A molding method for a composite material side fairing for a centrifuge

Abstract

This invention discloses a molding method for a centrifuge composite material side fairing in the field of composite material products technology, including the following steps: 1) Prepreg preparation; 2) Prepreg feeding; 3) Prepreg laying, using a female mold to form, laying carbon fiber plain weave prepreg, performing pre-drawing, laying the next layer of prepreg, and performing pre-drawing again until halfway done. When laying the prepreg, it is divided into four laying areas per layer, and the prepreg fiber break lines between each laying area are set on four curved surfaces, and the prepreg fiber break lines between each layer are staggered; 4) First hot pressing; 5) Placement of angle irons, after exiting the can, adding L-shaped angle irons near each corner frame, continuing to lay layers, and the prepreg has through holes that mate with threaded holes; 6) Local reinforcement; 7) Second hot pressing; 8) Demolding, using nuts and L-shaped angle irons for demolding. This invention solves the problem of delamination at the corner frame after the centrifuge side fairing is formed.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, and in particular to a method for molding a side fairing. Background Technology

[0002] Centrifuges are typical inertial instrument calibration and testing devices, used to calibrate and standardize accelerometers in fields such as food, medicine, and the military. During operation, centrifuges rotate at high speeds, generating significant drag torque that consumes 70%-80% of their energy. Therefore, optimized structural design is crucial. Two main methods exist for centrifuge rectification and drag reduction: one utilizes a rectifier shroud, and the other involves installing multiple layers of flat plates on the centrifuge surface to maximize airflow. The first method more effectively reduces drag power while also protecting the accelerometer and other components.

[0003] The shroud is the space where the centrifuge turntable and components operate. It requires not only a smooth and flat inner surface to provide a good operating environment, but also an overall appearance that meets the centrifuge's design specifications. Existing technology discloses a composite material shroud for a heavy-duty ultragravity centrifuge, publication number CN116532249A, published on 2023-08-04. The most important component of the shroud is the side shroud. Existing composite material side shrouds have four corner frames, formed using prepreg. Therefore, considering practical operability, the cuts (fiber break lines) on each side are placed in the corner frames. Over long-term use, delamination occurs at the corner frames, and this delamination gradually increases over time, posing a potential hazard to personnel. Therefore, this issue needs to be considered in the design of the side shroud's molding method. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a molding method for a centrifuge composite material side fairing, solving the problem of delamination at the corner frame after the centrifuge side fairing is molded.

[0005] The objective of this invention is achieved as follows: a method for molding a composite material side fairing for a centrifuge, comprising the following steps:

[0006] Step 1) Prepreg preparation: Carbon fiber unidirectional prepreg and carbon fiber plain weave prepreg are used. The first layer of the inner and outer surfaces of the side fairing uses carbon fiber plain weave prepreg, and the other layers use carbon fiber unidirectional prepreg.

[0007] Step 2) Prepreg cutting: Use software to design the layup diagram of the side fairing. Do not set any fiber breaks of the prepreg at the four corner skeletons. Use an automatic cutting machine to cut the prepreg according to the cutting diagram designed in the software.

[0008] Step 3) Prepreg Laying: Using a negative mold, lay the first layer of carbon fiber plain weave prepreg. After the first layer is laid, lay the peeling cloth to make a vacuum bag. Place a breathable felt at the vacuum nozzle, and connect the breathable felt to the vacuum nozzle and peeling cloth for pre-extraction. After smoothing the excess line, lay the next layer of prepreg and perform pre-extraction again. Repeat this process until half of the laying work is completed. When laying the prepreg, it is divided into four laying areas per layer. The prepreg fiber break lines between each laying area are set on the four curved surfaces, and the prepreg fiber break lines between each layer are staggered.

[0009] Step 4) Hot pressing to make vacuum bags: transport the mold to the autoclave, draw negative pressure in the vacuum bag, and apply positive pressure in the autoclave to compact the prepreg.

[0010] Step 5) Place angle irons. After the product is removed from the can, add an L-shaped angle iron outside the net size area of ​​each hanging frame. Continue to lay up the layers until all layers are finished. The angle irons are machined with threaded holes, and the prepreg is provided with through holes that match the threaded holes.

