Multi-scale numerical simulation method for carbon fiber woven cloth

Abstract

The invention relates to a carbon fiber woven cloth multi-scale numerical simulation method, which comprises the following steps of: generating a yarn micro-model, and performing a quasi-static tensile test on the yarn micro-model; weaving the yarn microscopic model to obtain a carbon fiber woven cloth microscopic model; performing a quasi-static tensile test on the carbon fiber woven cloth microscopic model; generating a macroscopic model of the carbon fiber woven cloth; and the like. According to the multi-scale numerical simulation method for the carbon fiber woven cloth, the material attributes of the yarns and the carbon fibers are provided through the micro model, the material attributes of representative units of the woven cloth are provided through the mesoscopic model, and the macroscopic model uses the result of mesoscopic homogenization for structural analysis.

Description

Technical Field

[0001] The present invention relates to the technical field of materials science, and particularly relates to a multi-scale numerical simulation method for carbon fiber woven fabrics. Background Art

[0002] During the existing carbon fiber simulation tests, in order to facilitate calculation and analysis, the microstructure of the carbon fiber woven fabric is simplified to a certain extent, usually with a unit cell model as the smallest unit. During actual use, the fiber filaments in the carbon fiber woven fabric may be subject to various damages and failures, such as fiber breakage, matrix cracking, fiber-matrix debonding, etc. Therefore, the models obtained by the current simulation methods cannot accurately reflect the true mechanical properties of the carbon fiber woven fabric. Summary of the Invention

[0003] The purpose of the present invention is to overcome the disadvantages of the traditional experimental methods, which are time-consuming, laborious, and difficult to comprehensively reveal the performance mechanism when analyzing the material characteristics and mechanism of carbon fiber woven fabrics, and to provide a multi-scale numerical simulation method for carbon fiber woven fabrics, so as to provide strong theoretical support for the research and application of carbon fiber woven fabrics.

[0004] To achieve the above purpose, the technical solution proposed by the present invention is: a multi-scale numerical simulation method for carbon fiber woven fabrics, including the following steps: Step 1: Set the diameter of the carbon fiber filaments and the content of the carbon fiber filaments in the yarn, and generate a microscopic model of the yarn; Step 2: Conduct a quasi-static tensile test on the microscopic model of the yarn to obtain the parameters of the microscopic model of the yarn; Step 3: Weave the microscopic model of the yarn to obtain a mesoscopic model of the carbon fiber woven fabric; Step 4: Conduct a quasi-static tensile test on the mesoscopic model of the carbon fiber woven fabric to obtain the parameters of the mesoscopic model of the carbon fiber woven fabric; Step 5: Generate a macroscopic model of the carbon fiber woven fabric, and substitute the parameters of the mesoscopic model of the fiber fabric to obtain a quasi-static tensile specimen of the carbon fiber woven fabric.

[0005] The further improvement of the above solution is that: in the above Step 1, the arrangement of the carbon fiber filaments in the yarn is honeycomb arrangement, grid arrangement or random arrangement; the carbon fiber filaments in the yarn and the epoxy resin are connected by co-nodes, and the epoxy resin is the matrix.

[0006] A further improvement of the above solution is as follows: In step 1, the random arrangement algorithm of carbon fiber filaments in the yarn is as follows. According to the set major axis a, minor axis b of the cross-section of the yarn, the diameter of the carbon fiber filaments, and the minimum distance between the carbon fiber filaments, arrange the carbon fiber filaments in sequence in the cross-section of the yarn, delete the carbon fiber filaments that exceed the boundary of the cross-section of the yarn to obtain the maximum number of fiber filaments, and then obtain the center point positions of each fiber filament. Randomly select several center point positions and generate carbon fiber filaments to obtain a microscopic model of the yarn with randomly arranged fiber filaments in the cross-section.

