Air duct forming mold and forming method thereof

Abstract

The present invention provides an air duct forming mold and a forming method thereof. The mold includes a mold body and a first forming element and a second forming element used in conjunction with the mold body and for forming the overlapping surface of the air duct. The mold body includes a hollow cylinder, a plurality of bosses surrounding the cylinder and arranged on the outer wall of the cylinder and spaced apart from each other for forming the air duct cavity. An annular protrusion is provided on the outer wall of the cylinder between adjacent bosses. The shapes of the first and second forming elements match the bosses and are snapped onto the bosses when forming the air duct. A thermal expansion extrusion piece is placed between adjacent first or second forming elements. After the mold is paved with prepreg sheets, it is coated, expansion extrusion blocks are placed, vacuuming and curing are performed to finally obtain the formed air duct. The air duct forming mold and forming method provided by the present invention realize the mass production of air ducts while ensuring the forming quality of the overlapping surface of the air ducts.

Description

Technical Field

[0001] The present invention belongs to the field of composite materials, and in particular relates to an air duct forming die and a forming method thereof. Background Art

[0002] Fiber reinforced composite materials have the advantages of light weight, high temperature resistance, sound absorption, moisture resistance, fire resistance, corrosion resistance, high strength, etc., and are gradually being used in aerospace and military products. Among them, fiber reinforced composite air ducts (the shape of which is as follows Figure 1 As shown, the whole is an arc-shaped structure, the central angle of the circle can be, for example, 60-175 degrees, and it includes an arc-shaped cavity and side wings connected to both sides of the cavity) and has gradually replaced other metal material air ducts and been promoted and applied, especially in the air conditioning system of large rocket launchers in the military industry. When the air duct is in use, the air duct needs to be bonded to the cylindrical body. If the air duct is directly formed into a circle, it is not easy to bond to the body. Therefore, it is necessary to bond a section of the air duct to the body first (the side wings of the air duct are bonded to the body), and then connect it with another section of the air duct. At least two air ducts are bonded to the cylindrical body, and multiple air ducts are connected in the circumferential direction to form an approximate ring, and then multiple annular air ducts are connected in the axial direction to form a channel. The existing technology is to directly bond the connecting surfaces of the two air ducts together. This connection method is not firm. Especially when the thickness of the two air ducts is inconsistent, the connection is prone to breakage and leakage. On the other hand, there are many problems in the current manufacture of air ducts. Air ducts are either produced individually or in batches, but batch production has low efficiency. The air ducts need to be put into an autoclave for curing, which increases production costs, and the air tightness of the air ducts cannot be guaranteed. Summary of the Invention

[0003] In view of the problems existing in the prior art, the present invention provides an air duct forming mold and a forming method thereof, which can realize the mass production of air ducts while ensuring the forming quality of the overlapping surfaces of the air ducts.

[0004] In the first aspect, the present invention provides an air duct forming mold, which includes a mold body and a first forming element and a second forming element used in conjunction with the mold body and for forming the overlapping surface of the air duct. The mold body includes a hollow cylinder, a plurality of bosses surrounding the cylinder that are arranged on the outer wall of the cylinder and spaced apart from each other for forming the air duct cavity, and an annular protrusion is provided on the outer wall of the cylinder between adjacent bosses. The shapes of the first forming element and the second forming element match the bosses and are snapped onto the bosses when forming the air duct, and a thermal expansion extrusion part is placed between adjacent first forming elements or second forming elements.

[0005] Furthermore, the first forming element and the second forming element are respectively in the shape of a "J", including two vertical surfaces, a first curved surface connecting the two vertical surfaces, and a second curved surface connected to one end of the vertical surface away from the first curved surface and extending along the axial direction of the cylinder. The length of the first curved surface along the boss is consistent with the length of the overlapping surface between the air ducts. The first forming element and the second forming element can be buckled on the same boss or covered on different bosses. The second curved surface extends to the space between the boss and the protrusion. The first forming element and the second forming element are 3D printed parts. The material can be, for example, carbon fiber reinforced polyphenylene sulfide (PPS / CF), glass fiber reinforced polyphenylene sulfide (PPS / GF) and other composite materials. The thickness of the first forming element or the second forming element is consistent with the thickness of the formed air duct. The 3D printed parts have strong design and replaceability, which increases the flexibility of replacing the first forming element and the second forming element. Without changing the mold, the first forming element or the second forming element of different thicknesses can be replaced to achieve the molding of overlapping surfaces of air ducts of different thicknesses.

