Method for predicting and inhibiting thermal structure deformation of large-size integral ceramic matrix composite material

Abstract

The invention discloses a large-size integral ceramic matrix composite thermal structure deformation prediction and inhibition method. The method comprises the following steps: process deformation prediction based on the influence of a ceramic precursor curing process on process deformation: specifically, establishing a ceramic matrix composite thermal structure curing model; establishing a thermal structure pyrolysis model of the ceramic matrix composite material; establishing a thermal structure permeation model of the ceramic-based composite material; obtaining the total strain increment of the ceramic precursor; predicting the thermal structure process deformation of the ceramic matrix composite material; the method further comprises process deformation regulation and control based on the influence of the ceramic precursor curing process on the process deformation. According to the method, the influence of curing and multiple rounds of pyrolysis on the process deformation is fully considered, and a more complete integral ceramic matrix composite thermal structure process deformation prediction model is established. By using the method, the PIP process scheme of different fiber / matrix materials and thermal structure geometrical shapes can be efficiently optimized at low cost, and the optimal control on the process deformation is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of advanced manufacturing of composite materials, and in particular relates to a method for predicting and suppressing thermal structural deformation of a large-scale integral ceramic-based composite material. Background Art

[0002] Large, monolithic ceramic matrix composite (CMC) thermal structural components are characterized by large size, thin walls, and complex shapes. Conformal and shape-control processes for thermal structures are key technologies in the advanced manufacturing of aerospace thermal structures and thermal protection. Accurate, rational, and efficient process mechanics models are crucial for predicting and suppressing thermal deformation in aircraft thermal structures, mitigating assembly failure risks and maximizing their thermal performance advantages and potential during design and manufacturing. The precursor infusion-pyrolysis (PIP) process is a near-net-shape fabrication method for CMC thermal structures. This process, through repeated cycles of ceramic precursor infusion and pyrolysis, gradually increases the density of the ceramic matrix. This process allows for precise control of matrix composition and microstructure, as well as net-shape fabrication of complex monolithic components, and holds significant applications in the fabrication of high-temperature, monolithic aerospace thermal structures. However, the deformation generated during the precursor pyrolysis process, particularly in large-scale monolithic CMC thermal structures, is amplified, severely hindering the advancement of large-scale monolithic CMC thermal structures and the development of high-performance thermal structures.

[0003] In the fabrication of large ceramic matrix composites (CMCs), geometric differences in materials and thermal structures, particularly those caused by geometric discontinuities and regions of varying cross-section thickness, lead to different processing conditions. However, the high cost of optimizing traditional processes restricts their industrial application. Therefore, it is crucial to investigate the deformation mechanisms and mitigation methods of large CMC thermal structures, and to uncover the mechanisms underlying the generation and evolution of these process deformations.

[0004] In short, for thin-walled, complex-shaped thermal structures, process stress during high-temperature molding often causes component deformation. Deformation will cause excessive damage to the fibers during processing, affecting material properties and even making it impossible to form according to the theoretical profile. The high-temperature molding process of large-scale integral ceramic-based composite thermal structures is very complex and lacks accurate quantitative analysis methods. The existing model method for the control of deformation of integral ceramic-based composite thermal structures has the following shortcomings: Figure 1As shown, the impact of the "curing" phase on process deformation during the PIP process is not considered. Traditional models generally assume that the ceramic precursor is in a deformation-free state after curing and before pyrolysis, and process deformation prediction begins with the pyrolysis after curing. However, in reality, a series of process deformations occur during the curing process. In addition, existing technical experience in forming thermal structures of ceramic-based composite wings and rudders lacks effective control over forming process deformation, making it unable to meet the demanding manufacturing precision and quality requirements of the new generation of large-scale, integral ceramic-based composite thermal structures. This has become a bottleneck technology that urgently needs to be overcome in the design and manufacture of thermal structures for new aircraft. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention proposes a method for predicting and suppressing the thermal structural deformation of large-scale integral ceramic-based composite materials. The purpose is to solve the problem that the existing integral ceramic-based composite material thermal structural process deformation control model method does not consider the impact of the "curing" process in the PIP process on the process deformation.

