A method of forming a composite cylindrical shell

Abstract

The application discloses a composite material cylindrical shell forming method in the technical field of composite material products, a plurality of annular grooves are processed on the inner periphery of the cylindrical shell, annular protrusions are formed between the annular grooves, and the method comprises the following steps: step 1, material preparation; step 2, mold preparation; step 3, blanking; step 4, I area whole-laying production, pre-impregnated material is laid layer by layer, and the joints are laid with a set size, the first layer needs to be vacuum compacted, vacuum compaction is carried out once every four layers, and pre-curing is carried out after laying; step 5, II area sacrificial layer production; step 6, III area groove area production; step 7, IV area whole-laying production; step 8, curing; step 9, first demolding; step 10, machining; and step 11, second demolding. The application solves the problem that the cylindrical shell is difficult to process in the prior art.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, and in particular to a method for forming a cylindrical shell. Background Technology

[0002] Carbon fiber reinforced resin matrix composites possess characteristics such as high specific strength, high specific modulus, and strong designability, making them a hot topic in materials research. Carbon fiber composite structural components are gradually replacing metal structural components and have been widely used in industries such as automotive, aerospace, shipbuilding, sporting goods, and weaponry in recent years. However, for complex structural components, the application of composite materials is often limited by product quality. Problems such as bridging, wrinkles, porosity, excessive adhesive application, and excessive adhesive content severely affect product quality, especially in irregularly shaped structural components.

[0003] In particular, there is a type of cylindrical shell in the technology, where the thickness at both ends of the shell is greater than the thickness in the middle, and the inner surface of the middle of the shell has multiple circumferential protrusions. This structure is difficult to process and form. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for forming a cylindrical shell made of composite materials, which solves the problem of the high difficulty in processing cylindrical shells in existing technologies.

[0005] The objective of this invention is achieved as follows: a method for forming a cylindrical shell of composite material, wherein the inner circumference of the cylindrical shell is machined with multiple circumferential grooves, and circumferential protrusions are formed between the circumferential grooves, characterized by comprising the following steps:

[0006] Step 1) Material preparation: Take the prepreg out of the cold storage, thaw it at room temperature, and set it aside for use;

[0007] Step 2) Prepare the mold: Install and fasten the cylinder, insert, front flange and rear flange of the mold. The front and rear ends of the insert, the outer periphery of the front section of the cylinder, the outer periphery of the rear section of the cylinder, the front flange and the end face of the rear flange form the front and rear end laying areas of the cylindrical shell. The outer periphery of the insert forms the inner surface laying area of ​​the cylinder. The outer periphery of the insert is provided with a groove formed by the circumferential protrusion for laying the inner surface of the shell. Clean the mold surface and apply a release agent to the mold surface.

[0008] Step 3) Cutting: Based on the strength calculation results, use an automatic fabric cutting machine to cut the prepreg sheets at various angles required for the layup and set them aside for use;

[0009] Step 4) Laying the entire area I: Lay the prepreg layer by layer, setting the dimensions at the joints. The first layer needs to be vacuum compacted, and vacuum compacted once every four layers. After laying, pre-curing is performed.

[0010] Step 5) Create the sacrificial layer in Zone II, the same as in Step 4);

[0011] Step 6) Construction of Zone III: Same as Step 4;

[0012] Step 7) Laying out Zone IV: Same as Step 4);

[0013] Step 8) Curing: Lay out nylon release cloth, porous release film and breathable felt in sequence to make a vacuum bag. After passing the cold pressure test, put it into a hot autoclave for curing.

[0014] Step 9) First demolding: Remove the front flange and rear flange;

[0015] Step 10) Machining: Machin the outer surface of the product according to the drawing requirements;

[0016] Step 11) Second demolding: Remove the fasteners that hold the cylinder and insert together. Lift the product and tooling on the rear flange side. Tap the cylinder to separate the product from the mold and obtain the desired product.

[0017] As a further limitation of the present invention, in step 4), the entire process is carried out along the front flange end face → outer periphery of the front section of the cylinder → surface of the insert → outer periphery of the rear section of the cylinder → rear flange end face.

[0018] As a further limitation of the present invention, in step 5), when laying the prepreg, the layers are laid from the inside out on the surface of the prepreg in zone I, close to the front flange end face and the rear flange end face; the edge of the prepreg is tightly attached to the prepreg on the front flange end face and the rear flange end face in zone I; after the laying of zone II is completed, pre-curing is required. The prepreg is heated and pressurized using an autoclave, and then pre-cured after laying.

