Intermediate material for forming fiber-reinforced resin-based composite material and preparation method of intermediate material

Abstract

The invention relates to the technical field of composite materials, in particular to an intermediate material for forming a fiber-reinforced resin-based composite material and a preparation method thereof.The intermediate material for forming the fiber-reinforced resin-based composite material comprises resin and unidirectional fibers, and the unidirectional fibers are fully covered with the resin; the unidirectional fiber comprises a plurality of fiber areas with different resin infiltration degrees. The preparation method comprises the following steps: transferring resin onto release paper by adopting a glue spreader to realize full-region or regional coating of the resin to obtain a resin glue film; respectively covering the upper surface and the lower surface of the unidirectional fiber with two layers of resin adhesive films, and fully or partially infiltrating resin in the resin adhesive films into the unidirectional fiber by adopting a hot-pressing roller with a convex surface, so as to control the infiltration degree of the resin. The intermediate material for forming the fiber-reinforced resin-based composite material and the preparation method aim at solving the problem that permeability and integrity of the intermediate material are difficult to consider at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to an intermediate material for molding fiber-reinforced resin-based composite materials and a preparation method thereof. Background Art

[0002] Advanced fiber-reinforced resin-based composites, boasting excellent properties such as high specific strength, high specific modulus, high-temperature resistance, corrosion resistance, and fatigue resistance, are widely used in the aerospace industry. Traditional processes typically use prepreg as an intermediate material and autoclave molding to produce high-quality composites. However, the high equipment and operating costs of autoclaves make them inadequate for the cost-effective manufacturing of large aerospace components.

[0003] Dry fiber using Vacuum Assisted Resin Infusion (VARI) and prepreg using Out-of-Autoclave / Vacuum Bagging (OoA or VBO) are two intermediate materials that can be formed without an autoclave. Both utilize vacuum bagging. Under negative pressure, air and volatiles are extracted from the intermediate material, allowing the resin to flow and infuse or fully saturate the fibers. The resin is then cured in an oven or curing furnace, reducing production costs.

[0004] However, autoclave molding can provide sufficiently large external pressure to crush bubbles, inhibit the formation of pores, promote resin flow, and fully impregnate the fibers; while vacuum bags can only provide a maximum pressure of one standard atmospheric pressure, so bubbles cannot be suppressed, the resin fluidity is lower, and defects such as pores are easily generated.

[0005] For dry fibers, existing technologies typically use dipping, spraying, or broadcasting to coat the fiber surface with a setting agent resin or penetrate it between fiber strands to achieve surface adhesion or cohesion. Thermoplastic fiber mesh is then composited onto the fiber surface to enhance toughness and improve the integrity of the dry fibers. To shorten injection time during liquid molding and reduce porosity caused by insufficient resin flow, it is often necessary to reduce the setting agent content in the dry fibers or to perforate or score the dry fibers to increase their Z-axis permeability.

[0006] VBO prepregs have strict requirements for their resin rheological properties: At room temperature, the resin viscosity should be high to facilitate air expulsion, while at elevated temperatures, the viscosity should be low to fully impregnate the fibers. Furthermore, during prepreg preparation, the degree of resin impregnation of the fibers must be controlled, leaving a portion of unimpregnated fibers as intra-layer airflow paths. Some VBO prepregs achieve interlayer airflow by coating the surface with an ultra-thin fabric, while others achieve Z-axis airflow by coating the fibers with a discontinuous resin film.

[0007] However, both dry fiber and VBO prepregs face a conflict between permeability and integrity. While reducing the setting agent content or the degree of resin impregnation of the fibers can improve the permeability of the intermediate material, facilitating gas expulsion and resin flow and infiltration during molding, this can reduce the cohesion and integrity of the intermediate material, hindering subsequent slitting or laying. Furthermore, drilling or scoring the intermediate material can damage or bend the fibers, affecting the mechanical properties of the composite material after molding.