[0006] The present invention adopts the following technical solutions to solve the technical problems:

[0007] A method for predicting and suppressing thermal structural process deformation of a large-scale integral ceramic matrix composite material is characterized by comprising the following steps:

[0008] Step 1: Prediction of process deformation based on the influence of ceramic precursor curing process on process deformation:

[0009] (1) Establishment of thermal structural curing model of ceramic matrix composites;

[0010] (2) Establishment of thermal structure pyrolysis model of ceramic matrix composites;

[0011] (3) Establishment of thermal structural permeability model of ceramic matrix composites;

[0012] (4) obtaining the total strain increment of the ceramic precursor;

[0013] (5) Prediction of thermal structural process deformation of ceramic matrix composites;

[0014] Step 2: Process deformation control based on the influence of ceramic precursor curing process on process deformation:

[0015] (1) Method for suppressing process deformation based on geometric parameter control: Based on the comparison between the predicted process deformation and the target process deformation, the geometric features of the input geometric model at a certain coordinate (x, y, z) are adjusted to suppress the process deformation;

[0016] (2) Method for suppressing process deformation based on process parameter regulation: By regulating the curing process parameters and pyrolysis process parameters, the process parameters are optimized to further suppress process deformation.

[0017] Furthermore, the establishment of the thermal structure curing model of the ceramic matrix composite material in the step 1 process (1) is as follows:

[0018] For a given curing process temperature field T(x,y,z,t), the curing kinetics equation can be expressed as:

[0019]

[0020] In the formula, the known number is A which can be obtained through experiments α 、E α , n1 and the universal gas constant R, A α represents the curing reaction frequency factor, E α represents the activation energy of the curing reaction, n1 is the curing reaction order; the unknowns are absolute temperature T, curing degree α and curing rate dα / dt, among which absolute temperature T is the independent variable, and curing degree α and curing rate dα / dt are dependent variables.

[0021] Furthermore, the establishment of the thermal structure pyrolysis model of the ceramic matrix composite material in step 1 process (2) is as follows:

[0022] For a given pyrolysis process temperature field T(x,y,z,t), the pyrolysis kinetic equation can be expressed as:

[0023]

[0024] In the formula, the known number is A which can be obtained through experiments r 、E r and n2 and the universal gas constant R, A r represents the pyrolysis reaction frequency factor, E r represents the activation energy of the pyrolysis reaction, n2 is the pyrolysis reaction order; the unknowns are absolute temperature T, ceramic conversion degree r and ceramic conversion rate dr / dt, among which absolute temperature T is the independent variable, ceramic conversion degree r and ceramic conversion rate dr / dt.

[0025] Furthermore, the establishment of the thermal structure permeation model of the ceramic matrix composite material in step 1 process (3) is as follows:

[0026] (1) Establishing the mass and momentum conservation equations for fluids passing through porous media: Polymer penetration into porous ceramics is an example of a fluid passing through porous media problem. This problem is modeled using the Richard equation, which combines the mass conservation equation and the momentum conservation equation based on Darcy's law:

[0027]

[0028] Among them, the known variables are pressure head ψ, the time derivative of pressure head Fluid conductivity K, where the dependent variable is fluid diffusivity Fluid capacity θ represents the volume fraction of the retained fluid, or θ represents the filling degree of the retained fluid;

[0029] (2) Determine the distribution of polymers in the material: By integrating, we can determine the distribution of polymers in the material:

[0030] θ=∫Cdψ (4)

[0031] (3) Determine the available volume limit of θ: According to equation (4), θ is limited by the available volume of fluid filling, which is equal to the volume of open pores v p .therefore:

[0032] θ=minimum{∫Cdψ,v p} (5)

[0033] Furthermore, the total strain increment and equivalent stress increment of the ceramic precursor obtained in step 1 (4) are specifically as follows:

[0034] The incremental linear elastic model is used to describe the elastic behavior of the precursor during the curing and pyrolysis process. The total strain increment of the precursor is described as follows:

[0035] Δε=Δε e +Δε th +Δε ch (6)

[0036] Among them, ① the known number is: Δε e , Δε th and Δε ch , respectively, are the elastic strain increment Δε e , thermal strain increment Δε th and chemical shrinkage strain increment Δε ch ; where the elastic strain increment Δε e is a function of the applied load, which is a known input; the thermal strain increment Δε th =βΔT is a function of ΔT, β is the thermal expansion coefficient, which is a known number; chemical strain increment Δε ch Satisfy Δε during the curing process ch =ηΔα, which is a function of Δα and satisfies Δε during the pyrolysis process ch=ηΔr, which is a function of the ceramic conversion increment Δr, where η is the chemical shrinkage coefficient and is a known number; ② The ceramic conversion increment Δr in formula (6) will be affected by the volume fraction θ of the polymer penetrating into the porous ceramic: that is, the volume fraction θ of the retained fluid obtained by solving the permeation model will affect the evolution of Δr in each round of pyrolysis.

