A 2.5d woven composite unit cell parameterized geometry modeling method
By parametrically describing the unit cell geometry and yarn path, the problem of difficulty in simultaneously considering the real spatial undulations and cross-sectional changes of yarn in existing modeling methods is solved, achieving efficient geometric modeling of 2.5D woven composite materials and improving the accuracy and applicability of the model.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HARBIN INST OF TECH
- Filing Date
- 2026-02-10
- Publication Date
- 2026-06-12
AI Technical Summary
Existing geometric modeling methods for 2.5D woven composite materials struggle to simultaneously account for the real spatial undulations of the yarn, cross-sectional geometric changes, and parameter controllability, resulting in significant deviations between the model and the actual structure, which affects the accuracy of mechanical performance prediction.
A 2.5D parametric geometric modeling method for unit cells of woven composite materials is adopted. By parametrically describing the geometric domain, yarn cross-section and center path of the unit cell, a collaborative model of yarn path and cross-section is constructed to reflect the real structural characteristics, including the interlacing undulation of warp and weft yarns and the influence of the forming process.
It achieves precise capture of the interlacing and undulating shape of yarn and the influence of the forming process under the premise of controllable parameters, reduces the deviation between the model and the actual structure, and improves the engineering applicability and structural reproducibility of the geometric model.
Smart Images
Figure CN122201533A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a geometric modeling method for composite materials, specifically a parametric geometric modeling method for 2.5D woven composite material unit cells that considers real structural features, belonging to the field of composite material structure modeling and engineering calculation technology. Background Technology
[0002] The internal yarn structure of 2.5D woven composite materials is highly complex. Structural features such as warp and weft density, warp and weft yarn specifications, and preform weaving methods all influence its mechanical properties. Although the preform structure exhibits certain regularity, the compaction of the mold and the interaction between the interlaced yarns during the molding process result in varying degrees of bending fluctuations, cross-sectional torsion, and structural misalignment in the warp and weft yarns. These structural features affect the mechanical properties of woven composite materials, especially strength and fatigue properties, which are sensitive to local characteristics. Therefore, revealing the mechanism by which the geometry of woven composite materials influences their mechanical properties is crucial for guiding material design and structural optimization of woven composite materials.
[0003] Generally, mechanical testing is the most direct and effective way to evaluate the mechanical properties of 2.5D woven composites. However, due to high manufacturing costs, long testing cycles, and complex weaving methods, it is impractical to study the influence of the geometry of woven composites on their mechanical properties solely through experiments. To address this, researchers have developed microscale models based on Reproducible Element Methods (RVEs) to study the complex mechanical properties of woven composites. Clearly, accurately reproducing microstructural features is crucial for the finite element analysis of woven composites, and this goal relies on constructing highly accurate microscale unit cell models, especially for predicting strength and fatigue properties. Therefore, establishing high-fidelity RVEs that approximate the true structure of the material is increasingly attracting researchers' attention. Currently, modeling methods for the microstructure of woven composites can be mainly divided into three categories: image reconstruction methods, compaction simulation reconstruction methods, and parametric modeling methods. However, image reconstruction methods heavily rely on the resolution of CT images, which can lead to high modeling costs and is not conducive to use in the design phase. Furthermore, deep learning technology is often applied only to one structure and may require more data to further enhance its generalization ability, which will further increase costs. Compaction simulation reconstruction, reverse geometry generation, or the development of complex mesh generation algorithms all aim to obtain a consistent mesh for finite element analysis. However, these studies typically require highly complex computational simulations or extensive geometry reconstruction, resulting in high time costs and hindering their use in the design phase. Existing parametric modeling methods often lack uniformity, favoring specific structures, and many adjustable parameters lack intuitive physical meaning. A few unified parametric modeling methods can currently only generate standard prefabricated geometry, failing to consider yarn deformation after molding, which may be one reason for the large stiffness prediction errors in existing models.
[0004] Therefore, it is necessary to establish a parametric geometric modeling method for 2.5D woven composite material unit cells that considers the real structural characteristics, and to reveal the influence of the structural characteristics of woven composite materials on their mechanical properties. Summary of the Invention
[0005] To address the problem that existing geometric modeling methods for woven composite materials struggle to simultaneously consider the real spatial undulations of yarns, cross-sectional geometric changes, and parameter controllability, this invention proposes a 2.5D parametric geometric modeling method for unit cells of woven composite materials. This method effectively describes the real structural characteristics of woven composite materials, providing a reliable geometric model foundation for subsequent numerical analysis and engineering applications.
