Chopped fiber prepreg mold-pressing near-net-shape forming manufacturing process for high-quality resin-based composite material part

Abstract

The invention relates to the technical field of resin-based composite material part forming, in particular to a resin-based composite material high-quality part chopped fiber prepreg mold pressing near-net-shape forming manufacturing process which specifically comprises the steps that a part model is established, a mold cavity-mold core mold is manufactured according to a part, the use amount of chopped fiber prepreg is determined according to the size of the part, and the chopped fiber prepreg mold pressing near-net-shape forming manufacturing process is completed. The method comprises the following steps: cutting a determined amount of chopped fiber prepreg according to the size of a mold cavity, laying the cut chopped fiber prepreg in a step shape, heating a mold, applying mold closing pressure at the same time, demolding after a set mold pressing time, and carrying out post-treatment to obtain a resin-based composite material workpiece with required precision. The part manufactured through the method has the low porosity, so that the overall performance is more excellent, and the method is particularly suitable for manufacturing thick-wall composite material components with the high quality requirement.

Description

Technical Field

[0001] The present invention relates to the technical field of resin matrix composite parts molding, and particularly relates to a manufacturing process for near-net molding of short-cut fiber prepregs for high-quality resin matrix composite parts by compression molding. Background Art

[0002] Short-cut fiber prepreg is a semi-finished product in which reinforcing phase fibers are impregnated with matrix phase resin. The matrix phase is generally selected from epoxy resin, phenolic resin, unsaturated polyester resin, etc. The reinforcing phase is generally selected from short-cut carbon fiber, short-cut glass fiber, short-cut aramid fiber, short-cut basalt fiber, etc. Compared with long fiber prepreg and continuous fiber prepreg, short-cut fiber prepreg has higher fluidity and formability, is more suitable for manufacturing parts with complex shapes, and has good mechanical properties. The quality and performance of the finally obtained composite parts depend on the molding process. Therefore, based on the urgent need for lightweight and high-quality resin matrix composite parts in various fields today, it is urgent to develop a near-net molding technology for prepregs by compression molding.

[0003] Compression molding is a process of putting powdery, granular or fibrous plastics into the mold cavity at the molding temperature, and then closing the mold and applying pressure to make it form and cure. It is often used to manufacture various shaped parts or products, and has the advantages of high efficiency, precision and suitability for mass production. The main process parameters for compression molding resin matrix composite parts include compression molding temperature, compression molding pressure and compression molding time. These parameters have a crucial impact on the molding process and the quality of the final product. At present, the defects in compression molded resin matrix composite parts mainly include delamination, porosity, air holes, rich resin, poor resin, debonding, looseness, deformation and weak adhesion. Among them, the proportion of delamination is the highest, exceeding 50%, and the proportions of air holes and porosity are also relatively high. (1) Delamination: mainly caused by process problems during manufacturing, such as insufficient pressure and uneven temperature, resulting in poor interlayer bonding. (2) Porosity and air holes: not only affect the quality and appearance, but may also reduce the mechanical strength of the product. It is mainly due to the incomplete discharge of entrapped air, hygroscopic water, volatile solvents, etc., resulting in voids inside the material. (3) Rich resin and poor resin: Rich resin means too much resin, and poor resin means too little resin, usually caused by improper mold design or operation. (4) Debonding: The bonding between fibers and resin is not firm, which may be due to incomplete curing or improper temperature control. (5) Looseness: The internal structure of the material is loose, which may be due to insufficient pressure or improper temperature control during the curing process. (6) Deformation and weak adhesion: The shape of the part changes or the interlayer bonding force is insufficient, which may be caused by unreasonable mold design or improper operation. The ultimate result caused by these defects is the deterioration of the mechanical properties of the molded part.

