A high-precision processing technology for prepreg preform and products made therefrom

Abstract

The present invention discloses a high-precision processing technology for prepreg preforms and the products made thereof, and belongs to the field of composite material preparation. The high-precision processing technology for prepreg preforms of the present invention comprises the following steps: S1, using fiber and resin to process and make prepreg; S2, using a layering method to make a preform; S3, pre-compacting the preform once according to the resin characteristics of the prepreg, and compacting it to the thickness of the finished product; S4, freezing the preform pre-compacted in step S3 to below the resin brittle temperature Tb; S5, in a temperature environment maintaining below the resin brittle temperature Tb, using machining to process the structural features in the thickness direction of the preform; S6, placing the processed preform in a curing molding mold and heating and curing. The present invention utilizes a combination of preform compaction, freezing and machining processes, so that the preform can be shaped by machining, and can form a fine structure in the thickness direction of the product, and obtain a prepreg preform with high dimensional accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material preparation, and more specifically to a high-precision processing technology for a prepreg preform and a product made therefrom. Background Art

[0002] With the rapid development of the aerospace field and the increasing requirements of the international situation on my country's independent research and development technology level, the design and development of the overall performance of parts, preparation technology and production equipment have attracted much attention. At present, among the many prepreg molding processes, compression molding has high production efficiency, is suitable for mass production, has precise product size, smooth surface, can have two refined surfaces, most of the complex structure products can be molded at one time, no auxiliary processing that damages the performance of the product is required, and the appearance and size of the product have good repeatability.

[0003] The existing prepreg molding process generally includes prepreg preparation, preform preparation and molding heating and curing molding. For example, the "a fiber-reinforced resin product and its molding method" disclosed in Chinese patent number ZL201710060715.X increases the flexibility of the molding process of the fiber-reinforced resin product by increasing the use of the preforming mold, and realizes the large-scale and complex product structure; the first fiber material layer can be laid on both sides of the fiber-reinforced resin product, thereby effectively improving the strength of the fiber-reinforced resin product, reducing the surface defects of the fiber-reinforced resin product, and obtaining a fiber-reinforced resin product with good surface gloss. Another example is a "resin supply material, preform, and fiber-reinforced resin manufacturing method" disclosed in Chinese patent application number 202010919422.4. Its fiber-reinforced resin manufacturing method is a fiber-reinforced resin manufacturing method that is formed by heating and pressurizing the preform, and thermosetting resin or resin is supplied from the resin supply material to the substrate.

[0004] The traditional prepreg molding process can usually only meet the dimensional accuracy requirements of small-thickness shell products. For products with large thickness (>8mm) and fine structural features in the thickness direction, it is impossible to accurately guarantee the dimensional accuracy and meet the laying requirements of fine structural features. Especially for large-thickness components with fine structures, the stacking method will cause a large amount of fiber buckling during the pressing process of the fine structure, thereby affecting the mechanical properties of the final product. The "method and device for providing a tapered edge on a plate including fiber material" disclosed in Chinese patent number ZL201380043543.5, in order to provide a tapered edge on the product, the impregnated fiber material is frozen in a solid state when it is machined by a machining device, so that a part of the edge can be machined to create a tapered surface. The purpose of creating the tapered surface is to prevent the laminate layer from delamination or cracking, and the overall machining accuracy requirement is not high. The aforementioned patent application 201710060715.X and patent application 202010919422.4 also mentioned freezing treatment of the preform. The purpose of the former is to facilitate the fixation and preservation of the preform, and the purpose of the latter is to facilitate the cutting of the preform, so as to facilitate the observation of the cross-section and the calculation of the mass content of the resin.

[0005] In summary, the existing prepreg molding process is difficult to produce products with large thickness and fine structural features in the thickness direction, and it is difficult to ensure the dimensional accuracy of the products and the placement requirements of fine structural features. Summary of the invention

[0006] 1. Technical problem to be solved by the invention

[0007] The present invention aims to provide a high-precision processing technology for prepreg preforms and the products made therefrom, so as to solve the problems that the existing prepreg molding process is difficult to produce products with large thickness and fine structural features in the thickness direction, and it is difficult to ensure the dimensional accuracy of the products and the laying requirements of the fine structural features. The technical scheme of the present invention is adopted to improve the existing prepreg molding process, and utilize the process combination of preform compaction, freezing and machining to enable the preform to be shaped by machining, and the fine structure in the thickness direction of the product can be formed to obtain a prepreg preform with high dimensional accuracy. In addition, the fine structural features of the resin-based composite product in the thickness direction can be highly fitted with the curing mold, and the mechanical properties of the product are guaranteed.

