CN115985421A - Fabric composite finite element modeling method based on microcosmic geometric model - Google Patents

Abstract

The invention relates to the field of woven composite material modeling, in particular to a fabric composite material finite element modeling method based on a micro-geometric model, which comprises the steps of establishing a micro-geometric model of a representative volume unit of a composite material woven fabric, and outputting a surface triangular surface patch model after calculation; periodically mapping the triangular patch model into a composite material domain, and calculating surface intersection points of the triangular patches in a grid line domain; repairing the penetration and narrow gaps among different yarns along the direction of the grid lines; adjusting grid node coordinates to match the adjacent surface intersection points and setting grid node labels; judging the splitting mode of the surface according to the four nodes of the surface of the hexahedron unit; and splitting the hexahedral unit into a tetrahedron, a pyramid and a triangular prism unit again according to the splitting mode of the surface, setting a corresponding label set for the unit according to the label type of the unit, and simultaneously storing the material direction corresponding to the unit. The method can establish a finite element model of the high-fidelity woven composite material, and has a very wide application prospect.

Description

A Finite Element Modeling Method for Fabric Composite Materials Based on Microscopic Geometry Model

technical field

The invention relates to the field of modeling of woven composite materials, in particular to a finite element modeling method for textile composite materials based on a microscopic geometric model.

Background technique

As a new type of high-performance composite material, woven composite material has the characteristics of high specific modulus, high specific strength and good manufacturability, and has been widely used in aerospace, military and other fields. The woven fabric reinforcement in the woven composite material is regularly woven through the warp, weft and binder yarns according to a specific topological structure, and has obvious multi-scale characteristics, and its microstructure and mesostructure directly affect the macroscopic structure of the composite material. performance.

The mesoscale unit cell of woven composites is composed of yarn and matrix, in which yarn is composed of fiber tow and matrix infiltrated between fibers. However, the mesoscopic yarns of woven composites have complex geometries due to the mutual extrusion and deformation of fiber tows during the weaving process. In the previous modeling research work, certain ideal assumptions were made on the cross-section and path of the mesoscopic yarn, but the real cross-section of the mesoscopic yarn changes dynamically with the path, and the ideal assumption often has certain differences with the real structure. Therefore, in order to reflect the mesoscopic yarn structure of woven composites more realistically, it is necessary to fully consider the deformation of the fabric when modeling.

For the mesoscopic modeling of woven composite materials, the usual method is based on the scanning electron microscope, optical microscope and Micro-CT scanning results, and assumes a certain cross-section and path of the yarn, so as to create a woven composite material in a parametric way Ideal model of mesostructure. However, the ideal geometric modeling method is mostly used for woven composite materials with low fiber volume content. When the fiber volume content is high, the yarns will have different waviness due to the mutual extrusion deformation between the yarns and the yarn cross-section will have certain asymmetry and torsion. The regular yarn shape and trajectory assumed by the ideal geometric model are far from the real model, and even the yarn geometric model will interfere to a certain extent, which cannot meet the needs of mechanical performance analysis.

The numerical calculation method based on finite element is an important and effective method to study composite materials. This method requires the establishment of a finite element model of the material. Whether the model can effectively reflect the internal structure of the material directly affects the accuracy of subsequent predictions of the mechanical properties of the material; Digital modeling method, which realizes the geometric modeling of composite material reinforcement, but this method cannot realize composite material matrix modeling and overall mesh division.

At present, the traditional meshing method is only suitable for the meshing of the mesostructure of woven composites with idealized (yarn cross-section is ellipse, racetrack, lens, etc.), and only for each yarn and matrix of the reinforcement respectively. Carry out mesh division, and then combine reinforcement and matrix meshes to form composite meshes, so that there is some interference between the meshes between yarn-yarn and yarn-matrix interfaces, which will affect the subsequent finite element simulation results.

Contents of the invention

Based on the problems existing in the prior art, the purpose of the present invention is to provide a finite element modeling method for fabric composite materials based on the microscopic geometric model. The present invention can not only establish an accurate geometric model based on the microscopic geometric model of the woven fabric, but also consider the Interfacial relationship between the various components of the material, eliminating inter-yarn interference and narrow gaps, and generating an accurate finite element model of the woven composite material. Based on the micro-scale woven fabric unit cell model, the high-truth finite element model of composite materials can be quickly established to improve the prediction accuracy of finite element mechanical properties. It is suitable for the development of 2D and 3D woven composite materials with various geometric structures, which greatly improves The development efficiency of woven fabric composite materials and the reduction of development costs have great application prospects.

