A method and system for predicting defects in the curing molding of composite materials considering the flow compaction process

Abstract

The application discloses a composite curing forming defect prediction method and system considering a flow compaction process, and relates to the technical field of composite curing forming simulation prediction. The method comprises the following steps: a data acquisition step; a data preprocessing step; a curing degree field acquisition step; and a corresponding parameter acquisition step. The system comprises the following modules which are connected in sequence: a thermal-chemical coupling temperature field calculation module, a time-varying performance calculation module of each component material, a thermal-mechanical coupling stress field calculation and flow-compaction calculation module. On the basis of existing research, the resin flow and the fiber bed compaction characteristics are considered, and the accurate prediction of the two forming defects, i.e., the thickness out-of-tolerance and the uneven resin content, generated after the curing forming of the composite structural part is realized.

Description

Technical Field

[0001] This invention relates to the field of composite material curing and molding simulation and prediction technology, and in particular to a method and system for predicting composite material curing and molding defects that takes into account the flow and compaction process. Background Technology

[0002] Advanced resin-based composite materials are widely used in structural components in aerospace, transportation, and energy fields due to their superior properties such as high specific strength, specific stiffness, and design flexibility. Autoclave curing is one of the key manufacturing methods for producing high-quality composite structural components. However, during the curing process, the inherent thermodynamic property mismatch between the component materials, the internal temperature gradient of the structural part, and the differences in the coefficients of thermal expansion between the material molds are key factors affecting the mechanical properties of composite materials. These factors can lead to problems such as wrinkling, delamination, uneven thickness, and uneven resin content, seriously affecting manufacturing accuracy. Especially for complex molded parts, there are significant deviations from the actual design dimensions and requirements, thus affecting the overall structural load-bearing capacity and assembly accuracy.

[0003] Traditional trial-and-error methods are costly and inefficient in effectively addressing these problems. Given that numerical techniques are currently a mature and cost-effective approach, they play a crucial role in understanding the curing reaction mechanisms within autoclaves and assessing influencing factors to obtain high-quality results. The curing process of composite materials involves complex phenomena such as thermo-chemical-mechanical multi-field coupling processes, resin flow, and fiber compaction. Resin flow is a key factor affecting fiber volume fraction and thermodynamic properties, ultimately influencing the true thickness of structural components. Furthermore, fiber compaction significantly impacts the effective impregnation efficiency and residual stress distribution of composite parts. Therefore, accurately characterizing the multi-field coupling and flow compaction processes during curing, and using numerical simulation methods to predict molding defects, are crucial for the accurate subsequent evaluation of the mechanical properties of composite structural components.

[0004] Therefore, proposing a method and system for predicting defects in the curing and molding of composite materials that considers the flow and compaction process to solve the difficulties existing in the prior art is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method and system for predicting defects in the curing and molding of composite materials that takes into account the flow compaction process, so as to achieve accurate prediction of two molding defects: thickness deviation and resin content inconsistency that occur after the composite material structural parts are molded.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for predicting defects in the curing and molding of composite materials that considers the flow compaction process includes the following steps:

[0008] S1. Data acquisition steps: Obtain the geometric dimensions of the composite material structural component and the temperature and load conditions during the actual curing process;

[0009] S2. Data preprocessing steps: Based on the geometric dimension data, temperature data and load condition data obtained in S1, establish a multi-field coupled finite element simulation model of the composite material structure considering the flow compaction process.

[0010] S3. Curing degree field acquisition steps: Based on the thermo-chemical coupling temperature field calculation model, the heat transfer module is used to calculate the temperature field change in the time domain during the curing process, and the result of the temperature field change is used as the input of the mathematical module to calculate the curing rate under each incremental step through the set curing kinetic equation, thereby obtaining the corresponding curing degree field.