[0006] Furthermore, the distance between the two vertical surfaces of the first forming element is equal to the sum of the width of the boss and twice the thickness of the air duct, and the distance between the two vertical surfaces of the second forming element is equal to the width of the boss. When the first forming element is in use, the prepreg sheet is first laid on the boss, and then the first forming element is buckled onto the boss. When the second forming element is in use, the second forming element is first buckled onto the boss, and then the prepreg sheet is laid.

[0007] Furthermore, the height of the protrusion protruding from the outer wall of the cylinder is preferably not less than the sum of the thickness of the air duct side wing and the thickness of the second curved surface. When the thickness of the air duct increases, the thickness of the second curved surface is reduced without changing the mold. The space between the protrusion and the boss is used to form the air duct side wing, and the distance between the protrusion and the boss is greater than the width of the air duct side wing.

[0008] Furthermore, the thermal expansion extrusion piece is an arc-shaped block made of silicone rubber, and the length of the thermal expansion extrusion piece is consistent with the length of the first molding element or the second molding element.

[0009] Furthermore, both ends of the cylinder are open, and a plurality of radial reinforcing ribs are provided in the openings. The plurality of reinforcing ribs converge toward the center of the cylinder opening and are connected to a ring plate provided in the center of the cylinder. The reinforcing ribs and the ring plate are connected, for example, by bolts, and the number of the reinforcing ribs can be, for example, 4-8.

[0010] Furthermore, a plurality of axial reinforcement ribs are fixed to the inner wall of the cylinder. The plurality of ribs are evenly distributed on the inner wall of the cylinder. The number of the ribs may be, for example, 3-6.

[0011] Furthermore, adjacent ribs are connected with circumferential reinforcement strips.

[0012] Furthermore, the height of the boss is consistent with the inner cavity height of the formed air duct, the width of the boss is consistent with the inner cavity width of the formed air duct, and the distance between adjacent bosses is less than 0.85%-1.0% of the width of the thermal expansion extrusion part.

[0013] When the first forming element and the second forming element are used, for example, the first forming element is used to form the overlapping surface of the first air duct. First, the composite material sheet used to manufacture the first air duct is laid on the boss, and then the first forming element is wrapped around the end of the sheet of the first air duct (the end of the first forming element is aligned with the end of the sheet, and the first forming element is wrapped with, for example, a rubberized release cloth). The second forming element is used to form the overlapping surface of the second air duct. The second forming element is first fixed on another boss (for example, fixed with a rubberized release cloth, and the outer surface of the boss is aligned with the inner surface of the second forming element). The surface matches, the end of the composite material sheet used to manufacture the second air duct is aligned with one end of the second forming element for laying, the thickness of the second forming element is consistent with the laying thickness of the sheet of the first air duct on the boss, after all the sheets of the first air duct and the second air duct are laid, they are covered, the expansion extrusion block is placed, vacuuming and curing process are carried out to finally obtain the formed first air duct and second air duct, the second air duct is overlapped on the first air duct at the overlap surface, the first forming element is used to ensure the outer surface of the first air duct, and the second forming element is used to ensure the inner surface of the second air duct.

[0014] In a second aspect, the present invention provides a method for forming an air duct using the above-mentioned mold, the method being as follows:

[0015] (1) preparing a prepreg sheet, a first forming element, a second forming element, and a thermal expansion extrusion part;

[0016] (2) Laying multiple layers (e.g., 3-10 layers, preferably 5-8 layers) of prepreg sheets for forming the first air duct along the boss of the mold, wrapping a first molding element around one end of the sheet to form the overlapping surface of the first air duct, fixing a second molding element on the boss near the first molding element, aligning one end of the prepreg sheet for forming the second air duct with one end of the second molding element to form the overlapping surface of the second air duct, and laying multiple layers (e.g., 3-10 layers, preferably 5-8 layers) of prepreg sheets for forming the second air duct on the boss in a direction away from the first molding element;