[0037] Furthermore, the prediction of thermal structural process deformation of ceramic matrix composite materials in step 1 (4) is specifically as follows:

[0038] ① Obtain the curing process deformation of the curing process;

[0039] ② The curing process deformation is used as the initial process deformation input of the pyrolysis process to obtain the final process deformation prediction.

[0040] Furthermore, the step 1 process (4) link ① obtains the curing process deformation of the curing process, which is as follows:

[0041] 1) Input the geometric model of the curing process;

[0042] 2) Apply the same load boundary conditions as the actual working condition to the geometric model. At this time, the increase in load leads to the generation of elastic strain increment Δε e ;

[0043] 3) Apply temperature boundary conditions T(t) to the geometric model according to the curing process temperature. At this time, the temperature change produces a thermal expansion strain increment Δε th ;

[0044] 4) Update and determine the curing degree field size α, the curing degree α changes to produce chemical shrinkage strain increment Δε ch ;

[0045] 5) Update matrix performance;

[0046] 6) Elastic strain increment Δε e , thermal expansion strain increment Δε th , chemical shrinkage strain increment Δε ch Update the curing process deformation field as input;

[0047] 7) Determine whether the curing is complete. If not, return to step 2). If completed, continue with step 8)

[0048] 8) The deformation field of the curing process is passed as input to subsequent multiple rounds of pyrolysis simulation.

[0049] Furthermore, in step 1, process (4) ②, the curing process deformation is used as the initial process deformation input of the pyrolysis process to obtain the final process deformation prediction, which is as follows:

[0050] 1) Input the geometric model, which is the same as the geometric model of the curing process;

[0051] 2) applying the same load boundary conditions as the actual working condition to the geometric model, and taking the solidification process deformation of the solidification process as the initial process deformation input of the pyrolysis process;

[0052] 3) Apply temperature boundary conditions T(t) to the geometric model according to the pyrolysis process temperature, and the temperature change generates a thermal expansion strain increment Δε th ;

[0053] 4) Update and determine the ceramic conversion degree r field size. The change of ceramic conversion degree r produces a chemical shrinkage strain increment Δε ch ;

[0054] 5) Update matrix components and properties;

[0055] 6)Δε e , Δε ch , Δε th Update the pyrolysis process deformation field as input;

[0056] 7) Determine whether the current round of pyrolysis is completed. If not, return to step 2). If completed, continue to step 8);

[0057] 8) Determine whether the pyrolysis rounds are sufficient. If sufficient, output the process deformation prediction result; if insufficient, continue process 9);

[0058] 9) Use the permeation model to calculate the pore volume fraction v in the new round of pyrolysis p Update and return to process 2) for a new round of pyrolysis.

[0059] Furthermore, the geometric model of step 2 is divided into three types: control of the microstructure and composition of the preform, control of the thermal structure geometric characteristics, and control of the surface curvature;

[0060] The preform is a geometric frame of woven fibers inside a large integral ceramic matrix composite material; the thermal structure is a large ceramic matrix composite material prepared and formed by a PIP process based on the preform; the profile curvature refers to the curvature characteristics of the geometric shape of the large ceramic matrix composite material;

[0061] Control of the microscopic structure and composition of the preform: at the microscopic level, the uniform distribution and volume fraction of the fibers are adjusted to suppress process deformation; at the mesoscopic level, the weaving or laying method of the fiber bundles, the spatial distribution of the fiber bundles, and the volume fraction are adjusted to suppress process deformation;

[0062] Control of the thermal structure's geometric features: By adjusting the thermal structure's geometric shape, size, thickness, and symmetry, the optimal geometric features are found to suppress process deformation.

[0063] Control of the curvature of the profile: Changes in curvature may change the location of stress concentration. By adjusting the profile, the process deformation distribution under different curvatures can be obtained, and then the appropriate profile curvature can be obtained.

[0064] Furthermore, the method for suppressing process deformation based on process parameter regulation in step 2 is as follows:

[0065] 1) By adjusting the curing and pyrolysis temperature curves T(t), such as the heating gradient and isothermal dwell time, the curing rate dα / dt and the pyrolysis rate dr / dt are controlled to achieve uniform curing and ceramic conversion and reduce process distortion caused by local non-uniformity. The temperature curve T(t) is the independent variable that affects the evolution of the curing degree α(x, y, z, t) and the ceramic conversion degree r(x, y, z, t).

[0066] 2) For multiple rounds of pyrolysis, the pyrolysis temperature, heating rate, and holding time are set in stages. The pyrolysis temperature, heating rate, and holding time are all included in the temperature curve T(t), so as to find the optimal process route and achieve the purpose of suppressing process deformation.

