A method for predicting deformation of a composite material after reaming after curing

Abstract

The application discloses a kind of composite material curing after re-perforation deformation prediction method, first use three-dimensional modeling software to establish the finite element model of not being perforated, and carry out mesh division;Adopt the method of complete thermal coupling, respectively through calculation to obtain temperature, curing rate, degree of cure, and stress result before demoulding;By converting the boundary condition of finite element model, through stress calculation method, the stress distribution result and displacement deformation result of finite element model after demoulding are recalculated, obtain the stress distribution result and displacement deformation result after demoulding;Then again mark the area needing to be perforated, and carry out stiffness reduction, release stress, realize the simulation to be perforated, through stress calculation method, the stress distribution result and displacement deformation result of finite element model after perforation are recalculated;Export the back result of component after perforation and the result before curing, with the aid of Geomagic Control software carries out high-precision fitting, obtains the final curing after perforation deformation result.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of finite element simulation of composite materials, and particularly to a method for predicting deformation of composite materials after curing and then drilling. BACKGROUND

[0002] Composite materials are materials formed by optimizing the combination of materials with different properties through advanced material preparation technology. It is composed of two or more materials with different properties through physical or chemical methods to form a material with new properties. In composite materials, one phase is the continuous phase, called the matrix; the other phase is the dispersed phase, called the reinforcing material. The dispersed phase is distributed in the form of an independent phase in the entire continuous phase, and there is an interface between the two phases.

[0003] Through curing deformation simulation, the deformation of composite materials under different process parameters (such as curing temperature, heating rate, pressure, etc.) can be predicted, so as to optimize the process parameters, reduce the deformation, and improve the product quality. Simulation before actual production can find potential deformation problems in advance, avoid waste and rework caused by unreasonable design or improper process, and reduce production cost. In the manufacturing of composite parts such as aircraft wings and fuselage structures, curing deformation simulation is widely used in optimization design and process to ensure the dimensional accuracy and performance reliability of the parts, reduce the structure weight, and improve the fuel efficiency and flight performance of the aircraft. For the structure of the aircraft fuselage, due to the existence of windows, the opening design is required in the manufacturing of the fuselage.

[0004] However, for the opening, whether to open first and then cure, or to cure first and then open, the prior art cannot accurately predict which method has smaller manufacturing deformation; in addition, since curing and then opening changes the stress distribution and deformation of the material, it is impossible to achieve a result similar to the test through simulation prediction. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a method for predicting deformation of composite materials after curing and then drilling. Based on the complete thermal coupling method, the dynamic equation required for curing deformation, thermal strain and mechanical strain, the processing of the demolding process, and the influence of the opening sequence of the first opening and the second opening are accurately grasped. For composite material components considering opening structure, the final manufacturing deformation is smaller, and the accuracy of the simulation prediction result can be effectively improved.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] A method for predicting deformation of composite materials after curing and then drilling, comprising the following steps:

[0008] Step 1, using three-dimensional modeling software to establish a finite element model without opening, then through mesh processing software for meshing, and then importing ABAQUS software to give material parameters to the finite element model without opening, setting the number of layers of the composite material, and setting the corresponding material direction of each layer;

[0009] Step 2, using the method of complete thermal coupling, setting the temperature during the curing process of the composite material through the curing process parameters, and calculating the temperature, curing rate, curing degree, and stress results before demolding respectively;

[0010] Step 3, by converting the boundary conditions of the finite element model, through the stress calculation method, the stress distribution results and displacement deformation results of the finite element model after demolding are recalculated, and the stress distribution results and displacement deformation results after demolding are obtained; Then mark the area that needs to be opened and reduce the stiffness, release the stress, realize the simulation of opening, and through the stress calculation method, the stress distribution results and displacement deformation results of the finite element model after opening are recalculated.

[0011] Step 4, export the results of the back of the member after opening and the results before curing, and use Geomagic Control software for high-precision fitting to obtain the final deformation results of the opening after curing.

[0012] As preferred, the meshing method is: through ANSA software to clean up the geometry and mesh of the model, and then output the inp file that ABAQUS can recognize.

[0013] As preferred, in step 2, the curing process parameters are: from room temperature to 70℃ at a rate of 2℃ / min, holding for 1 hour, then to 120℃ at a rate of 2℃ / min, holding for 1 hour, then to 180℃ at a rate of 2℃ / min, holding for 2 hours, and finally cooling to room temperature at a rate of 2℃ / min.

