GIS plate type insulating pull rod RTM process defect control method

Abstract

This invention discloses a defect control method for the RTM process of GIS plate-type insulating tie rods, belonging to the field of insulating tie rod design technology. The method includes constructing a simulation model of the GIS plate-type insulating tie rod RTM process; setting the physical field of the simulation model and performing mesh generation and control; simulating the flow process of the resin mixture in the RTM process based on the simulation model to obtain flow behavior data; obtaining the pressure field distribution characteristics and temperature field distribution characteristics of the resin mixture during the flow process; and analyzing the defect areas and their causes based on the flow behavior data, pressure field distribution characteristics, and temperature field distribution characteristics, and formulating process optimization methods. This invention provides theoretical support and simulation tools for the precise design, intelligent manufacturing, and defect control of plate-type tie rods, improving the consistency and engineering reliability of products; it also has methodological promotion value in the simulation modeling and multi-physics collaborative analysis of GIS-specific composite material insulating components.

Description

Technical Field

[0001] This invention relates to the field of insulating tie rod design technology, and in particular to a method for controlling defects in the RTM process of GIS plate-type insulating tie rods. Background Technology

[0002] As my country's power system develops towards ultra-high voltage and large capacity, gas-insulated switchgear (GIS) is widely used in urban core substations, underground transmission projects, and large-scale transmission and transformation hubs due to its excellent insulation performance, small footprint, and high operational stability. Insulating tie rods, as a typical support structure, are mainly used to connect the conductor system to the outer shell, achieving structural positioning, mechanical load-bearing, and electrical isolation. Their performance directly affects the overall operational reliability and safety stability of the GIS.

[0003] Currently, plate-type insulating tie rods are mainly made of glass fiber reinforced epoxy resin (GFRP) composite materials. Resin transfer molding (RTM), as a closed-mold, low-pressure, and highly controllable liquid molding technology, has gradually become the preferred process for molding large-size composite structures in recent years. In the RTM process, the fiber preform is first laid in a closed mold, and then the resin mixture is injected through a pre-set injection path, achieving penetration, curing, and part molding under certain temperature and pressure.

[0004] However, the flow and curing process of resin mixtures in RTM (Resin Molding Method) is extremely complex, especially for plate-type tie rods, which have large thicknesses, complex edges and corners, and non-uniform fiber arrangement. The resin mixture filling process often suffers from defects such as uneven penetration, flow dead zones, air trapping, and incomplete wetting. These problems directly lead to decreased insulation performance, structural stress concentration, and accelerated localized thermal aging, seriously threatening the operational safety of the equipment. Therefore, understanding the flow mechanism of resin mixtures in plate-type structures, the influence of fiber weaving methods on the penetration path, the evolution of the temperature-pressure field, and its coupling effect with the curing reaction has become a key technical issue for promoting the upgrading of GIS structure manufacturing. Summary of the Invention

[0005] The purpose of this invention is to provide a method for controlling defects in the RTM process of GIS plate-type insulated tie rods, revealing the mechanism of filling defects, proposing feasible structural and process optimization strategies, providing theoretical support and simulation tools for the precise design, intelligent manufacturing and defect control of plate-type tie rods, and improving the consistency and engineering reliability of products.

[0006] To achieve the above objectives, this invention provides a method for controlling defects in the RTM process of GIS plate-type insulated tie rods, comprising the following steps: S1. Construct a simulation model of the RTM process for GIS-type plate-type insulated tie rods; S2. Set the physical field for the simulation model and perform mesh generation and control; S3. Based on the simulation model, simulate the flow process of the resin mixture in the RTM process and obtain flow behavior data, including the flow characteristics of the resin mixture in the initial injection stage, the stage with gap flow as the main flow mode, and the stage with fiber penetration as the main flow mode; introduce a correlation model between temperature, degree of cure and viscosity of resin mixture, set dynamic viscosity that changes with temperature and degree of curing reaction, and substitute the calculated real-time viscosity into the Brinkman equation and energy conservation equation for joint solution, so that the simulation model closely approximates the real flow process of resin mixture; S4. Obtain the pressure field distribution characteristics and temperature field distribution characteristics during the flow process of the resin mixture; S5. Based on flow behavior data, pressure field distribution characteristics, and temperature field distribution characteristics, analyze the defect areas and their causes, and formulate process optimization methods.

[0007] Preferably, in S1, the simulation model considers the symmetry of the GIS plate-type insulating tie rod and the constraints of the mold structure. It selects the central core, fiberglass layer, and edge limiting assembly as the main structural units for geometric abstraction, ensuring the complete preservation of key structures and simplifying the internal non-flowing regions to reduce computational complexity and focus on the permeation behavior of the resin mixture in the fiberglass medium. The simplified RTM flow domain mainly includes the following parts: Glass fiber region: Represents the glass fiber filling layer in the tie rod, defined as a porous medium region, used to simulate the percolation behavior of resin mixtures under different layup thicknesses and weaving methods; Mold cavity wall: Represents the solid structure of the mold, set as an impermeable and fixed boundary, which plays a role in constraining and guiding the resin mixture; Inlet channel: Several glue injection ports are set on the inlet side of the tie rod to simulate the glue injection path in the actual RTM process, and constant pressure and constant flow rate boundary conditions can be applied; Gap area: Defines the tiny cavity between the preform and the inner wall of the mold, reflecting the area that is difficult to fit completely during the actual laying process, and is used to capture the flow of the mold wall and the phenomenon of rapid bypass. Exhaust channel: Several exhaust ports are arranged on the outlet side of the tie rod to discharge residual gas during the injection process, which is set as a free outflow boundary.

[0008] Preferably, the physical field settings in S2 specifically involve loading physical field modules into the simulation model, namely the Brinkman equation module, the horizontal set module in the porous medium, and the fluid heat transfer module. The Brinkman equation module is used to describe the low Reynolds number non-Darcy flow behavior of resin mixtures in glass fiber regions, taking into account pore resistance and viscous shear terms. The horizontal aggregation module in the porous medium is used to track the flow interface between the resin mixture and air during the infusion process, and dynamically reflect the change process of the resin mixture filling area. The fluid heat transfer module is used to simulate the temperature distribution of the resin mixture during the injection process.

[0009] Preferably, in S2, the meshing and control specifically involves meshing the simulation model after the physical field is set up. Free triangular meshes are used to divide the injection port and exhaust port into meshes. Sweeping is used to mesh the injection cylinder, glass fiber laying part and gap part in the fluid flow direction. After the meshing is completed, the mesh near the injection cylinder and the outlet is densified to improve the simulation accuracy.