[0011] S4. Corresponding parameter acquisition steps: Based on the time-varying characteristics of the composite material curing process and the curing degree field obtained in S4, calculate the thermodynamic performance parameters of the composite material and each component material in the composite material during the curing process, and obtain the relevant parameters corresponding to each incremental step, i.e. each degree of curing, including: coefficient of thermal expansion, resin viscosity and permeability.

[0012] S5. Prediction Steps: Based on the thermo-mechanical coupled stress field calculation model and the flow-compaction model, using the time-varying parameters of each component material as input, calculate the thermal expansion strain and curing shrinkage strain to obtain variables related to curing defects, including: residual stress field, thickness variation, and fiber volume fraction; and use the fiber volume fraction as the parameter input for the time-varying characteristic calculation in S3, iterate cyclically, and predict the molding defects, including: curing residual stress, thickness deviation, and uneven glue content.

[0013] The above methods, optionally, all utilize the COMSOL platform to construct the multi-field coupled finite element simulation model of the composite material structure considering the flow compaction process in S2.

[0014] The above method, optionally, includes a heat conduction model and a curing kinetics model in S3 specifically for the thermo-chemical coupling temperature field model;

[0015] The heat conduction model is based on the heat conduction equation coupled with the exothermic curing term:

[0016]

[0017] Where K xx K yy and K zz These are the thermal conductivity coefficients of the material along each direction, T is the curing reaction temperature in the current time and space domains, and ρ is the thermal conductivity coefficient of the material along each direction. c and C c These are the density and specific heat capacity of the composite material, respectively. This represents the exothermic internal term of the resin during the curing reaction.

[0018] Optionally, the specific details of calculating the thermodynamic property parameters of the composite material in S4 of the above method include:

[0019] Based on the mixing law, the curing degree field obtained in S3 and the mechanical property parameters of the initial resin, fiber and fiber bed are calculated to obtain the physical state of the resin during the curing process. Furthermore, the thermodynamic property parameters of the composite material and its components are calculated based on the physical state of the resin during the curing process.

[0020] The mixing law based on volume fraction is used to calculate the mechanical property parameters of composite materials, as shown in the following formula:

[0021] ρ c =V f ρ f +V m ρ m

[0022] C c =V f C f +V m C m

[0023] Where c represents composite material, f represents fiber, and m represents resin, and V, ρ, and C represent volume fraction, density, and specific heat capacity, respectively;

[0024] Based on the mixing law of the curing process, the expression for the resin modulus Poisson's ratio is calculated, and the physical state of the resin during the curing process is obtained. The expression for the resin modulus Poisson's ratio is as follows:

[0025]

[0026] Among them, E m v m and G m These represent the elastic modulus, Poisson's ratio, and shear modulus of the resin at the current increment step, respectively. and α represents the elastic modulus of the resin at the beginning and end of curing, respectively. gel α represents the degree of curing at the gel point. mod It is a function of curing degree and gel point.

[0027] Optionally, in the above method, the effective thermal expansion coefficient of the composite material is calculated in S4, with the following expression:

[0028]

[0029] β2=β3=(β 2f +v12f β 1f V f +(β m +v m β m (1-V) f )-[v 12f V f +v m (1-V f )]β1

[0030] Where, β i (i = 1, 2, 3) represents the coefficient of thermal expansion, and the subscripts f and m represent fiber and resin, respectively;

[0031] Permeability exhibits significant anisotropy, expressed based on the Kozeny-Carman equation, as follows:

[0032]

[0033] Among them, S ii (i = x, y, z) represents the fiber bed permeability, r f V represents the fiber diameter. a denoted by k1 and k3, which represent the maximum volume fraction of the fiber. k1 and k3 are Kozeny constants.

[0034] Optionally, the thermo-mechanical coupled stress field model in S5, as described above, is based on the stress-strain relationship and is expressed as follows:

[0035] σ=Cε

[0036] ε=ε e +ε th +ε sh

[0037] Where σ represents curing stress, C represents the composite material stiffness matrix, and ε represents curing strain. e ε th and ε sh These represent elastic strain, thermal expansion strain, and curing shrinkage strain, respectively.