[0067] Advantages and effects of the present invention

[0068] 1. This invention fully considers the impact of curing and multiple cycles of pyrolysis on process deformation, establishing a more comprehensive model for predicting thermal structural process deformation of monolithic ceramic matrix composites. This method allows for cost-effective and efficient optimization of PIP process solutions for different fiber / matrix materials and thermal structure geometries, achieving optimal control of process deformation.

[0069] 2. Since the present invention takes into account the influence of the curing process on process deformation, the predicted process stress generated by the PIP process can be closer to the actual situation and therefore more accurate;

[0070] 3. Since the present invention takes into account the curing and multiple rounds of pyrolysis processes that mainly cause process deformation in the PIP process, it can change the process parameters of these processes based on experimental data, and then optimize the process plan to achieve the purpose of controlling process stress. Compared with traditional process optimization methods that result in higher manufacturing costs, this helps to reduce process time and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 This is a schematic diagram of the PIP process flow;

[0072] Figure 2This is a flow chart of the process deformation prediction and control method of the present invention;

[0073] Figure 3 This is a flow chart of process deformation prediction of the present invention;

[0074] Figure 4 This is a flow chart of the process deformation control of the present invention. DETAILED DESCRIPTION

[0075] 1. Innovation of the present invention: The innovation lies in: First, the degree of solidification α and the total strain increment Δε are organically combined. In formula (3), the total strain increment Δε=Δε e +Δε th +Δε ch In the description of ch Satisfy Δε during the curing process ch =ηΔα, which is a function of Δα; Δε is satisfied during the pyrolysis process ch =ηΔr, which is a function of Δr. Therefore, the total strain increment takes into account both the curing degree increment Δα and the conversion degree increment Δr. Second, the process deformation generated by the curing process is used as the initial deformation field input of multiple rounds of pyrolysis to obtain the final process deformation prediction. Figure 3 As shown in the figure, the input to the geometric model during the pyrolysis process is not only the load conditions, but also the deformation field of the curing process obtained previously. In other words, the Δε obtained during the pyrolysis process th , Δε ch , Δε e are affected by the process deformation field of the curing process, or in other words, the Δε obtained during the pyrolysis process th , Δε ch , Δε e Δε including the curing process th , Δε ch , Δε e Third, process deformation prediction based on the impact of the ceramic precursor curing process on process deformation is organically combined with process deformation control based on the impact of the ceramic precursor curing process on process deformation. Prediction comes first, followed by control. Accurate prediction leads to accurate control. Because the impact of process deformation during the curing process is taken into account when predicting process deformation, the control phase can achieve an accurate control target.

[0076] In summary, the existing technology fails to consider the comprehensive impact of the processes from solidification to multiple rounds of impregnation and pyrolysis on the evolution of process deformation in the PIP process. This patent comprehensively considers the processes from solidification to multiple rounds of impregnation and pyrolysis that mainly cause process deformation in the PIP process, and establishes a comprehensive prediction model, which can predict and suppress the evolution of process deformation of the thermal structure of large-scale integral ceramic-based composite materials.

[0077] Based on the above invention principle, the present invention designs a method for predicting and suppressing thermal structural deformation of large-scale integral ceramic matrix composite materials, such as Figure 2 、 Figure 3 、 Figure 4 As shown, its characteristics include the following steps:

[0078] Step 1: Process deformation prediction based on the influence of the ceramic precursor curing process on process deformation, specifically including the following steps:

[0079] Supplementary Note 1 :

[0080] The difference between the present invention and the prior art is that the process deformation prediction of the prior art does not take into account the process deformation caused by the curing process, but only considers the process deformation of the pyrolysis process. The difference between step one of the present invention and the prior art is that the process deformation prediction of the present invention is a prediction of the process deformation that takes into account the influence of the ceramic precursor curing process on the process deformation. Therefore, the following processes 1), 2), 3), 4), and 5) are all designed around the process deformation caused by the curing process.

[0081] (1) Establishment of thermal structural curing model of ceramic matrix composites;

[0082] The details are as follows:

[0083] For a given curing process temperature field T(x,y,z,t), the curing kinetics equation can be expressed as:

[0084]

[0085] In the formula, the known number is A which can be obtained through experiments α 、E α , n1 and the universal gas constant R, A α represents the curing reaction frequency factor, E α represents the activation energy of the curing reaction, n1 is the curing reaction order; the unknowns are absolute temperature T, curing degree α and curing rate dα / dt, among which absolute temperature T is the independent variable, and curing degree α and curing rate dα / dt are dependent variables.

