Carbon fiber coating resin mixing management system and control method

Abstract

This invention belongs to the field of carbon fiber composite material preparation technology and discloses a resin mixing management system for carbon fiber coating. It includes a mixing vessel, a stirrer, a variable frequency drive motor, a temperature sensor, a power sensor, a cooling jacket, a flow regulating valve, and a controller. The controller calculates the cumulative heat of reaction based on the real-time drive power signal, the resin temperature signal, the inlet and outlet temperatures of the cooling medium, and the mass flow rate of the cooling medium; it predicts the dynamic viscosity based on the cumulative heat of reaction, the resin temperature signal, and the shear rate of the stirrer; and it calculates the target rotation speed command and the cooling flow rate adjustment command based on the deviation between the dynamic viscosity and the target viscosity and the time change rate of the cumulative heat of reaction. This invention solves the technical problem of drastic viscosity fluctuations caused by exothermic reactions during thermosetting resin mixing, making it difficult to maintain the optimal coating window, and achieves coordinated control of reaction heat and viscosity.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber composite material preparation technology, and specifically to a thermosetting resin mixing management system and its control method for carbon fiber coating process. Background Technology

[0002] In carbon fiber coating processes, the mixing uniformity and viscosity stability of thermosetting resins directly affect the interlaminar shear strength and surface quality of the coated composite material. Existing resin mixing systems typically employ a constant-speed stirring combined with a constant-temperature jacket control mode, meaning a fixed stirring speed and cooling water temperature are set, relying on operator experience to determine the mixing endpoint. During mixing, the resin matrix and curing agent immediately undergo a cross-linking reaction upon contact. This exothermic reaction raises the resin temperature, which further accelerates the reaction rate. Simultaneously, the resin viscosity exhibits non-linear and drastic fluctuations with the degree of reaction and temperature. This strong coupling effect of reaction heat, temperature, and viscosity leads to significant viscosity differences in different regions of the mixing vessel, making it difficult to maintain viscosity within the optimal window required for the coating process throughout the entire mixing cycle. Current technologies lack real-time sensing capabilities for accumulated reaction heat and cannot dynamically adjust stirring speed and cooling intensity based on the reaction progress. This results in uneven resin penetration during coating, forming dry spots or resin-rich areas, severely reducing the product yield of carbon fiber composites.

[0003] There is an urgent need for a resin mixing management system and control method for carbon fiber coating that can sense the accumulated heat of reaction in real time and dynamically adjust the stirring speed and cooling intensity according to the reaction process, so as to solve the technical problem of viscosity runaway and inability to maintain the optimal coating window caused by the strong coupling effect of heat of reaction, temperature and viscosity. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a resin mixing and management system for carbon fiber coating, comprising: a mixing vessel; a stirrer disposed inside the mixing vessel; a variable frequency drive motor connected to the stirrer; a temperature sensor installed on the inner wall of the mixing vessel for collecting the temperature signal of the resin inside the mixing vessel; a power sensor connected to the variable frequency drive motor for collecting the real-time drive power signal of the stirrer; a cooling jacket covering the outer wall of the mixing vessel; and a flow regulating valve installed on the cooling medium inlet pipe of the cooling jacket; and a control system. The device and controller are electrically connected to a temperature sensor, a power sensor, a variable frequency drive motor, and a flow regulating valve, respectively. The controller is configured to: calculate the cumulative heat of reaction based on the real-time drive power signal, the resin temperature signal, the inlet and outlet temperatures of the cooling medium in the cooling jacket, and the mass flow rate of the cooling medium; predict the dynamic viscosity based on the cumulative heat of reaction, the resin temperature signal, and the shear rate of the agitator; calculate the target speed command and the cooling flow rate regulation command based on the deviation between the dynamic viscosity and the target viscosity and the time change rate of the cumulative heat of reaction; output the target speed command to the variable frequency drive motor and the cooling flow rate regulation command to the flow regulating valve.

[0005] Preferably, the temperature sensor is a thermocouple array, which includes at least three thermocouples distributed along the axial direction of the mixing vessel.

[0006] More preferably, the power sensor is a torque sensor, which is installed between the output shaft of the variable frequency drive motor and the input shaft of the agitator.

[0007] More preferably, the cooling jacket is a spiral coil type jacket, and a first temperature sensor and a second temperature sensor are respectively installed at the cooling medium inlet and cooling medium outlet of the cooling jacket. Both the first temperature sensor and the second temperature sensor are electrically connected to the controller.

[0008] More preferably, the controller calculates the target speed command. Use the following formula: ; in The dimension is revolutions per minute. The reference speed is measured in revolutions per minute. The target viscosity is expressed in Pascal-seconds. The viscosity is dynamic and its dimension is Pascal-second. It is the stirring power exponent and is dimensionless. The heat release rate suppression coefficient is expressed in seconds per joule. The time-varying rate of change of the cumulative heat of reaction, in watts. The integral coefficient for cooling is given by revolutions per fenelvin. The time-varying rate of change of the resin's temperature signal is expressed in Kelvin per second. It is the adiabatic temperature rise rate, with dimensions in Kelvin per second.

[0009] In a further preferred embodiment, the controller calculates the cumulative heat of reaction using the energy balance principle: the time integral of the real-time drive power signal minus the energy consumed by the resin heating and the heat carried away by the cooling medium equals the cumulative heat released by the reaction.

[0010] More preferably, the controller uses a product of a temperature-dependent exponential model, a linear correction term for the accumulated heat of reaction, and a shear rate-dependent power-law model when predicting dynamic viscosity.

