Resin-based composite material thermophysical property multi-field coupling testing device and testing method

Abstract

The invention discloses a multi-field coupling testing device and method for thermophysical properties of a resin-based composite material, the device comprises a vacuum cavity, the vacuum cavity is connected with a vacuumizing device, an inert gas charging device and a water cooling unit, a heating unit is arranged in the vacuum cavity, the heating unit comprises a heat conduction block arranged above a workpiece platform, and the heat conduction block is connected with the vacuum cavity. A graphite heater is arranged on the upper surface of the heat conduction block in a contact mode and connected with a temperature control unit, and heat insulation plates are arranged around the graphite heater. A heat insulation device and a temperature measurement unit are arranged on the workpiece platform, the temperature measurement unit comprises a plurality of temperature measurement galvanic couples, the temperature measurement end of each temperature measurement galvanic couple is used for being inserted into a test piece, the wiring end of each temperature measurement galvanic couple is connected with a data acquisition unit, and an air pressure sensor is arranged on the vacuum cavity. According to the invention, through multi-field coupling and data inversion based on the physical information neural network, a high-precision and full-working-condition test means is provided for thermophysical parameters of the thermal protection material of the hypersonic aircraft.

Description

Technical Field

[0001] The invention relates to the field of hypersonic vehicle thermal protection testing, and in particular to a multi-field coupling testing device and a testing method for thermal properties of resin-based composite materials. Background Art

[0002] In the field of hypersonic vehicles, aerodynamic thermal issues are one of the key challenges. When hypersonic vehicles fly at high speeds in the atmosphere, they will face an extremely harsh aerodynamic thermal environment. In order to ensure the safe and stable operation of the aircraft, the thermal protection system is crucial, and resin-based composite materials have become the preferred thermal protection material for large areas of hypersonic aircraft due to their excellent thermal insulation properties. However, this type of material undergoes a complex pyrolysis reaction at high temperatures: the resin matrix decomposes to produce multi-component gases such as CO, CH4, and H2. The gases migrate in the pores and dynamically couple with the ambient pressure, resulting in thermal conductivity (k) and specific heat capacity (c p ) showed significant nonlinear characteristics.

[0003] In the prior art, a Chinese invention patent with announcement number CN107315030B discloses an "instrument and method for measuring thermal conductivity of a pyrolysis layer". Although the patent involves thermal conductivity measurement, the following problems exist during use: the invention requires the thermal conductivity of a carbonized layer to be known, but there is no detection method for the thermal conductivity of a carbonized layer containing pyrolysis gas, and all detection methods are based on the thermal conductivity of a carbonized layer without pyrolysis gas, resulting in a large error in the calculation of the equivalent thermal conductivity; the invention uses a heat flow meter on the back, and its error greatly reduces the accuracy of the measurement data; the flat plate sample of the invention is relatively thin, and the distance between the temperature measurement points in the thickness direction is limited, resulting in the implanted thermocouple affecting the measurement results of the material; the data inversion of the invention relies on a simplified heat transfer model, and there is computational instability during the inversion process, which further affects the accurate acquisition of the thermal properties of the material. Furthermore, the Chinese invention patent with publication number CN104407011A discloses "a test device and method for thermal diffusion coefficient based on laser flash method". Although the patent involves the measurement of thermal physical parameters, there are the following problems: the scheme assumes that the material composition is constant and does not consider the change in equivalent thermal conductivity caused by the generation of pyrolysis gas; in actual applications, the influence of pyrolysis gas on the thermal properties of the material cannot be ignored. In addition, the device does not integrate a pressure-controlled cavity and cannot simulate the influence of pressure on thermal properties in real flight. However, the Chinese invention patent with publication number CN106841297B discloses "a multifunctional solid material thermal property test device and method". Although the invention takes into account the influence of pressure, it does not avoid the oxidation reaction of oxygen on the material at high temperature, and does not involve the coupling effect of high-temperature pyrolysis gas and pressure. It is impossible to quantify the dynamic influence of pyrolysis gas on thermal conductivity, so the test range is limited. The invention is only applicable to the inherent thermal property test of solid materials and cannot reveal the dynamic changes of thermal properties during the pyrolysis reaction.

