Three-dimensional thermal response analysis method for composite stiffened wallboard

Abstract

The invention belongs to the field of material analysis, and particularly discloses a composite material stiffened wallboard three-dimensional thermal response analysis method which comprises the following steps: S1, establishing a composite material thermal response control equation; s2, the corresponding relation between the material density and the field variable is stipulated, and updating of the state variable is defined in a UMATHT subprogram; s3, calling UMATHT and USDFLD user subprograms to simulate thermal response calculation of the composite material under single-side heating, and calculating temperature response and pyrolysis degree of the composite material stiffened wallboard; according to the method, a composite material three-dimensional thermal response control equation set considering a polymer thermal decomposition reaction is established, a composite material thermal response analysis finite element model capable of considering polymer matrix decomposition is established based on secondary development of ABAQUS user subprograms UMATHT and USDFLD, and by calling the subprograms in ABAQUS software, a composite material thermal response analysis finite element model capable of considering polymer matrix decomposition is established. And thermal response analysis of the polymer matrix composite stiffened wall plate with a complex structure can be realized.

Description

Technical Field

[0001] The invention belongs to the field of material analysis, and in particular relates to a three-dimensional thermal response analysis method for a composite material reinforced wall panel. Background Art

[0002] Due to the excellent properties of fiber-reinforced composite materials such as light weight, corrosion resistance, high specific strength, good fatigue resistance, and rapid repair, they have been widely used in the aviation industry in recent years. For example, they are used in structures such as fuselages, wings, and tails. They are also used in jet engine components, including air intake fan blades, blade casings, and fairings. Fire is one of the major safety threats faced by modern passenger aircraft. The widespread use of composite materials in aircraft structures has attracted people's attention to the safety of composite materials in fire environments. One of the key factors to be considered in the design and use of composite materials is the fire resistance of the structure. Although polymer-based composite materials have lower thermal conductivity than traditional metals, due to the high flammability of the resin matrix, composite materials will undergo a series of physical and chemical changes at high temperatures. Therefore, it is necessary to evaluate the structural stability and integrity of the damaged area and its adjacent areas, and analyze and study whether the thermal damage caused by such accidents during flight will endanger flight safety.

[0003] However, existing methods often use linear heat conduction models, which do not take into account the complex phenomena caused by the pyrolysis of the composite matrix. In addition, most existing calculation methods usually assume that the material properties remain unchanged during use. But in fact, the thermal conductivity, specific heat capacity, and other physical properties of the material will change significantly with changes in temperature. Ignoring the nonlinear thermal behavior of the material will lead to an incorrect assessment of the thermal response, which in turn affects the service life and safety of the material. In practical applications, these simplified models lead to inaccurate predictions of temperature response, which may lead to safety hazards.

[0004] On the other hand, composite reinforced panels are commonly seen in actual engineering structures, rather than single-thickness laminates. Composite reinforced panels are three-dimensional structures composed of flat plates and reinforcing bars, and their thermal response analysis is generally performed using mature commercial finite element software such as ABAQUS. However, the heat transfer module of ABAQUS does not take into account the complex phenomena caused by the pyrolysis of the composite matrix. For actual polymer-based composite materials, a series of physical and chemical changes may occur during the heating process, including nonlinear changes caused by pyrolysis of the material matrix, thermal convection of decomposed gases, and anisotropic heat conduction inside the material. The heat transfer module that comes with ABAQUS may not be able to fully cover and cannot meet the actual calculation accuracy. Summary of the invention

[0005] The purpose of the present invention is to provide a three-dimensional thermal response analysis method for composite reinforced wall panels, which can be used to predict the thermal response law and decomposition law of polymer-based composite reinforced wall panels under fire environment, provide a fast and low-cost composite thermal response evaluation method for the aviation industry, and provide an effective analysis method for the composite structure design of civil aircraft.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A three-dimensional thermal response analysis method for composite material reinforced wall panels, comprising:

[0008] S1. Establishing a control equation for thermal response of a composite material, wherein the control equation for thermal response of the composite material includes: a heat transfer equation for the composite material under a heat flow load, a decomposition rate equation for the material, and a continuity equation;