[0011] Step 6) Local reinforcement: Place reinforcing material sheets outside the product net dimension line at the outer edge of the mold;

[0012] Step 7) Secondary hot pressing to make a vacuum bag. Transport the mold to the autoclave, run it according to the preset curing parameters, cool it under pressure to the set temperature, release the pressure and remove it from the autoclave to obtain the side fairing.

[0013] Step 8) Demolding: Insert bolts through the through holes in the prepreg and rotate the bolts until the front end of the bolts contacts the end face of the mold. Continue to rotate the bolts to increase the gap between the side fairing and the mold. After the side fairing is noticeably loosened from the mold, remove the side fairing to complete the demolding.

[0014] As a preferred technical solution of the molding method of the centrifuge composite material side fairing of the present invention, the opening of the side fairing is square, and the side fairing includes four curved surfaces. The four curved surfaces gradually shrink from the opening to the tip and the area gradually decreases. The connection between the four curved surfaces adopts an arc transition to form a corner frame.

[0015] As a preferred technical solution of the molding method of the centrifuge composite material side fairing of the present invention, in step 5), the inner and outer surfaces of the L-shaped angle iron are pre-wrapped with prepreg.

[0016] As a preferred technical solution of the molding method of the centrifuge composite material side fairing of the present invention, in step 5), after the L-shaped angle iron is placed, a prepreg of a set thickness is pre-laid in the area where the L-shaped angle iron is placed, then the L-shaped angle iron is placed, and the layering continues until the end, and finally a prepreg of a set thickness is laid in the area of ​​the L-shaped angle iron.

[0017] As a preferred technical solution of the molding method of the centrifuge composite material side fairing of the present invention, in step 5), during the laying process, the threaded hole needs to be plugged in advance to prevent the adhesive from entering the threaded hole.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention uses a method of not splitting the fibers in the carbon fiber prepreg at the corner skeleton where the stress is large, which increases the strength and provides a safe operating environment for centrifuges that are used for a long time; and the products made by the present invention are easier to demold. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the side fairing structure obtained by the present invention. Figure 1 .

[0021] Figure 2 This is a schematic diagram of the side fairing structure obtained by the present invention. Figure 2 .

[0022] Figure 3 This is an end view of the side fairing obtained by the present invention.

[0023] Figure 4 This is a schematic diagram of the placement of the angle iron in this invention.

[0024] Figure 5 This is a schematic diagram of local reinforcement in this invention.

[0025] Figure 6 This is a schematic diagram of demolding in this invention.

[0026] Among them, 100 is the side fairing, 101 is the curved surface, 102 is the hanger frame, 103 is the disconnect line, 200 is the angle iron, 201 is the threaded hole, and 300 is the reinforcing sheet. Detailed Implementation

[0027] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0028] A method for molding a composite material side fairing for a centrifuge, such as... Figure 1-2 As shown, the opening of the side fairing 100 is square, and the side fairing 100 includes four curved surfaces 101. The four curved surfaces 101 gradually taper from the opening to the tip and the area gradually decreases. The connection between the four curved surfaces 101 adopts an arc transition to form a corner frame, including the following steps.

[0029] Step 1) Prepreg preparation: Carbon fiber unidirectional prepreg and carbon fiber plain weave prepreg are used. The first layer of the inner and outer surfaces of the side fairing 100 uses carbon fiber plain weave prepreg, while the other layers use carbon fiber unidirectional prepreg.

[0030] Step 2) Prepreg cutting: Use software to design the layup diagram of the side fairing 100. Do not set any fiber breaks of the prepreg at the four corner skeletons 102. Use an automatic cutting machine to cut the prepreg according to the cutting diagram designed by the software.

[0031] Specifically, according to the layup diagram of the side fairing 100 designed using Fibersim software, no fiber breaks of prepreg are set at the four corner frames 102, such as... Figure 3 As shown, the length and width of the material pieces can be set larger than theoretically possible for easier practical operation; use an automatic feeding machine to feed the material according to the feeding diagram designed in Fibersim software.

[0032] It should be noted that, in order to ensure the strength of the corner skeleton 102, no prepreg fiber breaks are provided at the four corner skeletons 102.

