Locally transparent visual RTM mold and manufacturing method

Abstract

The invention provides a locally transparent and visual RTM mold and a manufacturing method, and relates to the technical field of composite material molding.The locally transparent and visual RTM mold comprises an upper mold and a lower mold, the upper mold and the lower mold are fixed through a second connecting piece and matched with each other to form a cavity, the upper mold comprises a frame, the frame is provided with a plurality of grooves, and the grooves are communicated with the upper mold and the lower mold. The groove is used for limiting and assembling the visible material, the groove is provided with an opening, and the visible material can block the opening; the visual material is connected with the frame through a plurality of first connecting pieces, the first connecting pieces are evenly distributed along the periphery of the visual material, a sealing structure is arranged on the peripheral side of the visual material, and the sealing structure is installed in the groove. By optimizing the upper die, it is ensured that the structural strength of the upper die can meet the RTM process requirement, meanwhile, good sealing can be achieved through filling of gaps around a visible material and arrangement of a sealing structure, the service life of the die is long, and the product quality is good.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material molding, and in particular to a partially transparent and visualized RTM mold and a manufacturing method thereof. Background Art

[0002] Resin Transfer Molding (RTM) is an advanced process for manufacturing high-performance fiber-reinforced composite materials. It is done by laying out the fiber-reinforced material preform calculated according to the design requirements in a pre-made cavity that meets the process dimensions. Then, a special resin system is injected into the closed cavity using an injection device within a certain pressure range. High-performance composite materials are prepared by curing and molding after the resin and reinforcement are infiltrated. It has the advantages of low cost, fast molding speed, good product quality, low environmental pollution, and the ability to manufacture large and complex structural components. Therefore, it has been widely used in the fields of aerospace and transportation.

[0003] At present, in the process of resin sheet molding, the molding cavity is provided by closing the upper and lower molds, and the molding effect is stable. However, in the molding process, since the upper and lower molds are both opaque structures, it is impossible to intuitively judge the flow front of the resin at different times during the injection process, and it is also impossible to judge whether there is uneven flow, bubble agglomeration, dry spots, etc. at a certain place, resulting in a high defect rate of the final product.

[0004] To this end, the Chinese patent application number 201921717534.0 discloses a visual RTM molding mold, including a lower mold and an upper mold, the upper mold including a frame and a glass plate, the glass plate is fitted with the lower mold, the opening located in the recessed area of ​​the lower mold is closed to form a cavity for molding the resin, and the frame is used to provide the glass plate with an extrusion force for fitting on the lower mold through connection with the lower mold. This solution realizes the visualization of the resin flow in the cavity by splitting the upper mold to form a transparent part.

[0005] In addition, the Chinese patent application number 201710356088.4 discloses a visual RTM mold for steplessly adjusting the thickness of composite sheet materials, wherein the upper mold plate is embedded with toughened glass; the lower mold plate is fixed to the frame by a fixing member, a sliding member is provided inside the fixing member, a linkage member is fixed to the bottom surface of the sliding member, and a cavity adjustment mechanism for driving the linkage member and the sliding member to move up and down is installed on the sliding member and the linkage member; the sliding member and the linkage member are provided with injection holes and outlet holes; a flow channel is provided around the upper end of the middle through hole of the fixing member leading to the closed cavity, and is connected to the injection hole. This solution uses toughened glass as an observation window on the upper mold plate to observe the resin filling flow.

[0006] However, in order to ensure that the mold meets the strength and rigidity requirements of the RTM process, glass is used as the visible material. Due to the relatively low toughness of glass, it cannot withstand the pressure during resin injection in the RTM process and the temperature changes during the curing process and break or deform. In addition, due to the different thermal conductivity of the glass plate and the metal mold, the temperature distribution of the formed body in the mold during curing is uneven, affecting the final product quality. Furthermore, since the glass plate and the upper mold are fixed with screws, the sealing of the connection is poor and the flatness is difficult to guarantee. Summary of the invention

[0007] The problem solved by the invention is that the existing visual RTM mold has the disadvantages of short service life and unsatisfactory quality of the molded body.

[0008] In order to solve the above problems, the present invention provides a partially transparent visual RTM mold, including an upper mold and a lower mold, which are fixed by a second connecting member and cooperate with each other to form a cavity, and the upper mold includes a frame, and a plurality of grooves are arranged on the frame for limiting the assembly of visual materials, and the grooves are provided with openings, and the visual material can block the openings; the visual material is connected to the frame through a first connecting member, and there are multiple first connecting members and they are evenly distributed along the periphery of the visual material, and a sealing structure is arranged on the outer peripheral side of the visual material, and the sealing structure is installed in the groove.