[0038] Optionally, the thermal expansion strain and curing shrinkage strain in S5 are calculated as follows using the above method:

[0039] (1) Calculate the curing shrinkage strain of the composite material, as shown in the following expression:

[0040]

[0041] in, This represents the coefficient of thermal expansion, with subscripts f and m indicating fiber and resin, respectively.

[0042] (2) Thermal expansion strain, the expression is as follows:

[0043] ε th =βΔT

[0044] The thermal expansion strain ε at the corresponding moment is obtained by multiplying the coefficient of thermal expansion β and the temperature difference ΔT. th .

[0045] Optionally, the flow-compaction model in S5, constructed based on mass conservation, resin flow continuity, and Darcy's law, is expressed as follows:

[0046]

[0047] P a =P+σ f

[0048] Where S ii (i = x, y, z) Fiber bed permeability, μ represents resin viscosity, P represents resin pressure, ε v σ represents volumetric strain. f P represents the effective stress of the fiber. a This indicates the application of an external load.

[0049] A composite material curing and molding defect prediction system considering the flow and compaction process, applying any of the above-mentioned composite material curing and molding defect prediction methods considering the flow and compaction process, includes the following modules connected in sequence: a thermo-chemical coupling temperature field calculation module, a time-varying property calculation module for each component material, a thermo-mechanical coupling stress field calculation module, and a flow and compaction calculation module;

[0050] Among them, the thermo-chemical coupling temperature field calculation module is used to obtain the temperature field, curing rate and degree of curing field during the curing process of composite materials;

[0051] The time-varying property calculation module for each component material is used to obtain the mechanical property parameters of the composite material and each component material during the curing process;

[0052] Thermo-mechanical coupling stress field calculation and flow-compaction calculation modules are used to obtain molding defects including non-uniform curing residual stress field, non-uniform adhesive content and thickness deviation.

[0053] As can be seen from the above technical solution, compared with the prior art, the present invention, a method and system for predicting defects in the curing and molding of composite materials considering the flow compaction process, has the following beneficial effects:

[0054] Based on existing research, this invention takes into account the flow and compaction characteristics of resin and establishes a three-dimensional model. By refining the curing and molding process, a finite element calculation method for the curing and molding of composite material structural parts is systematically constructed. This method can accurately predict the molding defects of composite material structural parts and has important guiding significance for reasonably reducing the generation of molding defects and preparing high-performance composite material complex structural parts. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0056] Figure 1 A flowchart of a composite material curing and molding defect prediction method considering the flow compaction process provided by the present invention;

[0057] Figure 2 This is a schematic diagram of the finite element mesh generation and boundary conditions for the L-shaped component provided by the present invention;

[0058] Figure 3 Curing process curve of the L-shaped part under high temperature and high pressure load conditions during the curing process provided by the present invention;

[0059] Figure 4 This is a schematic diagram illustrating the predicted molding defects of thickness deviation and uneven glue content provided by the present invention. Figure 4 'a' represents the thickness variation. Figure 4 b represents the fiber volume fraction distribution;

[0060] Figure 5 This is a schematic diagram of the predicted solidification residual stress provided by the present invention, wherein, Figure 5 a is the radial stress contour diagram. Figure 5 b is the circumferential stress contour plot. Figure 5 c represents the tangential stress contour diagram;

[0061] Figure 6 The structural diagram of the composite material curing and molding defect prediction system considering the flow compaction process provided by the present invention. Detailed Implementation

[0062] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0064] This invention can be used in a wide variety of general-purpose or special-purpose computing environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor devices, distributed computing environments including any of the above devices, etc.

