A multi-field coupling test device and test method for the thermal properties of resin-based composites

Abstract

The present invention discloses a multi-field coupling test device and a test method for the thermal properties of resin-based composites. The device includes a vacuum chamber, which is respectively connected to a vacuum pumping device, an inert gas filling device, and a water cooling unit. A heating unit is arranged inside the vacuum chamber. The heating unit includes a heat conducting block arranged above the workpiece platform. A graphite heater is in contact with the upper surface of the heat conducting block. The graphite heater is connected to a temperature control unit, and a heat insulation plate is arranged around the graphite heater. An insulation device and a temperature measurement unit are arranged on the workpiece platform. The temperature measurement unit includes a plurality of temperature measurement thermocouples. The temperature measurement end of each temperature measurement thermocouple is used to insert into the test piece, and the wiring end of each temperature measurement thermocouple is connected to a data acquisition unit. A pressure sensor is arranged on the vacuum chamber. The present invention provides a high-precision and full-condition test means for the thermal property parameters of the thermal protection materials of hypersonic aircraft through multi-field coupling and data inversion based on a physics-informed neural network.

Description

Technical Field

[0001] The present invention relates to the field of hypersonic vehicle thermal protection testing, and particularly to a multi-field coupling testing device and method for the thermal physical properties of resin matrix composites. Background Art

[0002] In the field of hypersonic vehicles, the aerodynamic heat problem is one of the key challenges. When a hypersonic vehicle flies at high speed in the atmosphere, it will face an extremely harsh aerodynamic heat environment. To ensure the safe and stable operation of the vehicle, the thermal protection system is crucial. Resin matrix composites, with their excellent heat insulation performance, have become the preferred thermal protection materials for large areas of hypersonic vehicles. However, such materials undergo complex pyrolysis reactions 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 are dynamically coupled with the ambient pressure, resulting in significant non-linear characteristics of the thermal conductivity (k) and specific heat capacity (c p ).

[0003] In the prior art, the Chinese invention patent with the publication number CN107315030B discloses a "thermal conductivity measurement instrument and method for pyrolysis layer". Although this patent is related to the measurement of thermal conductivity, there are the following problems in the use process: this invention requires the known thermal conductivity of the carbonized layer, but there is no detection method for the thermal conductivity of the carbonized layer containing pyrolysis gases, and they are all the thermal conductivities of the carbonized layers without pyrolysis gases, resulting in a large calculation error of the equivalent thermal conductivity; a heat flux meter is used on the back of this invention, and its error greatly reduces the accuracy of the measurement data; the thickness of the flat sample of this invention is relatively thin, and the arrangement distance between the temperature measurement points in the thickness direction is limited, resulting in the implanted thermocouples affecting the measurement results of the material; the data inversion of this invention relies on a simplified heat transfer model, and there are calculation instability phenomena during the inversion process, further affecting the accurate acquisition of the thermal physical properties of the material. Further, the Chinese invention patent with the publication number CN104407011A discloses a "testing device and method for thermal diffusivity based on the laser flash method". Although this patent is related to the measurement of thermal physical parameters, there are the following problems: this scheme defaults that the material composition is constant and does not consider the change of equivalent thermal conductivity caused by the generation of pyrolysis gases; in actual applications, the influence of pyrolysis gases on the thermal physical properties of materials cannot be ignored. In addition, this device does not integrate a pressure controllable cavity and cannot simulate the influence of pressure on thermal physical properties during actual flight. However, the Chinese invention patent with the publication number CN106841297B discloses a "multi-functional solid material thermal physical property testing device and method". Although this invention considers the influence of pressure, it does not avoid the oxidation reaction of oxygen on the material at high temperatures, and does not involve the coupling effect of high-temperature pyrolysis gases and pressure, and cannot quantify the dynamic influence of pyrolysis gases on thermal conductivity. Therefore, the testing range is limited, and this invention is only applicable to the testing of the inherent thermal physical properties of solid materials and cannot reveal the dynamic changes of thermal physical properties during the pyrolysis reaction.