[0086] (2) Establishment of thermal structure pyrolysis model of ceramic matrix composites; details are as follows:

[0087] For a given pyrolysis process temperature field T(x,y,z,t), the pyrolysis kinetic equation can be expressed as:

[0088]

[0089] In the formula, the known number is A which can be obtained through experiments r 、E rand n2 and the universal gas constant R, A r represents the pyrolysis reaction frequency factor, E r represents the activation energy of the pyrolysis reaction, n2 is the pyrolysis reaction order; the unknowns are absolute temperature T, ceramic conversion degree r and ceramic conversion rate dr / dt, among which absolute temperature T is the independent variable, ceramic conversion degree r and ceramic conversion rate dr / dt.

[0090] (3) Establishment of thermal structural permeability model of ceramic matrix composites;

[0091] The details are as follows:

[0092] ① Establishing the mass and momentum conservation equations for fluids passing through porous media: Polymer penetration into porous ceramics is an example of a fluid passing through porous media problem. This problem is modeled using the Richard equation, which combines the mass conservation equation and the momentum conservation equation based on Darcy's law:

[0093]

[0094] Among them, the known variables are pressure head ψ, the time derivative of pressure head Fluid conductivity K, where the dependent variable is fluid diffusivity Fluid capacity θ represents the volume fraction of the retained fluid, or θ represents the filling degree of the retained fluid;

[0095] ② Determine the distribution of polymers in the material: By integrating, we can determine the distribution of polymers in the material:

[0096] θ=∫Cdψ (10)

[0097] ③ Determine the available volume limit of θ: According to equation (4), θ is limited by the available volume of fluid filling, which is equal to the volume of open pores v p .therefore:

[0098] θ=minimum{∫Cdψ,v p} (11)

[0099] (4) Obtaining the total strain increment of the ceramic precursor; specifically as follows:

[0100] The incremental linear elastic model is used to describe the elastic behavior of the precursor during the curing and pyrolysis process. The total strain increment of the precursor is described as follows:

[0101] Δε=Δε e +Δε th +Δε ch (12)

[0102] Among them, ① the known number is: Δε e , Δε th and Δε cg , respectively, are the elastic strain increment Δε e , thermal strain increment Δε th and chemical shrinkage strain increment Δε ch ; where the elastic strain increment Δε e is a function of the applied load, which is a known input; the thermal strain increment Δε th =βΔT is a function of ΔT, β is the thermal expansion coefficient, which is a known number; chemical strain increment Δε ch Satisfy Δε during the curing process ch =ηΔα, which is a function of Δα and satisfies Δε during the pyrolysis process ch =ηΔr, which is a function of the ceramic conversion increment Δr, where η is the chemical shrinkage coefficient and is a known number; ② The ceramic conversion increment Δr in formula (6) will be affected by the volume fraction θ of the polymer penetrating into the porous ceramic: that is, the volume fraction θ of the retained fluid obtained by solving the permeation model will affect the evolution of Δr in each round of pyrolysis.

[0103] Supplementary Note 2 :

[0104] The left side of formula (6) is the total strain increment. It can be seen that the chemical strain increment Δε ch Satisfy Δε during the curing process ch =ηΔα, that is, the total strain increment includes the strain caused by the curing degree increment;

[0105] (5) Prediction of thermal structural process deformation of ceramic matrix composites; the specific steps are as follows:

[0106] Supplementary Note 3:

[0107] The following prediction of the final process deformation of the ceramic matrix composite thermal structure is divided into two steps. The difference between this invention and the prior art is that the curing process deformation field is calculated first, and then the total process deformation is calculated. The prior art does not include the curing process deformation field in the process deformation prediction, but only includes the process deformation during the pyrolysis process.

[0108] ① Obtain the curing process deformation of the curing process; the details are as follows:

[0109] A) Input geometry model of the curing process;

[0110] B) Apply the same load boundary conditions as the actual working condition to the geometric model. At this time, the increase in load leads to the generation of elastic strain increment Δε e ;

[0111] C) Apply temperature boundary conditions T(t) to the geometric model according to the curing process temperature. At this time, the temperature change generates a thermal expansion strain increment Δε th ;

[0112] D) Update and determine the curing degree field size α, the curing degree α changes to produce a chemical shrinkage strain increment Δε ch ;

[0113] E) Update matrix performance;

[0114] F) Elastic strain increment Δε e , thermal expansion strain increment Δε th , chemical shrinkage strain increment Δε ch Update the curing process deformation field as input;

[0115] G) Determine whether the curing is complete. If not, return to step 2). If completed, continue to step 8).

[0116] H) The deformation field of the solidification process is passed as input to subsequent multiple rounds of pyrolysis simulation.