[0006] The technical solution adopted by the present invention to solve the above problems is as follows:
[0007] A parametric geometric modeling method for a 2.5D woven composite material unit cell, wherein the 2.5D woven composite material unit cell yarn structure includes warp and weft yarns, comprising the following steps: S1: Determination of unit cell geometry: Based on the structural parameters of 2.5D woven composite materials, the geometric range of the unit cell in space is determined. S2: Parameterized definition of yarn cross-section. Based on the geometric features of the yarn cross-section, the cross-sectional shape and size of the warp and weft yarns are parameterized to obtain the initial yarn cross-section parameters. S3: Yarn center path construction. First, based on the topological relationship of the woven structure and the geometric dimensions of the yarn cross-section obtained in S2, the basic yarn center path is determined. Then, the influence of the forming process on the warp and weft yarn center paths is analyzed, and key feature parameters characterizing this influence are extracted. Finally, the basic yarn center path is corrected using the key feature parameters to obtain the spatial center paths of the warp and weft yarns within the unit cell, and the yarn center path coordinates are obtained. Through the yarn center path construction, all center path parameters are obtained. S4: Path and cross-section parameter coupling modeling, the initial yarn cross-section parameters obtained in S2 are coupled with the center path parameters obtained in S3 to determine the variation law of the cross-section along its center path, obtain the cross-section coordinates after the cross-section changes along the path, and construct the yarn entity geometry; S5: Unit cell geometry model generation. Based on the unit cell geometry domain obtained in S1, the yarn center path coordinates obtained in S3, and the cross-sectional coordinates after the cross-section changes along the path obtained in S4, a complete 2.5D woven composite material unit cell geometry model is generated and output.
[0008] Furthermore, the structural parameters mentioned in S1 include the arrangement characteristics of warp and weft yarns in the fabric, and the dimensional parameters of the unit cell in the length direction, width direction, and thickness direction, respectively.
[0009] Furthermore, the cross-sectional shape of the warp and weft yarns described in S2 is a flexible shuttle shape.
[0010] Furthermore, the method for determining the basic yarn center path described in S3 is as follows: the warp center path is distributed in a periodic stepped manner along the length of the unit cell; the warp center path is parallel to the weft cross-section when passing through the weft yarn; the tilt angle of the warp path between the peak and valley values is controlled by the angle parameter characterizing the influence of the molding process; the overall warp center path remains continuous and smooth; adjacent warp yarns are offset by one weft cross-section height in the thickness direction; the misalignment of adjacent warp yarns in the weft direction is controlled by the phase difference; the weft center path has a periodically changing curve shape along the width of the unit cell; the amplitude of the periodically changing curve is controlled by the amplitude parameter characterizing the influence of the molding process; the misalignment of adjacent weft yarns in the warp direction is controlled by the phase difference; adjacent weft yarns are offset by one warp cross-section height in the thickness direction.
[0011] Furthermore, the parameters characterizing the influence of the molding process include the amplitude coefficient of the weft yarn center path in the thickness direction and the tilt angle of the warp yarn center path between the peak and valley values.
[0012] Furthermore, the variation law of the yarn cross section along its central path in S4 is determined based on the key characteristics of the influence of the molding process on the posture change of the warp and weft yarn cross sections. The variation law of the yarn cross section along its central path includes the variation law of the rotation angle of the weft yarn cross section, the variation law of the rotation angle of the warp yarn cross section, and the variation law of the bending coefficient of the warp yarn cross section.
[0013] Furthermore, the rotation angle of the weft yarn cross section changes periodically within a width period, and the peak value of its variation is controlled by the tilt angle of the warp yarn center path between the peak and valley values.
[0014] Furthermore, the variation law of the rotation angle of the warp cross section is determined according to the geometric variation relationship of the weft yarn mid-surface in the weft direction, and the variation law of the bending coefficient of the warp cross section is determined according to the amplitude of the weft yarn center path and the weft yarn mid-surface.
[0015] Furthermore, the method for constructing the geometry of the yarn entity is as follows: first, the yarn cross-section is swept along the corrected center path; during the sweeping process, the cross-section orientation is updated in real time according to the rotation angle / bending coefficient change law, so that the cross-section is always perpendicular to the tangent direction of the center path, and finally a three-dimensional entity is formed.