[0007] A further improvement of the above solution is as follows: In step 2, during the quasi-static tensile test of the yarn microscopic model, when the quasi-static tensile load is applied and damage occurs to the carbon fiber filaments, recalculate the local mechanical properties of the yarn and the matrix. One end of the carbon fiber filament is fixed and constrained, and the other end is stretched with a constant displacement. The average stretching speed is 2 mm / min, and periodic boundaries are set in other directions.

[0008] A further improvement of the above solution is as follows: In step 3, generate a plain woven carbon fiber fabric of a unit cell, and fill the voids with epoxy resin.

[0009] A further improvement of the above solution is as follows: In step 4, divide the mesh of the yarns in the microscopic model of the carbon fiber fabric, set periodic boundaries for the non-tensile boundaries, and adopt shared topology between the yarns and the epoxy resin. Use the mapped mesh technology to perform hexahedral mesh division on the microscopic model of the carbon fiber fabric, and the models share nodes. Assign the parameters of the yarn microscopic model to the yarns in the microscopic model of the carbon fiber fabric, and perform a quasi-static tensile test on the microscopic model of the carbon fiber fabric.

[0010] A further improvement of the above solution is as follows: In step 5, the end clamps of the quasi-static tensile specimen of the carbon fiber fabric are made of structural steel, and both the macroscopic model of the carbon fiber fabric and the model of the structural steel are divided into hexahedral meshes.

[0011] The multi-scale numerical simulation method of carbon fiber fabric provided by the present invention provides the material properties of the yarn and carbon fiber filaments through the microscopic model, provides the material properties of the representative unit of the fabric through the mesoscopic model, and uses the results of mesoscopic homogenization for structural analysis in the macroscopic model. Description of the Drawings

[0012] Figure 1 It is the strain nephogram of the tetrahedral mesh division of the yarn microscopic model in the embodiment of the present invention.

[0013] Figure 2 It is the strain nephogram of the hexahedral mesh division of the yarn microscopic model in the embodiment of the present invention.

[0014] Figure 3 It is a schematic diagram of the mesoscopic model of carbon fiber woven fabric in the embodiment of the present invention.

[0015] Figure 4 It is a schematic diagram of meshing the yarns in the mesoscopic model of carbon fiber woven fabric in the embodiment of the present invention.

[0016] Figure 5 It is a schematic diagram of meshing the mesoscopic model of carbon fiber woven fabric in the embodiment of the present invention.

[0017] Figure 6 It is the tensile strain nephogram of the mesoscopic model of carbon fiber woven fabric in the embodiment of the present invention.

[0018] Figure 7 It is a schematic diagram of the quasi-static tensile specimen of carbon fiber woven fabric in the embodiment of the present invention.

[0019] Figure 8 It is the finite element model of the quasi-static tensile specimen of carbon fiber woven fabric in the embodiment of the present invention.

[0020] Figure 9 It is the tensile strain nephogram of the quasi-static tensile specimen of carbon fiber woven fabric in the embodiment of the present invention.

[0021] Figure 10 It is the tensile strain nephogram of the quasi-static tensile specimen of carbon fiber woven fabric in actual testing. Specific embodiments

[0022] Embodiment: In this embodiment, a multi-scale numerical simulation method for carbon fiber woven fabric is proposed, including the following steps: Step 1: Set according to the diameter and content of carbon fiber filaments required by the final target model to generate a microscopic model of the yarn. The arrangement of carbon fiber filaments in the yarn is in a honeycomb arrangement, a grid arrangement or a random arrangement; the carbon fiber filaments and epoxy resin in the yarn are connected by co-nodes, and the epoxy resin is the matrix.

[0023] Generally speaking, in actual processing, the diameters of fiber filaments on the same woven fabric are the same. Through the scanning of the yarn cross-section by industrial CT, it can be clearly found that the distribution of fiber filaments in the yarn is not uniform. By reading a large number of documents, it is found that previous studies are basically based on uniform arrangement to model the fibers. However, compared with uniform arrangement, random arrangement is more in line with the actual situation.