[0008] 2. Technical solution

[0009] In order to achieve the above object, the technical solution provided by the present invention is:

[0010] A high-precision processing technology for a prepreg preform of the present invention comprises the following steps:

[0011] S1. Preparing prepreg: using fiber and resin to process prepreg;

[0012] S2. Preparing a preform: Preparing a preform by layering;

[0013] S3, compaction treatment: pre-compact the preform once according to the resin characteristics of the prepreg, and compact it to the thickness of the finished product;

[0014] S4, freezing treatment: freezing the preform pre-compacted in step S3 to below the resin embrittlement temperature Tb;

[0015] S5, machining: in an environment where the temperature is maintained below the resin embrittlement temperature Tb, the structural features in the thickness direction of the preform are machined by machining;

[0016] S6. Heating and curing: placing the processed preform into a curing molding mold and heating and curing it.

[0017] Furthermore, in step S1, the fiber is selected from carbon fiber, glass fiber, basalt fiber and aramid fiber; the resin is selected from thermosetting resin and thermoplastic resin, and the resin content is 29% to 50%.

[0018] Furthermore, in step S2, the plying method of the preform is designed according to the required mechanical properties of the component.

[0019] Furthermore, in step S3, the compaction pressure is 1-15 MPa, and the pressure is maintained for 20-40 minutes.

[0020] Furthermore, in step S4, the preform is frozen by using liquid nitrogen, dry ice or a refrigerator, and the freezing temperature is determined according to the brittle temperature Tb of the selected resin.

[0021] Furthermore, in step S5, the machining is cutting to remove material.

[0022] Furthermore, in step S6, the cavity of the curing molding mold is consistent with the shape of the preform after machining.

[0023] Furthermore, in step S6, the curing heating temperature is set according to the curing characteristics of the selected resin, the curing pressure is 1-15 MPa, the temperature is 90-400° C., and the pressure is maintained for 30-60 minutes.

[0024] The present invention discloses a prepreg preform product, which is manufactured by adopting the above-mentioned high-precision processing technology for prepreg preforms.

[0025] 3. Beneficial effects

[0026] Compared with the existing known technologies, the technical solution provided by the present invention has the following significant effects:

[0027] (1) A high-precision processing technology for a prepreg preform and a product made therefrom of the present invention adopts a low-temperature processing preform technology to obtain a prepreg preform with high dimensional accuracy, the accuracy of which depends on the processing method and processing equipment; and the fibers in the preform can be kept straight and in a taut state, thereby ensuring the mechanical properties of the final resin-based composite product; furthermore, the fine features in the thickness direction of the product can be highly fitted to the curing molding mold, and the fibers will not bend during the pressing process, thereby ultimately ensuring the high-precision structural characteristics and mechanical properties of the resin-based composite product;

[0028] (2) The high-precision processing technology for prepreg preforms and the products made therefrom of the present invention improve the existing prepreg molding process and utilize a process combination of preform compaction, freezing and machining. Preform compaction can facilitate the shaping of the product structure, freezing can make the preform become solid, and machining can process the shape and size of the preform to be consistent with the finished product. No additional trimming is required at a later stage, so that the shape of the preform after machining is consistent with the cavity of the curing molding mold, with a higher degree of fit, and the mechanical properties of the product are guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A process flow chart of a high-precision processing technology for a prepreg preform of the present invention;

[0030] Figure 2 This is a part diagram of a 1 / 4 half-pipe joint molded by the high-precision processing technology of the prepreg preform of the present invention.

[0031] Explanation of the symbols in the schematic diagram:

[0032] 1. Prepreg; 2. Pre-compacting device; 3. Freezing device; 4. Machining device; 5. Curing and molding device; 11. Thread; 12. Back-cut groove; 13. Step hole. DETAILED DESCRIPTION

[0033] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings.