[0004] Therefore, it is difficult for existing thermal property testing technologies to accurately obtain the true thermal properties of resin matrix composites for hypersonic vehicles under complex working conditions. There is an urgent need for a new technology to break through this dilemma. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned disadvantages of the existing technologies, detect the dynamic change data of the thermal properties during the high-temperature pyrolysis reaction of resin matrix composites, obtain the true thermal property parameters of resin-based thermal protection materials, and provide a multi-field coupling testing device and testing method for the thermal properties of resin matrix composites.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A multi-field coupling testing device for the thermal properties of resin matrix composites includes a vacuum chamber, which is sealed and fastened to a vacuum chamber door; the vacuum chamber is respectively connected to a vacuum pumping device and an inert gas filling device for achieving a set air pressure and inert atmosphere in the vacuum chamber. The vacuum chamber is also connected to a water cooling unit for cooling the vacuum chamber. A workpiece platform and a heating unit are arranged in the vacuum chamber. The heating unit includes a heat conduction block arranged above the workpiece platform, and a graphite heater is in contact with the upper surface of the heat conduction block. The graphite heater is connected to a temperature control unit. An insulation device and a temperature measurement unit are arranged on the workpiece platform. The insulation device is used to wrap the test piece. The temperature measurement unit includes a plurality of thermocouples. The temperature measurement end of each thermocouple is used to insert into the test piece, and the wiring end of each thermocouple is connected to a data acquisition unit. A pressure sensor is arranged on the vacuum chamber, and the sensing part of the pressure sensor is inserted into the interior of the vacuum chamber. The output end of the pressure sensor is connected to the data acquisition unit.

[0008] The present invention realizes the coupled regulation of pressure and temperature, simulates the real flight environment, and through the combination of a vacuum pumping device and an inert gas filling device, supports the switching between inert gas protection and low-pressure / high-pressure environments to avoid the interference of pyrolysis gas oxidation.

[0009] Preferably, the vacuum pumping device includes a vacuum pump, and the vacuum pump is connected to the air outlet on the vacuum chamber through a vacuum pipeline. A vacuum valve is arranged on the vacuum pipeline.

[0010] Preferably, the inert gas filling device includes an argon high-pressure storage tank. The air outlet end of the argon high-pressure storage tank is connected to the air inlet end of a mass flow controller. The air outlet end of the mass flow controller is connected to the air inlet on the vacuum chamber through a filling pipeline.

[0011] Preferably, the water cooling unit includes a water cooling pump and a water collection drain disposed in the vacuum chamber. A water cooling channel is provided 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 collection drain. 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.

[0012] Preferably, the temperature control unit includes a temperature control thermocouple, a control module, and a power regulation unit. The temperature measuring end of the temperature control thermocouple is disposed in the heat conducting block. The wiring end of the temperature control thermocouple is connected to the control module. The output end of the control module is connected to the input end of the power regulation unit. The output end of the power regulation unit is connected to the graphite heater through a water cooling electrode.

[0013] 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 end 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 regulation unit. The operation simulation screen is used for manually inputting set parameters. The control input end of the PID controller is connected to the input end of the operation simulation screen.

[0014] Preferably, the plurality of temperature measuring thermocouples are respectively a top temperature measuring thermocouple, a middle temperature measuring thermocouple, and a bottom temperature measuring thermocouple. The upper half of the temperature measuring end of the top temperature measuring thermocouple is embedded in the heat conducting block. The lower half of the temperature measuring end of the top temperature measuring thermocouple is used for embedding the test piece. A plurality of middle temperature measuring thermocouples are arranged along the axial direction of the test piece. The temperature measuring ends of the plurality of middle temperature measuring thermocouples are all used for inserting into the test piece. The temperature measuring end of the bottom temperature measuring thermocouple is disposed on the workpiece platform for contacting the bottom of the test piece. The wiring ends of the top temperature measuring thermocouple, the middle temperature measuring thermocouple, and the bottom temperature measuring thermocouple are all connected to the data acquisition unit.