[0004] Therefore, the existing thermal property testing technology is difficult to accurately obtain the true thermal properties of resin-based composite materials for hypersonic vehicles under complex working conditions, and a new technology is urgently needed to break through this dilemma. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, detect the dynamic change data of the thermal properties of resin-based composite materials during high-temperature pyrolysis reaction, obtain the real thermal property parameters of resin-based thermal protection materials, and provide a multi-field coupling test device and test method for thermal properties of resin-based composite materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A multi-field coupling test device for thermal properties of resin-based composite materials, comprising a vacuum cavity, wherein the vacuum cavity is sealed and fastened to a vacuum cavity furnace door; the vacuum cavity is respectively connected to a vacuum pumping device and an inert gas charging device, and is used to make the vacuum cavity reach a set air pressure and an inert atmosphere; the vacuum cavity is also connected to a water cooling unit, and the water cooling unit is used to cool the vacuum cavity; a workpiece platform and a heating unit are arranged in the vacuum cavity, and the heating unit comprises a heat conducting block arranged above the workpiece platform, and a graphite heater is arranged in contact with the upper surface of the heat conducting block, and the graphite heater is connected to a temperature control unit; a heat insulating device and a temperature measuring unit are arranged on the workpiece platform, and the heat insulating device is used to cover a test piece; the temperature measuring unit comprises a plurality of temperature measuring couples, and the temperature measuring end of each of the temperature measuring couples is used to insert the test piece, and the wiring end of each of the temperature measuring couples is connected to a data acquisition unit; an air pressure sensor is arranged on the vacuum cavity, and the induction part of the air pressure sensor is inserted into the vacuum cavity, and the output end of the air pressure sensor is connected to the data acquisition unit.

[0007] The present invention realizes coupled regulation of pressure and temperature, simulates a real flight environment, and supports inert gas protection and low-pressure / high-pressure environment switching through the combination of a vacuum pumping device and an inert gas charging device, thereby avoiding oxidation interference of pyrolysis gas.

[0008] Preferably, the vacuum pump comprises a vacuum pump, and the vacuum pump is connected to an air outlet on the vacuum chamber through a vacuum pipe, and a vacuum valve is provided on the vacuum pipe.

[0009] Preferably, the inert gas filling device comprises an argon high-pressure storage tank, the gas outlet end of the argon high-pressure storage tank is connected to the gas inlet end of the mass flow controller, and the gas outlet end of the mass flow controller is connected to the gas inlet on the vacuum chamber through a filling pipe.

[0010] Preferably, the water cooling unit includes a water cooling pump and a water collecting row arranged in the vacuum chamber, a water cooling channel is arranged on the inner wall of the vacuum chamber, the water cooling channel is connected to the water inlet and the water outlet through the water collecting row, and the water inlet and the water outlet of the water cooling pump are respectively connected to the water outlet and the water inlet on the vacuum chamber.

[0011] Preferably, the temperature control unit includes a temperature control couple, a control module and a power adjustment unit, the temperature measuring end of the temperature control couple is arranged in the heat conductive block, the wiring end of the temperature control couple is connected to the control module, the output end of the control module is connected to the input end of the power adjustment unit, and the output end of the power adjustment unit is connected to the graphite heater through a water-cooled electrode.

[0012] Preferably, the control module includes a PID controller, a trigger circuit and an operation simulation screen, the input end of the PID controller is connected to the wiring terminal of the temperature control couple, the output end of the PID controller is connected to the input end of the trigger circuit, the output end of the trigger circuit is connected to the input end of the power regulation unit, the operation simulation screen is used to manually input set parameters, and the control input end of the PID controller is connected to the input end of the operation simulation screen.

[0013] Preferably, the multiple temperature measuring couples are respectively a top temperature measuring couple, an intermediate temperature measuring couple and a bottom temperature measuring couple, the upper half of the temperature measuring end of the top temperature measuring couple is embedded in the heat conductive block, the lower half of the temperature measuring end of the top temperature measuring couple is used to be embedded in the test piece, multiple intermediate temperature measuring couples are arranged along the axial direction of the test piece, the temperature measuring ends of the multiple intermediate temperature measuring couples are all used to be inserted into the test piece, the temperature measuring end of the bottom temperature measuring couple is arranged on the workpiece platform, and is used to contact the bottom of the test piece, and the wiring terminals of the top temperature measuring couple, the intermediate temperature measuring couple and the bottom temperature measuring couple are all connected to the data acquisition unit.

[0014] Preferably, a heat insulation plate is arranged around the graphite heater; the heat insulation device comprises an aerogel layer and an outer wall plate, the aerogel layer is used to wrap the test piece, and the outer wall plate is arranged outside the aerogel layer.