To achieve the above object, the present invention provides the following technical solutions:

A finite element modeling method for fabric composite materials based on a microscopic geometric model, comprising the following steps:

(1) Establish a representative volume unit micro-geometric model of the woven fabric;

(2) Calculate the yarn axis direction based on the microscopic geometric model of the representative volume unit, and output the surface triangle patch model of the woven fabric yarn;

(3) Establish a composite material domain, add matrix material and discretize the composite material domain into hexahedral units;

(4) map the surface triangular patch model of the yarn in step (2) to the composite material domain, calculate the intersection point of the triangle patch and the mesh line in the composite material domain, and save the topological relationship of the mesh line surface intersection point;

(5) Repair inter-yarn penetration and narrow gaps between different yarns caused by scale conversion along the grid line direction;

(6) Adjust the grid node of the composite material domain to the intersection point of the adjacent grid line surface, and set the topology label of the grid node;

(7) traverse the surface of the hexahedron unit, judge the split mode of the corresponding six surfaces according to the four grid nodes of each surface, and determine the split line;

(8) Split the hexahedron unit into tetrahedron, pyramid and triangular prism units again according to the splitting mode of the six surfaces in the hexahedron unit, store them as corresponding component unit sets according to the labels of each unit, and obtain the materials corresponding to each unit direction.

Compared with the prior art, the benefits of the present invention include:

The invention can carry out the development of the woven composite material product completely digitally, without needing real fabrics. The product development cycle is greatly reduced. At the same time, the fidelity of the finite element model based on micro-geometric structure reconstruction can be effectively guaranteed, and the overall mesh division can identify and repair the penetration and narrow gaps between different yarns, and match yarn-yarn and yarn -Matrix interface makes everything fit together perfectly. The invention can improve the prediction accuracy of the mechanical properties of the woven composite material, and can well guide the development and verification of the woven composite material product.

Description of drawings

Fig. 1 is a kind of flow chart of the finite element modeling method of fabric composite material based on the microscopic geometry model of the embodiment of the present invention;

Fig. 2 is a schematic diagram of the topological structure of a representative volume unit of a three-dimensional orthogonal fabric according to an embodiment of the present invention;

FIG. 3 is a microscopic geometric model of a representative volume unit of a three-dimensional orthogonal fabric according to an embodiment of the present invention;

Fig. 4 is a schematic diagram of the fiber node of the weft section slice of the three-dimensional orthogonal fabric according to the embodiment of the present invention;

Fig. 5 is a schematic diagram of boundary nodes of a weft section of a three-dimensional orthogonal fabric according to an embodiment of the present invention;

Fig. 6 is the three-dimensional orthogonal fabric surface triangular patch model of the embodiment of the present invention;

Fig. 7 is a schematic diagram of mapping between triangular patches and composite material domains according to an embodiment of the present invention;

Fig. 8 is a schematic diagram of grid line surface intersection calculation according to an embodiment of the present invention;

Fig. 9 is a schematic diagram of inter-yarn penetration and narrow gap adjustment according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of grid node adjustment according to an embodiment of the present invention;

Fig. 11 is a schematic diagram of a hexahedral unit surface split mode according to an embodiment of the present invention;

Fig. 12 is a schematic diagram of disassembly of a hexahedron unit according to an embodiment of the present invention;

Fig. 13 is a finite element mesh model of a three-dimensional orthogonal fabric composite material according to an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Wherein, the accompanying drawings are for illustrative purposes only, and represent only schematic diagrams, rather than physical drawings, and should not be construed as limiting the present invention; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, Enlargement or reduction does not represent the size of the actual product; for those skilled in the art, it is understandable that certain known structures and their descriptions in the drawings may be omitted.