[0065] Reference Figure 1 As shown, this invention discloses a method for predicting defects in the curing and molding of composite materials considering the flow compaction process, comprising the following steps:

[0066] S1. Data acquisition steps: Obtain the geometric dimensions of the composite material structural component and the temperature and load conditions during the actual curing process;

[0067] S2. Data preprocessing steps: Based on the geometric dimension data, temperature data and load condition data obtained in S1, establish a multi-field coupled finite element simulation model of the composite material structure considering the flow compaction process.

[0068] S3. Curing degree field acquisition steps: Based on the thermo-chemical coupling temperature field calculation model, the heat transfer module is used to calculate the temperature field change in the time domain during the curing process, and the result of the temperature field change is used as the input of the mathematical module to calculate the curing rate under each incremental step through the set curing kinetic equation, thereby obtaining the corresponding curing degree field.

[0069] S4. Corresponding parameter acquisition steps: Based on the time-varying characteristics of the composite material curing process and the curing degree field obtained in S4, calculate the thermodynamic performance parameters of the composite material and each component material in the composite material during the curing process, and obtain the relevant parameters corresponding to each incremental step, i.e. each degree of curing, including: coefficient of thermal expansion, resin viscosity and permeability.

[0070] S5. Prediction Steps: Based on the thermo-mechanical coupled stress field calculation model and the flow-compaction model, the thermal expansion and curing shrinkage strain are calculated using the time-varying parameters of each component material as input. Variables related to curing defects are obtained, including: residual stress field, thickness variation, and fiber volume fraction. The fiber volume fraction is then used as the parameter input for the time-varying characteristic calculation in S3. The process is iterative to predict molding defects, including: curing residual stress, thickness deviation, and uneven adhesive content.

[0071] Furthermore, the multi-field coupled finite element simulation models of composite material structural components considering the flow compaction process in S2 were all built on the COMSOL platform.

[0072] Specifically, based on COMSOL software, a finite element model is initialized according to the dimensional characteristics of the composite material structure and the modeling modules required for the curing process.

[0073] The curing process involves heat transfer modules such as convection of various components and hot air, and exothermic reaction of resin crosslinking; mechanical modules for the interaction of components and external loads; fluid modules for resin flow and compaction; and mathematical modules for calculating the degree of curing. A finite element model of the composite structure is initialized using COMSOL software.

[0074] Furthermore, the thermo-chemical coupling temperature field model in S3 specifically includes a heat conduction model and a curing kinetics model;

[0075] The heat conduction model is based on the heat conduction equation coupled with the exothermic curing term:

[0076]

[0077] Where K xx K yy and K zz These are the thermal conductivity coefficients of the material along each direction, T is the curing reaction temperature in the current time and space domains, and ρ is the thermal conductivity coefficient of the material along each direction. c and C c These are the density and specific heat capacity of the composite material, respectively. This represents the exothermic internal term of the resin during the curing reaction.

[0078] Specifically, the time-varying characteristics of its curing process can be described using the mixing law.

[0079]

[0080] Where, ρ m V is the density of the resin. f It is the fiber volume fraction, H m It is the heat released per unit mass of resin. It is the curing reaction rate, expressed as follows:

[0081]

[0082] Where m and n are the order of the curing reaction, and K0 is the reaction rate constant, determined by the Arrhenius equation, whose expression is as follows:

[0083] K0 = k0 exp(-ΔE0 / RT)

[0084] Based on the equations describing the heat release and heat transfer during curing, time-varying parameters related to thermodynamic properties (such as composite material density, specific heat, and thermal conductivity) are written into the variables of the model to complete the calculation of the temperature field and degree of curing field for each incremental step.

[0085] Based on the curing temperature field model, a set high temperature and high pressure load boundary condition is applied to the finite element model. The heat transfer module and the mathematical module are combined. The heat transfer module calculates the heat released by the curing reaction and updates the non-uniform temperature field. The mathematical module inputs the selected curing kinetic equation and solves the curing rate based on the obtained non-uniform temperature field to calculate the degree of curing at each moment and updates the degree of curing field.

