Method for measuring and calculating transient moisture-heat behavior of composite material based on moisture-heat coupling model

Abstract

The invention relates to a composite material transient moisture-heat behavior measuring and calculating method based on a moisture-heat coupling model, and the method comprises the steps: obtaining to-be-measured physical data of a uniform graphite epoxy composite material, the to-be-measured physical data comprising temperature, humidity and internal heat; inputting to-be-measured physical data into a moisture-heat coupling model based on an internal heat source to obtain transient moisture-heat behaviors of the uniform graphite epoxy composite material in an isotropic cylinder under the action of the internal heat source; the step of constructing the moisture-heat coupling model comprises the steps that dimensionless form conversion is carried out on a linear coupling model containing internal heat and a moisture source, parameters L1 and L2 are introduced into the model obtained after dimensionless form conversion, new functions h1 and h2 are used for replacing the model parameters, a satisfaction condition is determined, Hankel transformation and Laplace transformation are carried out on the satisfaction condition, and the moisture-heat coupling model is obtained. And obtaining a moisture-heat coupling model.

Description

Technical Field

[0001] The present invention relates to the technical field of materials science and engineering, and particularly to a method for calculating the transient moisture-heat behavior of composite materials based on a moisture-heat coupling model. Background Art

[0002] The urban heat island effect refers to the "high temperatureization" of cities due to factors such as a large amount of artificial heat generation, high heat storage bodies such as buildings and roads, and the reduction of green spaces.

[0003] Existing urban heat island effect analysis tools include: ground observation method, remote sensing monitoring method, numerical simulation method, and geographic information system (GIS) analysis method.

[0004] Ground observation method: Multiple meteorological observation stations are set up in urban and surrounding rural areas. Meteorological elements such as air temperature and humidity at different locations are directly measured through devices such as thermometers and hygrometers, and the temperature difference between the city and the suburbs is compared and analyzed to evaluate the intensity of the heat island effect. This method has high data accuracy, but there are problems such as limited site distribution and difficulty in comprehensively reflecting the spatial variation of the urban thermal environment.

[0005] Remote sensing monitoring method: Using thermal infrared sensors carried by satellite or aerial remote sensing platforms to obtain large-area surface temperature information and invert the distribution of the urban surface thermal field. It can quickly and widely monitor the spatial distribution and change trend of the urban heat island, but there are problems such as the surface temperature inversion accuracy being greatly affected by atmospheric conditions and difficulty in accurately obtaining the near-surface air temperature and humidity.

[0006] Numerical simulation method: Construct mathematical and physical models, such as computational fluid dynamics (CFD) models, urban canopy models (UCM), etc., considering factors such as the geometric structure of the city, underlying surface characteristics, and meteorological conditions, to numerically simulate the urban thermal environment and predict the intensity and distribution of the heat island effect. It can deeply analyze the formation mechanism of the heat island, but requires a large amount of basic data and complex parameter settings, resulting in high computational costs.

[0007] Geographic information system (GIS) analysis method: Combining spatial data such as the terrain, landform, land use, and building distribution of the city with meteorological data, and using the spatial analysis functions of GIS, such as buffer analysis and overlay analysis, to analyze the relationship between the urban heat island effect and various influencing factors. It can visually display the spatial distribution of the heat island effect and its correlation with related factors, but has high requirements for the integrity and accuracy of data and lacks the ability to real-time simulate the dynamic changes of the heat island.

[0008] Defects caused by the lack of a temperature-humidity coupling model in existing technical solutions include:

[0009] Inaccurate evaluation of heat island intensity: Temperature and humidity are important factors that are interrelated and jointly affect the urban thermal environment. The lack of a temperature-humidity coupling model and only considering temperature factors to evaluate heat island intensity will ignore the important role of humidity in human thermal sensation and urban heat balance. For example, in a high-humidity environment, even if the temperature is not particularly high, people will feel more stuffy, and the actual impact of the urban heat island effect will be more significant. However, without a temperature-humidity coupling model, this situation cannot be accurately reflected.

