Pressure-assisted resin injection molding method for composite material molding
By vacuum bagging of the reinforcing material preform and using a resin pressure sensor, combined with negative and positive pressure control, the problems of resin penetration uniformity and product thickness control in the VARI process were solved, achieving high-precision molding of composite materials.
Patent Information
- Application Number
- CN202511416642.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2025-12-12
AI Technical Summary
The existing VARI process presents challenges in controlling resin penetration uniformity and wetting the preform, resulting in defects such as low product thickness control accuracy, poor uniformity, and easy formation of dense pores.
The reinforcing material preform is encapsulated in a vacuum bag, and resin permeation is monitored by a resin pressure sensor. By combining negative and positive pressure control, the resin permeation pressure is adjusted to match the capillary pressure, thereby achieving uniform resin permeation and product thickness control.
It achieves uniform resin penetration and precise control of product thickness, suppresses dense pore defects, and is suitable for non-destructive quality and thickness accuracy control of complex structures and heterogeneous materials.
Smart Images
Figure CN121105427A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of resin-based fiber composite materials, and particularly relates to a pressure-assisted resin injection molding method for composite material molding. BACKGROUND
[0002] Vacuum assisted resin infusion (VARI) is a process of preparing a fiber preform on a single rigid mold and then introducing resin to infiltrate the preform. This method is a typical composite non-heat tank manufacturing technology, which has the advantages of low cost and high efficiency, and has a wide application and good development prospect in the fields of aerospace, wind power, shipbuilding, etc.
[0003] Since the VARI process has the characteristic of "online resin infiltration", the resin infiltration and product molding occur continuously, therefore, how to control the uniform and appropriate resin infiltration of the preform is the key and difficulty of the technology. On the one hand, the sufficiency of resin infiltration determines the lossless quality of the product; research shows that there is a difference in the filling driving force of resin between the intra-bundle and inter-bundle of the fiber bundle, the intra-bundle infiltration is mainly driven by capillary action, and the inter-bundle infiltration is mainly driven by viscous flow, and the mismatch between the two will cause uneven intra-bundle and inter-bundle infiltration, and further form defects such as dense pores. On the other hand, the process of resin infiltrating the preform affects the mechanical response behavior of the reinforcing material preform, and further affects the thickness of the product; there are problems such as low thickness control precision and poor thickness uniformity along the resin infiltration direction. SUMMARY
[0004] The present application provides a pressure-assisted resin injection molding method for composite material molding, to solve the technical difficulties of resin penetration uniformity control and preform infiltration in the existing VARI process.
[0005] The technical scheme of the present application is as follows: the present application provides a pressure-assisted resin injection molding method for composite material molding, which comprises the following steps: Step 1: vacuum bagging the reinforcing material preform, glue injection channel and glue outlet channel on the mold, and arranging a plurality of resin pressure sensors in the vacuum bag; Step 2: resin flows into the vacuum bag through the glue injection channel, and at the same time, negative pressure is applied above the vacuum bag; after the resin completely infiltrates the reinforcing material preform, the resin flows out from the glue outlet channel; the negative pressure is removed and the glue injection channel is closed; Step 3: before the resin is cured, a positive pressure is applied above the vacuum bag, so that part of the resin is discharged from the glue outlet channel; after the positive pressure is maintained for a predetermined time, the glue outlet channel is closed, and a composite material product is obtained by curing.
[0006] Optionally, in the pressure-assisted resin injection molding method for composite material molding as described above, in step 2, the negative pressure applied above the vacuum bag is as follows: During the application of negative pressure, the pressure monitored by the resin pressure sensor, i.e., the resin permeation pressure, is equal to the capillary pressure within the preform fiber bundle.
[0007] Optionally, in the pressure-assisted resin injection molding method for composite material molding as described above, the capillary pressure P within the preform fiber bundle... c The calculation method is as follows: ; Among them, V f To increase the fiber volume fraction in the preform, σ surf Let D be the surface tension of the resin, θ be the contact angle between the resin and the fiber, and D be the surface tension of the resin. f The diameter of the fiber. Porosity.
[0008] Optionally, in the pressure-assisted resin injection molding method for composite material molding as described above, before step 3, the method further includes: S1, Determine the material parameters of the preform, and determine the positive pressure P applied to the vacuum bag in step 3 based on the target thickness and the material parameters of the preform. t .