[0019] As a further limitation of the present invention, step 6) III includes three parts: the front end of the cylinder, the circumferential protrusion of the cylinder, and the rear end of the cylinder. When laying the front end of the cylinder, the groove area formed by the front flange end face, the outer periphery of the front section of the cylinder, and the front section of the insert is laid. When laying the circumferential protrusion of the cylinder, the groove area on the outer periphery of the insert is laid. When laying the rear end of the cylinder, the groove area formed by the rear section of the insert, the outer periphery of the rear section of the cylinder, and the rear flange end face is laid. During the laying of the groove area, several independent groove areas are laid before a whole laying is performed. The whole laying process is: front flange end face → outer periphery of the front section of the cylinder → insert surface → outer periphery of the rear section of the cylinder → rear flange end face.

[0020] As a further limitation of the present invention, step 7) IV area is a partial area of ​​the outer periphery of the front section of the cylinder, the outer periphery of the insert, and a partial area of ​​the outer periphery of the rear section of the cylinder, which is laid in a whole on the outer periphery of the prepreg that was previously laid.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses carbon fiber prepreg as raw material to effectively reduce the weight of the product; the use of autoclave molding process reduces the porosity of the composite material and improves its structural strength; the shell made by this method does not contain any metal and has a relatively low density, achieving the requirements of small weight and lightness; the use of detachable inserts to control the internal structure can effectively ensure the structural dimensions of the product and the utilization rate of raw materials; through layup design and pre-curing, the operability of the prepreg laying process is improved, which can effectively improve production efficiency and product qualification rate. Attached Figure Description

[0022] 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.

[0023] Figure 1 This is a flowchart of the present invention.

[0024] Figure 2 This is a schematic diagram of the mold structure in this invention.

[0025] Figure 3 This is an exploded view of the mold used in this invention.

[0026] Figure 4 This is a schematic diagram of the cylindrical structure of the mold of the present invention. Figure 1 .

[0027] Figure 5 This is a schematic diagram of the cylindrical structure of the mold of the present invention. Figure 2 .

[0028] Figure 6 This is a cross-sectional view of the mold and product forming of the present invention.

[0029] Figure 7 This is a schematic diagram of the product installation according to the present invention.

[0030] Figure 8 This is a schematic diagram of the product obtained by the present invention.

[0031] Among them, 100 is the cylinder body, 101 is the reinforcing rib, 102 is the countersunk hole, 103 is the front end of the cylinder body, 104 is the circumferential protrusion, 105 is the rear end of the cylinder body, 200 is the insert, 201 is the threaded hole, 300 is the front flange, 400 is the rear flange, 500 is the shell, and 600 is the cylindrical pin. Detailed Implementation

[0032] 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.

[0033] like Figure 1 The method for molding a composite cylindrical shell shown includes the following steps:

[0034] Step 1) Material preparation: Take out the SYT45 / YZ05 carbon fiber stable prepreg from the cold storage and cool it at room temperature for more than 6 hours before use.

[0035] Step 2) Prepare the mold: such as Figure 2-5 As shown, the mold includes a cylindrical body, which serves as the main support and partially as the cladding surface; inserts, installed on the outer periphery of the cylindrical body, with their outer periphery serving as the cladding surface; a front flange, installed on the outer periphery of the front end of the cylindrical body, serving as the front cladding surface of the cylindrical shell; and a rear flange, installed on the outer periphery of the rear end of the cylindrical body, serving as the rear cladding surface of the cylindrical shell. The front end of the cylindrical body has a front reinforcing rib, and the rear end of the cylindrical body has a rear reinforcing rib. The front and rear reinforcing ribs are perpendicular to each other. Multiple inserts are provided and spliced ​​together to form a cylindrical structure, which is fitted onto the outer periphery of the cylindrical body. The outer surface of the cylindrical body and the inner surface of the inserts are both inclined surfaces. The inserts are fastened to the cylindrical body with bolts. The front and rear flanges are connected to the cylindrical body using cylindrical pins. During assembly, the cylindrical body, inserts, and front and rear flanges of the mold are installed, tightened, and the mold surface is cleaned with acetone. A release agent is applied to the mold surface at least three times.

[0036] It should be noted that the mold has a simple structure and adopts an assembly structure, which makes demolding more convenient. After trial use, the mold has good layering operation, easy product demolding, and good product smoothness.

[0037] Step 3) Cutting: Based on the strength calculation results, use an automatic fabric cutter to cut the prepreg sheets at various angles required for the layup.

