A numerical prediction method for curing residual stress of braided composite materials

Abstract

The present invention discloses a method for numerically predicting residual stress of a braided composite material structure during curing, which belongs to the technical field of composite material structure manufacturing. The method comprises: constructing a braided fiber model based on the braided composite material structure, analyzing the braided fiber model by a finite element analysis method, wherein the braided fiber model is converted from a geometric model to a grid model, numerically simulating the grid model by a simulation model, and generating a field distribution result, wherein the simulation model comprises a curing kinetics model and a thermochemical model; simulating the field distribution result by a thermodynamic model, and generating a numerical distribution model of residual stress of the braided composite material structure during curing.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material structure manufacturing, and in particular relates to a numerical prediction method for curing residual stress of a braided composite material structure. Background Art

[0002] Composite materials are widely used in aerospace, automobile manufacturing, shipbuilding and other fields due to their superior specific strength, specific stiffness, fatigue properties and structural designability. In the current preparation process of composite materials, especially in the process involving woven composite materials, curing residual stress is often generated. These residual stresses may be caused by the non-uniformity of the material, the complexity of the thermal history and the deformation of the structure during the curing process. These residual stresses may cause deformation and cracking of the structure and reduce the mechanical properties of the material, thereby affecting the reliability and life of the entire structure.

[0003] The current prediction methods for residual stress of braided composite structures are mainly based on empirical formulas or simplified models, which have the problem of insufficient accuracy when dealing with complex structures and multi-material combinations. Therefore, there is an urgent need for an accurate and comprehensive method to predict residual stress of braided composite structures to meet the high requirements for structural performance during the manufacturing process.

[0004] In traditional methods, it is usually difficult to fully consider the multi-scale and multi-physics coupling of composite structures, resulting in uncertainty in the prediction results. In addition, the formation of curing residual stress involves complex factors such as the three-dimensional geometry of the structure, the special properties of the woven structure, and the temperature distribution during the curing process. The interaction of these factors makes the prediction more complicated. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a numerical prediction method for residual stress of braided composite material structure after curing, aiming to provide a prediction method for residual stress of braided composite material structure after curing based on numerical simulation. Through this method, the influence of multi-scale and multi-physical field coupling and the subtle changes of the structure during the curing process can be more accurately considered, and the distribution of residual stress can be more accurately simulated and predicted.

[0006] To achieve the above object, the present invention provides a method for numerically predicting residual stress of a braided composite material structure after curing, comprising:

[0007] Based on the woven composite material structure, a woven fiber model is constructed.

[0008] The woven fiber model is analyzed by a finite element analysis method, wherein the woven fiber model is converted from a geometric model to a mesh model, and the mesh model is numerically simulated by a simulation model to generate a field distribution result, wherein the simulation model includes a curing kinetics model and a thermochemical model;

[0009] The field distribution results are simulated by thermodynamic model to generate a numerical distribution model of residual stress during curing of braided composite material structure.

[0010] Optionally, the process of constructing the braided fiber model includes:

[0011] The geometric model is created using the TexGen tool, and the woven fiber model is generated by editing the geometric model.

[0012] Optionally, the thermochemical model is:

[0013] Construct a thermochemical model based on Fourier's heat conduction law and energy balance principle:

[0014] ;

[0015] in: is the density of the composite material, c is the specific heat of the composite material, is the performance parameter of the composite material; T is the absolute temperature of the composite material; are the thermal conductivity of the composite material along the x, y, and z directions, respectively; t For time; x , y , z are the thermal conductivity values ​​of the composite material along the x, y, and z directions respectively; It is the heat of generation of the internal heat source per unit volume per unit time.

[0016] Optionally, the heat of generation of the internal heat source per unit volume per unit time is:

[0017] ;

[0018] in: is the resin density; is the volume fraction of resin; is the total reaction heat of the resin; is the curing reaction rate of the resin.

[0019] Optionally, in the thermochemical model, a temperature boundary condition is set, wherein the temperature boundary condition is:

[0020] ;

[0021] Among them, on is a function given by the boundary condition, and the temperature boundary condition indicates that the absolute temperature T is at the temperature boundary. Equal to the preset absolute temperature .

