Composite tie rod mold and forming method combining autoclave and dry winding

Abstract

The present invention discloses a composite tie rod mold and forming method combining autoclave and dry winding, including laying mold preparation, a plurality of annular grooves provided at the end of the mold, and an inverted isosceles trapezoidal structure in axial cross section; laying prepreg, autoclave curing, processing and demoulding, gluing, dry winding, curing, grinding, and surface treatment process. The present invention adopts a process combining autoclave and dry winding, which has high efficiency, quantified process, high appearance quality, and controllable weight; autoclave and dry winding can strictly control the resin content, the operating environment is dry and there is no waste of raw materials, the weight of the product can be accurately controlled, and the production efficiency is high. The fiber winding products are rich in categories and widely used. They can be applied to the Shenzhou spacecraft load-bearing components in the high-tech fields of aerospace and weapon equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of composite tie rod forming, and in particular to a composite tie rod mold and a forming method combining an autoclave and dry winding. Background Art

[0002] Most of the existing composite tie rod forming processes use autoclave forming processes and prepreg tube rolling processes. The autoclave laying process is to lay the carbon fiber prepreg on the mold according to the laying requirements, seal the blank in a vacuum bag, and place it in a carbon fiber autoclave. Under a vacuum state, the autoclave equipment goes through procedures such as heating, pressurizing, heat preservation, cooling, and pressure relief, and solidification is achieved using the uniform temperature and uniform pressure provided simultaneously in the autoclave, thereby forming a carbon fiber composite material part with high surface and internal quality and complex shape. However, the conventional autoclave laying process is inefficient, the process is complicated, and the appearance quality of the formed composite tie rod is poor.

[0003] The tube rolling process uses heated rollers on a tube winder to soften the prepreg and melt the resin adhesive. Under a certain tension, the friction between the rollers and the mandrel during rotation continuously winds the prepreg onto the tube core to the desired thickness. The tube core is then cooled and shaped by cold rollers before being removed from the winder, wrapped with heat shrink film, and cured in an oven. After the tube has cured, the heat shrink film and inner core mold are removed to create a composite rolled tube. While the tube rolling process is highly efficient, it lacks the ability to close the ends, making it unsuitable for the production requirements of various tie rods. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a composite tie rod mold and forming method combining autoclave and dry winding, which has high working efficiency, quantified process, high appearance quality and controllable weight.

[0005] To this end, the technical solution of the present invention is: a composite tie rod mold combining an autoclave and dry winding, including a rod-shaped main body, the diameters of the two end portions of the rod-shaped main body are smaller than the rod-shaped main body, and are transitionally connected to the rod-shaped main body through a conical section; a plurality of annular grooves are provided on the ends of the rod-shaped main body and the conical section, and the axial cross-section of the annular groove is an inverted isosceles trapezoidal structure.

[0006] Another technical solution of the present invention is: a composite rod forming method combining autoclave and dry winding, using the above mold, comprising the following steps:

[0007] 1) Preparation of paving mold: Apply release agent on the mold;

[0008] 2) Prepreg laying: The prepreg is manually laid on the mold. The laying is divided into three areas: the circumferential groove at the end of the mold is the first area, the circumferential groove on the conical section is the second area, and the rest of the mold is the third area. The three areas are laid alternately at 0 degrees, 45 degrees, or 90 degrees to form a fiber layer.

[0009] 3) Autoclave curing: After the paving is completed, the fiber layer is pressurized and cured by a pressurizing device;

[0010] 4) Processing and demoulding: Divide the solidified fiber layer into two parts along the axis and demould from the mold;

[0011] 5) Bonding: Use structural adhesive to bond the bushing and the two fiber layers. The bushing includes a straight section and a second tapered section. A retaining ring is provided on the side of the straight section. Both the straight section and the second tapered section are provided with a circumferential groove. The axial cross-section of the groove is an inverted isosceles trapezoidal structure. The fiber layer is sleeved on the outside of the bushing, with the inner wall of the fiber layer in contact with the outer wall of the bushing, and the end of the fiber layer rests on the retaining ring.

[0012] 6) Dry winding: The prepreg / prepreg tape is wound on the mold surface, and a heating device is used for online heating during the winding process;

[0013] 7) Curing: After winding is completed, the composite rod is cured by step-by-step heating;

[0014] 8) Grinding: Grind the surface of the composite material pull rod to eliminate the surface tumors;

[0015] 9) Surface treatment: After grinding, use epoxy resin glue to brush the surface of the composite material tie rod.