[0033] Step 3) Prepreg Laying: Using a negative mold, lay the first layer of carbon fiber plain weave prepreg. After the first layer is laid, lay the peeling cloth to make a vacuum bag. Place a breathable felt at the vacuum nozzle, and connect the breathable felt to the vacuum nozzle and peeling cloth for pre-extraction. After smoothing the excess line, lay the next layer of prepreg and perform pre-extraction again. Repeat this process until half of the laying work is completed. When laying the prepreg, it is divided into four laying areas per layer. The prepreg fiber break line 103 between each laying area is set on the four curved surfaces 101, and the prepreg fiber break lines 103 between each layer are staggered.

[0034] Specifically, the pre-sampling time is generally set to around 30 minutes.

[0035] It should be noted that the use of breathable felt can eliminate air bubbles generated during the laying process to the greatest extent, further ensuring product performance. The four laying zones are laid separately to facilitate the laying of prepreg. At the same time, in order to ensure the strength of the corner skeleton 102, the prepreg fiber break line 103 between each laying zone is set on the four curved surfaces 101. In order to enhance the strength of the break line 103, the prepreg fiber break lines 103 between each layer are staggered.

[0036] Step 4) First hot pressing to make a vacuum bag. Transport the mold to the autoclave, draw negative pressure in the vacuum bag, and apply positive pressure in the autoclave to compact the prepreg.

[0037] Specifically, after half of the layup work is completed, the peeling cloth, release film, and breathable felt are placed to make a vacuum bag. The mold is placed in an autoclave, negative pressure is drawn out of the vacuum bag, and positive pressure is applied in the autoclave. The laid prepreg is compacted in this way, with a pressure of 0.6 MPa and a holding time of about 60 minutes.

[0038] Step 5) Place angle iron 200, remove and clean the auxiliary materials, as follows Figure 4 As shown, L-shaped angle irons 200 are placed at the four corner frames 102. Each L-shaped angle iron 200 has a pair of threaded holes 201. First, the angle iron 200 is wrapped with prepreg on both sides (refer to...). Figure 6 The prepreg needs to have holes of the same size as the threaded holes 201 on the L-shaped angle iron 200 cut out. First, lay a 5mm thick layer of prepreg on the prepreg (to increase local strength during demolding). Continue laying subsequent layers in this manner until all layers are laid. After all layers are laid, add another 5mm thick layer of prepreg on the L-shaped angle iron 200. At the same time, use non-adhesive release cloth to plug the threaded holes 201 to prevent them from becoming ineffective during subsequent demolding if they are blocked by adhesive.

[0039] It should be noted that in actual operation, due to expansion factors, the prepreg adheres tightly to the mold after curing, making demolding difficult. The L-shaped angle iron 200 can be designed to facilitate demolding.

[0040] Step 6) Local reinforcement: Place a 300mm reinforcing sheet outside the product net dimension line at the outer edge of the mold.

[0041] It should be noted that, in order to overcome the problem of small deformation of the product surface inside the cavity during the curing process, outside the net dimension line of the product at the outer edge of the mold, such as Figure 5 As shown, 300mm of reinforcing sheet is laid.

[0042] Step 7) Secondary hot pressing to make a vacuum bag. The mold is transported to the autoclave and run according to the preset curing parameters. It is cooled under pressure to the set temperature, and then depressurized and removed from the autoclave to obtain the side fairing 100.

[0043] Specifically, the auxiliary materials are laid out in the order of peeling cloth-isolation film-breathable felt, a vacuum bag is made along the outside of the mold, the mold is transported to the autoclave, and the curing parameters specified for the prepreg are followed. The mold is then cooled under pressure to 60°C, and the pressure is released from the autoclave to obtain the side fairing 100.

[0044] Step 8) Demolding: Insert bolts through the through holes of the prepreg and rotate the bolts so that the front end of the bolts contacts the end face of the mold. Continue to rotate the bolts, and the gap between the side fairing 100 and the mold will increase. After the side fairing 100 is obviously loosened from the mold, remove the side fairing 100 to complete the demolding.

