A composite material reinforcing sheet curing device

Abstract

This application provides a composite material reinforcing sheet curing device, relating to the field of carbon fiber reinforced material testing technology. It includes an external frame with a top plate and a bottom plate respectively positioned above and below it. The lower surface of the top plate and the upper surface of the bottom plate are parallel to each other. Perpendicular limiting plates are provided on the outer periphery of both the lower surface of the top plate and the upper surface of the bottom plate. Elastic air bags are fixed to the lower surface of the top plate and the upper surface of the bottom plate, respectively. An air compressor is connected inside the elastic air bag via a pressurization pipeline. The pressurization pipeline is equipped with a pressure gauge and a pressure valve. A heating film is provided on the side of the elastic air bag that contacts the sample. The heating film is connected to a temperature control device. After the elastic air bag expands, it completely encloses the composite material sample and the composite material reinforcing sheet. After the elastic air bag presses onto the sample, it deforms. The sample of different specifications is fixed by lateral pressure and surface friction, and the reinforcing sheet is cured for testing the tensile and compressive properties of fiber-reinforced composite materials.

Description

Technical Field

[0001] This application relates to the field of carbon fiber reinforced material testing technology, and more specifically, to a composite material reinforcing sheet curing device. Background Technology

[0002] When performing tensile and compressive property tests on composite materials at 0° and in multidirectional laminates, corresponding reinforcing sheets need to be bonded to the test specimens to ensure effective failure within the working area during testing. Reinforcing sheet bonding typically uses epoxy resin adhesives, including structural adhesives and adhesive films. To ensure bonding effectiveness, the bonded parts need to be heated and pressurized to allow the adhesive to fully cure. During the period from heating and pressurizing to complete curing, the adhesive viscosity decreases and flow occurs, which can easily lead to problems such as insufficient adhesive, uneven adhesive layer thickness, and reinforcing sheet slippage. To address these issues, auxiliary fixtures are typically used to position and pressurize the test specimens. Typical existing methods for reinforcing sheet bonding and curing include vacuum bag autoclave pressurization and fixture pressurization.

[0003] Vacuum bag autoclave pressurization schemes include a molding device and method for specimens with reinforcing plates (publication number CN114103165A), and a reinforcing plate style and bonding method (publication number CN114323864A). To fix the relative position between the reinforcing plate and the specimen during pressurization, the specimen undergoes machining outside the test, and is fixed using structures such as locating pins. This fixing method can damage the test specimen. Due to the special properties of carbon fiber materials, internal machining can create stress concentration points, severely affecting the reliability of the test results.

[0004] There are several solutions for pressurizing tooling, including a multi-purpose device for bonding reinforcing sheets on tensile and compressive composite specimens (CN206440513U), a method for bonding reinforcing sheets on composite specimens (CN105711079A), and a device and method for pasting reinforcing sheets on fiber-reinforced plastic specimens (CN118881631A). These solutions can achieve fixation without machining, but in order to adapt to different sizes and testing requirements, it is necessary to change the position of the fixture and the fixing structure, and there is also the problem of uneven pressurization. Summary of the Invention

[0005] To address the aforementioned issues, this application employs a composite material reinforcing sheet curing device, comprising an external frame, with a top plate and a bottom plate positioned above and below the external frame, respectively. The lower surface of the top plate and the upper surface of the bottom plate are parallel to each other. Perpendicular limiting plates are provided on the outer periphery of both the lower surface of the top plate and the upper surface of the bottom plate. Elastic air bags are fixed below the top plate and above the bottom plate, respectively. The interior of each elastic air bag is connected to a pressure gauge, a pressure valve, and an air compressor via a pressurization pipeline. A heating film is provided on the side of the elastic air bag that contacts the sample, and the heating film is connected to a temperature control device. After the elastic air bag expands, it completely encloses the composite material sample and the composite material reinforcing sheet.

[0006] Optionally, the heating film is movably connected to the elastic inflatable bag;

[0007] Alternatively, the heating film is a distributed heating film arranged along the width direction of the composite material sample, and the distributed heating film is fixedly connected to the elastic air inflatable bag.

