Molding control method for in-plane wrinkles of composite material

Abstract

The invention discloses a forming control method for in-plane wrinkles of a composite material, which comprises the following steps of: firstly, ensuring that carbon fiber prepregs on two sides are straight and stable under the pressure limitation of shaping clamping plate pressure devices on two sides, and then controlling the softening and shaping of resin of the carbon fiber prepregs by utilizing the temperature of a hot air gun; then, the carbon fiber prepreg fiber filaments are driven to be bent through self heat transfer and friction force of the metal rod; according to the forming control method, carbon fiber prepreg fiber yarn buckling size control is achieved through diameter control and dragging force of a metal rod, and finally in-plane fiber wrinkles are compacted and shaped after the temperature is cooled. According to the mode, in-plane fiber wrinkles with the height as small as 0.5 mm can be manufactured in a controlled mode, certain forming stability is achieved, the in-plane fiber wrinkles are provided for a detection mechanism to conduct in-plane wrinkle detection testing and mechanical testing, precious data support can be provided for design and research and development of composite materials through accurate detection and analysis of the in-plane wrinkles, and the in-plane fiber wrinkles can be obtained. The material formula is optimized, the manufacturing process is improved, and the product performance is improved.

Description

Technical Field

[0001] The invention relates to the technical field of composite material in-plane wrinkle forming, and in particular to a composite material in-plane wrinkle forming control method. Background Art

[0002] Due to factors such as large differences in the linear expansion coefficients of composite materials, improper selection of parameters such as ply angle and ply thickness, and internal stress caused by uneven resin curing, the in-plane fibers of composite materials undergo deformation mechanisms such as bending, slipping, and in-plane shear. These mechanisms act on the material together and may lead to the formation of in-plane wrinkles.

[0003] In-plane wrinkles will cause stress concentration when the material is subjected to stress, significantly reducing the mechanical properties of the composite material, such as tensile strength, compressive strength, and fatigue life, thereby accelerating the destruction of the material. At the same time, wrinkle defects will significantly change the failure mode of the composite material. Composite materials originally designed to be unidirectionally fiber-reinforced may exhibit burst failure under longitudinal tensile loads, but the presence of wrinkle defects may change their failure mode to fiber breakage failure and slight burst failure.

[0004] In the aerospace, automotive and other industries, potential in-plane wrinkles in composite structural parts may cause serious damage to personnel and equipment. Therefore, accurate in-plane wrinkle detection is an important means to avoid these potential losses. Accurate detection and analysis of in-plane wrinkles can timely discover and repair potential structural problems and ensure the safety of composite structures. Summary of the invention

[0005] In view of the problems that the causes of in-plane wrinkles in the above-mentioned composite materials are complex, difficult to control molding and have a significant impact on the mechanical properties of composite structural parts, the present invention provides a molding control method for in-plane wrinkles in composite materials under high temperature and high pressure, which provides conditions for subsequent in-plane wrinkle molding and detection.

[0006] In order to solve the above technical problems, the present invention provides a forming control method for in-plane wrinkles of a composite material. First, the carbon fiber prepregs on both sides are ensured to be straight and stable under the pressure limit of the pressure devices of the shaping pallets on both sides. Then, the temperature of the hot air gun is used to control the softening and shaping of the carbon fiber prepreg resin. Then, the self-heat transfer and friction of the metal rod are used to drive the fiber filaments of the carbon fiber prepreg to bend. The forming control method realizes the size control of the bending of the carbon fiber prepreg fiber filaments by controlling the diameter of the metal rod and the pulling force. Finally, the temperature is waited for cooling to compact and shape the in-plane fiber wrinkles.