[0017] (3) Repeat step (2) to lay prepreg sheets on each circle of bosses of the mold and wrap the first molding element and the second molding element;

[0018] (4) Laying the release cloth on the mold surface, and placing the thermal expansion extrusion parts between adjacent first forming elements and between adjacent second forming elements respectively;

[0019] (5) Use vacuum bag film and sealing strips to cover the entire mold and evacuate;

[0020] (6) Place the mold in an oven, cool it down, and continue to vacuum until the curing is complete;

[0021] (7) Take out of the oven, demould, check the air tightness of the air duct, and finally overlap the second air duct on the first air duct at the overlap surface, and bond the overlapped air duct to the cylindrical body.

[0022] Furthermore, in step (1), the prepreg sheet is a long strip of carbon fiber composite material, and the aspect ratio can be, for example, 10-20:1, preferably 12-18:1. More preferably, the width of the prepreg sheet is such that one end of the prepreg sheet in the length direction just extends to the protrusion.

[0023] Furthermore, in step (1), a first molding element and a second molding element are printed using a 3D printer, wherein the thickness of the second molding element is consistent with the thickness of the prepreg sheet of the first air duct laid on the boss, the distance between the two vertical surfaces of the second molding element is equal to the width of the boss, and the distance between the two vertical surfaces of the first molding element is equal to the sum of the width of the boss and twice the thickness of the air duct.

[0024] Furthermore, in step (2), the second arc surface of the first forming element and the second forming element extends to the space between the boss and the protrusion.

[0025] Furthermore, in step (4), the heat expansion extrusion part is a silicone rubber block. After the silicone rubber is placed, the silicone rubber expands itself after being heated, which can cause the outer surfaces of the vertical surfaces of the first air duct and the second air duct to be compressed, especially at the corner positions. The compression effect is good, so that the vacuum bag inserted later will not be suspended, and the prepreg resin is not easy to lose, thereby increasing the air tightness of the air duct.

[0026] Furthermore, in step (6), the temperature in the oven is 100-200°C, preferably 120-180°C, more preferably 130-150°C, and the oven is kept warm for 1.5-4h, preferably 2-3h.

[0027] Beneficial effects of the present invention:

[0028] The composite material air duct forming mold of the present invention is provided with multiple annular bosses, so that multiple products can be formed on the same mold, which solves the problem of batch production of air ducts and improves efficiency; the first forming element and the second forming element are simple to make and are completed by 3D printing, with strong design and replaceability, which increases the flexibility of replacing the first forming element and the second forming element. At the same time, the first forming element and the second forming element ensure the quality of the overlapping surface and reduce the fitting gap between the air ducts; the thermal expansion extrusion part expands and extrude the vertical surface of the air duct when heated, and can be formed using an oven, thereby reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the air duct structure.

[0030] Figure 2 It is a structural schematic diagram of an air duct forming mold of the present invention.

[0031] Figure 3 This is a front view of an air duct forming mold of the present invention.

[0032] Figure 4 for Figure 3 Enlarged view of point I in the middle.

[0033] Figure 5 It is a schematic structural diagram of the first forming element or the second forming element.

[0034] Figure 6 This is a cross-sectional view of the first forming element in use.

[0035] Figure 7 Cross-sectional view of the second forming element in use

[0036] Figure 8 Schematic diagram of the structure of the first air duct and the second air duct overlap

[0037] Figure 9 This is a cross-sectional view of the overlap between the first air duct and the second air duct.

[0038] Figure 10 Schematic diagram of bosses and protrusions.

[0039] Reference numerals:

[0040] 1-mold body, 1-1-cylinder, 1-2 boss, 2-first forming element, 3-second forming element, 4-vertical surface, 5-first arc surface, 6-second arc surface, 7-protrusion, 8-reinforcement rib, 9-ring plate, 10-rib, 11-reinforcement strip, 13-first air duct, 14-second air duct, 15-thermal expansion extrusion part, 16-air duct cavity, 17-side wing. DETAILED DESCRIPTION

[0041] The present invention is further described below with reference to the accompanying drawings and examples.

