A preparation method and device for compression molding of laminated panels at room temperature

Abstract

The present invention relates to the technical field of composite material preparation, and in particular to a preparation method and device for molding a laminate at room temperature. The method comprises the following steps: S1. Laying and fixing a plurality of fiber cloths in order to maintain the basic shape of the fiber layer; S2. Putting a bag into a container and placing the fiber cloth flat in the container; pouring resin until the resin submerges the fiber cloth; S3. Putting the container into a vacuum box and evacuating the air until no obvious bubbles emerge from the resin, closing the evacuation, taking out the container and letting it stand; S4. Slowly taking out the bag containing the resin and the fiber cloth, laying it flat on a lower template coated with a release agent, placing a container for receiving the resin at the open end of the bag, and then covering the bag with an upper template coated with a release agent; S5. Clamping the upper and lower templates with a clamp and letting it stand until the resin is cured; S6. Removing the clamp and opening the mold, removing the bag to obtain a formed laminate. The present invention has a simple structure, is easy to use, has a mature process, is low in cost, and is highly practical.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material preparation, and in particular to a preparation method and a device for laminated plates through compression molding at room temperature. Background Art

[0002] In the engineering and scientific applications of resin-based fiber composites, laminates are one of the most commonly used design structures. The ease of forming laminates makes their fabrication process highly designable. Traditional vacuum-assisted molding (VARTM) uses a vacuum pump to prestress the part. A rigid mold and vacuum bag are used to create the mold cavity. Specifically, the fiber layer is laid first, then a release sheet (for mold release), a release film (to separate the mesh from the release sheet), and a mesh (to provide a flow path for the resin). Flow tubes are placed at the inlet and outlet ports, and the vacuum bag is sealed with sealing strips. The resin is then drawn in under a constant vacuum pressure. Before drawing in the resin, the entire mold cavity must be checked for airtightness. First, close the inlet, apply vacuum, and then shut down the entire system. The vacuum bag is then left to stand for 45 minutes to observe for looseness and leaks. If leaks are detected throughout the mold cavity, the entire assembly must be inspected. In severe cases, the vacuum bag must be replaced and resealed, a time-consuming and labor-intensive process that can waste materials. Without proper airtightness testing, the resin typically cures in 6-9 hours. Leaks can significantly reduce the prestress in the laminate, significantly impacting its performance.

[0003] Current vacuum-assisted molding technology creates a vacuum environment between a vacuum bag and a rigid mold cavity, uses a vacuum pump to draw out the resin, and after the resin and fiber cloth are fully in contact and bonded, the vacuum pump is turned off and the two guide ports are locked. This creates a prestressed state in the vacuum environment for the resin-based composite laminate, causing the laminate to solidify. However, vacuum-assisted molding technology has the following problems:

[0004] 1) After the mold cavity is made using a rigid mold and a vacuum bag, a lot of time is needed to check the airtightness of the mold cavity;

[0005] 2) If the airtightness is not good, the mold cavity must be remade, wasting materials;

[0006] 3) Generally, the resin curing process after resin infusion requires vacuum to provide prestress. A mold cavity with poor airtightness will cause a significant decrease in prestress, thereby affecting the performance of the laminate.

[0007] Hot press molding technology uses a hot press to press prepreg into shape. First, the prepreg is cut to size and laid out in a certain order. The prepreg is then placed in a mold. Here, taking a typical laminate as an example, two metal plates clamp the prepreg and place it in a hot press set at a set temperature and pressure for hot pressing. This molding process is fast and convenient. However, hot press molding technology has the following problems:

[0008] 1) Hot pressing is used for prepregs, but the resin saturation of prepregs is low. For vacuum resin infusion process, the porosity of the laminate is large, which affects the mechanical properties of the laminate.

[0009] 2) Hot presses are expensive, energy-intensive, and not environmentally friendly. Summary of the Invention

[0010] The present invention provides a preparation method and a device for laminated plate compression molding at room temperature, aiming to solve the problems existing in the existing laminated plate molding technology.

[0011] The present invention provides a method for preparing a laminate by compression molding at room temperature, comprising the following steps:

[0012] S1. Lay out multiple fiber cloths in order and fix multiple layers of fiber cloth to maintain the basic shape of the fiber layer;

[0013] S2. Place the bag in a container that can hold the fiber cloth parallel to the container and lay the fiber cloth flat in the container; slowly pour the resin into the container until the resin submerges the fiber cloth;

[0014] S3. Place the container in a vacuum box and evacuate until no obvious bubbles emerge from the resin. Turn off the vacuum, remove the container and let it sit.