[0007] The specific steps of the molding control method are as follows: Step A: placing the composite carbon fiber prepreg on a metal rod of a selected size, and placing the whole on a flat tooling with a flat surface and a certain rigidity; Step B: Then, a plastic scraper is used to adhere the carbon fiber prepreg to the bottom side of the metal rod and make an imprint mark to determine the subsequent in-plane fiber wrinkle width; Step C: After confirming that the carbon fiber prepreg has been firmly attached to the metal rod, a positioning clamping device is installed on both sides of the metal rod to prevent the carbon fiber wires on both sides from sliding over a large range during the subsequent dragging of the metal rod; Step D: Use a hot air gun to heat the carbon fiber prepreg placed on the metal rod from beginning to end in sequence at a medium temperature to ensure uniform heating until the carbon fiber prepreg resin softens, thereby reducing the sliding resistance of the carbon fiber filaments; Step E: further lower the temperature of the hot air gun, apply a pulling force F from the front end to pull the metal rod, and apply a thrust F1 from the rear end to push the metal rod forward; utilize the temperature of the metal rod, the viscosity of the carbon fiber prepreg, and the friction between the metal rod and the carbon fiber prepreg to drive the carbon fiber yarn to slide and deform; Step F: When it is confirmed that the 0-degree carbon fiber prepreg has been pulled out to the specified size, stop the heat preservation of the hot air gun, wait for the composite carbon fiber prepreg to cool naturally, and remove the curvature prepreg sheet from the metal rod after cooling; Step G: Apply a slight pulling force at both ends of the prepreg sheet with curvature in the 0 degree direction and gradually press the prepreg sheet during this process to compact the curvature area into a two-dimensional plane, so as to obtain two-dimensional in-plane fiber wrinkles of a specified size; Step H: Finally, a release layer is laid between the fiber folds in the two-dimensional plane and the metal forming tooling, and an isolation film, a breathable felt, and a vacuum bag are laid in sequence on the fiber folds in the two-dimensional plane for packaging, and the vacuum is drawn to -0.08MPa, the seal is maintained, and a seal leak test is performed; Step I: Send the packaged two-dimensional in-plane fiber folds and metal forming tooling into a hot autoclave for curing and molding, vacuumize to -0.08MPa, and heat for 120min~180min; demold after taking out of the can to obtain molded two-dimensional in-plane fiber folds.

[0008] Preferably, metal rods of different diameters are selected and different pulling forces are used to produce in-plane fiber wrinkles of different sizes.

[0009] Preferably, in step C, after the carbon fiber prepreg is adhered to the metal rod, the positioning clamp devices installed on both sides of the metal rod are adjusted according to the elastic slip level of the carbon fiber prepreg. If the positioning clamp device is too tight, it is easy to cause fiber tearing due to insufficient fiber tension. If the positioning clamp device is too loose, the fibers on both sides are easy to slide and gather, resulting in increased fiber wrinkles.

[0010] Preferably, when using a hot air gun, air is blown in one direction in sequence to avoid uneven heating of the carbon fiber prepreg placed on the metal rod, resulting in different sizes. At the same time, the carbon fiber prepreg restricted by the positioning card device on both sides is prevented from being blown.

[0011] Preferably, in step D, the heating temperature of the hot air gun is 90°, and the heating time varies according to the size of the carbon fiber prepreg.

[0012] Preferably, in step E, during pulling, the heating temperature of the hot air gun is 60°. If it is found that the pulling force of some areas of the carbon fiber prepreg is insufficient and the curvature is smaller than other areas during the pulling process, it should be stopped and manually adjusted to ensure uniform size distribution.

[0013] Preferably, in step F, the carbon fiber prepreg is cooled to the normal room temperature of the metal rod while the prepreg sheet maintains a certain resin viscosity, and then the prepreg sheet is removed from the metal rod. At this time, the height difference of the fiber wrinkles is flattened, and only the in-plane fiber curvature is retained.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a method for preparing in-plane wrinkles of different sizes. This method can control the manufacture of in-plane fiber wrinkles as small as 0.5 mm in height, and has a certain molding stability. It is provided to the detection agency for in-plane wrinkle detection and mechanical testing. Through the accurate detection and analysis of in-plane wrinkles, it can provide valuable data support for the design and development of composite materials, and help researchers to have a deeper understanding of the formation mechanism, influencing factors and specific effects on material properties of wrinkle defects, so as to optimize material formulation, improve manufacturing process and enhance product performance. 2. The molding control method of the present invention can effectively avoid problems such as uneven distribution of surface wrinkles, different wrinkle curvatures, and discontinuous gaps in wrinkle fibers during the wrinkle molding process; it can improve the accuracy of in-plane wrinkle detection and enhance the overall quality and reliability of products in the aerospace field. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a process flow chart of the in-plane fiber wrinkle control molding process provided by the present invention; Figure 2 is an isometric view of the in-plane fiber wrinkle clamping control provided by the present invention; Figure 3 is a side view of the in-plane fiber wrinkle clamping control provided by the present invention; Figure 4 This is a schematic diagram of the controlled forming of in-plane fiber wrinkles provided by the present invention; Figure 5 is a two-dimensional schematic diagram of in-plane fiber wrinkles provided by the present invention; Figure 6 It is a schematic diagram of the in-plane fiber pleat hot press molding provided by the present invention.