[0008] Therefore, the inventors provide an intermediate material for molding a fiber-reinforced resin-based composite material and a preparation method thereof. Summary of the Invention

[0009] (1) Technical problems to be solved The embodiments of the present invention provide an intermediate material for molding fiber-reinforced resin-based composite materials and a preparation method thereof, which solve the technical problem that it is difficult to simultaneously take into account the integrity and permeability of the intermediate material.

[0010] (2) Technical solution A first aspect of the present invention provides an intermediate material for molding fiber-reinforced resin-based composite materials, comprising resin and unidirectional fibers, wherein the resin fully covers the unidirectional fibers, and the unidirectional fibers include multiple fiber regions with different resin impregnation degrees.

[0011] Furthermore, the unidirectional fiber is carbon fiber with a surface density of 50 to 600 g / m 2 .

[0012] Furthermore, the resin is a thermosetting resin, including at least one of epoxy resin, phenolic resin, vinyl ester resin, bismaleimide resin, cyanate resin, polyimide resin, benzoxazine resin and polyurethane resin.

[0013] Furthermore, when the intermediate material is dry fiber, the mass proportion of the resin is 0.5% to 15%.

[0014] Furthermore, when the intermediate material is a prepreg, the mass proportion of the resin is 30% to 45%.

[0015] The first aspect of the present invention also provides an intermediate material for molding fiber-reinforced resin-based composite materials, comprising resin and unidirectional fibers, wherein the resin does not fully cover the unidirectional fibers, and the unidirectional fibers include multiple fiber regions with different resin impregnation degrees.

[0016] A second aspect of the present invention provides a method for preparing an intermediate material for molding a fiber-reinforced resin-based composite material, comprising the following steps: The resin is transferred to the release paper using a coating roller to achieve full-area coating of the resin to obtain a resin film; Two layers of resin films are respectively covered on the upper and lower surfaces of the unidirectional fiber, and a convex hot pressing roller is used to fully or partially infiltrate the resin in the resin films into the unidirectional fiber to achieve control of the resin impregnation degree.

[0017] Furthermore, the viscosity of the resin at 60° C. is 20 to 2000 Pa.s; the viscosity of the resin at 80° C. is 5 to 200 Pa.s.

[0018] Furthermore, the gap between the hot pressing rollers is 0.1 to 0.4 mm.

[0019] A second aspect of the present invention further provides a method for preparing an intermediate material for molding a fiber-reinforced resin-based composite material, comprising the following steps: A convex coating roller is used to transfer the resin in a set pattern onto the release paper to achieve regional coating of the resin to obtain a resin film. Two layers of resin film are respectively covered on the upper and lower surfaces of the unidirectional fiber, and a hot pressing roller with a convex surface is used. The relative positions of the resin film and the hot pressing roller are adjusted so that the convex surface of the hot pressing roller surface is aligned with the area of ​​the film with resin, and the resin in the resin film is fully or partially infiltrated into the unidirectional fiber to achieve control of the degree of resin impregnation.

[0020] (3) Beneficial effects In summary, the present invention is suitable for low-cost processes that do not require autoclave molding, such as VARI and VBO processes, by fully or partially covering unidirectional fibers with resin to form an intermediate material. The unidirectional fibers include multiple fiber regions with different resin impregnation degrees, and the permeability and integrity of the intermediate material are balanced by controlling the fiber impregnation degree. The intermediate material can simultaneously meet the requirements of gas discharge, resin permeability, material integrity, and laying processability; it has high flexibility, low requirements for resin rheological properties, and can be used in a variety of resin systems; it can be prepared using existing film machines and prepreg machines, saving costs; it has high preparation efficiency and can be prepared in batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] Figure 1 This is a side view of the structure of an intermediate material for molding a fiber-reinforced resin-based composite material provided by an embodiment of the present invention; Figure 2This is a side view of the structure of another intermediate material for molding fiber-reinforced resin-based composite materials provided by an embodiment of the present invention; Figure 3 This is a schematic flow chart of a method for preparing an intermediate material for molding a fiber-reinforced resin-based composite material provided by an embodiment of the present invention; Figure 4 This is a schematic flow chart of another method for preparing an intermediate material for molding a fiber-reinforced resin-based composite material provided by an embodiment of the present invention; Figure 5 This is a top view of the structure of a fiber-reinforced resin-based composite material for molding provided in Example 1 of the present invention; Figure 6 This is a top view of the structure of a fiber-reinforced resin-based composite material for molding provided by Example 2 of the present invention; Figure 7 This is a top view of the structure for molding a fiber-reinforced resin-based composite material provided by Example 3 of the present invention.