[0024] The specific method for randomly arranging carbon fiber filaments in the yarn is as follows: The first step: Define the major axis a, minor axis b, diameter of carbon fiber filaments, and the minimum distance between carbon fiber filaments (to avoid carbon fiber filaments penetrating each other) respectively.

[0025] Step 2: Define and store the positions of the center points of each cross-section of the carbon fiber filaments, and at the same time detect the carbon fiber filaments and the ellipse boundary; judge whether the outer shell of the ellipse and the carbon fiber filaments are combined, and detect whether the carbon fiber filaments exceed the ellipse boundary. The stored points that exceed the boundary are automatically deleted, and the maximum number of carbon fiber filaments that can be contained is calculated.

[0026] Step 3: Randomly select from the set of stored coordinate points. Taking the selected coordinate points as the center, establish the cross-section of the yarn according to the set carbon fiber filament radius.

[0027] Step 4: Extend the length to the unit length of the yarn, and fill the middle of the carbon fiber filaments with epoxy resin.

[0028] For example, the parameters are set as follows: fiber diameter 15μm, major axis of the ellipse 1.992mm, minor axis of the ellipse 0.1335mm, minimum distance between fibers 0.005mm. After full-row calculation, the maximum number of fibers in the yarn is 891. 489 fibers are randomly selected, and one of the random models is calculated.

[0029] Step 2: Conduct a quasi-static tensile test on the microscopic model of the yarn to obtain the parameters of the microscopic model of the yarn. Use static analysis software to conduct a quasi-static tensile test on the microscopic model of the yarn. The carbon fiber filaments are made of high-strength modulus fiber filaments, and the material parameters of the carbon fiber filaments and epoxy resin are obtained by looking up tables.

[0030] During the quasi-static tensile test of the microscopic model of the yarn, when the quasi-static tensile load is applied and damage occurs to the carbon fiber filaments, recalculate the local mechanical properties of the yarn and the matrix; one end of the carbon fiber filaments is fixed and constrained, and the other end is stretched with a constant displacement. The average stretching speed is 2mm / min, and periodic boundaries are set in the other directions.

[0031] Apply a uniaxial tensile load to the microscopic model of the yarn and conduct stress-strain analysis. The strain nephograms of the representative elements with different mesh divisions are as Figure 1 and Figure 2 shown. It can be seen from the figure that when the UD model is meshed with hexahedrons, the maximum value of the strain is larger than that of the representative element of the UD model meshed with tetrahedrons. It is observed that the strain of the UD model with tetrahedron mesh division mainly occurs at the fiber filaments, and the strain value is about 0.0129; the strain of the UD model with hexahedron mesh division also mainly occurs at the fiber filaments, about 0.01175. Although the scales selected are different, it can also be seen that the strain values of the UD models with the two mesh divisions are almost the same.

[0032] Similarly, similar to the strain law of the yarn micro-model under different mesh division methods, when the yarn micro-model is divided into hexahedron meshes, the maximum stress is greater than that of the representative unit when the yarn micro-model is divided into tetrahedron finite elements; when divided into tetrahedron meshes, the stress of the yarn micro-model mainly occurs at the fiber filaments, and the stress is about 2.5646 MPa; when divided into hexahedron meshes, the strain of the yarn micro-model also mainly occurs at the fiber filaments, and the stress value is about 2.8012 MPa. It can be analyzed that the type of finite element unit has little influence on the stress value of the yarn micro-model.

[0033] Step 3: Weave the yarn micro-model to obtain a mesoscopic model of carbon fiber woven fabric.

[0034] In this step, that is, a 10 mm × 10 mm area is selected from the plain weave fiber composite material to construct a model to generate a unit cell of the plain weave carbon fiber woven fabric, and the voids are filled with epoxy resin, as Figure 3 shown.

[0035] Step 4: Conduct a quasi-static tensile test on the mesoscopic model of carbon fiber woven fabric to obtain the parameters of the mesoscopic model of carbon fiber woven fabric.