[0016] In the figure: 1. Metal rod; 2. Carbon fiber prepreg; 3. Positioning card device; 4. Flat tooling; 5. Hot air gun; 6. Isolation film; 7. Breathable felt; 8. Vacuum bag; 9. Release layer; 10. Metal forming tooling. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are in very simplified form and in non-precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0019] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0020] In addition, the features, operations, and characteristics described in the specification can be combined in any appropriate manner to form various embodiments. Similarly, the steps or actions described in the method can also be adjusted in order in a manner that can be easily seen by those skilled in the art. Therefore, the various sequences in the specification and drawings are only for the purpose of describing a certain embodiment, and are not necessarily such sequences, unless otherwise stated that a certain sequence must be followed. Example

[0021] The present invention provides a method for controlling the formation of in-plane wrinkles in a composite material. Figure 1First, the carbon fiber prepregs on both sides are kept straight and stable under the pressure limit of the shaping card pressure devices on both sides, and then the carbon fiber prepreg resin is softened and shaped by the temperature of the hot air gun, and then the self-heat transfer and friction of the metal rod are used to drive the carbon fiber prepreg fiber filaments to bend; the molding control method realizes the size control of the bending of the carbon fiber prepreg fiber filaments by controlling the diameter of the metal rod and the pulling force, and finally waits for the temperature to cool down to compact and shape the fiber wrinkles in the surface.

[0022] like Figure 2-6 , the specific steps of the molding control method are as follows: Step A: Figure 2-4 As shown, the composite carbon fiber prepreg 2 is placed on a metal rod 1 of a selected size, and the whole is placed on a flat tooling 4 with a flat surface and a certain rigidity; Step B: Then, a plastic scraper is used to make the carbon fiber prepreg 2 adhere to the bottom side of the metal rod 1 and make an imprint mark to determine the subsequent in-plane fiber wrinkle width; Step C: After confirming that the carbon fiber prepreg 2 has been firmly attached to the metal rod 1, a positioning clamp device 3 is installed on both sides of the metal rod 1 to prevent the carbon fiber filaments on both sides from sliding over a large range during the subsequent dragging of the metal rod 1; Step D: Use a hot air gun 5 to heat the carbon fiber prepreg 2 placed on the metal rod 1 at a medium temperature from beginning to end in sequence to ensure uniform heating until the resin of the carbon fiber prepreg 2 softens, so that the sliding resistance of the carbon fiber filaments is reduced; when heating, pay attention to the excess prepreg on both sides to prevent it from being deformed by heat; Step E: further lower the temperature of the hot air gun 5, apply a pulling force F from the front end to pull the metal rod 1, and apply a thrust F1 from the rear end to push the metal rod 1 forward; utilize the temperature of the metal rod 1 and the viscosity of the carbon fiber prepreg 2, and the friction between the metal rod 1 and the carbon fiber prepreg 2 to drive the carbon fiber yarn to slide and deform; in this step, it is necessary to continue to use the hot air gun at a medium or low temperature to ensure that the carbon fiber prepreg 2 is in a moderately softened state; Step F: When it is confirmed that the 0-degree carbon fiber prepreg 2 has been pulled out to a specified size, the heat gun 5 is stopped to keep warm, and the composite carbon fiber prepreg 2 is allowed to cool naturally. After cooling, the prepreg sheet with curvature is removed from the metal rod 1; Step G: Figure 5 As shown, a slight pulling force is applied to both ends of the prepreg sheet with curvature along the 0 degree direction and the prepreg sheet is gradually pressed during this process to compact the curvature area into a two-dimensional plane, so that two-dimensional in-plane fiber wrinkles of a specified size can be obtained; Step H: Figure 6As shown, finally, a release layer 9 is laid between the two-dimensional in-plane fiber folds and the metal forming tooling 10, and an isolation film 6, a breathable felt 7, and a vacuum bag 8 are laid in sequence on the two-dimensional in-plane fiber folds for packaging, and the vacuum is drawn to -0.08MPa to maintain sealing, and a sealing leak test is performed; Step I: Send the packaged two-dimensional in-plane fiber folds and the metal forming tooling 10 into a hot autoclave for curing and molding, vacuumize -0.08MPa, and hold the temperature for 120min~180min; demold after taking out of the can to obtain molded two-dimensional in-plane fiber folds.