[0023] In the picture: 1-resin; 2-unidirectional fiber. DETAILED DESCRIPTION

[0024] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments.

[0025] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0027] Figure 1 This is a schematic structural diagram of an intermediate material for molding a fiber-reinforced resin-based composite material provided by an embodiment of the present invention. Figure 1 The intermediate material may include resin 1 and unidirectional fibers 2, wherein the resin 1 completely covers the unidirectional fibers 2, and the unidirectional fibers include multiple fiber regions with different resin impregnation degrees.

[0028] Figure 2 This is a schematic structural diagram of an intermediate material for molding a fiber-reinforced resin-based composite material provided by an embodiment of the present invention. Figure 2 The intermediate material may include resin and unidirectional fibers, the resin does not fully cover the unidirectional fibers, and the unidirectional fibers include multiple fiber regions with different resin impregnation degrees.

[0029] In the above embodiment, the resin impregnation degree refers to the ratio of the thickness of the fiber impregnated area in the thickness direction of the intermediate material to the thickness of the intermediate material. The cohesion and integrity of the intermediate material are ensured by controlling the area ratio of the high and low fiber impregnation degree areas. The unidirectional fiber is carbon fiber with an area density of 50 to 600 g / m 2 The surface density is selected for a specific application scenario and can be 50g / m 2 , 100g / m 2 , 200g / m 2 , 300g / m 2 , 400g / m 2 , 500g / m 2 and 600g / m 2 Any value of the above will not be described here.

[0030] As an optional embodiment, the resin is a thermosetting resin, including at least one of epoxy resin, phenolic resin, vinyl ester resin, bismaleimide resin, cyanate resin, polyimide resin, benzoxazine resin, and polyurethane resin. The resin is a resin system and further includes a toughening agent, a curing agent, and an additive.

[0031] In a specific application scenario, the intermediate material can be further compounded with a thin layer of fiber felt, a thin layer of fiber fabric or a thermoplastic mesh to play the role of interlayer air conduction, toughening or improving integrity. The thin layer of fiber felt or fabric is composed of one or more of glass fiber, carbon fiber, quartz fiber, aramid fiber, ultra-high molecular weight polyethylene fiber, and basalt fiber. Thermoplastic fiber mesh is usually manufactured by melt spinning, electrospinning, wet web forming and other processes. The resins used in thermoplastic fiber mesh include polyamide, polyetherimide, polysulfone, polyethersulfone, phenolphthalein type polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyaryletherketone, phenolphthalein type polyaryletherketone, polypropylene, polyethylene terephthalate, polyurethane, etc. The mesh resin can be a mixture or copolymer of the above resins. The surface density of the thin layer of fabric or thermoplastic mesh is 3 to 50 g / m 2 The surface density is selected for a specific application scenario and can be 3g / m 2 , 10g / m 2 , 20g / m 2 , 30g / m 2 , 40g / m 2 and 50g / m2 Any value of the above will not be described here.

[0032] As an optional embodiment, when the intermediate material is dry fiber, the resin mass percentage is 0.5% to 15%. This mass percentage is selected for a specific application scenario and can be any value such as 0.5%, 1%, 3%, 5%, 8%, 10%, 12%, and 15%. It is not detailed here.

[0033] As an optional embodiment, when the intermediate material is a prepreg, the resin mass percentage is 30% to 45%. This mass percentage is selected for a specific application scenario and can be any value such as 30%, 35%, 40%, or 45%, which is not detailed here.