[0011] A control method for a resin mixing management system for carbon fiber coating, applied to any one of the above-described resin mixing management systems for carbon fiber coating, includes the following steps: Step S1: The controller collects the real-time drive power signal output by the power sensor, the resin temperature signal output by the temperature sensor, the inlet temperature of the cooling medium in the cooling jacket, the outlet temperature of the cooling medium, and the mass flow rate of the cooling medium in real time. Step S2: The controller calculates the cumulative heat of reaction based on the data collected in step S1. Step S3: The controller calculates the predicted dynamic viscosity value based on the accumulated heat of reaction, the resin temperature signal, and the shear rate of the stirrer. In step S4, the controller calculates the target rotational speed and cooling medium flow rate adjustment value based on the deviation between the predicted dynamic viscosity and the target viscosity and the time change rate of the accumulated reaction heat. It adjusts the output frequency of the variable frequency drive motor according to the target rotational speed value and controls the opening of the flow regulating valve according to the cooling medium flow rate adjustment value.

[0012] In a further preferred embodiment, the energy balance equation is used to calculate the cumulative heat of reaction in step S2: the time integral of the real-time drive power signal is equal to the sum of the sensible heat of the resin, the heat carried away by the cooling medium, and the cumulative heat of reaction. The sensible heat of the resin is obtained by the integral of the product of the resin mass, the resin specific heat capacity, and the time change rate of the resin temperature signal. The heat carried away by the cooling medium is obtained by the integral of the product of the mass flow rate of the cooling medium, the specific heat capacity of the cooling medium, and the difference between the outlet temperature and the inlet temperature of the cooling medium.

[0013] Further preferably, the mixture also includes an ultrasonic transducer array and a low-frequency pressure pulsating pump. The ultrasonic transducer array is installed on the outer wall of the mixing vessel and electrically connected to the controller. The outlet of the low-frequency pressure pulsating pump is connected to the interior of the mixing vessel and electrically connected to the controller. The controller is also configured to: calculate and estimate the average bubble radius based on the dynamic viscosity and the current rotation speed of the stirrer. When the estimated average bubble radius is greater than the radius threshold, the controller activates the ultrasonic transducer array to emit a standing wave signal with a frequency equal to the bubble resonance frequency, and simultaneously activates the low-frequency pressure pulsating pump to apply pressure pulsation to the mixing vessel.

[0014] Technical effects: This invention calculates the cumulative heat of reaction and predicts the dynamic viscosity in real time through a controller, and then dynamically adjusts the stirring speed and cooling flow rate according to the viscosity deviation and heat release rate. This solves the problem that the existing technology cannot cope with the drastic viscosity changes caused by the heat of reaction, and achieves stable viscosity control throughout the mixing cycle. It avoids coating defects caused by local overheating and gelation or insufficient viscosity, while reducing energy consumption. Attached Figure Description

[0015] Figure 1 Hardware connection diagram of the resin mixing and management system for carbon fiber coating; Figure 2 Timing diagram of single-cycle real-time control for resin mixing management system for carbon fiber coating; Figure 3 Logic block diagram for calculating the cumulative reaction heat of the resin mixing management system for carbon fiber coating; Figure 4 Logic block diagram for dynamic viscosity prediction in a resin mixing management system for carbon fiber coating; Figure 5 Flowchart of the control method steps for the resin mixing management system for carbon fiber coating. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] The existing technology has the following technical problems: during the mixing process of thermosetting resin in carbon fiber coating, the heat generated by the crosslinking reaction causes the resin temperature to rise continuously. The rise in temperature further accelerates the crosslinking reaction, and the accelerated reaction releases more heat, forming a positive feedback loop of exothermic reaction and accelerated reaction. At the same time, the viscosity of the resin fluctuates drastically with the deepening of the reaction and temperature changes. Traditional constant speed stirring and constant temperature cooling control methods cannot be dynamically adjusted according to the real-time state of the resin, making it difficult to maintain the resin viscosity within the optimal window required for the carbon fiber coating process. Ultimately, this leads to defects such as sagging, pinholes, and uneven thickness in the coated carbon fiber composite material, which cannot meet the process requirements of high-precision coating.

[0018] Based on this, please refer to Figures 1-5 This embodiment provides a resin mixing and management system for carbon fiber coating, including a mixing vessel, a stirrer, a variable frequency drive motor, a temperature sensor, a power sensor, a cooling jacket, a flow regulating valve, and a controller. It also includes an ultrasonic transducer array and a low-frequency pressure pulsating pump. The stirrer is disposed inside the mixing vessel, and the variable frequency drive motor is connected to the stirrer. The temperature sensor is installed on the inner wall of the mixing vessel to collect the temperature signal of the resin inside the mixing vessel. The power sensor is connected to the variable frequency drive motor to collect the real-time drive power signal of the stirrer. The cooling jacket covers the outer wall of the mixing vessel, and the flow regulating valve is installed on the cooling medium inlet pipe of the cooling jacket. The controller is electrically connected to the temperature sensor, the power sensor, the variable frequency drive motor, and the flow regulating valve. The ultrasonic transducer array is installed on the outer wall of the mixing vessel and electrically connected to the controller. The outlet of the low-frequency pressure pulsating pump is connected to the interior of the mixing vessel and electrically connected to the controller. The controller is configured to calculate the cumulative heat of reaction based on the real-time drive power signal, the resin temperature signal, the inlet and outlet temperatures of the cooling medium in the cooling jacket, and the mass flow rate of the cooling medium; predict the dynamic viscosity based on the cumulative heat of reaction, the resin temperature signal, and the shear rate of the stirrer; calculate the target speed command and the cooling flow rate adjustment command based on the deviation between the dynamic viscosity and the target viscosity and the time change rate of the cumulative heat of reaction; output the target speed command to the variable frequency drive motor; output the cooling flow rate adjustment command to the flow regulating valve; and simultaneously calculate the estimated average bubble radius based on the dynamic viscosity and the current speed of the stirrer. When the estimated average bubble radius is greater than the radius threshold, the ultrasonic transducer array is activated to emit a standing wave signal with a frequency equal to the bubble resonance frequency, and the low-frequency pressure pulsating pump is activated to apply pressure pulsation to the mixing vessel.