[0004] At present, the manufacturing of resin matrix composite parts based on prepregs often relies on manual experience and static settings for temperature and pressure control, and cannot flexibly respond to the changes of complex molds and different resin materials, resulting in uneven temperature distribution and unstable pressure, thus affecting the quality and mechanical properties of the formed parts. Therefore, the exploration of the forming process for complex structural parts and relatively thick resin matrix composite parts is one of the important current directions.

[0005] In summary, developing an economic, efficient and high-quality compression molding near-net-shape forming process for chopped fiber prepregs has important significance and application value. Summary of the Invention

[0006] In order to solve the problems that the control of temperature and pressure during the manufacturing of resin matrix composite prepreg parts currently only relies on manual experience and static settings, resulting in deterioration of the mechanical properties of the obtained parts, etc., the present invention provides a manufacturing technology for chopped fiber prepreg compression molding near-net-shape forming of high-quality resin matrix composite parts.

[0007] The present invention is realized through the following technical solutions: The manufacturing process for chopped fiber prepreg compression molding near-net-shape forming of high-quality resin matrix composite parts includes the following steps:

[0008] S1. Establish a part model, use the reaction compression molding module in plastic molding simulation software to couple and simulate the temperature and pressure during the compression molding process and obtain the coupling relationship, and obtain the optimal mold closing window through the front temperature distribution of the chopped fiber prepreg under different mold closing pressures and in combination with the curing reaction rate;

[0009] S2. Manufacture a cavity-core mold according to the part. The cavity volume of the mold is calculated based on the volume compensation formula;

[0010] The volume compensation formula is:

[0011]

[0012] Where: V m is the cavity volume of the mold, V p is the part volume, S v is the volume curing shrinkage rate of the matrix resin of the chopped fiber prepreg;

[0013] S3. Obtain the dosage of the chopped fiber prepreg according to m = V m × ρ × Ke; where: V m is the cavity volume of the mold, ρ is the density of the chopped fiber prepreg, and Ke is the loss coefficient, usually taking 1.02 - 1.10;

[0014] S4. Cut the chopped fiber prepreg in a determined amount according to the cavity size of the mold, and make the size of the chopped fiber prepreg corresponding to the largest cross-sectional part of the part 60-80% of the corresponding mold cavity size, while the sizes of the chopped fiber prepregs corresponding to other parts of the part are gradually reduced; lay the cut chopped fiber prepregs in a stepped manner to facilitate the removal of gas during the compression molding process;

[0015] S5. Heat the mold to a temperature 10-20°C lower than the compression molding temperature, then place the stepped chopped fiber prepreg obtained in step S4 in the mold and place temperature sensors and pressure sensors on each surface and the center position of the chopped fiber prepreg;

[0016] S6. Heat the mold and simultaneously apply the clamping pressure obtained in step S1, monitor the pressure data in real time and dynamically adjust the pressure. When the temperature distribution along the edge is uniform and resin overflows at the mold edge, first slowly release a pressure not exceeding 10% of the compression pressure, then pressurize to the compression pressure under the set clamping pressure, and achieve precise clamping with the help of an automated control system; the compression pressure is obtained based on the compression molding temperature in step S5 and the temperature and pressure coupling relationship obtained in step S1;

[0017] S7. Compression mold at the compression pressure and compression molding temperature, and simultaneously use the placed temperature sensors and pressure sensors to monitor each surface and the center position of the chopped fiber prepreg in real time, record the temperature change curve over time, and timely adjust the temperature through the equipment system to control the temperature difference between the center and each surface not exceeding 3°C; at the same time, monitor the coupling relationship between pressure and temperature;

[0018] S8. Demold after the compression molding time and perform post-treatment to obtain a resin matrix composite part with the required precision.

[0019] As a further improvement of the manufacturing process technical solution of the present invention, the plastic molding simulation software is Autodesk Moldflow software.

[0020] As a further improvement of the manufacturing process technical solution of the present invention, define the resin material in Autodesk Moldflow, select the curing reaction model and fiber length, set the temperature and pressure parameters, predict the porosity of the molded part by simulating the temperature distribution under different clamping pressures and combining the curing reaction rate, and obtain the optimal clamping window accordingly.

