A multi-scale simulation method for complex structures of short fiber reinforced thermoplastic composites

Abstract

The present invention provides a multi-scale simulation method for complex structures of short fiber reinforced thermoplastic composites, belonging to the technical field of simulation of short fiber reinforced materials, including: S1. Material constitutive construction; S2. Finite element analysis of complex products of short fiber reinforced thermoplastic composites. The present invention provides a strength analysis method for short fiber reinforced thermoplastic composite products, which takes into account the material anisotropy caused by the injection molding process, constructs an accurate material constitutive model, and realizes finite element analysis, especially having general applicability to complex structures. Short fiber reinforced thermoplastic composites are affected by the molding process and exhibit anisotropic characteristics, which are difficult to accurately simulate in simulation. By using the method described in this patent, a relatively accurate material constitutive model can be obtained, and a complete strength analysis process can be established.

Description

Technical Field

[0001] The present invention relates to the technical field of short fiber reinforced material simulation, and particularly relates to a multi-scale simulation method for complex structures of short fiber reinforced thermoplastic composites. Background Art

[0002] Currently, the research on fiber reinforced composites has become a technically important issue internationally. Militarily, military equipment such as aircraft, rockets, artificial satellites, and ships are gradually being manufactured entirely from composites. Civilians, composites have played an important role in fields such as transportation vehicles, building structures, and medical instruments. Fiber composites are classified according to their structural forms into: single-layer composites, laminated composites, and short fiber composites. Short fiber composites are mainly applied in the automotive industry and can be used for the manufacture of structural parts; they can also be used for the manufacture of non-structural parts inside aircraft. Fibers endow products with good thermomechanical properties, and short fiber composites are also suitable for manufacturing devices close to heat sources. In addition, they are widely used in electrical and electronic and household appliances.

[0003] Different composites have different manufacturing methods. Injection molding is an important processing method for short fiber composites. During the injection molding process, the fibers flow in the mold cavity together with the matrix, causing the short fibers to have different orientations at different positions, so that the formed materials and products have different microstructures at different positions. During the molding process, the melt temperature, injection pressure, mold cavity shape, and processing process parameters will all affect the final state of the fibers. In addition, composites with different microstructures and mechanical properties can also be obtained by selecting and matching component materials. In order to better apply short glass fiber reinforced materials to life, the research on the mechanical properties of short glass fiber reinforced materials has become increasingly important.

[0004] The current main research methods for short fiber reinforced products are mainly divided into the following three methods: (1) Short fiber reinforced products are generally injection molded. Moldflow comprehensively considers the flow process of the matrix and its resulting effects during the injection molding process. Therefore, various analyses such as filling, holding pressure, cooling, warping, and fiber orientation can be carried out in Moldflow. (2) Combining Abaqus and Moldflow software for mold flow analysis and structural analysis. Since the structural analysis of injection molded products cannot rely on general injection molding CAE, other excellent structural analysis software is required. Abaqus has long been recognized as the most powerful general-purpose excellent finite element in the industry, and Abaqus has a direct interface with Moldflow. Therefore, mold flow analysis and structural analysis can be directly carried out by combining Abaqus and Moldflow software, which has also become an effective means to predict and verify the mechanical properties of short fiber reinforced composites. (3) Combining Abaqus, Digimat, and Moldflow software for mold flow analysis and structural analysis. First, use Moldflow to obtain the fiber distribution and direction information in the structure; then use Digimat to realize the mapping of fiber direction data; finally, use Abaqus for finite element analysis of the structure. However, there are some problems with the current three methods: For the first method, since Moldflow is not a professional structural analysis software, only some simple structural analyses can be carried out for simple models through Moldflow, and sometimes the analysis results desired by researchers cannot be obtained; for the second method, combining Abaqus and Moldflow software for mold flow analysis and structural analysis, although it can perform structural analysis on complex structures compared to the first method, applying this method requires a complete match of the software versions of Abaqus and Moldflow, which is relatively demanding on the user's hardware. Moreover, this mapping method has strict requirements for the mesh of the analysis model, with low flexibility. For complex structural parts, the mapping success rate is not high, and there is no correlation between the material properties used in the forming analysis and the structural analysis, resulting in low analysis accuracy; for the third method, a material mesoscopic constitutive model is constructed with the help of the third-party software Digimat, and the material constitutive is directly inferred based on the two phases contained in the material. The mechanical properties of the actually processed materials are not consistent with the predicted results, and it is not accurate to bring the predicted constitutive model into the structure for structural analysis.