[0014] As preferred, in step 2, the curing process parameters and the curing kinetics equation are known, and the temperature, curing rate, and curing degree are calculated by the curing kinetics method.

[0015] As preferred, in step 2, the glass transition temperature is determined by testing, and the known related parameters are obtained, and finally the stress distribution results before demolding are calculated by the curing deformation mechanics model, and the related parameters include the stiffness matrix of the rubber state and the glass state, the effective strain vector, and the time of the glass transition point.

[0016] As preferred, in step 3, through the UMAT subroutine, the opening area is identified by using the element number, and when the element is in the hole area, it is marked by using the state variable.

[0017] As preferred, in step 3, when judging to reduce the stiffness of the marking unit, the glassy material parameter of the opening area is reduced to a minimum value, stress release is allowed, stress distribution is recalculated, and deletion is carried out in the post-processing module by checking the marking state.

[0018] As preferred, in step 4, by extracting the displacement results of the back surface layer of cells after opening and before curing from the ABAQUS calculation results, the results are saved as an obj file format, and then imported into the Geomagic Control software for high-precision fitting, the design model is set as a Reference object, the simulation result is set as a Test object, the best fitting alignment algorithm is adopted to move the simulation result to the design model, and the 3D comparison algorithm is adopted to generate the deformation result.

[0019] The present application has the following characteristics and beneficial effects:

[0020] The present application considers the complex process of composite material curing forming, uses the actually measured curing kinetics equation, considers the thermal strain and curing shrinkage in different directions, considers the sequence of opening and closing, realizes the opening treatment after demolding, accurately grasps the deformation amount influencing factor of the composite material after opening, provides an effective method for manufacturing the composite material considering opening, and reduces the deformation amount in the composite material manufacturing process. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A solidification-demolding-opening relationship flow chart in a composite material curing and then opening deformation prediction method provided by the present application.

[0022] Figure 2 A C-shaped member schematic diagram used in the embodiment of the present application.

[0023] Figure 3 An ABAQUS subprogram calling and opening relationship flow chart of the present application.

[0024] Figure 4 An opening area identification schematic diagram of the present application.

[0025] Figure 5 A displacement prediction result schematic diagram of the present application.

[0026] Figure 6 A high-precision fitting setting schematic diagram of the present application.

[0027] Figure 7 A final deformation result schematic diagram of the present application.

[0028] Figure 8 A material direction setting schematic diagram in the embodiment of the present application.

[0029] Figure 9 The test and simulation results of the present application are compared with the point position diagram. DETAILED DESCRIPTION

[0030] The present application will be described in detail below with specific examples. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that the examples in the present application and the features in the examples can be combined with each other without conflict.

[0031] A deformation prediction method for a composite material after curing and re-drilling, as shown in Figure 1 , includes the following steps:

[0032] Step 1, use three-dimensional modeling software to establish a finite element model without drilling, then perform meshing through mesh processing software, specifically, use ANSA software to perform geometry cleaning and mesh processing, then output an inp file that can be recognized by ABAQUS.

[0033] Then import the ABAQUS software to give the material parameters to the finite element model without drilling, set the number of layers of the composite material, and set the corresponding material direction of each layer;

[0034] It should be noted that the composite material is composed of fibers and resin, and the material direction refers to the orientation of the fibers; as shown in Figure 8 , the red line in the figure is the fiber direction, 1 is the 0 degree direction, 2 is 90 degrees, and 3 is the thickness direction.

[0035] In this embodiment, C-shaped components are taken as examples, as shown in the accompanying Figure 2 , use three-dimensional modeling software to establish the required model, then import the model into ANSA software, perform geometry cleaning and meshing, and then export the inp file; open the file through ABAQUS, set the relevant material parameters such as density, user-defined material, and user-defined field; perform layer division on the composite material, assign material properties to the model, and determine the material direction; use the complete thermal-mechanical coupling method, set the first analysis step as a temperature-displacement coupling analysis step, and the second and third analysis steps as static-general analysis steps, set the temperature, displacement, stress, etc. Field output request; set the corresponding boundary conditions in the load module; assign the element type in the mesh module as temperature-displacement coupling C3D8T element type.

[0036] Step 2, use the complete thermal-mechanical coupling method to set the temperature during the curing process of the composite material through the curing process parameters, and calculate the temperature, curing rate, curing degree, and stress results before demolding, respectively.

