unit.

[0079] [C i ] is the stiffness matrix of the fiber bundle of the woven composite material in its own local coordinate system, which is generally determined by experiments;

[0080] The stiffness matrix of the fiber bundle needs to be obtained through experiments. Mechanical tests are performed on the fiber bundle to obtain the stress-strain relationship of the fiber bundle, thereby obtaining the stiffness parameters of the fiber bundle, such as the elastic modulus, shear modulus and Poisson's ratio. Through multiple tests, the average value of the stiffness parameters of the fiber bundle is obtained as a representative parameter. Based on these stiffness parameters, the stiffness matrix of the fiber bundle can be calculated. Here, a simplified treatment is made, and the stiffness matrix of each fiber bundle is regarded as the same, which is convenient for the subsequent calculation of the stiffness matrix of the geometric model unit.

[0081] [T i ] is the coordinate transformation matrix, which is used to transform the stiffness matrix of the fiber bundle from the local coordinate system to the global coordinate system;

[0082] The specific calculation steps of the coordinate transformation matrix are:

[0083] 1. Determine the local coordinate system of the fiber bundle: usually the main axis direction of the fiber bundle is taken as the x-axis of the local coordinate system, and the normal direction of the fiber bundle cross section is taken as the z-axis of the local coordinate system;

[0084] 2. Determine the position and direction of the fiber bundle in the global coordinate system: determine the starting point coordinates and the end point coordinates of the fiber bundle in the global coordinate system, and calculate the direction vector of the fiber bundle by subtracting the starting point coordinates from the end point coordinates of the fiber bundle;

[0085] 3. Calculate the rotation angle and coordinate transformation matrix of the fiber bundle: Calculate the rotation angle and coordinate transformation matrix of the fiber bundle according to the direction vector of the fiber bundle. The coordinate transformation matrix is ​​a 6×6 matrix that represents the rotation relationship of the local coordinate system of the fiber bundle relative to the global coordinate system.

[0086] [T i ] -1 is the inverse matrix of the coordinate transformation matrix, which is used to transform the stiffness matrix of the fiber bundle from the local coordinate system to the global coordinate system.

[0087] Step 108, calculating the macroscopic mechanical response of the composite material structure.

[0088] The macroscopic mechanical response includes the stress-strain field and the overall deformation of the composite material structure, which can be directly calculated using the general finite element method based on the unit mechanical property parameters obtained in step 107.

[0089] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for predicting mechanical properties of a woven composite material structure, characterized in that: Step 101, obtaining a CT image of the woven composite material; Step 102, performing image preprocessing on the CT image; Step 103, segmenting the fiber bundles in the preprocessed image to obtain a segmented fiber bundle image; Step 104, extracting the fiber bundle direction center line from the segmented fiber bundle image; Step 105, establishing a macroscopic geometric model of the woven composite material structure, and performing regular unit grid division on the geometric model; Step 106, establishing a connection between the fiber bundle centerline and the geometric model unit; Step 107, calculating the mechanical performance parameters of each unit one by one; Step 108, calculating the macroscopic mechanical response of the composite material structure.

2. The mechanical property prediction method according to claim 1, characterized in that: Step 101, obtaining a CT image of a woven composite material specimen, further includes: The resolution of CT images is at least sub-millimeter.

3. The mechanical property prediction method according to claim 2, characterized in that: Step 102, performing image preprocessing on the CT image, further includes: Image preprocessing methods include noise removal algorithms and contrast enhancement algorithms.

4. The mechanical property prediction method according to claim 3, characterized in that: Step 103, segmenting the fiber bundles in the preprocessed image to obtain a segmented fiber bundle image, further comprising: The fiber bundles can be segmented by applying one or more segmentation methods such as threshold segmentation, region growing, edge detection and deep learning-based segmentation methods.

5. The mechanical property prediction method according to claim 4, characterized in that: Step 104, extracting the fiber bundle direction center line from the segmented fiber bundle image, also includes: To extract the center line of the fiber bundle, one or more algorithms such as skeleton extraction algorithm, thinning algorithm, distance transformation algorithm, medial axis transformation algorithm, etc. can be applied.

6. The mechanical property prediction method according to claim 5, characterized in that: Step 104, extracting the fiber bundle direction center line from the segmented fiber bundle image, also includes: The fiber bundle running center line includes the warp yarn running center line and the weft yarn running center line.

7. The mechanical property prediction method according to claim 6, characterized in that: Step 106, establishing a connection between the fiber bundle centerline and the geometric model unit, also includes: Set the range for calculating distance; Establish the center line of the fiber bundle within the center point of the geometric model unit; Calculate the distance from the center point of the geometric model unit to the center line of the fiber bundle contained in the range.

8. The mechanical property prediction method according to claim 7, characterized in that: Step 107, calculating the mechanical properties of the geometric model unit, also includes: ； [C m ] is the stiffness matrix of the geometric model unit of the woven composite material; i=1-n represents the centerline of the fiber bundle within the center point of the geometric model unit; f i represents the weighting factor of the fiber bundle toward the center line; [C i ] is the stiffness matrix of the fiber bundle of the woven composite material in its own local coordinate system; [T i ] is the coordinate transformation matrix, which is used to transform the stiffness matrix of the fiber bundle from the local coordinate system to the global coordinate system; [T i ] -1 is the inverse matrix of the coordinate transformation matrix, which is used to transform the stiffness matrix of the fiber bundle from the local coordinate system to the global coordinate system.

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