[0117] ②Use the curing process deformation as the initial process deformation input of the pyrolysis process to obtain the final process deformation prediction. The details are as follows:

[0118] A) Input geometry model, which is the same as the geometry model of the curing process;

[0119] B) applying the same load boundary conditions as those in the actual working condition to the geometric model, and using the solidification process deformation of the solidification process as the initial process deformation input of the pyrolysis process;

[0120] C) Apply temperature boundary conditions T(t) to the geometric model according to the pyrolysis process temperature, and the temperature change generates a thermal expansion strain increment Δε th ;

[0121] D) Update and determine the field size of the ceramic conversion degree r, and the change of the ceramic conversion degree r produces a chemical shrinkage strain increment Δε ch ;

[0122] E) Update the matrix components and properties;

[0123] F)Δε e , Δε ch , Δε th Update the pyrolysis process deformation field as input;

[0124] G) Determine whether the current round of pyrolysis is completed. If not, return to step 2). If completed, continue to step 8);

[0125] H) Determine whether the pyrolysis rounds are sufficient. If sufficient, output the process deformation prediction result; if insufficient, continue with step 9);

[0126] G) Use the permeation model to calculate the pore volume fraction v in the new round of pyrolysis p Update and return to process 2) for a new round of pyrolysis.

[0127] Step 2: Process deformation control based on the influence of ceramic precursor curing process on process deformation:

[0128] Supplementary Note 4:

[0129] The difference between the present invention and the prior art is that the process deformation control is based on the process deformation prediction including the process deformation generated during the curing process.

[0130] (1) Method for suppressing process deformation based on geometric parameter control: Based on the comparison between the predicted process deformation and the target process deformation, the geometric features of the input geometric model at a certain coordinate (x, y, z) are adjusted to suppress the process deformation;

[0131] The geometric model is divided into three types: the control of the microstructure and composition of the preform, the control of the thermal structure geometric characteristics, and the control of the surface curvature;

[0132] The preform is a geometric frame of woven fibers inside a large integral ceramic matrix composite material; the thermal structure is a large ceramic matrix composite material prepared and formed by a PIP process based on the preform; the profile curvature refers to the curvature characteristics of the geometric shape of the large ceramic matrix composite material;

[0133] Control of the microscopic structure and composition of the preform: at the microscopic level, the uniform distribution and volume fraction of the fibers are adjusted to suppress process deformation; at the mesoscopic level, the weaving or laying method of the fiber bundles, the spatial distribution of the fiber bundles, and the volume fraction are adjusted to suppress process deformation;

[0134] Control of the thermal structure's geometric features: By adjusting the thermal structure's geometric shape, size, thickness, and symmetry, the optimal geometric features are found to suppress process deformation.

[0135] Control of the curvature of the profile: Changes in curvature may change the location of stress concentration. By adjusting the profile, the process deformation distribution under different curvatures can be obtained, and then the appropriate profile curvature can be obtained.

[0136] (2) Method for suppressing process deformation based on process parameter regulation: By regulating the curing process parameters and pyrolysis process parameters, the process parameters are optimized to further suppress process deformation.

[0137] The details are as follows:

[0138] ① By adjusting the curing and pyrolysis temperature curves T(t), such as the heating gradient and isothermal dwell time, the curing rate dα / dt and the pyrolysis rate dr / dt are controlled to ensure uniform curing and ceramic conversion, thereby reducing process deformation caused by local unevenness. The temperature curve T(t) is the independent variable that affects the evolution of the curing degree α(x, y, z, t) and the ceramic conversion degree r(x, y, z, t).

[0139] ② For the multi-round pyrolysis process, the pyrolysis temperature, heating rate and holding time are set in stages. The pyrolysis temperature, heating rate and holding time are all included in the temperature curve T(t), so as to find the optimal process route and achieve the purpose of suppressing process deformation.

[0140] It should be emphasized that the above specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the above embodiments as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for predicting and suppressing thermal structural deformation of large-scale monolithic ceramic matrix composite materials, characterized in that: The following steps are involved: Step 1: Prediction of process deformation based on the influence of ceramic precursor curing process on process deformation: (1) Establishment of thermal structural curing model of ceramic matrix composites; (2) Establishment of thermal structure pyrolysis model of ceramic matrix composites; (3) Establishment of thermal structural permeability model of ceramic matrix composites; (4) obtaining the total strain increment of the ceramic precursor; (5) Prediction of thermal structural process deformation of ceramic matrix composites; Step 2: Process deformation control based on the influence of ceramic precursor curing process on process deformation: (1) Process deformation suppression method based on geometric parameter control: Based on the comparison between the predicted process deformation and the target process deformation, the process deformation is suppressed by adjusting the geometric features of the input geometric model at a certain coordinate (x, y, z); (2) Methods for suppressing process deformation based on process parameter control; By adjusting the curing process parameters and the pyrolysis process parameters, the process parameters can be optimized to further suppress process deformation.