[0010] Inability to comprehensively analyze the heat island formation mechanism: Processes such as water evaporation and vegetation transpiration on the urban underlying surface affect air humidity and also interact with the heat transfer process. Without a temperature-humidity coupling model, it is difficult to accurately describe the impact of these processes on the formation and development of the urban heat island and comprehensively reveal the formation mechanism of the heat island effect. For example, water bodies and green spaces increase air humidity through evaporation and transpiration, and at the same time absorb and store heat, which has a mitigating effect on the urban heat island. However, the lack of a coupling model makes it impossible to accurately quantify this effect.

[0011] Limited prediction ability of the heat island effect: When predicting the urban heat island effect, the changing trends of temperature and humidity and their interaction are crucial for the prediction results. The lack of a temperature-humidity coupling model makes it impossible to consider the feedback effect of humidity changes on temperature and the coupling change law of temperature and humidity under different weather conditions and seasons, resulting in inaccurate prediction of the future development trend of the heat island effect. For example, during high-temperature periods in summer, the increase in humidity may further exacerbate the urban heat island effect, but without a coupling model, this situation cannot be predicted.

[0012] Lack of basis for urban planning and formulation of heat island mitigation measures: When formulating urban planning and heat island mitigation measures, it is necessary to comprehensively consider various factors such as temperature and humidity to optimize the urban layout, increase green spaces and water bodies, etc. Without a temperature-humidity coupling model, it is impossible to accurately evaluate the comprehensive impact of different planning schemes and mitigation measures on the urban temperature and humidity environment, and it is difficult to formulate scientific, reasonable and targeted urban planning and heat island mitigation strategies. Summary of the Invention

[0013] To solve the problems existing in the above-mentioned prior art, the object of the present invention is to provide a method for calculating the transient moisture-heat behavior of composite materials based on a moisture-heat coupling model. For isotropic and homogeneous graphite-epoxy composite material T300 / 5208, while experiencing transient thermal shock in the central ring, maintaining an adiabatic and moisture-proof outer surface, an exact solution is derived through Hankel transform and Laplace transform, the coupling and non-coupling effects of temperature, humidity and thermal stress are explored, and the mutual influence of temperature and humidity is comprehensively considered, which can more accurately evaluate the heat island intensity.

[0014] To achieve the above object, the present invention provides the following solutions:

[0015] Method for calculating transient moisture-heat behavior of composite materials based on moisture-heat coupling model, comprising:

[0016] Obtain the physical data to be measured of the homogeneous graphite epoxy composite material, where the physical data to be measured includes: temperature, humidity, and internal heat;

[0017] Input the physical data to be measured into the moisture-heat coupling model based on the internal heat source to obtain the transient moisture-heat behavior in the isotropic cylinder of the homogeneous graphite epoxy composite material under the action of the internal heat source;

[0018] Constructing the moisture-heat coupling model includes: performing a dimensionless form transformation on the linear coupling model containing internal heat and moisture sources, introducing parameters L1 and L2 into the transformed dimensionless form model respectively, and using new functions h1 and h2 to replace the model parameters, determining the satisfied conditions, performing Hankel transform and Laplace transform on the satisfied conditions to obtain the moisture-heat coupling model.

[0019] Optionally, obtaining the dimensionless form transformation of the linear coupling model containing internal heat and moisture sources includes:

[0020] Obtain the mass of water per unit mass of solid, and according to the mass of the water, combined with the mass conservation satisfied by the internal heating situation, determine the balance relationship between the net amount of water vapor entering and the voids and moisture in the solid under the action of the internal heat source, that is, the moisture transfer relationship:

[0021]

[0022] where D is the diffusion coefficient related to moisture flow, T is the temperature, w(r,t) is the moisture generated per cubic meter per second, is the Laplace operator, C is the amount of water vapor contained in the voids per unit volume, ρ is the density, v′ is the volume fraction of the voids, is the partial differential symbol, M is the mass of water in the unit solid, and t is the time;

[0023] Obtain the temperature distribution affected by the entering water, and according to the temperature distribution, combined with the non-Fourier heat conduction model, determine the heat transfer relationship:

[0024]

[0025] where, is the temperature gradient, K is the thermal conductivity, g(r,t) is the heat generated per cubic meter per second, C p is the specific heat capacity at constant pressure, is the heat released by the moisture per unit mass;

[0026] Based on the coupling relationship between the moisture transfer relationship and the heat transfer relationship, the linear coupling model including internal heat and moisture sources is obtained.