[0021] As a further improvement of the manufacturing process technical solution of the present invention, in step S1, the matrix of the chopped fiber prepreg is selected from any one or a mixture of two or more of epoxy resin, phenolic resin, and unsaturated polyester resin; the chopped fibers in the chopped fiber prepreg are selected from any one or a mixture of two or more of chopped carbon fibers, chopped glass fibers, chopped aramid fibers, and chopped basalt fibers.

[0022] As a further improvement of the manufacturing process technical solution of the present invention, in step S1, the gel temperature, curing temperature, and curing time of the resin matrix of the chopped fiber prepreg are obtained through testing, and the temperature from the curing temperature of the obtained resin matrix to the curing temperature + 20°C is used as the molding temperature, and the curing time is used as the molding time.

[0023] As a further improvement of the manufacturing process technical solution of the present invention, the gel temperature, curing temperature, and curing time of the resin matrix can be obtained by using a differential scanning calorimeter, a rheometer, and a flat knife wire drawing method. As a further improvement of the manufacturing process technical solution of the present invention, in step S2, the mold is a steel mold, an aluminum alloy mold, or a ceramic mold.

[0024] As a further improvement of the manufacturing process technical solution of the present invention, in step S2, a positioning pin is provided in the mold to ensure the uniformity of the thickness dimension of the workpiece; a pressure sensor is installed in the mold to monitor the pressure in the mold cavity in real time; a displacement sensor is installed in the mold to monitor the closing position of the mold and the resin extrusion amount in real time.

[0025] As a further improvement of the manufacturing process technical solution of the present invention, in step S6, the clamping pressure is 0.1 - 0.5 MPa.

[0026] As a further improvement of the manufacturing process technical solution of the present invention, in step S5, for the stepped chopped fiber prepreg placed in the mold, the distance from its maximum dimension to each edge of the corresponding mold cross-section is the same.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) By using plastic molding simulation software, such as Autodesk Moldflow, to simulate the flow process of the prepreg in the molding process, the number of mold trials and material waste can be reduced, and the determination of the forming process of the chopped fiber prepreg can be guided and accelerated.

[0029] (2) Adopting the stepped prepreg laying method is convenient for exhausting the gas in the molding process, thereby avoiding the appearance of pores and air holes in the workpiece.

[0030] (3) Use a multi-channel tester to precisely control the process parameters. Set temperature sensors and pressure sensors at key positions of the mold to monitor the temperature and pressure changes in the mold cavity in real time, and accurately judge the mold closing time. Through these measures, perform the mold closing operation precisely at the optimal moment when the mold closing time arrives, thereby improving product quality, reducing the production cycle and energy consumption.

[0031] (4) The components manufactured by the method of the present invention usually have a lower porosity, so the overall performance, especially the mechanical properties such as tensile strength, bending strength, etc., are more excellent, and it is particularly suitable for the preparation of composite components with thick walls and high quality requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments in line with the present invention, and are used together with the specification to explain the principles of the present invention.

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is a schematic diagram of the simple process flow of the compression molding near-net shaping of short-cut fiber pre-preg for high-quality parts of the resin matrix composite material of the present invention.

[0035] Figure 2 It is a schematic diagram of the front temperature distribution of the Autodesk Moldflow simulation in Example 1 of the present discovery.

[0036] Figure 3 It is a schematic diagram of the pore distribution of the parts formed in Example 1 of the present discovery.

[0037] Figure 4 It is a schematic diagram of the multi-channel temperature sensors laid in Example 1 of the present invention. It can be seen that Figure 4 the process of the present invention can realize the comprehensive monitoring of the temperature changes in different regions during the compression molding process.