[0022] Optionally, the performance parameters of the composite material are equivalently calculated according to the mixing ratio:

[0023]

[0024] in, is the fiber volume fraction, K c represents the volume fraction of the composite material, K r represents the resin volume fraction, Indicates resin density, represents the fiber density, c f represents the specific heat of resin, c r Indicates the specific heat of resin, subscript r Resin, subscript f Represents fiber, f represents the weighting coefficient of the fiber in the composite material, and c represents the specific heat capacity of the composite material.

[0025] Optionally, the curing kinetics model is

[0026]

[0027] Where: A is the frequency factor, is the activation energy, R is the universal gas constant, T is the absolute temperature of the composite material, α is the variable of the reaction progress, m and n are the order of the reaction, is a constant related to the slope of the reaction rate function, and is a constant related to temperature T.

[0028] Optionally, the process of analyzing the braided fiber model by finite element analysis method includes:

[0029] The mesh model conversion and numerical simulation calculation of the braided fiber model are performed by Abaqus finite element analysis software, wherein the Hetval subroutine is set according to the simulation model, and the mesh model is numerically simulated based on the Hetval subroutine.

[0030] Optionally, the process of generating the field distribution results includes:

[0031] According to the numerical simulation results, an ODB file is generated, and the ODB file is analyzed to generate field distribution results, wherein the field distribution results include mold surface temperature field, temperature field distribution and fixed degree field distribution.

[0032] Optionally, the process of simulating the field distribution results by means of a thermodynamic model includes:

[0033] The field distribution results are simulated and calculated based on the stress-strain constitutive model to generate simulation calculation results, which include residual stress, component springback deformation, interface and interlayer interaction, and a post-curing stress distribution model is generated based on the simulation calculation results.

[0034] Compared with the prior art, the present invention has the following advantages and technical effects:

[0035] The present invention relates to a method for numerically predicting residual stress of a braided composite material structure during curing, aiming to solve the problem of curing residual stress that is currently prevalent in the preparation process of composite material structures. The present invention adopts a method based on numerical simulation and uses a finite element model to comprehensively and accurately predict the braided composite material structure. The method comprehensively considers factors such as the three-dimensional geometric shape of the structure, the special properties of the braided structure, and the temperature distribution during the curing process, and can more accurately simulate the distribution of residual stress.

[0036] Compared with traditional methods, the advantage of this invention is that it can more comprehensively consider the effects of multi-scale and multi-physical field coupling, improve the accuracy and reliability of residual stress prediction of braided composite materials, and provide a more reliable basis for the optimal design and manufacturing of braided composite structures. This method will play an important role in the preparation and design of braided composite structures and provide advanced numerical tools for optimizing engineering practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0038] Figure 1 The present invention provides a specific flow chart for predicting the curing residual stress of a braided composite material structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0040] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0041] This embodiment provides a method for numerically predicting residual stress of a braided composite material structure after curing, which belongs to the technical field of composite material structure manufacturing. The steps are as follows:

[0042] 1) Use TexGen tool to draw complex woven fiber models to ensure the accuracy and detail of the model.

[0043] 2) The obtained woven fiber model is imported into the Abaqus finite element software, and the woven model is converted from a collection model to a mesh model through the finite element software. For the mesh model, the Hetvl model is used to perform numerical simulation calculations of the thermochemical model and the curing kinetics model.

[0044] 3) After the numerical simulation calculation is completed, an ODB file is generated. By analyzing the ODB file, the simulated field distribution results are obtained, and the residual stress field distribution is further solved.

[0045] 4) According to the field distribution results, based on the thermodynamic model, the stress-strain distribution is accurately solved.

[0046] The present invention relates to a method for numerically predicting residual stress of a braided composite material structure during curing, aiming to solve the problem of curing residual stress that is currently prevalent in the preparation process of composite material structures. The present invention adopts a method based on numerical simulation and uses a finite element model to comprehensively and accurately predict the braided composite material structure. The method comprehensively considers factors such as the three-dimensional geometric shape of the structure, the special properties of the braided structure, and the temperature distribution during the curing process, and can more accurately simulate the distribution of residual stress.

[0047] Compared with traditional methods, the advantage of this invention is that it can more comprehensively consider the effects of multi-scale and multi-physical field coupling, improving the accuracy and reliability of prediction. This method will play an important role in the preparation and design of woven composite structures and provide advanced numerical tools for optimizing engineering practice.