[0086] The curing temperature field model includes a heat conduction model describing heat transfer and a curing kinetic model describing the resin crosslinking reaction process.

[0087] Furthermore, the specific details of calculating the thermodynamic property parameters of composite materials in S4 include:

[0088] Based on the mixing law, the curing degree field obtained in S3 and the mechanical property parameters of the initial resin, fiber and fiber bed are calculated to obtain the physical state of the resin during the curing process. Furthermore, the thermodynamic property parameters of the composite material and its components are calculated based on the physical state of the resin during the curing process.

[0089] The mixing law based on volume fraction is used to calculate the mechanical property parameters of composite materials, as shown in the following formula:

[0090] ρ c =V f ρ f +V m ρ m

[0091] C c =V f Cf +V m C m

[0092] Where c represents composite material, f represents fiber, and m represents resin, and V, ρ, and C represent volume fraction, density, and specific heat capacity, respectively.

[0093] Based on the mixing law of the curing process, the expression for the resin modulus Poisson's ratio is calculated, and the physical state of the resin during the curing process is obtained. The expression for the resin modulus Poisson's ratio is as follows:

[0094]

[0095]

[0096] Among them, E m v m and G m These represent the elastic modulus, Poisson's ratio, and shear modulus of the resin at this incremental step, respectively. and α represents the elastic modulus of the resin at the beginning and end of curing, respectively. gel α represents the degree of curing at the gel point. mod It is a function of curing degree and gel point.

[0097] Furthermore, in S4, the effective thermal expansion coefficient of the composite material is calculated, and the expression is as follows:

[0098]

[0099] β2=β3=(β 2f +v 12f β 1f V f +(β m +v m β m (1-V) f )-[v 12f V f +v m (1-V f )]β1

[0100] Where, β i (i = 1, 2, 3) represents the coefficient of thermal expansion, and the subscripts f and m represent fiber and resin, respectively. E 1f E represents the elastic modulus in the fiber direction 1. 1m This represents the elastic modulus of the resin in one direction.

[0101] Permeability exhibits significant anisotropy, expressed based on the Kozeny-Carman equation, as follows:

[0102]

[0103] Among them, S ii (i = x, y, z) represents the fiber bed permeability, r f V represents the fiber diameter. a denoted by k1 and k3, which represent the maximum volume fraction of the fiber. k1 and k3 are Kozeny constants.

[0104] Specifically, the flow rate of the resin matrix depends on its viscosity and directly affects the compaction process. The viscosity of the resin primarily depends on its rheological properties. The relationship between resin viscosity and curing time is fitted using the following formula:

[0105]

[0106] Where μ ∞ E μ E k and k ∞ All of these are material constants.

[0107] Then, the solved degree of curing and the mechanical property parameters of the initial resin, fiber and fiber bed are used as inputs to calculate the mechanical property parameters of the composite material and its components during the curing process. The fiber volume fraction in the calculation results of the flow compaction module is also used as an input parameter to calculate the corresponding parameters such as the coefficient of thermal expansion, resin viscosity and permeability.

[0108] Furthermore, the thermo-mechanical coupled stress field model in S5 is based on the stress-strain relationship, and its expression is as follows:

[0109] σ=Cε

[0110] ε=ε e +ε th +ε sh

[0111] Where σ represents curing stress, C represents the composite material stiffness matrix, and ε represents curing strain. e ε th and ε sh These represent elastic strain, thermal expansion strain, and curing shrinkage strain, respectively.

[0112] Specifically, by combining the boundary conditions set in the model with the solid mechanics module and the porous media Darcy flow module, thermal strain and chemical shrinkage strain are calculated, and the stress field, material deformation, pressure distribution and fiber volume fraction are updated. Through iterative iteration, the final morphology, adhesive content and residual stress of the cured composite material are solved.