[0005] Patent CN106250648B: A Structural Analysis Method for Glass Fiber Reinforced Materials Based on Abaqus and Moldflow Simulations. This patent introduces an analysis method for glass fiber reinforced materials using combined simulations of Abaqus and Moldflow. Specifically, it maps the fiber orientation information obtained from Moldflow to the structural analysis mesh in Abaqus by running scripts. The advantage of this method is that it can flexibly and quickly complete the information transfer between the two software without relying on third - party software. However, it does not explain how to set material parameters in Abaqus to obtain an accurate material constitutive model. Summary of the Invention

[0006] The object of the present invention is to propose a multi - scale simulation method for complex structures of short - fiber reinforced thermoplastic composites. Considering the material anisotropy caused by the injection molding process, an accurate material constitutive model is constructed and finite - element analysis is realized, which is generally applicable to complex structures. Short - fiber reinforced thermoplastic composites are affected by the molding process and exhibit anisotropic characteristics, making it difficult to accurately simulate in simulations. By using the method described in this patent, a relatively accurate material constitutive model can be obtained and a complete strength analysis process can be established.

[0007] The technical solution of the present invention is realized as follows:

[0008] The present invention provides a multi - scale simulation method for complex structures of short - fiber reinforced thermoplastic composites, including: S1. Material constitutive construction; S2. Finite - element analysis of complex products of short - fiber reinforced thermoplastic composites.

[0009] As a further improvement of the present invention, it specifically includes the following steps:

[0010] S1. Material constitutive construction:

[0011] S101. The width of the gate is close to the width of the sample, and the thickness of the gate is greater than the thickness of the sample.

[0012] S102. The thickness of the connection part between the gate and the sample is less than the thickness of the sample.

[0013] S103. The sample size ensures that splines with different fiber directions can be intercepted.

[0014] S104. Tensile and strain measurements are carried out on splines with different fiber orientations.

[0015] S105. A material mesoscopic model is constructed in Digimat software.

[0016] S106. Conduct material reverse engineering in Digimat MX by performing reverse engineering on the test curves tested in S104 and the curves obtained from the mesoscopic model analysis in S105, modifying the matrix material parameters set in S105 to obtain the material model after reverse engineering;

[0017] S2. Finite element analysis of complex products of short fiber reinforced thermoplastic composites:

[0018] S201. Perform injection molding process analysis on the actual product using molding process analysis software to obtain the fiber orientation distribution of the actual product and output it in a format recognizable by Digimat;

[0019] S202. Mesh the actual product using strength analysis software;

[0020] S203. In the MAP module of Digimat software, map the fiber orientation based on the molding analysis mesh information obtained in S201 to the mesh based on the strength analysis in S202 to obtain the mapped fiber orientation file;

[0021] S204. In the finite element model of S202, import the material model after reverse engineering obtained in S106 and the mapped fiber orientation file obtained in S203, and apply boundary conditions for finite element analysis.

[0022] As a further improvement of the present invention, in step S103, the 0° direction is the material flow direction, and templates with different 0° directions are designed as needed, and at least 3 direction splines are intercepted.

[0023] As a further improvement of the present invention, in step S1041, the tensile test is measured on an electronic universal material testing machine; the strain test is measured on an extensometer.

[0024] As a further improvement of the present invention, in step S201, the molding process analysis software is selected from at least one of general injection molding analysis software such as Moldflow and Moldex3D.

[0025] As a further improvement of the present invention, in step S204, the strength analysis software is at least one of general structural analysis software such as Abaqus and Ansys.

[0026] As a further improvement of the present invention, it specifically includes the following steps:

[0027] (1) By performing tensile tests on at least 3 splines with different fiber directions, respectively obtain their stress-strain curves and save them as file A;

[0028] (2) In the Digimat MF module, set the reinforced phase material and the matrix phase material, select the corresponding model for testing, and save it as File B.

[0029] (3) In the Digimat MX module, import File A and File B, perform material reverse engineering, correct the parameters of the matrix material to ensure that the analysis curve coincides with the test curve at the corresponding angles, and save it as File C.

[0030] (4) Conduct forming process analysis and calculation on the actual product, and output the mesh file D and the fiber orientation file E;

[0031] (5) Perform finite element mesh division on the actual product and save it as File F.