[0015] Preferably, a heat insulation board is disposed around the graphite heater; the heat insulation device includes an aerogel layer and an outer wall board. The aerogel layer is used for wrapping the test piece. The outer wall board is disposed outside the aerogel layer.

[0016] A method for multi-field coupling testing of thermophysical properties of resin matrix composites includes:

[0017] S1: Obtain temperature measurement data of multiple temperature measurement points of the test piece under a set ambient air pressure As a data set, where x and t are respectively the position coordinates and the time coordinate, and i, j are respectively the indexes of the position coordinate and the time coordinate. The multiple temperature measurement points include the top, bottom, and middle positions of the test piece;

[0018] S2: Perform data processing based on a physics-informed neural network to obtain the thermal conductivity parameter and the specific heat capacity parameter, specifically including the following steps:

[0019] S2.1: Construct a physics-informed neural network, control equations, and a total loss function. The input of the physics-informed neural network includes the position coordinate x and the time coordinate t, and the output of the physics-informed neural network includes the temperature T, the density ρ of the resin matrix composite, and the pyrolysis gas mass flow rate. ;

[0020] The control equations include the energy equation of the resin matrix composite and the pyrolysis gas mass conservation equation. The formula of the energy equation of the resin matrix composite is as follows:

[0021]

[0022]

[0023]

[0024] where ρ is the density of the resin matrix composite, c p is the specific heat capacity of the resin matrix composite, T is the temperature, k is the thermal conductivity of the resin matrix composite, Δh is the heat of pyrolysis, is the pyrolysis gas mass flow rate, c g is the specific heat capacity of the pyrolysis gas, a3, a2, a1, and a0 are thermal conductivity parameters, and b1 and b0 are specific heat capacity parameters;

[0025] The formula of the pyrolysis gas mass conservation equation is as follows:

[0026]

[0027] Since the thermal conductivity k and the specific heat capacity c p of the resin matrix composite are functions of temperature, according to the chain rule:

[0028]

[0029] where h is the enthalpy value of the solid material, h g is the enthalpy value of the pyrolysis gas;

[0030] The density change rate caused by the pyrolysis reaction is calculated by the Arrhenius equation, and the formula is as follows:

[0031]

[0032] where B is the pre-exponential factor, E is the activation energy of the reaction, R is the universal gas constant, ρ v and ρ c are the densities of the original material and the completely carbonized material, and n is the reaction order;

[0033] The total loss function includes a data-driven loss term and a physics-informed loss term.

[0034] S2.2: Combine the governing equations with the loss function to train the physics-informed neural network. During the training process, the thermal conductivity parameter, specific heat capacity parameter to be identified, and the weights and biases of the physics-informed neural network are jointly used as training parameters to participate in the training until the physics-informed neural network converges, and then extract the thermal conductivity parameter and specific heat capacity parameter identified by the trained physics-informed neural network.

[0035] S3: Obtain the thermal conductivity k and specific heat capacity c of the resin matrix composite under the set environmental air pressure according to the thermal conductivity parameter and specific heat capacity parameter. p 。

[0036] Preferably, the data-driven loss term L d is calculated from the mean square error between the predicted temperature and the temperature measurement data at multiple temperature measurement points. The formula is as follows:

[0037]

[0038] where N d is the total number of temperature measurement points, T(x i ,t j ) is the predicted temperature T at the temperature measurement point at (x i ,t j ), and is the temperature measurement data at multiple temperature measurement points at .

[0039] The physics-informed loss term L p is calculated from the governing equations and initial conditions. The initial conditions include the initial temperature T0 and the initial density ρ0. The calculation formula of the physics-informed loss term L p is as follows:

[0040]

[0041] where N p is the number of regional training points, and N i is the number of initial condition training points.

[0042] The total loss function L is:

[0043]

[0044] where λ p is the weight corresponding to the physics-informed loss term, and λ d is the weight corresponding to the data-driven loss term.

[0045] The test method of the present invention can obtain the true temperature measurement data of the internal test points of the material based on experimental tests, and use the physics-informed neural network to invert the thermal physical properties of the resin matrix composite material, without relying on the thermal conductivity of the carbonized layer and the original material layer, and the thermal physical properties are more real.