[0038] Step 4) Construction of Zone I (light green area in the diagram), as follows: Figure 7 As shown, the prepreg is laid layer by layer, with the seam area having a set size for the layer. The layer in this area is 4mm thick, which is 2 / 3 of the actual product thickness. This layer covers the entire mold surface. To improve the quality of the layering, vacuum compaction is performed every 4 layers. The method is to make a vacuum bag to seal the product and the mold, and use the vacuum bag to create negative pressure to pressurize the prepreg.

[0039] It should be noted that when laying the entire section of Zone I, it is necessary to coordinate with the laying of the trench section of Zone III (see step 8 for details). When laying the entire section, the laying should be carried out along the front flange end face → outer periphery of the front section of the cylinder → surface of the insert → outer periphery of the rear section of the cylinder → rear flange end face.

[0040] Step 5) Pre-curing: To further promote the prepreg laying effect, pre-curing is required after completing the I zone layup. During pre-curing, the product and mold should be sealed in a vacuum bag and placed in an autoclave. After heating to 60°C, pressurize to 0.6MPa and maintain for 2.5 hours before cooling down with the furnace.

[0041] It should be noted that pre-curing can promote a tighter prepreg layup, denser carbon fiber, and effectively eliminate gas between prepregs.

[0042] Step 6) Creating the sacrificial layer in Zone II (yellow area in the diagram): (See diagram below) Figure 7 As shown, the layup in this area is located outside the product cutting line. Its function is to assist in the forming of the product flange. In order to ensure that the product flange has good mechanical properties, the layup surface is parallel to the flange surface during the layup process. In this way, the fiber direction is perpendicular to the direction of force, and the product can provide sufficient strength.

[0043] Specifically, in Zone I, the prepreg is laid layer by layer from the inside out, close to the front and rear flange faces. The edges of the prepreg are tightly attached to the prepreg on the front and rear flange faces in Zone I. After the Zone II layup is completed, pre-curing is required. The prepreg is heated and pressurized using an autoclave and then pre-cured after laying.

[0044] Step 7) Pre-curing: To further promote the prepreg laying effect, pre-curing is required after completing the II zone layup.

[0045] Step 8) Construction of Zone III (dark green area in the diagram): (See diagram below) Figure 7 As shown, the III zone includes three parts: the front end of the cylinder A1-A3, the circumferential protrusions of the cylinder B1-B3, and the rear end of the cylinder C1-C3.

[0046] When laying the prepreg at the front end of the cylinder, the prepreg is laid in the groove area formed by the front flange end face, the outer periphery of the front section of the cylinder, and the front section of the insert. When laying the prepreg in this area, the prepreg is in an L-shape.

[0047] When laying the circumferential protrusions of the cylinder, the prepreg is laid flat in the groove area on the outer periphery of the insert.

[0048] When laying the prepreg at the rear end of the cylinder, the prepreg is laid in the groove area formed by the rear section of the insert, the outer periphery of the rear section of the cylinder, and the rear flange end face. When laying the prepreg in this area, the prepreg is in an L-shape.

[0049] During the installation of the grooved area, several independent grooved areas are laid before a whole paving is performed. Specifically, after laying A1, B1-B3, and C1, a whole layer is laid, then A2, B1-B3, and C2 are laid, and then A3, B1-B3, and C3 are laid. The whole paving process is as follows: front flange end face → outer periphery of the front section of the cylinder → insert surface → outer periphery of the rear section of the cylinder → rear flange end face.

[0050] It should be noted that the interleaving of the grooved area and the whole layer ensures the connection strength between the prepreg sheets, effectively prevents the grooved area from debonding from the whole layer, and helps to ensure the rigidity of the product.

[0051] Step 9) Pre-curing: To further promote the prepreg laying effect, pre-curing is required after completing the III zone layup.

[0052] It should be noted that pre-curing can promote a tighter prepreg layup, denser carbon fiber, and effectively eliminate gas between prepregs.

[0053] Step 10) Lay out the entire IV zone (blue area in the diagram): as shown Figure 7 As shown, Zone IV is a partial area of ​​the outer periphery of the front section of the cylinder, the outer periphery of the insert, and a partial area of ​​the outer periphery of the rear section of the cylinder. The prepreg that was previously laid is laid on the outer periphery of the prepreg, which includes partial areas of Zone I and Zone III.