[0015] S4. Slowly remove the bag containing the resin and fiber cloth, wrap the bag with the resin and fiber cloth, and lay it flat on the lower template coated with a release agent. Place a container to receive the resin at the open end of the bag, and then cover the bag with an upper template coated with a release agent.

[0016] S5. Clamp the upper and lower templates with a fixture and let them stand until the resin is cured.

[0017] S6. Remove the clamp and open the mold, remove the bag and obtain the formed pressed board.

[0018] As a further improvement of the present invention, in step S1, the method of fixing the plurality of fiber cloths includes: fixing the four sides of the plurality of fiber cloths with fasteners, or fixing the plurality of fiber cloths with fiber setting spray.

[0019] As a further improvement of the present invention, the bag is a high-temperature resistant vacuum bag made of 100% nylon.

[0020] As a further improvement of the present invention, the resin is curable at room temperature and liquid at high temperature.

[0021] As a further improvement of the present invention, in step S5, multiple G-type clamps are used to clamp multiple corners of the upper template and the lower template to continuously and evenly provide molding pressure for the laminate.

[0022] As a further improvement of the present invention, step S5 further includes using a pressure detection device to monitor the pre-pressure value provided by the G-type clamp during each pressing.

[0023] The present invention also provides a preparation device for laminated panels compression molding at room temperature, which is used to perform the preparation method for laminated panels compression molding at room temperature, including a bag with one end open, a container, and a vacuum box, the bag is loaded with fiber cloth and resin, the bag is laid flat in the container, the container is arranged in the vacuum box, and the vacuum box is connected to an external exhaust device.

[0024] As a further improvement of the present invention, the preparation device for compression molding of laminates at room temperature also includes a rigid template, a G-type clamp, and a container. The rigid template includes an upper template and a lower template. A bag filled with fiber cloth and resin is arranged between the upper template and the lower template. Multiple G-type clamps are clamped at multiple top corners of the upper template and the lower template, and the container is docked with the open end of the bag.

[0025] As a further improvement of the present invention, the G-type clamp includes a clamp bracket, a clamping screw, and a handle. The bottom end of the clamp bracket hooks the lower template, the top of the clamp bracket is provided with a threaded hole, the clamping screw is connected to the threaded hole, the bottom of the clamping screw supports the upper template, and the top of the clamping screw is connected to the handle.

[0026] As a further improvement of the present invention, the contact surfaces of the upper template, the lower template and the bag are coated with a release agent.

[0027] The present invention has the following beneficial effects: simple structure, ease of use, mature process foundation, ease of implementation, low cost, low energy consumption, low carbon emissions from the entire preparation process, and strong practicality, capable of producing different specimen shapes and sizes by changing the mold. It effectively ensures continuous prestressing during the curing process, avoiding the impact of prestressing on the performance of the laminate due to a decrease in prestressing. Compared with vacuum-assisted molding processes, it saves the time and cost of checking airtightness, eliminates the energy consumption of long-term vacuum pumping of resin, and improves the stability of material preparation. Compared with hot pressing processes, it reduces the porosity of the laminate and requires less equipment and operating space. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a first structural diagram of a preparation apparatus for compression molding a laminate at room temperature according to the present invention;

[0029] Figure 2 This is the second structural diagram of the preparation device for compression molding of the laminated board at room temperature according to the present invention. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0031] The present invention provides a method for preparing laminates by compression molding at room temperature, particularly involving laminates in which resin can be cured and molded at room temperature. Based on the Vacuum Assisted Molding (VARTM) process, the room temperature compression molding process is divided into two steps: the first step involves degassing the resin in a vacuum chamber to ensure full contact between the fiber cloth 1 and the resin and remove excess air; the second step involves clamping the mold plate with a G-type clamp 5 to provide continuous pressure on the laminate.

[0032] The preparation process of the first part specifically includes the following steps:

[0033] S1. Lay out multiple fiber sheets 1 in order and secure them. Methods for securing the fiber sheets 1 include using paper clips to secure the edges of the fiber sheets 1 or using a fiber-setting spray to prevent them from moving. This securing method is applicable not only to fiber laminates but also to metal fiber laminates. Simply stack the fiber and metal layers in a certain order and secure the basic shape.

