A molding process suitable for composite material tubular beams with large thickness

Abstract

This invention discloses a molding process suitable for composite material tube beams with significant thickness, comprising: S1, providing a tubular mandrel; S2, fitting an inner expansion bag onto the surface of the mandrel; S3, laying composite prepreg on the inner expansion bag according to the design of the composite material tube beam, while utilizing the strength of the mandrel itself to create a vacuum bag on the mandrel, and pre-compacting the layers by vacuuming; vacuum pre-compacting is performed every 4-8 layers; during prepreg laying, the layers near both ends of the mandrel are designed as missing layers, and pads are placed on the inner expansion bag near the end of the mandrel; the pads and the missing layers are matched in shape; S4, an outer mold is tightly attached to the outside of the preform and connected and fixed to a sealing plate; S5, inflating the inner expansion bag to create pressure on the preform, and then sending it into a curing oven for curing; S6, removing the outer mold, mandrel, and inner expansion bag, and machining to obtain the finished part. This invention can produce composite material tube beams with significant thickness and good quality.

Description

Technical Field

[0001] This invention relates to the field of composite material molding technology, and more specifically to a molding process suitable for composite material tube beams with large thickness. Background Technology

[0002] Composite material tube beams / shafts are now widely used in various fields such as aerospace, automotive, and industry. In particular, fiber composite material tube beams (shafts) have significant advantages over metal tube shafts due to their "lightweight and high strength" characteristics.

[0003] For certain applications requiring lightweight yet high-strength construction, fiber-reinforced composite tube beams (shafts) offer unparalleled advantages. Currently, for thicker composite tube beams (shafts), filament winding and internal expansion molding are commonly used methods. Although internal expansion molding is more expensive than filament winding, the resulting products exhibit higher internal quality (porosity, delamination).

[0004] Therefore, the mainstream method is still to use the internal expansion molding process. However, for composite material tube beams with a large wall thickness (≥8mm), the internal expansion molding process will face two problems that need to be solved: (1) The material of the core mold is relatively soft and easily deformed; and because the core mold itself is relatively soft, it cannot be vacuum pre-compacted multiple times, resulting in insufficient density between the composite prepreg layers; (2) The thickness of the manufactured composite material tube beam is relatively large, and the prepreg at its end will form a step when it is laid. During subsequent pressure curing, axial extrusion force will be generated, causing the prepreg to be squeezed and deformed towards the middle, ultimately affecting the quality of the finished product. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems existing in the current internal expansion molding method for manufacturing composite tube beams with large wall thicknesses. This invention designs a new molding process suitable for composite tube beams with large thicknesses, solving many problems faced by the current internal expansion molding method in manufacturing composite tube beams with large wall thicknesses.

[0006] This invention is achieved through the following technical solution:

[0007] A forming process suitable for composite material tubular beams with large thickness, characterized in that the process includes the following steps:

[0008] S1. Provide a tubular core mold;

[0009] Wherein: the core mold has the strength to meet the requirements of vacuum pre-extraction at room temperature, and has the ability to soften and shrink during heating and curing to meet the requirements of subsequent core extraction and demolding;

[0010] S2. An inner expansion bag is fitted onto the surface of the core mold;

[0011] S3. On the inner expansion bag, composite prepreg is laid according to the design of composite tube beam, and pre-compacted to form a composite tube beam prefabricated body.

[0012] Specifically: when laying the prepreg, the layers near both ends of the core mold are designed as missing layers, and a pad is provided on the inner expansion bag near the end of the core mold; the pad and the shape of the missing layer are matched; specifically, the pad can be fixed by pressure-sensitive tape;

[0013] S4. After the prepreg is laid, an outer mold is attached tightly to the outside of the composite material tube beam precast body and the outer mold is fixed.

[0014] S5. Inflate the inner expansion bag with air so that the inner expansion bag exerts pressure on the composite material tube beam preform, and then send the whole thing into the curing oven for curing.

[0015] S6. After curing, remove the outer mold, extract the tubular core mold and inner expansion bag, and machine to obtain the part (that is, to make a composite material tube beam or tube shaft with a large thickness).

[0016] Similarly, the method provided by this invention is applicable to the molding and manufacturing of composite material tubes and shafts with large thicknesses.

[0017] Specifically, in step S3 above, the rigidity of the core mold itself can be used to make a vacuum bag on the core mold, which can pre-vacuum the prepreg layer, making the prepreg layers more compact and improving the quality of the final product.

[0018] Specifically, in step S5 above, the inner expansion bag is pressurized by inflation to compress the composite material tube beam preform. The preform is located between the inner expansion bag and the outer mold, and is compacted by the pressure generated by the inner expansion bag.