2. The method for predicting and suppressing thermal structural deformation of a large-scale integral ceramic matrix composite material according to claim 1, characterized in that: The establishment of the thermal structure curing model of the ceramic matrix composite material in the step 1 process (1) is as follows: For a given curing process temperature field T(x,y,z,t), the curing kinetics equation can be expressed as: In the formula, the known number is A which can be obtained through experiments α 、E α , n1 and the universal gas constant R, A α represents the curing reaction frequency factor, E α represents the activation energy of the curing reaction, n1 is the curing reaction order; the unknowns are absolute temperature T, curing degree α and curing rate dα / dt, among which absolute temperature T is the independent variable, and curing degree α and curing rate dα / dt are dependent variables.

3. The method for predicting and suppressing thermal structural deformation of a large-scale integral ceramic matrix composite material according to claim 1, characterized in that: The establishment of the thermal structure pyrolysis model of the ceramic matrix composite material in the step 1 process (2) is as follows: For a given pyrolysis process temperature field T(x, y, z, t), the pyrolysis kinetic equation can be expressed as: In the formula, the known number is A which can be obtained through experiments r 、E r and n2 and the universal gas constant R, A r represents the pyrolysis reaction frequency factor, E r represents the activation energy of the pyrolysis reaction, n2 is the pyrolysis reaction order; the unknowns are absolute temperature T, ceramic conversion degree r and ceramic conversion rate dr / dt, among which absolute temperature T is the independent variable, ceramic conversion degree r and ceramic conversion rate dr / dt.

4. The method for predicting and suppressing thermal structural deformation of a large-scale integral ceramic matrix composite material according to claim 1, characterized in that: The establishment of the thermal structure permeation model of the ceramic matrix composite material in the step 1 process (3) is as follows: (1) Establishing the mass and momentum conservation equations for fluids passing through porous media: Polymer penetration into porous ceramics is an example of a fluid passing through porous media problem. This problem is modeled using the Richard equation, which combines the mass conservation equation and the momentum conservation equation based on Darcy's law: Among them, the known variables are pressure head ψ, the time derivative of pressure head Fluid conductivity K, where the dependent variable is fluid diffusivity Fluid capacity θ represents the volume fraction of the retained fluid, or θ represents the filling degree of the retained fluid; (2) Determine the distribution of polymers in the material: By integrating, we can determine the distribution of polymers in the material: θ=∫Cdψ (4) (3) Determine the available volume limit of θ: According to equation (4), θ is limited by the available volume of fluid filling, which is equal to the volume of open pores v p ,therefore: θ=minimum{∫Cdψ,v p } (5).

5. The method for predicting and suppressing thermal structural deformation of a large-scale integral ceramic matrix composite material according to claim 1, characterized in that: The total strain increment and equivalent stress increment of the ceramic precursor obtained in step 1 (4) are as follows: The incremental linear elastic model is used to describe the elastic behavior of the precursor during the curing and pyrolysis process. The total strain increment of the precursor is described as follows: No = No e +No th +No ch (6) Among them, ① the known number is: Δε e , Δε th and Δε ch , respectively, are the elastic strain increment Δε e , thermal strain increment Δε th and chemical shrinkage strain increment Δε ch ; where the elastic strain increment Δε e is a function of the applied load, which is a known input; the thermal strain increment Δε th =βΔT is a function of ΔT, β is the thermal expansion coefficient, which is a known number; chemical strain increment Δε ch Satisfy Δε during the curing process ch =ηΔα, which is a function of Δα and satisfies Δε during the pyrolysis process ch =ηΔr, which is a function of the ceramic conversion increment Δr, where η is the chemical shrinkage coefficient and is a known number; ② The ceramic conversion increment Δr in formula (6) will be affected by the volume fraction θ of the polymer penetrating into the porous ceramic: that is, the volume fraction θ of the retained fluid obtained by solving the permeation model will affect the evolution of Δr in each round of pyrolysis.

6. The method for predicting and suppressing thermal structural deformation of a large-scale integral ceramic matrix composite material according to claim 1, characterized in that: The prediction of thermal structural process deformation of ceramic matrix composite materials in step 1 (4) is as follows: ① Obtain the curing process deformation of the curing process; ② The curing process deformation is used as the initial process deformation input of the pyrolysis process to obtain the final process deformation prediction.