[0034] S2. Place bag 2 in a container that can hold the fiber cloth 1 in parallel, and place the fiber cloth 1 flat in container 3. Slowly pour resin into container 3 until the resin submerges the fiber cloth 1. Place the fiber cloth 1 in bag 2 and pour an appropriate amount of resin into bag 2 to allow the fiber cloth 1 to be soaked in the resin.

[0035] The resin must be liquid and capable of curing at room temperature, exhibiting a certain degree of fluidity. Bag 2 is preferably a 100% nylon vacuum bag, which resists bonding with the resin and can withstand high temperatures. For laminates requiring post-curing, the vacuum bag must also be heat-resistant and suitable for temperatures that meet the post-curing temperature of the laminate.

[0036] Place the bag 2 containing the resin and fiber cloth 1 flatly in a container 3 of sufficient size, so that the fiber cloth 1 is evenly immersed in the resin. The opening of the bag 2 should be facing upwards to facilitate the extraction of the air between the fiber cloth 1 and the resin in the vacuum chamber. Slowly add the resin into the container until the resin completely submerges the fiber stack. If the fiber cloth (such as polyethylene fiber) has low wettability with the resin and floats above the resin, you need to use a glass rod to press the fiber cloth appropriately to fully soak it with the resin.

[0037] S3. Place container 3 in a vacuum chamber and evacuate until no bubbles are released from the resin. For example, using 500ml of resin, evacuate for 10 minutes, until no bubbles are released. This vacuuming removes excess bubbles from the resin and fiber cloth 1, reducing the porosity of the laminate and improving its mechanical properties. Taking advantage of the one-way resin flow provided by the vacuum-assisted molding process, the vacuum pressure is used to remove bubbles from the fiber-resin gap.

[0038] Finally, turn off the vacuum pump to stop pumping, take out the container 3, and let it stand for 5 minutes to allow the resin and fiber cloth 1 to continue to fully infiltrate, then slowly take the bag 2 out of the container 3. Be careful not to shake the resin to avoid generating excess bubbles.

[0039] The rigidity of container 3 needs to be such that when the resin is introduced into container 3, container 3 does not deform significantly. A PVC plastic container can be used. The size of container 3 must meet the size requirements of the vacuum box. Evacuating the resin for 10 minutes is beneficial to reducing the porosity of the resin after curing. Let it stand for 5 minutes to allow the resin to more fully infiltrate the fiber cloth.

[0040] The preparation process of the second part specifically comprises the following steps:

[0041] S4. Take out the fiber cloth 1 that has been evacuated and pre-impregnated with resin from the vacuum bag. The bag 2 needs to completely wrap the resin and the fiber cloth 1. The ply of the fiber cloth 1 cannot be disturbed. Pinch the opening of the bag 2 with one hand to form a sealed state to prevent the resin from flowing out and spilling during movement. At the same time, support the bottom of the bag 2 with the other hand to maintain the basic appearance of the fiber cloth 1. Then, lay the bag 2 with the bag opening facing up on the center of the lower template 42 coated with a release agent, ensuring that the fiber cloth 1 is in a flat state. The purpose of applying the release agent to the lower template 42 is to prevent the resin from overflowing and remaining on the mold, which is convenient for cleaning later. Then cover the bag 2 with the upper film plate coated with a release agent. At this time, the bag 2 opening is facing one side around the mold, and a container 6 is placed on one side to allow excess resin to flow out during the extrusion process of the laminate. It is recommended to simply wrap the bag 2 opening with tape or a rubber band to fix it, leaving an opening of 2-3 cm in diameter to prevent the bag 2 from spreading over a large area and causing unorganized flow of resin.

[0042] S5. Use a clamp to clamp the upper template 41 and the lower template 42, and place a container 6 for receiving the resin at the open end of the bag 2; let it stand until the resin is completely solidified; use multiple G-type clamps 5 to fix and clamp multiple corner points of the upper and lower templates to continuously provide molding pressure for the laminate. Considering different performance requirements, the number of G-type clamps 5 can be increased at will. Taking the preparation of a 3mm thick fiber laminate as an example, six G-type clamps 5 are used for fixing and clamping. The distance between the upper and lower templates is clamped to 3.2mm by the clamps 5. The extra 0.2mm distance takes into account the thickness of the vacuum bag. At the same time, a pressure detection device (thin film pressure distribution test system) can also be used to monitor the pre-pressure value provided by the G-type clamp 5 during each preparation, that is, the pressure applied by the template to the laminate, and control the range of molding pressure during each preparation to achieve accurate control of the mechanical properties of the laminate.