[0046] Based on the PINN model, the present invention replaces the traditional inversion calculation and solves the problem of inaccurate boundary parameters relied on. Through the multi-field coupling of temperature-pressure-gas and the intelligent data inversion based on the physics-informed neural network (PINN), the present invention solves the core problems such as the neglect of the pyrolysis gas effect and the distortion of the data model in the prior art, provides a high-precision and full-condition test method for the thermal physical properties of the thermal protection materials of hypersonic vehicles, has significant engineering application value, and promotes the coordinated improvement of lightweight and reliability. Brief Description of the Drawings

[0047] The following further describes the present invention in detail with reference to the drawings:

[0048] Figure 1 is a schematic structural diagram of the device of the present invention;

[0049] Figure 2 is a schematic connection structure diagram of the vacuum cavity and the vacuum chamber door of the device of the present invention;

[0050] Figure 3 is a schematic internal structure diagram of the vacuum cavity of the device of the present invention;

[0051] Figure 4 is a schematic diagram of the distribution of the temperature measurement ends of the temperature measurement thermocouples of the device of the present invention;

[0052] Figure 5 is a schematic diagram of the lead distribution of the temperature measurement thermocouples of the device of the present invention.

[0053] Figure 6 is a schematic connection diagram of the control module of the device of the present invention.

[0054] Description of the reference numerals: 1 - water-cooling pump, 2 - vacuum cavity, 3 - vacuum chamber door, 301 - sealing ring, 302 - bolt fastening mechanism, 4 - vacuum valve, 5 - high-pressure argon storage tank, 6 - vacuum pump, 7 - vacuum penetrator, 8 - wiring terminal of the temperature measurement thermocouple, 9 - data acquisition unit, 10 - wiring terminal of the temperature control thermocouple, 11 - control module, 1101 - trigger circuit, 1102 - PID controller, 1103 - operation simulation screen, 12 - power adjustment unit, 13 - temperature control thermocouple, 1401 - first water-cooling electrode, 1402 - second water-cooling electrode, 15 - heat insulation board, 16 - graphite heater, 17 - heat conduction block, 18 - test piece, 19 - workpiece platform, 20 - air pressure sensor. Detailed Description of the Invention

[0055] As Figure 1 shown, a multi-field coupling test device for the thermal properties of a resin matrix composite provided by the present invention includes a vacuum chamber 2, and the vacuum chamber 2 is hermetically and tightly connected to a vacuum chamber furnace door 3. The vacuum chamber 2 and the vacuum chamber furnace door 3 are connected by a bolt fastening mechanism 302, and a sealing ring 301 is arranged at the edge of the vacuum chamber furnace door 3, as Figure 2 shown. By connecting and applying pressure through the bolt fastening mechanism 302, the rubber sealing ring 301 is pressed against the vacuum chamber 2 to achieve the sealing purpose. The vacuum chamber 2 adopts a chamber water-cooling structure, and the inner wall is sprayed with a thermal barrier coating.

[0056] The vacuum chamber 2 is respectively connected to a vacuum pumping device and an inert gas filling device, and is used to make the pressure in the vacuum chamber 2 reach a set air pressure and an inert atmosphere. The vacuum pumping device includes a vacuum pump 6, and the vacuum pump 6 is connected to an air outlet on the vacuum chamber 2 through a vacuum pipeline, and a vacuum valve 4 is arranged on the vacuum pipeline. The vacuum pump 6 cooperates with the vacuum valve 4 to achieve vacuum pumping, and the chamber pressure is reduced to 1×10 -1 Pa to eliminate gas interference. The inert gas filling device includes an argon high-pressure storage tank 5. The air outlet end of the argon high-pressure storage tank 5 is connected to the air inlet end of a mass flow controller, and the air outlet end of the mass flow controller is connected to an air inlet on the vacuum chamber 2 through a filling pipeline. 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 are used to ensure that no oxidation reaction occurs during the pyrolysis process of the material to burn out the specimen, and to avoid oxidation reaction or air interference during the pyrolysis process of the material, and at the same time, the air pressure data in the vacuum chamber 2 is measured by a pressure sensor 20.