[0008] Optionally, the heating wires of the heating film are arranged in parallel to each other, and the length direction of the heating wires is parallel to the length direction of the composite material sample.

[0009] Optionally, the elastic air bags on the lower surface of the top plate and the upper surface of the bottom plate are equipped with exhaust valves.

[0010] Optionally, the inner side of the limiting plate is covered with an anti-adhesive layer made of polytetrafluoroethylene.

[0011] Optionally, the heating film is made of polytetrafluoroethylene;

[0012] Alternatively, the heating film is made of silicone rubber or polyimide, and the side of the heating film that contacts the composite material sample and the composite material reinforcing sheet is covered with a polytetrafluoroethylene layer.

[0013] Optionally, a height adjustment mechanism is provided between the top plate and the bottom plate. The height adjustment mechanism is as follows:

[0014] A sliding pair and a height limit lock are installed between the top plate and the bottom plate in the height direction;

[0015] Alternatively, the top plate is movably connected to a threaded column that is oriented downwards and fixed relative to the top plate in the height direction. The threaded column is perpendicular to the bottom surface of the top plate and has external threads on its side wall. The side wall of the threaded column has a height mark. The bottom plate is fixedly connected to an upward-oriented support column with an opening at the top and an internal thread that matches the threaded column.

[0016] Optionally, the elastic inflatable bag is made of silicone rubber.

[0017] Optionally, a temperature sensor is provided between the heating film and the composite material reinforcing sheet, and the temperature sensor and the temperature control device establish a communication connection through a signal transmission line.

[0018] Optionally, it also includes a control host and a control panel, wherein the temperature control device, temperature sensor, pressure gauge and air compressor establish communication connections with the control host and are regulated based on the control panel.

[0019] The beneficial effects of the composite material reinforcing sheet curing device provided in this application are as follows:

[0020] (1) Before the test, the composite material sample with the composite reinforcement sheet bonded is placed between the elastic air bags. First, the pressure valve is opened and the elastic air bags are expanded by the air compressor and the pressurization pipeline to fix the composite reinforcement sheet and the composite material sample. Then, heating is started and the composite reinforcement sheet is cured based on the heat regime and pressure control requirements for fixing the composite reinforcement sheet.

[0021] (2) After the elastic air bag is pressed on the sample, it deforms and fixes the sample of different specifications by lateral pressure and surface friction. It is widely used for the curing of the sample reinforcement sheet in the tensile test of fiber reinforced polymer matrix composites and the in-plane compression test of fiber reinforced plastics. The pressure is balanced and controllable at the position where the elastic air bag is attached to the reinforcement sheet or the sample itself. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0023] Figure 1 This is a front view schematic diagram of the composite material reinforcing sheet curing device provided in the embodiments of this application;

[0024] Figure 2 This is a three-dimensional schematic diagram from the left side of the composite material reinforcing sheet curing device provided in the embodiments of this application;

[0025] Figure 3 This is a three-dimensional schematic diagram from the right side of the composite material reinforcing sheet curing device provided in the embodiments of this application;

[0026] Figure 4 This is a front view schematic diagram of the height limiting lock of the composite material reinforcing sheet curing device provided in the embodiments of this application;

[0027] Figure 5 This is a bottom view schematic diagram of the distributed heating film provided in an embodiment of this application;

[0028] Figure 6 This is a three-dimensional schematic diagram of the distributed heating film provided in the embodiments of this application;

[0029] Figure 7This is a bottom view schematic diagram of the movable connection of the heating film provided in the embodiment of this application;

[0030] Figure 8 This is a three-dimensional schematic diagram of the movable connection of the heating film provided in the embodiment of this application;

[0031] Figure 9 This is a three-dimensional schematic diagram of a tensile specimen of a multi-directional laminate.

[0032] Figure 10 This is a schematic diagram of the control logic of the composite material reinforcing sheet curing device provided in the embodiments of this application.