[0113] In the thermo-mechanical coupled stress field calculation model, the total strain of the material is decomposed into mechanical strain ε. eand the strain ε due to thermal expansion th Curing shrinkage strain ε sh The non-mechanical strain and solidified residual stress σ are solved using Hooke's law.

[0114] Furthermore, the thermal expansion strain and curing shrinkage strain in S5 are calculated as follows:

[0115] (1) Calculate the curing shrinkage strain of the composite material, as shown in the following expression:

[0116]

[0117] in, The coefficient of thermal expansion is represented by the subscript i, which indicates the three directions along the fiber direction and perpendicular to the fiber direction, respectively. The subscripts f and m represent the fiber and resin, respectively.

[0118] (2) Thermal expansion strain, the expression is as follows:

[0119] ε th =βΔT

[0120] The thermal expansion strain ε at the corresponding moment is obtained by multiplying the coefficient of thermal expansion β and the temperature difference ΔT. th .

[0121] Furthermore, the flow-compaction model in S5 is constructed based on mass conservation, resin flow continuity, and Darcy's law, and its expression is as follows:

[0122]

[0123] P a =P+σ f

[0124] Where S ii (i = x, y, z) Fiber bed permeability, μ represents resin viscosity, P represents resin pressure, ε v σ represents volumetric strain. f P represents the effective stress of the fiber. a This indicates the application of an external load.

[0125] According to a specific embodiment of the present invention, the permeability also exhibits significant anisotropy, which can be described by the Kozeny-Carman equation, as follows:

[0126]

[0127] Where S ii (i = x, y, z) represents the fiber bed permeability, r f V represents the fiber diameter. a denoted by k1 and k3, which represent the maximum volume fraction of the fiber. k1 and k3 are Kozeny constants.

[0128] Specifically, based on the SSM model and effective stress theory, the mechanical equilibrium equations are expressed as follows:

[0129] P a =σ+P

[0130] Among them, P a σ represents the external load of the autoclave, P represents the effective stress of the fiber bed, and P represents the resin pressure.

[0131] The curing process, including heat, chemistry, mechanics, and flow compaction, was simulated and analyzed using the finite element software COMSOL to predict curing defects.

[0132] According to a specific embodiment of the present invention, the technical effect is demonstrated by taking the prediction of molding defects of L-shaped composite material structural parts considering the flow compaction process as an example. In this embodiment, a multi-field coupling analysis of the composite material curing process was performed to obtain predictions of molding defects such as residual stress after curing, thickness deviation, and uneven glue content of the L-shaped parts. The specific process includes the following steps:

[0133] Step 1: Establish as follows Figure 2 The L-shaped structural component shown has a three-dimensional finite element model. Given a refined mesh, [0] is used. 20 Material layup method.

[0134] Step 2: [The following text appears to be a separate, unrelated section:] ... Figure 3 The curing process curve shown serves as the load condition for the L-shaped part. The curing temperature T is input into the heat transfer module, and combined with the mathematical module characterizing the curing kinetic equation, the calculation of the non-uniform temperature field and the degree of curing field is realized.

[0135] Step 3: Using the calculated curing degree field of each incremental step as input, calculate the thermodynamic properties during the curing process in the set variable module that characterizes the time-varying properties of the composite material and each component material.

[0136] Step 4: Use the obtained thermodynamic performance parameters as input to the solid mechanics module and the porous Darcy's law module to predict molding defects such as thickness deviation, uneven glue content, and curing deformation in the L-shaped part. The prediction results are as follows: Figure 4 and Figure 5 As shown, where, Figure 4 'a' represents the thickness variation. Figure 4 b represents the fiber volume fraction distribution. Figure 5 a is the radial stress contour diagram. Figure 5 b is the circumferential stress contour plot. Figure 5 c represents the tangential stress contour plot.