[0009] This setting can realize the visualization of the RTM mold, and at the same time, the upper mold used to form the cavity is made of visible material and a frame evenly arranged, ensuring uniform temperature conduction and excellent quality of the final product. At the same time, the visible material is a PC board, which has low difficulty in processing and opening holes, and will not break due to improper force during the assembly process.

[0010] Preferably, there is a gap of 0.5-1.0 mm between the four sides of the visible material and the groove, and the sealing structure is a sealing strip connected end to end, and the sealing strip is located between the openings of the first connecting member.

[0011] This setting can create a gap between the visible material and the groove, and the gap is filled to achieve initial sealing; then a secondary seal is performed through the sealing structure to isolate the outside air, and the two cooperate with each other to meet the sealing requirements of the PC board as the visible material.

[0012] Preferably, a cavity is provided in the sealing strip, and the interface is overlapped obliquely and sealed with glue, and the groove is provided with an assembly groove for accommodating the sealing strip; the widths of the assembly groove and the sealing strip are L1 and L2 respectively, wherein L1=L2+D and the value of D is 2-6mm. This setting can ensure that the sealing structure itself has a good compression space, and at the same time, air is always present in the cavity of the sealing strip, which will not be over-extruded and has a good sealing effect.

[0013] Preferably, a reinforcing rib is provided in the middle of the opening to support the flat visual material. Compared with metal materials, visual materials such as PC boards have good toughness but poor strength, and are easily bent and deformed when subjected to a pressure shock of 1 MPa during the RMT process. This arrangement can support visual materials, especially PC boards, to prevent them from excessive deformation or even breakage.

[0014] Preferably, the frame is provided with a first reinforcing rib and a second reinforcing rib on a side away from the visible material, the first reinforcing ribs are provided in parallel with each other, the second reinforcing ribs are provided in parallel with each other, the first reinforcing ribs and the second reinforcing ribs are vertically connected to each other and are integrally formed with the frame. This arrangement can strengthen the structure of the upper mold with multiple openings, so that the visible area formed by the visible material has a high proportion in the upper mold, and the injection process can be better observed.

[0015] Preferably, the first connecting member is a countersunk bolt, a matching hole is arranged on the groove, the countersunk bolt is connected with the matching hole after passing through the visible material, the visible material and the side of the countersunk bolt close to the lower mold are in the same plane, and the visible material and at least part of the frame are in the same plane.

[0016] Preferably, the length of a single visible material is 50 mm-300 mm, the width is 50-300 mm, the minimum distance between two adjacent visible materials is 60 mm, and the thickness of the visible material is at least 20 mm.

[0017] Preferably, a seal is provided between the upper die and the lower die, the seal is annular and is located on the outer peripheral side of the cavity, and the upper die and / or the lower die are provided with a plurality of glue injection ports.

[0018] The present invention also provides a method for manufacturing a partially transparent and visualized RTM mold, comprising:

[0019] S1. Simulate and check the designed local visual RTM mold to ensure that it meets the use requirements under extreme pressure;

[0020] S2. Machining the upper die to form a groove and an opening, opening an assembly groove on the outer peripheral side of the groove, machining the visible material to make its size 0.5-1 mm smaller than the groove, and setting a mounting hole at a preset position;

[0021] S3. Install the sealing strip into the assembly groove and connect the ends together, overlap the joints at an angle and seal them with glue;

[0022] S4, assemble the visual material into the groove and fix it through the first connecting piece, ensure that the first connecting piece is screwed in the same number of turns and the compression amount of the sealing structure is 3-5mm, and fill and seal the joint between the visual material and the frame 11.

[0023] Compared with the prior art, the partially transparent visual RTM mold and manufacturing method described in the present invention have the following beneficial effects: 1) The visible area formed by the transparent material accounts for a high proportion, and the injection operation is regulated based on the observed resin conditions, so the product yield rate is high; 2) The visible material and frame of the upper mold are evenly distributed, there is no temperature gradient in the mold, the consistency of the curing process is good, and the product quality is more stable; 3) Good sealing can be achieved by filling the gaps around the visible material and setting the sealing structure. At the same time, the upper mold structure is optimized to ensure that its structural strength can meet the RTM process requirements and the mold has a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an overall schematic diagram of a partially transparent and visualized RTM mold according to an embodiment of the present invention;

[0025] Figure 2 for Figure 1 A partial enlarged view of the middle A;

[0026] Figure 3 Another viewing angle of the partially transparent visualized RTM mold according to an embodiment of the present invention;

[0027] Figure 4 It is a structural schematic diagram of the upper mold according to an embodiment of the present invention;