Fig. 1 is a kind of flow chart of the finite element modeling method of fabric composite material based on the microscopic geometric model of the embodiment of the present invention; As shown in Fig. model method, including the following steps:

(1) Establish the micro-geometric model of the representative volume unit of the woven fabric, as follows:

(1.1) Define the yarn parameters of each component of the woven fabric, the size of the representative volume unit and the key nodes of the organization, and establish the topology of the representative volume unit of the woven fabric;

In some embodiments of the present invention, the step (1.1) may also specifically include: setting parameters such as the initial cross-sectional area and modulus of the yarn, setting the dimensions in the direction of the warp (length direction) and weft (width direction) of the fabric, and defining the woven fabric The coordinates of the key points and the initial path of the yarn establish the topology of the representative volume unit of the fabric whose cross-sectional shape is circular and the yarn path is a broken line. As shown in Figure 2, the three-dimensional orthogonal fabric topology includes warp yarns, weft yarns and joints. Knot yarn with three yarns.

(1.2) Set the boundary conditions of the topological structure unit and apply the yarn tension, discretize the yarn into micro-geometric units through the discretization of yarn fibers and fiber digital units, and perform numerical calculations on the discretized yarns to obtain micro-geometric unit cells Model.

In some embodiments of the present invention, the step (1.2) may also specifically include: setting periodic boundary conditions in the warp and weft directions, and under the condition that the cross-sectional area of the yarn is kept constant, dividing the warp yarn, weft yarn and binding yarn equally For 64, 64 and 16 virtual fibers, the virtual fibers are discretized into digital units (rod units and fiber nodes), and the length of the digital units is 0.5 times the diameter of the virtual fiber. A constant tension is applied at both ends of the yarn to cause relative movement between the fibers, to realize the change of the yarn path and cross-sectional shape, until it is close to the real fabric structure. As shown in Figure 3, the microscopic geometric model of the representative volume unit of the three-dimensional orthogonal fabric, the final size of the representative volume unit is 13.64*5.976*5.9753mm (length*width*thickness).

(2) Calculate the direction of the yarn axis based on the microscopic geometric model of the representative volume unit, and output the triangular patch model of the yarn surface of the woven fabric, as follows:

(2.1) Obtain the three-dimensional coordinate data of the fiber nodes of the model in step (1) and record the corresponding topological relationship;

Wherein, it can be understood that, in the embodiment of the present invention, the virtual fibers belonging to the same yarn have the same number of fiber nodes, and the fiber nodes of the same virtual fiber are sorted in sequence according to the direction of the yarn path, and the fiber nodes can be formed according to the above relationship topological relationship.

(2.2) Calculate the yarn central axis path node through the three-dimensional coordinates of the node, slice the yarn section evenly along the path direction of each yarn, and obtain the interpolation point of each fiber on the yarn section;

In some embodiments of the present invention, the step (2.2) may also specifically include: calculating the average value of fiber nodes of the same yarn and the same serial number as the yarn path nodes, and connecting the yarn path nodes sequentially as the yarn path direction. Calculate the normal vector of the sectional plane along the direction of the yarn path, the distance between two adjacent sectional planes is about 1-5 times the length of the virtual fiber rod unit, and obtain the interpolation point of the virtual fiber rod unit on the sectional plane, as shown in Figure 4. Schematic illustration of the interpolation points for the yarn path direction.

(2.3) adopt Delaunay triangulation algorithm and Alpha-shape algorithm adaptive acquisition step (2.2) in the boundary of yarn section interpolation point, obtain yarn section polygonal boundary profile;

In some embodiments of the present invention, the step (2.3) may also specifically include: traversing the cross-section plane interpolation points in step (2.2), taking the interpolation point as the center, and taking the corresponding virtual fiber radius as the radius on the cross-section plane to increase by 8 on average -20 interpolation points, use the Delaunay triangulation algorithm to calculate the Delaunay triangulation of all interpolation points on the same section plane. Delete any triangle whose edge is greater than Alpha in the Delaunay triangulation to obtain the Alpha-shape of the triangulation, where Alpha is 5-10 times the diameter of the virtual fiber. The boundary of the extracted remaining Delaunay triangulation is the polygonal boundary contour of the yarn section, and the cross-section boundary nodes are obtained through homogenization and interpolation along the contour. Figure 5 is a schematic diagram of the boundary nodes of a weft yarn section.

It should be noted that in order to ensure the correct generation of subsequent triangular patches, it is necessary to ensure that the number of boundary nodes of each section of the same yarn is the same.