[0034] Figure 3 This is a flow chart of a method for preparing an intermediate material for molding a fiber-reinforced resin-based composite material provided by an embodiment of the present invention. Figure 3 , the method may include the following steps: S301, using a coating roller to transfer the resin onto the release paper to achieve full area coating of the resin to obtain a resin film; S302, covering the upper and lower surfaces of the unidirectional fiber with two layers of resin film respectively, and using a convex hot pressing roller to fully or partially infiltrate the resin in the resin film into the unidirectional fiber to achieve control of the resin impregnation degree.

[0035] In the above-described embodiment, a conventional prepreg hot-melt two-step adhesive film coating method is used. When the unidirectional fibers are composited with the resin, the resin film completely covers the upper and lower surfaces of the unidirectional fibers. The surface density of the resin film is controlled by controlling the temperature, the gap between the adjustment roller and the adhesive coating roller, and the vehicle speed. Using one or more pairs of hot pressing rollers with convex surfaces, the resin fully penetrates in some areas due to the variation in the roller gap, while in other areas the resin only penetrates the fiber surface or partially, thereby enabling control over the degree of resin impregnation. The degree of resin impregnation of the unidirectional fibers is regulated by the temperature of the hot pressing rollers, the gap between the hot pressing rollers, and the vehicle speed. The higher the temperature of the hot pressing rollers, the lower the resin viscosity, the smaller the roller gap, and the lower the vehicle speed, the easier it is for the resin to impregnate the unidirectional fibers, and the higher the degree of impregnation of the unidirectional fibers. Conventional hot pressing rollers can be used to further press the resin into the unidirectional fibers as needed. Among them, the temperature of the resin film is determined by the rheological properties of the resin system. The viscosity of the resin at 60°C is 20~2000Pa.s, the viscosity of the resin at 80°C is 5~200Pa.s, and the gap between the hot pressing rollers is 0.1~0.4mm (the gap refers to the shortest distance between the convex surfaces of the upper and lower hot pressing rollers).

[0036] Figure 4is a flowchart of a preparation method of a kind of fiber reinforced resin matrix composite material forming intermediate material provided by the embodiment of the present application, see Figure 4 The method can include the following steps: S401, using a glue spreading roller with a convex surface, transfer resin showing a set pattern to release paper to achieve resin regional coating, and obtain resin adhesive film; S402, cover two layers of resin adhesive film on the upper and lower surfaces of unidirectional fiber respectively, and adjust the relative position of resin adhesive film and hot pressing roller using hot pressing roller with convex surface, align the convex surface of hot pressing roller surface with part of resin adhesive film area, and fully or partially infiltrate resin in resin adhesive film into unidirectional fiber to achieve control of resin infiltration degree.

[0037] In the above embodiment, when preparing resin adhesive film, a glue spreading roller with a convex surface on the surface is used to transfer resin showing a set pattern (which can be strip-shaped or net-shaped, but is not limited thereto, as long as resin adhesive film is discontinuous and not fully covers release paper) to release paper to achieve resin regional coating and form resin adhesive film. The surface density of resin adhesive film is controlled by controlling temperature, adjusting the gap between roller and glue spreading roller, and controlling vehicle speed. One or more pairs of hot pressing rollers with convex surfaces on the surface are used to align the convex surface of hot pressing roller surface with part of resin adhesive film area, that is, to ensure that only part of the area of resin can contact the convex surface, rather than all areas of resin contacting the convex surface, and at the same time, due to the change of roller gap, some areas of resin fully infiltrate, and some areas of resin only partially infiltrate, so that the control of resin infiltration degree is achieved. The infiltration degree of resin into unidirectional fiber is regulated by the temperature of hot pressing roller, the gap of hot pressing roller and vehicle speed. The higher the temperature of hot pressing, the lower the viscosity of resin, the smaller the gap between rollers, and the lower the vehicle speed, the easier the resin infiltrates into unidirectional fiber, and the higher the infiltration degree of unidirectional fiber. Ordinary hot pressing roller can be used to further press resin into unidirectional fiber according to needs. The temperature of resin adhesive film is determined by the rheological properties of resin system, the viscosity of resin at 60℃ is 20-2000 Pa.s, the viscosity of resin at 80℃ is 5-200 Pa.s, and the gap of hot pressing roller is 0.1-0.4 mm (the shortest distance between the convex surfaces of the upper and lower hot pressing rollers).