7. The method for controlling thermal structural deformation of a large-scale integral ceramic matrix composite material according to claim 6, characterized in that: The step 1 process (4) step ① obtains the curing process deformation of the curing process, which is as follows: 1) Input the geometric model of the curing process; 2) Apply the same load boundary conditions as the actual working condition to the geometric model. At this time, the increase in load leads to the generation of elastic strain increment Δε e ; 3) Apply temperature boundary conditions T(t) to the geometric model according to the curing process temperature. At this time, the temperature change produces a thermal expansion strain increment Δε th ; 4) Update and determine the curing degree field size α, the curing degree α changes to produce chemical shrinkage strain increment Δε ch ; 5) Update matrix performance; 6) Elastic strain increment Δε e , thermal expansion strain increment Δε th , chemical shrinkage strain increment Δε ch Update the deformation field of the curing process as input; 7) Determine whether the curing is complete. If not, return to step 2). If completed, continue with step 8) 8) The deformation field of the curing process is passed as input to subsequent multiple rounds of pyrolysis simulation.

8. The method for controlling thermal structural deformation of a large-scale integral ceramic matrix composite material according to claim 6, characterized in that: In step 1, process (4) ②, the curing process deformation is used as the initial process deformation input of the pyrolysis process to obtain the final process deformation prediction, as follows: 1) Input the geometric model, which is the same as the geometric model of the curing process; 2) applying the same load boundary conditions as the actual working condition to the geometric model, and taking the solidification process deformation of the solidification process as the initial process deformation input of the pyrolysis process; 3) Apply temperature boundary conditions T(t) to the geometric model according to the pyrolysis process temperature, and the temperature change generates a thermal expansion strain increment Δε th ; 4) Update and determine the ceramic conversion degree The magnitude of the field r and the change in the ceramic conversion degree r produce a chemical shrinkage strain increment Δε ch ; 5) Update matrix components and properties; 6)Δε e , Δε ch , Δε th Update the pyrolysis process deformation field as input; 7) Determine whether the current round of pyrolysis is completed. If not, return to step 2). If completed, continue to step 8); 8) Determine whether the pyrolysis rounds are sufficient. If sufficient, output the process deformation prediction result; if insufficient, continue process 9); 9) Use the permeation model to calculate the pore volume fraction v in the new round of pyrolysis p Update and return to process 2) for a new round of pyrolysis.

9. The method for predicting and suppressing thermal structural deformation of a large-scale integral ceramic matrix composite material according to claim 1, characterized in that: The geometric models in step 2 are divided into three types: the control of the microstructure and composition of the preform, the control of the thermal structure geometric characteristics, and the control of the surface curvature; The preform is a geometric frame of woven fibers inside a large integral ceramic matrix composite material; the thermal structure is a large ceramic matrix composite material prepared and formed by a PIP process based on the preform; The surface curvature refers to the curvature characteristics of the geometric shape of the large ceramic matrix composite material; Control of the microstructure and composition of the preform: At the micro level, the uniform distribution and volume fraction of the fibers are adjusted to suppress process deformation; At the microscopic level, process deformation can be suppressed by adjusting the weaving or laying method of fiber bundles, the spatial distribution of fiber bundles, and the volume fraction; Control of the thermal structure's geometric features: By adjusting the thermal structure's geometric shape, size, thickness, and symmetry, the optimal geometric features are found to suppress process deformation. Control of the curvature of the profile: Changes in curvature may change the location of stress concentration. By adjusting the profile, the process deformation distribution under different curvatures can be obtained, and then the appropriate profile curvature can be obtained.

10. According to the method for predicting and suppressing thermal structural deformation of a large-scale monolithic ceramic matrix composite material in claim 1, the method for suppressing process deformation based on process parameter regulation in step 2 is as follows: 1) By adjusting the curing and pyrolysis temperature curves T(t), such as the heating gradient and isothermal dwell time, the curing rate dα / d and the pyrolysis rate dr / dt are controlled to achieve uniform curing and ceramic conversion and reduce process deformation caused by local unevenness; the temperature curve T(t) is the independent variable that affects the evolution of the curing degree α(x, y, z, t) and the ceramic conversion degree r(x, y, z, t); 2) For multiple rounds of pyrolysis, the pyrolysis temperature, heating rate, and holding time are set in stages. The pyrolysis temperature, heating rate, and holding time are all included in the temperature curve T(t), so as to find the optimal process route and achieve the purpose of suppressing process deformation.

Images