[0036] Mesh the yarns in the mesoscopic model of carbon fiber woven fabric, as Figure 4 shown. Set the periodic boundary for the non-tensile boundary, and adopt shared topology between the yarns and the epoxy resin; as Figure 5 shown, use the mapped mesh technology to divide the mesoscopic model of carbon fiber woven fabric into hexahedron meshes. The models share nodes with each other, and the transfer of stress and strain data is more accurate.

[0037] Assign the parameters of the yarn micro-model to the yarns in the mesoscopic model of carbon fiber woven fabric, and conduct a quasi-static tensile test on the mesoscopic model of carbon fiber woven fabric. Without damaging the fiber filaments, since shared nodes are used in the contact area, the yarns can be perfectly bonded to the epoxy resin matrix. The finite element mesh is composed of hexahedron elements. To ensure the accuracy of the model, the element mesh is a uniform mesh with a size of 0.1 mm.

[0038] Use a static analysis software to conduct a quasi-static tensile test on the mesoscopic model of carbon fiber woven fabric, and obtain the material parameters of the mesoscopic model of carbon fiber woven fabric through calculation. The strain nephogram obtained from the tensile test is as Figure 6 shown.

[0039] Step 5: Generate a macroscopic model of carbon fiber woven fabric, and substitute the parameters of the mesoscopic model of the fiber fabric to obtain a quasi-static tensile specimen of carbon fiber woven fabric, as Figure 7As shown in the figure. The clamping pieces at both ends of the quasi-static tensile specimen of carbon fiber woven fabric are made of structural steel, and their material parameters are obtained by looking up the table. When modeling, the clamping pieces and the fiber composite materials on both sides are connected with co-nodes.

[0040] The quasi-static tensile specimen of carbon fiber woven fabric is meshed to generate a finite element model of the quasi-static tensile specimen of carbon fiber woven fabric as shown in Figure 8 the figure. When meshing, in order to ensure the model quality and accuracy, a uniform mesh with a size of 0.006 mm is used. The number of nodes is 1,719,163 and the number of elements is 1,370,308, so the display degree of the model is relatively low. Zooming in on the local area can show the finite element model with structural steel clamping pieces on both sides of the fiber cloth. In actual fiber composite components, there is friction between the matrix material and the fiber material. Since it is very difficult to measure the friction coefficient, in order to simplify the model and reduce the calculation amount, in the macroscopic model of the fiber composite material, the contact between the matrix epoxy resin and the carbon fiber material is set as co-node contact. The finite element models of both the carbon fiber woven fabric and the structural steel adopt hexahedron meshing, and the mesh quality is high.

[0041] Finally, a static analysis software is used. One end of the single-layer specimen is fixed and the other end is stretched with a constant displacement. The displacement size is 4 mm. According to the loading speed of 2 mm / min in the quasi-static tensile test, the loading time is 2 min. The strain nephogram obtained from the tensile test is as shown in Figure 9 the figure.

[0042] As shown in Figure 10 the figure, when a physical object is used for the quasi-static tensile test of carbon fiber woven fabric, when the carbon fiber woven fabric bears the tensile load, the load is mainly borne by the gauge section in the middle. Under the same load condition, due to the large difference in the elastic modulus between the carbon fiber filaments and the epoxy resin, the carbon fiber filaments produce a greater degree of strain, which fully shows that the carbon fiber is the main supporting component in the woven fabric, and the load borne by the matrix is less than the load borne by the carbon fiber. Therefore, the epoxy resin is hidden and only the stress of the fiber material is analyzed.

[0043] In the quasi-static tensile simulation test of the quasi-static tensile specimen of carbon fiber woven fabric, the elastic modulus is calculated according to the average stress-strain value of the model. The average stress, average strain and elastic modulus of the model in the simulation test are summarized and compared with the actual test parameters. The elastic modulus value of the fiber cloth in the numerical simulation in this embodiment is 32,504 MPa, and the elastic modulus value of the fiber cloth in the actual test is 30,944.95 MPa. The difference between the two is small, and the correctness of the quasi-static tensile specimen of carbon fiber woven fabric in this embodiment is verified.