[0010] Preferably, the features of the three stages for acquiring flow behavior data in S3 specifically include the following: Initial injection stage: Record the behavior of the resin mixture after being injected from the injection port, preferentially forming "gap-first flow" along the gap area, and initially spreading laterally to both sides of the injection surface; The gap flow-dominated stage: the process of tracking the rapid diffusion of the resin mixture along the gap, with the edge outlet flowing out first and the middle outlet lags behind, and the resin mixture in the gap area forming a serrated advance before gradually smoothing out. Fiber infiltration-dominated stage: Record the transition of resin mixture from interstitial flow to slow infiltration inside glass fiber, the main infusion interface from a serrated shape to a flat shape, and the synergistic flow characteristics of resin mixture infiltrating laterally from the edge interstitial spaces to the center of the mold cavity.

[0011] Preferably, in S3, the implementation process of the association model is as follows: A model of the curing kinetics of resin mixtures was constructed using the Domain Ordinary Differential Equation (ODE) interface in COMSOL to achieve spatiotemporal tracking of the degree of curing α across the entire field. The transient degree of curing obtained from the ODE and the temperature field obtained from the energy equation were substituted as independent variables into the Castro-Macosko viscosity algebraic equation, thereby updating the fluid viscosity parameters in the Brinkman equation within each simulation step. The Castro-Macosko viscosity algebraic equation is as follows: ; in, The apparent viscosity of the resin mixture; T The absolute temperature of the system; Indicates the conversion rate of the reaction; A It is a pre-factor related to material properties;T a Activation temperature; It is the gel point conversion rate; while B and C It is a dimensionless fitting constant that describes the contribution of molecular chain growth and crosslinking to viscosity.

[0012] Preferably, the specific content of S4 is to organize the pressure value distribution, pressure gradient change, spatial location and range of high pressure zone and low pressure zone at different time points, and summarize the pressure field distribution law; organize the temperature value distribution, temperature difference gradient, temperature change trend of key area at different time points, and summarize the evolution law of temperature field affected by external heating, material thermal conductivity difference and resin mixture flow.

[0013] Preferably, S5 specifically includes the following steps: S51. Defect area location: Based on the simulation results of the simulation model, extract the flow behavior data, pressure field and temperature field distribution characteristics of the entire resin mixture injection process, and combine the resin mixture volume fraction distribution image to identify the potential defect locations, including unwetted areas and air gap concentration areas, and determine the main defect concentration areas. S52. Analyze the causes of defects in the main areas where defects are concentrated and in the resin mixture pouring stage. S53. Coupled analysis of key influencing factors: Verify the effects of fiber weaving method, temperature, viscosity, impregnation time, injection pressure, and part thickness on defects one by one. Combine the simulation results under different parameters to clarify the effects of each factor and summarize the logic of defect formation. S54. Introduce a "gradient permeability" prefabricated design. Based on the incomplete impregnation area located by the simulation model, change the uniform fiber laying method of the fully insulating parts, adjust the density of fiber weaving, set a low permeability in the areas where dry spot defects are prone to occur, guide the resin mixture to preferentially fill the weak impregnation area, and solve the dry spot and bubble problems that are prone to occur in heavy parts.

[0014] Preferably, the Brinkman equation module is modeled based on the Brinkman equations, which include the momentum conservation equation and the mass conservation equation, as follows: Momentum conservation equation: ; in, The dynamic viscosity of the resin mixture. For velocity vector field, For density, t For time, For pressure, To account for the equivalent viscosity affected by fluid shear stress, K For penetration rate; mass conservation equation: ; The level set module in the porous medium is based on the level set method, and its governing equation is: Interface transfer equations, including re-initialization: ; in, For level set functions, =1 represents the resin mixture phase. =0 represents the air phase. Controlling the interface thickness For reinitialization factors; The temperature control equation in the fluid heat transfer module is an energy conservation equation: ; in, T For temperature, c p Specific heat capacity; Effective thermal conductivity, Q This is the volumetric heat source term.

[0015] Therefore, this invention adopts the above-mentioned defect control method for RTM process of GIS plate-type insulated tie rod, and constructs an RTM process simulation model of GIS composite insulated tie rod structure. The model includes glass fiber structure, mold cavity, injection port and vent, etc., reflecting the geometric characteristics of each typical area of ​​tie rod structure; simulates the three-dimensional flow and wetting behavior of resin mixture in anisotropic porous structure inside preform, clearly tracking the front advancement path, unwetted area and its evolution process; simulates the typical temperature field and pressure field distribution characteristics in RTM process, showing that the pressure gradually decreases along the flow path after resin mixture injection, and the temperature field is affected by mold heating and low temperature resin mixture flow, forming temperature disturbances at the flow front and inlet area; through defect area extraction and volume fraction analysis, it is found that the area between injection ports, the middle outlet area and the middle area of ​​glass fiber laying are high-risk areas for forming "dry spots" and "gas entrapment", and the defect distribution is jointly controlled by structural complexity and flow non-uniformity.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 Here are a) a geometric model and b) a cross-sectional view of the plate-type insulating tie rod according to an embodiment of the present invention; Figure 2 The following are embodiments of the present invention: a) a mesh partitioning diagram of the insulating tie rod; b) a side view of the mesh division; c) a mesh refinement diagram of the glue injection port area. Figure 3This is a flow diagram of the resin mixture during the initial injection in an embodiment of the present invention; Figure 4 This is a flow diagram of a resin mixture with predominantly gap flow according to an embodiment of the present invention; Figure 5 This is a flow diagram of a resin mixture under joint control of slit-porous media according to an embodiment of the present invention; Figure 6 This is the pressure field distribution of the insulating tie rod during 0-10s according to an embodiment of the present invention; Figure 7 This is the pressure field distribution of the insulating tie rod at 100s according to an embodiment of the present invention; Figure 8 This is the pressure field distribution of the insulating tie rod when the resin mixture is filled according to an embodiment of the present invention; Figure 9 This is a cross-sectional view of the pressure field of the insulating tie rod when the resin mixture is filled according to an embodiment of the present invention; Figure 10 These are the temperature fields of the resin mixture at different times after injection according to an embodiment of the present invention; Figure 11 This is a cross-sectional view of the temperature field after the resin mixture is injected according to an embodiment of the present invention; Figure 12 This is a flow diagram of the resin mixture at the injection inlet in an embodiment of the present invention; Figure 13 This is a flow diagram of the resin mixture at the injection inlet gap in an embodiment of the present invention. Figure 14 This is a diagram showing that the resin mixture at the end corner of an embodiment of the present invention is not fully impregnated. Figure 15 This is a flow diagram of the resin mixture at the outlet of an embodiment of the present invention; Figure 16 This is a flow diagram of the resin mixture at the end of the casting process according to an embodiment of the present invention; Figure 17 This is the image of the unfilled central region at 5300s in this embodiment of the invention; Figure 18 This is the image of the unfilled central region at 7900s in this embodiment of the invention; Figure 19 This describes the injection of resin mixtures of different viscosities at 500 seconds according to an embodiment of the present invention. Figure 20 This is a cross-sectional view of resin mixtures of different viscosities injected at 500s according to an embodiment of the present invention; Figure 21 This is a defect diagram of the intermediate region at different immersion times according to an embodiment of the present invention; Figure 22 These are cross-sectional views of defects at different injection pressures according to an embodiment of the present invention; Figure 23 These are the geometric models of the present invention after the thickness is reduced and the thickness is increased. Figure 24 This is a flow diagram of the resin mixture at the inlet at the same time when the thickness is 0.048m, 0.058m, and 0.068m according to an embodiment of the present invention; Figure 25 These are defect diagrams taken at the same time when the thickness is 0.048m, 0.058m, and 0.068m according to embodiments of the present invention. Figure 26 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] Example 1 This invention provides a method for controlling defects in the RTM process of GIS plate-type insulated tie rods, the process of which is as follows: Figure 26 As shown, it includes the following steps: S1. Construct a simulation model of the RTM process for GIS-type plate-type insulated tie rods.