[0016] Furthermore, the generation process of the unit cell geometric model described in S5 specifically includes: obtaining the geometric models of a single warp yarn and a single weft yarn respectively in S4; combining the geometric models of the single warp yarn and the weft yarn according to the spatial arrangement relationship of the unit cell geometric domain and the yarn center path described in S1 to obtain a 2.5D woven composite material yarn geometric model; and then performing Boolean operations or equivalent geometric processing with the matrix geometric model of a preset shape to form a complete 2.5D woven composite material unit cell geometric model.
[0017] Furthermore, the preset shape of the base geometry model is a cuboid.
[0018] The application of the 2.5D woven composite material unit cell geometric model constructed by any of the 2.5D woven composite material unit cell parametric geometric modeling methods disclosed in this invention in numerical analysis.
[0019] The beneficial effects of this invention are: 1. The method described in this invention, under controllable parameters, achieves collaborative modeling of yarn path and cross-sectional geometry through parameterized description of the unit cell geometry, yarn cross-sectional parameters, yarn center path, and cross-sectional rotation law, thereby effectively reflecting the true structural characteristics of 2.5D woven composite materials. Compared with existing methods, this invention improves the engineering applicability and structural reproducibility of the geometric model while ensuring modeling flexibility.
[0020] 2. This invention first defines the yarn cross-section parameterizedly, then corrects the center path, and then couples the path and cross-section parameters. This not only accurately captures the interlacing and undulating shape of the warp and weft yarns, but also reflects the influence of the forming process on the shape, size and rotation law of the yarn cross-section through parameterized description. At the same time, the influence of forming on the path is characterized by key parameters, so that the constructed model can fully reproduce the real structural characteristics of 2.5D woven composite materials and greatly reduce the deviation between the model and the actual structure. Attached Figure Description
[0021] Figure 1 This is a flowchart illustrating one embodiment of the parametric geometric modeling method for 2.5D woven composite material unit cells of the present invention. Figure 2 This is a schematic diagram of the warp center path of the present invention; Figure 3 This is a schematic diagram of the center path of the warp and weft yarns of the present invention; Figure 4 This is a schematic diagram of the warp cross-section of the present invention; Figure 5 This is a schematic diagram illustrating the variation law of the weft yarn cross-section rotation angle within one cycle of the present invention; Figure 6 This is a schematic diagram of the geometric model of a single warp yarn in this invention; Figure 7 This is a schematic diagram of the geometric model of a single weft yarn in this invention; Figure 8 This is a schematic diagram of a 2.5D woven composite yarn geometric model considering the actual structural features of the present invention; Figure 9 This is a schematic diagram of the geometric model of a 2.5D woven composite material unit cell that takes into account the actual structural features of the present invention. Detailed Implementation
[0022] Specific implementation method one: as follows Figure 1-9 As shown in this embodiment, a parametric geometric modeling method for 2.5D woven composite material unit cells specifically involves a method that considers the real structural characteristics of 2.5D woven composite material unit cells. By parametrically describing the influence of the molding process on the yarn spatial path and cross-sectional geometry, the method achieves the geometric construction of the real structure of the woven composite material. The 2.5D woven composite material unit cell yarn structure includes two types: warp yarns and weft yarns. The warp and weft yarns are interlaced within the unit cell according to a predetermined topological relationship, thereby forming a woven structure with thickness-direction undulation characteristics. The topological relationship, through a regularized description, clarifies the arrangement direction, interlacing order, interlacing point position, and avoidance relationship of adjacent yarns within the unit cell, ensuring the periodicity and repeatability of the woven structure.
[0023] like Figure 1 As shown, the 2.5D woven composite material unit cell parametric geometric modeling method includes the following steps: S1: Unit cell geometry domain determination. Based on the structural parameters of the 2.5D woven composite material, the geometric range of the unit cell in space is determined, which is used to define the computational domain for subsequent yarn geometry modeling.
