A locally transparent visual RTM mold and manufacturing method

Abstract

The present invention provides a locally transparent visual RTM mold and a manufacturing method, which relates to the technical field of composite material forming. The locally transparent visual RTM mold includes an upper mold and a lower mold. The upper mold and the lower mold are fixed through a second connecting member and cooperate with each other to form a cavity. The upper mold includes a frame, and a plurality of grooves are provided on the frame for limiting and assembling a visual material. An opening is provided in the groove, and the visual material can block the opening. The visual material is connected to the frame through a first connecting member. There are a plurality of first connecting members and they are evenly distributed along the outer periphery of the visual material. A sealing structure is provided on the outer peripheral side of the visual material, and the sealing structure is installed in the groove. By optimizing the upper mold, the present invention ensures that its structural strength can meet the requirements of the RTM process. At the same time, the filling of the gaps around the visual material and the setting of the sealing structure can achieve good sealing, the mold has a long service life, and the product quality is good.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material molding, and more particularly, to a locally transparent visual RTM mold and a manufacturing method thereof. Background Art

[0002] The Resin Transfer Molding (RTM) process is an advanced process for manufacturing high-performance fiber-reinforced composites. In a prefabricated cavity that meets the process dimensions, a fiber-reinforced material preform calculated according to the design requirements is laid, and then a special resin system is injected into the closed cavity by an injection device within a certain pressure range. After the resin infiltrates the reinforcement and cures, high-performance composites are prepared. It has the advantages of low cost, fast molding speed, good product quality, little environmental pollution, and the ability to manufacture large and complex structural components, so it has been widely used in the aerospace and transportation fields.

[0003] Currently, during the resin sheet molding process, a molding cavity is provided by the clamping of the upper and lower molds, and the molding effect is stable. However, during the molding process, since both the upper and lower molds are opaque structures, it is impossible to directly judge the flow front of the resin at different times during the injection process, nor can it be judged whether there are situations such as uneven flow, bubble agglomeration, and dry spots at a certain place, resulting in a high defect rate of the final product.

[0004] For this reason, Chinese Patent No. 201921717534.0 discloses a visual RTM molding mold, including a lower mold and an upper mold. The upper mold includes a frame and a glass plate. The glass plate is attached to the lower mold to close the opening of the concave area on the lower mold, thereby forming a cavity for molding the resin. The frame is used to provide a pressing force for attaching to the lower mold by connecting with the lower mold. This solution realizes the visualization of the resin flow in the cavity by splitting the upper mold into a transparent part.

[0005] In addition, Chinese Patent No. 201710356088.4 discloses a visual RTM mold for steplessly adjusting the thickness of a composite material sheet. A toughened glass is embedded in the upper template; the lower template is fixed on the frame by a fixing member. A sliding member is provided in the fixing member, and a linkage member is fixed to the bottom surface of the sliding member. A cavity adjusting mechanism for driving the linkage member and the sliding member to move up and down is installed thereon; injection holes and discharge holes are opened on the sliding member and the linkage member; a flow channel is opened around the upper end of the middle through hole leading to the closed cavity in the fixing member and is communicated with the injection hole. This solution uses toughened glass as an observation window on the upper template to observe the resin filling and flowing.

[0006] However, in order to ensure that the mold meets the strength and stiffness requirements of the RTM process, glass is used as the visible material. Due to the relatively low toughness of glass, it may crack or deform under the pressure during resin injection and the temperature change during the curing process in the RTM process. In addition, due to the different thermal conductivity properties of the glass plate and the metal mold, the temperature distribution of the formed body in the mold during curing is uneven, which affects the final product quality. Moreover, since the glass plate and the upper mold are fixed by screws, the sealing performance at the connection is poor and the flatness is difficult to guarantee. Summary of the Invention

[0007] The problem solved by the present invention is that the existing visible RTM molds have deficiencies such as short service life and unsatisfactory quality of the formed bodies prepared.