[0021] Plate-type insulating tie rods, as key internal support and insulation components of UHV GIS equipment, typically consist of a central insulating core, multiple outer glass fiber reinforcement layers, end metal inserts, and a mold cavity limiting structure. During the resin transfer molding (RTM) process, the resin mixture needs to fully penetrate the entire glass fiber preform under pressure and achieve dense bonding between the layers during the curing stage. Therefore, to accurately simulate the flow behavior of the resin mixture during the injection process, it is necessary to construct a representative three-dimensional flow model.

[0022] This embodiment considers the symmetry of the GIS plate-type insulating tie rod and the constraints of the mold structure. The central core, fiberglass layer, and edge limiting assembly are selected as the main structural units for geometric abstraction, ensuring the complete preservation of key structures and simplifying the internal non-flowing regions to reduce computational complexity and focus on the permeation behavior of the resin mixture in the fiberglass medium. The simplified RTM flow domain mainly includes the following parts: Glass fiber region: Represents the glass fiber filling layer in the tie rod, defined as a porous medium region, used to simulate the percolation behavior of resin mixtures under different layup thicknesses and weaving methods; Mold cavity wall: Represents the solid structure of the mold, set as an impermeable and fixed boundary, which plays a role in constraining and guiding the resin mixture; Inlet channel: Several glue injection ports are set on the inlet side of the tie rod to simulate the glue injection path in the actual RTM process, and constant pressure and constant flow rate boundary conditions can be applied; Gap area: Defines the tiny cavity between the preform and the inner wall of the mold, reflecting the area that is difficult to fit completely during the actual laying process, and is used to capture the flow of the mold wall and the phenomenon of rapid bypass. Exhaust channel: Several exhaust ports are arranged on the outlet side of the tie rod to discharge residual gas during the injection process, which is set as a free outflow boundary.

[0023] The model constructed in this embodiment is as follows: Figure 1 As shown, (a) is the three-dimensional structure of the model, and (b) is a cross-sectional view; the injection cylinder is used to connect the glue injection port, and there are 5 glue injection ports and 5 vent ports.

[0024] S2. Set up the physics field for the simulation model and perform mesh generation and control. Specifically, the physics field setting involves loading physics modules into the simulation model, namely the Brinkman equation module, the horizontal mass module in the porous medium, and the fluid heat transfer module.

[0025] The Brinkman equations module describes the low Reynolds number non-Darcy flow behavior of resin mixtures within glass fiber regions, considering porosity resistance and viscous shear terms. The module is based on the Brinkman equations, which include momentum conservation and mass conservation equations, as detailed below: Momentum conservation equation: ; in, The dynamic viscosity of the resin mixture. For velocity vector field, For density, t For time, For pressure, To account for the equivalent viscosity affected by fluid shear stress, K For penetration rate; mass conservation equation: .

[0026] The level set module in porous media is used to track the flow interface between the resin mixture and air during infusion, dynamically reflecting the changes in the resin mixture filling area. The level set module in porous media is based on the level set method, and its governing equation is: Interface transfer equations, including re-initialization: ; in, For level set functions, =1 represents the resin mixture phase. =0 represents the air phase. Controlling the interface thickness This is a reinitialization factor.

[0027] The fluid heat transfer module is used to simulate the temperature distribution of the resin mixture during the infusion process; the temperature control equation in the fluid heat transfer module is the energy conservation equation: ; in, T For temperature, c p Specific heat capacity; Effective thermal conductivity, Q This is the volumetric heat source term.

[0028] The specific flow conditions and parameters in this embodiment are shown in the table below:

[0029] After the physics field is set up, the simulation model is meshed. Free triangular meshes are used for the injection port and vent. Then, sweeping meshes are applied to the injection barrel, fiberglass layup, and gaps along the fluid flow direction. After meshing, the mesh near the injection barrel and outlet is refined to improve simulation accuracy. Specifically... Figure 2 As shown, (a) is the mesh partitioning diagram of the simulation model, (b) is the side view of the mesh partitioning, and (c) is the mesh refinement diagram of the glue injection port area.

[0030] S3. Simulate the flow process of the resin mixture in the RTM process based on a simulation model to obtain flow behavior data, including the flow characteristics of the resin mixture in the initial injection stage, the stage where gap flow is the main flow mode, and the stage where fiber penetration is the main flow mode. Introduce a correlation model between temperature, degree of cure, and resin mixture viscosity, set a dynamic viscosity that varies with temperature and degree of curing reaction, and substitute the calculated real-time viscosity into the Brinkman equation and energy conservation equation for joint solution, so that the simulation model closely approximates the real resin mixture flow process. Specifically, this includes the following: Initial injection stage: Record the behavior of the resin mixture after being injected from the injection port, preferentially forming "gap-first flow" along the gap area, and initially spreading laterally to both sides of the injection surface; The gap flow-dominated stage: the process of tracking the rapid diffusion of the resin mixture along the gap, with the edge outlet flowing out first and the middle outlet lags behind, and the resin mixture in the gap area forming a serrated advance before gradually smoothing out. Fiber infiltration-dominated stage: Record the transition of resin mixture from interstitial flow to slow infiltration inside glass fiber, the main infusion interface from a serrated shape to a flat shape, and the synergistic flow characteristics of resin mixture infiltrating laterally from the edge interstitial spaces to the center of the mold cavity.

[0031] The implementation process of the association model is as follows: A model of the curing kinetics of resin mixtures was constructed using the Domain Ordinary Differential Equation (ODE) interface in COMSOL to achieve spatiotemporal tracking of the degree of curing α across the entire field. The transient degree of curing obtained from the ODE and the temperature field obtained from the energy equation were substituted as independent variables into the Castro-Macosko viscosity algebraic equation, thereby updating the fluid viscosity parameters in the Brinkman equation within each simulation step. The Castro-Macosko viscosity algebraic equation is as follows: ; in, The apparent viscosity of the resin mixture; T The absolute temperature of the system; Indicates the conversion rate of the reaction; A It is a pre-factor related to material properties; T a Activation temperature; It is the gel point conversion rate; while B and C It is a dimensionless fitting constant that describes the contribution of molecular chain growth and crosslinking to viscosity.