[0033] Explanation of reference numerals in the attached drawings: 1-Top plate; 2-Bottom plate; 3-Elastic air bag; 4-Pressure booster pipe; 5-Pressure gauge; 6-Pressure valve; 7-Heating membrane; 8-Exhaust valve; 9-Limiting plate; 10-Threaded column; 11-Support column; 12-Upper column; 13-Lower column; 14-Height limit pin hole; 15-Height limit pin; 16-Temperature sensor; 17-Heating membrane connecting sleeve; 18-Temperature signal transmission line; 19-Heating wire; 20-Composite material sample; 21-Reinforcing sheet; 22-Long side of sample; 23-Short side of sample; 101-Control panel; 102-Control host; 103-Temperature control module; 104-Pressure control module. Detailed Implementation

[0034] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0035] Figure 9 To conform to the tensile test method for oriented fiber reinforced polymer matrix composites in GB / T 3354-2014, the multi-directional laminate tensile test specimen includes a specimen body 20 and a reinforcing sheet 21. The direction parallel to the long side 22 of the specimen is the specimen length direction, and the direction parallel to the short side 23 of the specimen is the specimen width direction. In some special cases, it may be difficult to distinguish between the long side 22 and the short side 23 of the specimen (such as in GB / T45461-2025, the specification for attaching reinforcing sheets for test specimens of carbon fiber composites). In this case, the side corresponding to the side with the larger side area is taken as the long side 22 of the specimen.

[0036] like Figures 1-5As shown, this application provides a composite material reinforcing sheet curing device, including an outer frame, with a top plate 1 and a bottom plate 2 respectively arranged above and below the outer frame. The lower surface of the top plate 1 and the upper surface of the bottom plate 2 are parallel to each other. A limiting plate 9 perpendicular to the lower surface of the top plate 1 and the upper surface of the bottom plate 2 are arranged on their outer periphery. An elastic air bag 3 is fixed on the lower surface of the top plate 1 and the upper surface of the bottom plate 2 respectively. The inside of the elastic air bag 3 is connected to a pressure gauge 5, a pressure valve 6 and an air compressor (not shown) in sequence through a pressurization pipeline 4. A heating film 7 is arranged on the side of the elastic air bag 3 that contacts the sample. The heating film 7 is connected to a temperature control device. After the elastic air bag 3 expands, it completely wraps the composite material sample 20 and the composite material reinforcing sheet.

[0037] Since the elastic air bag 3 completely wraps the composite material sample 20 and the composite material reinforcing sheet after expansion in the composite material reinforcing sheet curing device provided in this application, the shape of its vertical projection can be any shape. In this embodiment, it is a rectangle. As a feasible alternative, it can also be a circle or an irregular shape.

[0038] The lower surface of the top plate 1 and the upper surface of the bottom plate 2 are parallel to each other. The outer periphery of the lower surface of the top plate 1 and the upper surface of the bottom plate 2 are provided with limiting plates 9 perpendicular to them to ensure that the upper and lower elastic air bags 3 are opposite each other in the main expansion direction during expansion, so that the upper and lower elastic air bags can complete the maximum deformation and fit when fixing the composite material sample 20.

[0039] Before testing, the composite material sample 20 with the composite material reinforcing sheet 21 bonded is placed between the elastic air bags 3. First, the pressure valve 6 is opened, and the elastic air bags 3 are expanded by the air compressor and the pressurization pipeline 4 to fix the composite material reinforcing sheet 21 and the composite material sample 20. Then, heating is started, and the composite material reinforcing sheet 21 is cured based on the thermal regime and pressure control requirements for fixing the composite material reinforcing sheet 21.

[0040] After the elastic air bag 3 is pressed onto the sample, it deforms and fixes the sample of different specifications through lateral pressure and surface friction. The composite reinforcement sheet 21, which is widely used in tensile test of fiber-reinforced polymer matrix composites and in-plane compression test of fiber-reinforced plastics, is cured. At the position where the elastic air bag 3 is attached to the composite reinforcement sheet 21 or the composite sample 20 itself, the pressure is balanced and controllable.