[0019] The mixing vessel is a sealed stainless steel structure with a mirror-polished inner wall to a polishing precision of Ra0.2μm, reducing resin adhesion and eliminating mixing dead zones. Its effective volume can be flexibly set according to the production scale of carbon fiber coating, typically ranging from 50L to 500L. The top of the vessel has resin and curing agent inlets, and the bottom has an outlet. Both inlets and outlets are equipped with sealing valves to ensure the airtightness of the mixing process and prevent resin oxidation and deterioration due to contact with air. The agitator is located in the center of the mixing vessel and employs a slanted-blade turbine agitator structure with 4 to 6 blades. The angle between the blades and the agitator shaft is 45 degrees, and the blade diameter is 1 / 3 to 1 / 2 of the inner diameter of the mixing vessel. The agitator shaft is made of 304 stainless steel and is rigidly connected to the output shaft of the variable frequency drive motor via a coupling. This agitator structure can simultaneously improve the mixing shear effect and axial convection capacity of the resin, ensuring the uniformity of resin mixing within the vessel. The variable frequency drive motor is a three-phase asynchronous variable frequency speed control motor, adapted to 380V industrial AC power, with a speed range of 0 to 1500 rpm and an output power of 2.2kW to 15kW. It can be flexibly selected according to the volume of the mixing tank and the viscosity characteristics of the resin. The motor is equipped with a high-precision encoder with an encoding accuracy of 1024 lines / revolution, which can provide real-time feedback on the actual speed of the motor and provide accurate data for subsequent power calculation and speed adjustment.

[0020] The temperature sensor employs a thermocouple array structure, comprising at least three thermocouples distributed along the axial direction of the mixing vessel. The thermocouples are type K, with a temperature measurement range of 0℃ to 300℃, a measurement accuracy of ±0.5℃, and a thermal response time of less than 0.5s. The thermocouples are arranged at equal intervals from top to bottom along the axial direction of the mixing vessel, with a spacing of 1 / 4 to 1 / 3 of the mixing vessel's height. They are positioned near the resin surface, in the middle of the mixing vessel, and at the bottom of the mixing vessel. The probe of each thermocouple is in close contact with the inner wall of the mixing vessel, ensuring full contact with the resin. Each thermocouple independently outputs the resin temperature signal at its location. All signals are transmitted to the controller via a shielded cable, with the shielding layer of the cable grounded to prevent electromagnetic interference from affecting the temperature signal. The power sensor is a torque sensor, which is installed at the coupling position between the output shaft of the variable frequency drive motor and the input shaft of the agitator. A static torque sensor is selected, with a measurement range of 0 to 500 N·m, a measurement accuracy of ±0.1%FS, and a nonlinear error of less than 0.05%FS. It can detect the torsional stress transmitted on the rotating shaft in real time. At the same time, the torque sensor can synchronously collect the speed signal of the variable frequency drive motor. The actual mechanical power of the agitator is directly calculated by multiplying the torque and angular velocity. Compared with the method of indirectly estimating the power through the motor current, this method is not affected by the motor iron loss, copper loss, air gap change and harmonic interference, and can truly reflect the resistance encountered by the agitator blades rotating in the resin.

[0021] The cooling jacket is a spiral coil type, made of 316L stainless steel, which has good corrosion resistance and thermal conductivity. The coil diameter is 20mm to 32mm, and the coil pitch is 50mm to 100mm. The coil tightly covers the outer wall of the mixing vessel, and the contact area with the outer wall of the vessel accounts for more than 80% of the total area of ​​the outer wall of the vessel, which greatly increases the heat exchange area and extends the residence time of the cooling medium in the jacket, thereby improving the heat exchange efficiency. The flow regulating valve installed on the cooling medium inlet pipe of the cooling jacket is an electric proportional regulating valve with an adjustment range of 0 to 100m. 3 The cooling medium flow rate is adjustable at ±1% per hour, with a response time of less than 1 second. It supports 4-20mA analog signal control and can precisely adjust the cooling medium flow rate according to the instructions issued by the controller. The cooling medium inlet and outlet of the cooling jacket are respectively equipped with a first temperature sensor and a second temperature sensor. Both the first and second temperature sensors are PT100 platinum resistance temperature sensors with a temperature measurement range of 0℃ to 100℃, a temperature measurement accuracy of ±0.2℃, and a resolution of 0.1℃. They are electrically connected to the controller to collect the initial temperature of the cooling medium before it enters the jacket and the temperature after it flows out of the jacket in real time, providing accurate temperature difference data for calculating the cumulative heat of reaction.

[0022] The ultrasonic transducer array consists of at least six piezoelectric ultrasonic transducers, which are evenly distributed in a ring on the lower outer wall of the mixing vessel. The transducers have an operating frequency range of 20kHz to 100kHz and a transmission power of 50W to 200W. They are connected to the controller via an RS485 bus and can adjust the transmission frequency and power according to the controller's instructions. The low-frequency pressure pulsation pump is a plunger-type pressure pump with a stainless steel body. The pressure range is 0.1MPa to 0.5MPa, and the operating frequency is 0.5Hz to 2Hz. The outlet of the low-frequency pressure pulsation pump is connected to the interior of the mixing vessel through a stainless steel pipe extending to half the height of the resin liquid in the mixing vessel. A dispersion nozzle is installed at the outlet of the pipe to ensure that the pressure pulsation acts evenly on the interior of the resin. The low-frequency pressure pulsation pump is electrically connected to the controller and receives start / stop and frequency adjustment commands from the controller.