[0042] In the description of the present invention, it should be understood that the directional relationships indicated by the terms "upper", "lower", "rear", "front", "inside", "outside", etc. are based on the directional relationships shown in the accompanying drawings. They are only for the convenience of explaining the simple description of the present invention and cannot be considered as limitations on the present invention. In addition, the terms "first" and "second" are only used to distinguish the descriptive purposes and cannot be understood as indicating their relative importance. Therefore, the definition of "first" and "second" explicitly indicates that they have the same characteristics. It should be noted that, unless otherwise clearly stipulated and defined, the terms "set" and "connected" should be understood in a broad sense. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to actual conditions.

[0043] like Figure 1-10 As shown, the present invention provides an air duct forming mold, which includes a mold body 1 and a first forming element 2 and a second forming element 3 used in conjunction with the mold body 1 and for forming the lap joint surface of the air duct. The mold body 1 includes a hollow cylinder 1-1, a plurality of bosses 1-2 surrounding the cylinder that are arranged on the outer wall of the cylinder 1-1 and arranged at intervals from each other for forming the air duct cavity, and an annular protrusion 7 is provided on the outer wall of the cylinder between adjacent bosses 1-2. The shapes of the first forming element 2 and the second forming element 3 are consistent with the bosses 1-2 and are snapped onto the bosses 1-2 when forming the air duct. A thermal expansion extrusion part 15 is placed between adjacent first forming elements 2 or second forming elements 3.

[0044] like Figure 5 As shown, the first forming element 2 and the second forming element 3 are respectively in the shape of a "J", including two vertical surfaces 4, a first curved surface 5 connecting the two vertical surfaces 4, and a second curved surface 6 connected to one end of the vertical surface 4 away from the first curved surface 5 and extending axially along the cylinder 1-1. The length of the first curved surface 5 along the length of the boss 1-2 is consistent with the length of the overlapping surface between the air duct. The first forming element 2 and the second forming element 3 can be buckled on the same boss 1-2 or covered on different bosses 1-2. The second curved surface 6 extends to the space between the boss 1-2 and the protrusion 7. The first forming element 2 The first and second molding elements 2 and 3 are 3D printed parts, and the material may be, for example, composite materials such as carbon fiber reinforced polyphenylene sulfide (PPS / CF) and glass fiber reinforced polyphenylene sulfide (PPS / GF). The thickness of the first molding element 2 or the second molding element 3 is consistent with the thickness of the molded air duct. The 3D printed parts have strong design and replaceability, which increases the flexibility of replacing the first molding element 2 and the second molding element 3. Without changing the mold, the first molding element 2 or the second molding element 3 of different thicknesses can be replaced to achieve the molding of the overlapping surfaces of air ducts of different thicknesses.

[0045] The distance between the two facades 4 of the first molding element 2 is equal to the sum of the width of the boss and twice the thickness of the air duct. The distance between the two facades 4 of the second molding element 3 is equal to the width of the boss. When the first molding element 2 is in use, the prepreg sheet is first laid on the boss, and then the first molding element 2 is buckled onto the boss. When the second molding element 3 is in use, the second molding element 3 is first buckled onto the boss 1-2, and then the prepreg sheet is laid.

[0046] The height of the protrusion 7 protruding from the outer wall of the cylinder 1-1 is preferably not less than the sum of the thickness of the air duct side wing and the thickness of the second curved surface 6. When the thickness of the air duct increases, the thickness of the second curved surface 6 is reduced without changing the mold. The space between the protrusion 7 and the boss 1-2 is used to form the air duct side wing, and the distance between the protrusion 7 and the boss 1-2 is greater than the width of the air duct side wing.

[0047] The thermal expansion extrusion member 15 is an arc-shaped block made of silicone rubber. The length of the thermal expansion extrusion member 15 is consistent with the length of the first molding element 2 or the second molding element 3 .

[0048] The cylinder 1-1 is open at both ends, and a plurality of radial reinforcing ribs 8 are provided in the openings. The plurality of reinforcing ribs 8 converge toward the center of the opening of the cylinder 1-1 and are connected to a ring plate 9 provided at the center of the cylinder 1-1. The reinforcing ribs 8 and the ring plate 9 are connected, for example, by bolts. The number of reinforcing ribs 8 can be, for example, 4-8.