[0045] Specifically, after removing the vacuum bag and auxiliary materials, demold the side fairing 100. The demolding principle is described in [link to demolding instructions]. Figure 4 , Figure 6 Because the corner frame 102 of the side fairing 100 has high internal stress in the mold after molding, a demolding L-shaped angle iron 200 is placed near each corner frame 102. The angle iron 200 is connected to the composite material. The bolts are forcefully applied using tools, and the threaded holes 201 and bolts are engaged. As the bolts are continuously screwed in, the gap between the product and the mold increases. After the product is obviously loosened from the mold, it can be easily removed. The side fairing 100 after removal is subjected to non-destructive testing, and the non-destructive testing results are good.

[0046] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method of forming a centrifuge composite side fairing, characterized by, The method comprises the following steps: Step 1) Prepreg preparation, carbon fiber unidirectional prepreg and carbon fiber plain weave prepreg are used, carbon fiber plain weave prepreg is used for the first layer of the inner surface and the outer surface of the side fairing (100), and carbon fiber unidirectional prepreg is used for other layers; Step 2) Prepreg blanking, a software is used to design a layering diagram of the side fairing (100), no fiber break of any prepreg is arranged at four corner skeletons (102), and an automatic blanking machine is used to blank according to the blanking diagram designed by the software; Step 3) Prepreg laying, a negative mold is used for forming, carbon fiber plain weave prepreg is laid for the first layer, after the first layer is laid, a skinning cloth is laid, a vacuum bag is made, a breather fabric is arranged at a vacuum nozzle, the breather fabric is connected with the vacuum nozzle and the skinning cloth, pre-extraction is performed, after the remaining amount line is smoothed, the next layer of prepreg is laid, pre-extraction is performed again, and the laying is performed in the same way until the layering work is completed, during the prepreg laying, the prepreg is divided into four laying areas per layer, the prepreg fiber break lines (103) between the laying areas are arranged on the four curved portions (101), and the prepreg fiber break lines (103) between the layers are staggered with each other; Step 4) One-time hot pressing, a vacuum bag is made, the mold is transported into a hot pressing tank, negative pressure is extracted in the vacuum bag, and positive pressure is given in the hot pressing tank to compact the prepreg; Step 5) L-shaped angle iron (200) is placed, after the tank is taken out, an L-shaped angle iron (200) is added outside the product net size area near each corner skeleton, the layering is continuously performed until all the layering is completed, the L-shaped angle iron (200) is internally provided with a threaded hole (201), a through hole matched with the threaded hole (201) is formed in the prepreg, the L-shaped angle iron (200) is pre-wrapped with prepreg on the inner and outer surfaces, after the tank is taken out, the area where the L-shaped angle iron (200) is placed is pre-laid with prepreg of a set thickness, then the L-shaped angle iron (200) is placed, the layering is continuously performed until the layering is completed, and finally, the prepreg of the set thickness is laid in the area of the L-shaped angle iron (200); Step 6) Local reinforcement, a reinforcing sheet (300) is laid outside the product net size line at the outer edge of the mold; Step 7) Two-time hot pressing, a vacuum bag is made, the mold is transported into a hot pressing tank, preset curing parameters are used, the hot pressing tank is cooled to a set temperature under pressure, the pressure is released, the tank is taken out, and the side fairing (100) is obtained; Step 8) Demolding, a bolt is arranged in the through hole of the prepreg, the front end of the bolt is in contact with the end surface of the mold by rotating the bolt, the gap between the side fairing (100) and the mold becomes larger by continuously rotating the bolt, after the side fairing (100) and the mold are obviously loose, the side fairing (100) is taken out, and the demolding is completed.

2. A method of forming a composite material side fairing (100) for a centrifuge according to claim 1, wherein, The opening of the side fairing (100) is square, the side fairing (100) comprises four curved portions (101), the four curved portions (101) are gradually contracted from the opening to the tip end and gradually reduced in area, the connection portions between the four curved portions (101) are transitioned in an arc shape, and the corner skeletons are formed.

3. A method of forming a composite material side fairing (100) for a centrifuge according to claim 2, wherein, During the laying in step 5), the threaded hole (201) needs to be pre-plugged to prevent glue from entering the threaded hole (201).

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