[0038] Figure 5 It is a time-temperature graph obtained by testing the multi-channel temperature sensors in Example 1 of the present invention. It can be seen that Figure 5 during the entire compression molding process, the temperature difference between the center and each surface of the process of the present invention does not exceed 3°C, indicating that precise control of the temperature field during the molding process is achieved.

[0039] Figure 6 It is a schematic diagram of the staggered laying of short-cut fiber pre-pregs commonly used at present. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] In order to more clearly understand the above-mentioned objects, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0041] In the following description, many specific details are set forth in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only a part of the embodiments of the present invention, rather than all the embodiments.

[0042] The present invention provides specific embodiments of a manufacturing process for short-cut fiber prepreg compression near-net shaping of high-quality resin matrix composite parts, including the following steps:

[0043] S1. Establish a part model, use the reaction compression molding module in plastic molding simulation software to couple and simulate the temperature and pressure during the compression molding process to obtain the coupling relationship, and obtain the optimal mold closing window through the front temperature distribution of the short-cut fiber prepreg under different mold closing pressures and in combination with the curing reaction rate; specifically, the part model is a flat plate model, laid in a stepped manner to more accurately simulate the temperature distribution during the flow and curing of the prepreg;

[0044] S2. Manufacture a cavity-core mold according to the part, and the cavity volume of the mold is calculated based on the volume compensation formula;

[0045] The volume compensation formula is:

[0046]

[0047] Where: V m is the cavity volume of the mold, V p is the part volume, S v is the volume curing shrinkage rate of the matrix resin of the short-cut fiber prepreg;

[0048] S3. Obtain the amount of short-cut fiber prepreg according to m = V m × ρ × Ke; where: V m is the cavity volume of the mold, ρ is the density of the short-cut fiber prepreg, and Ke is the loss coefficient, usually taking 1.02 - 1.10;

[0049] S4. Cut the short-cut fiber prepreg with the determined amount according to the cavity size of the mold, and make the size of the short-cut fiber prepreg corresponding to the largest cross-sectional part of the part be 60 - 80% of the corresponding mold cavity size, and the sizes of the short-cut fiber prepreg corresponding to other parts of the part are gradually reduced; lay the cut short-cut fiber prepreg in a stepped manner to facilitate the discharge of gas during the compression molding process;

[0050] S5. Heat the mold to a temperature 10 - 20 °C lower than the molding temperature, then place the chopped fiber prepreg laid in a stepped shape obtained in step S4 in the mold and place temperature sensors and pressure sensors on each surface and the central position of the chopped fiber prepreg.

[0051] S6. Heat the mold and simultaneously apply the clamping pressure obtained in step S1, monitor the pressure data in real time and dynamically adjust the pressure. When the temperature distribution along the edge is uniform and resin overflows at the mold edge, first slowly release a pressure not exceeding 10% of the molding pressure, then pressurize to the molding pressure under the set clamping pressure, and achieve precise clamping with the aid of an automated control system; the molding pressure is obtained based on the molding temperature in step S5 and the temperature - pressure coupling relationship obtained in step S1.

[0052] S7. Molding is carried out under the molding pressure and molding temperature. At the same time, use the placed temperature sensors and pressure sensors to monitor each surface and the central position of the chopped fiber prepreg in real time, record the temperature - time change curve, and adjust the temperature in a timely manner through the equipment system to control the temperature difference between the center and each surface not exceeding 3 °C; at the same time, monitor the coupling relationship between pressure and temperature.

[0053] S8. After demolding and post - treatment after the molding time, a resin - matrix composite part with the required precision is obtained.

[0054] In an example provided by the present invention, the plastic molding simulation software is Autodesk Moldflow software. Define the resin material in Autodesk Moldflow, select the curing reaction model and fiber length, set the temperature and pressure parameters, predict the porosity of the molded part by simulating the temperature distribution under different clamping pressures and combining the curing reaction rate, and obtain the optimal clamping window accordingly.