[0032] In this embodiment, the flow behavior results at each stage are as follows: Initial injection phase, such as Figure 3As shown, the color bars represent the volume fraction of the resin mixture. Initially, the resin mixture is contained within the injection barrel and has not yet entered the fiber preform structure. As the injection process begins, driven by a set pressure differential, the resin mixture is slowly injected into the mold cavity through the injection port. Due to the presence of tiny gaps between the mold cavity and the fiberglass preform, and the low flow resistance in this area, the resin mixture preferentially advances along these gaps, forming a distinct "gap-first flow" phenomenon. After the leading edge of the resin mixture contacts the fiber preform, the fluid is blocked and diverted by local flow channels, and begins to expand to both sides of the injection surface, forming preliminary lateral spreading behavior. At this stage, the main flow is concentrated in the gap area, and the penetration into the porous fiber interior is not yet significant.

[0033] The gap flow-dominant stage, such as Figure 4 As shown, the color bars represent the volume fraction of the resin mixture. As injection time progresses, the resin mixture fully enters the mold cavity. During this stage, the flow behavior is dominated by the gap between the glass fiber preform and the mold cavity wall. Due to the presence of a significant low-resistance channel in this area, the resin mixture exhibits a rapid diffusion trend within the gap. After reaching the fiber zone, the resin mixture preferentially flows out from the two outermost outlets. A small portion of the resin mixture that does not flow out from these two outlets continues to flow towards the center, exiting from the three outlets in the middle. This results in a significantly faster flow velocity at the outlet edge area compared to the central area. Simultaneously, the propulsion speed of the resin mixture in the central area slows down significantly, creating a "lag" in the injection of the central outlet area.

[0034] Furthermore, as the resin mixture continuously enters, the glass fibers begin to be impregnated. Due to the presence of multiple independent injection ports, a typical serrated advancement structure of the resin mixture front can be observed in the gap region. Each injection port corresponds to a main flow path, resulting in periodic bulges in the flow front laterally. This spatial non-uniformity causes local areas to contact the glass fibers first, while other areas lag behind. As the injection time increases, the flow fronts between multiple injection points gradually expand and merge, and the originally distinct serrated boundaries are gradually filled, with the front shape tending towards a smooth transition. During this process, the main seepage path remains concentrated in the gap region, and truly effective large-area infiltration has not yet fully formed.

[0035] Fiber penetration-dominant stage, such as Figure 5As shown, the color bars represent the volume fraction of the resin mixture. The resin mixture flow gradually transitions from rapid filling of the initial gaps to slow seepage within the fiber region, forming a typical injection behavior controlled by a combination of gap and porous media. Initially, the resin mixture is propelled forward along the main injection channel by multiple injection ports and rapidly distributed to the front of the mold cavity through the tiny gaps between the mold and the fiber. Due to uneven distribution of injection ports and differences in local flow resistance, the early resin mixture front exhibits obvious irregular advancement, forming a serrated injection boundary along the flow direction. As the injection process progresses, the resin mixture in each channel gradually achieves a balanced advancement speed, the serrated front begins to converge and tends to become uniform, and the entire main injection interface gradually flattens out, transitioning into a stable and continuously advancing flow boundary. At this point, the flow front exhibits strong directionality and pressure control in the mold channel, gradually advancing along the direction from the injection port to the vent, forming the main flow path of the injection.

[0036] Simultaneously, the resin mixture in the gaps around the mold edges begins to slowly permeate into the glass fiber while being injected into the main path. Driven by the boundary pressure difference and lateral permeation, the resin mixture remaining in the edge gaps expands towards the center of the mold cavity at a relatively low speed, gradually forming a lateral permeation network. This dual mechanism causes the flow front to gradually approach the outlet in the in-plane direction, while in the normal direction, the permeation into the fiber gradually expands.

[0037] The resin mixture gradually fills the glass fiber preform under the combined action of main channel injection and edge gap seepage, with the injection front showing a gradual saturation process from the boundary to the center. The seepage path within the fiber region is microscopically affected by the material's pore structure and fiber arrangement, resulting in a relatively complex overall seepage morphology, but macroscopically maintaining the continuity and hierarchy of the propagation direction.

[0038] S4. Obtain the pressure field distribution characteristics and temperature field distribution characteristics during the flow process of the resin mixture; specifically, organize the pressure value distribution, pressure gradient change, spatial location and range of high pressure zone and low pressure zone at different time points, and summarize the pressure field distribution law; organize the temperature value distribution, temperature difference gradient, temperature change trend of key areas at different time points, and summarize the evolution law of temperature field affected by external heating, material thermal conductivity difference and resin mixture flow.

[0039] The pressure field analysis process in this embodiment is as follows: The resin mixture enters the mold cavity through the injection port at a constant inlet pressure of 0.6 MPa and gradually propels forward through the glass fiber zone. The mold cavity vent is a vacuum to maintain a reasonable pressure gradient and promote gas escape.

[0040] In the initial stage of infusion, such as Figure 6 , Figure 7As shown, the color bars all represent pressure. Figure 6 The pressure field distribution of the insulating tie rod from 0 to 10 seconds; Figure 7 The pressure field distribution of the insulating tie rod is shown at 100s. The resin mixture is slowly injected into the mold from the bottom injection port. Since a continuous flow channel has not yet formed inside the mold cavity, the pressure in the inlet area rises rapidly, forming a localized high-pressure zone. At this time, the pressure field distribution is highly concentrated, with almost all the pressure concentrated near the injection port. As the resin mixture begins to advance into the mold cavity, the pressure gradually increases along its path, while the unfilled areas remain at low pressure. Therefore, the entire mold cavity forms a pressure gradient that gradually decreases from the injection port to the injection front, and the pressure field evolves essentially synchronously with the flow front.

[0041] After the resin mixture enters the slit channel, it spreads rapidly in the tiny gaps between the mold and the glass fiber. These slit regions have lower resistance and higher local flow velocities, resulting in a relatively faster pressure drop. At this stage, the high-pressure zone remains concentrated in the central region of the flow path, extending continuously from the injection port to the leading edge. In the middle stage, the resin mixture advances further, and the injection area gradually expands. The pressure field changes significantly accordingly. The high-pressure zone moves forward as the injection path extends, and the area of ​​the high-pressure zone originally near the injection port begins to shrink, elongating the pressure gradient band. Due to the flow resistance of the porous fiber medium in the flow path, the propagation velocity of the resin mixture within the fiber region decreases, resulting in a more significant pressure drop at the leading edge, forming a band-shaped low-pressure expansion zone. The injection leading edge is represented as a clear gradient band in the pressure field diagram, with an unfilled low-pressure area in front and a filled stable area behind. Near the end of the injection process, the resin mixture almost fills the entire mold cavity, and the flow velocity decreases significantly. Figure 8 , Figure 9 As shown, Figure 8 This describes the pressure field distribution of the insulating tie rod when it is filled with resin mixture. Figure 9 This is the corresponding pressure field profile; at this point, the entire pressure field gradually approaches equilibrium. Except for a slight pressure difference between the inlet and outlet ends to maintain limited flow, the pressure changes in the remaining areas are very slow, exhibiting a relatively uniform and stable distribution. The pressure gradient is no longer significant.