[0037] Specifically, the ABAQUS subroutine and the drilling relationship flowchart are as followsFigure 3 The curing process parameters are as follows: from room temperature to 70°C at a rate of 2°C / min, holding for 1 hour, then from 70°C to 120°C at a rate of 2°C / min, holding for 1 hour, then from 120°C to 180°C at a rate of 2°C / min, holding for 2 hours, and finally from 180°C to room temperature at a rate of 2°C / min, and the DISP subroutine is written.

[0038] In this embodiment, the curing degree field variable is defined by the USDFLD subroutine, and the heat inside the material is defined by the HETVAL subroutine, the curing degree and the curing rate are calculated, and the curing degree is updated, wherein the curing rate is as follows:

[0039]

[0040] wherein α is the curing degree, T is the temperature, is the curing rate;

[0041] Further, the glass transition temperature is determined by testing, and known related parameters are obtained, and finally the stress distribution result before demolding is calculated by the curing deformation mechanics model, and the related parameters include the stiffness matrix of the rubber state and the glass state, the effective strain vector, and the time of the glass transition point.

[0042] wherein the expression of the curing deformation mechanics model is as follows:

[0043]

[0044] wherein, are the stiffness matrix of the rubber state and the glass state respectively, σ i is the stress distribution result before demolding, is the effective strain vector, t vit is the time of the glass transition point, T g is the glass transition temperature; wherein the glass transition temperature is measured by testing and the result is as follows:

[0045]

[0046] The thermal strain and the curing shrinkage strain are calculated by the UEXPAN subroutine, and according to the change ΔT of the temperature of the incremental step, the thermal strain increment of the composite material can be calculated, which can be understood that the thermal strain increment is the change of the strain caused by the thermal expansion of the material due to the temperature change; the change of the strain will cause the change of the stress, which will affect the final stress result; the strain in the curing deformation mechanics model in step 2 is the total strain, which contains the thermal strain, i.e.

[0047]

[0048] wherein α iCte is the coefficient of thermal expansion; the coefficient of thermal expansion of the material is measured by a thermal mechanical analyzer (TMA) as follows:

[0049]

[0050] The coefficient of thermal expansion in the fiber direction is 0; the solidification shrinkage strain is measured by test, and the result in the direction perpendicular to the fiber direction is 0.45%.

[0051] The solidification temperature curve is defined by the DISP subroutine, the heat inside the material is defined by the HETVAL subroutine, the solidification degree and the solidification rate are calculated, the solidification degree is updated, the solidification degree field variable is defined by the USDFLD subroutine, the data is transmitted by the state variable STATEV and the user subroutine HETVAL, the thermal strain and the solidification shrinkage strain are calculated by the UEXPAN subroutine, and the material parameters related to temperature, the stiffness matrix, the mechanical strain, and the calculation of the total stress strain are defined by the UMAT subroutine.

[0052] It should be noted that the result before demolding is calculated by the solidification deformation mechanics model, part of the stress is released after demolding to obtain the solidification residual stress, and the stress is further released after the hole is opened to obtain the final solidification residual stress.

[0053] Step 3, by converting the boundary conditions of the finite element model, by the stress calculation method, the stress distribution result and the displacement deformation result of the finite element model after demolding are recalculated, the stress distribution result and the displacement deformation result after demolding are obtained; then the area to be opened is marked, and the stiffness is reduced to release the stress, realize the simulation of the opening, and by the stress calculation method, the stress distribution result and the displacement deformation result of the finite element model after opening are recalculated;

[0054] It should be noted that when considering the opening, the finite element model is not opened first and then simulated, but the finite element model without opening is used, the demolding process is considered after the solidification deformation simulation is finished, and then the opening is processed after demolding. Compared with the first opening, this method has smaller solidification deformation.

[0055] In this embodiment, the UMAT subroutine is used to identify the opening area by using the element number, the state variable is used to mark the element when it is judged to be in the hole area, and the stiffness reduction processing is performed, the stress is recalculated, and the marking result is shown in the attached Figure 4 The simulation method of the opening borrows the element degradation deletion technology used in the composite material failure analysis, then the stiffness of the marked element is reduced when it is judged in the third analysis step, the glass material parameters of the hole area are reduced to a very small value, the very small value is set to 0.001 in this embodiment, the stress is allowed to release, the stress distribution is recalculated, the marked element is deleted, the displacement result is shown in the attachedFigure 5 As shown.

[0056] Step 4: Export the results of the back side of the component after the hole is opened and the results before curing. Use Geomagic Control software to perform high-precision fitting to obtain the final result of the hole deformation after curing.