[0137] and Figure 1Correspondingly, this invention also discloses a composite material curing and molding defect prediction system that considers the flow compaction process, such as... Figure 6 As shown, a composite material curing and molding defect prediction method considering the flow and compaction process, which applies any of the above, includes the following modules connected in sequence: a thermo-chemical coupling temperature field calculation module, a time-varying property calculation module for each component material, a thermo-mechanical coupling stress field calculation module, and a flow and compaction calculation module.

[0138] Among them, the thermo-chemical coupling temperature field calculation module is used to obtain the temperature field, curing rate and degree of curing field during the curing process of composite materials;

[0139] The time-varying property calculation module for each component material is used to obtain the mechanical property parameters of the composite material and each component material during the curing process;

[0140] Thermo-mechanical coupling stress field calculation and flow-compaction calculation modules are used to obtain molding defects including non-uniform curing residual stress field, non-uniform adhesive content and thickness deviation.

[0141] Specifically, the thermo-chemical coupling temperature field calculation module is used to obtain the temperature field, curing rate, and degree of curing field during the curing process of composite materials.

[0142] The time-varying property calculation module for each component material is used to obtain the mechanical property parameters of the composite material and each component material during the curing process. The mechanical property parameters of each component material include: thermal conductivity, modulus, coefficient of thermal expansion and viscosity of fiber and resin; the mechanical property parameters of composite material include: specific heat capacity, thermal conductivity, density, stiffness matrix, coefficient of thermal expansion, shrinkage strain and permeability.

[0143] Thermo-mechanical coupling stress field calculation and flow-compaction calculation modules are used to obtain molding defects, including non-uniform curing residual stress field, thickness variation and non-uniform adhesive content.

[0144] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0145] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both.

[0146] To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality above. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0147] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting defects in the curing and molding of composite materials considering the flow and compaction process, characterized in that, Includes the following steps: S1. Data acquisition steps: Obtain the geometric dimensions of the composite material structural component and the temperature and load conditions during the actual curing process; S2. Data preprocessing steps: Based on the geometric dimension data, temperature data and load condition data obtained in S1, establish a multi-field coupled finite element simulation model of the curing of composite material structural parts considering the flow compaction process. S3. Curing degree field acquisition steps: Based on the thermo-chemical coupling temperature field calculation model, the heat transfer module is used to calculate the temperature field change in the time domain during the curing process, and the result of the temperature field change is used as the input of the mathematical module to calculate the curing rate under each incremental step through the set curing kinetic equation, thereby obtaining the corresponding curing degree field. S4. Corresponding parameter acquisition steps: Based on the time-varying characteristics of the composite material curing process and the curing degree field obtained in S3, calculate the thermodynamic performance parameters of the composite material and each component material in the composite material during the curing process, and obtain the relevant parameters corresponding to each incremental step, i.e. each degree of curing, including: coefficient of thermal expansion, resin viscosity and permeability. S5. Prediction Steps: Based on the thermo-mechanical coupled stress field calculation model and the flow-compaction model, using the time-varying parameters of each component material as input, calculate the thermal expansion strain and curing shrinkage strain to obtain variables related to curing defects, including: residual stress field, thickness variation, and fiber volume fraction; and use the fiber volume fraction as the parameter input for the time-varying characteristic calculation in S3, iterate cyclically, and predict molding defects, including: curing residual stress, thickness deviation, and uneven glue content; The specific details of calculating the thermodynamic property parameters of composite materials in S4 include: Based on the mixing law, the curing degree field obtained in S3 and the mechanical property parameters of the initial resin, fiber and fiber bed are calculated to obtain the physical state of the resin during the curing process. Furthermore, the thermodynamic property parameters of the composite material and its components are calculated based on the physical state of the resin during the curing process. The mixing law based on volume fraction is used to calculate the mechanical property parameters of composite materials, as shown in the following formula: in, c Indicates composite materials, Indicates fiber, Represents resin. , and These represent volume fraction, density, and specific heat capacity, respectively. Based on the mixing law of the curing process, the expression for the resin modulus Poisson's ratio is calculated, and the physical state of the resin during the curing process is obtained. The expression for the resin modulus Poisson's ratio is as follows: in, , and These represent the elastic modulus, Poisson's ratio, and shear modulus of the resin at the current increment step, respectively. and These represent the elastic modulus of the resin at the beginning and end of curing, respectively. This indicates the degree of curing at the gel point. It is a function of the degree of curing and the gel point; The effective thermal expansion coefficient of the composite material is calculated in S4 using the following expression: in, Indicates the coefficient of thermal expansion, subscript f and m They represent fibers and resins, respectively. Permeability exhibits significant anisotropy, expressed based on the Kozeny-Carman equation, as follows: in, Indicates fiber bed permeability. Indicates fiber diameter. Indicates the maximum volume fraction of fibers. and It is the Kozeny constant.