[0015] A multi-field coupling test method for thermophysical properties of resin-based composite materials, comprising: S1: Obtain temperature measurement data of multiple temperature measurement points of the test piece under set ambient pressure As a data set, where x and t are the position coordinate and time coordinate, respectively, i and j are the indexes of the position coordinate and time coordinate, respectively, and the multiple temperature measurement points include the top, bottom and middle positions of the test piece; S2: Data processing is performed based on the physical information neural network to obtain thermal conductivity parameters and specific heat capacity parameters, which specifically includes the following steps: S2.1: Construct a physical information neural network, a control equation and a total loss function, wherein the input of the physical information neural network includes the position coordinate x and the time coordinate t, and the output of the physical information neural network includes the temperature T, the density ρ of the resin-based composite material and the mass flow rate of the pyrolysis gas ; The control equation includes the energy equation of the resin-based composite material and the pyrolysis gas mass conservation equation. The formula of the energy equation of the resin-based composite material is as follows: Where ρ is the density of the resin-based composite material, c p is the specific heat capacity of the resin-based composite material, T is the temperature, k is the thermal conductivity of the resin-based composite material, Δh is the thermal decomposition heat, is the pyrolysis gas mass flow rate, c g is the specific heat capacity of pyrolysis gas, a3, a2, a1 and a0 are thermal conductivity parameters, b1 and b0 are specific heat capacity parameters; The formula of the pyrolysis gas mass conservation equation is as follows: Due to the thermal conductivity k and specific heat capacity c of resin-based composite materials p As a function of temperature, according to the chain rule: Where h is the enthalpy of the solid material, h g is the enthalpy of pyrolysis gas; The rate of density change caused by the pyrolysis reaction is calculated by the Arrhenius equation as follows: Among them, B is the pre-exponential factor, E is the reaction activation energy, R is the gas universal constant, ρ v and ρ c is the density of the original material and the complete carbonization, n is the reaction order; The total loss function includes a data-driven loss term and a physical information loss term.

[0016] S2.2: Combine the control equation and the loss function to train the physical information neural network. During the training process, the thermal conductivity parameters and specific heat capacity parameters to be identified are used together with the weights and biases of the physical information neural network as training parameters to participate in the training until the physical information neural network converges. The thermal conductivity parameters and specific heat capacity parameters identified by the trained physical information neural network are extracted. S3: Obtain the thermal conductivity k and specific heat c of the resin-based composite material under the set ambient pressure according to the thermal conductivity parameter and the specific heat capacity parameter. p .

[0017] Preferably, the data driven loss term L d The mean square error of the predicted temperature and the temperature measurement data of multiple temperature measurement points is calculated using the following formula: Among them, N d is the total number of temperature measurement points, T(x i ,t j ) is the temperature measurement point at (x i ,t j ) is the predicted temperature T, For multiple temperature measurement points Temperature measurement data at The physical information loss term L p Calculated by the control equation and initial conditions, the initial conditions include initial temperature T0 and initial density ρ0, physical information loss term L p The calculation formula is as follows: Among them, N p is the number of regional training points, N i is the number of initial condition training points; The total loss function L is: Among them, λ p is the weight corresponding to the physical information loss term, λ d is the weight corresponding to the data-driven loss term.

[0018] The testing method of the present invention can obtain the real temperature measurement data of the test points inside the material based on the experimental test, and use the physical information neural network to invert the thermal physical property parameters of the resin-based composite material. It is no longer dependent on the thermal conductivity of the carbonized layer and the original material layer, and the thermal physical property parameters are more realistic.

[0019] The present invention is based on the PINN model, replacing the traditional inversion calculation to solve the problem of inaccurate boundary parameters. The present invention solves the core problems of neglecting the pyrolysis gas effect and data model distortion in the prior art through multi-field coupling of temperature-pressure-gas and intelligent data inversion (PINN) based on physical information neural network, and provides a high-precision, full-condition testing method for the thermal physical parameters of hypersonic aircraft thermal protection materials. It has significant engineering application value and promotes the coordinated improvement of lightweight and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described in detail below in conjunction with the accompanying drawings: Figure 1 It is a schematic diagram of the structure of the device of the present invention; Figure 2 It is a schematic diagram of the connection structure between the vacuum chamber and the vacuum chamber furnace door of the device of the present invention; Figure 3 It is a schematic diagram of the internal structure of the vacuum chamber of the device of the present invention; Figure 4 It is a schematic diagram of the distribution of the temperature measuring ends of the temperature measuring couple of the device of the present invention; Figure 5 It is a schematic diagram of the lead distribution of the temperature measuring couple of the device of the present invention.

[0021] Figure 6 It is a connection diagram of the control module of the device of the present invention.