[0019] Specifically, in step S6 above, the core mold shrinks when heated in the curing oven, making it easy to demold; that is, the UPVC core mold softens when heated, reducing its diameter, and can be removed from the mold after curing.

[0020] Furthermore, a molding process suitable for composite material tube beams with larger thicknesses is provided: the core mold mentioned in step S1 is made of UPVC pipe.

[0021] Furthermore, a molding process suitable for composite material tube beams with large thickness: Step S2, sealing plates are provided at both ends of the core mold, and air inlet and air outlet are respectively provided on the sealing plates;

[0022] When the inner expansion bag is fitted onto the surface of the core mold, there is a margin at both ends of the core mold, and the margin of the inner expansion bag is sealed to the sealing plate.

[0023] Furthermore, a molding process suitable for composite material tube beams with greater thickness: Step S4, the outer mold is fixedly connected to the sealing plates at both ends of the core mold by sealing bolts.

[0024] Furthermore, a molding process suitable for composite material tube beams with larger thicknesses is provided: Step S4, the outer mold is also provided with a sealing device to ensure the airtightness of the inner expansion bag; the sealing device is located between the outer mold and the sealing plate; the remaining inner expansion bag is sealed and connected to the sealing device.

[0025] Specifically, the sealing plate is connected to the outer mold and has no direct relationship with the core mold; the sealing plate, the outer mold, and the inner expansion bag form a sealed space, which is pressurized through the inflation port and depressurized through the exhaust port.

[0026] Furthermore, a molding process suitable for composite material tube beams with relatively large thicknesses is provided: Step S5, inflating the inner expansion bag through the inflation port, with the pressure generated being 3–25 bar. Specifically, the inflation causes the inner expansion bag to exert a pressure of 3–25 bar on the composite material preform.

[0027] Furthermore, a molding process suitable for composite material tube beams with larger thickness: Step S3, after laying 4 to 8 layers of prepreg, a vacuum bag is made on the mandrel, and the prepreg layers are pre-compacted by vacuuming.

[0028] Specifically, in this step, the inner expansion bag can be pre-vacuumed before the prepreg is laid. The purpose is to make the inner expansion bag fit the surface of the mandrel so that the prepreg can be laid.

[0029] Specifically, when laying 4 to 8 layers of prepreg, vacuum bags are made on the outside of the layer (i.e., on the core mold) to vacuum and pre-compact the prepreg layer according to the laying and compaction requirements. After multiple laying and pre-compaction, a composite material tube beam prefabrication is formed.

[0030] Specifically, by utilizing the rigidity of the core mold itself, vacuum bags can be made on the core mold to pre-compact the layup by vacuuming.

[0031] Furthermore, a molding process suitable for composite material tube beams with large thickness: in step S3, one end of the pad block is matched with the shape of the layer, and the other end is flush with the end of the core mold.

[0032] Furthermore, a molding process suitable for composite material tube beams with larger thicknesses is provided: the pad in step S3 is a silicone rubber pad.

[0033] Furthermore, a molding process suitable for composite material tube beams with greater thickness is as follows: Step S6, the missing layers during the laying process are processed and cut flat to obtain composite material tube beams with greater thickness.

[0034] In the molding process of composite material tube beams with large thickness provided by the present invention: (1) The inner core mold is made of UPVC pipe, which can meet the strength requirements after vacuum pre-extraction under room temperature conditions; and can meet the requirements of heat softening and shrinkage during curing in the curing oven, and can be removed from the mold. (2) After the end prepreg is laid into a layer (slope) transition, a silicone rubber pad is used to cooperate with the layer slope and fit flat; the slope of the silicone rubber pad is consistent with the slope of the prepreg layer area, and the slope length is 2 to 3 times the thickness of the prepreg layer; after the silicone rubber pad is fitted with the layer, its end is flush with the sealing surface of the outer mold; after the silicone rubber pad is fitted with the prepreg layer area, its thickness is equal to the theoretical thickness of the prepreg layer.

[0035] Beneficial effects of this invention:

[0036] (1) This invention provides a molding process suitable for composite tube beams with large thickness. By using a mandrel for internal expansion molding, it solves the problems of dense laying of composite tube beams with large wall thickness and axial prepreg extrusion. It can produce composite tube beams with large thickness and good quality (no delamination, wrinkles, smooth outer surface, and uniform and smooth inner surface).