[0027] Optionally, the expression of the linear coupling model including internal heat and moisture sources is:

[0028]

[0029] where D h is the diffusion coefficient related to heat flow, D m is the diffusion coefficient related to moisture flow, k1 is the heat conduction coefficient, k2 is the moisture diffusion coefficient, η is the humidity coupling coefficient, θ is the temperature coupling coefficient, and τ is the relaxation time.

[0030] Optionally, the parameters L1 and L1 included in the transformed model in dimensionless form are:

[0031]

[0032] where, is the dimensionless temperature, ψ is the dimensionless humidity, g(ρ,t * ) is the dimensionless internal heat source, is the dimensionless heat conduction coefficient, t * is the dimensionless time, w(ρ,t * ) is the dimensionless internal moisture source, is the dimensionless moisture diffusion coefficient.

[0033] Optionally, the expressions of the parameters L1 and L2 are:

[0034]

[0035] where D h is the diffusion coefficient related to heat flow, D m is the diffusion coefficient related to moisture flow, η is the humidity coupling system, θ is the temperature coupling system;

[0036] The expressions of the new functions h1 and h2 are:

[0037]

[0038] where, is the dimensionless temperature, χ is the dimensionless humidity.

[0039] Optionally, determining the satisfaction of the conditions includes:

[0040]

[0041]

[0042] where ρ is the density and t * is the dimensionless time.

[0043] Optionally, performing the Hankel transform on the said satisfied conditions includes:

[0044] Setting the boundary conditions of the cylinder and substituting the boundary conditions into the new functions h1 and h2:

[0045]

[0046] where h1(R, t * ) is the first introduced new function, h2(R, t * ) is the second introduced new function, (R, t * ) are the radius coordinate and time coordinate at the boundary, is the initial value of the temperature, χ0(t * ) is the initial humidity;

[0047] Performing the Hankel transform on the said satisfied conditions according to the substituted new functions h1 and h2 includes:

[0048]

[0049] where is the square of the positive root of the transcendental equation, λ n is the positive root of the transcendental equation, J′0(λ n ) is the derivative of the zero-order Bessel function of the first kind, δ(t * - 0) is the step function, m1 is the coefficient related to the internal heat source, m2 is the parameter related to the internal moisture source, is, is, is the form after the Hankel transform of the first new function, τ * is the dimensionless relaxation time, is the form after the Hankel transform of the second new function.

[0050] Optionally, performing the Laplace transform on the satisfied conditions after the Hankel transform includes:

[0051]

[0052] where H1 is the form after the Laplace transform of the first new function after the Hankel transform, H2 is the form after the Laplace transform of the second new function after the Hankel transform, is the dimensionless temperature, χ0(t * ) is the dimensionless humidity, J1 is the Bessel function of the first kind of the first order, s is the time in the Laplace domain.

[0053] Optionally, obtaining the moisture-heat coupling model includes:

[0054]

[0055] wherein, is the dimensionless temperature after Laplace transform, is the dimensionless humidity after Laplace transform.

[0056] The beneficial effects of the present invention are as follows:

[0057] In order to overcome the technical deficiencies in the internal heat source and its hygrothermal coupling response of composite materials in the prior art, the present invention proposes a new hygrothermal coupling model for internal heat sources. By introducing methods such as multi-physical field coupling and multi-scale modeling, this model comprehensively considers the mutual influence of temperature and humidity and can more accurately evaluate the heat island intensity.

[0058] The present invention fully couples heat conduction, moisture diffusion, and mechanical response through the new model, considering the interaction between heat sources, moisture, and stress. By introducing non-linear coupling equations, the model can more accurately describe the dynamic changes of the temperature field, humidity field, and stress field of composite materials under the action of internal heat sources. This model can more realistically reflect the hygrothermal coupling behavior of composite materials in the actual use environment, especially in high-temperature and high-humidity environments, and significantly improve the prediction accuracy of temperature distribution and moisture penetration.