[0055] In an example provided by the present invention, in step S1, the matrix of the chopped fiber prepreg is selected from any one or a mixture of two or more of epoxy resin, phenolic resin, and unsaturated polyester resin; the chopped fibers in the chopped fiber prepreg are selected from any one or a mixture of two or more of chopped carbon fibers, chopped glass fibers, chopped aramid fibers, and chopped basalt fibers.

[0056] In another example provided by the present invention, in step S1, the gel temperature, curing temperature, and curing time of the resin matrix of the chopped fiber prepreg are obtained through testing. The temperature range from the obtained curing temperature of the resin matrix to the curing temperature + 20 °C is used as the molding temperature, and the curing time is used as the molding time.

[0057] In an example provided by the present invention, a differential scanning calorimeter, a rheometer, and a flat knife wire drawing method can be used to obtain the gel temperature, curing temperature, and curing time of the resin matrix.

[0058] In another example provided by the present invention, in step S2, the mold is a steel mold, an aluminum alloy mold, or a ceramic mold.

[0059] In another example provided by the present invention, in step S2, a positioning pin is provided in the mold to ensure the uniformity of the thickness dimension of the workpiece; a pressure sensor is installed in the mold to monitor the pressure in the mold cavity in real time; a displacement sensor is installed in the mold to monitor the closing position of the mold and the resin extrusion amount in real time. During specific implementation, the surface of the mold cavity can be polished according to the requirements of the surface accuracy and dimensional accuracy of the workpiece.

[0060] In an example provided by the present invention, in step S6, the clamping pressure is 0.1 - 0.5 MPa.

[0061] In another example provided by the present invention, in step S5, for the stepped chopped fiber prepreg placed in the mold, the distance from its maximum dimension to each edge of the corresponding mold cross-section is the same.

[0062] The specific embodiments of the present invention will be described in detail below.

[0063] Example 1

[0064] A manufacturing process for near-net shaping of a chopped carbon fiber / epoxy resin prepreg for high-quality resin matrix composite parts, comprising the following steps:

[0065] SI. Establish a flat plate model, import the model into Autodesk Moldflow, define the material as epoxy resin, select the autocatalytic model, divide the mesh, set the starting temperature of the prepreg to 25 °C, and the molding pressure to 5 - 20 MPa (Determination reasons: First, the part size is 300×300×4 mm, and the prepreg ply thickness is 4 mm, so there is no need for high pressure to prevent fiber misalignment; Second, the resin system is a high-flow epoxy resin, and medium pressure is required for better gas exhaust; Third, the molding pressure depends on the prepreg properties, part thickness and part structure, and the epoxy prepreg is generally 5 - 20 MPa). Conduct a coupled simulation of the temperature and pressure during the compression molding process and obtain the coupling relationship; simulate the front temperature distribution of the chopped fiber prepreg under different clamping pressures and predict the porosity of the molded part in combination with the curing reaction rate; after comparison, when the clamping pressure is 0.15 MPa, the front temperature is uniform and the porosity of the molded part is the least. Therefore, determine the clamping pressure to be 0.15 MPa. The front temperature distribution under the clamping pressure of 0.15 MPa and the porosity distribution predicted by observing the front temperature distribution and combining with the curing reaction rate are shown in Figure 2 and Figure 3 respectively. The front temperature refers to the highest temperature reached by the front part of the material in the mold during the compression molding process. This temperature is crucial for controlling the molding process and ensuring the quality of the product. The level of the front temperature directly affects the fluidity of the material and the curing reaction, and thus affects the density and properties of the product. It can be seen from Figure 2 that: under the clamping pressure of 0.15 MPa, the front temperature distribution is uniform and continuously rising, and the prepreg spreads evenly in all directions.

[0066] It can be seen from Figure 3 that: the porosity of the part mainly appears at the four corners. This is because they are the areas where the resin is filled last, and the pressure transfer is weak. Therefore, after the local viscosity increases, gas cannot be effectively exhausted.