[0023] The controller is an industrial-grade programmable logic controller (PLC), using the Siemens S7-1500 series, equipped with a 1.2GHz quad-core processor, 16GB of high-speed storage capacity and 8GB of cache. It supports multi-channel analog and digital signal acquisition, with an analog acquisition accuracy of 16 bits and a digital acquisition frequency of 1kHz. The controller connects to the temperature sensor, power sensor, first temperature sensor, and second temperature sensor via shielded cables to achieve analog signal connection, and to the variable frequency drive motor, flow regulating valve, ultrasonic transducer array, and low-frequency pressure pulsating pump via an industrial bus to achieve digital signal connection, ensuring real-time and stable signal transmission. The controller has built-in dedicated algorithm modules, including a signal filtering module, a reaction heat calculation module, a viscosity prediction module, a control command generation module, and a bubble displacement control module. These modules work together to complete the entire process control from signal acquisition and data calculation to command issuance. The controller is also equipped with a touch screen operating interface, supporting manual setting of process parameters, display of real-time data, and storage of historical data with a storage period of up to one year, facilitating production process traceability and optimization.

[0024] The controller's signal filtering module preprocesses all acquired sensor signals, using median filtering to remove noise interference. The filtering window is set to five sampling points. By eliminating extreme values ​​and using the median as valid data, it effectively suppresses signal fluctuations caused by electromagnetic interference and mechanical vibration without signal lag, ensuring the accuracy of data used in subsequent calculations. After signal filtering, the controller's reaction heat calculation module calculates the cumulative reaction heat based on the energy balance principle. This calculation is theoretically based on the first law of thermodynamics, which states that the change in internal energy of a closed system equals the heat exchange between the system and its surroundings plus the work done by the surroundings on the system. For this resin mixing system, the mixing process is a closed process, and the volume and mass of the resin are essentially constant. Ignoring secondary energy losses such as friction of the stirring shaft and heat dissipation from the vessel wall, all mechanical work done by the surroundings on the system is converted into changes in the internal energy of the resin, heat carried away by the cooling medium, and chemical energy released by the resin cross-linking reaction. Based on this principle, the calculation equation for the cumulative reaction heat is derived as follows: By transforming the above equation, the specific formula for calculating the cumulative heat of reaction is as follows: In this formula, For real-time driving power signals, the dimensions are... (Watt), calculated from the torque value detected by the torque sensor and the angular velocity, where the angular velocity is converted from the rotational speed of the variable frequency drive motor, and the conversion relationship is as follows: ,in The real-time speed of the motor, with dimensions of (Reposted per minute) Let be the angular velocity, with dimensions . (Radians per second, where radians are dimensionless), ultimately passing through The real-time drive power is calculated. The torque value detected by the torque sensor, with dimensions of (Cow rice); The total mass of the resin, with dimensions of (kg), this parameter is set by the user in the controller according to the effective volume of the mixing vessel and the resin filling factor. The resin filling factor is typically 0.7 to 0.8 to avoid resin splashing during stirring. Resin volatilization and wall-mounting loss are ignored during mixing. It is a constant value; The isobaric specific heat capacity of the resin, with dimensions of (Joules per kilogram Kelvin), resin for coating thermosetting carbon fibers The value ranges from 1200 J / (kg·K) to 1800 J / (kg·K), and users can calibrate the controller according to the type of resin actually used. The time-varying rate of change of the resin's temperature signal, with dimensions of (Kelvin per second), the temperature signal collected by the thermocouple array is calculated by the five-point difference method. The five-point difference method selects five consecutive sampling points for difference operation, which effectively improves the calculation accuracy of temperature change rate and avoids the error caused by single-point temperature fluctuation. The weighted average temperature of the thermocouple array is used in the calculation. The thermocouple weight near the bottom of the mixing vessel is set to 0.4, the weight in the middle is set to 0.3, and the weight near the liquid surface is set to 0.3, which takes into account the characteristics of the heat of reaction accumulating at the bottom and the heat dissipation characteristics of the liquid surface. The mass flow rate of the cooling medium, with dimensions of (kg / s), calculated from the opening degree of the flow regulating valve and the flow characteristic curve of the cooling medium pipeline. The cooling medium is typically deionized water with a density of 1000 kg / m³. 3 The flow characteristic curve is pre-entered into the algorithm module of the controller; The isobaric specific heat capacity of the cooling medium, with dimensions of (Joules per kilogram Kelvin), deionized water at room temperature The value is 4186 J / (kg·K), which is a constant. The outlet temperature of the cooling medium, with dimensions of (Kelvin), collected in real time by the second temperature sensor; The inlet temperature of the cooling medium, with dimensions of (Kelvin), collected in real time by the first temperature sensor; The cumulative heat of reaction, with dimensions of (Joules), reflecting the time from the start of mixing to the moment... The total heat released by the resin due to the cross-linking reaction.

[0025] The core innovation of this formula lies in combining the first law of thermodynamics with the actual resin mixing process, eliminating secondary energy loss factors. It utilizes only parameters collected by the system's existing sensors to achieve soft measurement of the cumulative heat of reaction, eliminating the need for expensive online chromatographs and spectrometers, thus significantly reducing system hardware costs. Simultaneously, the formula reflects the cumulative energy effect through integration, enabling real-time tracking of the heat of reaction's changing trend and providing accurate reaction progress data for subsequent viscosity prediction and control command generation. The formula is implemented by the controller's heat of reaction calculation module, which uses a 1ms calculation step and employs the trapezoidal integration method to numerically integrate each term. This method divides the integration interval into several small trapezoids, calculating the sum of the areas of all small trapezoids as the integration result. Compared to the rectangular integration method, this method has a smaller integration error and effectively avoids the accumulation of integration errors, ensuring the accuracy of the cumulative heat of reaction calculation. During the calculation process, the controller continuously calls upon filtered data from each sensor, substitutes it into the formula for continuous calculation, and transmits the calculation results to the controller's viscosity prediction module in real time.