[0024] First, the spatial geometric domain of the unit cell is determined based on the structural parameters of the 2.5D woven composite material. The length of the unit cell is determined by the weft density of the preform and the number of weft yarns in the length direction within the unit cell; the width of the unit cell is determined by the warp density of the preform and the number of warp yarns in the width direction within the unit cell; and the thickness of the unit cell is determined by the cross-sectional thickness of the warp and weft yarns. The structural parameters include, but are not limited to, the arrangement characteristics of the warp and weft yarns in the fabric and the dimensional parameters of the unit cell in the length, width, and thickness directions, respectively. This method determines the spatial geometric domain of the unit cell, which is used to limit the calculation range for subsequent yarn geometry modeling and provides unified spatial constraints for constructing the yarn center path and cross-sectional geometry.
[0025] S2: Parameterized definition of yarn cross-section. Based on the geometric characteristics of the yarn cross-section, the cross-sectional shape and size of the warp and weft yarns are parameterized to obtain the initial yarn cross-section parameters, so as to reflect the influence of the forming process on the yarn cross-section.
[0026] After determining the unit cell geometry, the cross-sectional geometry of the warp and weft yarns is parameterized. The yarn cross-section is described using a parameterizable geometry, and its shape and size are controlled by cross-sectional parameters to reflect the influence of the forming process on the geometric characteristics of the yarn cross-section. Preferably, the cross-sectional shape of the warp and weft yarns is a flexible shuttle shape.
[0027] The weft yarn cross-section can be represented within a unit cell as a spindle-shaped cross-section, meaning the weft yarn cross-section is spindle-shaped or approximately spindle-shaped, with a flat, symmetrical characteristic of being thicker in the middle and thinner at both ends. It encompasses common deformations such as the ideal spindle shape, the flat convex lens shape, and the ellipse shape, and is an important basis for woven structure design and mechanical property prediction. Specifically, such as... Figure 2 As shown, the small hexagonal filled areas represent the weft yarn cross-section. The small hexagons are used to illustrate the random distribution of fibers in the weft yarn. Figure 4 As shown, the purple line represents the weft path, and the red line represents the warp cross-section. The warp cross-section within a unit cell can be represented as a shuttle-shaped cross-section and is flexible. By parametrically describing the warp cross-section profile, the cross-sectional geometry of the warp within the unit cell can be obtained. By parametrically describing the degree of curvature of the warp cross-section, its shape is adapted to the weft path to reflect the true structural characteristics after the warp and weft yarns interweave.
[0028] S3: Yarn center path construction. First, based on the topological relationship of the woven structure and the geometric dimensions of the yarn cross-section obtained in S2, the basic yarn center path is determined. Then, the influence of the forming process on the warp and weft yarn center paths is analyzed, and key feature parameters characterizing this influence are extracted. Finally, the basic yarn center path is corrected using the key feature parameters to obtain the spatial center paths of the warp and weft yarns within the unit cell, and the coordinates of the yarn center paths are obtained. Through the yarn center path construction, all center path parameters are obtained. The yarn center path construction generates the spatial center path through four steps: basic path determination, influence feature extraction, parameter characterization, and path correction. All parameters used to define, correct, or describe the center path are considered center path parameters. The key feature parameters can be obtained from measurement data of the formed structure, image analysis results, empirical settings, or fitting inversion.