[0022] Explanation of the accompanying drawings: 1-water cooling pump, 2-vacuum chamber, 3-vacuum chamber furnace door, 301-sealing ring, 302-bolt fastening mechanism, 4-vacuum valve, 5-argon high-pressure storage tank, 6-vacuum pump, 7-vacuum through-hole, 8-wiring terminal of temperature measuring thermocouple, 9-data acquisition unit, 10-wiring terminal of temperature controlling thermocouple, 11-control module, 1101-trigger circuit, 1102-PID controller, 1103-operation simulation screen, 12-power adjustment unit, 13-temperature controlling thermocouple, 1401-first water-cooled electrode, 1402-second water-cooled electrode, 15-heat insulation board, 16-graphite heater, 17-heat conductive block, 18-test piece, 19-workpiece platform, 20-air pressure sensor. DETAILED DESCRIPTION

[0023] like Figure 1 As shown, a multi-field coupling test device for thermal properties of resin-based composite materials provided by the present invention comprises a vacuum chamber 2, which is sealed and fastened to a vacuum chamber furnace door 3. The vacuum chamber 2 is connected to the vacuum chamber furnace door 3 by a bolt fastening mechanism 302, and a sealing ring 301 is arranged on the edge of the vacuum chamber furnace door 3. Figure 2 As shown. The rubber sealing ring 301 is connected and pressure is applied by the bolt fastening mechanism 302 to make it close to the vacuum chamber 2 to achieve the purpose of sealing. The vacuum chamber 2 adopts a cavity water cooling structure, and the inner wall is sprayed with a thermal barrier coating.

[0024] The vacuum chamber 2 is connected to a vacuum pump and an inert gas filling device respectively, so as to achieve a set pressure and an inert atmosphere in the vacuum chamber 2. The vacuum pump includes a vacuum pump 6, which is connected to the gas outlet on the vacuum chamber 2 through a vacuum pipe, and a vacuum valve 4 is provided on the vacuum pipe. The vacuum pump 6 cooperates with the vacuum valve 4 to realize vacuuming, and the chamber pressure is reduced to 1×10 -1Pa, eliminate gas interference. The inert gas filling device includes an argon high-pressure storage tank 5, the outlet end of the argon high-pressure storage tank 5 is connected to the inlet end of the mass flow controller, and the outlet end of the mass flow controller is connected to the inlet on the vacuum chamber 2 through a filling pipe. Argon is injected into the vacuum chamber 2 through the mass flow controller to form an isothermal reference environment. The vacuum unit and the argon filling unit ensure that no oxidation reaction occurs during the material pyrolysis process to burn the test piece, avoid oxidation reaction or air interference measurement during the material pyrolysis process, and measure the air pressure data in the vacuum chamber 2 through the air pressure sensor 20.

[0025] The vacuum cavity 2 is also connected to a water cooling unit, which is used to cool the vacuum cavity 2. The water cooling unit includes a water cooling pump 1 and a water collecting row arranged in the vacuum cavity 2. A water cooling channel is arranged on the inner wall of the vacuum cavity 2. The water cooling channel is connected to the water inlet and the water outlet through the water collecting row. The water inlet and the water outlet of the water cooling pump 1 are connected to the water outlet and the water inlet on the vacuum cavity 2 respectively.

[0026] like Figure 3 As shown, a workpiece platform 19 and a heating unit are provided in the vacuum chamber 2. The heating unit includes a heat-conducting block 17 provided above the workpiece platform 19. The heat-conducting block 17 can be made of boron nitride or aluminum oxide insulating material. A graphite heater 16 is provided in contact with the upper surface of the heat-conducting block 17. The graphite heater 16 is connected to the power supply in the external circuit through the first water-cooled electrode 1401 and the second water-cooled electrode 1402. Hollow pipes are provided inside the first water-cooled electrode 1401 and the second water-cooled electrode 1402 for passing cooling water. The graphite heater 16 is also connected to the temperature control unit through the second water-cooled electrode 1402. A heat-insulating plate 15 is provided around the graphite heater 16. A heat-insulating device and a temperature measuring unit are provided on the workpiece platform 19. The heat-insulating device is used to cover the test piece 18. The heat-insulating device includes an aerogel layer and an outer wall plate. The aerogel layer is used to wrap the test piece 18, and the outer wall plate is provided outside the aerogel layer. The aerogel layer of the heat insulation device wraps the test piece 18, and an outer wall plate is added to force the pyrolysis gas to diffuse along the one-way channel. The workpiece platform 19 is connected to a mechanical adjustment mechanism, which is used to adjust the stroke of the workpiece platform 19.