[0048] The main purpose of this invention is to propose a new method to predict the curing residual stress of braided composite material structure. That is, by using the process of mutual coupling between heat and chemical reaction, a mathematical model of the problem is established according to Fourier's heat conduction law and energy balance principle, and the Hetval subroutine is written to realize the prediction of curing residual stress of braided composite material structure in ABAQUS.

[0049] To elaborate on the above:

[0050] The technical solution adopted by the present invention is: a numerical prediction method for curing residual stress of a braided composite material structure, comprising the following steps:

[0051] The first step is to use the TexGen tool to draw a complex woven fiber model to ensure the accuracy and detail of the model.

[0052] In this step, use the TexGen tool to draw the braided fiber model. First, create a 2D weaving model. During the creation process, set the relevant parameters, Warp Yarns: 3, Weft Yarns: 3, Yarn Spacing: 1, Yarn Width: 0.749256, Fabric Thickness: 0.29, and set the create defaultdomain / add 10% to domain height / refine model / force in-plane tangents at nodes options to generate a geometric model.

[0053] Make relevant settings for the geometric model. After setting, select edit domain in the domain project to edit the unit cell geometric model.

[0054] In the edit field, set the vectors x: 1, -1, 0, 0, 0, 0; y: 0, 0, 1, -1, 0, 0; z: 0, 0, 0, 0, 1, -1; d: 0, -2, 0, -2, -0.0145, -0.3045 from top to bottom, and select create box to create the display model.

[0055] Set the display area options, Box domain: minimum: X: 0, Y: 0, Z: -0.0145; maximum: X: 2, : Y: 2, Z: 0.3045; generate and display the unit cell weaving model, that is, the weaving fiber model.

[0056] like Figure 1 As shown, in the second step, the obtained woven fiber model is imported into the Abaqus finite element analysis software, and meshed to generate a mesh model. The Hetval model is used to perform a thermochemical model numerical simulation calculation on the mesh model. The thermochemical model is as follows:

[0057] The curing process of solid resin-based composite materials is a process of coupled heat and chemical reaction. The mathematical model of the simulation calculation is established based on Fourier's heat conduction law and energy balance principle:

[0058]

[0059] in: is the density of the composite material, c is the specific heat of the composite material, is the parameter of the composite material density; T is the absolute temperature of the composite material; are the thermal conductivity of the composite material along the x, y, and z directions, respectively; t For time; x , y , z are the thermal conductivity time values ​​of the composite material along the x, y, and z directions respectively; is the heat of generation of the internal heat source per unit volume per unit time, determined by the following formula:

[0060]

[0061] in: is the resin density; is the volume fraction of resin; is the total reaction heat of the resin; is the curing reaction rate of the resin.

[0062] Since the resin is generally in a vacuum during the curing process, only temperature boundary conditions exist:

[0063]

[0064] The formula indicates that the absolute temperature T is at the temperature boundary. Equal to the preset absolute temperature , on is the function given by the boundary conditions.

[0065] The performance parameters of composite materials can be equivalently calculated according to the mixing ratio:

[0066]

[0067] Where: is the fiber volume fraction, K c represents the volume fraction of the composite material, K r represents the resin volume fraction, Indicates resin density, represents the fiber density, c f represents the specific heat of resin, c r Indicates the specific heat of resin, subscript r Resin, subscript f Represents fiber, frepresents the weighting coefficient of the fiber in the composite material, and c represents the specific heat capacity of the composite material.

[0068] The curing kinetics equation reflects the quantitative relationship between the resin curing rate, curing degree and temperature. It is usually described by a phenomenological model at the macroscopic level. The curing kinetics model is as follows:

[0069]

[0070] Where: A is the frequency factor; is the activation energy; R is the universal gas constant, T is the absolute temperature of the composite material, α is the variable of reaction progress, indicating the degree of conversion of a substance, m and n are the order of reaction, which determines the dependence of reaction progress on component concentration. is a regulating parameter, a constant related to the curing kinetics model, affecting the steepness or sensitivity of the exponential function. and is a constant related to temperature T.

[0071] Using the above formula, write the Hetval subroutine.

[0072] Step 3: After completing the numerical simulation calculation of the grid model based on the thermochemical model, generate the corresponding ODB file, including obtaining the simulated field distribution results by analyzing the ODB file. The field distribution results include the mold surface temperature field, the constructed temperature field distribution, and the component fixity field, and further solve the residual stress field distribution.

