A molding die and molding method for the rear section shell of a composite material outer bypass casing for an engine.

Abstract

This invention discloses a molding die and molding method for the rear section shell of an engine composite material bypass casing in the field of composite material product technology. The molding die includes a rotating body set on a frame; the top of the frame is provided with multiple sets of support rollers, and the inner side of the rotating body is supported on the support rollers. Under the action of the support rollers, the rotating body can rotate. This invention solves the problems of yield rate and molding quality of the rear section shell of the engine bypass casing.

Description

Technical Field

[0001] This invention relates to the field of composite material products technology, and in particular to a composite material outer bypass casing rear section housing for an engine. Background Technology

[0002] To achieve a high thrust-to-weight ratio, modern aero-engines can increase thrust and reduce structural weight. Composite materials, a new type of material with many excellent characteristics such as high specific strength, high specific stiffness, and strong design flexibility, can reduce the weight of aero-engine structural components by about 20%-30%, which is of great significance for improving the overall technical performance of the structure. Abroad, the application of resin-based composite materials in aero-engines began in the 1970s. After NASA successfully developed PMR-type polyimide, T300 / PMR15 composite materials were successfully used to develop composite outer bypass ducts, intermediate casings, nozzle adjustment vanes, and other parts suitable for use in engines, achieving significant weight reduction effects and quickly being promoted in various engine models.

[0003] Most of the composite material outer casings of a certain type of engine currently in service are made of T300 / PMR15 polyimide composite material. Traditional auxiliary materials used in autoclave processes, such as vacuum bags, sealing tapes, peelable layers, and gas-conducting felts, decompose at the high temperatures (above 350°C) during polyimide composite molding and cannot withstand the high temperatures. A small amount of dedicated high-temperature resistant auxiliary materials have extremely poor processability at room temperature; sealing tapes lack adhesiveness; vacuum bags are easily broken; and the probability of bag bursting and air leakage during product curing is extremely high, easily resulting in scrap and defects. At the same time, small molecule substances may leak out during the preparation and curing of polyimide prepregs, and the products generally have excessive manufacturing defects, leading to reduced safety of the casing shell and a high scrap rate of casing production materials; the molded rear section shell has a defect of about 1 meter in length in the R-zone, and the shell delamination expansion leads to a reduction in component life.

[0004] A novel engine outer bypass casing forming process is disclosed in the prior art, with the publication number CN109591319 A, which has some of the above-mentioned drawbacks. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a molding die and molding method for the rear section shell of an engine's composite material outer bypass casing, solving the problems of yield rate and molding quality of the rear section shell of the engine's outer bypass casing.

[0006] The objective of this invention is achieved as follows: a molding die for the rear section shell of an engine composite material bypass casing includes a rotating body mounted on a frame; the top of the frame is provided with multiple sets of support rollers, and the inner side of the rotating body is supported on the support rollers, allowing the rotating body to rotate under the action of the support rollers.

[0007] As a preferred technical solution of the molding die of the present invention, the support rollers are provided in three sets, each set of support rollers is provided with two rollers, two sets of which are symmetrically arranged on both sides of the other set, and the three sets of support rollers are on the same arc surface, and the arc surface is coaxial with the rotating body.

[0008] As a preferred technical solution of the molding die of the present invention, the rotating body includes a main body die, an upper flange die and a lower flange die. The upper and lower surfaces of the main body die extend radially to form an upper support flange and a lower support flange, and the upper and lower surfaces of the main body die extend axially outward to form an upper mounting flange and a lower mounting flange.

[0009] As a preferred technical solution of the molding die of the present invention, a stepped mounting surface is formed between the laying surface of the main die and the upper mounting flange and the lower mounting flange, and the upper flange die and the lower flange die are fixed on the stepped mounting surface.

[0010] As a preferred technical solution of the molding die of the present invention, a compensation gasket is provided between the upper mounting flange, the lower mounting flange and the main mold.

[0011] A method for molding the rear section shell of a composite material outer bypass casing for an engine, using the aforementioned molding die, includes the following steps:

[0012] Step 1) Assemble the mold. First, install the upper flange mold and the lower flange mold onto the main mold. When assembling the rotating body, leave an machining allowance between the upper flange mold and the lower flange mold. The distance should be greater than the design distance. After the rotating body is assembled, install it onto the frame.