[0059] The present invention uses a multi-scale modeling method through the new model to comprehensively consider the hygrothermal coupling response of composite materials from the microscale (fibers and matrix) to the macroscale (overall structure). The microscale model is used to describe the hygrothermal behavior at the fiber-matrix interface, and the macroscale model is used to predict the performance changes of the overall structure. Multi-scale modeling enables the model to more comprehensively reflect the behavior of composite materials at different scales. Especially under the action of internal heat sources, the influence of microscale hygrothermal response on macroscale performance is accurately described.

[0060] When predicting the urban heat island effect, the changing trends of temperature and humidity and their interaction are crucial for the prediction results. The coupling model of the present invention can consider the feedback effect of humidity change on temperature and the coupling change rules of temperature and humidity under different weather conditions and seasons, thereby more accurately predicting the future development trend of the heat island effect. For example, during high-temperature periods in summer, the increase in humidity may further exacerbate the urban heat island effect, and the present invention can effectively predict this situation, while the prior art is limited by the lack of a coupling model and the prediction is inaccurate.

[0061] Provide a scientific basis for urban planning: When formulating urban planning and heat island mitigation measures, various factors such as temperature and humidity need to be comprehensively considered to optimize the urban layout, increase green spaces and water bodies, etc. The present invention can accurately evaluate the comprehensive impact of different planning schemes and mitigation measures on the urban temperature and humidity environment, providing a strong basis for formulating scientific, reasonable and targeted urban planning and heat island mitigation strategies. However, due to the lack of a coupling model, the prior art lacks sufficient basis in this regard.

[0062] By introducing mathematical methods such as dimensionless form transformation, Hankel transform, and Laplace transform, the present invention processes a linear coupling model containing internal heat and moisture sources, which can effectively simplify the calculation process and improve the calculation efficiency. At the same time, the application of these mathematical methods also helps to improve the solution accuracy and reliability of the model. In contrast, the prior art often requires a large amount of basic data and complex parameter settings in numerical simulation, resulting in high calculation costs and a lack of real-time simulation ability for the dynamic changes of the heat island. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0064] Figure 1 It is a flowchart of a method for measuring the transient moisture-heat behavior of a composite material based on a moisture-heat coupling model according to an embodiment of the present invention;

[0065] Figure 2 It is a cross-sectional view of an infinitely long solid cylinder under the action of a sudden wet-heat load according to an embodiment of the present invention;

[0066] Figure 3 It is the dimensionless temperature distribution at different dimensionless times t* after applying an internal heat source to a solid cylinder at a dimensionless relaxation time. (a) is the dimensionless temperature distribution at different dimensionless times t* after applying an internal heat source to a solid cylinder at a dimensionless relaxation time τ* = 0.2; (b) is the dimensionless temperature distribution at different dimensionless times t* after applying an internal heat source to a solid cylinder at a dimensionless relaxation time τ* = 2;

[0067] Figure 4The dimensionless humidity distribution of the solid cylinder in the embodiment of the present invention under internal action at dimensionless relaxation times, heat sources at four different dimensionless times t*; (a) shows the dimensionless radial displacement distribution of the solid cylinder under internal action at dimensionless relaxation time τ* = 0.2, heat sources at four different dimensionless times t*; (b) shows the dimensionless radial displacement distribution of the solid cylinder under internal action at dimensionless relaxation time τ* = 2, heat sources at four different dimensionless times t*. Detailed implementation manners

[0068] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0069] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0070] This embodiment discloses a method for calculating the transient moisture-heat behavior of a composite material based on a moisture-heat coupling model, including: constructing a moisture-heat coupling model based on an internal heat source by introducing an internal heat source to expand the non-Fourier and non-Fick hyperbolic models, for studying the transient moisture-heat behavior in an isotropic cylinder of a uniform graphite epoxy composite material T300 / 5208 under the action of an internal heat source. This model comprehensively explores the response of the interior of the cylinder when it is subjected to a transient thermal shock under external adiabatic and moisture-proof conditions. An exact solution is derived using Laplace transform and Not Hankel transform techniques. This embodiment analyzes the coupling and decoupling effects of temperature, moisture, and stress. This embodiment helps to more accurately predict the changes in the performance of the composite material under different environmental conditions, comprehensively considering the mutual influence of temperature and humidity, and can more accurately evaluate the intensity of the heat island.