[0009] Optionally, in the pressure-assisted resin injection molding method for composite material molding as described above, in step S1, the positive pressure P above the vacuum bag is determined. t The methods include: S11, Prepare a wet preform sample identical to the preform, perform a compression test, and record the strain. With actual stress ,Sure Critical strain linearly related to true stress ,Sure The attenuation coefficient b of the compressive modulus with strain in the nonlinear region of true stress; Where h0 is the thickness of the preform sample before compression, h t The thickness measured at time t during the compression test. Let A0 be the pressure at time t during the compression test, and A0 be the area of the preform specimen subjected to pressure. The relationship between the actual stress and the nonlinear correlation region is expressed as: ; S12, Calculate the normal force applied in step 3: ; Wherein, h is the target thickness of the composite product, the strain of the preform sample after applying positive pressure E0 is the compression modulus of the wet preform sample in the linear stage of the compression process; when |ε|≤|ε0|, b=0; when |ε|>|ε0|, b is determined by the wet compression test, P0 is the vacuum pressure in the vacuum bag before applying positive pressure.
[0010] Optionally, in the pressure-assisted resin injection molding method for composite material molding as described above, before the step 3, further comprising: S2, determining the pressure holding time of the positive pressure applied to the vacuum bag in step 3, comprising: during the process of applying positive pressure to the vacuum bag, based on the relationship between the preform thickness and the positive pressure application time, the pressure holding time corresponding to the target thickness is determined.
[0011] Optionally, in the pressure-assisted resin injection molding method for composite material molding as described above, the way of determining the pressure holding time in S2, comprising: By solving the following differential equation, the preform sample thickness-time curve h(t) is drawn according to the result, and the time when the thickness reaches the target thickness h on the curve h(t) is determined as the pressure holding time: ; Wherein, K0 is the permeability when the preform sample thickness is h0, is the porosity when the preform sample thickness is h0, μ resin is the resin viscosity; when |ε|≤|ε0|, b=0; when |ε|>|ε0|, b is determined by the wet compression test.
[0012] Optionally, in the pressure-assisted resin injection molding method for composite material molding as described above, the step 1 comprises: According to the partition of different thicknesses, materials and structures in the composite material product to be formed, the vacuum bag is divided into different partitions based on the partition of the product, and the negative pressure, positive pressure and pressure holding time can be independently controlled when the pressure is applied to each partition of the vacuum bag, and at least one resin pressure sensor is provided in the vacuum bag corresponding to each partition position.
[0013] The beneficial effects of the present application are: the present application provides a pressure-assisted resin injection molding method for composite material forming, after the reinforcing material preform, glue injection channel and glue outlet channel are vacuum sealed and packaged on the mold by a vacuum bag, the resin flows into the vacuum bag from the glue injection channel, negative pressure is applied to the upper part of the vacuum bag during the resin infiltration process, the resin is promoted to quickly and fully infiltrate, and the resin infiltration pressure is matched with the capillary pressure, the resin fully infiltrates the reinforcing material preform and then flows out from the glue outlet channel, the negative pressure is removed and the glue injection channel is closed; after the infiltration is completed, before the resin is cured, positive pressure is applied to the upper part of the vacuum bag, so that part of the resin is discharged from the glue outlet channel, the positive pressure is maintained for a preset time, then the glue outlet channel is closed, and the composite material product is obtained by curing, so that the control of the product thickness accuracy is realized. Further, the technical scheme provided by the present application can divide the product into regions according to the material, thickness and structure, and perform regional pressure control accordingly, so that the accurate control of the non-destructive quality and thickness accuracy of the complex structure product can be realized. The technical scheme provided by the present application has the following beneficial effects: Firstly, the non-destructive quality of the product is improved, the negative pressure of the vacuum bag during resin infiltration is adjusted, the resin pressure is matched with the capillary pressure, the uniform control of the resin macroscopic and microscopic flow front is realized, and the formation of dense pore defects is inhibited. Secondly, the thickness accuracy of the product is improved, the scheme of controlling the preform thickness by positive pressure and pressure maintaining time is proposed, and the pressure-thickness model is established, so that the thickness accuracy of the composite material product obtained by molding is high, and the thickness uniformity is good.
[0014] Thirdly, the adaptability is strong, the pressure can be regionally adjusted according to the product structure, material and other characteristics, and the accurate control of the non-destructive quality and thickness accuracy of the variable thickness, complex structure and heterogeneous material product can be realized. DETAILED DESCRIPTION
[0015] The accompanying drawings are used to provide a further understanding of the technical scheme of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical scheme of the present application, and do not constitute a limitation on the technical scheme of the present application.