[0067] SII. The components of the prepreg are epoxy resin and chopped carbon fiber. The length of the chopped carbon fiber is 25 mm, and the content of the epoxy resin is 55%. Based on the formula V s =(V0 - V C )÷V0×100% (where: V0 is the volume of the resin matrix before curing; V C is the volume of the resin matrix after complete curing; V s is the volume curing shrinkage rate of the resin matrix), the volume curing shrinkage rate of the epoxy resin is calculated to be 3%; the part to be molded is a square plate with dimensions 300×300×4 mm and a volume of 360000 mm 3 ; the mold is a 45# steel cavity-core mold. Based on the volume compensation formula V m =V p ÷(1 - Sv )(Where: V m is the volume of the mold cavity, V p is the volume of the workpiece, S v is the volume shrinkage rate of the matrix resin of the prepreg) The calculated size of the mold cavity is 303.10×303.10×4.05 mm, and the volume is 372072 mm 3 ; According to the surface accuracy and dimensional accuracy requirements of the workpiece, the surface of the mold cavity is polished and positioning pins are set in the mold to ensure the uniformity of the thickness dimension of the workpiece; A pressure sensor is installed in the mold to monitor the pressure in the mold cavity in real time; A displacement sensor is installed in the mold to monitor the closing position of the mold and the resin extrusion amount in real time.

[0068] SIII. Determine the amount of prepreg according to m = V m ×ρ×(1.02 - 1.10); Where: V m is the volume of the mold cavity, which is 372072 mm 3 ; ρ is the density of the prepreg, which is 1.47 g / cm 3 ; According to the known knowledge of prepreg molding, the Ke loss coefficient of flat workpieces is 1.02 - 1.05, and that of complex workpieces is 1.05 - 1.10. Since the workpiece to be molded is a flat workpiece and its volume is not large, the loss coefficient is taken as 1.02; The mass of the finally used prepreg is m = 557.90 g.

[0069] SIV. Cut the determined amount of prepreg according to the mold structure, and the laying size is 80% of the mold size for the bottom layer, and the sizes of the corresponding prepregs in other parts are gradually reduced layer by layer, so that the cut prepregs are laid in a stepped shape, as Figure 1 shown, in order to facilitate the removal of gas during the molding process;

[0070] SV. Obtain the gel temperature of the resin matrix of the used prepreg as 110°C, the curing temperature as 120°C, and the curing time as 20 min through a differential scanning calorimeter, and accordingly determine the molding temperature as 120°C and the molding time as 20 min. Based on the molding temperature of 120°C and the temperature-pressure coupling relationship obtained in step SI, the molding pressure is 5 MPa. Therefore, all the process parameters for near-net molding by molding are determined.

[0071] SVI. Heat the mold to 110°C, then place the prepregs laid in a stepped shape obtained in step (SIV) in the mold and make the distance from the largest size layer (i.e., the bottom layer) to each edge of the mold consistent. Place temperature sensors and pressure sensors on each surface and the center position of the prepreg, as Figure 4 shown.

[0072] SVII. Heat the mold and apply pressure simultaneously. The clamping pressure is 0.15 MPa. Dynamically adjust the pressure by real-time monitoring of the pressure data. When the temperature distribution of the prepreg front is uniform and resin overflows at the mold edge, first slowly reduce the pressure to 4.6 MPa, and then slowly increase the pressure to the molding pressure of 5 MPa. Clamp the mold with the aid of an automated control system.

[0073] SVIII. Molding is carried out for 20 min at a molding pressure of 5 MPa and a molding temperature of 120 °C. At the same time, use the set temperature sensors to monitor each surface and the center of the prepreg in real time, record the temperature change curve over time, and adjust the temperature in a timely manner through the equipment system to control the temperature difference between the center and each surface not exceeding 3 °C, as Figure 5 shown. In addition, Figure 5 it further shows the accuracy of the model.