[0027] The temperature measuring unit includes multiple temperature measuring couples, the temperature measuring end of each temperature measuring couple is used to insert the test piece 18, and the connection terminal 8 of each temperature measuring couple is connected to the data acquisition unit 9. A pressure sensor 20 is arranged on the vacuum cavity 2, and the sensing part of the pressure sensor 20 is inserted into the interior of the vacuum cavity 2, and the output end of the pressure sensor 20 is connected to the data acquisition unit 9. The multiple temperature measuring couples are respectively a top temperature measuring couple, an intermediate temperature measuring couple and a bottom temperature measuring couple. The upper half of the temperature measuring end of the top temperature measuring couple is embedded in the heat conducting block 17, and the lower half of the temperature measuring end of the top temperature measuring couple is used to be embedded in the test piece 18. Multiple intermediate temperature measuring couples are arranged along the axial direction of the test piece 18, and the temperature measuring ends of the multiple intermediate temperature measuring couples are all used to be inserted into the test piece 18. The temperature measuring end of the bottom temperature measuring couple is arranged on the workpiece platform 19, and is used to contact the bottom of the test piece 18. The leads of the top temperature measuring couple, the intermediate temperature measuring couple and the bottom temperature measuring couple pass through the vacuum chamber 2 through the vacuum through-hole 7, and the wiring terminals 8 of the top temperature measuring couple, the intermediate temperature measuring couple and the bottom temperature measuring couple are all connected to the data acquisition unit 9. The data acquisition unit 9 includes a collector, and the collector adopts an eight-way or above interface, and the output end of the collector is connected to the industrial control computer.

[0028] In this embodiment, Figure 4 and Figure 5 As shown, there are seven thermocouples, including a top thermocouple, five middle thermocouples and a bottom thermocouple. The temperature measuring ends of the seven thermocouples are inserted at equal intervals along the axial direction of the test piece 18, and the leads of the thermocouples are staggered to avoid contact between the thermocouples and affect data collection.

[0029] In this embodiment, the temperature control unit includes a temperature control couple 13, a control module 11 and a power adjustment unit 12. The power adjustment unit 12 adopts a thyristor power regulator. The temperature measuring end of the temperature control couple 13 is arranged in the heat conducting block 17, the connection terminal 10 of the temperature control couple 13 is connected to the control module 11, the output end of the control module 11 is connected to the input end of the power adjustment unit 12, and the output end of the power adjustment unit 12 is connected to the graphite heater 16 through the second water-cooled electrode 1402. Figure 6As shown, the control module 11 includes a PID controller 1102, a trigger circuit 1101 and an operation simulation screen 1103. The input end of the PID controller 1102 is connected to the terminal 10 of the temperature control thermocouple 13, the output end of the PID controller 1102 is connected to the input end of the trigger circuit 1101, the output end of the trigger circuit 1101 is connected to the input end of the power adjustment unit 12, the operation simulation screen 1103 is used to manually input the setting parameters, and the control input end of the PID controller 1102 is connected to the input end of the operation simulation screen 1103. The set temperature is input through the operation simulation screen 1103, and the set temperature value is sent to the PID controller 1102. The temperature control thermocouple 13 detects the real-time temperature in the heat conduction block 17 and feeds it back to the PID controller 1102. The PID controller 1102 compares the set temperature with the real-time temperature, calculates the error, and generates a control signal through the internal algorithm (proportional-integral-differential) of the PID controller 1102. The control signal output by the PID controller 1102 is transmitted to the trigger circuit 1101. The power regulating unit 12 adjusts the conduction angle or duty cycle according to the control signal, thereby adjusting the input power of the graphite heater 16 to make the temperature of the heat conducting block 17 approach the set value. The temperature control thermocouple 13 continuously feeds back the actual temperature, and the PID controller 1102 dynamically adjusts the output control signal according to the real-time data to form a closed-loop control.

[0030] Boron nitride heat conductive block 17 is used as a heat conductive control structure, and the upper and lower surfaces contact the upper surface of graphite heater 16 and test piece 18 respectively. The insulation strength of boron nitride can isolate the high voltage current of graphite heater 16 and avoid the risk of leakage between test piece 18 and heating unit.

[0031] The present invention realizes coupled regulation of pressure and temperature, simulates a real flight environment, and supports inert gas protection and low-pressure / high-pressure environment switching through the combination of a vacuum pumping device and an inert gas charging device, thereby avoiding oxidation interference of pyrolysis gas.