[0026] After the cumulative heat of reaction is calculated, the viscosity prediction module of the controller predicts the dynamic viscosity of the resin based on the cumulative heat of reaction, the temperature signal of the resin, and the shear rate of the stirrer. The theoretical basis for this prediction is the Arrhenius equation, the viscosity change law of the curing reaction, and a power-law rheological model. The Arrhenius equation describes the quantitative relationship between molecular motion rate and temperature; the viscosity of the resin is negatively correlated with the molecular motion rate. As the temperature increases, the molecular motion rate accelerates, and the viscosity decreases exponentially. The cross-linking reaction of thermosetting resins increases the cross-linking density of molecular chains with the deepening of the reaction. The degree of reaction can be characterized by the cumulative heat of reaction per unit volume, and the viscosity increases linearly with the increase of the cross-linking density. During stirring, the resin is in a shear flow state, and its shear viscosity follows a power-law model. Pseudoplastic thermosetting resins exhibit shear-thinning characteristics, meaning that the higher the shear rate, the lower the viscosity. Based on the above three fundamental theories, the thermal effect of temperature on viscosity, the chemical effect of heat of reaction on viscosity, and the flow effect of shear rate on viscosity are decoupled and combined in a product form to derive the prediction model for dynamic viscosity: ; In this formula, The dynamic viscosity has the following dimensions: (Pascal second) is a time interval. The instantaneous viscosity of the resin is the target value for viscosity prediction; For reference viscosity, the dimensions are: (Pascal second) is the time it takes for the resin to reach a reference temperature. No cross-linking reaction, reference shear rate The base viscosity is determined experimentally based on the type of thermosetting resin used for carbon fiber coating, with a typical range of 10 Pa·s to 100 Pa·s. Users can adjust the value in the controller according to the actual resin used. The characteristic constant related to the activation energy of resin molecular motion has dimensions of (Kelvin), derived from the Arrhenius equation, has a value of ,in The activation energy for the motion of resin molecules, with dimensions of (joules per mole) The gas constant is 8.314 J / (mol·K). The value ranges from 2000K to 8000K, and is obtained by measuring the viscosity of the resin at different temperatures and using data fitting. For a moment The resin weighted average temperature, with dimensions of (Kelvin), consistent with the temperature used in the calculation of cumulative reaction heat, is obtained by weighted averaging of the acquired signals from the thermocouple array; The thermal influence coefficient of the reaction has dimensions of . (per cubic meter per joule), a dimensionless correlation parameter reflecting the influence of the cumulative heat of reaction per unit volume on the resin viscosity, with a value range of 0.001 m. 3 / J to 0.01m 3 / J, by testing the viscosity of the resin under different cumulative heat of reaction, the larger the coefficient, the more significant the effect of heat of reaction on viscosity; Let V be the volume of the resin, with dimensions . (cubic meters), determined by the effective volume of the mixing vessel and the resin filling coefficient, and the total mass of the resin. Correspondingly, it is a constant value; For a moment The cumulative heat of reaction, with dimensions of (Joules), which are transmitted in real time by the reaction heat calculation module of the controller; For a moment The shear rate exerted by the stirrer on the resin, with dimensions of... (The reciprocal of the second), calculated from the stirrer's rotation speed and geometric parameters, is given by the following relationship: ,in This is the shear rate coefficient, dimensionless (reciprocal of a second per revolution per minute), and is related to the blade type, blade diameter, and mixing vessel inner diameter. (This refers to the shear rate coefficient of the inclined blade turbine propeller.) The value range is 10s -1 / (r / min) to 30s -1 / (r / min), The real-time rotational speed of the stirrer, with dimensions of (Reposted per minute); The reference shear rate has the following dimensions: (Reciprocal of a second), usually taken as 100s -1 , where is the typical shear rate of the resin in the carbon fiber coating process, and is a constant value; The rheological index, dimensionless (1), reflects the shear-thinning properties of the resin. It is used for coating thermosetting carbon fibers. The value ranges from 0.3 to 0.8. The smaller the value, the more significant the shear thinning property of the resin. This parameter is obtained by testing the shear viscosity of the resin with a rheometer and using data fitting.

[0027] The core innovation of this formula lies in decoupling and organically combining the three key factors affecting resin viscosity. Each product term corresponds to a single influencing factor, with clear and explicit physical meaning. This facilitates parameter calibration by users based on different resin types and coating process requirements, solving the problem of difficult parameter calibration and complex calculations caused by the coupling of multiple factors in traditional viscosity prediction models. Simultaneously, this model balances physical rationality and computational simplicity, based on classical thermodynamics and rheology theories while simplifying complex molecular dynamics calculations, enabling real-time calculations on industrial controllers. The formula is implemented by the viscosity prediction module of the controller. The module uses a 1ms calculation step, receiving in real-time the accumulated heat of reaction from the heat of reaction calculation module, the resin temperature signal from the signal filtering module, and the real-time rotational speed from the variable frequency drive motor. It then calculates the shear rate and each influencing factor sequentially, multiplying them to obtain the dynamic viscosity prediction value. The calculation result is transmitted in real-time to the controller's control command generation module and simultaneously displayed on the controller's operating interface, facilitating operator monitoring of the resin's viscosity status.