[0037] (2) In the molding process provided by the present invention, by designing the prepreg layer at the end as a layer-dropping method and setting up a pad that matches the layer-dropping method, the existing internal expansion molding process is avoided. This process can easily lead to the formation of steps when the prepreg is laid at the end, which will generate axial extrusion force during subsequent pressure curing, thereby causing the prepreg to be squeezed and deformed towards the middle, ultimately affecting the quality of the finished product. The molding process of the present invention effectively improves the quality of the product. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This invention provides a molding process diagram for composite material tube beams with large thickness.

[0040] The markings in the diagram are: 1 core mold (tubular), 2 inner expansion bag, 3 composite material tube beam precast body, 4 pad block, 5 outer mold, 6 sealing bolt, 7 sealing device, 8 tear-off layer, 1-1 sealing plate, 1-2 air inlet, 1-3 exhaust outlet, 3-1 discard layer. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0042] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "top," and "bottom," etc., indicating orientation or positional relationships, are merely for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein.

[0043] Example 1

[0044] A molding process suitable for composite tube beams with large thickness is provided: taking a large-wall-thickness composite tube beam with a length of 3m, an inner diameter of 129mm, and an outer diameter of 144mm (i.e., a wall thickness of 15mm) as an example, the molding process is used to manufacture it, and a prepreg with a medium-temperature epoxy system is used for manufacturing. The ply reduction ratio of the prepreg at the end is 1:2.

[0045] The process includes the following steps:

[0046] S1. Provide a tubular core mold 1;

[0047] Wherein: the core mold 1 is made of UPVC material, which can meet the strength requirements after vacuum pre-extraction under room temperature conditions; and can meet the requirements of softening and shrinking when heated during curing in the curing oven, so as to allow for core removal and demolding.

[0048] Specifically, the dimensions of the core mold 1 are selected as follows: outer diameter 125mm, wall thickness 10mm, and length 3140mm;

[0049] S2. An inner expansion bag 2 is fitted onto the surface of the core mold 1, and when the inner expansion bag 2 is fitted, a margin is left at both ends of the core mold 1, while ensuring that the outer diameter of the inner expansion bag 2 can be increased to a maximum of 129mm after subsequent inflation.

[0050] Wherein: sealing plates 1-1 are provided at both ends of the core mold 1, and air inlets 1-2 and air outlets 1-3 communicating with the interior of the core mold 1 are respectively provided on the sealing plates 1-1; when the inner expansion bag 2 is fitted onto the surface of the core mold 1, there is a margin at both ends of the core mold 1, and the margin of the inner expansion bag 2 is sealed to the sealing plates 1-1, and the sealing plates 1-1 are fixedly connected to the outer mold 5; specifically, the sealing plates 1-1 are made of steel, and the air inlets 1-2 and air outlets 1-3 are standard air nozzle connectors;

[0051] S3. On the surface of the inner expansion bag 2, composite prepreg is laid according to the design of composite tube beam. In order to improve the molding quality of the final product, during the prepreg laying process, a vacuum bag is made on the layup for pre-compaction after every 4 to 8 layers of prepreg. After multiple laying and pre-compaction, composite tube beam preform 3 is formed.

[0052] Specifically: When laying the prepreg, according to the layer-dropping design ratio, the first layer of prepreg is laid with a length of 3060mm. The layers near both ends of the core mold 1 are designed as layer-dropping 3-1 (the length of layer-dropping 3-1 at both ends corresponds to 30mm on the core mold). Silicone rubber pads 4 are set on the inner expansion bag 2 near both ends of the core mold 1. One end of the silicone rubber pad 4 matches the shape of layer-dropping 3-1, and the other end is flush with the end of the core mold 1. The silicone rubber pad 4 is fixed by pressure-sensitive adhesive tape. Preferably, in order to facilitate demolding, a peelable layer (auxiliary material) 8 can be laid on the surface of the inner expansion bag 2 first, and then the prepreg is laid on the peelable layer 8.

[0053] S4. After the prepreg is laid, an outer mold 5 is tightly attached to the outside of the composite material tube beam precast body 3. The outer mold 5 is made of steel and has a designed length of 3140mm. The outer mold 5 is also provided with a sealing device 7 to further ensure the airtightness of the core mold 1. The sealing device 7 is located between the outer mold 5 and the sealing plate 1-1. The reserved inner expansion bag 2 is sealed and connected to the sealing device 7. After the connection is completed, the outer mold 5 is fixedly connected to the sealing plates 1-1 at both ends of the core mold 1 by sealing bolts 6.

[0054] S5. Inflate the inner expansion bag 2 (equivalent to the core mold 1) through the air inlet 1-2, so that the inner expansion bag 2 generates a pressure of 3 to 25 bar on the composite material tube beam preform 3, and then send the whole into the curing oven for curing according to the curing curve of the composite material prepreg.