[0057] The vacuum chamber 2 is also connected to a water-cooling unit, and the water-cooling unit is used to cool down the vacuum chamber 2. The water-cooling unit includes a water-cooling pump 1 and a water collection row arranged in the vacuum chamber 2. Water-cooling channels are arranged on the inner wall of the vacuum chamber 2, and the water-cooling channels are connected to the water inlet and the water outlet through the water collection row. The water inlet and the water outlet of the water-cooling pump 1 are respectively connected to the water outlet and the water inlet on the vacuum chamber 2.

[0058] As Figure 3As 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.

[0059] 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.

[0060] 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.

[0061] In this embodiment, the temperature control unit includes a temperature control thermocouple 13, a control module 11, and a power regulation unit 12. The power regulation unit 12 uses a thyristor power regulator. The temperature measurement end of the temperature control thermocouple 13 is arranged inside the heat conduction block 17. The wiring end 10 of the temperature control thermocouple 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 regulation unit 12. The output end of the power regulation unit 12 is connected to the graphite heater 16 through the second water-cooled electrode 1402. As Figure 6 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 wiring end 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 regulation unit 12. The operation simulation screen 1103 is used for manually inputting set parameters. The control input end of the PID controller 1102 is connected to the input end of the operation simulation screen 1103. By inputting the set temperature through the operation simulation screen 1103, the set temperature value is sent to the PID controller 1102. The temperature control thermocouple 13 detects the real-time temperature inside 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, generates a control signal through the internal algorithm (proportional-integral-derivative) of the PID controller 1102, and the control signal output by the PID controller 1102 is transmitted to the trigger circuit 1101. The power regulation unit 12 adjusts the conduction angle or duty cycle according to the control signal, thereby regulating the input power of the graphite heater 16 to make the temperature of the heat conduction 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.

[0062] Taking the boron nitride heat conduction block 17 as the heat conduction regulation structure, the upper and lower surfaces are respectively in contact with the graphite heater 16 and the upper surface of the test piece 18. The insulation strength of boron nitride can isolate the high-voltage current of the graphite heater 16 and avoid the risk of electric leakage between the test piece 18 and the heating unit.

[0063] The present invention realizes the coupled regulation of pressure and temperature, simulates the real flight environment, and through the combination of a vacuum pumping device and an inert gas filling device, supports inert gas protection and the switching of low-pressure / high-pressure environments, and avoids the interference of pyrolysis gas oxidation.

[0064] When implementing the present invention, it is operated according to the following steps:

[0065] Step A: Install the heat insulation device on the test piece 18, that is, wrap the aerogel layer around the outer layer of the test piece 18, and install the outer wall plate outside the aerogel layer;

[0066] Step B: Install seven temperature - measuring thermocouples on the test piece 18 through the outer wall plate and the aerogel layer;

[0067] Step C: Fix the test piece 18 on the workpiece platform 19, and adjust the stroke of the workpiece platform 19 so that the test piece 18 is in close contact with the surface of the heat - conducting block 17;

[0068] Step D: Connect the leads of the seven temperature - measuring thermocouples to the vacuum penetrator 7;

[0069] Step E: Start the vacuum pump 6, evacuate the air, and adjust the pressure of the vacuum cavity 2 to 1×10 -1 Pa, then turn off the vacuum pump 6;

[0070] Step F: Open the argon high - pressure storage tank 5, and accurately inject argon into the vacuum cavity 2 through the mass flow controller. After reaching the set pressure, stop the injection;

[0071] Step G: Heat up through the graphite heater 16, and use the control module 11 to control the temperature within ±1℃. When the top temperature of the test piece 18 reaches 800℃ and the bottom temperature rise is 50℃, cut off the heating power supply and stop heating;

[0072] 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 cavity 2 measured by the air pressure sensor 20;

[0073] Step I: After completing the data acquisition, release the gas pressure in the vacuum cavity 2 to atmospheric pressure to end the test.