[0032] When the present invention is implemented, the following steps are performed: Step A: installing the heat insulation device on the test piece 18, that is, wrapping the aerogel layer on the outer layer of the test piece 18, and installing the outer wall panel on the outer side of the aerogel layer; Step B: Install seven temperature measuring couples on the test piece 18 through the outer wall plate and the aerogel layer; Step C: Fix the test piece 18 on the workpiece platform 19, and adjust the stroke of the workpiece platform 19 to make the test piece 18 closely contact with the surface of the heat conducting block 17; Step D: Connect the leads of seven temperature measuring couples to the vacuum feedthrough 7; Step E: Start the vacuum pump 6 to evacuate the vacuum chamber 2 and adjust the pressure to 1×10 -1 Pa, turn off the vacuum pump 6; Step F: Open the argon high-pressure storage tank 5, and accurately inject argon into the vacuum chamber 2 through the mass flow controller. When the set pressure is reached, stop injecting; Step G: The temperature is raised by the graphite heater 16 and the temperature is controlled by the control module 11 within ±1°C. When the top temperature of the test piece 18 reaches 800°C and the bottom temperature rises to 50°C, the heating power is cut off and the heating is stopped; Step H: During the heating process, the data acquisition unit 9 synchronously records the temperature measurement data of the seven temperature measuring points where the thermocouples are located. and the air pressure data in the vacuum chamber 2 measured by the air pressure sensor 20; Step I: After completing data collection, release the gas pressure in the vacuum chamber 2 to normal pressure, and end the test.

[0033] Step J: Obtain the temperature measurement data of the temperature measurement point under a certain ambient pressure through the above test , data processing is carried out based on the multi-field coupling test method of thermal physical properties of resin-based composite materials.

[0034] The present invention realizes pressure-temperature coupling regulation and simulates the real flight environment. By combining the argon pressurization device with the vacuum unit, it supports inert gas protection and low-pressure / high-pressure environment switching to avoid oxidative interference of pyrolysis gas.

[0035] The present invention also provides a multi-field coupling test method for thermal properties of resin-based composite materials, comprising the following steps: S1: Obtain temperature measurement data of multiple temperature measurement points of the test piece under set ambient pressure As a data set, x and t are the position coordinate and time coordinate respectively, i and j are the indexes of the position coordinate and time coordinate respectively, and multiple temperature measurement points include the top, bottom and middle positions of the test piece.

[0036] S2: Perform data processing based on physical information neural network to obtain thermal conductivity parameters and specific heat capacity parameters. Specifically, it includes the following steps: S2.1: Construct a physical information neural network, control equations and total loss function. The input of the physical information neural network includes the position coordinate x and the time coordinate t. The output of the physical information neural network includes the temperature T, the density ρ of the resin-based composite material and the mass flow rate of the pyrolysis gas. .

[0037] The control equations include the energy equation of the resin-based composite material and the pyrolysis gas mass conservation equation. The formula of the energy equation of the resin-based composite material is as follows: Where ρ is the density of the resin-based composite material, c pis the specific heat capacity of the resin-based composite material, T is the temperature, k is the thermal conductivity of the resin-based composite material, Δh is the thermal decomposition heat, is the pyrolysis gas mass flow rate, c g is the specific heat capacity of pyrolysis gas.

[0038] The thermal conductivity k and specific heat capacity c of the resin-based composite material p The polynomials are fitted as follows: Among them, a3, a2, a1 and a0 are thermal conductivity parameters, and b1 and b0 are specific heat capacity parameters.

[0039] The formula of the pyrolysis gas mass conservation equation is as follows: Due to the thermal conductivity k and specific heat capacity c of resin-based composite materials p As a function of temperature, according to the chain rule: Where h is the enthalpy of the solid material, h g is the enthalpy of pyrolysis gas.

[0040] The rate of density change caused by the pyrolysis reaction is calculated by the Arrhenius equation as follows: Among them, B is the pre-exponential factor, E is the reaction activation energy, R is the gas universal constant, ρ v and ρ c is the density of the original material and the complete carbonization, and n is the reaction order.

[0041] The total loss function includes data-driven loss term and physical information loss term. The data-driven loss term L is defined as d The mean square error of the predicted temperature and the temperature measurement data of multiple temperature measurement points is calculated using the following formula: Among them, N d is the total number of temperature measurement points, T(x i ,t j ) is the temperature measurement point at (x i ,t j ) is the predicted temperature T, For multiple temperature measurement points Temperature measurement data at.

[0042] In this embodiment, the boundary conditions are provided by the measurement data of the temperature measurement points at the top and bottom of the test piece, which are already included in L d middle.

[0043] Define the physical information loss term L p Calculated by the control equation and initial conditions, including initial temperature T0 and initial density ρ0, physical information loss term L p The calculation formula is as follows: Among them, N p is the number of regional training points, N i is the number of initial condition training points.

[0044] The total loss function L is: Among them, λ p is the weight corresponding to the physical information loss term, λ d is the weight corresponding to the data-driven loss term.

[0045] S2.2: Combine the control equation and the loss function to train the physical information neural network. During the training process, the thermal conductivity parameters and specific heat capacity parameters that need to be identified are used together with the weights and biases of the physical information neural network as training parameters to participate in the training until the physical information neural network converges. The thermal conductivity parameters and specific heat capacity parameters identified by the trained physical information neural network are extracted.