(2.4) Perform homogenization and interpolation on the section polygon in step (2.3) to obtain the vertices of the triangular patch, and then generate the surface triangular patch model of the yarn according to a specific order.

In some embodiments, as shown in FIG. 6 , the surface triangle patch model of the yarn is obtained by connecting the boundary nodes on two adjacent sectional planes according to a specific sequence of boundary nodes.

(3) Establish a composite material domain, add matrix material and discretize the composite material domain into hexahedral units, which may include the following:

(3.1) Read the size of the representative volume unit of the fabric, and set the min and max key nodes of the composite material domain;

In some embodiments of the present invention, the step (3.1) may also specifically include: assuming that the midpoint of the composite material domain is P _cmid (x _cmid , y _cmid , z _cmid ), all fibers in the microscopic geometric model of the representative volume unit of the woven fabric The midpoint of the node is P _tmid (x _tmid , y _tmid , z _tmid ), then x _cmid = x _tmid + x _off , y _cmid = y _tmid + y _off , z _cmid = z _tmid , where x _off and y _off are The midpoint of the composite material domain is offset along the x and y directions (longitude and latitude directions) (±1/2*length in the x direction, ±1/2*width in the y direction). Define the minimum value point P _cmin (x _cmin ,y _cmin ,z _cmin ) and the maximum value point P _cmax (x _cmax ,y _cmax ,z _cmax ) of the composite material domain, there is x _cmin ＝x _cmid -1/2*length，y _cmin = y _cmid -1/2*width, z _cmin = z _cmid -1/2*thickness*(1+z _inc ), x _cmax = x _cmid +1/2*length, y _cmax = y _cmid +1/ 2*width, z _cmax =z _cmid +1/2*thickness*(1+z _inc ), where z _inc is the thickness increase percentage in the z direction (zi _inc is greater than or equal to 0 according to different composite material structures). The cuboid region formed by the two points P _cmin and P _cmax along the three positive directions of x, y and z is the composite material domain including the woven fabric reinforcement and the matrix material.

(3.2) Set the appropriate hexahedral unit size according to the fiber size and cross-sectional parameters of the fabric, and uniformly discretize the material domain in step (3.1) into hexahedral units of corresponding size.

In some embodiments of the present invention, the step (3.2) can also specifically include: setting the dimensions of the hexahedron unit in the x, y and z directions, the size can be set according to the average diameter of all the virtual fibers of the fabric, too small a unit size will lead to The number of grids increases sharply, increasing the consumption of computing resources. Excessively large element sizes will result in the loss of some details of the fabric, which will affect the accuracy of subsequent simulations. Generally, the unit size is set to be 1-5 times the average diameter of the virtual fiber. The composite material domain surrounded by the two points P _cmin and P _cmax in step (3.1) is uniformly discretized into hexahedral units, as shown in Figure 7, the cuboid area is the composite material domain after migration.

(4) Map the triangular patch model of the yarn surface in step (2) to the composite material domain, calculate the intersection point of the triangular patch and the grid line in the composite material domain, and save the topological relationship of the grid line surface intersection point, details as follows:

(4.1) Map the triangular facet on the surface of the yarn into the composite material domain, calculate the surface intersection points of the triangular facet and the grid lines in the three directions of x, y and z, and record the topological information of the intersection;

In some embodiments of the present invention, the step (4.1) may also specifically include: as shown in FIG. 7 , mapping the yarn surface triangular facets to the composite material domain, because the composite material domain may be affected in step (3). Offsets are made in the warp and weft directions, the portion of the triangular patch shown is not in the composite domain, the triangular surface not in the composite domain is periodically mapped to the other side of the representative volume element, and the triangular patch is calculated Intersect with the surface of grid lines in the three directions of x, y and z, and record the topological information of the intersection as shown in Figure 8. The schematic diagram of calculating the intersection is shown in Figure 8. Triangle abc is a triangular patch on the surface of a yarn, and triangle a'b'c' , a"b"c" and a"'b"'c"' are the vertical projections of the triangle abc on the xoy, xoz and zoy planes respectively. Taking the xoy plane as an example, first determine whether there is a grid node inside the triangle a'b'c' of the xoy plane, if there is a grid node, calculate the coordinates of the corresponding node, and back-project it to the triangle surface abc for calculation The coordinates of the projected point; if it does not exist, it will not be calculated, and the projected point is the surface intersection point of the yarn and the grid line. Judge the vertical projection of the triangle abc on the xoz and zoy planes in turn. Points 1, 2, and 3 are the intersection points of the yarn surface triangle abc and the grid line surface in the x, y, and z directions.