[0009] S2. Based on the writing rules of ABAQUS user subroutines UMATHT and USDFLD, the expansion of the composite material thermal response control equation from one dimension to three dimensions is derived and realized. The relationship between the field variables and the state variables is defined through the USDFLD subroutine, and the corresponding relationship between the material density and the field variables is specified. The update of the state variables is defined in the UMATHT subroutine;

[0010] S3. Use ABAQUS software to establish a finite element model of composite reinforced wall panels subjected to unilateral heating. By calling the UMATHT and USDFLD user subroutines, simulate the thermal response calculation of the composite material under unilateral heating, and calculate the temperature response and degree of thermal decomposition of the composite reinforced wall panels.

[0011] Preferably, the heat transfer equation of the composite material under the action of heat flux load is as follows:

[0012]

[0013] Where: T represents temperature, t represents time, ρ represents material density, represents the gas mass flow rate, and are the enthalpy change of solid material and gas, C p , C pg are the specific heat capacity of solid materials and gas respectively, T0 represents the initial temperature, k1, k2, k3 are the thermal conductivities of the three coordinate directions x, y, z of the materials respectively, where x and y are the coordinates along the plane of the material, z is the coordinate along the thickness of the material, Q is the decomposition heat, and Q is a negative value for endothermic reactions.

[0014] Preferably, the decomposition rate equation of the material is as follows:

[0015]

[0016] Where: v is the original material density, ρ char is the density of completely carbonized material, A, E, n are reaction rate constants: preexponential factor, activation energy, reaction order, and R is the ideal gas constant.

[0017] Preferably, the specific form of the continuity equation is obtained based on the assumption that the decomposed gas does not accumulate inside the material, as shown below:

[0018]

[0019] During the material decomposition process, the decomposition degree of the material is represented by the remaining mass fraction of the original material, and the remaining mass fraction F of the original material is calculated according to the following formula:

[0020]

[0021] Anisotropic thermal conductivity k of the material i , expressed as:

[0022] k i =Fk v +(1-F)k c (i=1,2,3) (5)

[0023] Where: k v is the thermal conductivity of the original material, k c is the thermal conductivity of the completely carbonized material;

[0024] The specific heat capacity of a solid material is expressed as:

[0025] C p =FC pv +(1-F)C pc (6)

[0026] Where: C pv is the specific heat capacity of the original material, C pc is the specific heat capacity of completely carbonized material.

[0027] Preferably, the internal heat energy per unit mass U and the partial derivative of the internal heat energy per unit mass with respect to temperature are defined in the ABAQUS user subroutine as Partial derivative of internal heat energy per unit mass with respect to temperature gradient Heat flow vector f, partial derivative of heat flow vector with respect to temperature Partial derivative of the heat flux vector with respect to the temperature gradient These variables are evaluated at every increment.

[0028] Preferably, the expansion of the composite material thermal response control equation from one dimension to three dimensions comprises expanding equation (1) and substituting it into equation (3) to obtain a three-dimensional heat transfer equation:

[0029]

[0030] The basic energy balance equation of heat transfer analysis is combined to obtain the expressions of variables such as U, DUDT, etc.

[0031] Preferably, the calculation formula for the internal energy heat increase ΔU in one of the incremental steps is:

[0032]

[0033] Partial derivative of internal heat energy per unit mass with respect to temperature The calculation formula is:

[0034]

[0035] Partial derivative of internal heat energy per unit mass with respect to temperature gradient The calculation formula is:

[0036]

[0037] The calculation formula of heat flow vector f is:

[0038]

[0039] Partial derivative of heat flux vector with respect to temperature The calculation formula is:

[0040]

[0041] Partial derivative of the heat flux vector with respect to the temperature gradient The calculation formula is:

[0042]

[0043] Preferably, the calculation formula for calculating the thermal response of the simulated composite material under single-side heating for initial conditions and boundary conditions is as follows:

[0044] Initial conditions:

[0045]

[0046] Heated surface boundary conditions:

[0047]

[0048] Backside thermal boundary condition:

[0049]

[0050] Where: q″ rad is the externally applied radiation heat flux, f(t) is the net heat flux of the heated surface, σ is the Boltzmann constant, T s 、T back are the surface and back temperatures of the material, T ∞ is the ambient temperature, h front 、h back are the convective heat transfer coefficients on the surface and back of the material, and ε is the reflectivity of the material.