[0057] Specifically, by extracting the displacement results of the back layer of elements after the hole is opened and the displacement results before curing from the ABAQUS calculation results, the results are saved as an .obj file and then imported into Geomagic Control software for high-precision fitting. The design model is set as the Reference object, and the simulation results are set as the Test object. The best-fit alignment algorithm is used to bring the simulation results closer to the design model, and the deformation results are generated using a 3D comparison algorithm, as shown in the attached figure. Figure 7 As shown.

[0058] To further clarify the errors between simulation and experiment, see attached... Figure 9 Taking the model as an example, based on the structural characteristics of the model, eight feature points were selected in the back 1 / 4 region for deformation data comparison.

[0059] Table 1 shows the comparison results between simulation and experiment:

[0060]

[0061] As shown in Table 1, the error between simulation and experiment is very small, with a difference of no more than 0.2 mm. Therefore, predicting deformation problems in advance through simulation reduces trial and error, material waste, and shortens the product development cycle. Accurate deformation prediction helps improve product reliability and meet the stringent requirements of high-end fields for composite material performance. It has clear application value in high-end fields such as aerospace and automotive manufacturing, and can significantly improve the manufacturing precision and efficiency of composite material components. Although there are certain technical barriers and data dependence issues, its core advantages of optimizing processes and reducing costs through simulation make it promising for industrial production. With the continuous expansion of composite material applications, this method is expected to become one of the industry standard technologies.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for predicting deformation after curing and then opening pores in a composite material, characterized in that, Includes the following steps: Step 1: Use 3D modeling software to create a finite element model without holes, then use mesh processing software to generate a mesh, and then import it into ABAQUS software to assign material parameters to the finite element model without holes, set the number of layers of the composite material, and set the corresponding material orientation for each layer. Step 2: Using a fully thermo-mechanical coupling method, the temperature during the curing process of the composite material is set through curing process parameters, and the curing rate, degree of curing, and stress results before demolding are obtained by calculation. The calculation method is as follows: the glass transition temperature is determined by testing, and the known relevant parameters are obtained. Finally, the stress distribution before demolding is calculated by the curing deformation mechanics model. The relevant parameters include the stiffness matrix of the rubber state and the glass state, the effective strain vector, and the time of the glass transition point. Step 3: By transforming the boundary conditions of the finite element model, and using the stress calculation method, recalculate the stress distribution and displacement deformation results of the finite element model after demolding to obtain the stress distribution and displacement deformation results after demolding. Then, the areas that need to be opened are marked, and the stiffness is reduced to release the stress, thus simulating the opening. The stress distribution and displacement deformation results of the finite element model after the opening are recalculated using stress calculation methods. When it is determined that the stiffness of the marked unit is reduced, the glassy material parameters of the opening area are reduced to a minimum value to allow stress release, the stress distribution is recalculated, and then the marked status is checked and deleted in the post-processing module. Step 4: Export the results of the back side of the component after the hole is opened and the results before curing. Use Geomagic Control software to perform high-precision fitting to obtain the final result of the hole deformation after curing.

2. The deformation prediction method for composite materials after curing and then opening pores according to claim 1, characterized in that, The mesh generation method is as follows: the model is geometrically cleaned and meshed using ANSA software, and then an .inp file that can be recognized by ABAQUS is output.

3. The deformation prediction method for composite materials after curing and then opening pores according to claim 1, characterized in that, In step 2, the curing process parameters are as follows: heat up from room temperature to 70°C at a rate of 2°C / min, hold for 1 hour, then heat up to 120°C at a rate of 2°C / min, hold for 1 hour, then heat up to 180°C at a rate of 2°C / min, hold for 2 hours, and finally cool down to room temperature at a rate of 2°C / min.

4. The deformation prediction method for composite materials after curing and then opening pores according to claim 1, characterized in that, In step 2, given the curing process parameters and curing kinetic equations, the curing rate and degree of curing are calculated using curing kinetic methods.

5. The deformation prediction method for composite materials after curing and then opening pores according to claim 1, characterized in that, In step 3, the UMAT subroutine is used to identify the opening area using the unit number. When it is determined that the unit is in the opening area, a state variable is used to mark it.

6. The deformation prediction method for composite materials after curing and then opening pores according to claim 1, characterized in that, In step 4, the displacement results of the back layer unit after the hole is opened and the displacement results before curing are extracted from the ABAQUS calculation results. The results are saved as obj file format and then imported into Geomagic Control software for high-precision fitting. The design model is set as the Reference object and the simulation result is set as the Test object. The best fitting alignment algorithm is used to bring the simulation results closer to the design model and the 3D comparison algorithm is used to generate the deformation results.

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