[0049] A plurality of axial reinforcement ribs 10 are fixed to the inner wall of the cylinder 1 - 1 . The plurality of ribs 10 are evenly distributed on the inner wall of the cylinder 1 - 1 . The number of the ribs 10 may be 3-6, for example.

[0050] Adjacent ribs 10 are connected by circumferential reinforcement strips 11 .

[0051] The height of the boss 1-2 is consistent with the inner cavity height of the formed air duct, the width of the boss 1-2 is consistent with the inner cavity width of the formed air duct, and the distance between adjacent bosses 1-2 is less than 0.85%-1.0% of the width of the thermal expansion extrusion part 15.

[0052] When the first forming element 2 and the second forming element 3 are in use, for example, the first forming element 2 is used to form the overlapping surface of the first air duct 13. First, the composite material sheet used to manufacture the first air duct 13 is laid on the boss 1-2, and then the first forming element 2 is wrapped around the end of the sheet of the first air duct 13 (the end of the first forming element 2 is aligned with the end of the sheet, and the first forming element 2 is wrapped with, for example, a release cloth with adhesive). The second forming element 3 is used to form the overlapping surface of the second air duct 14. The second forming element 3 is first fixed on the boss (for example, fixed with a release cloth with adhesive, and the outer surface of the boss matches the inner surface of the second forming element). The end of the composite material sheet used to manufacture the second air duct 14 is aligned with one end of the second forming element 3 and laid. The thickness of the second forming element 3 is consistent with the laying thickness of the sheet of the first air duct 13 on the boss.

[0053] The prepreg used in the following examples to prepare the air duct is FT300-3K / IS1303-200 / 50-1000, the first molding element and the second molding element are made of PPS / CF, and the thermal expansion extrusion piece is a silicone rubber block.

[0054] Example

[0055] Method for preparing the first air duct and the second air duct using a mold:

[0056] (1) The prepreg was cut into sheets with a length of 1810 mm and a width of 100 mm, and a silicone rubber block with a thickness of 12 mm and a width of 32.32 mm was prepared. The first molding element and the second molding element were printed using a 3D printer. The thickness of the second molding element was consistent with the thickness of the prepreg sheet of the first air duct laid on the boss.

[0057] (2) Lay 4 layers of prepreg sheets for forming the first air duct along the boss of the mold, and use the first forming element wrapped with adhesive release cloth to wrap one end of the sheet. The end of the sheet wrapped with the first forming element is called end A (i.e., the end that overlaps with the second air duct), and the end not wrapped with the first forming element is called end B.

[0058] Use adhesive release cloth to secure the second molded element to the boss near end A. Align one end of the prepreg sheet for forming the second air duct with one end of the second molded element. Lay four layers of prepreg sheets for forming the second air duct on the boss, away from the first molded element. The end of the prepreg sheet covering the second molded element is end C (i.e., the end that overlaps the first air duct), and the end not covering the second molded element is end D.

[0059] (3) Repeat step (2) to lay prepreg sheets on each circle of bosses of the mold and wrap the first molding element and the second molding element;

[0060] (4) Laying a layer of release cloth on the mold surface, and placing thermal expansion extrusion parts between adjacent first molding elements and between adjacent second molding elements;

[0061] (5) Use vacuum bag film and sealing strips to cover the entire mold and evacuate;

[0062] (6) Place the mold in an oven and heat it to 130°C. Keep it at this temperature for 3 hours and then cool it down to cure. During this period, continue to vacuum until the curing is complete.

[0063] (7) Remove from the oven, demould and clean the surface auxiliary materials and burrs, check the air tightness of the air duct, and finally connect the A end of the first air duct with the C end of the second air duct (such as Figure 8 As shown), the B end of the first air duct and the D end of the second air duct are respectively connected to the arc-shaped connecting plate.

[0064] While the A ends and C ends of the first air duct and the second air duct are overlapped, their annular portions also need to be bonded to the cylindrical inner structure.