[0041] In another embodiment of this application, such as Figure 5 and Figure 6As shown, the heating film 7 is a distributed heating film 7 arranged along the width direction of the composite material sample 20. Since the surface area of ​​the elastic air bag 3 will expand due to pressure after being pressurized, while the heating film 7 cannot expand its area at will due to the limitation of the internal heating wire 19 circuit, in order to prevent the heating film 7 from falling off or being stretched and damaged, as a feasible technical solution, a distributed heating film 7 is set on the surface of the elastic air bag 3 to minimize the impact of the change in the surface area of ​​the elastic air bag 3 on the heating film 7. The distributed heating film 7 is fixedly connected to the elastic air bag 3.

[0042] In this embodiment, the image is only a schematic diagram of the distributed installation direction and position, and is not intended to limit the specific quantity or size. In order to achieve a better anti-fall-off effect, the distributed heating film 7 with a narrower width and a larger number can be set according to actual needs.

[0043] Since the main deformation of the elastic air bag 3 occurs on both sides of the length direction of the composite material sample 20, the deformation of the elastic air bag 3 in the groove formed between the composite material reinforcing plates 21 at both ends is relatively small, and the distributed heating film 7 and the elastic air bag 3 are fixed along the length direction of the composite material sample 20.

[0044] In another embodiment of this application, such as Figure 7 and Figure 8 As shown, the heating film 7 and the elastic air bag 3 are movably connected. Due to the aforementioned reasons, in order to reduce the impact of changes in the surface area of ​​the elastic air bag 3 on the heating film 7, a movable connection is formed between the heating film 7 and the elastic air bag 3. In this embodiment, a heating film connecting sleeve 17 is fitted over the heating film 7, allowing the heating film 7 to move in the lateral and longitudinal directions. The side closer to the heating wire 19 is the inner side of the heating film connecting sleeve 17, and the side farther from the heating wire 19 is the outer side. When the elastic air bag 3 deforms, it presses the heating film 7 into the groove formed between the composite material reinforcing sheets 21 at both ends. The heating film 7 on the outer side of the heating film connecting sleeve 17 is drawn into the inner side of the heating film connecting sleeve 17, while maintaining the connection between the heating film 7 and the elastic air bag 3. After the test is completed, the heating film 7 drawn into the inner side of the heating film connecting sleeve 17 returns to the outer side of the heating film connecting sleeve 17 as the shape of the elastic air bag 3 recovers.

[0045] In this embodiment, two heating film connecting sleeves 17 are provided in both the length and width directions of the sample. The number and position of these sleeves are determined by the ability to achieve the above-mentioned functions, and no specific limitation is made on the number and position.

[0046] In another embodiment of this application, the heating wires 19 of the heating film 7 are arranged in parallel to each other, and the length direction of the heating wires 19 is parallel to the length direction of the composite material sample 20. In order to adapt to composite reinforcing sheets 21 of different sizes, the heating film 7 should have a heating range greater than that of the largest heating sheet. However, for the heating film 7, when it is pressed into both sides of the sample by the elastic air bag 3, the heating film 7—especially the non-distributed heating film 7—will bend to a certain extent, which will affect the service life of the heating wires 19. By arranging the heating wires 19 of the heating film 7 in parallel to each other, and the length direction of the heating wires 19 being parallel to the length direction of the composite material sample 20, the heating wires affected when the heating film 7 bends are minimized, thus extending the service life of the heating film 7.

[0047] In another embodiment of this application, both the lower surface of the top plate 1 and the upper surface of the bottom plate 2 are provided with exhaust valves 8 for the elastic air bags 3. After the test, the pressure valve 6 is closed and the exhaust valve 8 is opened to quickly discharge the gas inside the elastic air bags 3 and replace the next sample to be processed. Compared with the solution of evacuating air or directly lifting the top plate 1, this solution is more convenient to operate.