[0016] Preferably, the paving method adopted in step 2) is as follows:

[0017] Layer 1: The first, second, and third areas are all paved along 0 degrees;

[0018] Second layer: The first and second areas are paved at 90 degrees, and the third area is not paved; Third layer: The first and second areas are paved at 90 degrees, and the third area is not paved; Fourth layer: The first, second and third areas are paved at +45 degrees;

[0019] The fifth layer: the second area is tiled along 90 degrees, and the first and third areas are not tiled;

[0020] Layer 6: The first and second areas are both paved along 0 degrees, and the third area is not paved;

[0021] Layer 7: The first, second and third areas are all paved along 0 degrees;

[0022] 8th layer: The second area is paved along +45 degrees, and the first and third areas are not paved;

[0023] 9th layer: The second area is paved along +45 degrees, and the first and third areas are not paved;

[0024] 10th layer: The first, second and third areas are all paved along 0 degrees;

[0025] 11th layer: the first and second areas are paved along 0 degrees, and the third area is not paved; 12th layer: the second area is paved along 90 degrees, and the first and third areas are not paved;

[0026] 13th layer: The first, second and third areas are all paved along +45 degrees;

[0027] 14th layer: The first and second areas are paved at 90 degrees, and the third area is not paved;

[0028] 15th layer: The first and second areas are paved at 90 degrees, and the third area is not paved;

[0029] 16th layer: The first, second and third areas are all paved along 0 degrees.

[0030] Preferably, in step 1), the release agent used is RM-1937. After the release agent is applied by brushing, it is left to air for more than 15 minutes and repeatedly applied by brushing for 3 times.

[0031] Preferably, in step 3), before pressurization, the surface of the pull rod is wrapped with a release cloth, a non-porous isolation film, a breathable felt, and a vacuum bag film in sequence, and the vacuum bag is sealed with a pressure-sensitive tape. The pressurization pressure is 1 bar to 20 bar, and the curing temperature is 100 to 150°C, and the curing time is 1 to 15 hours.

[0032] Preferably, in step 6), the prepreg yarn / prepreg tape is pre-impregnated with carbon fiber and epoxy resin, and the width of the prepreg yarn / prepreg tape is 5-12 mm; the tension during winding is 20-30 N, the heating temperature of the heating device is 50-60 ° C, the heating method is hot air, infrared, ultrasonic or hot roller, and a temperature measurement control system is installed.

[0033] Preferably, in step 6), local fiber winding thickening is performed at the bushing joint position at an angle of 85-89 degrees, with a thickness of 2-3 mm, and the winding geodesic angle and layup are [±45]2s.

[0034] Preferably, in step 7), the curing temperature is 100-150° C., the heating rate is 2° C. / min, and the curing time is 4-6 hours.

[0035] Preferably, in step 8), sandpaper is used for polishing, and the mesh number of the sandpaper is 50-200 meshes.

[0036] Preferably, in step 9), cleaning is required after polishing, and the cleaning agent used is ethyl acetate or acetone for cleaning, and after cleaning, epoxy resin glue is brushed on the surface.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The combination of autoclave and dry winding technology has high efficiency, quantified process, high appearance quality and controllable weight;

[0039] 2. Autoclave and dry winding can strictly control the resin content (accurate to within 2%), the operating environment is dry and there is no waste of raw materials. It can accurately control the weight of the product and has high production efficiency.

[0040] 3. The bushing is provided with grooves of conical structure and inverted isosceles trapezoidal structure, which fit with the closing part of the composite tie rod, ensuring that the bushing will not be separated or pulled off during the tensile and compressive load tests; a retaining ring is provided at the end of the bushing, and the retaining ring diameter is larger than the diameter of the composite tie rod, so that the bushing will not be pressed into the fiber layer during the compression load test, thereby preventing the bushing from being separated from the composite tie rod;

[0041] 4. Fiber-wound products are rich in categories and widely used. They can be used in the Shenzhou spacecraft load-bearing components in the high-tech fields of aerospace and weapons equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The following is a further detailed description of the embodiments of the present invention in conjunction with the accompanying drawings.

[0043] Figure 1 Schematic diagram of the structure of the mold of the present invention;

[0044] Figure 2 for Figure 1 A partial enlarged view of

[0045] Figure 3 is a flow chart of the method of the present invention;

[0046] Figure 4 Schematic diagram of the structure of the composite tie rod of the present invention;

[0047] Figure 5 It is a structural schematic diagram of the bushing of the present invention;

[0048] Figure 6 This is a cross-sectional view of the structure of the bushing and the composite pull rod of the present invention.