[0042] Throughout the injection process, the pressure field changes in tandem with the advance of the flow front, gradually transitioning from initial concentrated high pressure to overall equilibrium in the later stages. The process of the resin mixture filling the mold cavity is also a process in which pressure gradually expands and tends to become uniform in space.

[0043] The temperature field analysis process in this embodiment is as follows: The thermal boundary conditions are set to maintain the external temperature of the mold at 90°C, the initial temperature of the internal glass fiber at 80°C, and the temperature of the resin mixture injected at the inlet at 45°C.

[0044] like Figure 10 The figure shows the temperature field at different times after the resin mixture is injected. The color bars represent temperature in Kelvin. In the initial stage of injection, the temperature field mainly shows a heat transfer trend from the outside to the inside. Since the gap area is close to the mold wall, it first exchanges heat with the external heat source, so its temperature rises rapidly. In contrast, the glass fiber area, due to its lower thermal conductivity and higher heat capacity, experiences a relatively slow heating process, forming a significant temperature difference transition.

[0045] As the infusion process proceeds, a low-temperature resin mixture is continuously injected from the inlet, its temperature significantly lower than that of the glass fiber and the mold. Initially, the gap area is filled with the resin mixture first, resulting in a significant drop in local temperature and the formation of a relatively continuous low-temperature channel along the gap. Subsequently, the resin mixture gradually penetrates into the glass fiber area, where its temperature gradually rises due to heat transfer. In the middle and later stages, the overall temperature of the glass fiber gradually converges with that of the mold, while the temperature in the gap area remains slightly lower than that of the glass fiber and the mold body due to the continuous flow of the resin mixture, forming a relatively stable temperature gradient. This difference not only affects the local viscosity of the resin mixture but also indirectly influences its flow resistance and wetting behavior. Figure 11 As shown in the temperature profile, the temperature at the resin mixture inlet is always the lowest, and the temperature gradually increases with the flow direction. The temperature contour lines show a clear "high at the front and low at the back" characteristic, reflecting the heat transfer process under the combined action of heat conduction and convection.

[0046] The temperature field change reflects the temperature evolution characteristics under the combined effects of external heating, differences in the thermal conductivity of materials, and injection of low-temperature resin mixtures.

[0047] S5. Based on flow behavior data, pressure field distribution characteristics, and temperature field distribution characteristics, analyze the defect areas and their causes, and formulate process optimization methods. This specifically includes the following steps: S51. Defect area location: Based on the simulation results of the simulation model, extract the flow behavior data, pressure field and temperature field distribution characteristics of the entire resin mixture injection process, and combine the resin mixture volume fraction distribution image to identify the potential defect locations, including unwetted areas and air gap concentration areas, and determine the main defect concentration areas. S52. Analyze the causes of defects in the main areas where defects are concentrated and in the resin mixture pouring stage. S53. Coupled analysis of key influencing factors: Verify the effects of fiber weaving method, temperature, viscosity, impregnation time, injection pressure, and part thickness on defects one by one. Combine the simulation results under different parameters to clarify the effects of each factor and summarize the logic of defect formation. S54. Introducing a "gradient permeability" prefabricated design, based on the incomplete impregnation areas located by the simulation model, the uniform fiber laying method of the fully insulating components is changed, and the density of the fiber weaving is adjusted. Low permeability is set in areas prone to dry spot defects, guiding the resin mixture to preferentially fill the weakly impregnated areas, thus solving the dry spot and bubble problems that easily occur in heavy components. For example, in the insulating tie rod example, based on the flow simulation results, the tie rod is divided into a conventional flow zone and an impregnation reinforcement zone. In the defect-prone area identified by the simulation (the middle area of ​​the insulating tie rod), the weaving method of the glass fiber layer is adjusted to a special hybrid structure with high permeability, improving its local permeability.

[0048] The simulation results in this embodiment show that the locations where defects are likely to occur during the flow of the resin mixture are mainly concentrated in three typical regions: the inlet adjacent area, the mold cavity center area, and the merging area of ​​the main leading edge and the edge seepage. The defect formation mechanisms of each type of region are different.

[0049] First, such as Figure 12 and Figure 13 As shown, Figure 12 This is a flow diagram of the resin mixture at the injection inlet during the initial injection phase. Figure 13 This diagram illustrates the flow of resin mixture at the injection port during the initial injection phase. In the initial stage after the resin mixture is injected into the mold, there is significant localized high pressure in the injection port area. Driven by the pressure difference, the resin mixture is ejected into the mold cavity at a certain velocity from the injection port. If the mold cavity structure is not conducive to the smooth diffusion of the resin mixture or if the venting channels fail to open in time, the gas between adjacent injection ports may be rapidly surrounded by the suddenly incoming resin mixture, forming a closed space and causing gas stagnation. This phenomenon of "inlet injection with gas stagnation" mainly occurs in the initial injection stage, in the middle area between injection ports, and is closely related to excessive initial velocity of the resin mixture and failure of the venting channels to open in time.

[0050] Secondly, such as Figure 14 and Figure 15 As shown, Figure 14 This image shows incomplete impregnation of the resin mixture at the end corner. Figure 15 This is a flow diagram of the resin mixture at the outlet. Insufficient resin mixture filling may occur in the central outlet area of ​​the mold cavity. Although five vents are provided at the top of the mold to release internal air, due to differences in geometry and flow resistance between the vents, the first and fifth vents are more efficient at expelling gas squeezed from the resin mixture's leading edge, while the second and fourth vents in the middle have poor venting efficiency, and the third vent has a moderate effect. This restricts the venting path in the central area of ​​the mold. When the resin mixture's leading edge approaches this area, local pressure lag occurs due to the difficulty in gas escape, resulting in a slower penetration rate of the resin mixture in the central area, easily leaving unwetted areas or residual air bubbles.

[0051] Finally, as Figure 16 The diagram shows the resin mixture flow at the end of the pouring process. As the main flow path progresses to the end, the pouring front in the injection direction gradually approaches the front of the resin mixture seeping into the gaps on both sides, and the two meet and merge in the central region of the mold. This merging process occurs at the end of the pouring process, which is the last area in the central region to be covered by the resin mixture. If the edge seepage velocity is still insufficient at this moment, and there is no effective venting path at the closing position of the front, the residual air in the central region may be trapped by the front and unable to escape, eventually forming a narrow and regularly shaped air trapping defect in the center.