[0048] In another embodiment of this application, the inner surface of the limiting plate 9 is covered with an anti-adhesive layer made of polytetrafluoroethylene. Regardless of the precision of pressure control and sample fixation, adhesive leakage is always difficult to completely avoid. Therefore, an anti-adhesive layer is provided on the inner surface of the limiting plate 9 at locations where overflowing adhesive may come into contact, preventing the inner surface of the limiting plate 9 from adhering to the elastic air bag 3. Even if adhesion does occur, the anti-adhesive layer structure makes it easier to process the cured adhesive.

[0049] In another embodiment of this application, the heating film 7 is made of polytetrafluoroethylene. In order to be able to adapt to samples of various specifications, the heating range of the heating film 7 should cover all types of test samples. Therefore, when curing small-sized samples, the heating film 7 is also easily affected by adhesive leakage, and its surface should be an anti-stick material.

[0050] In another embodiment of this application, the heating film 7 is made of silicone rubber or polyimide, and the side of the heating film 7 that contacts the composite material sample 20 and the composite material reinforcing sheet 21 is covered with a polytetrafluoroethylene layer. Both silicone rubber and polyimide have high heat resistance, but their anti-adhesion effect is generally poor. Therefore, when they are used as the material of the heating film 7, the surface of the heating film 7 needs to be covered with an anti-adhesion polytetrafluoroethylene coating.

[0051] In another embodiment of this application, such as Figure 4 As shown, a height adjustment mechanism is provided between the top plate 1 and the bottom plate 2. The height adjustment mechanism is as follows:

[0052] A sliding pair and a height limit lock are provided between the top plate 1 and the bottom plate 2 in the height direction;

[0053] The sliding pair includes an upper column 12 and a lower column 13 with a clearance fit. The upper column 12 is fixed below the top plate 1, and the lower column 13 is fixed above the bottom plate 2. Height limiting pin holes 14 are provided at corresponding positions on the upper column 12 and the lower column 13. Multiple sets of height limiting pin holes 14 are provided on the upper column 12 and the lower column 13. The height of the height limiting pin holes 14 is the same in different sets of upper column 12, and the height of the height limiting pin holes 14 is the same in different sets of lower column 13. Height limiting pins 15 simultaneously pass through the height limiting pin holes 14 of the same set of upper column 12 and lower column 13 to lock the relative positions of the upper column 12 and the lower column 13, thereby fixing the relative position between the top plate 1 and the bottom plate 2. This solution allows for rapid height adjustment.

[0054] To more stably fix the relative position between the top plate 1 and the bottom plate 2, a height limiting pin hole 14 with internal threads and a height limiting pin 15 with external threads can be provided to cooperate with each other.

[0055] In another embodiment of this application, such as Figures 1-3 As shown, a height adjustment mechanism is provided between the top plate 1 and the bottom plate 2. The height adjustment mechanism consists of a threaded post 10 movably connected to the top plate 1, pointing downwards and fixed relative to the top plate 1 in the height direction. The threaded post 10 is perpendicular to the bottom surface of the top plate 1 and has external threads on its sidewalls. A height indicator (marked according to actual dimensions, not shown in the figure) is provided on the sidewalls of the threaded post 10. An upward-pointing support column 11 is fixedly connected to the bottom plate 2. The support column 11 has an opening at its top, and an internal thread matching the external threads of the threaded post 10 is provided inside. Compared to a height limit lock solution, the solution provided in this embodiment allows for more precise height adjustment. When no fine adjustment is needed, quick positioning is achieved through the height indicator. When fine adjustment is required, the distance between the top plate 1 and the bottom plate 2 can be directly measured using calipers or other equipment.

[0056] In another embodiment of this application, the elastic inflatable bag 3 is made of silicone rubber. Silicone rubber has good elasticity and heat resistance, making it suitable for simultaneously heating and pressurizing the composite material reinforcing sheet 21. It also has good electrical insulation properties, making it suitable for use in conjunction with the heating film 7. Therefore, it is suitable as a material for preparing elastic inflatable bags.