[0049] Marked in the figure are: rod-shaped body 1, end 2, first annular groove 21, inverted isosceles trapezoidal structure 22, conical section 3, second annular groove 31, bushing 4, straight section 41, second conical section 42, retaining ring 43, third groove 44, fourth groove 45, fiber layer 5. DETAILED DESCRIPTION

[0050] In the description of the present invention, it should be noted that, for directional words, such as the terms "center", "horizontal (X)", "longitudinal (Y)", "vertical (Z)", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like, indicating directions and positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and cannot be understood as limiting the specific scope of protection of the present invention.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features. Therefore, the terms "first" and "second" may explicitly or implicitly refer to one or more of these features. Throughout the description of the present invention, "several" and "a number" mean two or more, unless otherwise specifically defined.

[0052] See the accompanying drawings. The composite tie rod mold described in this embodiment includes a rod-shaped body 1. The diameter of each end portion 2 of the rod-shaped body is smaller than that of the rod-shaped body 1, and the ends 2 are transitionally connected to the rod-shaped body 1 via a conical section 3. A plurality of annular grooves are provided on both the end portion and the conical section of the rod-shaped body. The end portion 2 is provided with a first annular groove 21, and the conical section 3 is provided with a second annular groove 31. The axial cross-section of the annular grooves is an inverted isosceles trapezoidal structure 22, i.e., the two side walls of the annular groove are symmetrically inclined surfaces, forming an isosceles concave portion.

[0053] The composite tie rod to be produced in this embodiment has a length of 612 mm, a diameter of 32.5 mm, a wall thickness of 1.25 mm, a weight of 215 g, and a designed tensile limit load of greater than 3 tons.

[0054] The forming method of the composite tie rod includes the following steps:

[0055] 1) Preparation of paving mold: Apply release agent on the mold. The release agent used is RM-1937. After the release agent is applied, let it dry for more than 15 minutes and apply it repeatedly for 3 times.

[0056] 2) Prepreg laying: The prepreg is manually laid on the mold. The laying is divided into three areas: the first annular groove at the end of the mold is the first area S1, the second annular groove on the conical section is the second area S2, and the rest of the mold is the third area S3. The three areas are laid alternately at 0 degrees, 45 degrees, or 90 degrees.

[0057] The paving methods adopted are shown in Table 1:

[0058] Table 1 Paving plan

[0059]

[0060] Specifically:

[0061] Layer 1: The first area S1, the second area S2, and the third area S3 are all paved along 0 degrees;

[0062] Layer 2: The first area S1 and the second area S2 are both tiled at 90 degrees, and the third area S3 is not tiled;

[0063] Layer 3: The first area S1 and the second area S2 are both tiled at 90 degrees, and the third area S3 is not tiled;

[0064] The 4th layer: the first area S1, the second area S2, and the third area S3 are all paved along +45 degrees;

[0065] Layer 5: The second area S2 is tiled along a 90-degree angle, and the first area S1 and the third area S3 are not tiled;

[0066] Layer 6: The first area S1 and the second area S2 are both tiled along 0 degrees, and the third area S3 is not tiled;

[0067] Layer 7: The first area S1, the second area S2, and the third area S3 are all paved along 0 degrees;

[0068] Layer 8: The second area S2 is tiled along +45 degrees, and the first area S1 and the third area S3 are not tiled;

[0069] Layer 9: The second area S2 is tiled along +45 degrees, and the first area S1 and the third area S3 are not tiled;

[0070] Layer 10: The first area S1, the second area S2, and the third area S3 are all paved along 0 degrees;

[0071] 11th layer: the first area S1 and the second area S2 are both paved along 0 degrees, and the third area S3 is not paved;

[0072] Layer 12: The second area S2 is tiled at 90 degrees, and the first area S1 and the third area S3 are not tiled;

[0073] 13th layer: The first area S1, the second area S2, and the third area S3 are all paved along +45 degrees;

[0074] 14th layer: The first area S1 and the second area S2 are both paved at 90 degrees, and the third area S3 is not paved;

[0075] 15th layer: The first area S1 and the second area S2 are both paved at 90 degrees, and the third area S3 is not paved;

[0076] 16th layer: The first area S1, the second area S2, and the third area S3 are all paved along 0 degrees.