[0028] After dynamic viscosity prediction is completed, the controller's control command generation module calculates the target speed command based on the deviation between the dynamic viscosity and the target viscosity, as well as the time-varying rate of change of the accumulated heat of reaction. The theoretical basis for this calculation is the principles of feedback control, feedforward control, and integral compensation. Simple viscosity feedback adjustment can lead to response lag, especially when the rate of heat release suddenly increases. The resin viscosity may not have increased significantly yet, but it is about to rise sharply due to the sudden temperature increase and accelerated reaction. Therefore, feedforward control is needed to adjust the speed in advance based on the heat release rate. Simultaneously, to compensate for the cooling system's heat dissipation capacity deviation, an integral compensation term is added to achieve coordinated control of feedforward and feedback. Based on the above principles, the calculation formula for the target speed command is derived as follows: ; In this formula, For a moment The target speed command, with dimensions of (Revolutions per minute) is the speed control command output by the controller to the variable frequency drive motor; The reference speed is given by the dimensionless speed. (Revolutions per minute), calibrated according to the resin mixing requirements of the carbon fiber coating process, with a value range of 100 revolutions per minute to 500 revolutions per minute, which is the basic stirring speed for the mixing process to ensure the basic mixing effect of the resin. The target viscosity is , with dimensions of (Pascal-second), set according to the requirements of the carbon fiber coating process, with a value range of 20 Pa·s to 50 Pa·s, is the optimal viscosity window value for the resin to meet the coating process requirements, and is set by the user in the controller. For a moment The dynamic viscosity, with dimensions of (Pascal seconds), transmitted in real time by the viscosity prediction module of the controller; The stirring power index, dimensionless (1), reflects the quantitative relationship between stirring power and rotational speed and viscosity. The formula for calculating stirring power is: ,in The power coefficient has the following dimensions: It is related to the geometric parameters of the agitator and mixing vessel. The value range is 2 to 3. Through experimental calibration, the introduction of this parameter enables the speed adjustment to adapt to the rheological properties of the resin and ensure the stability of the stirring power. The heat release rate suppression coefficient has dimensions of . (seconds per joule), a dimensionless correlation parameter reflecting the degree to which the reaction exothermic rate inhibits the stirring speed, with a value range of 1×10⁻⁶. -6 s / J to 1×10 -4 The larger the coefficient (s / J), the more significant the effect of the heat release rate on the inhibition of rotational speed. The rate of change of the cumulative heat of reaction over time, with dimensions of (Watt), which is the rate of exothermic reaction of the resin, is calculated from the cumulative heat of reaction using the three-point difference method. The three-point difference method can effectively improve the calculation accuracy of the exothermic rate and avoid errors caused by fluctuations in single-point data. Taking the absolute value means that only the magnitude of the exothermic rate is considered, and the direction is not considered. The integral coefficient for cooling has dimensions of . (per fenelvin), a dimensionless correlation parameter that reflects the degree of compensation of the cooling system's heat dissipation capacity deviation to the stirring speed. The value ranges from 0.5 r / (min·K) to 5 r / (min·K). Through experimental calibration, the larger the coefficient, the more significant the compensation of the heat dissipation capacity deviation to the stirring speed. The time-varying rate of change of the resin's temperature signal, with dimensions of (Kelvin per second), consistent with the rate of temperature change used in the calculation of cumulative heat of reaction; The adiabatic temperature rise rate, with dimensions of (Kelvin per second) is the rate of temperature rise of the resin due to exothermic reaction alone, without cooling. The formula is: It is calculated from the reaction exothermic rate and the heat capacity of the resin; integral term The dimensions are (Kelvin), reflecting the time from the start of mixing to the moment The cumulative deviation of the cooling system's heat dissipation capacity. A positive difference indicates insufficient heat dissipation of the cooling system, while a negative difference indicates excessive heat dissipation of the cooling system.

[0029] The core innovation of this formula lies in the organic combination of viscosity feedback speed regulation, exothermic rate feedforward suppression, and cooling integral compensation. This solves the response lag problem of traditional simple viscosity feedback regulation, and achieves advanced control and precise adjustment of resin viscosity. Among them, the viscosity feedback speed regulation term can adjust the rotation speed in real time according to the current viscosity deviation to ensure that the resin viscosity is maintained near the target value. The exothermic rate feedforward suppression term can reduce the rotation speed in advance according to the trend of exothermic reaction, avoiding high rotation speed from aggravating shear heat generation and reaction acceleration, thus suppressing the sharp rise in viscosity from the source. The cooling integral compensation term can compensate for the heat dissipation capacity deviation of the cooling system, and improve the overall temperature control effect of the system by adjusting the rotation speed to assist cooling. The formula is implemented by the control command generation module of the controller. The module receives the dynamic viscosity from the viscosity prediction module, the cumulative heat of reaction from the heat of reaction calculation module, and the temperature change rate from the signal filtering module in real time with a calculation step of 1ms. It then calculates the heat release rate, the adiabatic temperature rise rate, and the values ​​of each component in sequence, and finally adds them together to obtain the target speed command. After the calculation is completed, the controller sends the target speed command to the variable frequency drive motor through the industrial bus. The variable frequency drive motor adjusts the output frequency according to the command to realize the real-time and precise adjustment of the stirrer speed. During the adjustment process, the actual speed of the motor is fed back to the controller through the encoder to form a closed-loop control of the speed.

[0030] The controller's control command generation module, while calculating the target rotational speed command, generates a cooling flow rate adjustment command based on the deviation between the dynamic viscosity and the target viscosity, as well as the time-varying rate of change of the accumulated heat of reaction. The core logic of the cooling flow rate adjustment is coordinated with the calculation of the target rotational speed command. When the absolute value of the reaction exothermic rate exceeds a preset threshold, or the weighted average temperature of the resin exceeds a preset temperature threshold, the controller increases the output value of the cooling flow rate adjustment command, increases the opening of the flow regulating valve, increases the flow rate of the cooling medium, enhances the heat exchange effect of the cooling jacket, and reduces the resin temperature. When the dynamic viscosity is lower than the target viscosity and the reaction exothermic rate is at a low level, the controller appropriately decreases the output value of the cooling flow rate adjustment command, decreases the opening of the flow regulating valve, reduces the flow rate of the cooling medium, and avoids excessively low resin temperature leading to increased viscosity. When both the resin viscosity and temperature are within the target range, the controller maintains a stable cooling flow rate. The output value of the cooling flow rate adjustment command is the opening percentage of the flow rate regulating valve. The opening percentage is linearly related to the flow rate of the cooling medium, and the value range of the opening percentage is 0 to 100%. The controller sends the cooling flow rate adjustment command to the flow rate regulating valve through a 4-20mA analog signal. The flow rate regulating valve adjusts its opening according to the command to achieve real-time and precise adjustment of the cooling medium flow rate. During the adjustment process, the mass flow rate of the cooling medium is calculated through the flow characteristic curve and fed back to the controller to form a closed-loop control of the cooling flow rate.