[0029] After defining the yarn cross-section parameters, the basic yarn center path is determined based on the topological relationships of the woven structure (such as the rules for warp yarns passing through weft yarns along the thickness and length directions, the misalignment rules for adjacent warp yarns along the width direction, and the misalignment rules for adjacent weft yarns along the length direction) and the geometric dimensions of the yarn cross-section. Correspondingly, the geometric parameters of the basic yarn center path are obtained, including warp basic path parameters (such as the offset height of adjacent warp yarns in the thickness direction, the phase difference of adjacent warp yarns along the width direction, and the start or end X-coordinate of the warp path within the unit cell) and weft basic path parameters (such as the start or end Y-coordinate of the weft yarn within the unit cell, and the offset distance of adjacent weft yarns in the thickness direction). These geometric parameters of the basic yarn center path form the skeleton of the center path, ensuring the rationality of the yarn's topological relationships. Specifically, the method for determining the basic yarn center path is as follows: the warp yarn center path is distributed in a periodic stepped manner along the length of the unit cell; the warp yarn center path is parallel to the weft yarn cross-section when passing through the weft yarn, and the overall warp yarn center path remains continuous and smooth; adjacent warp yarns are offset by one weft yarn cross-section height in the thickness direction; the misalignment of adjacent warp yarns in the weft direction is controlled by a phase difference; the weft yarn center path has a periodically changing curve shape along the width of the unit cell, and the misalignment of adjacent weft yarns in the warp direction is controlled by a phase difference; adjacent weft yarns are offset by one warp yarn cross-section height in the thickness direction. Then, by analyzing the changes in the warp and weft yarn center paths after the forming process (such as weaving tension and yarn extrusion), key characteristic parameters affecting the warp and weft yarn center paths during the forming process are extracted. This includes the tilt angle of the warp path between peaks and troughs (defined as the tilt angle of the warp path between the peak and trough values within a period, when passing through the weft cross-section, describing the warp tilt caused by the flat extrusion preform) and the amplitude of the weft center path (defined as the amplitude of the weft center path described by a periodic curve, describing the weft fluctuation caused by the flat extrusion preform). Based on these key parameters, the basic yarn center paths are corrected to obtain the actual spatial center paths of the warp and weft yarns within the unit cell. The corrected spatial center path coordinate parameters are obtained, including path point coordinates (three-dimensional coordinate points discretized along the path, describing the spatial orientation of the path), path tangent direction vectors (the tangent direction at each path point is used for subsequent coupling between the cross-section and the path, such as the cross-section normal being perpendicular to the tangent), and path amplitude (a geometric quantity describing the curvature of the periodic weft path). The spatial center paths of the warp and weft yarns within the unit cell are constructed separately to describe the interlacing and undulation characteristics of the yarns in the fabric.
[0030] like Figure 2 and Figure 3 As shown, Figure 2 This is a schematic diagram of the warp yarn center path, where the solid red line represents the warp yarn center path and the dashed purple line represents the parallel line of the weft yarn cross-section outline. Figure 3This diagram illustrates the center paths of warp and weft yarns. The center path line parallel to the X-direction is the warp center path line, and the center path line parallel to the Y-direction is the weft center path line. The corrected yarn center paths can describe the interlacing relationship and spatial undulation characteristics of warp and weft yarns within the unit cell.
[0031] S4: Path and cross-section parameter coupling modeling. The initial yarn cross-section parameters (such as shape, size, rotation law, etc.) obtained in S2 are coupled with the center path parameters obtained in S3 to determine the variation law of the cross-section parameters along its center path, obtain the cross-section coordinates after the cross-section changes along the path, and construct the yarn entity geometry. The variation law of the yarn cross-section along its center path is determined based on the key features of the influence of the forming process on the posture changes (including rotation / bending) of the warp and weft yarn cross-sections.
[0032] After obtaining the yarn center path and cross-sectional parameters, the yarn cross-sectional parameters are coupled with the center path parameters to generate the three-dimensional geometry of the yarn. Based on observation and analysis of the actual yarn structure, key features affecting the rotation of the warp and weft yarn cross-sections during the forming process are extracted, and the variation law of the yarn cross-section along the center path is determined accordingly. Specifically, the variation law of the yarn cross-section along its center path includes the variation law of the rotation angle of the weft yarn cross-section, the variation law of the rotation angle of the warp yarn cross-section, and the variation law of the cross-sectional curvature coefficient. The rotation angle of the weft yarn cross-section changes periodically within a width period, and the peak value of its variation law is controlled by the tilt angle of the warp yarn center path between the peak and trough values. The variation law of the rotation angle of the warp yarn cross-section is determined based on the geometric variation relationship of the weft yarn mid-surface in the weft direction, and the variation law of the warp yarn cross-section curvature coefficient is determined based on the amplitude of the weft yarn center path and the weft yarn mid-surface.
[0033] like Figure 5 The diagram illustrates the variation of the weft yarn cross-section rotation angle within one cycle. This variation can be described by parameters, where Angle represents the maximum value of the weft yarn cross-section rotation angle. The variation of the warp yarn cross-section rotation angle can be extracted from the weft yarn's mid-surface. Through this parameter-coupled modeling method, a yarn solid geometry reflecting the true structural characteristics can be constructed. Specifically, the method for constructing the yarn solid geometry is as follows: first, the yarn cross-section is swept along the corrected center path; during the sweeping process, the cross-section orientation is updated in real time according to the aforementioned rotation angle / bending coefficient variation law, ensuring that the cross-section is always perpendicular to the tangent direction of the center path, ultimately forming a three-dimensional solid.