(4.2) Periodically map the grid line surface intersection points on the six-face boundary of the composite material domain, so that the grid line surface intersection points meet the periodic boundary conditions of the representative volume unit.

It can be understood that by periodically mapping the triangular patch mesh to the gridline-surface intersections on the six-surface boundaries of the review material domain, the topological relationship of the gridline-surface intersections can be reflected, so that the gridlines Surface intersection points satisfy periodic boundary conditions for representative volume elements.

(5) Repair inter-yarn penetration and narrow gaps between different yarns caused by scale conversion along the grid line direction, as follows:

(5.1) Extract the intersection points of the yarns on the grid line surface in the x, y and z directions respectively and sort them according to their x, y or z coordinate values; as shown in Figure 9(a)-(b), there is a vertical direction There are 2-4 surface intersections of unequal grid lines on the grid line;

(5.2) According to the x, y or z value of grid line intersection and its topological relationship, adjust the intersection of two interpenetrating different yarn surfaces to be the midpoint of the two points, and swap the topological labels of the two nodes at the same time. Adjust the intersection of two different yarn surfaces whose distance is less than the set threshold to the midpoint of the two points.

In some embodiments of the present invention, the step (5.2) may also specifically include: according to the x, y or z value of the grid line surface intersection point and its topological relationship, as shown in Figure 9 (a), Yarn1 and Yarn2 are two staggered yarn, where i ₁ and i ₂ are the intersection points of the grid line surfaces of Yarn1 and Yarn2 respectively, and penetration occurs on the surface of Yarn1 and Yarn2. Similarly, there is a narrow gap (narrow gap) between Yarn1 and Yarn2 yarns in Figure 9(b). The judgment threshold is less than 1/3 times the grid size). Adjust the intersection point of the surface of the two mesh lines with penetration or narrow gap to the midpoint of the two points, as shown in Figure 9 (a)-(b) The hollow node is the adjusted surface intersection point, and the dotted line is the material boundary line of the two yarns .

(6) Adjust the grid nodes of the composite material domain to the intersection points of the adjacent grid line surfaces, and set the topology labels of the grid nodes, as follows:

(6.1) Read the adjusted gridline surface intersection in step (5), judge that the gridline surface intersection is adjacent to the grid node and store the gridline surface intersection in the corresponding grid node adjacency linked list, as shown in Figure 10 ( As shown in a), taking a plane as an example, there are three surface intersections S ₁ , S ₂ and S ₃ in the adjacency linked list of grid node N ₁ .

(6.2) Traversing all grid nodes, if the grid node adjacency linked list is zero, then there is no need to adjust the grid node, and set the label of the grid node as the label corresponding to a single component. Otherwise adjust the grid node coordinates to the midpoint of the intersection of all adjacent surfaces, and set the grid node label to the corresponding multicomponent label.

In some embodiments of the present invention, _the step (6.2) may also specifically include: traversing all grid nodes, as shown _in Fig. 10(a), N ₁ has three adjacent grid surface intersections, and adjusting ₂ and S ₃ midpoint, set the label _of N _{1 as} a multi-component label; as shown _{in Fig .} The label of the grid node is a multi-component label; as shown in Figure 10(a), the adjacency list of the grid node N ₃ is zero, so there is no need to adjust the grid node, and the label of the N ₃ grid node is set to correspond to a single component label. Figure 10(b) is a schematic diagram of the adjusted grid nodes, where the unadjusted grid nodes are all single component labels.