[0054] Step 11) Curing: Final curing: Make a vacuum bag, wrap a porous isolation film and breathable felt on the surface of the mold, place two vacuum nozzles according to the size of the mold, and after passing the cold pressure test, put it into the autoclave for final curing;

[0055] Step 12) First demolding: After the prepreg is cured with the mold, the product blank is obtained. Further machining will produce the product. Before machining, the front and rear flanges need to be removed, and the cylinder and inserts are retained as machining fixtures.

[0056] It should be noted that, since the end faces of the product need to be machined, the front flange and rear flange, and the remaining molds need to be used as machine tooling, which greatly facilitates the machining process.

[0057] Step 13) Machining: According to the drawing requirements, the composite blank can be machined to obtain the required product; furthermore, the outer surface of the part can be coated according to the usage requirements.

[0058] Step 14) Second demolding: During demolding, remove the bolts securing the cylinder and insert. On the rear flange side, use a wooden block to lift the product, suspending the mold in the air. Gently tap the cylinder with a wooden hammer to separate the product from the mold, obtaining the desired product. Figure 8 As shown.

[0059] It should be noted that the wooden hammer will not damage the composite product, and the cylindrical mold is conical, so demolding can be achieved under the action of gravity and hammering.

[0060] 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 for molding a cylindrical shell made of composite materials, wherein the inner circumference of the cylindrical shell is machined with multiple circumferential grooves, and circumferential protrusions are formed between the circumferential grooves, characterized in that, Includes the following steps: Step 1) Material preparation: Take the prepreg out of the cold storage, thaw it at room temperature, and set it aside for use; Step 2) Prepare the mold: Install and fasten the cylinder, insert, front flange and rear flange of the mold. The front and rear ends of the insert, the outer periphery of the front section of the cylinder, the outer periphery of the rear section of the cylinder, the front flange and the end face of the rear flange form the front and rear end laying areas of the cylindrical shell. The outer periphery of the insert forms the inner surface laying area of ​​the cylinder. The outer periphery of the insert is provided with a groove formed by the circumferential protrusion for laying the inner surface of the shell. Clean the mold surface and apply a release agent to the mold surface. Step 3) Cutting: Based on the strength calculation results, use an automatic fabric cutting machine to cut the prepreg sheets at various angles required for the layup and set them aside for use; Step 4) Laying the entire area I: Lay the prepreg layer by layer, setting the dimensions at the joints. The first layer needs to be vacuum compacted, and vacuum compacted once every four layers. After laying, pre-curing is performed. Step 5) Fabrication of the sacrificial layer in Zone II: During installation, lay the prepreg layer in Zone I from the inside out, close to the front and rear flange faces. The edges of the prepreg should be tightly bonded to the prepreg on the front and rear flange faces of Zone I. After completing the Zone II layer, pre-curing is required. Use an autoclave to heat and pressurize the prepreg, and then pre-cur it after installation. Step 6) Construction of Zone III groove area. Zone III groove area consists of three parts: front end of cylinder, circumferential protrusion of cylinder, and rear end of cylinder. When laying the front end of cylinder, the groove area formed by the front flange end face, the outer periphery of the front section of cylinder, and the front section of the insert is laid. When laying the circumferential protrusion of cylinder, the groove area on the outer periphery of the insert is laid. When laying the rear end of cylinder, the groove area formed by the rear section of the insert, the outer periphery of the rear section of cylinder, and the rear flange end face is laid. During the groove area laying process, several independent groove areas are laid before a whole laying is carried out. The whole laying process is: front flange end face → outer periphery of the front section of cylinder → insert surface → outer periphery of the rear section of cylinder → rear flange end face. Step 7) Laying out Zone IV: Zone IV is a section of the outer periphery of the front section of the cylinder, the outer periphery of the insert, and a section of the outer periphery of the rear section of the cylinder. The entire area is laid on the outer periphery of the prepreg that was previously laid. Step 8) Curing: Lay out nylon release cloth, porous release film and breathable felt in sequence to make a vacuum bag. After passing the cold pressure test, put it into a hot autoclave for curing. Step 9) First demolding: Remove the front flange and rear flange; Step 10) Machining: Machin the outer surface of the product according to the drawing requirements; Step 11) Second demolding: Remove the fasteners that fix the cylinder and the insert, lift the product and tooling on the rear flange side; knock the cylinder to separate the product and the mold, and obtain the desired product.

2. The method for forming a composite cylindrical shell according to claim 1, characterized in that, Step 4) When laying the lining, lay it along the front flange end face → outer periphery of the front section of the cylinder → surface of the insert → outer periphery of the rear section of the cylinder → rear flange end face.

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