Forming method of carbon fiber stepped shaft

Abstract

The invention discloses a forming method of a carbon fiber stepped shaft, and relates to the technical field of shaft forming, and the forming method comprises the following steps: preparing a stepped shaft sand core: forming and demolding in a sand core mold to obtain the stepped shaft sand core; carbon fiber prepreg cloth is laid on the outer wall of the stepped shaft sand core, pressure maintaining and curing are conducted, and a preformed stepped shaft is obtained; and demolding and forming: demolding the preformed stepped shaft from the stepped shaft sand core to obtain a formed stepped shaft. According to the forming method of the carbon fiber stepped shaft, the integrity and the overall strength of the carbon fiber stepped shaft are improved, and the overall weight can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of shaft molding, and in particular to a molding method of a carbon fiber stepped shaft. Background Art

[0002] A shaft is a mechanical part used for supporting, rotating and transmitting power, and is commonly used in mechanical equipment, automobiles, motor vehicles, ships and other fields. Metal shafts are generally heavier due to the high density of metal materials, resulting in excessive weight of the equipment, and the service life of the metal shaft will be greatly reduced in high temperature and high humidity environments. Carbon fiber shafts are increasingly widely used in the field of engineering machinery technology due to their high strength, light weight, good wear resistance, corrosion resistance and fatigue resistance.

[0003] At present, carbon fiber stepped shafts with different cross-sectional sizes are mostly assembled from multiple carbon fiber shafts with different cross-sectional sizes through metal connectors, and mechanical processing and drilling are necessary during assembly, which not only affects the strength of the original carbon fiber shaft, but also the integrity of the stepped shaft after assembly is not high and the weight is also increased, which is relatively energy-consuming for some large mechanical equipment. Summary of the invention

[0004] The purpose of the present invention is to provide a method for forming a carbon fiber stepped shaft to solve the problems existing in the above-mentioned prior art, improve the integrity and overall strength of the carbon fiber stepped shaft, and reduce the overall weight.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a method for forming a carbon fiber stepped shaft, comprising the following steps:

[0007] Preparing a stepped shaft sand core: molding and demoulding in a sand core mold to obtain the stepped shaft sand core;

[0008] Preforming: laying carbon fiber prepreg on the outer wall of the stepped shaft sand core, and performing pressure-maintaining curing to obtain a preformed stepped shaft;

[0009] Demolding: Demolding the preformed stepped shaft from the stepped shaft sand core to obtain a formed stepped shaft.

[0010] Preferably, in the step of preparing the stepped shaft sand core, the sand core mold has a plurality of sand core cavities along the axial direction, and adjacent sand core cavities have different cross-sectional sizes. The sand core cavities are used to fill the prefabricated sand cores, and the sand core mold filled with the prefabricated sand cores is solidified, and then demolded and the prefabricated sand cores are polished to obtain the stepped shaft sand core.

[0011] Preferably, in the step of preparing the stepped shaft sand core, the adjacent sand core cavities of the sand core mold can be detachably connected, and each of the sand core cavities includes a plurality of sub-cavities that can be detachably connected along the circumferential direction; and covers are detachably provided at both ends of the sand core mold.

[0012] Preferably, in the step of preparing the step shaft sand core, a demoulding cloth is laid on the inner wall of each sand core cavity, and the prefabricated sand core is filled and compacted in turn in each sand core cavity, and a core shaft for fixing the prefabricated sand core in each sand core cavity is coaxially arranged in the sand core mold; the sand core mold filled with the prefabricated sand core is cured, and then the sand core mold is removed to demould and the prefabricated sand core is polished to obtain the step shaft sand core.

[0013] Preferably, in the preforming step, an inner demoulding cloth is firstly laid on the periphery of the step shaft sand core, and then the carbon fiber prepreg is laid on the periphery of the inner demoulding cloth, and an outer demoulding cloth is laid on the periphery of the carbon fiber prepreg, and the whole is pressure-maintained and cured to obtain the preformed step shaft.

[0014] Preferably, in the preforming step, the carbon fiber prepreg is respectively laid on each shoulder and each shaft body of the stepped shaft sand core, and the outer circle and inner circle of the carbon fiber prepreg laid on the shoulder are provided with a circumferential overlap portion, and the circumferential overlap portion is used to overlap with the carbon fiber prepreg laid outside the adjacent shaft body.

[0015] Preferably, the circumferential overlapping portions each include a plurality of circumferentially distributed serrations, and each of the serrations is used for overlapping with the carbon fiber prepreg coated outside the adjacent shaft body.

[0016] Preferably, in the preforming step, multiple layers of the carbon fiber prepreg are laid outside the stepped shaft sand core, and the circumferential overlap portion at each shaft shoulder is overlapped with the carbon fiber prepreg laid outside the adjacent shaft body in sequence; and the circumferential overlap portions between two adjacent layers are staggered.

[0017] Preferably, during the preforming step, vacuum bag is used for vacuuming and pressure maintenance.