[0013] Step 2) Prepare the prepreg. Make the prepreg into materials for the main ply and R-corner filler strips to cooperate with the main ply process of the casing. The prepreg is T300 / B2501 bismaleimide resin-based prepreg.

[0014] Step 3) Pre-form the R-corner filler strip, and fill the mold with the pre-formed R-corner filler strip, then vacuum pre-form it;

[0015] Step 4) After preforming, the top area of ​​the rotating body is laid out using a manual layering process. After partial laying is completed, the rotating body is rotated to continue laying layers, so that the laid layer is always at the top.

[0016] Step 5) Finally, lay up the prepreg according to the gradient layup principle to make up for the insufficient thickness on the side of the flange near the outer edge of the casing;

[0017] Step 6) After the paving is completed, pre-forming is carried out. After the pre-forming is completed, the bolts are unscrewed and the upper flange mold and the lower flange mold are removed. The compensation gasket is removed and then the upper flange mold and the lower flange mold are installed. After installation, the bolts are tightened so that the inner surfaces of the upper flange mold and the lower flange mold are attached to the step installation surface.

[0018] Step 7) Vacuuming is performed using a vacuum bag film, followed by curing and shaping in an autoclave;

[0019] Step 8) Demolding machine is used to obtain the final engine composite material outer bypass casing rear section shell.

[0020] As a preferred technical solution of the molding method described in this invention, the specific steps of step 3) preforming the R-angle filler strip are as follows: the R-angle filler strip is a composite of bismuth adhesive film and prepreg. The adhesive film is placed on the prepreg and rolled into a round rod shape, which is then placed in the R-angle preforming mold. The theoretical R-area shape is pressed out using a vacuum bag. The fiber direction of the R-angle is 90° circumferentially around the shell. The R-angle filler strip consists of four 90° arc structures on each of the upper and lower end faces. The interface joint is a 45° oblique butt joint.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention patent uses bismaleimide resin-based prepreg to manufacture the composite material outer casing rear section shell. Under the premise of meeting the usage requirements, the product qualification rate reaches over 95%, and the internal molding quality is significantly better than the original polyimide composite outer casing rear section. There is almost no internal delamination in the circumferential R-zone. The raw material cost is more than 40% lower than the original polyimide composite. Due to the lower curing temperature and pressure, the cost of auxiliary materials is also greatly reduced, the requirements for autoclave equipment are reduced, and energy consumption is significantly reduced. The R-zone manufacturing technology with R-corner pre-filling increases the tensile strength of the R-zone by 50% compared to the original polyimide rear section shell. Attached Figure Description

[0023] 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.

[0024] Figure 1 This is a schematic diagram of the molding die structure in this invention.

[0025] Figure 2 This is a schematic diagram of the frame structure in this invention.

[0026] Figure 3 This is a side view of the frame in this invention.

[0027] Figure 4 This is a schematic diagram of the rotating body structure in this invention.

[0028] Figure 5 This is a partial cross-sectional view of the rotating body in this invention.

[0029] Figure 6 This is a flowchart of the molding method in this invention.

[0030] Figure 7 This is a schematic diagram of the R-corner filling block structure in this invention.

[0031] Figure 8 This is a top view of the R-intersection filling block in this invention.

[0032] Among them, 100 is the frame, 101 is the central shaft, 102 is the pin, 103 is the support roller, 200 is the rotating body, 201 is the main body mold, 201a is the upper support flange, 201b is the lower support flange, 201c is the upper mounting flange, 201d is the lower mounting flange, 202 is the upper flange mold, 203 is the lower flange mold, 204 is the axial screw, 205 is the compensating washer, and 300 is the R angle filler strip. Detailed Implementation

[0033] 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.

[0034] like Figure 1-5 The mold shown is a molding die for the rear section shell of the composite material outer bypass casing of an engine, including a rotating body 200 set on a frame 100; the top of the frame 100 is provided with multiple sets of support rollers 103, the inner side of the rotating body 200 is supported on the support rollers 103, and the rotating body 200 can rotate under the action of the support rollers 103.