[0038] Example 1 Adhesive film machine coated epoxy resin adhesive film two rolls, and the surface density of each roll of adhesive film was 35 g / m 2 . The viscosity of resin at 60℃ was 460 Pa.s, and the viscosity of resin at 80℃ was 53 Pa.s. 12K T800 grade carbon fiber was used as reinforcing material, and the fiber surface density was 145 g / m 2A pair of hot pressing rollers with convex surfaces of equal spacing (3mm), equal size (3mm×3mm), and thickness of 0.10mm are used to infiltrate the resin into the spaces between the carbon fiber bundles through hot pressing. By adjusting the temperature and roller gap, the impregnation degree of some fibers is 80% and that of some fibers is 50% (the degree of impregnation of the resin into the unidirectional fibers is detailed in Figure 5 The darker the color, the higher the degree of resin impregnation). The composite temperature of the fiber and resin film is 80℃, the roller gap is 0.15mm, and the speed is 3mm / min. Then, at a hot pressing temperature of 60℃, the composite surface density on the prepreg surface is 10g / m 2 A thin glass fiber fabric is used to further improve air conduction.

[0039] Example 2 The film machine coats two rolls of epoxy resin mesh film, each roll has a surface density of 33g / m 2 The resin has a viscosity of 125 Pa.s at 60°C and 23 Pa.s at 80°C. The horizontal (along the width of the film) and vertical (perpendicular to the width of the film) strips that make up the grid-like film are both 3mm wide and spaced 3mm apart. 12K T800 grade carbon fiber is used as the reinforcement material, with a fiber surface density of 133g / m 2 Align the upper and lower layers of film so that the grid positions overlap. Use a pair of hot pressing rollers with equally spaced (3mm) and equally wide strips (the strip width is 3mm, along the roller length and perpendicular to the fiber direction) and a 0.15mm thick convex surface. Adjust the relative position of the film and the hot pressing roller so that the convex surface of the hot pressing roller surface and the transverse film strips are aligned, and the film resin is infiltrated into the spaces between the carbon fiber bundles. By adjusting the temperature and roller gap, the impregnation degree of some fibers in contact with the grid film is 95%, and the impregnation degree of some fibers is 60% (see the impregnation degree of resin and unidirectional fibers for details). Figure 6 The darker the color, the higher the degree of resin impregnation). The composite temperature of the fiber and resin film was 75°C, the roller gap was 0.15 mm, and the speed was 3 mm / min.

[0040] Example 3 The film machine coats two rolls of epoxy resin mesh film, with a surface density of 8g / m 2 The viscosity of the resin is 125 Pa.s at 60°C and 23 Pa.s at 80°C. The width of the horizontal (along the width of the film) and vertical (perpendicular to the width of the film) strips that make up the grid-like film are both 3mm, with a spacing of 3mm. 12K T800 grade carbon fiber is used as the reinforcement material, with a fiber surface density of 200g / m 2; the upper and lower layers of the film are aligned, and the grid positions are overlapped. A pair of hot pressing rollers with equal intervals (3 mm), equal width strips (strip width 3 mm, direction along the length of the roller, perpendicular to the fiber direction), and a thickness of 0.1 mm convex surface are used. The relative position of the film and the hot pressing roller is adjusted, the convex surface of the hot pressing roller surface and the transverse film strip are aligned, and the resin of the film is penetrated between the carbon fiber tows. By adjusting the temperature and the roller gap, the fiber contact with the grid film is 70%, and the partial fiber is 40% (the degree of resin and unidirectional fiber infiltration is shown in Figure 7 , the darker the color represents the higher the degree of resin infiltration). The composite temperature of the fiber and the resin film is 90℃, the roller gap is 0.1mm, and the speed is 1mm / min. Then, at a hot pressing temperature of 90℃, one side surface is compounded with a polyamide mesh with a surface density of 8g / m 2 to obtain dry fibers.