[0031] The controller's bubble displacement control module and control command generation module work together to calculate the estimated average bubble radius in real time based on the dynamic viscosity and the current speed of the stirrer. The calculation of the estimated average bubble radius is based on the breakup and coalescence patterns of bubbles during stirring. Higher stirring speeds result in greater shear force in the resin, making it easier for bubbles to break into smaller sizes. Higher resin viscosity increases the resistance to coalescence and buoyancy, making it harder for small bubbles to coalesce and grow. Based on this pattern, a calculation relationship for the estimated average bubble radius is established: the average bubble radius is directly proportional to the stirring speed and inversely proportional to the dynamic viscosity of the resin. When the estimated average bubble radius exceeds a radius threshold (typically 50 micrometers, set according to the carbon fiber coating process requirements), many bubbles that are difficult to float naturally exist in the resin. If not promptly displaced, these bubbles will form pinhole defects after coating. The controller immediately activates the ultrasonic transducer array and simultaneously starts the low-frequency pressure pulsation pump. The ultrasonic transducer array calculates the bubble resonance frequency based on the estimated average bubble radius. The bubble resonance frequency is determined by the bubble radius, the surface tension of the resin, and its density. The calculation formula is as follows: ,in The surface tension of the resin has dimensions of . (Newtons per meter), thermosetting resin The value ranges from 0.03 N / m to 0.07 N / m. The density of the resin is given by the dimensionless (π / 2). (kg per cubic meter), thermosetting resin The value range is 1000 kg / m 3 Up to 1200kg / m 3 , To estimate the average radius of the bubble, the dimension is... (meters), the square root parameter in this formula has dimensions of... The dimensions after taking the square root are: ,and of The dimensions after multiplication are The ultrasonic transducer array perfectly matches the frequency dimension (Hertz, the reciprocal of the second). It emits a standing wave signal with a frequency equal to the bubble's resonant frequency. Under resonance conditions, the small bubbles in the resin oscillate violently, colliding and merging to grow larger. Simultaneously, the low-frequency pressure pulsating pump applies pressure pulsations to the resin in the mixing vessel at a frequency of 0.5Hz to 2Hz. The periodic pressure changes further promote bubble aggregation and buoyancy. The aggregated and grown bubbles rapidly rise to the resin surface under the buoyancy of the resin and are discharged through the gas phase space of the mixing vessel, achieving active bubble removal from the resin. When the estimated average bubble radius is less than a radius threshold, the controller shuts off the ultrasonic transducer array and the low-frequency pressure pulsating pump, stopping the bubble removal operation and avoiding unnecessary energy consumption.

[0032] The overall control flow of this system is a continuous closed-loop control. The controller acquires the real-time drive power signal output by the power sensor, the resin temperature signal output by the temperature sensor, the cooling medium inlet temperature output by the first temperature sensor, and the cooling medium outlet temperature output by the second temperature sensor at a frequency of 1kHz. Simultaneously, it calculates the cooling medium mass flow rate based on the opening degree of the flow regulating valve. After filtering, the acquired signals are substituted into the energy balance equation to calculate the cumulative heat of reaction. Then, based on the cumulative heat of reaction, the resin temperature signal, and the shear rate of the stirrer, the dynamic viscosity prediction value is calculated using a dynamic viscosity prediction model. Subsequently, based on the dynamic viscosity prediction value... The deviation from the target viscosity and the rate of change of accumulated reaction heat over time are used to calculate the target rotational speed using a target rotational speed command calculation formula, while simultaneously generating a cooling medium flow rate adjustment value. The controller adjusts the output frequency of the variable frequency drive motor according to the target rotational speed value to achieve real-time adjustment of the stirrer speed, and controls the opening of the flow regulating valve according to the cooling medium flow rate adjustment value to achieve real-time adjustment of the cooling medium flow rate. Simultaneously, the controller calculates the estimated average bubble radius in real time. When the estimated average bubble radius is greater than a radius threshold, the ultrasonic transducer array and the low-frequency pressure pulsating pump are activated to drive and remove bubbles; when the estimated average bubble radius is less than the radius threshold, the bubble driving and removal operation is stopped. The entire control process is executed uninterruptedly, with each module working collaboratively to achieve comprehensive, real-time control of reaction exothermics, viscosity changes, and bubble generation during resin mixing.

[0033] The carbon fiber coating resin mixing management system in this embodiment achieves real-time coordinated control of reaction exothermics and viscosity during the thermosetting resin mixing process through the collaborative work of various hardware units and the controller algorithm module. This ensures that the resin viscosity remains stable near the target value required for coating throughout the mixing process, avoiding coating defects caused by viscosity runaway. Multi-point temperature monitoring is achieved through a thermocouple array distributed along the mixing vessel axis, improving the representativeness of temperature acquisition and making the calculation of reaction heat accumulation and dynamic viscosity more accurate. Direct measurement of the stirrer's mechanical power using a torque sensor avoids the influence of motor efficiency fluctuations and harmonic interference, improving the accuracy of reaction heat accumulation calculation and making the control system response more reliable. The increased heat exchange area through a spiral coil cooling jacket, combined with precise measurement of the temperature difference of the cooling medium by inlet and outlet temperature sensors, provides accurate data for energy balance calculations, further enhancing the reaction heat accumulation. The system achieves high reliability through calculations. By integrating the target rotational speed command calculation formula with feedback, feedforward, and integral compensation, it enables advanced control of resin viscosity, significantly improving control response speed and stability. Based on the energy balance equation of the first law of thermodynamics, it achieves low-cost online estimation of accumulated reaction heat without the need for expensive testing instruments. A dynamic viscosity prediction model integrating thermal, chemical, and flow effects can accurately track complex changes in resin viscosity during mixing in real time, providing reliable data for control command generation. An active bubble removal module effectively removes microbubbles generated during mixing, improving the density and interfacial bonding strength of the coated carbon fiber composite material and reducing pinhole defects. A complete closed-loop control process enables fully automated control from signal acquisition and data calculation to command execution, enhancing the intelligence level and product quality stability of carbon fiber coating production.