[0051] Preferably, the expansion of the composite material thermal response control equation from one dimension to three dimensions is derived and implemented based on the writing rules of ABAQUS user subroutines UMATHT and USDFLD, and is compiled and implemented using Fortran language code through Visual studio software platform.

[0052] Preferably, the S3 step comprises:

[0053] S3.1. Establish a composite material stiffened panel component model, including the flat plate, long stringer and web structure, and define the basic dimensions of the model;

[0054] S3.2. Set the material properties of the composite material stiffened panel component model. The model is a three-dimensional stiffened panel structure. Each component, such as the flat plate, web plate, and long stringer, sets the material properties and defines its own coordinate system separately to correspond to the subroutine. The density is set to be related to the carbonization rate field variable, and a non-independent variable option is added. The dimension of the state variable matrix defined and output is set; user-defined scenarios and user-defined material options are added;

[0055] S3.3. The connection mode of each component of the model is defined in the interaction module. The connection mode between the lower surface of the plate and the upper surface of the long stringer, and the lower surface of the long stringer and the upper surface of the web are all Tie connection, so as to realize the rigid connection between the two surfaces, and the binding area does not have relative movement and deformation;

[0056] S3.4. Create the first analysis step for heat transfer analysis. Set the time to the actual heating time. Both the initial time increment and the time increment are set to a fixed value of 1. In the field variable output requirement manager, the variable to be output is temperature.

[0057] S3.5. Setting the model boundary conditions, including convective heat transfer and radiation heat transfer on the material surface, wherein the convective heat transfer coefficient and the material reflectivity of the material are set;

[0058] S3.6. Apply a surface heat flux load that is consistent with reality;

[0059] S3.7, based on the grid module, meshing the model;

[0060] S3.8. In the job module, when submitting a job, submit the written composite material thermal response subroutine in the user subroutine location, submit the calculation, and obtain the temperature response and thermal decomposition degree calculation results.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] The present invention establishes a three-dimensional thermal response control equation group of composite materials considering the thermal decomposition reaction of polymers by targeting the thermal response analysis technology of polymer-based composite material stiffened panels, which can consider the anisotropic heat conduction inside the material and the gas mass flow in the thickness direction. Based on the secondary development of ABAQUS user subroutines UMATHT and USDFLD, a composite material thermal response analysis finite element model considering the decomposition of the polymer matrix is ​​established, which can realize the thermal response analysis of polymer-based composite material stiffened panels with complex configurations, and can predict the thermal responses such as temperature and decomposition degree under the action of unilateral radiation heat flow, thereby providing a fast and low-cost composite material thermal response evaluation method for the aviation industry and an effective analysis means for the composite material structure design of civil aircraft.

[0063] The present invention calculates a composite material structure with a complex shape, defines a separate coordinate system for each component and writes a UMATHT subroutine corresponding to each component, and links each separate subroutine to form a UMATHT subroutine that can be called to calculate the thermal response of the complex structure of the stiffened wall panel. Through the UMATHT subroutine, the temperature field of the material is updated in real time to ensure that the temperature change reflects the material performance immediately, and considers the equations of anisotropic heat conduction inside the material, decomposed gas heat convection, and material thermal decomposition heat absorption, so that the heat conduction calculation can still maintain high accuracy under complex geometric shapes and multi-material interfaces.