[0041] It should be clear that each embodiment in the specification is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other, and each embodiment focuses on the difference from other embodiments. The present application is not limited to the specific steps and structures described above and shown in the drawings. Moreover, for the sake of brevity, detailed descriptions of known methods and techniques are omitted.

[0042] The above is only an embodiment of the present application, and is not limited to the present application. The present application can have various modifications and changes for those skilled in the art without departing from the scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the scope of the claims of the present application.

Claims

1. An intermediate material for molding fiber-reinforced resin-based composite materials, characterized in that: The invention comprises resin and unidirectional fibers, wherein the resin completely covers the unidirectional fibers, and the unidirectional fibers include a plurality of fiber regions with different resin impregnation degrees.

2. The intermediate material for molding fiber-reinforced resin-based composite materials according to claim 1, characterized in that: The unidirectional fiber is carbon fiber with a surface density of 50 to 600 g / m 2 .

3. The intermediate material for molding fiber-reinforced resin-based composite materials according to claim 1, characterized in that: The resin is a thermosetting resin, including at least one of epoxy resin, phenolic resin, vinyl ester resin, bismaleimide resin, cyanate resin, polyimide resin, benzoxazine resin and polyurethane resin.

4. The intermediate material for molding fiber-reinforced resin-based composite materials according to claim 1, characterized in that: When the intermediate material is dry fiber, the mass proportion of the resin is 0.5% to 15%.

5. The intermediate material for molding fiber-reinforced resin-based composite materials according to claim 1, characterized in that: When the intermediate material is a prepreg, the mass proportion of the resin is 30% to 45%.

6. An intermediate material for molding fiber-reinforced resin-based composite materials, characterized in that: The invention comprises resin and unidirectional fibers, wherein the resin does not completely cover the unidirectional fibers, and the unidirectional fibers include a plurality of fiber regions with different resin impregnation degrees.

7. A method for preparing an intermediate material for molding a fiber-reinforced resin-based composite material according to claim 1, characterized in that: The method comprises the following steps: The resin is transferred to the release paper using a coating roller to achieve full-area coating of the resin to obtain a resin film; Two layers of resin films are respectively covered on the upper and lower surfaces of the unidirectional fiber, and a hot pressing roller with a convex surface is used to fully or partially infiltrate the resin in the resin films into the unidirectional fiber to achieve control of the resin impregnation degree.

8. The method for preparing an intermediate material for molding a fiber-reinforced resin-based composite material according to claim 7, characterized in that: The viscosity of the resin at 60° C. is 20 to 2000 Pa.s; the viscosity of the resin at 80° C. is 5 to 200 Pa.s.

9. The method for preparing an intermediate material for molding a fiber-reinforced resin-based composite material according to claim 7, characterized in that: The gap between the hot pressing rollers is 0.1 to 0.4 mm.

10. A method for preparing an intermediate material for molding a fiber-reinforced resin-based composite material according to claim 6, characterized in that: The method comprises the following steps: A convex coating roller is used to transfer the resin in a set pattern onto the release paper to achieve regional coating of the resin to obtain a resin film. Two layers of resin film are respectively covered on the upper and lower surfaces of the unidirectional fiber, and a hot pressing roller with a convex surface is used. The relative positions of the resin film and the hot pressing roller are adjusted so that the convex surface of the hot pressing roller surface is aligned with the area of ​​the film with resin, and the resin in the resin film is fully or partially infiltrated into the unidirectional fiber to achieve control of the degree of resin impregnation.

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