[0052] In this embodiment, during the molding process of the insulating tie rod, parameters such as injection conditions, fiber weaving method, preheating temperature, and preform thickness have a significant impact on the flow behavior and defect distribution of the resin mixture. Injection conditions are the main external factor driving the flow of the resin mixture within the mold cavity. If the injection speed is too fast, fluctuations are likely to occur at the leading edge of the resin mixture, leading to gas entrainment and trapping in the complex structure; while too low an injection pressure may result in restricted flow and incomplete filling, especially in the far end of the preform or dense areas, where blank unwetted areas are likely to form. The fiber weaving method directly determines the porosity and permeability of the glass fiber preform. Different weaving structures differ significantly in yarn arrangement, degree of interlacing, and interlayer channel structure, thereby affecting the permeation rate and path of the resin mixture in the porous medium. Overly dense weaving may improve mechanical properties, but it will also exacerbate local flow resistance, making it easy for the resin mixture to accumulate or flow around internally, causing retention defects in the central part. The preheating temperature of the mold and fiber preform significantly affects the flowability of the resin mixture. A reasonable temperature gradient helps reduce the viscosity of the resin mixture, improves wettability, and avoids viscosity increases, resin stagnation, or even premature gelation due to localized cooling. Furthermore, variations in the thickness of the preform not only affect the flow channel dimensions of the mold cavity but also alter the local pressure gradient. Excessively thick areas may lead to delayed filling or even air trapping, resulting in the typical "air trapping in thick areas" problem. Therefore, when setting process parameters, it is necessary to consider both material properties and geometry, coordinating the matching of injection power and penetration resistance to suppress the generation and propagation of defects.

[0053] This embodiment analyzes the above reasons one by one, and the specific process is as follows.

[0054] 1) Analysis of the impact of weaving method on defects During the epoxy resin mixture infusion process, glass fibers with different weaving methods exhibit significant differences in structural characteristics. Among these, the most direct parameter affecting flow behavior is the permeability of the fiber layer. The weaving method, by altering the arrangement of yarns in the in-plane and thickness directions, regulates the pore connectivity and flow channel structure within the fiber preform, directly influencing the permeation rate and path of the resin mixture within it. To analyze the impact of different weaving methods on wetting behavior and defect distribution, this embodiment selected three typical weaving methods: plain weave, twill weave, and biaxial weave, with a corresponding permeability of 2.916 × 10⁻⁶. -10 m 2 0.398×10 -10 m 2 0.672×10 -10 m 2 .

[0055] Figure 17 The diagram illustrates the morphology of the unwetted area during the intermediate stage (5300s) of three weaving methods. It can be observed that, at the same time interval, higher permeability leads to faster resin mixture propagation, resulting in the unwetted area being closer to the outlet. Plain weave, with its highest permeability, has the shortest unwetted area in the length direction, closest to the outlet, and exhibits a distinct "wider at the top, narrower at the bottom" shape. This morphology indicates that the high-pressure area near the inlet allows the resin mixture to penetrate preferentially in the central region, while the periphery experiences less pressure, leading to a slower penetration and a propagation profile where the center penetrates first and the edges lag behind. In contrast, the lower permeability twill weave and biaxial structure propagate more slowly overall, but their unwetted areas are more regular, and their leading edge morphology is flatter. Figure 18 The results show the defect distribution at the final impregnation stage (7900s). It is clear that higher penetration results in a smaller unimpregnated area and a better final impregnation effect. The plain weave structure exhibits the most complete resin mixture distribution and the fewest residual defects, demonstrating excellent impregnation performance. In contrast, the twill and biaxial weave structures still show some degree of residual resin or insufficient saturation in the central area.

[0056] A comprehensive analysis of the two sets of images demonstrates that higher permeability contributes to improved overall resin mixture infusion efficiency. Although initial edge-progress lag may occur, it ultimately achieves more complete wetting, significantly reducing potential defects. Therefore, under the conditions of this infusion system and parameters, the plain weave structure performs optimally and is recommended as the preferred choice. Of course, the final selection of the weave method must also consider the comprehensive mechanical and electrical performance requirements of the material.

[0057] 2) Analysis of the influence of temperature / viscosity on defects During the resin mixture pouring process, temperature indirectly affects the flow behavior mainly by controlling the viscosity of the resin mixture. To further investigate the impact of temperature changes on pouring defects, this embodiment selects three different viscosity conditions for comparative analysis. Figure 19 The spatial distribution of the resin mixture in the preform at different viscosities is shown at 500s. Figure 20 This is the corresponding volume fraction cross-sectional view.

[0058] As can be observed from the figure, with decreasing viscosity, the overall propulsion speed of the resin mixture increases significantly, the wetting area becomes larger, and the unwetted portion is closer to the outlet direction. This indicates that low-viscosity resin mixtures are more conducive to penetrating the internal pores of the preform in a shorter time, thus improving wetting efficiency. Under high viscosity conditions, flow restriction is more pronounced, the overall propulsion area is shorter, unsaturated areas are concentrated near the inlet, and even a significant residual gas area forms below the inlet. This suggests that high viscosity is detrimental to venting and uniform propulsion of the resin mixture front.

[0059] Further analysis of the cross-sectional images reveals that lower viscosity results in a more uniform and evenly distributed injection front along the channel direction, facilitating smooth gas escape. Conversely, higher viscosity tends to trap air gaps at the junctions of gaps and fibers, increasing the risk of residual adhesive or voids. Overall, lower viscosity helps improve flowability, enhance filler integrity, and reduce the probability of defects. It is important to note that viscosity reduction often depends on increased resin mixture temperature, and high-temperature environments simultaneously accelerate the curing reaction rate of the epoxy system. Therefore, in actual injection processes, curing behavior must be considered in conjunction with the process to ensure a harmonious balance between flowability and reaction rate within a reasonable window, thereby achieving high-quality molding.

[0060] 3) Analysis of the influence of immersion time on defects Figure 21 The evolution of defects in the central region of the mold cavity is shown under different injection times (7200s, 7900s, 8700s, 9700s).

[0061] At the initial time point (7200s), a distinct, elongated unfilled area was observed in the center, exhibiting significant color differences and a clean, well-defined shape, indicating that this area had not yet been effectively filled by the resin mixture. Because this area was located at the intersection of the various injection ports and the edge penetration paths, the resin mixture had not yet converged there, thus creating a relatively persistent residual air gap. As time progressed to 7900s, the outline of the defect area became blurred, indicating that the resin mixture had gradually penetrated it. At this stage, the resin mixture continued to extend from both ends of the mold cavity towards the center, with some of the resin mixture from the injection ports and edge channels merging here, and the previously closed blank area began to be invaded. The length of the unfilled area shortened significantly, but a thin, elongated shape remained. At 8700s, the coverage area of ​​the resin mixture further expanded, leaving only a small, blurred unfilled mark in the center, its shape no longer regular. At this point, the resin mixture advancing from the injection ports converged with the seepage from the gaps on both sides, slowly filling the central area. The defect was almost completely eliminated, and the overall filling was nearly complete. By 9700s, the defects were no longer visible, and the central area of ​​the entire mold cavity was the same color as the sides, indicating that the area had been completely impregnated. The previously remaining cavities had been filled by the slowly penetrating resin mixture, with a uniform color and no obvious air gaps.