[0016] Figure 1 A flow chart of a pressure-assisted resin injection molding method for composite material forming is provided for the embodiments of the present application; Figure 2 The compression test results of the sample of the embodiment 2 of the present application; Figure 3 The thickness-time curve of the sample of the embodiment 2 of the present application; Figure 4 The schematic diagram of the thickness change trend of the sample of the embodiment 1, the comparative example 1 and the embodiment 2 of the present application with the distance of the glue injection channel.
Claims
1. A pressure-assisted resin injection molding method for composite material molding, characterized in that, Includes the following steps: Step 1: Vacuum-sealed preform of reinforcing material, glue injection channel and glue dispensing channel on mold using a vacuum bag, wherein multiple resin pressure sensors are installed inside the vacuum bag; Step 2: The resin flows into the vacuum bag through the injection channel, and a negative pressure is applied above the vacuum bag. After the resin has completely penetrated the reinforcing material preform, it flows out from the outlet channel. The negative pressure is then removed and the injection channel is closed. Step 3: Before the resin cures, apply positive pressure to the top of the vacuum bag to discharge some resin from the dispensing channel. After maintaining the positive pressure for a preset time, close the dispensing channel and cure to obtain the composite material product.
2. The pressure-assisted resin injection molding method for composite material molding according to claim 1, characterized in that, In step 2, the negative pressure is applied above the vacuum bag in the following way: During the application of negative pressure, the pressure monitored by the resin pressure sensor, i.e., the resin permeation pressure, is equal to the capillary pressure within the preform fiber bundle.
3. The pressure-assisted resin injection molding method for composite material molding according to claim 2, characterized in that, The capillary pressure P within the preform fiber bundle c The calculation method is as follows: ； Among them, V f To increase the fiber volume fraction in the preform, σ surf Let D be the surface tension of the resin, θ be the contact angle between the resin and the fiber, and D be the surface tension of the resin. f The diameter of the fiber. Porosity.
4. The pressure-assisted resin injection molding method for composite material molding according to any one of claims 1 to 3, characterized in that, Before step 3, the following are also included: S1, determine the material parameters of the preform, and determine the positive pressure P applied to the vacuum bag in step 3 based on the target thickness and the material parameters of the preform. t .
5. The pressure-assisted resin injection molding method for composite material molding according to claim 4, characterized in that, In S1, the positive pressure P above the vacuum bag is determined. t The methods include: S11, Prepare a wet preform sample identical to the preform, perform a compression test, and record the strain. With actual stress ,Sure Critical strain linearly related to true stress ,Sure The attenuation coefficient b of the compressive modulus with strain in the nonlinear region of true stress; Where h0 is the thickness of the preform sample before compression, h t The thickness measured at time t during the compression test. Let A0 be the pressure at time t during the compression test, and A0 be the area of the preform specimen subjected to pressure. The relationship between the actual stress and the nonlinear correlation region is expressed as: ; S12, Calculate the normal force applied in step 3: ； Where h is the target thickness of the composite material product, and the strain of the preform sample after applying positive pressure. E0 is the compression modulus of the wet preform sample during the linear stage of compression; when |ε|≤|ε0|, b=0; when |ε|>|ε0|, b is determined by the wet compression test; P0 is the vacuum pressure inside the vacuum bag before applying positive pressure.
6. The pressure-assisted resin injection molding method for composite material molding according to claim 4, characterized in that, Before step 3, the following are also included: S2, Determine the pressure holding time for applying positive pressure to the vacuum bag in step 3, including: during the process of applying positive pressure to the vacuum bag, determine the pressure holding time corresponding to the target thickness based on the relationship between the preform thickness and the positive pressure application time.
7. The pressure-assisted resin injection molding method for composite material molding according to claim 6, characterized in that, The method for determining the pressure holding time in S2 includes: By solving the following differential equation, the thickness-time curve h(t) of the preform sample is plotted based on the results. The time it takes for the thickness to reach the target thickness h is determined from the curve h(t) as the pressure holding time. ； Wherein, K0 is the permeability when the thickness of the preform sample is h0. The porosity is μ when the thickness of the preform sample is h0. resin ε is the resin viscosity; when |ε|≤|ε0|, b=0; when |ε|>|ε0|, b is determined by wet compression test.
8. The pressure-assisted resin injection molding method for composite material molding according to claim 7, characterized in that, Step 1 includes: The composite material product to be molded is divided into different sections based on its thickness, material, and structure. The vacuum bag is then divided into different sections based on the product's sections. During steps 2 and 3, when pressure is applied to each section of the vacuum bag, the negative pressure, positive pressure, and pressure holding time can be independently controlled. At least one resin pressure sensor is installed in the vacuum bag corresponding to each section.