[0028] Figure 5 It is an assembly cross-sectional view of the visual material according to an embodiment of the present invention;

[0029] Figure 6 is a cross-sectional schematic diagram of a sealing structure according to an embodiment of the present invention;

[0030] Figure 7 This is a uniform load diagram of the partially transparent visual RTM mold of the present invention at 1 MPa;

[0031] Figure 8 The overall displacement cloud diagram of the partially transparent visualized RTM mold of the present invention under 1 MPa;

[0032] Fig. 9 It is a displacement cloud diagram of the upper mold frame in the visualized RTM mold of the present invention under 1 MPa;

[0033] Fig.10 This is a displacement cloud diagram of the visible area in the visualized RTM mold described in the present invention under 1 MPa.

[0034] Description of reference numerals:

[0035] 1-upper mold; 11-frame; 12-reinforcement rib; 13-first reinforcement rib; 14-second reinforcement rib; 15-opening; 2-visible material; 21-first connecting piece; 22-sealing structure; 3-lower mold; 4-glue injection port; 5-second connecting piece; 6-sealing piece. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. The technical features of the embodiments of the present invention can be combined with each other without conflict.

[0037] It should be noted that all the terms used in the present invention for directional and positional indications, such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "inside", "outside", "top", "lower", "lateral", "longitudinal", "center", etc., are only used to explain the relative positional relationship and connection status between the components in a certain state (as shown in the accompanying drawings), and are only for the convenience of describing the present invention, rather than requiring the present invention to be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features.

[0038] In the description of the present invention, 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; 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 according to specific circumstances.

[0039] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0040] The RTM process is a molding method that injects resin into a closed mold and allows it to infiltrate reinforcing materials (such as fiber cloth, fiber felt, etc.) to manufacture composite materials. It has the advantages of low cost, fast molding speed, good product quality, low environmental pollution, and is suitable for manufacturing large and complex structural components. It has broad application prospects in the fields of aerospace, transportation, etc. In order to achieve controllability of the process, the existing RTM mold uses a whole piece of glass as a visual window, but due to the different thermal conductivity between the glass and the metal mold, the temperature distribution of the mold is uneven, especially during the curing process, which is extremely unfavorable for the quality control of the final product; because the glass is connected to the upper mold by screws and its own toughness is relatively low, it will deform or even break when assembled too tightly, and if the assembly is loose, there will be a problem of loose sealing. For this reason, the applicant proposes the following technical solution:

[0041] like Figure 1-6 As shown, a partially transparent visual RTM mold includes an upper mold 1 and a lower mold 3, wherein the upper mold 1 and the lower mold 3 are fixed by a second connecting member 5 and cooperate with each other to form a cavity; the upper mold 1 includes a frame 11, and a plurality of grooves are arranged on the frame 11 for limiting the assembly of a visual material 2, and an opening 15 is arranged in the groove, and the visual material 2 can block the opening 15; the visual material 2 is connected to the frame 11 through a first connecting member 21, and there are a plurality of first connecting members 21 and they are evenly distributed along the periphery of the visual material 2, and a sealing structure 22 is arranged on the peripheral side of the visual material 2, and the sealing structure 22 is limitedly assembled to the groove.

[0042] This arrangement can realize the visualization of the RTM mold, and at the same time, the upper mold 1 used to form the cavity is evenly arranged with the visible material 2 and the frame 11, ensuring uniform temperature conduction and excellent quality of the final product; at the same time, the visible material 2 is a PC board, which is easy to process and open, and will not break due to improper application of force during the assembly process. The second connecting member 5 is a bolt, and its specific structure is the prior art.

[0043] As an example of the present invention, a seal 6 is provided between the upper mold 1 and the lower mold 3 to seal the assembly therebetween. The seal 6 is an annular sealing ring, and its specific structure and assembly relationship are prior art, which will not be described in detail here.

[0044] Preferably, there is a gap of 0.5-1.0 mm between the four sides of the visible material 2 and the groove, and the sealing structure 22 is a sealing strip connected end to end, and the sealing strip is located between the openings 15 of the first connector 21. This arrangement can create a gap between the visible material 2 and the groove, and the gap is filled to achieve primary sealing; then the sealing structure 22 is used to perform secondary sealing and isolate the outside air, and the two cooperate with each other to meet the sealing requirements of the PC board as the visible material 2.