[0034] Combination Figure 1 As shown, a high-precision processing technology for a prepreg preform of the present invention comprises the following steps:

[0035] S1. Preparation of prepreg: prepreg is made by processing fiber and resin. Resin is used as the matrix and fiber is used as the reinforcement. Prepreg can be made by impregnating continuous fiber fabric with resin. Fiber can be selected from carbon fiber, glass fiber, basalt fiber and aramid fiber, etc., and can be selected according to the mechanical properties of the product. Resin preferably uses thermosetting resin and thermoplastic resin, and the content of resin in prepreg can be designed to be 29% to 50%, and the specific content of resin can be determined according to the performance requirements of the product.

[0036] S2. Preparing a preform: The preform is prepared by a layering method. Specifically, the preform can be prepared by an initial layering method of conventional lamination. The layering method of the preform is designed according to the mechanical properties required by the component, such as unidirectional layering or multidirectional layering.

[0037] S3. Compacting treatment: Pre-compact the preform once according to the resin characteristics of the prepreg, and compact it to the thickness of the finished product. The preform after pre-compacting can be more convenient to shape, and the compacting pressure can be controlled at 1-15MPa, and the pressure can be maintained for 20-40min, making the preform more compact as a whole and improving the structural strength of the preform. Compacting the preform directly to the thickness of the finished product facilitates subsequent molding and curing, and can reduce fiber buckling during molding and curing, which is beneficial to improving product performance.

[0038] S4, freezing treatment: Freeze the preform after pre-compacting in step S3 to below the resin brittle temperature Tb. The refrigeration method can use cold sources such as liquid nitrogen and dry ice, or refrigerators such as compressors and evaporators. By freezing the preform, the preform is made to be below the resin brittle temperature Tb, and the preform becomes solid. At this time, the prepreg does not undergo chemical reaction, which is a physical change, providing conditions for subsequent processing of structural features in the thickness direction of the preform. The freezing temperature is determined according to the brittle temperature Tb of the selected resin.

[0039] S5. Machining: In a temperature environment that is maintained below the resin embrittlement temperature Tb, the structural features in the thickness direction of the preform are machined by machining. Machining is a cutting process to remove materials, such as commonly used turning, milling, planing, grinding, drilling and boring, etc., which can be selected according to the structural characteristics of the component. The ambient temperature of the entire machining process is below the resin embrittlement temperature Tb, ensuring that the structural features in the thickness direction of the preform are machined in a solid state.

[0040] S6. Heating and curing: Place the processed preform into the curing molding die for heating and curing. The curing heating temperature can be set according to the curing characteristics of the selected resin, the curing pressure can be designed to be 1-15MPa, the temperature is 90-400℃, and the pressure is maintained for 30-60min. The specific prepreg molding parameters can be determined according to design requirements. The cavity of the curing molding die is consistent with the shape of the machined preform, so that the preform and the curing molding die are highly fitted, and the fibers will not bend during the pressing process, ultimately ensuring the high-precision structural characteristics and mechanical properties of the resin-based composite products.

[0041] The prepreg preform product manufactured by the above-mentioned high-precision processing technology for prepreg preforms can obtain high-precision structural characteristics and mechanical properties, and can produce products with large thickness and fine structural characteristics in the thickness direction, ensuring the product size accuracy and the laying requirements of fine structural characteristics.

[0042] The present invention will be further described below in conjunction with the embodiments.

[0043] [Example]

[0044] This embodiment is made by Figure 2 Taking the pipe fitting product shown as an example, the structural feature of the pipe fitting product is that it has a thread 11 and a back cutter groove 12 on its outer wall, and a stepped hole 13 on its inner wall, that is, there are threads 11, back cutter groove 12 and stepped hole 13 in the thickness direction of the product. It is difficult to form the above-mentioned fine structural features with the existing prepreg molding process.

[0045] See also Figure 1 As shown, a high-precision processing technology for a prepreg preform of this embodiment comprises the following steps:

[0046] S1. Preparing prepreg: The prepreg 1 is a thermosetting carbon fiber unidirectional prepreg, the thickness of the prepreg 1 is 0.1 mm, the carbon fiber is T700S, the resin is a thermosetting epoxy resin, and the resin content is 42%.

[0047] S2. Preparing a preform: After the prepreg is cut into a designed shape, it is laid in a tooling; specifically, the laying is performed by a continuous covering laying method, and woven prepreg can also be laid on both sides of the upper and lower surfaces as needed.