[0046] The gradient descent method is used to train the physical information neural network. The specific formula is: Among them, η is the learning rate, θ a are the training parameters of the physical information neural network in the ath iteration.

[0047] S3: Obtain the thermal conductivity k and specific heat c of the resin-based composite material under the set ambient pressure according to the thermal conductivity parameter and the specific heat capacity parameter. p .

[0048] The testing method of the present invention can obtain the real temperature measurement data of the test points inside the material based on the experimental test, and use the physical information neural network to invert the thermal physical property parameters of the resin-based composite material. It is no longer dependent on the thermal conductivity of the carbonized layer and the original material layer, and the thermal physical property parameters are more realistic.

[0049] The present invention is based on the PINN model, replacing the traditional inversion calculation to solve the problem of inaccurate boundary parameters. The present invention solves the core problems of neglecting the pyrolysis gas effect and data model distortion in the prior art through multi-field coupling of temperature-pressure-gas and intelligent data inversion (PINN) based on physical information neural network, and provides a high-precision, full-condition testing method for the thermal physical parameters of hypersonic aircraft thermal protection materials. It has significant engineering application value and promotes the coordinated improvement of lightweight and reliability.

[0050] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

Claims

1. A multi-field coupling test device for thermal properties of resin-based composite materials, characterized in that: The invention comprises a vacuum chamber, wherein the vacuum chamber is sealed and fastened to a vacuum chamber furnace door; the vacuum chamber is respectively connected to a vacuum pumping device and an inert gas charging device, so as to make the vacuum chamber reach a set air pressure and an inert atmosphere; the vacuum chamber is also connected to a water cooling unit, and the water cooling unit is used to cool the vacuum chamber; a workpiece platform and a heating unit are arranged in the vacuum chamber; the heating unit comprises a heat conducting block arranged above the workpiece platform, a graphite heater is arranged in contact with the upper surface of the heat conducting block, and the graphite heater is connected to a temperature control unit; a heat insulating device and a temperature measuring unit are arranged on the workpiece platform, and the heat insulating device is used to cover a test piece; the temperature measuring unit comprises a plurality of temperature measuring couples, and the temperature measuring end of each temperature measuring couple is used to insert a test piece, and the wiring end of each temperature measuring couple is connected to a data acquisition unit; an air pressure sensor is arranged on the vacuum chamber, and the sensing part of the air pressure sensor is inserted into the interior of the vacuum chamber, and the output end of the air pressure sensor is connected to the data acquisition unit.

2. The multi-field coupling test device for thermal properties of resin-based composite materials according to claim 1, characterized in that: The vacuum pump comprises a vacuum pump, which is connected to an air outlet on the vacuum chamber through a vacuum pipe, and a vacuum valve is arranged on the vacuum pipe.

3. The multi-field coupling test device for thermophysical properties of resin-based composite materials according to claim 1, characterized in that: The inert gas filling device comprises an argon high-pressure storage tank, the gas outlet end of the argon high-pressure storage tank is connected to the gas inlet end of the mass flow controller, and the gas outlet end of the mass flow controller is connected to the gas inlet on the vacuum chamber through a filling pipeline.

4. The multi-field coupling test device for thermophysical properties of resin-based composite materials according to claim 1, characterized in that: The water cooling unit includes a water cooling pump and a water collecting row arranged in the vacuum chamber. A water cooling channel is arranged on the inner wall of the vacuum chamber. The water cooling channel is connected to the water inlet and the water outlet through the water collecting row. The water inlet and the water outlet of the water cooling pump are respectively connected to the water outlet and the water inlet on the vacuum chamber.

5. The multi-field coupling test device for thermophysical properties of resin-based composite materials according to claim 1, characterized in that: The temperature control unit includes a temperature control couple, a control module and a power adjustment unit. The temperature measuring end of the temperature control couple is arranged in the heat conductive block, the connection end of the temperature control couple is connected to the control module, the output end of the control module is connected to the input end of the power adjustment unit, and the output end of the power adjustment unit is connected to the graphite heater through a water-cooled electrode.

6. The multi-field coupling test device for thermophysical properties of resin-based composite materials according to claim 5, characterized in that: The control module includes a PID controller, a trigger circuit and an operation simulation screen. The input end of the PID controller is connected to the wiring terminal of the temperature control thermocouple, the output end of the PID controller is connected to the input end of the trigger circuit, the output end of the trigger circuit is connected to the input end of the power adjustment unit, the operation simulation screen is used to manually input setting parameters, and the control input end of the PID controller is connected to the input end of the operation simulation screen.