[0074] SIX. After molding for 20 min at a molding pressure of 5 MPa and a molding temperature of 120 °C, demold and perform post-treatment, then a resin matrix composite part with the required accuracy is obtained.

[0075] The ultimate result of the defects in the parts produced by the molding process is the deterioration of the mechanical properties of the molded parts. Therefore, this application evaluates the quality of the parts based on the mechanical properties.

[0076] For the parts obtained in this example, the flexural strength is 474.62 MPa and the tensile strength is 269.05 MPa.

[0077] Example 2

[0078] Except that the molding temperature is 130 °C, the others are the same as in Example 1.

[0079] For the parts obtained in this example, the flexural strength is 566.81 MPa and the tensile strength is 279.61 MPa.

[0080] Comparative Example 1

[0081] Except that the molding time is 30 min, the others are the same as in Example 1.

[0082] For the parts obtained in this comparative example, the flexural strength is 433.04 MPa and the tensile strength is 197.94 MPa.

[0083] Comparative Example 2

[0084] Same as Example 1, except that the prepreg is not laid in a stepped manner, but is laid in a staggered laying manner as Figure 6 shown.

[0085] For the parts obtained in this comparative example, the flexural strength is 415.14 MPa and the tensile strength is 167.46 MPa.

[0086] Comparative Example 3

[0087] Same as Example 1 except that the molding pressure is 10 MPa.

[0088] For the component obtained in this comparative example, its flexural strength is 522.39 MPa and its tensile strength is 202.55 MPa.

[0089] It can be seen from the comparison between the examples and the comparative examples that during the molding process of the chopped fiber prepreg, the process parameters have significant effects on the various properties of the manufactured components. Inappropriate molding pressure will cause resin accumulation or loss, inappropriate molding temperature will cause uneven curing of the prepreg, and inappropriate molding time will cause insufficient or over-curing of the prepreg. From the above examples and comparative examples, it can be seen that the near-net molding manufacturing process of the chopped fiber prepreg for high-quality components of the resin matrix composite material of the present invention effectively improves the mechanical properties of the manufactured components because it improves the quality of the manufactured components.

[0090] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Although the foregoing embodiments have been described in detail, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A near-net-shape molding manufacturing process for high-quality resin-based composite parts made of chopped fiber prepreg, characterized by: The following steps are involved: S1. Establish a part model, use the reaction compression molding module in the plastic molding simulation software to couple the temperature and pressure in the compression molding process and obtain the coupling relationship, and obtain the optimal mold window through the front temperature distribution of the chopped fiber prepreg under different mold clamping pressures and combined with the curing reaction rate; S2. manufacturing a cavity-core mold according to the workpiece, wherein the cavity volume of the mold is calculated based on a volume compensation formula; The volume compensation formula is: ; in: V m is the cavity volume of the mold, V p is the volume of the workpiece, S v is the volume curing shrinkage of the matrix resin of the chopped fiber prepreg; S3. According to The amount of chopped fiber prepreg is obtained; wherein: V m is the cavity volume of the mold, is the density of the chopped fiber prepreg, Ke is the loss coefficient, usually 1.02~1.10; S4. Cut the chopped fiber prepreg in a determined amount according to the size of the mold cavity, and make the size of the chopped fiber prepreg corresponding to the largest cross-section of the workpiece 60-80% of the size of the corresponding mold cavity, and the size of the chopped fiber prepreg corresponding to other parts of the workpiece is gradually reduced; the cut chopped fiber prepreg is laid in a stepped shape to facilitate the removal of gas during the molding process; S5, heating the mold to a temperature 10-20°C lower than the compression molding temperature, then placing the chopped fiber prepreg laid in a stepped shape obtained in step S4 in the mold, and placing a temperature sensor and a pressure sensor on each surface and the center of the chopped fiber prepreg; S6, heating the mold and applying the mold clamping pressure obtained in step S1 at the same time, monitoring the pressure data in real time and dynamically adjusting the pressure, when the temperature distribution along the front edge is uniform and resin overflows from the edge of the mold, first slowly releasing the pressure not exceeding 10% of the molding pressure, and then pressurizing to the molding pressure under the set mold clamping pressure, and realizing precise mold clamping with the help of an automated control system; the molding pressure is obtained based on the molding temperature in step S5 and the coupled relationship between temperature and pressure obtained in step S1; S7, molding at the molding pressure and molding temperature, and simultaneously using the placed temperature sensors and pressure sensors to monitor each surface and the center position of the chopped fiber prepreg in real time, recording the temperature change curve over time, and adjusting the temperature in time through the equipment system to control the temperature difference between the center and each surface to be no more than 3°C; and simultaneously monitoring the coupling relationship between pressure and temperature; S8, demoulding and post-processing after the molding time is up, so as to obtain a resin-based composite material product with the required precision.