(7) Traversing the surface of the hexahedron unit, judging the splitting mode of the corresponding six surfaces according to the four grid nodes of each surface, and determining the splitting line, as follows:

Read the four vertex labels corresponding to the quadrilateral, and judge whether the quadrilateral needs to be divided into two triangles according to the number of labels and the type of the label. If it needs to be divided, add the adjacent grid nodes of the grid node, as shown in Figure 9. There are 6 types Surface split mode, m mesh nodes belong to two or more materials, s mesh nodes belong to a single material. In Figure 11(a), there are 4 grid nodes s grid nodes, and no division lines are added to the surface; in Figure 11(b)-(c), one node or two nodes on the same side are m nodes, so m nodes and s nodes must contain the same label, and the surface does not need to add dividing lines; Figure 11(d)-(f) contains 2 or more m nodes, and m nodes all contain the label of s node, then the surface is a material , there is no need to add dividing lines, on the contrary, it is necessary to add dividing lines at 2 m nodes.

It should be noted that the regular quadrilateral and the order of m-nodes and s-nodes shown in Figure (11) are schematic diagrams, and non-regular quadrilateral surfaces shown in Figure (10) may appear, and different node distribution orders can be obtained by rotating the graph (11) corresponds to the node distribution order.

(8) According to the splitting mode of the six surfaces in the hexahedral unit, the hexahedral unit is divided into tetrahedron, pyramid and triangular prism units again, and the topological labels of the grid intersection points of each unit are stored as corresponding component unit sets, and obtained The material direction corresponding to each unit is as follows:

(8.1) Read the adjacent points of the hexahedral unit nodes, divide the hexahedral unit into one component, two components or three components according to the node label, and then split each component into tetrahedron, pyramid or triangular prism unit, if necessary, nodes can be added inside the hexahedron unit for splitting. As shown in Figure 12(a), there are two dividing lines on the two faces of the hexahedral unit, and the unit is split into two triangular prism units; as shown in Figure 12(b), the hexahedral unit belongs to two or three components, The units are split into 1 tetrahedral unit, 1 pyramidal unit and 1 triangular prism unit. Figure 13(a)-(c) are the composite finite element mesh, composite reinforcement woven mesh and matrix mesh respectively.

(8.2) Judgment unit set Each unit corresponds to the adjacent yarn path node in step (2), and the unit material direction is set as the path direction of the node.

In summary, the finite element modeling method for fabric composite materials provided by the present invention realizes fully digital finite element model modeling without the need for idealized assumptions and accurate real models; Transformation; achieve inter-yarn penetration and narrow gap repair, mesh node adjustment and attribute assignment; perfect meshing between yarn-yarn and yarn-matrix interfaces; obtain a composite material mesh model with material attribute information, for defining materials The isotropic properties provide a basis; at the same time, the mesh model meets the periodic boundary of the representative volume unit; it greatly improves the development efficiency and simulation accuracy of fabric composite materials, and reduces the development cycle of fabric composite materials.

Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the above-mentioned embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, and the storage medium can include: ROM, RAM, disk or CD, etc.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (10)