[0064] The present invention dynamically adjusts material properties by utilizing the USDFLD subroutine, thereby taking into account the effect of material decomposition changes on temperature during the decomposition reaction, and ensuring that the behavior of the material at different temperatures can be accurately described. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0066] Figure 1 A flowchart of the method steps of the present invention;

[0067] Figure 2 The thermal response analysis calculation flow chart of the present invention;

[0068] Figure 3 This is a schematic diagram of the distribution of measurement points of the ribs on the front side of the wall panel of the present invention;

[0069] Figure 4 It is the time-temperature curve diagram of the front measurement point of the present invention;

[0070] Figure 5 This is a schematic diagram of the distribution of measuring points of the ribs on the back of the wall panel of the present invention;

[0071] Figure 6 It is the time-temperature curve diagram of the back measurement point of the present invention;

[0072] Figure 7 The pyrolysis rate cloud diagram was calculated for the analysis of the present invention. DETAILED DESCRIPTION

[0073] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0074] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0075] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0076] As attached Figure 1 To Attachment Figure 2 As shown:

[0077] Embodiment 1: This embodiment provides a three-dimensional thermal response analysis method for a composite material reinforced wall panel, comprising:

[0078] S1. Establish the control equation of thermal response of composite materials. The control equation of thermal response of composite materials includes: heat transfer equation (energy conservation equation) of composite materials under heat flow load, material decomposition rate equation (Arrhenius equation) and continuity equation (mass conservation equation);

[0079] S2. Based on the writing rules of ABAQUS user subroutines UMATHT and USDFLD, the expansion of the thermal response control equation of composite materials from one dimension to three dimensions is derived and realized. The relationship between field variables and state variables is defined through the USDFLD subroutine, and the corresponding relationship between material density and field variables is specified. The update of state variables is defined in the UMATHT subroutine, and it is written in the Fortran language through the UMATHT subroutine module;

[0080] S3. Use ABAQUS software to establish a finite element model of composite reinforced wall panels subjected to unilateral heating. By calling the UMATHT and USDFLD user subroutines, simulate the thermal response calculation of the composite material under unilateral heating, and calculate the temperature response and degree of thermal decomposition of the composite reinforced wall panels.

[0081] By defining the above variables and updating the state variables through ABAQUS subroutines, the thermal response analysis and calculation of composite materials considering the decomposition gas convection heat transfer and material decomposition can be carried out;

[0082] A set of three-dimensional thermal response control equations for composite materials considering the thermal decomposition reaction of polymers was established, including: heat transfer equation (energy conservation equation), decomposition rate equation and continuity equation (mass conservation equation). At the same time, the anisotropic heat conduction inside the material and the gas mass flow in the thickness direction can be considered. Based on the secondary development of ABAQUS user subroutines UMATHT and USDFLD, the variables such as material thermal conductivity, specific heat capacity, material and decomposition gas enthalpy change, decomposition degree, internal heat energy, change of internal heat energy with temperature, change of internal energy with temperature spatial gradient, heat flux vector, heat flux vector for temperature change, heat flux vector for temperature spatial gradient change are defined and updated by writing FORTRAN programs. A finite element model for thermal response analysis of composite materials considering the decomposition of polymer matrix is ​​established, which can realize the thermal response analysis of polymer-based composite reinforced panels with complex configurations, and can predict the thermal response such as temperature and decomposition degree under the action of unilateral radiation heat flow.

[0083] The internal heat energy per unit mass U and the partial derivative of the internal heat energy per unit mass with respect to temperature are defined in the ABAQUS user subroutine. Partial derivative of internal heat energy per unit mass with respect to temperature gradient Heat flow vector f, partial derivative of heat flow vector with respect to temperature Partial derivative of the heat flux vector with respect to the temperature gradient These variables are evaluated at every increment.

[0084] The expansion of the thermal response control equation of composite materials from one dimension to three dimension includes expanding equation (1) and substituting it into (3) to obtain the three-dimensional heat transfer equation:

[0085]

[0086] The basic energy balance equation of heat transfer analysis is combined to obtain the expressions of variables such as U, DUDT, etc.