[0035] Specifically, the frame 100 is made of welded square tubing. Rollers are provided at the bottom of the frame 100, and a central shaft 101 is fixed at the top of the frame 100. Support rollers 103 are mounted on the central shaft 101 via bearings. The two ends of the central shaft 101 are machined into square shapes, and the top of the frame 100 is machined with corresponding square grooves. The square grooves are connected to the two ends of the central shaft 101 via pins 102. Grooves are machined on the support rollers 103, and the inner ring of the rotating body 200 is supported in the grooves.

[0036] It should be noted that the support point of the rotating body 200 is located in the upper area. Under the action of its own weight, the rotating body 200 is supported on the support roller 103. Under normal conditions, the rotating body 200 will not move. An external force needs to be applied to push the rotating body 200 to make it rotate, thus ensuring the stability of the paving process.

[0037] Furthermore, the support rollers 103 are provided in three sets, with two sets of support rollers 103 in each set. Two sets are symmetrically arranged on both sides of the other set, and the three sets of support rollers 103 are located on the same arc surface, and the arc surface is coaxial with the rotating body 200.

[0038] Specifically, the support roller 103 located in the middle is supported at the apex of the inner ring of the rotating body 200, and the angle between the other two support points and the apex is approximately 30°.

[0039] This design further ensures the stability of the rotating body when supported by 200°.

[0040] Furthermore, the rotating body 200 includes a main body mold 201, an upper flange mold 202, and a lower flange mold 203. The upper and lower surfaces of the main body mold 201 extend radially to form an upper support flange 201a and a lower support flange 201b. The upper and lower surfaces of the main body mold 201 extend axially outward to form an upper mounting flange 201c and a lower mounting flange 201d. A stepped mounting surface is formed between the laying surface of the main body mold 201 and the upper mounting flange 201c and the lower mounting flange 201d. The upper flange mold 202 and the lower flange mold 203 are fixed on the stepped mounting surface.

[0041] Specifically, the main mold 201 is a cylindrical structure. The upper support flange 201a and the lower support flange 201b are used to support the support rollers 103. The upper mounting flange 201c and the lower mounting flange 201d are used to install the packaging auxiliary materials required for autoclave curing, including isolation film, breathable felt, sealing tape and vacuum bag film, etc. The upper flange mold 202 and the lower flange mold 203 are fixed to the stepped mounting surface by axial screws 204. The inner sides of the upper flange mold 202 and the lower flange mold 203 are also machined with corresponding inner steps.

[0042] Thus, the top surface of the main mold 201 forms a bonding surface with the inner surface of the upper flange mold 202 and the inner surface of the lower flange mold.

[0043] Furthermore, a compensation washer 205 is provided between the upper mounting flange 201c, the lower mounting flange 201d and the main mold 201.

[0044] Specifically, the compensation washer 205 has a thickness of 0.5mm and is used to compensate for the metal expansion caused by entering the autoclave.

[0045] like Figure 6The method for molding the rear section shell of the composite material outer bypass casing of an engine, shown in the figure, uses the molding mold of Example 1 and includes the following steps.

[0046] Step 1) Assemble the mold. First, install the upper flange mold 202, lower flange mold 203, and compensation washer 205 onto the main body mold 201 using axial screws 204. When assembling the rotating body 200, leave an machining allowance between the upper flange mold 202 and the lower flange mold 203. The distance should be greater than the design distance. After the rotating body 200 is assembled, install it onto the frame 100.

[0047] Step 2) Prepare the prepreg. Make the prepreg into materials for the main layup layer and materials for the R-corner filler strip 300 to cooperate with the main layup process of the casing. The prepreg is T300 / B2501 bismaleimide resin-based prepreg. T300 is the carbon fiber type and B2501 is the resin type.

[0048] Step 3) Pre-form the R-angle filler strip 300. First, fill the mold with the pre-formed R-angle filler strip 300, then vacuum pre-form it. The specific steps for pre-forming the R-angle filler strip 300 are as follows: The R-angle filler strip 300 is a composite of bismuth adhesive film and prepreg. The adhesive film is placed on the prepreg and rolled into a round rod shape. It is then placed in the R-angle pre-forming mold and pressed into the theoretical R-area shape using a vacuum bag. The fiber direction of the R-angle is 90° circumferentially around the shell. The R-angle filler strip 300 consists of four 90° arc structures on each of its upper and lower end faces. The interface joint is a 45° bevel butt joint. Figure 7-8 As shown.