[0077] 3) Autoclave curing: After paving is completed, the surface of the composite rod is wrapped with release cloth, non-porous isolation film, breathable felt, and vacuum bag film in sequence, and the vacuum bag is sealed with sub-sensitive tape. After the sealing is completed, vacuum is evacuated to 0.7-0.9 bar, and then the power is turned off for 5-20 minutes. Manually check that the vacuum degree does not drop more than 0.05 bar, and then put the composite rod into the autoclave for curing. The curing system is: 125±5℃, the holding time is 120 minutes, and the vacuum is evacuated throughout the process. The vacuum degree in the vacuum bag is not less than -0.05MPa.

[0078] 4) Processing and demoulding: the solidified fiber layer 5 is divided into two parts along the axis and demoulded from the mold;

[0079] 5) Bonding: Use structural adhesive to bond the bushing 4 and the two fiber layers 5 together, ensuring product dimensions. The bushing 4 is hollow and includes a straight section 41 and a second tapered section 42. A retaining ring 43 is located on the side of the straight section 41. The diameter of the retaining ring 43 is larger than the diameter of the ends of the fiber layers 5. The ends of the fiber layers 5 rest against the retaining ring 43, preventing the bushing from being pressed into the fiber layers during the compression load test, causing the bushing to separate from the fiber layers.

[0080] A third groove 44 is provided in an annular direction on the straight section 41, and a fourth groove 45 is provided in an annular direction on the second conical section 42, and the axial cross-sections of the third groove 44 and the fourth groove 45 are inverted isosceles trapezoidal structures; the fiber layer 5 is sleeved on the outside of the bushing 4, and the closing part of the fiber layer fits with the outer wall of the bushing. The grooves with an inverted isosceles trapezoidal structure on the bushing can ensure that the bushing will not detach or pull off during tensile and compressive load tests.

[0081] 6) Dry winding: The prepreg / prepreg tape is wound on the mold surface through a tension control device and a yarn guide wheel. The prepreg / prepreg tape is made of carbon fiber and epoxy resin pre-impregnated, and the width of the prepreg / prepreg tape is 5-12mm. The dry winding method uses one strand of prepreg and controls the prepreg temperature to 45-85°C. The winding method is spiral winding with a winding angle of 45 degrees. At the same time, during the winding process, the winding tension is 30-40N and the winding speed is 80-120m / min.

[0082] During the winding process, a heating device is used for online heating. The heating temperature of the heating device is 50-60℃. The heating method is hot air, infrared, ultrasonic or hot roller, and a temperature measurement control system is installed.

[0083] At the bushing joint position, local fiber winding thickening is performed at 85-89 degrees with a thickness of 2-3 mm. The winding geodesic angle and layup are [±45]2s.

[0084] 7) Curing: After winding, the composite rod is cured by step-by-step heating. The curing system is 115-125°C and the holding time is 3-5 hours.

[0085] 8) Grinding: Grind the surface of the composite material pull rod to eliminate the surface nodules; use sandpaper for grinding, the mesh number of the sandpaper is 50-200 mesh.

[0086] 9) Surface treatment: After grinding, it needs to be cleaned. The cleaning agent used is ethyl acetate or acetone. After cleaning, the surface is brushed with epoxy resin glue.

[0087] After the tensile limit load test, the tensile load of the composite tie rod in this embodiment was 8.5 tons, and the failure form was bushing fracture; the tensile loads of the composite tie rods made using the prepreg autoclave process and the prepreg staggered tube process without adding the anti-fall-off pre-embedded area were 3.6 tons and 3.8 tons respectively, and the failure form was bushing shedding.