[0062] As can be seen from the figure, the extension of the impregnation time helps the resin mixture cover the central area, improves the local blank areas caused by the initial flow path deviation or the difference in seepage velocity on both sides, and the central area is gradually filled in and the defects are "squeezed out".

[0063] 4) Analysis of the influence of injection pressure on defects In the molding process of liquid composite materials, injection pressure is one of the key process parameters affecting the flow rate of the resin mixture and the final wetting quality. This example selects three typical injection pressure levels: 0.4 MPa, 0.6 MPa, and 0.8 MPa. Figure 22 (From left to right) The effects of different injection pressures on the distribution of resin mixtures and potential defects under otherwise identical conditions are compared and analyzed, with a particular focus on the flow state in the gap area near the injection port.

[0064] from Figure 22It can be observed that the filling capacity of the resin mixture in the mold inlet area is significantly enhanced with the gradual increase of injection pressure. At an injection pressure of 0.4 MPa, the resin mixture propagates slowly within the gap, easily forming stagnant areas between adjacent injection ports, especially at the interface between the gap and the glass fiber, where obvious unwetted air gaps exist, indicating poor venting and insufficient resin mixture penetration. When the injection pressure increases to 0.6 MPa, the resin mixture advances more rapidly, the filling area between the injection ports widens significantly, some of the previously residual gas is effectively expelled, and the air gap distribution in the gap area is significantly reduced, indicating that the injection pressure at this point is sufficient to overcome the flow resistance caused by the glass fiber structure and improve local wetting. At an injection pressure of 0.8 MPa, the resin mixture exhibits stronger mold filling capacity, with virtually no obvious air gap residue at the interface between the gap and the glass fiber, and the inlet area is fully filled with resin mixture. The injection process is more continuous, and the leading edge propagation is smoother, showing superior venting and wetting characteristics.

[0065] Further analysis revealed that as injection pressure increased, the unwetted portion in the central region at the end of the injection gradually moved closer to the mold exit, indicating that the resin mixture could be pushed deeper into the far end of the mold cavity. This morphological change made it easier for gas to escape through the still-unclosed leading edge region, effectively reducing the risk of central air pockets or closure defects. Furthermore, high injection pressure not only increased the flow velocity at the inlet but also raised the average pressure level along the entire flow path, significantly enhancing the resin mixture's propulsion capability near the exit region. This overall increase in pressure differential helped improve flow continuity and wetting integrity throughout the entire injection system.

[0066] In summary, appropriately increasing the injection pressure helps improve the penetration ability of the resin mixture, especially in areas with complex fiber structures or narrow gaps. It can effectively reduce trapped gas and wetting blind spots, and improve the filling effect in the middle area during the later stages of injection, thereby improving the overall wetting quality.

[0067] 5) Analysis of the influence of thickness on defects To investigate the effects of different thicknesses on the impregnation process and defect distribution of resin mixtures, the following observations can be drawn from three aspects: geometric model, flow behavior, and defect morphology: Figure 23 The figure shows the changes in geometric modeling after decreasing and increasing the thickness. As can be seen from the figure, while keeping the number and location of the injection ports and other boundary conditions constant, changing only the part thickness will directly affect the distribution of the resin mixture in the channel and the change in flow resistance. Figure 24This study demonstrates the flow of resin mixtures in the inlet region under different thicknesses (0.048 m, 0.058 m, and 0.068 m) at the same time point. With increasing thickness, the depth of the resin mixture entering the mold cavity decreases, and the color distribution at the inlet becomes more concentrated, indicating greater flow resistance. For the thinner mold cavity (0.048 m), the resin mixture exhibits a better diffusion trend in the initial injection stage, with a significantly deeper penetration depth at the inlet. In contrast, the thicker mold cavity (0.068 m) shows weaker penetration ability within the same time frame, with a narrower leading edge and slower propagation speed at the inlet. Figure 25 The distribution of defect areas under the same impregnation time is shown for three different thicknesses. At a thickness of 0.048 μm, there are almost no significant unimpregnated areas, indicating full fluid filling. However, at a thickness of 0.068 μm, a distinct unsaturated area exists in the central region, appearing as a narrow, elongated band, indicating that the resin mixture failed to completely penetrate the central area within the limited injection time, resulting in a large injection dead zone. The defect morphology at a medium thickness of 0.058 μm falls between these two extremes, demonstrating that thickness significantly affects the impregnation effect.

[0068] Based on the above analysis, it can be concluded that, without considering electrical and mechanical performance limitations, reducing the thickness of the part is beneficial to improving the wetting uniformity of the resin mixture and reducing the risk of defects in the central region.

[0069] Therefore, this invention employs the aforementioned defect control method for the RTM process of GIS plate-type insulated tie rods, constructing an RTM process simulation model of the GIS composite insulated tie rod structure. The model includes a glass fiber structure, mold cavity, injection port, and vent, reflecting the geometric characteristics of typical regions of the tie rod structure. It simulates the three-dimensional flow and wetting behavior of the resin mixture within the anisotropic porous structure of the preform, clearly tracing the leading edge propagation path, unwetted areas, and their evolution. The simulation obtains typical temperature and pressure field distribution characteristics during the RTM process, showing the gradual pressure increase along the flow path after resin mixture injection. The temperature field gradually decreases, influenced by both mold heating and the flow of the low-temperature resin mixture, resulting in temperature disturbances at the flow front and inlet area. Defect region extraction and volume fraction analysis revealed that the areas between injection ports, the intermediate outlet area, and the middle area of ​​the glass fiber layer are high-risk areas prone to "dry spots" and "air pockets." Defect distribution is jointly controlled by structural complexity and flow inhomogeneity. The effects of fiber weaving method, temperature, viscosity, wetting time, injection pressure, and part thickness on defects were verified one by one. Combined with simulation results under different parameters, the effects of each factor were clarified, and the logic of defect formation was summarized.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for controlling defects in the RTM process of GIS panel-type insulated tie rods, characterized in that, Includes the following steps: S1. Construct a simulation model of the RTM process for GIS-type plate-type insulated tie rods; S2. Set the physical field for the simulation model and perform mesh generation and control; S3. Based on the simulation model, simulate the flow process of the resin mixture in the RTM process and obtain flow behavior data, including the flow characteristics of the resin mixture in the initial injection stage, the stage with gap flow as the main flow mode, and the stage with fiber penetration as the main flow mode; introduce a correlation model between temperature, degree of cure and viscosity of resin mixture, set dynamic viscosity that changes with temperature and degree of curing reaction, and substitute the calculated real-time viscosity into the Brinkman equation and energy conservation equation for joint solution, so that the simulation model closely approximates the real flow process of resin mixture; S4. Obtain the pressure field distribution characteristics and temperature field distribution characteristics during the flow process of the resin mixture; S5. Based on flow behavior data, pressure field distribution characteristics, and temperature field distribution characteristics, analyze the defect areas and their causes, and formulate process optimization methods.