1. A finite element modeling method for fabric composites based on micro-geometric model, comprising the following steps: (1) Establish a representative volume unit micro-geometric model of the woven fabric; (2) Calculate the yarn axis direction based on the microscopic geometric model of the representative volume unit, and output the surface triangle patch model of the woven fabric yarn; (3) Establish a composite material domain, add matrix material and discretize the composite material domain into hexahedral units; (4) map the surface triangular patch model of the yarn in step (2) to the composite material domain, calculate the intersection point of the triangle patch and the mesh line in the composite material domain, and save the topological relationship of the mesh line surface intersection point; (5) Repair inter-yarn penetration and narrow gaps between different yarns caused by scale conversion along the grid line direction; (6) Adjust the grid node of the composite material domain to the intersection point of the adjacent grid line surface, and set the topology label of the grid node; (7) traverse the surface of the hexahedron unit, judge the split mode of the corresponding six surfaces according to the four grid nodes of each surface, and determine the split line; (8) Split the hexahedron unit into tetrahedron, pyramid and triangular prism units again according to the splitting mode of the six surfaces in the hexahedron unit, store them as corresponding component unit sets according to the labels of each unit, and obtain the materials corresponding to each unit direction. 2. a kind of fabric composite material finite element modeling method based on micro-geometry model as claimed in claim 1, is characterized in that: described step (1), is specifically as follows: (1.1) Define the yarn parameters of each component of the woven fabric, the size of the representative volume unit and the key nodes of the organization, and establish the topology of the representative volume unit of the woven fabric; (1.2) Set the topological structure boundary conditions and apply yarn tension, discretize the yarn into micro-geometric units through the discretization of yarn fibers and fiber digital units, and perform numerical calculations on the discretized yarns to obtain the micro-geometric unit cell model . 3. a kind of fabric composite material finite element modeling method based on micro-geometry model as claimed in claim 1, is characterized in that: described step (2), specifically as follows: (2.1) Obtain the fiber node three-dimensional coordinate data of the model in step (1) and record its corresponding topological relationship; (2.2) Calculate the yarn central axis path node through the three-dimensional coordinates of the node, slice the yarn section evenly along the path direction of each yarn, and obtain the interpolation point of each fiber on the yarn section; (2.3) adopt Delaunay triangulation algorithm and Alpha-shape algorithm adaptive acquisition step (2.2) in the boundary of yarn section interpolation point, obtain yarn section polygonal boundary profile; (2.4) Perform homogenization and interpolation on the section polygon in step (2.3) to obtain the vertices of the triangular patch, and then generate the surface triangular patch model of the yarn according to a specific order. 4. a kind of fabric composite finite element modeling method based on micro-geometry model as claimed in claim 1, is characterized in that: described step (3), specifically as follows: (3.1) Read the size of the representative volume unit of the fabric, and set the min and max key nodes of the composite material domain; (3.2) Set the appropriate hexahedral unit size according to the fiber size and cross-sectional parameters of the fabric, and uniformly discretize the material domain in step (3.1) into hexahedral units of corresponding size. 5. a kind of fabric composite material finite element modeling method based on micro-geometry model as claimed in claim 1, is characterized in that: described step (4), specifically as follows: (4.1) Map the triangular facet on the surface of the yarn into the composite material domain, calculate the surface intersection points of the triangular facet and the grid lines in the three directions of x, y and z, and record the topological information of the intersection; (4.2) Periodically map the grid line surface intersection points on the six-face boundary of the composite material domain, so that the grid line surface intersection points meet the periodic boundary conditions of the representative volume unit. 6. a kind of fabric composite material finite element modeling method based on micro-geometry model as claimed in claim 1, is characterized in that: described step (5), is specifically as follows: (5.1) respectively extracting the intersection points of yarns on the grid line surface in x, y and z directions and sorting them according to their x, y or z coordinate values; (5.2) According to the grid line intersection x, y or z value and its topological relationship, the intersection of two interpenetrating different yarn surfaces is adjusted to the midpoint of the two points, and the topological labels of the two nodes are exchanged at the same time; The intersection of two different yarn surfaces whose distance is less than the set threshold is adjusted to the midpoint of the two points. 7. a kind of fabric composite material finite element modeling method based on micro-geometry model as claimed in claim 1, is characterized in that: described step (6), specifically as follows: (6.1) read the adjusted grid line surface intersection in step (5), judge the adjacent grid node of the grid line surface intersection, and store the grid line surface intersection in the corresponding grid node adjacency linked list; (6.2) Traverse all grid nodes, if the grid node adjacency linked list is zero, then do not need to adjust the grid node, and set the label of the grid node to correspond to a single component label; otherwise, adjust the coordinates of the grid node to all adjacent surfaces At the midpoint of the intersection, set the grid node label to the corresponding multi-component label. 8. a kind of fabric composite material finite element modeling method based on micro-geometry model as claimed in claim 1, is characterized in that: described step (7), specifically as follows: Read the quadrilateral on the surface of the hexahedral unit corresponding to the four grid node labels, judge whether the quadrilateral needs to be divided into two triangles according to the number of labels and the type of the label, if necessary, add the adjacent nodes of the node. 9. a kind of fabric composite material finite element modeling method based on micro-geometry model as claimed in claim 1, is characterized in that: described step (8), is specifically as follows: (8.1) Read the adjacent points of the hexahedral unit nodes, divide the hexahedral unit into one component, two components or three components according to the node label, and split the corresponding components into tetrahedron, pyramid or Triangular prism unit; (8.2) Judgment unit set Each unit corresponds to the adjacent yarn path node in step (2), and the unit material direction is set as the path direction of the node. 10. A kind of fabric composite material finite element modeling method based on micro-geometry model as claimed in claim 9, is characterized in that: in described step (8.1), the mode of splitting group comprises, adds in hexahedron element interior Nodes are split.

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