[0057] In another embodiment of this application, such as Figures 5-8 As shown, a temperature sensor 16 is installed between the heating film 7 and the composite material reinforcing sheet 21. The temperature sensor 16 and the temperature control device establish a communication connection through a signal transmission structure. When adjusting the thermal power of the heating film 7 solely through the temperature control device is insufficient to meet precise control, the actual temperature is measured by the temperature sensor 16, and the signal is fed back to the temperature control device through the temperature signal transmission line 18. The temperature is then adjusted based on the difference between the actual temperature and the set temperature to eliminate experimental condition deviations.

[0058] In another embodiment of this application, such as Figure 10 As shown, the system also includes a control host 102 and a control panel 101. Temperature control module 103 and pressure control module 104 establish communication connections with the control host 102 and are adjusted based on the control panel 101. Signals are received and converted through the control host 102, and human-machine interaction is performed through the control panel 101 with an LED screen. Control signals are then provided by the control host 102 to control the curing temperature by controlling the output power of the heating film 7 and to control the pressure of the elastic air bag 3 by controlling the opening and closing of the air compressor, thus comprehensively controlling the experimental parameters of the composite material reinforcing sheet curing device.

[0059] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A composite patch curing apparatus comprising an outer frame, characterised in that: A top plate and a bottom plate are respectively provided above and below the external frame. The lower surface of the top plate and the upper surface of the bottom plate are parallel to each other. A limiting plate perpendicular to the lower surface of the top plate and the upper surface of the bottom plate are provided on their outer periphery. An elastic air bag is fixed below the top plate and above the bottom plate. The inside of the elastic air bag is connected to a pressure gauge, a pressure valve and an air compressor in sequence through a pressurization pipeline. A heating film is provided on the side of the elastic air bag that contacts the sample. The heating film is connected to a temperature control device. After the elastic air bag expands, it completely wraps the composite material sample and the composite material reinforcing sheet.

2. The composite patch curing apparatus of claim 1, wherein: The heating film is movably connected to the elastic air-inflatable bag; Alternatively, the heating film may be a distributed heating film arranged along the width direction of the composite material sample, and the distributed heating film may be fixedly connected to the elastic air-inflating bag.

3. The composite patch curing apparatus of claim 2, wherein: The heating wires of the heating film are arranged in parallel to each other, and the length direction of the heating wires is parallel to the length direction of the composite material sample.

4. The composite patch curing apparatus of claim 1, wherein: Both the lower surface of the top plate and the upper surface of the bottom plate are equipped with air vents on their elastic air bags.

5. The composite patch curing apparatus of claim 1, wherein: The inner side of the limiting plate is covered with an anti-adhesive layer, which is made of polytetrafluoroethylene.

6. The composite material reinforcing sheet curing device as described in claim 5, characterized in that: The heating film is made of polytetrafluoroethylene. Alternatively, the heating film may be made of silicone rubber or polyimide, and the side of the heating film that contacts the composite material sample and the composite material reinforcing sheet may be covered with a polytetrafluoroethylene layer.

7. The composite patch curing apparatus of claim 1, wherein: A height adjustment mechanism is provided between the top plate and the bottom plate, and the height adjustment mechanism is as follows: A sliding pair and a height limit lock are installed between the top plate and the bottom plate in the height direction; Alternatively, the top plate is movably connected to a threaded post that is oriented downwards and fixed relative to the top plate in the height direction. The threaded post is perpendicular to the bottom surface of the top plate and has external threads on its sidewalls. The sidewalls of the threaded post have height markings. The bottom plate is fixedly connected to an upward-oriented support column with an opening at the top and an internal thread matching the threaded post inside.

8. The composite patch curing apparatus of claim 1, wherein: The elastic air-inflatable bag is made of silicone rubber.

9. The composite patch curing apparatus of claim 1, wherein: A temperature sensor is provided between the heating film and the composite material reinforcing sheet, and the temperature sensor and the temperature control device are connected through a signal transmission line.

10. The composite patch curing apparatus of claim 9, wherein: It also includes a control host and a control panel. The temperature control device, temperature sensor, pressure gauge and air compressor are respectively connected to the control host and are regulated based on the control panel.

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