2. The method for controlling defects in the RTM process of GIS plate-type insulating tie rods according to claim 1, characterized in that, In S1, the simulation model considers the symmetry of the GIS plate-type insulating tie rod and the constraints of the mold structure. It selects the central core, fiberglass layer, and edge limiting assembly as the main structural units for geometric abstraction, ensuring the complete preservation of key structures and simplifying the internal non-flowing regions to reduce computational complexity and focus on the permeation behavior of the resin mixture in the fiberglass medium. The simplified RTM flow domain mainly includes the following parts: Glass fiber region: Represents the glass fiber filling layer in the tie rod, defined as a porous medium region, used to simulate the percolation behavior of resin mixtures under different layup thicknesses and weaving methods; Mold cavity wall: Represents the solid structure of the mold, set as an impermeable and fixed boundary, which plays a role in constraining and guiding the resin mixture; Inlet channel: Several glue injection ports are set on the inlet side of the pull rod to simulate the glue injection path in the actual RTM process, and constant pressure and constant flow rate boundary conditions can be applied; Gap area: Defines the tiny cavity between the preform and the inner wall of the mold, reflecting the area that is difficult to fit completely during the actual laying process, and is used to capture the flow of the mold wall and the phenomenon of rapid bypass. Exhaust channel: Several exhaust ports are arranged on the outlet side of the tie rod to discharge residual gas during the injection process, which is set as a free outflow boundary.

3. The method for controlling defects in the RTM process of GIS plate-type insulating tie rods according to claim 2, characterized in that, In S2, the physical field settings specifically involve loading physical field modules into the simulation model, namely the Brinkman equation module, the horizontal collection module in the porous medium, and the fluid heat transfer module. The Brinkman equation module is used to describe the low Reynolds number non-Darcy flow behavior of resin mixtures in glass fiber regions, taking into account pore resistance and viscous shear terms. The horizontal aggregation module in the porous medium is used to track the flow interface between the resin mixture and air during the infusion process, and dynamically reflect the change process of the resin mixture filling area. The fluid heat transfer module is used to simulate the temperature distribution of the resin mixture during the injection process.

4. The method for controlling defects in the RTM process of GIS plate-type insulating tie rods according to claim 3, characterized in that, In S2, mesh generation and control specifically involve meshing the simulation model after the physical field is set up. Free triangular meshes are used to divide the injection port and vent into meshes. Sweep meshes are used to divide the injection cylinder, glass fiber laying section and gap section into meshes in the fluid flow direction. After the meshing is completed, the mesh near the injection cylinder and outlet is refined to improve the simulation accuracy.

5. The method for controlling defects in the RTM process of GIS plate-type insulating tie rods according to claim 4, characterized in that, The specific features of the three-stage acquisition of flow behavior data in S3 include the following: Initial injection stage: Record the behavior of the resin mixture after being injected from the injection port, preferentially forming "gap-first flow" along the gap area, and initially spreading laterally to both sides of the injection surface; The gap flow-dominated stage: the process of tracking the rapid diffusion of the resin mixture along the gap, with the edge outlet flowing out first and the middle outlet lags behind, and the resin mixture in the gap area forming a serrated advance before gradually smoothing out. Fiber infiltration-dominated stage: Record the transition of resin mixture from interstitial flow to slow infiltration inside glass fiber, the main infusion interface from a serrated shape to a flat shape, and the synergistic flow characteristics of resin mixture infiltrating laterally from the edge interstitial spaces to the center of the mold cavity.

6. The method for controlling defects in the RTM process of GIS plate-type insulating tie rods according to claim 5, characterized in that, In S3, the implementation process of the association model is as follows: A model of the curing kinetics of resin mixtures was constructed using the Domain Ordinary Differential Equation (ODE) interface in COMSOL to achieve spatiotemporal tracking of the degree of curing α across the entire field. The transient degree of curing obtained from the ODE and the temperature field obtained from the energy equation were substituted as independent variables into the Castro-Macosko viscosity algebraic equation, thereby updating the fluid viscosity parameters in the Brinkman equation within each simulation step. The Castro-Macosko viscosity algebraic equation is as follows: ； in, The apparent viscosity of the resin mixture; T The absolute temperature of the system; Indicates the conversion rate of the reaction; A It is a pre-factor related to material properties; T a Activation temperature; It is the gel point conversion rate; while B and C It is a dimensionless fitting constant that describes the contribution of molecular chain growth and crosslinking to viscosity.

7. The method for controlling defects in the RTM process of GIS plate-type insulating tie rods according to claim 6, characterized in that, S4 specifically includes compiling the pressure value distribution, pressure gradient changes, and spatial location and range of high-pressure and low-pressure zones at different time points, summarizing the pressure field distribution patterns; compiling the temperature value distribution, temperature difference gradient, and temperature change trends in key areas at different time points, summarizing the evolution patterns of the temperature field affected by external heating, material thermal conductivity differences, and resin mixture flow.

8. The method for controlling defects in the RTM process of GIS plate-type insulating tie rods according to claim 7, characterized in that, S5 specifically includes the following steps: S51. Defect area location: Based on the simulation results of the simulation model, extract the flow behavior data, pressure field and temperature field distribution characteristics of the entire resin mixture injection process, and combine the resin mixture volume fraction distribution image to identify the potential defect locations, including unwetted areas and air gap concentration areas, and determine the main defect concentration areas. S52. Analyze the causes of defects in the main areas where defects are concentrated and in the resin mixture pouring stage. S53. Coupled analysis of key influencing factors: Verify the effects of fiber weaving method, temperature, viscosity, impregnation time, injection pressure, and part thickness on defects one by one. Combine the simulation results under different parameters to clarify the effects of each factor and summarize the logic of defect formation. S54. Introduce the "gradient permeability" prefabricated design. Based on the incomplete impregnation area located by the simulation model, change the uniform fiber laying method of the fully insulating parts, adjust the density of fiber weaving, set low permeability in the areas where dry spot defects are prone to occur, guide the resin mixture to preferentially fill the weak impregnation area, and solve the dry spot and bubble problems that are prone to occur in heavy parts.

9. The method for controlling defects in the RTM process of GIS plate-type insulating tie rods according to claim 3, characterized in that, The Brinkman equation module is based on the Brinkman equations, which include the momentum conservation equation and the mass conservation equation, as follows: Momentum conservation equation: ; in, The dynamic viscosity of the resin mixture. For velocity vector field, For density, t For time, For pressure, To account for the equivalent viscosity affected by fluid shear stress, K For penetration rate; mass conservation equation: ; The level set module in the porous medium is based on the level set method, and its governing equation is: Interface transfer equations, including re-initialization: ； in, For level set functions, =1 represents the resin mixture phase. =0 represents the air phase. Controlling the interface thickness For reinitialization factors; The temperature control equation in the fluid heat transfer module is an energy conservation equation: ； in, T For temperature, c p Specific heat capacity; Effective thermal conductivity, Q This is the volumetric heat source term.

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