Claims

1. A composite material air duct forming mold, characterized in that: The invention comprises a mold body (1) and a first forming element (2) and a second forming element (3) used in conjunction with the mold body (1) and used to form the overlap surface of the air duct. The mold body (1) comprises a hollow cylinder (1-1), a plurality of bosses (1-2) surrounding the cylinder and arranged on the outer wall of the cylinder (1-1) and spaced apart from each other for forming the cavity of the air duct. An annular protrusion (7) is provided on the outer wall of the cylinder between adjacent bosses (1-2). The shapes of the first forming element (2) and the second forming element (3) match the bosses (1-2) and are buckled onto the bosses (1-2) when forming the air duct. A protrusion (7) is placed between adjacent first forming elements (2) or second forming elements (3). There is a thermal expansion extrusion component (15), the first forming element (2) and the second forming element (3) are respectively in a "J" shape, including two vertical surfaces (4), a first curved surface (5) connecting the two vertical surfaces (4), and a second curved surface (6) connected to one end of the vertical surface (4) away from the first curved surface (5) and extending axially along the cylinder (1-1), the length of the first curved surface (5) along the boss (1-2) is consistent with the length of the overlapping surface between the air duct, the first forming element (2) and the second forming element (3) can be buckled on the same boss (1-2) or covered on different bosses (1-2), and the second curved surface (6) extends to the space between the boss (1-2) and the protrusion (7).

2. The composite material air duct forming die according to claim 1, wherein: The first molding element (2) and the second molding element (3) are 3D printed parts, and the material is carbon fiber reinforced polyphenylene sulfide (PPS / CF) or glass fiber reinforced polyphenylene sulfide (PPS / GF) composite material. The thickness of the first molding element (2) or the second molding element (3) is consistent with the thickness of the molded air duct.

3. The composite material air duct forming mold according to claim 1, characterized in that: The distance between the two facades (4) of the first forming element (2) is equal to the sum of the width of the boss and twice the thickness of the air duct, and the distance between the two facades (4) of the second forming element (3) is equal to the width of the boss.

4. The composite material air duct forming die according to claim 1, characterized in that: The height of the protrusion (7) protruding from the outer wall of the cylinder (1-1) is not less than the sum of the thickness of the air duct side wing and the thickness of the second curved surface (6), and the space between the protrusion (7) and the boss (1-2) is used to form the air duct side wing.

5. The composite material air duct forming die according to claim 1, characterized in that: The thermal expansion extrusion piece (15) is an arc-shaped block made of silicone rubber. The length of the thermal expansion extrusion piece (15) is consistent with the length of the first molding element (2) or the second molding element (3).

6. The composite material air duct forming die according to claim 1, characterized in that: The height of the boss (1-2) is consistent with the height of the inner cavity of the formed air duct, the width of the boss (1-2) is consistent with the width of the inner cavity of the formed air duct, and the distance between adjacent bosses (1-2) is less than 0.85%-1.0% of the width of the thermal expansion extrusion part (15).

7. A method for forming an air duct using the mold according to any one of claims 1 to 6, the method being as follows: (1) Preparing a prepreg sheet, a first molding element, a second molding element, and a thermal expansion extrusion part; (2) Laying multiple layers of prepreg sheets for forming the first air duct along the boss of the mold, wrapping the first molding element around one end of the sheet to form the overlapping surface of the first air duct, fixing the second molding element on the boss near the first molding element, aligning one end of the prepreg sheet for forming the second air duct with one end of the second molding element to form the overlapping surface of the second air duct, and laying multiple layers of prepreg sheets for forming the second air duct on the boss in a direction away from the first molding element; (3) Repeat step (2) to lay prepreg sheets on each circle of the boss of the mold and wrap the first molding element and the second molding element; (4) Laying the release cloth on the mold surface, and placing the thermal expansion extrusion parts between adjacent first forming elements and between adjacent second forming elements respectively; (5) Use vacuum bag film and sealing strips to cover the entire mold and evacuate; (6) Place the mold in an oven, cool it down, and solidify it. During this period, vacuum is continuously applied until the solidification is completed. (7) Take out of the oven, demould, check the air tightness of the air duct, and finally overlap the second air duct on the first air duct at the overlap surface, and glue the overlapped air duct to the cylindrical body.

8. The method according to claim 7, characterized in that In step (4), the thermal expansion extrusion part is a silicone rubber block.

9. The method according to claim 7, characterized in that In step (6), the temperature in the oven is 100-200°C, and the oven is kept warm for 1.5-4 hours.

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