[0034] S5: Unit cell geometry model generation. Based on the unit cell geometry domain obtained in S1, the yarn center path coordinates obtained in S3, and the cross-sectional coordinates after the cross-section changes along the path obtained in S4, a complete 2.5D woven composite material unit cell geometry model is generated and output. The specific process of generating the unit cell geometry model includes: In step S4, geometric models of a single warp yarn and a single weft yarn are obtained respectively. The geometric models of the single warp yarn and the weft yarn are combined according to the spatial arrangement relationship of the unit cell geometric domain and the yarn center path described in step S1 to obtain a 2.5D woven composite material yarn geometric model. Based on the 2.5D woven composite material yarn geometric model, Boolean operations or equivalent geometric processing are performed with a matrix geometric model of a preset shape (preferably a cuboid) to form a complete 2.5D woven composite material unit cell geometric model.
[0035] Specifically, after completing the three-dimensional geometry construction of the yarn, geometric models of a single warp yarn and a single weft yarn are obtained, such as... Figure 6 and Figure 7 As shown. Then, the geometric models of single warp and weft yarns are combined according to the peak phase deviation rules of adjacent warp yarns in the width direction and adjacent weft yarns in the length direction in the woven structure. This, combined with the actual number of warp and weft yarn layers in the thickness direction, generates a 2.5D woven composite yarn geometric model that considers the real structural characteristics, as shown. Figure 8 As shown. Based on this, Boolean operations or equivalent geometric processing are performed on a matrix geometric model (preferably a cuboid) with the same preset shape as the unit cell domain to finally obtain a 2.5D woven composite material unit cell geometric model that considers the real structural features, such as... Figure 9 As shown, this is output as the modeling result for subsequent numerical analysis or engineering applications.
[0036] This invention first defines the yarn cross-section parametrically, then corrects the center path, and finally couples the path and cross-section parameters. This not only accurately captures the interlacing and undulating patterns of warp and weft yarns, but also reflects the influence of the forming process on the shape, size, and rotation of the yarn cross-section through parametric description. Simultaneously, it characterizes the influence of forming on the path through key parameters, enabling the constructed model to fully reproduce the true structural characteristics of 2.5D woven composite materials, significantly reducing the deviation between the model and the actual structure. This solves the problem of existing methods failing to simultaneously consider the true spatial undulations of the yarn, cross-sectional geometric changes, and parameter controllability, leading to significant deviations between the model and the actual fabric structure.
[0037] This invention provides a parametric geometric modeling method for 2.5D woven composite materials considering real structural characteristics. Under controllable parameters, this method achieves collaborative modeling of yarn path and cross-sectional geometry by parametrically describing the unit cell geometric domain, yarn cross-sectional parameters, yarn center path, and cross-sectional rotation law, thereby effectively reflecting the real structural characteristics of 2.5D woven composite materials. Compared with existing methods, this invention improves the engineering applicability and structural reproducibility of the geometric model while maintaining modeling flexibility. It achieves an effective description of the real structural characteristics of woven composite materials, providing a reliable geometric model foundation for subsequent numerical analysis and engineering applications.
[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.
Claims
1. A parametric geometric modeling method for a 2.5D woven composite material unit cell, wherein the 2.5D woven composite material unit cell yarn structure includes warp and weft yarns, characterized in that... Includes the following steps: S1: Determination of unit cell geometry: Based on the structural parameters of 2.5D woven composite materials, the geometric range of the unit cell in space is determined. S2: Parameterized definition of yarn cross-section. Based on the geometric features of the yarn cross-section, the cross-sectional shape and size of the warp and weft yarns are parameterized to obtain the initial yarn cross-section parameters. S3: Yarn center path construction. First, based on the topological relationship of the woven structure and the geometric dimensions of the yarn cross-section obtained in S2, the basic yarn center path is determined. Then, the influence of the forming process on the warp and weft yarn center paths is analyzed, and key feature parameters characterizing this influence are extracted. Finally, the basic yarn center path is corrected using the key feature parameters to obtain the spatial center paths of the warp and weft yarns within the unit cell, and the yarn center path coordinates are obtained. Through the yarn center path construction, all center path parameters are obtained. S4: Path and cross-section parameter coupling modeling, the initial yarn cross-section parameters obtained in S2 are coupled with the center path parameters obtained in S3 to determine the variation law of the cross-section along its center path, obtain the cross-section coordinates after the cross-section changes along the path, and construct the yarn entity geometry; S5: Unit cell geometry model generation. Based on the unit cell geometry domain obtained in S1, the yarn center path coordinates obtained in S3, and the cross-sectional coordinates after the cross-section changes along the path obtained in S4, a complete 2.5D woven composite material unit cell geometry model is generated and output.