[0032] (6) In the Digimat Map module, import File D, File E, and File F for mapping, map the fiber information based on the forming analysis mesh to the structure analysis mesh, and output the mapped fiber orientation file, which is saved as File G.

[0033] (7) Based on File F, apply boundary conditions and load conditions, import the material constitutive model file C after reverse engineering and the mapped fiber orientation file G, and perform finite element analysis and solution.

[0034] The present invention has the following beneficial effects: The present invention proposes a method for analyzing the strength of short fiber reinforced thermoplastic composite products, which considers the material anisotropy caused by the injection molding process, constructs an accurate material constitutive model, and realizes finite element analysis, especially for complex structures, it has general applicability. Short fiber reinforced thermoplastic composites are affected by the forming process and exhibit anisotropic characteristics, which are difficult to accurately simulate in simulation. By using the method described in this patent, a relatively accurate material constitutive model can be obtained, and a complete strength analysis process can be established. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1 It is the analysis flow chart of the multi-scale simulation method for the complex structure of the short fiber reinforced thermoplastic composite material of the present invention;

[0037] Figure 2 It is Gate Scheme 1 in Embodiment 1;

[0038] Figure 3It is the gate solution 2 in Example 1;

[0039] Figure 4 It is the sectional view in the thickness direction of the sample in Example 1;

[0040] Figure 5 It is the spline with 0° fiber direction;

[0041] Figure 6 It is the spline with 30° fiber direction;

[0042] Figure 7 It is the spline with 45° fiber direction;

[0043] Figure 8 It is the spline with 90° fiber direction;

[0044] Among them, 1 is the gate; 2 is the connection part between the gate and the sample; 3 is the sample. Specific implementation mode

[0045] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0046] The analysis process of the multi-scale simulation method for the complex structure of the short fiber reinforced thermoplastic composite material of the present invention is as Figure 1 shown. The specific method is as follows:

[0047] S1. Material constitutive construction:

[0048] The gate solution is as Figure 2 , 3 .

[0049] S101. The width of the gate is close to the width of the sample, and the thickness of the gate is greater than the thickness of the sample;

[0050] S102. The thickness of the connection part between the gate and the sample is less than the thickness of the sample; as Figure 4 .

[0051] S103. The size of the sample ensures that splines with different fiber directions are intercepted.

[0052] S104. Tensile and strain measurements are carried out on the splines with different fiber orientations;

[0053] S105. Build a material mesoscopic model in Digimat software;

[0054] S106. Conduct material reverse engineering in Digimat MX. By performing reverse engineering on the test curves tested in S104 and the curves obtained from the mesoscopic model analysis in S105, correct the matrix material parameters set in S105 to obtain the material model after reverse engineering;

[0055] S2. Finite element analysis of complex products of short fiber reinforced thermoplastic composites:

[0056] S201. Use molding process analysis software to perform injection molding process analysis on the actual product, obtain the fiber orientation distribution of the actual product, and output it in a format recognizable by Digimat;

[0057] S202. Perform mesh generation on the actual product using strength analysis software;

[0058] S203. In the MAP module of Digimat software, map the fiber orientation based on the molding analysis mesh information obtained in S201 to the mesh based on the strength analysis in S202 to obtain the mapped fiber orientation file;

[0059] S204. In the finite element model of S202, import the material model after reverse engineering obtained in S106 and the mapped fiber orientation file obtained in S203, and apply boundary conditions for finite element analysis.

[0060] Example 1

[0061] Specifically, it includes the following steps:

[0062] 1. By conducting tensile tests on splines with different fiber directions, obtain the stress-strain curves of 0°, 30°, 45°, and 90° respectively. The splines with 0°, 30°, 45°, and 90° fiber directions are as Figures 5 - 8 shown and saved as test.xml;

[0063] 2. In the Digimat MF module, set the reinforcing phase material as glass fiber, select the elastic model for the material model, and set the elastic modulus, Poisson's ratio, aspect ratio, and volume fraction. The matrix phase material is nylon, select the elastic-plastic model for the material model, and set the elastic modulus, Poisson's ratio, yield strength, hardening modulus, and hardening index, and save it as the material1.daf file.

[0064] 3. In the Digimat MX module, import the material.daf file and the test.xml file (ensure that curves in at least two directions are input), perform material reverse engineering, correct the parameters of the matrix material, and ensure that the analysis curve coincides with the test curve at the corresponding angle. During the reverse engineering operation, first correct the elastic section to obtain the corrected elastic modulus and Poisson's ratio of the matrix material, then correct the plastic section to obtain the corrected hardening modulus, hardening index, and yield strength of the matrix material, and save it as a new material2.daf file.