[0045] As an example of the present invention, an assembly groove is provided on the groove, the longitudinal section of one end of the sealing strip is rectangular and is limitedly assembled to the assembly groove, and the cross-section of the other end of the sealing strip is an arc and a cavity is provided inside for contacting with the visual material 2. This arrangement can be squeezed and deformed under the action of the first connecting member 21, so as to fit tightly with the visual material, and the other side of the sealing strip is assembled through the limiting groove to prevent the position of the sealing structure 22 from loosening and slipping. Preferably, the widths of the assembly groove and the sealing strip are L1 and L2, respectively, where L1=L2+D and the value of D is 2-6mm. This arrangement can ensure that the sealing structure itself has a good compression space.

[0046] Preferably, the two ends of the sealing strip are overlapped by an oblique joint method, and the two ends of the cavity are sealed by a sealant at the joint, for example, a 20-30mm deep polyurethane sealant is applied to the hollow area of ​​the sealing ring to ensure the sealing after the mold is closed. This setting can ensure that there is always air in the cavity of the sealing strip, and it will not be over-extruded, and the sealing effect is good.

[0047] Preferably, the first connecting member 21 is a countersunk bolt, and a matching hole is provided on the groove. The countersunk bolt passes through the visual material 2 and is connected to the matching hole. The visual material 2 and the side of the countersunk bolt close to the lower mold 3 are in the same plane, and the visual material 2 and at least part of the frame 11 are in the same plane. This setting can ensure that the inner surface of the cavity is smooth and flat, and the final product quality is good. Preferably, the minimum spacing between the first connecting members 21 is 50-100mm.

[0048] Preferably, reinforcing ribs 12 are provided on the frame 11, and the reinforcing ribs 12 are located in the middle of the opening 15. Compared with metal materials, visual materials 2 such as PC boards have good toughness but poor strength, and are easily bent and deformed when subjected to a pressure shock of 1 MPa during the RMT process. This arrangement can support the visual material 2, especially the PC board, to prevent it from excessive deformation or even breakage. As an example of the present invention, the frame 11 is made of metal materials such as iron and steel, which can take into account that the mold has good rigidity and is of moderate quality for easy operation.

[0049] As an example of the present invention, the frame 11 is provided with a first reinforcing rib 13 and a second reinforcing rib 14 on a side away from the visible material 2, the first reinforcing rib 13 has a plurality of ribs and is arranged in parallel with each other, the second reinforcing rib 14 has a plurality of ribs and is arranged in parallel with each other, the first reinforcing rib 13 and the second reinforcing rib 14 are vertically connected to each other and are integrally formed with the frame 11. This arrangement can strengthen the structure of the upper mold 1 having a plurality of openings 15, so that the visible area formed by the visible material 2 has a high proportion in the upper mold 1, and the injection process can be better observed.

[0050] As an example of the present invention, the length of a single visual material 2 is 50mm-300mm, the width is 50-300mm, the minimum spacing between two adjacent visual materials 2 is 60mm, and the thickness of the visual material 2 is at least 20mm. As an example of the present invention, the height of the upper mold 1 and the lower mold 3 is 2.2m, the width is 1.4m, the thickness of the upper mold 1 and the lower mold 3 is 50mm, the thickness of the cavity is 16mm, the thickness of the reinforcing rib is 30mm, the height is 60mm, the spacing between the reinforcing ribs is 350mm, and a total of 15 grooves are arranged on the upper mold 1, the size of the grooves is 350mm*350mm, and the depth is 20-30mm.

[0051] The local transparent visualization RTM mold was simulated and checked, and the results are shown in Figure 7-10 According to the results, the comprehensive average deformation of the partially transparent visualized RTM mold under a pressure of 1 MPa is 2.091 mm, the deformation of the metal reinforcement rib is 0.287 mm, the maximum deformation of the PC board is 2.091 mm, and the overall rigidity meets the use requirements.

[0052] The fiber preform is laid into the cavity of the partially transparent visual RTM mold. After the mold is closed, the resin is injected through each injection port 4, the resin infiltration and flow in the fiber preform is observed, and the injection pressure and other process parameters are regulated. The resin flow process in the cavity can be clearly observed through the visible area, and the state of fiber penetration can be clearly seen, the effect is good, and no resin leakage occurs during the injection process, proving that the transparent window sealing effect is good; after 50 batches of production using the partially transparent visual RTM mold described in this application, no abnormalities are found and it can still be used normally. The yield rate of the product in this process is 96%; under the same conditions, after 36 batches of production using the existing visual mold, the mold's airtightness has problems and cannot be normal. At the same time, for products that are sensitive to curing temperature, the yield rate is significantly lower than that of this application.