[0073] Step 4: According to the field distribution results, based on the thermodynamic model, accurately solve the stress-strain distribution. The thermodynamic model uses the stress-strain constitutive model, and simulates and calculates the residual stress, component rebound deformation, interface and interlayer interaction, and displays the corresponding model generation to generate a stress distribution model at a certain moment after curing. This content can be implemented according to the relevant content of "Numerical Simulation and Theoretical Research on Curing Deformation of Thermosetting Resin-based Composite Materials".

[0074] The beneficial effects of the present invention are:

[0075] The main purpose of the present invention is to propose a new method to predict the curing residual stress of a braided composite material structure. The present invention aims to provide a method for predicting the curing residual stress of a braided composite material structure based on numerical simulation, which can more accurately consider the influence of multi-scale and multi-physical field coupling, as well as the subtle changes of the structure during the curing process, and provide a more reliable basis for the optimal design and manufacture of the braided composite material structure.

[0076] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for numerically predicting residual stress of a braided composite material structure after curing, characterized in that: include: Based on the woven composite material structure, a woven fiber model is constructed. The woven fiber model is analyzed by a finite element analysis method, wherein the woven fiber model is converted from a geometric model to a mesh model, and the mesh model is numerically simulated by a simulation model to generate a field distribution result, wherein the simulation model includes a curing kinetics model and a thermochemical model; The field distribution results are simulated by thermodynamic model to generate the numerical distribution model of residual stress of braided composite material structure after curing; The thermochemical model is: Construct a thermochemical model based on Fourier's heat conduction law and energy balance principle: ； in: is the density of the composite material, c is the specific heat of the composite material, is the performance parameter of the composite material; T is the absolute temperature of the composite material; are the thermal conductivity coefficients of the composite material along the x, y, and z directions respectively; t is time; x, y, and z are the thermal conductivity values ​​of the composite material along the x, y, and z directions respectively; is the heat of generation of the internal heat source per unit volume per unit time; The heat of generation of the internal heat source per unit volume per unit time is: ； in: is the resin density; is the volume fraction of resin; is the total reaction heat of the resin; is the curing reaction rate of the resin; In the thermochemical model, a temperature boundary condition is set, wherein the temperature boundary condition is: ； Among them, on is a function given by the boundary condition, and the temperature boundary condition indicates that the absolute temperature T is at the temperature boundary. Equal to the preset absolute temperature ; The performance parameters of the composite material are equivalently calculated according to the mixing ratio: in, is the fiber volume fraction, K c represents the volume fraction of the composite material, K r represents the resin volume fraction, Indicates resin density, represents the fiber density, c f represents the specific heat of resin, c r represents the specific heat of resin, subscript r represents resin, subscript f represents fiber, f represents the weighting coefficient of fiber in the composite material, and c represents the specific heat capacity of the composite material; The curing kinetics model is Where: A is the frequency factor, is the activation energy, R is the universal gas constant, T is the absolute temperature of the composite material, α is the variable of the reaction progress, m and n are the order of the reaction, is a constant related to the slope of the reaction rate function, and is a constant related to temperature T.

2. The method according to claim 1, characterized in that: The construction process of the braided fiber model includes: The geometric model is created using the TexGen tool, and the woven fiber model is generated by editing the geometric model.

3. The method according to claim 1, characterized in that The process of analyzing the braided fiber model by finite element analysis method includes: The mesh model conversion and numerical simulation calculation of the braided fiber model are performed by Abaqus finite element analysis software, wherein the Hetval subroutine is set according to the simulation model, and the mesh model is numerically simulated based on the Hetval subroutine.

4. The method according to claim 3, characterized in that The process of generating field distribution results includes: According to the numerical simulation results, an ODB file is generated, and the ODB file is analyzed to generate field distribution results, wherein the field distribution results include mold surface temperature field, temperature field distribution and fixed degree field distribution.

5. The method according to claim 1, characterized in that The process of simulating the field distribution results through the thermodynamic model includes: The field distribution results are simulated and calculated based on the stress-strain constitutive model to generate simulation calculation results, which include residual stress, component springback deformation, interface and interlayer interaction, and a post-curing stress distribution model is generated based on the simulation calculation results.

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