[0065] 4. Perform forming process analysis and calculation on the actual product, and output the mesh file process.pat and the fiber orientation file fiber.xml;

[0066] 5. Perform finite element mesh division on the actual product and save it as the stresss.inp file.

[0067] 6. In the Digimat Map module, import the process.pat, fiber.xml, and stresss.inp files for mapping, map the fiber information based on the forming analysis mesh to the structure analysis mesh, output the mapped fiber orientation file, and save it as fiber new.xml.

[0068] 7. Based on the stress.inp file, apply boundary conditions and load conditions, import the material constitutive model material2.daf after reverse engineering and the mapped fiber orientation file fiber new.xml file, and perform finite element analysis and solution.

[0069] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made 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 simulation method for complex structures of short fiber reinforced thermoplastic composites, characterized in that Specifically, it includes the following steps: S1. Material constitutive model construction: S101. The width of the gate is close to the width of the sample, and the thickness of the gate is greater than the thickness of the sample. S102. The thickness of the connecting part between the gate and the sample is less than the thickness of the sample. S103. The sample size ensures that splines with different fiber directions are intercepted. S104. Tensile and strain measurements are carried out on the splines with different fiber orientations. S105. A mesoscopic model of the material is constructed in Digimat software. S106. In Digimat MX, material reverse engineering is carried out. By reverse engineering the test curve in S104 and the curve obtained from the mesoscopic model analysis in S105, the matrix material parameters set in S105 are corrected to obtain the material model after reverse engineering. S2. Finite element analysis of complex products of short fiber reinforced thermoplastic composites: S201. The injection molding process of the actual product is analyzed using molding process analysis software to obtain the fiber orientation distribution of the actual product and output it in a format recognizable by Digimat. S202. Mesh generation is carried out on the actual product using strength analysis software. S203. In the MAP module of Digimat software, the fiber orientation based on the molding analysis mesh information obtained in S201 is mapped into the mesh based on the strength analysis in S202 to obtain the mapped fiber orientation file. S204. In the finite element model of S202, the reverse engineered material model obtained in S106 and the mapped fiber orientation file obtained in S203 are imported, and boundary conditions are applied for finite element analysis.

2. The multi-scale simulation method for the complex structure of the short fiber reinforced thermoplastic composite material according to claim 1, characterized in that In step S103, the 0° direction is the material flow direction. Samples with different 0° directions are designed as needed, and splines in at least 3 directions are intercepted.

3. The multi-scale simulation method for the complex structure of the short fiber reinforced thermoplastic composite material according to claim 1, characterized in that, In step S104, the tensile test is measured on an electronic universal material testing machine; the strain test is measured on an extensometer.

4. The multi-scale simulation method for the complex structure of the short fiber reinforced thermoplastic composite material according to claim 1, wherein, In step S201, the molding process analysis software is selected from at least one of Moldflow and Moldex3D general injection molding analysis software.

5. The multi-scale simulation method for the complex structure of the short fiber reinforced thermoplastic composite material according to claim 1, wherein In step S204, the strength analysis software is at least one of Abaqus and Ansys general structural analysis software.

6. The multi-scale simulation method for a complex structure of a short fiber reinforced thermoplastic composite according to claim 1, wherein Specifically, it includes the following steps: (1) By conducting tensile tests on splines with at least 3 different fiber directions, their stress-strain curves are obtained respectively and saved as file A. (2) In the Digimat MF module, the reinforcing phase material and the matrix phase material are set, and the corresponding model is selected for testing and saved as file B. (3) In the Digimat MX module, file A and file B are imported, material reverse engineering is carried out, and the parameters of the matrix material are corrected to ensure that the analysis curve coincides with the test curve at the corresponding angle, and saved as file C. (4) The molding process analysis calculation is carried out on the actual product, and the mesh file D and the fiber orientation file E are output. (5) Finite element mesh generation is carried out on the actual product and saved as file F. (6) In the Digimat Map module, import files D, E, and F for mapping, map the fiber information based on the forming analysis mesh to the structure analysis mesh, and output the mapped fiber orientation file, which is saved as file G. (7) Based on file F, apply boundary conditions and load conditions, import the material constitutive model file C after reverse engineering and the mapped fiber orientation file G, and perform finite element analysis and solution.

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