[0088] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A composite rod forming method combining autoclave and dry winding, characterized in that: The following steps are involved: 1) Preparing the paving mold: Apply a release agent to the mold. The mold comprises a rod-shaped body, with both ends of the rod-shaped body having a smaller diameter than the rod-shaped body and transitionally connected to the rod-shaped body via a conical section. A plurality of annular grooves are provided on the ends of the rod-shaped body and the conical section. The axial cross-section of the annular grooves is an inverted isosceles trapezoidal structure. 2) Prepreg laying: The prepreg is manually laid on the mold. The laying is divided into three areas: the circumferential groove at the end of the mold is the first area, the circumferential groove on the conical section is the second area, and the rest of the mold is the third area. The three areas are laid alternately at 0 degrees, 45 degrees, or 90 degrees to form a fiber layer. 3) Autoclave curing: After the laying is completed, the fiber layer is pressurized and cured by a pressurizing device; 4) Processing and demoulding: Divide the solidified fiber layer into two parts along the axis and demould from the mold; 5) Bonding: Use structural adhesive to bond the bushing and the two fiber layers. The bushing includes a straight section and a second tapered section. A retaining ring is provided on the side of the straight section. Both the straight section and the second tapered section are provided with a circumferential groove. The axial cross-section of the groove is an inverted isosceles trapezoidal structure. The fiber layer is sleeved on the outside of the bushing, with the inner wall of the fiber layer in contact with the outer wall of the bushing, and the end of the fiber layer rests on the retaining ring. 6) Dry winding: The prepreg / prepreg tape is wound on the mold surface, and a heating device is used for online heating during the winding process; 7) Curing: After winding, the composite rod is cured by step-by-step heating. 8) Grinding: Grind the surface of the composite material pull rod to eliminate the surface tumors; 9) Surface treatment: After grinding, use epoxy resin glue to brush the surface of the composite material tie rod.

2. The composite rod forming method combining autoclave and dry winding as claimed in claim 1, characterized in that: The paving method adopted in step 2) is as follows: Layer 1: The first, second, and third areas are all paved along 0 degrees; Second layer: The first and second areas are tiled at 90 degrees, and the third area is not tiled; The third layer: the first and second areas are both paved at 90 degrees, and the third area is not paved; The 4th layer: The first, second and third areas are all paved along +45 degrees; The fifth layer: the second area is tiled along 90 degrees, and the first and third areas are not tiled; Layer 6: The first and second areas are both paved along 0 degrees, and the third area is not paved; Layer 7: The first, second and third areas are all paved along 0 degrees; 8th layer: The second area is paved along +45 degrees, and the first and third areas are not paved; 9th layer: The second area is paved along +45 degrees, and the first and third areas are not paved; 10th layer: The first, second and third areas are all paved along 0 degrees; 11th layer: The first and second areas are paved along 0 degrees, and the third area is not paved; Layer 12: The second area is tiled along a 90-degree angle, and the first and third areas are not tiled; 13th layer: The first, second and third areas are all paved along +45 degrees; 14th layer: The first and second areas are paved at 90 degrees, and the third area is not paved; 15th layer: The first and second areas are paved at 90 degrees, and the third area is not paved; 16th layer: The first, second and third areas are all paved along 0 degrees.

3. The composite rod forming method combining autoclave and dry winding as claimed in claim 1, characterized in that: In the step 1), the release agent used is RM-1937. After the release agent is applied, it is left to air for more than 15 minutes and repeatedly applied three times.

4. The composite rod forming method combining autoclave and dry winding as claimed in claim 1, characterized in that: In step 3), before pressurization, the surface of the tie rod is wrapped with a release cloth, a non-porous isolation film, a breathable felt, and a vacuum bag film in sequence, and the vacuum bag is sealed with a pressure-sensitive tape. The pressurization pressure is 1 bar to 20 bar, and the curing temperature is 100-150° C. and the curing time is 1-15 hours.

5. The composite rod forming method combining autoclave and dry winding as claimed in claim 1, characterized in that: In step 6), the prepreg yarn / prepreg tape is made of carbon fiber and epoxy resin, and the width of the prepreg yarn / prepreg tape is 5-12 mm; the tension during winding is 20-30 N, the heating temperature of the heating device is 50-60° C., and the heating method is hot air, infrared, ultrasonic or hot roller, and a temperature measurement and control system is installed.

6. The composite rod forming method combining autoclave and dry winding as claimed in claim 5, characterized in that: In the step 6), local fiber winding thickening is performed at the bushing joint position at an angle of 85-89 degrees, with a thickness of 2-3 mm, and the winding geodesic angle and layup are [±45] 2s.

7. The composite rod forming method combining autoclave and dry winding as claimed in claim 1, characterized in that: In step 7), the curing temperature is 100-150° C., the heating rate is 2° C. / min, and the curing time is 4-6 hours.

8. The composite rod forming method combining autoclave and dry winding as claimed in claim 1, characterized in that: In the step 8), sandpaper is used for polishing, and the mesh number of the sandpaper is 50-200.

9. The composite rod forming method combining autoclave and dry winding as claimed in claim 1, characterized in that: In the step 9), cleaning is required after polishing. Ethyl acetate or acetone is used as a cleaning agent for cleaning. After cleaning, epoxy resin glue is applied to the surface.

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