[0053] The present application also provides a method for manufacturing a partially transparent and visualized RTM mold, comprising:

[0054] S1. Simulate and check the designed local visual RTM mold to ensure that it meets the use requirements under extreme pressure;

[0055] S2, machining the upper die 1 to form a groove and an opening 15, setting a mounting groove on the outer peripheral side of the groove, machining the visual material 2 to make its size 0.5-1 mm smaller than the groove, and setting a mounting hole at a preset position;

[0056] S3, installing the sealing structure 22 into the assembly groove and connecting them end to end, making an oblique overlap at the interface and sealing it with glue;

[0057] S4. Assemble the visual material 2 into the groove and fix it through the first connecting piece 21, ensure that the first connecting piece 21 is screwed in the same number of turns and the compression amount of the sealing structure 22 is 3-5mm, fill and seal the joint between the visual material 2 and the frame 11, such as resin putty, structural adhesive or sealant.

[0058] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A partially transparent visual RTM mold, comprising an upper mold (1) and a lower mold (3), wherein the upper mold (1) and the lower mold (3) are fixed by a second connecting member (5) and cooperate with each other to form a mold cavity, characterized in that: The upper mold (1) comprises a frame (11), the frame (11) being provided with a plurality of grooves for limiting the assembly of a visual material (2), the grooves being provided with openings (15), and the visual material (2) being capable of blocking the openings (15); the visual material (2) and the frame (11) being connected via a first connecting member (21), the first connecting member (21) being provided in plurality and evenly distributed along the periphery of the visual material (2), a sealing structure (22) being provided on the periphery of the visual material (2), and the sealing structure (22) being installed in the grooves.

2. The partially transparent visual RTM mold according to claim 1, characterized in that: There is a gap of 0.5-1.0 mm between the four sides of the visible material (2) and the groove, and the sealing structure (22) is a sealing strip connected end to end, and the sealing strip is located between the openings (15) of the first connecting member (21).

3. The partially transparent visual RTM mold according to claim 2, characterized in that: A cavity is arranged in the sealing strip and an oblique overlap is performed at the interface and sealed with glue. An assembly groove is arranged in the groove to accommodate the sealing strip. The widths of the assembly groove and the sealing strip are L1 and L2 respectively, wherein L1=L2+D and the value of D is 2-6mm.

4. The partially transparent visual RTM mold according to claim 1, characterized in that: A reinforcing rib (12) is provided in the middle of the opening (15) for supporting the flat plate-shaped visible material (2).

5. The partially transparent visual RTM mold according to claim 4, characterized in that: The frame (11) is provided with a first reinforcing rib (13) and a second reinforcing rib (14) on a side away from the visible material (2); the first reinforcing ribs (13) are provided in plurality and are arranged in parallel with each other; the second reinforcing ribs (14) are provided in plurality and are arranged in parallel with each other; the first reinforcing ribs (13) and the second reinforcing ribs (14) are vertically connected to each other and are integrally formed with the frame (11).

6. The partially transparent visual RTM mold according to claim 1, characterized in that: The first connecting member (21) is a countersunk bolt, a matching hole is provided on the groove, the countersunk bolt passes through the visible material (2) and is connected to the matching hole, the visible material (2) and a side of the countersunk bolt close to the lower mold (3) are in the same plane, and the visible material (2) and at least a portion of the frame (11) are in the same plane.

7. The partially transparent visual RTM mold according to claim 1, characterized in that: The length of a single visible material (2) is 50 mm to 300 mm, the width is 50 mm to 300 mm, the minimum spacing between two adjacent visible materials (2) is 60 mm, and the thickness of the visible material (2) is at least 20 mm.

8. The partially transparent visual RTM mold according to claim 1, characterized in that: A sealing member (6) is provided between the upper die (1) and the lower die (3); the sealing member (6) is annular and is located on the outer peripheral side of the cavity; and the upper die (1) and / or the lower die (3) are provided with a plurality of glue injection ports (4).

9. The method for manufacturing a partially transparent and visual RTM mold according to any one of claims 1 to 8, characterized in that: include: S1. Simulate and check the designed local visual RTM mold to ensure that it meets the use requirements under extreme pressure; S2, machining the upper die (1) to form a groove and an opening (15), opening a mounting groove on the outer peripheral side of the groove, machining the visible material (2) to make its size 0.5-1.0 mm smaller than the groove, and setting a mounting hole at a preset position; S3, installing the sealing structure (22) into the assembly groove and connecting the end to the end, making an oblique overlap at the interface and sealing it with glue; S4, assembling the visual material (2) into the groove and fixing it through the first connecting member (21), ensuring that the number of turns of the first connecting member (21) is the same and the compression amount of the sealing structure (22) is 3-5 mm, and filling and sealing the joint between the visual material (2) and the frame (11).

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