[0087] The calculation formula for the internal energy increase ΔU in an incremental step is:

[0088]

[0089] Partial derivative of internal heat energy per unit mass with respect to temperature The calculation formula is:

[0090]

[0091] Partial derivative of internal heat energy per unit mass with respect to temperature gradient The calculation formula is:

[0092]

[0093] The calculation formula of heat flow vector f is:

[0094]

[0095] Partial derivative of heat flux vector with respect to temperature The calculation formula is:

[0096]

[0097] Partial derivative of the heat flux vector with respect to the temperature gradient The calculation formula is:

[0098]

[0099] The calculation formula for the initial conditions and boundary conditions for simulating the thermal response of composite materials under single-sided heating is as follows:

[0100] Initial conditions:

[0101]

[0102] Heated surface boundary conditions:

[0103]

[0104] Backside thermal boundary condition:

[0105]

[0106] Where: q″ rad is the externally applied radiation heat flux, f(t) is the net heat flux of the heated surface, σ is the Boltzmann constant, T s 、T backare the surface and back temperatures of the material, T ∞ is the ambient temperature, h front 、h back are the convective heat transfer coefficients on the surface and back of the material, and ε is the reflectivity of the material.

[0107] Based on the writing rules of ABAQUS user subroutines UMATHT and USDFLD, the expansion of the thermal response control equation of composite materials from one dimension to three dimensions is derived and implemented, which is compiled using Fortran language code through the Visual studio software platform.

[0108] The S3 steps include:

[0109] S3.1. Establish a composite material stiffened panel component model, including the flat plate, long stringer and web structure, and define the basic dimensions of the model;

[0110] S3.2. Set the material properties of the composite material stiffened panel component model. The model is a three-dimensional stiffened panel structure. Each component, such as the flat plate, web plate, and long stringer, sets the material properties and defines its own coordinate system separately to correspond to the subroutine. The density is set to be related to the carbonization rate field variable, and a non-independent variable option is added. The dimension of the state variable matrix defined and output is set; user-defined scenarios and user-defined material options are added;

[0111] S3.3. The connection mode of each component of the model is defined in the interaction module. The connection mode between the lower surface of the plate and the upper surface of the long stringer, and the lower surface of the long stringer and the upper surface of the web are all Tie connections, so that the two surfaces are rigidly connected, and the binding area does not have relative movement and deformation;

[0112] S3.4. Create the first analysis step for heat transfer analysis. Set the time to the actual heating time. Both the initial time increment and the time increment are set to a fixed value of 1. In the field variable output requirement manager, the variable to be output is temperature.

[0113] S3.5. Set the model boundary conditions, including the convective heat transfer and radiation heat transfer on the material surface, including setting the convective heat transfer coefficient and material reflectivity of the material;

[0114] S3.6. Apply a surface heat flux load that is consistent with reality;

[0115] S3.7, based on the grid module, mesh the model;

[0116] S3.8. In the job module, when submitting a job, submit the written composite material thermal response subroutine in the user subroutine position, submit the calculation, and obtain the temperature response and pyrolysis degree calculation results;

[0117] Calculate the stiffened wall panels composed of different material system components including flat plates, long girders and webs, write the corresponding UMATHT subroutine for each component, and link each individual subroutine to form a UMATHT subroutine that can be called to calculate the thermal response of the complex structure of the stiffened wall panels.

[0118] From the above, we can see that considering a series of physical and chemical changes that occur in polymer-based composite materials during heating, including changes caused by material pyrolysis, anisotropic heat conduction inside the material, and heat convection of decomposed gases, the established composite thermal response control equations include: heat transfer equation (energy conservation equation), decomposition rate equation (Arrhenius equation) and continuity equation (mass conservation equation). Finite element modeling of composite stiffened panels heated on one side was carried out using the finite element software ABAQUS, and the thermal response law of composite stiffened panels was calculated and analyzed using the written composite thermal response subroutine;

[0119] Through the UMATHT subroutine, the temperature field of the material is updated in real time to ensure that the temperature change reflects the material performance immediately, and the equations of anisotropic heat conduction inside the material, decomposition gas heat convection, and material thermal decomposition heat absorption are considered, and are written in Fortran language through the UMATHT subroutine module. This method uses numerical integration and optimization algorithms to ensure that the heat conduction calculation can still maintain high accuracy under complex geometric shapes and multi-material interfaces;

[0120] The USDFLD subroutine is used to dynamically adjust material properties, so that the effect of material decomposition changes on temperature in the decomposition reaction can be considered, ensuring that the behavior of the material at different temperatures can be accurately described.