[0071] The Dufour effect describes the phenomenon of heat flow generated by non-uniform moisture concentration in an isothermal solid. The ratio of heat flow to moisture flow is called the transport heat. The Soret effect or thermal diffusion involves the movement of moisture caused by non-uniform temperature inside the solid, although the moisture distribution in the solid is uniform. Therefore, the mass M of water per unit mass of the solid is expressed as follows:

[0072]

[0073] where T, C, ω are temperature, the amount of water vapor contained in the voids per unit volume, and material constants. Let the mass of water in the entire composite material be m:

[0074]

[0075] Among them, P is the material density, and v' is the void volume fraction.

[0076] Due to the influence of internal heating, a large amount of water entering the gap must satisfy the mass conservation:

[0077]

[0078] Among them, w(r, t) is the moisture generated per cubic meter per second, and q m is the moisture flux vector, which, according to the non-Fick's law, obeys:

[0079]

[0080] Among them, D is the diffusion coefficient related to moisture flow, and T is the relaxation time.

[0081] Eliminate q in Equation (3) m and Equation (4):

[0082]

[0083] Among them, represents the Laplace operator. This equation indicates that the net amount of water vapor entering the system under the action of the internal heat source must be balanced with the increase in voids and moisture in the solid.

[0084] Similarly, the temperature redistribution of the system can be obtained from the law of conservation of energy:

[0085]

[0086] Among them, C p is the specific heat capacity at constant pressure, that is, the heat released per unit mass of water vapor, and q h is the heat flux vector, which, according to the non-Fourier's law, that is, the non-Fourier heat conduction model proposed by Cattaneo and Vernotte, is given in the following form:

[0087]

[0088] Among them, represents the temperature gradient, K is the thermal conductivity, and g(r, t) is the heat generated per cubic meter per second. By substituting Equation (7) into Equation (6), we can obtain:

[0089]

[0090] Among them, for the two equations (5) and (8), the mass of moisture contained in each unit mass of solid is m. Therefore, heat and moisture transfer are coupled, and the quantity Thus, a linear coupled equation containing internal heat and moisture sources is obtained:

[0091]

[0092] Where:

[0093]

[0094] Referring to the Cartesian coordinate system O-rz, for simplicity, this embodiment considers an infinitely long cylinder as shown in Figure 2 The radius of the cylinder is such that r < R. It is assumed that the interior of the cylinder is suddenly affected by high temperature and humidity. At the same time, its outer surface is considered to have resistance to heat and moisture. It is assumed that temperature and humidity are coupled and they both change the elastic stress within the medium. Conversely, elastic deformation does not affect temperature and humidity.

[0095] The initial conditions of the hydrothermal conditions are as follows:

[0096] T(r; 0) = 0; C(r; 0) = 0; 0 < r < R; (13)

[0097] In addition, it is assumed that the temperature and humidity on the surface of the cylinder are the same as those of the ambient medium. Therefore, the temperature and humidity on the surface of the cylinder can be specified and these values will be reached:

[0098] T(R; t) = T0(t); C(R; t) = C0(t); t > 0; (14)

[0099] Where T0(t) and C0(t) are known functions that vary with time t.

[0100] To simplify equations (9) and (10), they can be rewritten in the following dimensionless form:

[0101]

[0102] Some of the dimensionless variables are made dimensionless as follows:

[0103]

[0104] Where and are the dimensionless temperature and humidity, respectively, with units of:

[0105]

[0106] Where T0 and C0 represent the reference temperature and water content in the initial state, while T ∞ and C ∞ represent the temperature and water content in the final equilibrium state, respectively.