[0074] Step J: Obtain the temperature measurement data of the temperature - measuring points under a certain ambient air pressure from the above test , and perform data processing based on the multi - field coupling test method for the thermal properties of resin - based composites.

[0075] The present invention realizes pressure - temperature coupling regulation, simulates the real flight environment, and through the combination of the argon pressurization device and the vacuum unit, supports inert gas protection and the switching between low - pressure / high - pressure environments, avoiding the interference of pyrolysis gas oxidation.

[0076] The present invention also provides a multi - field coupling test method for the thermal properties of resin - based composites, including the following steps:

[0077] S1: Obtain the temperature measurement data of multiple temperature - measuring points of the test piece under the set ambient air pressure as a data set, where x and t are the position coordinates and time coordinates respectively, and i, j are the indices of the position coordinates and time coordinates respectively. The multiple temperature - measuring points include the top, bottom, and middle positions of the test piece.

[0078] S2: Perform data processing based on a physics-informed neural network to obtain the thermal conductivity parameter and the specific heat capacity parameter. Specifically, it includes the following steps:

[0079] S2.1: Construct a physics-informed neural network, a governing equation, and a total loss function. The input of the physics-informed neural network includes the position coordinate x and the time coordinate t, and the output of the physics-informed neural network includes the temperature T, the density ρ of the resin matrix composite, and the pyrolysis gas mass flow rate. .

[0080] The governing equation includes the energy equation of the resin matrix composite and the mass conservation equation of the pyrolysis gas. The formula of the energy equation of the resin matrix composite is as follows:

[0081]

[0082] Among them, ρ is the density of the resin matrix composite, c p is the specific heat capacity of the resin matrix composite, T is the temperature, k is the thermal conductivity of the resin matrix composite, Δh is the heat of pyrolysis, is the pyrolysis gas mass flow rate, c g is the specific heat capacity of the pyrolysis gas.

[0083] The thermal conductivity k and the specific heat capacity c of the resin matrix composite p are respectively fitted as polynomials:

[0084]

[0085]

[0086] Among them, a3, a2, a1, and a0 are thermal conductivity parameters, and b1 and b0 are specific heat capacity parameters.

[0087] The formula of the mass conservation equation of the pyrolysis gas is as follows:

[0088]

[0089] Since the thermal conductivity k and the specific heat capacity c of the resin matrix composite p are functions of temperature, according to the chain rule:

[0090]

[0091] Among them, h is the enthalpy value of the solid material, h g is the enthalpy value of the pyrolysis gas.

[0092] The density change rate caused by the pyrolysis reaction is calculated by the Arrhenius equation, and the formula is as follows:

[0093]

[0094] Among them, B is the pre-exponential factor, E is the activation energy of the reaction, R is the universal gas constant, ρ v and ρ c are the densities of the raw material and the fully carbonized material, and n is the reaction order.

[0095] The total loss function includes a data-driven loss term and a physical-information loss term. The data-driven loss term L d is calculated from the mean square error between the predicted temperature and the temperature measurement data at multiple temperature measurement points, and the formula is as follows:

[0096]

[0097] where N d is the total number of temperature measurement points, T(x i ,t j ) is the predicted temperature T at the temperature measurement point at (x i ,t j ), and is the temperature measurement data at multiple temperature measurement points at .

[0098] 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, and are already included in L d .

[0099] The physical-information loss term L p is calculated from the governing equation and the initial conditions. The initial conditions include the initial temperature T0 and the initial density ρ0. The calculation formula for the physical-information loss term L p is as follows:

[0100]

[0101] where N p is the number of regional training points, and N i is the number of initial-condition training points.

[0102] The total loss function L is:

[0103]

[0104] where λ p is the weight corresponding to the physical-information loss term, and λ d is the weight corresponding to the data-driven loss term.

[0105] S2.2: Combine the control equation and the loss function to train the physics-informed neural network. During the training process, the thermal conductivity parameter, specific heat capacity parameter to be identified, and the weights and biases of the physics-informed neural network are jointly used as training parameters to participate in the training until the physics-informed neural network converges, and then extract the thermal conductivity parameter and specific heat capacity parameter identified by the trained physics-informed neural network.