[0121] Example 2: A three-dimensional thermal response analysis method for composite reinforced wall panels is used for simulation analysis. Specifically, 12 points evenly distributed on the front ribs of the wall panels are selected, and the labels are as shown in the attached figure. Figure 3 As shown in the figure, since the plane direction is defined as isotropic in the subroutine, the calculated temperatures of points 1-4, 5-8, and 9-12 are the same, and their temperature-time history curves are shown in the attached figure. Figure 4 As shown;

[0122] Take the 6 points marked on the ribs on the back of the wall panel as shown in the attached Figure 5 The temperature-time history curve is shown in the attached Figure 6 As shown;

[0123] Analysis and calculation of the pyrolysis rate cloud diagram as attached Figure 7 As shown:

[0124] Results: For complex structures such as reinforced wall panels, a thermal response analysis method considering pyrolysis was developed, and a pyrolysis rate cloud map can be output.

[0125] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values ​​(e.g., temperature, pressure, etc.), installation arrangement, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of performing the function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to several modifications still falling within the scope of the appended claims.

[0126] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0127] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0128] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A three-dimensional thermal response analysis method for composite reinforced wall panels, characterized in that: include: S1. Establishing a control equation for thermal response of a composite material, wherein the control equation for thermal response of the composite material includes: a heat transfer equation for the composite material under a heat flow load, a decomposition rate equation for the material, and a continuity equation; S2. Based on the writing rules of ABAQUS user subroutines UMATHT and USDFLD, the expansion of the composite material thermal response control equation from one dimension to three dimensions is derived and realized. The relationship between the field variables and the state variables is defined through the USDFLD subroutine, and the corresponding relationship between the material density and the field variables is specified. The update of the state variables is defined in the UMATHT subroutine; S3. Use ABAQUS software to establish a finite element model of composite reinforced wall panels subjected to unilateral heating. By calling the UMATHT and USDFLD user subroutines, simulate the thermal response calculation of the composite material under unilateral heating, and calculate the temperature response and degree of thermal decomposition of the composite reinforced wall panels.

2. A three-dimensional thermal response analysis method for composite reinforced wall panels according to claim 1, characterized in that: The heat transfer equation of the composite material under the action of heat flux load is as follows: Where: T represents temperature, t represents time, ρ represents material density, represents the gas mass flow rate, and are the enthalpy change of solid material and gas, C p , C pg are the specific heat capacity of solid materials and gas respectively, T0 represents the initial temperature, k1, k2, k3 are the thermal conductivities of the three coordinate directions x, y, z of the materials respectively, where x and y are the coordinates along the plane of the material, z is the coordinate along the thickness of the material, Q is the decomposition heat, and Q is a negative value for endothermic reactions.

3. A three-dimensional thermal response analysis method for composite reinforced wall panels according to claim 2, characterized in that: The decomposition rate equation of the material is shown below: Where: v is the original material density, ρ char is the density of completely carbonized material, A, E, n are reaction rate constants: preexponential factor, activation energy, reaction order, and R is the ideal gas constant.

4. A three-dimensional thermal response analysis method for composite reinforced wall panels according to claim 3, characterized in that: The specific form of the continuity equation is obtained based on the assumption that the decomposition gas does not accumulate inside the material, as shown below: During the material decomposition process, the decomposition degree of the material is represented by the remaining mass fraction of the original material, and the remaining mass fraction F of the original material is calculated according to the following formula: Anisotropic thermal conductivity k of the material i , expressed as: k i =Fk v +(1-F)k c (i=1,2,3) (5) Where: k v is the thermal conductivity of the original material, k c is the thermal conductivity of the completely carbonized material; The specific heat capacity of a solid material is expressed as: C p =FC pv +(1-F)C pc (6) Where: C pv is the specific heat capacity of the original material, C pc is the specific heat capacity of completely carbonized material.