[0048] S3, compaction treatment: the preform is pre-compacted according to the resin characteristics of the prepreg. The pre-compacting step can use a pre-compacting device 2, which can be a molding device. The pre-compacting pressure is 2MPa, compacted to the thickness of the finished product, and the pressure is maintained for 30 minutes.

[0049] S4, freezing treatment: using a freezing device 3 such as liquid nitrogen, dry ice, a compressor and an evaporator to freeze the preform to a temperature below the resin embrittlement temperature Tb, specifically -30°C.

[0050] S5, machining: in an environment where the temperature is maintained below the resin embrittlement temperature, the machining device 4 is used to machine the threads 11, the undercut grooves 12, the stepped holes 13 and other features in the thickness direction of the preform.

[0051] S6, heating and curing: placing the processed preform into the curing and molding device 5 for heating and curing. The curing and molding device 5 may be a molding device. The pressure of the pressurized curing is 4 MPa, the temperature is 150° C., and the pressure is maintained for 60 minutes.

[0052] The above-mentioned prepreg preform is produced by high-precision processing technology Figure 2 The pipe fitting product shown has high-precision structural features and good mechanical properties.

[0053] The high-precision processing technology of a prepreg preform of the present invention is particularly suitable for preforms with large thickness (>8mm) and fine structural features in the thickness direction. By improving the existing prepreg molding process, a process combination of preform compaction, freezing and machining is used. The compaction of the preform can facilitate the shaping of the product structure, freezing can make the preform become solid, and machining can process the shape and size of the preform to be consistent with the finished product. No additional trimming is required in the later stage, so that the shape of the preform after machining is consistent with the cavity of the curing molding mold, with a higher degree of fit, and the mechanical properties of the product are guaranteed.

[0054] Compared with the prior art, the present invention also has the following advantages:

[0055] Firstly, the present invention adopts low temperature processing preform technology to obtain a prepreg preform with high dimensional accuracy, and its accuracy depends on the processing method and processing equipment.

[0056] Secondly, the present invention can keep the fibers in the preform straight and in a taut state, thereby ensuring the mechanical properties of the final resin-based composite product.

[0057] Thirdly, the present invention can achieve a high degree of fit between the fine features in the thickness direction and the mold, and the fibers will not bend during the pressing process, ultimately ensuring the high-precision structural characteristics and mechanical properties of the resin-based composite products.

[0058] The present invention and its embodiments are described schematically above, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and creatively designs a structure and an embodiment similar to the technical solution without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A high-precision processing technology for prepreg preforms, It is characterized in that The following steps are involved: S1. Preparing prepreg: Prepreg is made by processing fiber and resin, and the content of resin in the prepreg is 29%~50%; S2. Preparing a preform: Preparing a preform by layering; S3, compaction treatment: pre-compact the preform once according to the resin characteristics of the prepreg, and compact it to the thickness of the finished product; the compaction pressure is 1~15MPa, and the pressure is maintained for 20~40min; S4, freezing treatment: freezing the preform pre-compacted in step S3 to below the resin embrittlement temperature Tb; S5, machining: in an environment where the temperature is maintained below the resin embrittlement temperature Tb, the structural features in the thickness direction of the preform are machined by machining; S6, heating and curing: placing the processed preform into a curing and molding mold and heating and curing; the cavity of the curing and molding mold is consistent with the shape of the machined preform; The curing heating temperature is set according to the curing characteristics of the selected resin, the curing pressure is 1~15MPa, the temperature is 90~400℃, and the pressure is maintained for 30~60min.

2. The high-precision processing technology for prepreg preform according to claim 1, Features: In step S1, the fiber is selected from carbon fiber, glass fiber, basalt fiber and aramid fiber; and the resin is selected from thermosetting resin and thermoplastic resin.

3. The high-precision processing technology for prepreg preform according to claim 1, Features: In step S2, the layup method of the prefabricated body is designed according to the required mechanical properties of the component.

4. The high-precision processing technology for prepreg preform according to claim 1, Features: In step S4, the preform is frozen by using liquid nitrogen, dry ice or a refrigerator, and the freezing temperature is determined according to the brittle temperature Tb of the selected resin.

5. The high-precision processing technology for prepreg preform according to claim 1, Features: In step S5, the machining is cutting to remove material.

6. A prepreg preform product, Features: The prepreg preform product is manufactured by using the high-precision processing technology for prepreg preforms according to any one of claims 1 to 5.

Images