[0018] Preferably, the prefabricated sand core is a water-soluble sand core; in the demolding step, the stepped shaft sand core with the preformed stepped shaft is immersed in water, and the stepped shaft sand core is washed away by water flow to demold the preformed stepped shaft, and then processed to obtain the formed stepped shaft.

[0019] Compared with the prior art, the present invention has achieved the following technical effects:

[0020] The forming method of the carbon fiber step shaft provided by the present invention first prepares a step shaft sand core by means of a sand core mold, then lays a carbon fiber prepreg cloth outside the step shaft sand core, obtains an integrated preformed step shaft after pressure holding and curing, and then demolds the preformed step shaft to obtain a formed step shaft. In this way, the carbon fiber step shaft is formed in one piece without the need for metal connectors to assemble, thereby improving the integrity and overall strength of the carbon fiber step shaft and being able to reduce the overall weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic structural diagram of a sand core mold provided in Example 1;

[0023] Figure 2 A schematic diagram of the structure of a stepped shaft sand core provided in Example 1;

[0024] Figure 3 A schematic diagram of the structure of the pressing roller table provided in Example 1;

[0025] Figure 4 This is a corresponding diagram of the laying of carbon fiber prepreg at the shoulder provided in Example 1.

[0026] In the figure: 1-sand core mold; 11-sand core cavity; 12-sub-cavity; 13-cover; 14-core shaft; 2-step shaft sand core; 21-shaft shoulder; 22-shaft body; 3-carbon fiber prepreg cloth; 31-circumferential overlap portion; 32-serrated portion; 4-pressing roller table; 41-step. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The purpose of the present invention is to provide a method for forming a carbon fiber stepped shaft to solve the problems existing in the above-mentioned prior art, improve the integrity and overall strength of the carbon fiber stepped shaft, and reduce the overall weight.

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Embodiment 1

[0031] This embodiment provides a method for forming a carbon fiber stepped shaft, comprising the following steps:

[0032] Preparation of a stepped shaft sand core: forming and demoulding in a sand core mold 1 to obtain a stepped shaft sand core 2;

[0033] Preforming: laying carbon fiber prepreg 3 on the outer wall of the step shaft sand core 2, and performing pressure-maintaining curing to obtain a preformed step shaft;

[0034] Demolding: Demolding the preformed stepped shaft from the stepped shaft sand core 2 to obtain a formed stepped shaft.

[0035] Among them, a step shaft sand core 2 is prepared by a sand core mold 1, and then a carbon fiber prepreg cloth 3 is laid outside the step shaft sand core 2, and an integrated preformed step shaft is obtained after pressure holding and curing, and then the preformed step shaft is demolded to obtain a formed step shaft. In this way, the carbon fiber step shaft is formed in one piece, and no metal connectors are required for assembly, which improves the integrity and overall strength of the carbon fiber step shaft and can reduce the overall weight.

[0036] Among the optional solutions of this embodiment, it is more preferred to refer to Figure 1 In the step of preparing the step shaft sand core, the sand core mold 1 has a plurality of sand core cavities 11 along the axial direction, and the adjacent sand core cavities 11 have different cross-sectional sizes. The sand core cavities 11 are used to fill the prefabricated sand core, and the sand core mold 1 filled with the prefabricated sand core is solidified, and then the mold is demoulded and the prefabricated sand core is polished to obtain the step shaft sand core 2, such as Figure 2 As shown; the number and inner diameter of the sand core cavities 11 of the sand core mold 1 are determined according to the size of the actual molded step shaft, the number of the sand core cavities 11 should be the same as the step segments of the molded step shaft, and the inner diameter of the sand core cavity 11 should be smaller than the corresponding size of the molded step shaft, so that the required carbon fiber step shaft size can be achieved after the subsequent laying of the carbon fiber prepreg 3.

[0037] In the optional scheme of this embodiment, it is more preferred that in the step of preparing the stepped shaft sand core, adjacent sand core cavities 11 of the sand core mold 1 can be detachably connected, and each sand core cavity 11 includes a plurality of sub-cavities 12 that can be detachably connected along the circumferential direction; and covers 13 are detachably provided at both ends of the sand core mold 1; adjacent sub-cavities 12 and adjacent sand core cavities 11 are detachably connected by bolts, which facilitates disassembly and demolding.

[0038] In the optional scheme of this embodiment, it is more preferred that in the step of preparing the stepped shaft sand core, a demoulding cloth is laid on the inner wall of each sand core cavity 11, and the prefabricated sand core is filled and compacted in each sand core cavity 11 in turn, and a core shaft 14 for fixing the prefabricated sand core in each sand core cavity 11 is coaxially arranged in the sand core mold 1; the sand core mold 1 filled with the prefabricated sand core is cured, and then the sand core mold 1 is removed to demould and the prefabricated sand core is polished to obtain the stepped shaft sand core 2.