[0008] To solve the above problems, the present invention provides a locally transparent and visual RTM mold, including an upper mold and a lower mold. The upper mold and the lower mold are fixed by a second connecting member and cooperate with each other to form a cavity. The upper mold includes a frame, and a plurality of grooves are provided on the frame for limiting and assembling the visible material. The grooves are provided with openings, and the visible material can block the openings. The visible material and the frame are connected by a first connecting member. There are a plurality of first connecting members and they are evenly distributed along the outer periphery of the visible material. A sealing structure is provided on the outer peripheral side of the visible material, and the sealing structure is installed in the grooves.

[0009] This setting can realize the visualization of the RTM mold. At the same time, the upper mold for forming the cavity of the upper mold is composed of a uniform arrangement of the visible material and the frame, ensuring uniform temperature conduction and excellent quality of the final product. At the same time, the visible material is a PC board, which has little difficulty in processing and opening holes itself, and will not crack due to improper application of force during the assembly process.

[0010] Preferably, there is a gap of 0.5 - 1.0 mm between the periphery of the visible material and the grooves. The sealing structure is a sealing strip connected end to end, and the sealing strip is located between the first connecting member and the opening.

[0011] This setting can create a gap between the visible material and the grooves, and the initial sealing is achieved by filling the gap. Then, the secondary sealing is carried out through the sealing structure to isolate the outside air. The two cooperate with each other to meet the sealing requirements with the PC board as the visible material.

[0012] Preferably, a cavity is provided inside the sealing strip, and mitered lap joint is performed at the interface and sealed with glue. 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, where L1 = L2 + D and the value of D is 2 - 6 mm. This setting can ensure that the sealing structure itself has good compression space, and at the same time, there is always air in the cavity of the sealing strip, which will not be overly squeezed, and the sealing effect is good.

[0013] Preferably, a reinforcing rib is provided at the middle position of the opening for supporting the flat visual material. Compared with metal materials, visual materials such as PC boards have good toughness but poor strength, and are prone to bending and deformation under a pressure impact of 1 MPa in the RMT process. This setting can support the visual material, especially PC boards, and prevent excessive deformation or even fracture.

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

[0015] Preferably, the first connecting member is a countersunk head bolt, and a mating hole is provided on the groove. The countersunk head bolt passes through the visual material and is connected to the mating hole. The side of the visual material and the countersunk head bolt close to the lower mold are on the same plane, and the visual material and at least part of the frame are on the same plane.

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

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

[0018] The present invention also provides a manufacturing method for a locally transparent visual RTM mold, including:

[0019] S1. Perform simulation verification on the designed locally visual RTM mold to ensure that it meets the usage requirements under the ultimate pressure;

[0020] S2. Machine-process the upper mold to form a groove and an opening, machine an assembly groove on the outer peripheral side of the groove, machine the visible material so that its size is 0.5 - 1 mm smaller than the groove, and set installation holes at preset positions;

[0021] S3. Install the sealing strip into the assembly groove and make its head and tail connected. Make a miter joint at the interface and seal it with glue;

[0022] S4. Assemble the visible material into the groove and fix it with the first connecting piece, ensuring that the number of screwing-in turns of the first connecting piece is the same and the compression amount of the sealing structure is 3 - 5 mm. Fill and seal the joint between the visible material and the frame 11.

[0023] Compared with the prior art, the local transparent visualization RTM mold and manufacturing method of the present invention have the following beneficial effects: 1) The proportion of the visible area formed by the transparent material is high. The injection molding operation is regulated based on the observed resin condition, and the product qualification rate is high; 2) The visible material of the upper mold and the frame 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 through the filling of the gaps around the visible material and the setting of the sealing structure. At the same time, the structure of the upper mold is optimized to ensure that its structural strength can meet the requirements of the RTM process, and the mold service life is long. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the overall schematic diagram of the local transparent visualization RTM mold described in the embodiment of the present invention;

[0025] Figure 2 is Figure 1 the partial enlarged view at A in

[0026] Figure 3 is the view from another angle of the local transparent visualization RTM mold described in the embodiment of the present invention;