7. The multi-field coupling test device for thermophysical properties of resin-based composite materials according to claim 1, characterized in that: The multiple temperature measuring couples are respectively a top temperature measuring couple, an intermediate temperature measuring couple and a bottom temperature measuring couple. The upper half of the temperature measuring end of the top temperature measuring couple is embedded in the heat conductive block, and the lower half of the temperature measuring end of the top temperature measuring couple is used to be embedded in the test piece. Multiple intermediate temperature measuring couples are arranged along the axial direction of the test piece, and the temperature measuring ends of the multiple intermediate temperature measuring couples are all used to be inserted into the test piece. The temperature measuring end of the bottom temperature measuring couple is arranged on the workpiece platform for contacting the bottom of the test piece. The wiring terminals of the top temperature measuring couple, the intermediate temperature measuring couple and the bottom temperature measuring couple are all connected to the data acquisition unit.

8. The multi-field coupling test device for thermophysical properties of resin-based composite materials according to claim 1, characterized in that: A heat insulation plate is arranged around the graphite heater, and the heat insulation device comprises an aerogel layer and an outer wall plate. The aerogel layer is used to wrap the test piece, and the outer wall plate is arranged outside the aerogel layer.

9. A multi-field coupling test method for thermal properties of resin-based composite materials, characterized in that: include: S1: Obtain temperature measurement data of multiple temperature measurement points of the test piece under set ambient pressure As a data set, where x and t are the position coordinate and time coordinate, respectively, i and j are the indexes of the position coordinate and time coordinate, respectively, and the multiple temperature measurement points include the top, bottom and middle positions of the test piece; S2: Data processing is performed based on the physical information neural network to obtain thermal conductivity parameters and specific heat capacity parameters, which specifically includes the following steps: S2.1: Construct a physical information neural network, a control equation and a total loss function, wherein the input of the physical information neural network includes the position coordinate x and the time coordinate t, and the output of the physical information neural network includes the temperature T, the density ρ of the resin-based composite material and the mass flow rate of the pyrolysis gas ; The control equation includes the energy equation of the resin-based composite material and the pyrolysis gas mass conservation equation. The formula of the energy equation of the resin-based composite material is as follows: ； ； Where ρ is the density of the resin-based composite material, c p is the specific heat capacity of the resin-based composite material, T is the temperature, k is the thermal conductivity of the resin-based composite material, Δh is the thermal decomposition heat, is the pyrolysis gas mass flow rate, c g is the specific heat capacity of pyrolysis gas, a3, a2, a1 and a0 are thermal conductivity parameters, b1 and b0 are specific heat capacity parameters; The formula of the pyrolysis gas mass conservation equation is as follows: ； Due to the thermal conductivity k and specific heat capacity c of resin-based composite materials p As a function of temperature, according to the chain rule: ； Where h is the enthalpy of the solid material, h g is the enthalpy of pyrolysis gas; The rate of density change caused by the pyrolysis reaction is calculated by the Arrhenius equation as follows: ； Among them, B is the pre-exponential factor, E is the reaction activation energy, R is the gas universal constant, ρ v and ρ c is the density of the original material and the complete carbonization, n is the reaction order; The total loss function includes a data-driven loss term and a physical information loss term; S2.2: Combine the control equation and the loss function to train the physical information neural network. During the training process, the thermal conductivity parameters and specific heat capacity parameters to be identified are used together with the weights and biases of the physical information neural network as training parameters to participate in the training until the physical information neural network converges. The thermal conductivity parameters and specific heat capacity parameters identified by the trained physical information neural network are extracted. S3: Obtain the thermal conductivity k and specific heat c of the resin-based composite material under the set ambient pressure according to the thermal conductivity parameter and the specific heat capacity parameter. p .

10. The multi-field coupling test method for thermal properties of resin-based composite materials according to claim 9, characterized in that: The data-driven loss term L described in step S2.1 d The mean square error of the predicted temperature and the temperature measurement data of multiple temperature measurement points is calculated using the following formula: ； Among them, N d is the total number of temperature measurement points, T(x i, t j ) is the temperature measurement point at (x i, t j ) is the predicted temperature T, For multiple temperature measurement points Temperature measurement data at The physical information loss term L p Calculated by the control equation and initial conditions, the initial conditions include initial temperature T0 and initial density ρ0, the physical information loss term L p The calculation formula is as follows: ； Among them, N p is the number of regional training points, N i is the number of initial condition training points; The total loss function L is: ； Among them, λ p is the weight corresponding to the physical information loss term, λ d is the weight corresponding to the data-driven loss term.

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