2. The 2.5D woven composite material unit cell parametric geometric modeling method according to claim 1, characterized in that... The structural parameters described in S1 include the arrangement characteristics of warp and weft yarns in the fabric, and the dimensional parameters of the unit cell in the length, width, and thickness directions, respectively.
3. The method for parametric geometric modeling of 2.5D woven composite material unit cells according to claim 1, characterized in that... The cross-sectional shape of the warp and weft yarns described in S2 is a flexible, approximately shuttle-shaped structure.
4. The method for parametric geometric modeling of 2.5D woven composite material unit cells according to claim 1, characterized in that... The method for determining the basic yarn center path described in S3 is as follows: the warp yarn center path is distributed in a periodic stepped manner along the length of the unit cell. When the warp yarn center path passes through the weft yarn, it is parallel to the weft yarn cross-section. The tilt angle of the warp yarn path between the peak and valley values is controlled by the angle parameter characterizing the influence of the molding process. The overall warp yarn center path remains continuous and smooth. Adjacent warp yarns are offset by one weft yarn cross-section height in the thickness direction. The misalignment of adjacent warp yarns in the weft direction is controlled by the phase difference. The weft yarn center path has a periodic changing curve shape along the width of the unit cell. The amplitude of the periodic changing curve is controlled by the amplitude parameter characterizing the influence of the molding process. The misalignment of adjacent weft yarns in the warp direction is controlled by the phase difference. Adjacent weft yarns are offset by one warp yarn cross-section height in the thickness direction.
5. The 2.5D woven composite material unit cell parametric geometric modeling method according to claim 4, characterized in that... The parameters characterizing the influence of the molding process include the amplitude coefficient of the weft yarn center path in the thickness direction and the tilt angle of the warp yarn center path between the peak and valley values.
6. The method for parametric geometric modeling of 2.5D woven composite material unit cells according to claim 1, characterized in that... The variation law of the yarn cross section along its central path in S4 is determined based on the key characteristics of the influence of the molding process on the posture change of the warp and weft yarn cross sections. The variation law of the yarn cross section along its central path includes the variation law of the rotation angle of the weft yarn cross section, the variation law of the rotation angle of the warp yarn cross section, and the variation law of the bending coefficient of the warp yarn cross section.
7. The method for parametric geometric modeling of 2.5D woven composite material unit cells according to claim 6, characterized in that... The rotation angle of the weft yarn section changes periodically within a width period, and the peak of its variation is controlled by the tilt angle of the warp yarn center path between the peak and valley values.
8. The method for parametric geometric modeling of 2.5D woven composite material unit cells according to claim 6, characterized in that... The variation law of the rotation angle of the warp cross section is determined according to the geometric variation relationship of the weft yarn mid-surface in the weft direction, and the variation law of the bending coefficient of the warp cross section is determined according to the amplitude of the weft yarn center path and the weft yarn mid-surface.
9. The method for parametric geometric modeling of 2.5D woven composite material unit cells according to claim 6, characterized in that... The specific method for constructing the geometry of the yarn entity is as follows: the yarn cross-section is swept along the modified center path. During the sweeping process, the cross-section orientation is updated in real time according to the change law of the rotation angle / bending coefficient, so that the cross-section is always perpendicular to the tangent direction of the center path, and finally a three-dimensional entity is formed.
10. The method for parametric geometric modeling of 2.5D woven composite material unit cells according to claim 1, characterized in that... The generation process of the unit cell geometric model described in S5 specifically includes: obtaining the geometric models of a single warp yarn and a single weft yarn respectively in S4; combining the geometric models of the single warp yarn and the weft yarn according to the spatial arrangement relationship of the unit cell geometric domain and the yarn center path to obtain a 2.5D woven composite material yarn geometric model; and then performing Boolean operations or equivalent geometric processing with the matrix geometric model of a preset shape to form a complete 2.5D woven composite material unit cell geometric model.