[0055] S6. After curing, remove the sealing bolts 6 and remove the outer mold 5. The core mold 1 (UPVC pipe) will soften due to heat and its diameter will become smaller. Then the core can be pulled out and demolded, thereby pulling out the tubular core mold 1 and the inner expansion bag 2. The missing layer 3-1 part is machined and cut flat to obtain the above-mentioned large wall thickness composite material pipe beam with a length of 3m and a wall thickness of 15mm.

[0056] The forming process of the above-mentioned thick-walled composite material tube beam is as follows: Figure 1 As shown.

[0057] The molding process provided by this invention can stably produce composite material tube beams with large thicknesses. This invention, in conjunction with a mandrel, uses an internal expansion molding method to produce thick composite material tube beams, solving problems encountered in current processes for producing thick-walled composite material tube beams, such as insufficient interlayer compaction of the prepreg and susceptibility to axial prepreg extrusion, leading to deformation of the prepreg towards the center and ultimately affecting the quality of the finished product. The molding process provided by this invention can produce composite material tube beams with good quality (i.e., no delamination, wrinkles, smooth outer surface, and uniformly smooth inner surface) and large thickness.

[0058] The molding process of this invention is also applicable to the production of composite material tubes and shafts with greater thickness.

[0059] The above-described preferred embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of the invention. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A forming process suitable for use with composite material pipe beams of greater thickness, characterized in that, The thick composite pipe beam refers to a composite pipe beam with a wall thickness of 8 mm or more. The process comprises the following steps: S1, providing a tubular core mold (1); The core mold (1) has a strength that meets the vacuum pre-extraction requirements at room temperature and softens and shrinks when heated to meet the subsequent core extraction and demolding requirements; S2, setting an inner inflatable bag (2) on the surface of the core mold (1); S3, laying and pre-compacting the composite prepreg on the inner inflatable bag (2) according to the design of the composite pipe beam to form a composite pipe beam preform (3); The layers near the two ends of the core mold (1) are designed as lost layers (3-1), and the end of the inner inflatable bag (2) is provided with a spacer (4); the spacer (4) and the lost layer (3-1) are matched in shape; S4, after the prepreg laying is completed, an outer mold (5) is tightly arranged outside the composite pipe beam preform (3), and the outer mold (5) is fixed; S5, inflate the inner inflatable bag (2) to generate pressure on the composite pipe beam preform (3), and then send it into the curing oven as a whole for curing; S6, after curing, remove the outer mold (5), extract the tubular core mold (1) and the inner inflatable bag (2), and machine to obtain the finished product.

2. A forming process for a composite material pipe beam having a large thickness according to claim 1, wherein The core mold (1) in step S1 is selected from UPVC pipes.

3. The forming process for a composite material pipe beam having a large thickness according to claim 1, wherein The two ends of the core mold (1) are provided with sealing plates (1-1), and the sealing plates (1-1) are respectively provided with inflation ports (1-2) and exhaust ports (1-3); The inner inflatable bag (2) has a surplus when it is set on the surface of the core mold (1), and the surplus inner inflatable bag (2) is sealingly connected with the sealing plate (1-1).

4. A forming process for a composite material tube beam of large thickness according to claim 3, characterized in that, The outer mold (5) is fixedly connected with the sealing plates (1-1) at the two ends of the core mold (1) through sealing bolts (6).

5. A forming process for a composite material tube beam of large thickness according to claim 4, characterized in that, The outer mold (5) is also provided with a sealing device (7) for ensuring the air tightness of the inner inflatable bag (2); the sealing device (7) is arranged between the outer mold (5) and the sealing plate (1-1); The surplus inner inflatable bag (2) is sealingly connected with the sealing device (7).

6. A forming process for a composite material pipe beam having a large thickness according to claim 3, wherein In step S5, the inner inflatable bag (2) is inflated through the inflation port (1-2), and the pressure generated by the inflation is 3-25 bar.

7. The process of claim 1, wherein the composite material pipe beam has a thickness of 0.5 to 5 inches. In step S3, a vacuum bag is made on the core mold (1) after laying and pre-compacting 4-8 layers of prepreg, and the prepreg layers are pre-compacted by vacuum extraction.

8. The forming process for a composite material pipe beam having a large thickness according to claim 1, wherein One end of the spacer (4) in step S3 is matched with the shape of the lost layer (3-1), and the other end is flush with the end of the core mold (1).

9. The process of claim 1, wherein the composite tube beam has a thickness of at least 0.5 inches. The spacer (4) in step S3 is selected from silicone rubber spacers.

10. The forming process for thick composite pipe beams according to claim 1, wherein step S6, the lost layer during laying is processed and cut flat to obtain a thick composite pipe beam.

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