[0034] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A resin mixing and management system for carbon fiber coating, characterized in that, include: A mixing vessel; a stirrer disposed inside the mixing vessel; A variable frequency drive motor is connected to the stirrer; A temperature sensor, installed on the inner wall of the mixing vessel, is used to collect the temperature signal of the resin inside the vessel. A power sensor, connected to a variable frequency drive motor, is used to collect the real-time drive power signal of the stirrer. A cooling jacket covers the outer wall of the mixing vessel. A flow regulating valve is installed on the cooling medium inlet pipe of the cooling jacket. A controller is electrically connected to the temperature sensor, power sensor, variable frequency drive motor, and flow regulating valve. The controller is configured to: calculate the cumulative heat of reaction based on the real-time drive power signal, the resin temperature signal, the inlet and outlet temperatures of the cooling medium in the cooling jacket, and the mass flow rate of the cooling medium; and predict the dynamic viscosity based on the cumulative heat of reaction, the resin temperature signal, and the shear rate of the stirrer. The target speed command and cooling flow rate adjustment command are calculated based on the deviation between the dynamic viscosity and the target viscosity and the time change rate of the accumulated heat of reaction. The target speed command is output to the variable frequency drive motor, and the cooling flow rate adjustment command is output to the flow rate regulating valve.

2. The resin mixing and management system for carbon fiber coating according to claim 1, characterized in that, The temperature sensor is a thermocouple array, which contains at least three thermocouples distributed along the axial direction of the mixing vessel.

3. The resin mixing and management system for carbon fiber coating according to claim 1, characterized in that, The power sensor is a torque sensor, which is installed between the output shaft of the variable frequency drive motor and the input shaft of the agitator.

4. The resin mixing and management system for carbon fiber coating according to claim 1, characterized in that, The cooling jacket is a spiral coil type jacket. The cooling medium inlet and cooling medium outlet of the cooling jacket are respectively equipped with a first temperature sensor and a second temperature sensor. Both the first temperature sensor and the second temperature sensor are electrically connected to the controller.

5. The resin mixing and management system for carbon fiber coating according to claim 1, characterized in that, The controller calculates the target speed command. Use the following formula: ； in The dimension is revolutions per minute. The reference speed is measured in revolutions per minute. The target viscosity is expressed in Pascal-seconds. The viscosity is dynamic and its dimension is Pascal-second. It is the stirring power exponent and is dimensionless. The heat release rate suppression coefficient is expressed in seconds per joule. The time-varying rate of change of the cumulative heat of reaction, in watts. The integral coefficient for cooling is given by revolutions per fenelvin. The time-varying rate of change of the resin's temperature signal is expressed in Kelvin per second. It is the adiabatic temperature rise rate, with dimensions in Kelvin per second.

6. The resin mixing and management system for carbon fiber coating according to claim 1, characterized in that, The controller calculates the cumulative heat of reaction using the energy balance principle: the time integral of the real-time drive power signal minus the energy consumed by the resin heating and the heat carried away by the cooling medium equals the cumulative heat released by the reaction.

7. The resin mixing and management system for carbon fiber coating according to claim 1, characterized in that, The controller predicts dynamic viscosity by using a product of a temperature-dependent exponential model, a linear correction term for the accumulated heat of reaction, and a shear rate-dependent power-law model.

8. A control method for a resin mixing management system for carbon fiber coating, applied to the resin mixing management system for carbon fiber coating as described in any one of claims 1-7, characterized in that, Includes the following steps: Step S1: The controller collects the real-time drive power signal output by the power sensor, the resin temperature signal output by the temperature sensor, the inlet temperature of the cooling medium in the cooling jacket, the outlet temperature of the cooling medium, and the mass flow rate of the cooling medium in real time. Step S2: The controller calculates the cumulative heat of reaction based on the data collected in step S1. Step S3: The controller calculates the predicted dynamic viscosity value based on the accumulated heat of reaction, the resin temperature signal, and the shear rate of the stirrer. In step S4, the controller calculates the target rotational speed and cooling medium flow rate adjustment value based on the deviation between the predicted dynamic viscosity and the target viscosity and the time change rate of the accumulated reaction heat. It adjusts the output frequency of the variable frequency drive motor according to the target rotational speed value and controls the opening of the flow regulating valve according to the cooling medium flow rate adjustment value.

9. The control method for the resin mixing management system for carbon fiber coating according to claim 8, characterized in that, In step S2, the cumulative heat of reaction is calculated using the energy balance equation: the time integral of the real-time drive power signal is equal to the sum of the sensible heat of the resin, the heat carried away by the cooling medium, and the cumulative heat of reaction. The sensible heat of the resin is obtained by the integral of the product of the resin mass, the resin specific heat capacity, and the time change rate of the resin temperature signal. The heat carried away by the cooling medium is obtained by the integral of the product of the mass flow rate of the cooling medium, the specific heat capacity of the cooling medium, and the difference between the outlet temperature and the inlet temperature of the cooling medium.

10. The resin mixing and management system for carbon fiber coating according to claim 1, characterized in that, It also includes an ultrasonic transducer array and a low-frequency pressure pulsating pump. The ultrasonic transducer array is installed on the outer wall of the mixing vessel and electrically connected to the controller. The outlet of the low-frequency pressure pulsating pump is connected to the inside of the mixing vessel and electrically connected to the controller. The controller is also configured to calculate the estimated average bubble radius based on the dynamic viscosity and the current rotation speed of the stirrer. When the estimated average bubble radius is greater than the radius threshold, the controller starts the ultrasonic transducer array to emit a standing wave signal with a frequency equal to the bubble resonance frequency, and at the same time starts the low-frequency pressure pulsating pump to apply pressure pulsation to the mixing vessel.

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