[0043] After clamping the mold tightly, let it sit until the resin cures. During this time, pressure can be continuously applied to the laminate without the risk of vacuum leaks causing the pressure to drop or disappear.

[0044] S6. Remove the clamp and open the mold, remove the bag 2 and obtain the formed pressed plate.

[0045] The present invention proposes a method for preparing laminates that can be compression molded at room temperature. This method overcomes the shortcomings of the complicated operation of the vacuum-assisted molding process and the high cost of the hot pressing molding process. While simplifying the preparation process, it can ensure that there is continuous pressure during the curing process of the laminate, and prepare laminates with lower porosity. It solves the problem that the vacuum bag has poor airtightness, resulting in no continuous pre-pressure during the curing of the laminate, which further causes a significant decrease in the performance of the laminate. At the same time, it can achieve low-energy preparation of laminates, and can also improve the preparation of specimens of different shapes by changing the fixture, including changing the material composition. This method and device can not only prepare fiber laminates, but also prepare fiber metal laminates, honeycomb sandwich laminates and other laminates that can be cured at room temperature, and has a certain degree of universality.

[0046] In conjunction with the method for preparing the laminate by compression molding at room temperature, the present invention is also designed to prepare a device for compression molding the laminate at room temperature. The device includes a bag 2 with an open end, a container 3, and a vacuum box. The bag 2 is loaded with fiber cloth 1 and resin, and the bag 2 is laid flat in the container 3. The container 3 is set in the vacuum box, and the vacuum box is connected to an external exhaust device. This structure omits the vacuum resin guide part and directly puts the fiber cloth 1 into the bag 2 filled with resin, and then lays it flat in the square container 3. The purpose is to allow the fiber cloth 1 to be evenly immersed in the resin. The container 3 is then placed in the vacuum box for exhaust. During this period, the bag 2 is opened upward to facilitate the extraction of gas between the fiber and the resin in the vacuum box. The bag 2 is a vacuum bag, and the container 3 is a square container 3.

[0047] The device also includes a rigid template 4, a G-type clamp 5, and a container 6. The rigid template 4 includes an upper template 41 and a lower template 42. A bag 2 containing a fiber cloth 1 and resin is positioned between the upper and lower templates 41, 42. Multiple G-type clamps 5 are clamped at multiple corners of the upper and lower templates 41, 42. The container 6 docks with the open end of the bag 2. The contact surfaces of the upper and lower templates 41, 42 with the bag 2 are coated with a release agent. The device comprises two rigid templates 4, namely an upper template 41 and a lower template 42, and four G-type clamps 5. During use, the fiber cloth 1, which has been pre-impregnated with resin, is removed from the vacuum bag and placed between the two rigid templates 4. An upper mold holder coated with a release agent is then placed on top of the vacuum bag. Four G-type clamps are used to secure the four corners of the two templates. The open end of the bag 2 is secured with a container 6 to receive the extruded resin. After the mold is clamped on all sides, it is left to stand until the resin solidifies. This clamping structure allows continuous pressure to be applied to the laminate during curing without the need to worry about vacuum leaks causing the pressure to drop or disappear.

[0048] The G-type clamp 5 includes a clamp bracket 51, a clamping screw 52, and a handle 53. The bottom end of the clamp bracket 51 hooks onto the lower template 42. The top end of the clamp bracket 51 is provided with a threaded hole, which is connected to the clamping screw 52. The bottom of the clamping screw 52 abuts the upper template 41, and the top of the clamping screw 52 is connected to the handle 53. The clamp bracket 51 has a C-shaped structure, with its bottom end abutting the lower template 42. The clamping screw 52 is screwed through the handle 53. The connection between the clamping screw 52 and the threaded hole allows the clamping screw 52 to move up and down relative to the top end of the upper clamp bracket 51, thereby adjusting the distance between the upper template 41 and the lower template 42, thereby continuously applying pressure to the fiber cloth 1 and resin in the bag 2.

[0049] The compression molding process addresses the time and cost associated with vacuum-assisted compression molding airtightness checks, as well as the subsequent reduction in prestress during curing, which can lead to decreased laminate performance. This reduces mold cavity airtightness checks, lowers production costs, and provides a constant level of prestress during the laminate's curing process. The addition of a vacuum chamber evacuation step also reduces the laminate's porosity, resulting in a lower porosity and improved mechanical properties.