[0107] By utilizing the established initial and boundary conditions (13)-(14), the relevant dimensionless form is derived as follows:

[0108] (P; 0) = 0; (P; 0) = 0; 0 < P < 1; (19)

[0109] The cylinder has the boundary conditions:

[0110] (1; t * ) = 0 (t * ); (1; t * ) = 0 (t * ); t * > 1; (20)

[0111] Since equations (15) and (16) are coupled, to decouple them, the parameter L1 is introduced.

[0112] By multiplying equation (15) by L1 and adding it to equation (16), the following is obtained:

[0113]

[0114] If a new unknown function is introduced, then:

[0115]

[0116] Satisfying the condition:

[0117]

[0118] The following relationship must be required:

[0119]

[0120] This gives:

[0121]

[0122] Similarly, introducing the parameter -L2, multiplying equation (15) by L2 and then adding the result to equation (16) gives:

[0123]

[0124] Similarly, introducing another new unknown function such that:

[0125]

[0126] Where:

[0127]

[0128] Next, use the new functions h1 and h2 to represent temperature and humidity;

[0129]

[0130] At the same time, by substituting the boundary conditions (20) into formulas (22) and (28), we obtain:

[0131]

[0132] By substituting the initial conditions (19) into formulas (22) and (28):

[0133] hi(p; 0) = 0; hi(p; 0) = 0; 0 < p < 1; i = 1; 2; (33)

[0134]

[0135] where g pi , w pi is the instantaneous heat source intensity.

[0136] To obtain the solutions of h1 and h2, the Hankel transform and its inverse transform on the range 0 < P < 1 of the variable P are introduced as follows:

[0137]

[0138] where the subscript i takes 1 and 2, corresponding to h1 and h2 respectively, and λn (n = 1; 2; 3...) are the positive roots of the transcendental equation

[0139] J0(λn) = 0; (37)

[0140] Recall the following properties:

[0141]

[0142] Under the boundary conditions (31) and (32), the Hankel transform of equations (23) and (27) is performed to obtain:

[0143]

[0144] where:

[0145]

[0146] Formulas (40) and (41) are second-order non-homogeneous differential equations. Apply the Laplace transform to solve them. Considering the initial conditions, apply the Laplace transform to equations (40) and (41):

[0147]

[0148]

[0149] After some simplifications, one obtains

[0150]

[0151] Next, equations (47) and (48), which are numerically inverse to each other after Hankel transform, yield the following results:

[0152]

[0153] Substitute the Hankel transform results of equations (47) and (48) into equations (49) and (50), and obtain:

[0154]

[0155] In a similar manner,

[0156]

[0157] The coupled equations (30) are transformed into the decoupled equations (53) and (54).

[0158] Therefore, the dimensionless temperature and humidity can be expressed in terms of H1 and H2:

[0159]

[0160] Results and Discussion:

[0161] This example illustrates the effects of temperature and humidity on the transient response of elastic displacement and stress of a thermal / moisture source in a solid cylinder. In the numerical calculation, to clarify the effects of temperature and humidity changes on the transient heat absorption elastic field of the thermal / moisture source inside the solid cylinder, the influence of the surface on the heat absorption impact is not considered in this example. Therefore, the material properties are adopted.