[0049] Step 4) After preforming, the top area of ​​the rotating body 200 is laid out using a manual layering process. After partial laying is completed, the rotating body 200 is rotated to continue laying layers, so that the laid layer is always at the top.

[0050] Step 5) Finally, the prepreg is laid up according to the gradient layup principle to make up for the insufficient thickness on the side of the flange near the outer circumference of the casing. Specifically: the shell is made of prepreg manually laid on the mold. During the layup process, the layup starts on the main mold 201 surface. Since the flange area is larger than the theoretical plane, if the material is not replenished in time, uneven thickness is likely to occur at the flange. For this product, in order to improve the layup efficiency, it is not necessary to replenish the material for each layer. After all the main layup layers are completed, the flange arc material is used for gradient thickness replenishment, which can effectively solve the problem of uneven flange thickness and greatly improve the layup efficiency.

[0051] Step 6) After the paving is completed, pre-forming is performed. After pre-forming, the bolts are unscrewed and the upper flange mold 202 and lower flange mold 203 are removed. The compensation washer 205 is removed and then the upper flange mold 202 and lower flange mold 203 are installed. After installation, the bolts are tightened so that the inner surfaces of the upper flange mold 202 and lower flange mold 203 are attached to the step mounting surface.

[0052] Step 7) Vacuuming is performed using a vacuum bag film, followed by curing and shaping in an autoclave.

[0053] Step 8) Demolding machine is used to obtain the final engine composite material outer bypass casing rear section shell.

[0054] The principle by which this invention solves the technical problem will be explained in detail below.

[0055] 1. The use of a special mold in the embodiment makes the tiling process more convenient. Since it is a manual tiling process, the comfort of the operator directly affects the accuracy and efficiency of the tiling. The special mold allows the workers to maintain the most comfortable posture during the tiling without having to make too many physical movements, which greatly improves the accuracy and efficiency of the tiling.

[0056] 2. To facilitate the later assembly of the shell and ensure the parallelism of the upper and lower end faces and the overall height of the shell, the present invention specifically defines the following feature in step 1): When assembling the rotating body 200, the distance between the upper flange mold 202 and the lower flange mold 203 is made with an allowance, which is greater than the design distance. This feature increases the thickness of the overall shell during installation, so that the upper and lower flanges have the allowance of the frame 100, thereby ensuring the parallelism of the upper and lower end faces and the overall height.

[0057] 3. Since the final product will be sent to an autoclave for curing, the mold is made of 45# steel. Under high temperature forming temperature, the main structure of the 45# steel mold, including the flange mold, will thermally expand and extend by more than 0.5mm on one side. However, the composite material itself does not generate much thermal expansion at the forming temperature, which causes the composite material flange to form a gap with the mold at high temperature, making it impossible to effectively pressurize the flange structure. Therefore, before the prepreg is laid, a 0.5mm thick compensation gasket needs to be placed on the flange mold at both ends. Before final curing, the gasket is removed to compensate for the extension under high temperature curing. This effect is specifically limited by the addition of compensation gasket 205 in step 1) and the characteristics in step 6).

[0058] 4. In order to facilitate the laying of the R-corner filler strip 300, the entire ring-shaped R-corner filler strip 300 is not easy to lay. The present invention defines the R-corner filling area as consisting of four 90° arcs on the upper and lower end faces. In addition, in order to increase the mechanical properties of the R-corner at the joint, a 45° oblique butt joint is selected for the interface joint to increase the contact area. This effect is specifically defined in step 3).