5. A three-dimensional thermal response analysis method for composite material reinforced wall panels according to claim 4, characterized in that: The ABAQUS user subroutine defines the internal heat energy per unit mass U and the partial derivative of the internal heat energy per unit mass with respect to temperature: Partial derivative of internal heat energy per unit mass with respect to temperature gradient Heat flow vector f, partial derivative of heat flow vector with respect to temperature Partial derivative of the heat flux vector with respect to the temperature gradient These variables are evaluated at every increment.

6. A three-dimensional thermal response analysis method for composite material reinforced wall panels according to claim 5, characterized in that: The expansion of the composite material thermal response control equation from one dimension to three dimensions includes expanding equation (1) and substituting it into equation (3) to obtain the three-dimensional heat transfer equation: The basic energy balance equation of heat transfer analysis is combined to obtain the expressions of variables such as U, DUDT, etc.

7. A three-dimensional thermal response analysis method for composite material reinforced wall panels according to claim 6, characterized in that: The calculation formula of the internal energy increase ΔU in the incremental step is: Partial derivative of internal heat energy per unit mass with respect to temperature The calculation formula is: Partial derivative of internal heat energy per unit mass with respect to temperature gradient The calculation formula is: The calculation formula of heat flow vector f is: Partial derivative of heat flux vector with respect to temperature The calculation formula is: Partial derivative of the heat flux vector with respect to the temperature gradient The calculation formula is:

8. A three-dimensional thermal response analysis method for composite material reinforced wall panels according to claim 7, characterized in that: The calculation formula for the initial condition and boundary condition of the thermal response calculation of the simulated composite material under single-side heating is as follows: Initial conditions: Heated surface boundary conditions: Backside thermal boundary condition: Where: q r ″ ad is the externally applied radiation heat flux, f(t) is the net heat flux of the heated surface, σ is the Boltzmann constant, T s , T back are the surface and back temperatures of the material, T ∞ is the ambient temperature, h front 、h back are the convective heat transfer coefficients on the surface and back of the material, and ε is the reflectivity of the material.

9. The three-dimensional thermal response analysis method of composite material reinforced wall panels according to claim 1, characterized in that: The expansion of the composite material thermal response control equation from one dimension to three dimensions is derived and implemented based on the ABAQUS user subroutines UMATHT and USDFLD writing rules, and is compiled and implemented using Fortran language codes on the Visual studio software platform.

10. The three-dimensional thermal response analysis method of composite material reinforced wall panels according to claim 1, characterized in that: The S3 step includes: S3.

1. Establish a composite material stiffened panel component model, including the flat plate, long stringer and web structure, and define the basic dimensions of the model; S3.

2. Set the material properties of the composite material stiffened panel component model. The model is a three-dimensional stiffened panel structure. Each component, such as the flat plate, web plate, and long stringer, sets the material properties and defines its own coordinate system separately to correspond to the subroutine. The density is set to be related to the carbonization rate field variable, and a non-independent variable option is added. The dimension of the state variable matrix defined and output is set; user-defined scenarios and user-defined material options are added; S3.

3. The connection method of each component of the model is defined in the interaction module. The connection method between the lower surface of the plate and the upper surface of the long stringer, and the lower surface of the long stringer and the upper surface of the web are all Tie connections; S3.

4. Create the first analysis step for heat transfer analysis. Set the time to the actual heating time. Both the initial time increment and the time increment are set to a fixed value of 1. In the field variable output requirement manager, the variable to be output is temperature. S3.

5. Setting the model boundary conditions, including convective heat transfer and radiation heat transfer on the material surface, wherein the convective heat transfer coefficient and the material reflectivity of the material are set; S3.

6. Apply a surface heat flux load that is consistent with reality; S3.7, based on the grid module, meshing the model; S3.

8. In the job module, when submitting a job, submit the written composite material thermal response subroutine in the user subroutine location, submit the calculation, and obtain the temperature response and thermal decomposition degree calculation results.

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