[0162] Initially, this example investigated the influence of internal heat sources on the transient response of a coupled thermoelastic hydrodynamic system, where P1 = 0.5; X = 0.5. Figure 3 and Figure 4 show the radial temperature and humidity distributions at different time intervals. In all the graphs, the solid lines represent the coupled conditions and the dashed lines represent the uncoupled conditions. Figure 3 (a) and 3(b) respectively show the dimensionless temperature distributions of the solid cylinder at four different dimensionless times t* with dimensionless relaxation times T* = 0.2 and T* = 2. According to previous studies, the obtained temperature distribution is affected by humidity changes and its associated thermal boundary conditions. Therefore, in this example, it is assumed that the temperature and humidity at the boundary are constant, and the cylinder is only affected by internal heat sources or moisture sources. Thus, asFigure 3 As shown, the interior of the solid cylinder is affected by a heat source, but the temperature at the boundary remains constant. From Figure 3 (a) and 3(b), it can be seen that in the initial stage of the solid cylinder, the temperature of the annular heat source P1 = 0.5, the temperature at the boundary remains constant, and the temperature at the center of the circle gradually increases with time. When the temperature reaches the maximum value, it begins to decrease and oscillates back and forth near zero until it reaches the equilibrium state. This is the result of the hydrothermal coupling effect. When the water absorption rate is positive (i.e., ), water acts as a heat source for the temperature distribution. Therefore, in the coupled state, the initial temperature is higher than that in the uncoupled state, and the difference between the two also gradually increases. When the water release rate is negative (i.e., ), water acts like a radiator. Therefore, over time, the temperature in the uncoupled state gradually becomes higher than that in the coupled state, and the difference between the two also gradually decreases until equilibrium is reached. By comparing Figure 3 (a) and 3(b), it can be seen that as the relaxation time increases, the time for the temperature to reach the peak will be later. The peak value is lower. This is due to the influence of the relaxation time on the speed. This further illustrates the unreasonableness at a finite speed. A similar conclusion can be drawn for water. Figure 4 (a) and 4(b) respectively describe the distribution of dimensionless wet urine at different time points when the relaxation time T* = 0.2 and T* = 2. From Figure 4 it can be seen that under the same conditions, the water response is more intense than the temperature in the coupled case. As Figure 4 shown, over time, the difference between these two scenarios becomes more and more obvious. This phenomenon is also affected by the humidity effect. In this coupled case, due to the increase in the evaporation rate, the temperature and water response at the center of the cylinder are faster. Compared with the uncoupled scenario, the internal humidity effect in the coupled scenario is more significant.

[0163] This embodiment proposes a linear hydrothermal coupling model with internal transient thermal shock. Through Hankel transform and Laplace transform techniques, an exact closed - form solution for the coupled changes of temperature and moisture in an infinitely long solid cylinder under thermal shock and moisture shock is obtained. Numerical results of graphite / epoxy composites are calculated and presented. The coupling effect between the temperature field and the moisture field is studied from the perspective of an internal transient heat source. Considering that the performance of T300 / 5208 may vary under different climatic conditions, the research results of the present invention should be considered when designing and analyzing under similar conditions. Generally speaking, this research provides valuable insights into the behavior of composites under the combined action of internal heat generation, temperature, and moisture.

[0164] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for calculating the transient moisture-heat behavior of a composite material based on a moisture-heat coupling model, characterized in that, Including: Obtaining the physical data to be measured of a homogeneous graphite epoxy composite material, where the physical data to be measured includes: temperature, humidity, and internal heat; Inputting the physical data to be measured into a moisture-heat coupling model based on an internal heat source to obtain the transient moisture-heat behavior in an isotropic cylinder of the homogeneous graphite epoxy composite material under the action of the internal heat source; Constructing the moisture-heat coupling model includes: performing a dimensionless form transformation on a linear coupling model containing internal heat and a moisture source, introducing parameters L1 and L2 into the model after the dimensionless form transformation respectively, and using new functions h1 and h2 to replace the model parameters, determining the conditions to be satisfied, performing Hankel transform and Laplace transform on the conditions to be satisfied, and obtaining the moisture-heat coupling model.

2. The transient moisture-heat behavior measurement method of the composite material based on the moisture-heat coupling model according to claim 1, wherein, Performing a dimensionless form transformation on the linear coupling model containing internal heat and a moisture source includes: Obtaining the mass of water in each unit mass of solid, and based on the mass of the water, combining with the mass conservation satisfied by the internal heating situation, determining the balance relationship between the net amount of water vapor entering and the voids and moisture in the solid under the action of the internal heat source, that is, the moisture transfer relationship: where D is the diffusion coefficient related to water flow, T is the temperature, w(r,t) is the water generated per cubic meter per second, is the Laplace operator, C is the amount of water vapor contained in the voids per unit volume, ρ is the density, v′ is the volume fraction of the voids, is the partial differential symbol, M is the mass of water in the unit solid, and t is the time; Obtaining the temperature distribution affected by the entering water, and based on the temperature distribution, combining with the non-Fourier heat conduction model, determining the heat transfer relationship: wherein, is the temperature gradient, K is the thermal conductivity, g(r,t) is the heat generated per cubic meter per second, C p is the specific heat capacity at constant pressure, is the heat released by the moisture per unit mass; Based on the coupling relationship between the moisture transfer relationship and the heat transfer relationship, obtaining the linear coupling model containing internal heat and a moisture source.