[0027] Figure 4 is the structural schematic diagram of the upper mold described in the embodiment of the present invention;

[0028] Figure 5 is the assembly cross-sectional view of the visible material described in the embodiment of the present invention;

[0029] Figure 6 is the cross-sectional schematic diagram of the sealing structure described in the embodiment of the present invention;

[0030] Figure 7 is the uniform load diagram of the local transparent visualization RTM mold of the present invention under 1 MPa;

[0031] Figure 8 is the overall displacement nephogram of the local transparent visualization RTM mold of the present invention under 1 MPa;

[0032] Figure 9 This is the displacement nephogram of the upper die frame in the visual RTM mold of the present invention under 1 MPa;

[0033] Figure 10 This is the displacement nephogram of the visual area in the visual RTM mold of the present invention under 1 MPa.

[0034] Explanation of reference numerals:

[0035] 1 - upper die; 11 - frame; 12 - reinforcing rib; 13 - first reinforcing rib; 14 - second reinforcing rib; 15 - opening; 2 - visual material; 21 - first connecting member; 22 - sealing structure; 3 - lower die; 4 - glue injection port; 5 - second connecting member; 6 - seal. Detailed implementation manners

[0036] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is given with reference to the accompanying drawings. On the premise of no conflict, the technical features of the embodiments of the present invention can be combined with each other.

[0037] It should be noted that all terms indicating directions and positions in the present invention, such as: "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inner", "outer", "top", "bottom", "lateral", "longitudinal", "center", etc., are only used to explain the relative positional relationship and connection situation between components in a certain specific 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. Therefore, it cannot be understood as a limitation to the present invention. In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features.

[0038] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" 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 directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[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 Figures 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 die 1 and the lower die 3 for sealing the assembly therebetween. The seal 6 is an annular sealing ring, and its specific structure and assembly relationship are prior arts and will not be elaborated herein.

[0044] Preferably, there is a gap of 0.5 - 1.0 mm between the periphery of the visual material 2 and the groove. The sealing structure 22 is a sealing strip connected end to end, and the sealing strip is located between the opening 15 of the first connector 21. This setting can create a gap between the visual material 2 and the groove, and the initial sealing is achieved by filling the gap; then the secondary sealing is carried out through the sealing structure 22 to isolate the outside air, and the two cooperate with each other to meet the sealing requirements for the PC board as the visual 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 into the assembly groove, and the cross section of the other end of the sealing strip is arc-shaped and a cavity is provided inside for abutting against the visual material 2. This setting can be squeezed and deformed under the action of the first connector 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 - 6 mm. This setting can ensure that the sealing structure itself has a good compression space.

[0046] Preferably, the two ends of the sealing strip adopt the beveled joint method, and sealant is used to seal both ends of the cavity at the butt joint. For example, polyurethane sealant with a depth of 20 - 30 mm is injected into the hollow area of the sealing ring to ensure the sealing performance after mold closing. This setting can ensure that there is always air in the cavity of the sealing strip, and it will not be over-squeezed, and the sealing effect is good.

[0047] Preferably, the first connector 21 is a countersunk head bolt, a mating hole is provided on the groove, the countersunk head bolt passes through the visual material 2 and is connected to the mating hole, the side of the visual material 2 close to the lower die 3 and the countersunk head bolt 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 has good quality. Preferably, the minimum distance between the first connectors 21 is 50 - 100 mm.

[0048] Preferably, reinforcing ribs 12 are provided on the frame 11, and the reinforcing ribs 12 are located at the middle position of the opening 15. Compared with metal materials, the visual material 2 such as PC board has good toughness but poor strength, and is prone to bending and deformation under a pressure impact of 1 MPa in the RMT process. This setting can support the visual material 2, especially the PC board, and prevent it from being overly deformed or even fractured. 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 the good rigidity of the mold and is of moderate quality and convenient for operation.