[0044] The present invention is not limited to the specific technical solutions described in the above embodiments. In addition to the above embodiments, the present invention may also have other implementation manners. For those skilled in the art, any technical solutions formed by making any modifications, equivalent replacements, improvements, etc. within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A multi-scale numerical simulation method for carbon fiber woven fabric, characterized in that: The steps include: Step 1: Set the diameter of the carbon fiber filaments and the carbon fiber filament content in the yarn to generate a yarn microscopic model; Step 2: Perform a quasi-static tensile test on the yarn micromodel to obtain the parameters of the yarn micromodel; Step 3: Weave the yarn microscopic model to obtain a carbon fiber woven cloth microscopic model; Step 4: Perform a quasi-static tensile test on the carbon fiber woven fabric micro-model to obtain the parameters of the carbon fiber woven fabric micro-model; Step 5: Generate a macroscopic model of the carbon fiber woven cloth, and substitute the parameters of the microscopic model of the fiber cloth into it to obtain a quasi-static tensile specimen of the carbon fiber woven cloth.

2. The multi-scale numerical simulation method of carbon fiber woven cloth according to claim 1, characterized in that: In the step 1, the carbon fiber filaments in the yarn are arranged in a honeycomb arrangement, a tic-tac-toe arrangement or a random arrangement; the carbon fiber filaments in the yarn and the epoxy resin are connected by a common node, and the epoxy resin is the matrix.

3. The multi-scale numerical simulation method of carbon fiber woven cloth according to claim 2, characterized in that: In the step 1, the random arrangement algorithm of the carbon fiber filaments in the yarn is as follows: according to the set major axis a, minor axis b, diameter of the carbon fiber filaments, and minimum distance between the carbon fiber filaments of the yarn cross section; the carbon fiber filaments are arranged sequentially in the cross section of the yarn, and the carbon fiber filaments beyond the boundary of the yarn cross section are deleted to obtain the maximum number of fiber filaments; and then the center point position of each fiber filament is obtained; a number of center point positions are randomly selected and carbon fiber filaments are generated to obtain a yarn microscopic model with randomly arranged fiber filaments in the cross section.

4. The multi-scale numerical simulation method of carbon fiber woven cloth according to claim 2, characterized in that: In the step 2, during the quasi-static tensile test of the yarn micromodel, when the quasi-static tensile load is applied, damage to the carbon fiber occurs, and the local mechanical properties of the yarn and the matrix are recalculated; one end of the carbon fiber is fixedly constrained and the other end is stretched with a constant displacement, the average stretching speed is 2 mm / min, and periodic boundaries are set in the remaining directions.

5. The multi-scale numerical simulation method of carbon fiber woven cloth according to claim 4, characterized in that: In the step 3, a plain woven carbon fiber woven cloth of a unit cell is generated, and the gaps are filled with epoxy resin.

6. The multi-scale numerical simulation method of carbon fiber woven cloth according to claim 5, characterized in that: In the step 4, the yarns in the carbon fiber woven cloth micro-model are meshed, the non-stretching boundaries are set with periodic boundaries, and the yarns and the epoxy resin are shared topology; the carbon fiber woven cloth micro-model is meshed with hexahedrons using the mapping grid technology, and the models share nodes; the parameters of the yarn micro-model are assigned to the yarns in the carbon fiber woven cloth micro-model, and the carbon fiber woven cloth micro-model is subjected to a quasi-static tensile test.

7. The multi-scale numerical simulation method of carbon fiber woven cloth according to claim 6, characterized in that: In the step 5, the two end clamps of the carbon fiber woven cloth quasi-static tensile test piece are made of structural steel, and the macro model of the carbon fiber woven cloth and the model of the structural steel are both divided by hexahedral meshes.

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