2. The method for predicting defects in the curing and molding of composite materials considering the flow compaction process according to claim 1, characterized in that, The multi-field coupled finite element simulation models of composite material structural components considering the flow compaction process in S2 were all built on the COMSOL platform.

3. A method for predicting defects in the curing and molding of composite materials considering the flow compaction process according to claim 1, characterized in that, The thermal-chemical coupled temperature field model in S3 specifically includes a heat conduction model and a curing kinetics model; The heat conduction model is based on the heat conduction equation coupled with the exothermic curing term: in , and These are the thermal conductivity coefficients of the material in each direction. It is the curing reaction temperature in the current time and space domains. and These are the density and specific heat capacity of the composite material, respectively. This represents the exothermic internal term of the resin during the curing reaction.

4. A method for predicting defects in the curing and molding of composite materials considering the flow compaction process according to claim 1, characterized in that, The thermo-mechanical coupled stress field model in S5 is based on the stress-strain relationship, and its expression is as follows: in Indicates curing stress. Represents the stiffness matrix of composite materials. Indicates curing strain. , and These represent elastic strain, thermal expansion strain, and curing shrinkage strain, respectively.

5. A method for predicting defects in the curing and molding of composite materials considering the flow compaction process according to claim 4, characterized in that, The thermal expansion strain and curing shrinkage strain in S5 are calculated as follows: (1) Calculate the curing shrinkage strain of the composite material, as shown in the following expression: in, Indicates curing shrinkage strain, subscript i These represent the three directions along the fiber direction and perpendicular to the fiber direction, respectively; subscript f and m They represent fibers and resins, respectively. (2) Thermal expansion strain, the expression is as follows: Utilizing the coefficient of thermal expansion and temperature difference Multiply to obtain the thermal expansion strain at the corresponding time. .

6. A method for predicting defects in the curing and molding of composite materials considering the flow compaction process according to claim 1, characterized in that, The flow-compaction model in S5 is based on mass conservation, resin flow continuity, and Darcy's law, and its expression is as follows: in Fiber bed permeability Indicates resin viscosity. Indicates resin pressure. Indicates volumetric strain. Indicates the effective stress of the fiber. This indicates the application of an external load.

7. A composite material curing and molding defect prediction system considering the flow compaction process, characterized in that... The method for predicting defects in the curing and molding of composite materials considering the flow and compaction process, as described in any one of claims 1-6, includes the following modules connected in sequence: a thermo-chemical coupling temperature field calculation module, a time-varying property calculation module for each component material, a thermo-mechanical coupling stress field calculation module, and a flow and compaction calculation module. Among them, the thermo-chemical coupling temperature field calculation module is used to obtain the temperature field, curing rate and degree of curing field during the curing process of composite materials; The time-varying property calculation module for each component material is used to obtain the mechanical property parameters of the composite material and each component material during the curing process; Thermo-mechanical coupling stress field calculation and flow-compaction calculation modules are used to obtain molding defects including non-uniform curing residual stress field, non-uniform adhesive content and thickness deviation.

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