[0023] Specifically, by selecting metal rods 1 of different diameters and using different pulling forces, in-plane fiber wrinkles of different sizes can be manufactured. Specifically, the relationship between pulling force and size function needs to be accumulated and verified based on actual operations.

[0024] Specifically, in step C, after the carbon fiber prepreg 2 is firmly attached to the metal rod 1, the installation positioning clamp devices 3 on both sides of the metal rod 1 are adjusted according to the elastic slip level of the carbon fiber prepreg 2. If the positioning clamp device 3 is restricted too tightly, it is easy to cause fiber tearing due to insufficient fiber tension. If the positioning clamp device 3 is restricted too loosely, the fibers on both sides are easy to slide and gather, resulting in increased fiber wrinkles.

[0025] Specifically, when using the hot air gun 5, air is blown in one direction in sequence to avoid uneven heating of the carbon fiber prepreg 2 placed on the metal rod 1, resulting in different sizes. At the same time, the carbon fiber prepreg 2 restricted by the positioning clamp device 3 on both sides is prevented from being blown.

[0026] Further, in step D, the heating temperature of the hot air gun 5 is 90°, and the heating time varies according to the size of the carbon fiber prepreg 2. The present invention provides a heating example of 100×200 mm heating and blowing time of 15-20 minutes.

[0027] Furthermore, in step E, when pulling, the heating temperature of the hot air gun 5 is 60°. If it is found that the pulling force of some areas of the carbon fiber prepreg 2 is insufficient and the curvature is smaller than other areas during the pulling process, it should be stopped and manually adjusted to ensure uniform size distribution.

[0028] Specifically, in step F, the carbon fiber prepreg 2 is cooled to the normal room temperature of the metal rod 1 while the prepreg sheet maintains a certain resin viscosity, and then the prepreg sheet is removed from the metal rod 1. At this time, the height difference of the fiber wrinkles is flattened, and only the in-plane fiber curvature is retained.

[0029] The method for preparing in-plane wrinkles of different sizes provided by the present invention can control the manufacture of in-plane fiber wrinkles as small as 0.5 mm in height, and has a certain molding stability, which can be provided to detection institutions for in-plane wrinkle detection tests and mechanical tests. Through accurate detection and analysis of in-plane wrinkles, valuable data support can be provided for the design and development of composite materials, which helps researchers to have a deeper understanding of the formation mechanism of wrinkle defects, influencing factors and the specific impact on material properties, thereby optimizing material formulations, improving manufacturing processes, and enhancing product performance.

[0030] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for controlling the formation of in-plane wrinkles in a composite material, characterized in that: First, the carbon fiber prepregs on both sides are kept straight and stable under the pressure limit of the shaping card pressure devices on both sides. Then, the carbon fiber prepreg resin is softened and shaped by using the temperature of a hot air gun. Then, the self-heat transfer and friction of the metal rod are used to drive the carbon fiber prepreg fiber filaments to bend. The molding control method realizes the size control of the bending of the carbon fiber prepreg fiber filaments by controlling the diameter of the metal rod and the pulling force. Finally, the temperature is cooled to compact and shape the fiber wrinkles in the surface.