[0050] Compared with the prior art, the present invention has the following advantages:

[0051] 1) Save time. The traditional vacuum resin infusion process has very high requirements for airtightness, and checking the airtightness is very time-consuming. If the vacuum bag is found to be damaged or the airtightness is poor after the entire mold is sealed, the sealing process must be restarted, which is time-consuming and material-intensive.

[0052] 2) Flexible and simple operation. G-type clamps 5 provide pressure, eliminating the need for vacuum bags or heavy objects. If the resin requires post-curing, the entire assembly can be placed in an oven for heating, making it suitable for the preparation of a variety of resin systems. To further stabilize the process, a pressure detection device can be added to measure the preload on the laminate caused by the number of clamps and the clamp tightening depth during preparation, ensuring the mechanical stability of each part. Training costs for technicians are also low.

[0053] 3) The device is economical and practical. Only two 5-6mm thick 2024-T3 grade aluminum plates are required as rigid templates 4, which are strong enough to compress the laminate without deforming the mold.

[0054] 4) Universal applicability. Applicable to a variety of room temperature curable laminates, such as fiber metal laminates and honeycomb sandwich laminates.

[0055] 5) It is machine-variable. By changing the size and shape of the mold, various types of laminates can be produced to meet the needs of real-world applications for laminates of various sizes.

[0056] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a laminate by compression molding at room temperature, characterized in that: The following steps are involved: S1. Lay out multiple fiber cloths in order and fix multiple layers of fiber cloth to maintain the basic shape of the fiber layer; S2. Place the bag in a container that can be parallel to the fiber cloth and place the fiber cloth flat in the bag of the container; slowly pour the resin into the bag of the container until the resin submerges the fiber cloth; S3. Place the container in a vacuum box and evacuate until no obvious bubbles emerge from the resin. Turn off the vacuum, remove the container and let it sit. S4. Slowly remove the bag containing the resin and fiber cloth, wrap the bag with the resin and fiber cloth, and lay it flat on the lower template coated with a release agent. Place a container to receive the resin at the open end of the bag, and then cover the bag with an upper template coated with a release agent. S5. Clamp the upper and lower templates with a fixture and let them stand until the resin is cured. S6. Remove the clamp and open the mold, remove the bag and obtain the formed pressed board.

2. The method for preparing a laminate by compression molding at room temperature according to claim 1, characterized in that: In the step S1, the method of fixing the plurality of fiber cloths includes: fixing the four sides of the plurality of fiber cloths with fasteners, or fixing the plurality of fiber cloths with fiber setting spray.

3. The method for preparing a laminate by compression molding at room temperature according to claim 1, characterized in that: The bag is a high-temperature resistant vacuum bag made of 100% nylon.

4. The method for preparing a laminate by compression molding at room temperature according to claim 1, characterized in that: The resin is curable at room temperature and liquid at high temperature.

5. The method for preparing a laminate by compression molding at room temperature according to claim 1, characterized in that: In step S5, multiple G-type clamps are used to clamp multiple corners of the upper template and the lower template to continuously and evenly provide molding pressure for the laminate.

6. The method for preparing a laminate by compression molding at room temperature according to claim 5, characterized in that: The step S5 further includes using a pressure detection device to monitor the pre-pressure value provided by the G-type clamp during each pressing.

7. A preparation device for laminated board compression molding at room temperature, used for executing the preparation method for laminated board compression molding at room temperature according to any one of claims 1 to 6, characterized in that: The invention comprises a bag with one end open, a container and a vacuum box. The bag is loaded with fiber cloth and resin and is laid flat in the container. The container is arranged in the vacuum box, and the vacuum box is connected to an external exhaust device.

8. The device for preparing laminates by compression molding at room temperature according to claim 7, characterized in that: It also includes a rigid template, a G-type clamp, and a container. The rigid template includes an upper template and a lower template. A bag filled with fiber cloth and resin is set between the upper template and the lower template. Multiple G-type clamps are clamped at multiple top corners of the upper template and the lower template, and the container is docked with the open end of the bag.

9. The apparatus for preparing laminates by compression molding at room temperature according to claim 8, characterized in that: The G-type clamp includes a clamp bracket, a clamping screw, and a handle. The bottom end of the clamp bracket hooks the lower template, the top of the clamp bracket is provided with a threaded hole, the clamping screw is connected to the threaded hole, the bottom of the clamping screw supports the upper template, and the top of the clamping screw is connected to the handle.

10. The device for preparing laminates by compression molding at room temperature according to claim 8, characterized in that: The contact surfaces of the upper template, the lower template and the bag are coated with a release agent.

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