[0059] 5. This invention modifies the temperature resistance of bismaleimide resin, resulting in a molding temperature more than 100°C lower than that of the original polyimide composite outer casing. This significantly improves the operability of auxiliary materials used in vacuum systems, such as vacuum bags, sealing tapes, and breathable felts. It avoids the decomposition of auxiliary materials at high molding temperatures and the easy breakage of vacuum bags, greatly reducing the chance of bag bursting and air leakage during curing, thus significantly improving the product yield. Furthermore, the bismaleimide resin-based prepreg releases almost no solvents or volatile small molecules during curing, providing favorable conditions for low porosity in the product. The layability of the bismaleimide resin-based prepreg is far superior to that of polyimide prepreg, greatly reducing defects such as bubbles and bridging caused by poor layability, effectively controlling the problem of excessive product defects.

[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 molding die for the rear section shell of an engine composite material bypass casing, characterized in that, Includes a rotating body (200) mounted on a frame (100); the top of the frame (100) is provided with multiple sets of support rollers (103), the inner side of the rotating body (200) is supported on the support rollers (103), and the rotating body (200) can rotate under the action of the support rollers (103). There are three sets of support rollers (103), and each set of support rollers (103) has two rollers. Two sets are symmetrically arranged on both sides of the other set. The three sets of support rollers (103) are on the same arc surface, and the arc surface is coaxial with the rotating body (200). The rotating body (200) includes a main body mold (201), an upper flange mold (202), and a lower flange mold (203). The upper and lower surfaces of the main body mold (201) extend radially to form an upper support flange (201a) and a lower support flange (201b). The upper and lower surfaces of the main body mold (201) extend axially outward to form an upper mounting flange (201c) and a lower mounting flange (201d). A stepped mounting surface is formed between the paving surface of the main body mold (201) and the upper mounting flange (201c) and the lower mounting flange (201d). The upper flange mold (202) and the lower flange mold (203) are fixed on the stepped mounting surface.

2. The molding die for the rear section shell of the engine composite material outer bypass casing according to claim 1, characterized in that, Compensating gaskets (205) are provided between the upper mounting flange (201c), the lower mounting flange (201d) and the main mold (201).

3. A method for molding the rear section shell of an engine composite material bypass casing, using the molding die described in claim 1 or 2, characterized in that, Includes the following steps: Step 1) Assemble the mold. First, install the upper flange mold (202) and the lower flange mold (203) onto the main body mold (201). When assembling the rotating body (200), leave an machining allowance between the upper flange mold (202) and the lower flange mold (203). The distance is greater than the design distance. After the rotating body (200) is assembled, install it onto the frame (100). Step 2) Prepare the prepreg. Make the prepreg into materials for the main ply and R-corner filler strips (300) to cooperate with the main ply process of the casing. The prepreg is T300 / B2501 bismaleimide resin-based prepreg. Step 3) Pre-form the R-corner filler strip (300), and fill the mold with the pre-formed R-corner filler strip (300) and vacuum pre-form it; Step 4) After preforming, the top area of ​​the rotating body (200) is laid out using a manual layering process. After partial laying is completed, the rotating body (200) is rotated to continue laying, so that the layered surface is always at the top. Step 5) Finally, lay up the prepreg according to the gradient layup principle to make up for the insufficient thickness on the side of the flange near the outer edge of the casing; Step 6) After the paving is completed, pre-forming is carried out. After the pre-forming is completed, the bolts are unscrewed and the upper flange mold (202) and lower flange mold (203) are removed. The compensation gasket (205) is removed and then the upper flange mold (202) and lower flange mold (203) are installed. After installation, the bolts are tightened so that the inner surfaces of the upper flange mold (202) and lower flange mold (203) are attached to the step mounting surface. Step 7) Vacuuming is performed using a vacuum bag film, followed by curing and shaping in an autoclave; Step 8) Demolding machine is used to obtain the final engine composite material outer bypass casing rear section shell.

4. The molding method for the rear section shell of an engine composite material bypass casing according to claim 3, characterized in that, Step 3) The specific steps of the pre-formed R-angle filler strip (300) are as follows: The R-angle filler strip (300) is a composite of bismuth adhesive film and prepreg. The adhesive film is placed on the prepreg and rolled into a round rod shape. It is then placed in the R-angle pre-forming mold and pressed out the theoretical R-area shape using a vacuum bag. The fiber direction of the R-angle is 90° circumferential to the shell. The R-angle filler strip (300) consists of four 90° arc structures on the upper and lower end faces. The interface joint is a 45° oblique butt joint.

Images