2. The near-net-shape molding manufacturing process of high-quality resin-based composite parts made of chopped fiber prepreg according to claim 1 is characterized in that: The plastic molding simulation software is Autodesk Moldflow software.

3. The near-net-shape molding manufacturing process of high-quality resin-based composite parts made of chopped fiber prepreg according to claim 2 is characterized in that: Define the resin material in Autodesk Moldflow, select the curing reaction model and fiber length, set the temperature and pressure parameters, and predict the porosity of the molded part by simulating the temperature distribution under different mold clamping pressures and combining the curing reaction rate, thereby obtaining the optimal mold clamping window.

4. The process for manufacturing high-quality resin-based composite parts by chopped fiber prepreg molding near-net-shape molding according to claim 1, characterized in that: In step S1, the matrix of the chopped fiber prepreg is selected from any one of epoxy resin, phenolic resin, and unsaturated polyester resin, or a mixture of two or more thereof; the chopped fibers in the chopped fiber prepreg are selected from any one of chopped carbon fiber, chopped glass fiber, chopped aramid fiber, and chopped basalt fiber, or a mixture of two or more thereof.

5. The process for manufacturing high-quality resin-based composite parts by chopped fiber prepreg molding near-net-shape molding according to claim 1, characterized in that: In step S1, the gel temperature, curing temperature and curing time of the resin matrix of the chopped fiber prepreg are obtained by testing, and the curing temperature of the obtained resin matrix to the curing temperature + 20°C is used as the molding temperature, and the curing time is used as the molding time.

6. The near-net-shape molding manufacturing process of high-quality resin-based composite parts made of chopped fiber prepreg according to claim 5, characterized in that: The gel temperature, curing temperature and curing time of the resin matrix can be obtained by using a differential scanning calorimeter, a rheometer and a flat knife drawing method.

7. The near-net-shape molding manufacturing process of high-quality resin-based composite parts made of chopped fiber prepreg according to claim 1, characterized in that: In step S2, the mold is a steel mold, an aluminum alloy mold or a ceramic mold.

8. The process for manufacturing high-quality resin-based composite parts by chopped fiber prepreg molding near-net-shape molding according to claim 1, characterized in that: In step S2, the mold is provided with positioning pins to ensure the uniformity of the thickness of the workpiece; the mold is installed with a pressure sensor to monitor the pressure in the mold cavity in real time; the mold is installed with a displacement sensor to monitor the mold closing position and the resin extrusion amount in real time.

9. The near-net-shape molding manufacturing process of high-quality resin-based composite parts made of chopped fiber prepreg according to claim 1, characterized in that: In step S6, the mold clamping pressure is 0.1-0.5 MPa.

10. The near-net-shape molding manufacturing process of high-quality resin-based composite parts made of chopped fiber prepreg by molding according to claim 1, characterized in that: In step S5, the distances between the maximum dimension of the stepped chopped fiber prepreg placed in the mold and the edges of the corresponding mold cross section are consistent.

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