[0106] The physics-informed neural network is trained using the gradient descent method. The specific formula is as follows:

[0107]

[0108] where η is the learning rate, and θ a is the training parameter of the physics-informed neural network in the a-th round of iteration.

[0109] S3: Obtain the thermal conductivity k and specific heat capacity c of the resin matrix composite under the set environmental air pressure according to the thermal conductivity parameter and specific heat capacity parameter p .

[0110] The test method of the present invention can obtain the true temperature measurement data of the internal test points of the material based on experimental tests, and use the physics-informed neural network to invert the thermal physical properties of the resin matrix composite, no longer relying on the thermal conductivities of the carbonized layer and the original material layer, and the thermal physical properties are more real.

[0111] Based on the PINN model, the present invention replaces the traditional inversion calculation and solves the problem of inaccurate boundary parameters relied on. Through the multi-field coupling of temperature-pressure-gas and the intelligent data inversion based on the physics-informed neural network (PINN), the present invention solves the core problems such as the neglect of pyrolysis gas effect and data model distortion in the prior art, provides a high-precision and full-condition test method for the thermal physical properties of the thermal protection materials of hypersonic vehicles, has significant engineering application value, and promotes the coordinated improvement of lightweight and reliability.

[0112] The above are only the 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 those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope defined by the claims.

Claims

1. 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: k=a3T 3 +a2T 2 +a1T+a0; c p =b1T+b0; 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 .

2. The multi-field coupling test method for thermal properties of resin-based composite materials according to claim 1, 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 ) of the predicted temperature T, For multiple temperature measurement points at (x i , t j ) at a temperature measurement point; 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: L=λ p L p +λ d L d ; 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.

3. The multi-field coupling test method for thermal properties of resin-based composite materials according to claim 1, characterized in that: The temperature measurement data of the multiple temperature measurement points in step S1 According to the multi-field coupling test device for thermal properties of resin-based composite materials, the multi-field coupling test device for thermal properties of resin-based composite materials includes a vacuum chamber, which is sealed and fastened to the vacuum chamber furnace door; the vacuum chamber is respectively connected to a vacuum pumping device and an inert gas charging device, which are used to make the vacuum chamber reach a set air pressure and an inert atmosphere, and the vacuum chamber is also connected to a water cooling unit, which is used to cool the vacuum chamber, and a workpiece platform and a heating unit are arranged in the vacuum chamber, and the heating unit includes a heat conductive block arranged above the workpiece platform, and a graphite heater is arranged in contact with the upper surface of the heat conductive block, and the graphite heater is connected to the temperature control unit, and a heat insulating device and a temperature measuring unit are arranged on the workpiece platform, and the heat insulating device is used to cover the test piece, and the temperature measuring unit includes a plurality of temperature measuring couples, and each of the temperature measuring couples The temperature measuring end is used to insert the test piece, and the wiring terminal of each of the temperature measuring couples is connected to the data acquisition unit. 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 embed the test piece. There are multiple intermediate temperature measuring couples distributed along the axial direction of the test piece. The temperature measuring ends of the multiple intermediate temperature measuring couples are 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. An air pressure sensor is arranged on the vacuum cavity, and the sensing part of the air pressure sensor is inserted into the vacuum cavity. The output end of the air pressure sensor is connected to the data acquisition unit.

4. The multi-field coupling test method for thermal properties of resin-based composite materials according to claim 3, 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.

5. The multi-field coupling test method for thermal properties of resin-based composite materials according to claim 3, 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.

6. The multi-field coupling test method for thermal properties of resin-based composite materials according to claim 3, 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.

7. The multi-field coupling test method for thermal properties of resin-based composite materials according to claim 3, 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.

8. The multi-field coupling test method for thermal properties of resin-based composite materials according to claim 7, 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.

9. The multi-field coupling test method for thermal properties of resin-based composite materials according to claim 3, 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.

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