[0049] As an example of the present invention, first reinforcing ribs 13 and second reinforcing ribs 14 are provided on the side of the frame 11 away from the visual material 2. There are multiple first reinforcing ribs 13 arranged in parallel with each other, and there are multiple second reinforcing ribs 14 arranged in parallel with each other. The first reinforcing ribs 13 and the second reinforcing ribs 14 are perpendicularly connected to each other and are integrally formed with the frame 11. This setting can strengthen the structure of the upper mold 1 with multiple openings 15, so that the proportion of the visual area formed by the visual material 2 in the upper mold 1 is high, 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 50 mm - 300 mm, the width is 50 - 300 mm, the minimum distance between two adjacent visual materials 2 is 60 mm, and the thickness of the visual material 2 is at least 20 mm. As an example of the present invention, the height of the upper mold 1 and the lower mold 3 is 2.2 m, the width is 1.4 m, the thickness of the upper mold 1 and the lower mold 3 is 50 mm, the cavity thickness is 16 mm, the reinforcing rib thickness is 30 mm, the height is 60 mm, the reinforcing rib spacing is 350 mm, and a total of 15 grooves are provided on the upper mold 1. The size of the grooves is 350 mm * 350 mm, and the depth is 20 - 30 mm.

[0051] The local transparent visual RTM mold is simulated and checked, and the results are shown in Figures 7-10 the figure. According to the results, the comprehensive average deformation of the local transparent visual RTM mold under a pressure of 1 MPa is 2.091 mm, the deformation of the metal reinforcing 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] Place the fiber preform into the cavity of the local transparent visualization RTM mold. After closing the mold, inject resin through each resin injection port 4, observe the infiltration and flow of the resin in the fiber preform, and adjust process parameters such as the injection pressure. Through the visible area, the flow process of the resin in the cavity can be clearly observed, the state of fiber penetration can be clearly seen, and the effect is good. Moreover, no resin leakage occurs during the injection process, proving that the sealing effect of the transparent window is good. After using the local transparent visualization RTM mold of the present application to produce 50 batches, no abnormalities are found and it can still be used normally. During this process, the qualified rate of the products is 96%. Under the same conditions, after using the existing visible mold to produce 36 batches, the airtightness of the mold has problems and it cannot be used normally. At the same time, for products sensitive to curing temperature, the qualified rate is significantly lower than that of the present application.

[0053] The present application also provides a manufacturing method for a local transparent visualization RTM mold, including:

[0054] S1. Perform simulation verification on the designed local visualization RTM mold to ensure that it meets the usage requirements under the ultimate pressure;

[0055] S2. Machine the upper mold 1 to form a groove and an opening 15, set an assembly groove on the outer peripheral side of the groove, machine the visible material 2 so that its size is 0.5 - 1 mm smaller than the groove, and set installation holes at preset positions;

[0056] S3. Install the sealing structure 22 into the assembly groove and make its head and tail connected. Lap the bevel at the interface and seal it with glue;

[0057] S4. Assemble the visible material 2 into the groove and fix it with the first connector 21, ensuring that the number of screwing-in turns of the first connector 21 is the same and the compression amount of the sealing structure 22 is 3 - 5 mm. Fill and seal the joint between the visible material 2 and the frame 11, such as resin putty, structural glue or sealant, etc.

[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 should 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) is provided with a plurality of grooves for limiting the assembly of the visual material (2), the grooves are provided with openings (15), and the visual material (2) is capable of blocking the openings (15); the visual material (2) is connected to the frame (11) via a first connecting member (21), there are a plurality of first connecting members (21) and they are evenly distributed along the periphery of the visual material (2), a sealing structure (22) is provided on the periphery of the visual material (2), and the sealing structure (22) is installed in the grooves; 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 first connecting member (21) and the opening (15); A cavity is provided in the sealing strip and an oblique overlap is performed at the interface and sealed with glue. 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 2-6 mm. A reinforcing rib (12) is provided in the middle of the opening (15) for supporting the flat plate-shaped visible material (2).

2. The partially transparent visual RTM mold according to claim 1, 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).

3. 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.

4. 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.

5. 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).

6. The method for manufacturing a partially transparent and visual RTM mold according to any one of claims 1 to 5, 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).

Images