2. A method for controlling the formation of in-plane wrinkles in a composite material according to claim 1, characterized in that: The specific steps of the molding control method are as follows: Step A: placing a composite carbon fiber prepreg (2) on a metal rod (1) of a selected size, and placing the entire rod on a flat plate tooling (4) with a flat surface and a certain rigidity; Step B: Then, a plastic scraper is used to make the carbon fiber prepreg (2) adhere to the bottom side of the metal rod (1) and make an imprint mark to determine the subsequent in-plane fiber wrinkle width; Step C: after confirming that the carbon fiber prepreg (2) has been firmly attached to the metal rod (1), a positioning clamping device (3) is installed on both sides of the metal rod (1) to prevent the carbon fiber filaments on both sides from sliding over a large range during the subsequent dragging of the metal rod (1); Step D: using a hot air gun (5) to heat the carbon fiber prepreg (2) placed on the metal rod (1) in sequence from the beginning to the end at a medium temperature, ensuring uniform heating, until the resin of the carbon fiber prepreg (2) softens, thereby reducing the sliding resistance of the carbon fiber filaments; Step E: further lowering the temperature of the hot air gun (5), applying a pulling force F from the front end to pull the metal rod (1), and applying a thrust F1 from the rear end to push the metal rod (1) forward; utilizing the temperature of the metal rod (1), the viscosity of the carbon fiber prepreg (2), and the friction between the metal rod (1) and the carbon fiber prepreg (2) to drive the carbon fiber filaments to slide and deform; Step F: When it is confirmed that the 0-degree carbon fiber prepreg (2) has been pulled out to a specified size, the heat gun (5) is stopped to keep warm, and the composite carbon fiber prepreg (2) is allowed to cool naturally. After cooling, the prepreg sheet with curvature is removed from the metal rod (1); Step G: Apply a slight pulling force at both ends of the prepreg sheet with curvature in the 0 degree direction and gradually press the prepreg sheet during this process to compact the curvature area into a two-dimensional plane, so as to obtain two-dimensional in-plane fiber wrinkles of a specified size; Step H: Finally, a release layer (9) is laid between the two-dimensional in-plane fiber folds and the metal forming tooling (10), and an isolation film (6), a breathable felt (7), and a vacuum bag (8) are laid in sequence on top of the two-dimensional in-plane fiber folds for packaging, and the vacuum is drawn to -0.08 MPa, the seal is maintained, and a seal leak test is performed; Step I: The packaged two-dimensional in-plane fiber folds and the metal forming tooling (10) are sent to a hot autoclave for curing and forming, and the vacuum is drawn to -0.08MPa and the temperature is 120min~180min; after being taken out of the autoclave and demoulding, the molded two-dimensional in-plane fiber folds can be obtained.

3. A method for controlling the formation of in-plane wrinkles in a composite material according to claim 1 or 2, characterized in that: By selecting metal rods (1) of different diameters and using different pulling forces, in-plane fiber wrinkles of different sizes and specifications are manufactured.

4. A method for controlling the formation of in-plane wrinkles in a composite material as claimed in claim 1 or 2, characterized in that: In step C, after the carbon fiber prepreg (2) is firmly attached to the metal rod (1), the positioning clamping devices (3) installed on both sides of the metal rod (1) are adjusted according to the elastic sliding level of the carbon fiber prepreg (2). If the positioning clamping device (3) is restricted too tightly, it is easy to cause fiber tearing due to insufficient fiber tension. If the positioning clamping device (3) is restricted too loosely, the fibers on both sides are easy to slide and aggregate, resulting in an increase in fiber wrinkles.

5. A method for controlling the formation of in-plane wrinkles in a composite material as claimed in claim 1 or 2, characterized in that: When using the hot air gun (5), the air is blown in one direction in sequence to avoid uneven heating of the carbon fiber prepreg (2) placed on the metal rod (1), which results in different sizes. At the same time, the carbon fiber prepreg (2) restricted by the positioning clamping plate device (3) on both sides is prevented from being blown.

6. A method for controlling the formation of in-plane wrinkles in a composite material as claimed in claim 5, characterized in that: In step D, the heating temperature of the hot air gun (5) is 90°, and the heating time varies according to the size of the carbon fiber prepreg (2).

7. A method for controlling the formation of in-plane wrinkles in a composite material as claimed in claim 5, characterized in that: In step E, during pulling, the heating temperature of the hot air gun (5) is 60°. If it is found during the pulling process that the pulling force of some areas of the carbon fiber prepreg (2) is insufficient and the curvature is smaller than that of other areas, the process should be stopped and manually adjusted to ensure uniform size distribution.

8. The method for controlling the formation of in-plane wrinkles in a composite material according to claim 1, characterized in that: In step F, the carbon fiber prepreg (2) is cooled to the normal room temperature of the metal rod (1) while the prepreg sheet maintains a certain resin viscosity, and then the prepreg sheet is removed from the metal rod (1). At this time, the height difference of the fiber wrinkles is flattened, and only the in-plane fiber curvature is retained.

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