3. The transient moisture-heat behavior measurement method of the composite material based on the moisture-heat coupling model according to claim 2, wherein The expression of the linear coupling model containing internal heat and a moisture source is: where D h is the diffusion coefficient related to heat flow, D m is the diffusion coefficient related to moisture flow, k1 is the heat conduction coefficient, k2 is the moisture diffusion coefficient, η is the humidity coupling coefficient, θ is the temperature coupling coefficient, and τ is the relaxation time.

4. The transient moisture-heat behavior measurement method of the composite material based on the moisture-heat coupling model according to claim 1, characterized in that, Introducing parameters L1 and L1 into the model after the dimensionless form transformation respectively includes: Among them, is the dimensionless temperature, ψ is the dimensionless humidity, and g(ρ, t * ) is the dimensionless internal heat source, is the dimensionless heat conduction coefficient, t * is the dimensionless time, w(ρ, t * ) is the dimensionless internal moisture source, is the dimensionless moisture diffusion coefficient.

5. The method for measuring the transient moisture-heat behavior of a composite material based on a moisture-heat coupling model according to claim 1, characterized in that The expressions of the parameters L1 and L2 are: Among them, D h is the diffusion coefficient related to heat flow, D m is the diffusion coefficient related to moisture flow, η is the humidity coupling coefficient, and θ is the temperature coupling coefficient; The expressions of the new functions h1 and h2 are: where, is the dimensionless temperature, and χ is the dimensionless humidity.

6. The transient moisture-heat behavior measurement method of the composite material based on the moisture-heat coupling model according to claim 1, characterized in that, Determining the conditions to be satisfied includes: where ρ is the density and t * is the dimensionless time.

7. The transient moisture-heat behavior measurement method of the composite material based on the moisture-heat coupling model according to claim 1, characterized in that Performing a Hankel transform on the conditions to be satisfied includes: Setting the boundary conditions of the cylinder and substituting the boundary conditions into the new functions h1 and h2: where, h1(R, t * ) is the first newly introduced function, h2(R, t * ) is the second newly introduced function, (R, t * ) are the radius coordinate and time coordinate at the boundary, is the initial value of temperature, χ0(t * ) is the initial value of humidity; Based on the new functions h1 and h2 after substitution, performing a Hankel transform on the conditions to be satisfied includes: wherein, is the square of the positive root of the transcendental equation, λ n is the positive root of the transcendental equation, J′0(λ n ) is the derivative of the Bessel function of the first kind of order zero, δ(t * -0) is the step function, m1 is the coefficient related to the internal heat source, m2 is the parameter related to the internal moisture source, is the derivative of temperature with respect to time considering the relaxation time, is the derivative of humidity with respect to time considering the relaxation time, is the form after Hankel transform of the first new function, τ * is the dimensionless relaxation time, is the form after Hankel transform of the second new function.

8. The transient moisture-heat behavior measurement method of the composite material based on the moisture-heat coupling model according to claim 1, characterized in that Performing a Laplace transform on the conditions to be satisfied after Hankel transform includes: Among them, H1 is the form after the Hankel transform and then the Laplace transform of the first new function, and H2 is the form after the Hankel transform and then the Laplace transform of the second new function. is the dimensionless temperature, χ0(t * ) is the dimensionless humidity, J1 is the Bessel function of the first kind of the first order, and s is the time in the Laplace domain.

9. The transient moisture-heat behavior measurement method of the composite material based on the moisture-heat coupling model according to claim 1, characterized in that, Obtaining the moisture-heat coupling model includes: Among them, is the dimensionless temperature after Laplace transform, is the dimensionless humidity after Laplace transform.

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