[0039] The demoulding of the prefabricated step shaft sand core 2 is facilitated by laying the demoulding cloth. First, a layer of demoulding cloth is pasted inside the sub-cavity 12 of each sand core cavity 11, and then the cover 13 on one side is assembled with the sand core cavity 11 on one side by bolts, and the core shaft 14 and the cover 13 are connected with bolts, and the prepared prefabricated sand core is filled into the sand core cavity 11 and tamped, and then the other sand core cavities 11 are assembled in sequence, and the prepared prefabricated sand core is filled into the sand core cavity 11 and tamped; finally, the cover 13 on the other side is assembled; then the sand core mold 1 filled with the prefabricated sand core is placed in a curing furnace for heating and curing, and cured at 150°C for 20 hours, and then the sand core mold 1 is removed to obtain the step shaft sand core 2, and the surface of the step shaft sand core 2 is polished and trimmed to be flat, as shown in FIG. Figure 2 The mandrel 14 can increase the fracture resistance of the stepped shaft sand core 2 and also facilitates the handling.

[0040] In the optional scheme of this embodiment, it is more preferred that in the preforming step, firstly, an inner demoulding cloth is laid on the outer periphery of the step shaft sand core 2, and then the carbon fiber prepreg cloth 3 is laid on the outer periphery of the inner demoulding cloth, and the outer demoulding cloth is laid on the outer periphery of the carbon fiber prepreg cloth 3, and the whole is pressure-maintained and cured to obtain a preformed step shaft; by laying the inner demoulding cloth and the outer demoulding cloth, the subsequent demoulding of the carbon fiber prepreg cloth 3 is facilitated, and the prefabricated sand core is prevented from affecting the molding surface quality of the carbon fiber prepreg cloth 3.

[0041] In the optional solutions of this embodiment, it is more preferred that Figure 4 As shown, in the preforming step, a carbon fiber prepreg 3 is respectively laid on each shoulder 21 and each shaft body 22 of the stepped shaft sand core 2, and the outer circle and inner circle of the carbon fiber prepreg 3 laid on the shoulder 21 are provided with a circumferential overlap portion 31, and the circumferential overlap portion 31 is used to overlap with the carbon fiber prepreg 3 laid on the outside of the adjacent shaft body 22. By laying the carbon fiber prepreg 3 on the shoulder 21 and each shaft body 22 and overlapping and fixing them, it is convenient to control the laying quality of the carbon fiber prepreg 3 at the outer circle and inner circle of the shoulder 21 to avoid excessive accumulation.

[0042] In the optional scheme of this embodiment, it is more preferred that when the carbon fiber prepreg 3 at the outer circle and the inner circle of the shoulder 21 are stacked, it is necessary to consider the overlap with the two adjacent shaft bodies 22. Not only is it necessary to have sufficient connection strength, but also to avoid wrinkling during stacking to prevent excessive local accumulation. Therefore, the circumferential overlap portion 31 includes a plurality of circumferentially distributed serrations 32, each serration 32 is used to overlap with the carbon fiber prepreg 3 laid on the outside of the adjacent shaft body 22. The advantage of the serration 32 is that the connection between the shoulder 21 and the shaft body 22 has the largest overlap area. As the overlap position of the carbon fiber prepreg 3 on the shoulder 21 and the shaft body 22 changes, the overlap area can be reduced, thereby effectively reducing the degree of local accumulation at the overlap.

[0043] In the optional scheme of this embodiment, it is more preferred that in the step preforming, multiple layers of carbon fiber prepreg 3 are laid on the outside of the stepped shaft sand core 2, and the circumferential overlap 31 at each shoulder 21 is overlapped with the carbon fiber prepreg 3 laid on the outside of the adjacent shaft body 22 in sequence, and the overlapping in sequence improves the connection strength; in order to reduce the degree of local accumulation at the overlap between the shaft body 22 and the shoulder 21, the circumferential overlap 31 between the two adjacent layers is staggered, that is, each time the shoulder 21 is laid, half the angle of the sawtooth 32 is rotated at the position of the previous shoulder 21 layer and then laid, so that the overlap is closed circumferentially and local accumulation is reduced. Each time a layer of carbon fiber prepreg 3 is laid, the pores and bubbles therein are scraped out with a scraper.

[0044] Before laying the carbon fiber prepreg 3, the shape and size of the carbon fiber prepreg 3 are pre-cut according to the required size. It should be noted that as the stacking thickness increases, the laying size of the shoulder 21 changes, and the carbon fiber prepreg 3 needs to be adaptively adjusted when unloading. After the carbon fiber prepreg 3 is laid, it is compacted by the pressing roller 4. See Figure 3 The pressing roller table 4 rolls the preformed stepped shaft through the upper and lower plates, wherein the pressing roller table 4 is provided with a plurality of steps 41 adapted to the preformed stepped shaft.

[0045] Among the optional schemes of this embodiment, it is more preferred that in the preforming step, vacuum is drawn and pressure is maintained through a vacuum bag, the vacuum bag is sealed with sealing tape, the uncured carbon fiber step shaft is placed in the vacuum bag, the carbon fiber step shaft is completely wrapped with an external demoulding cloth, and vacuum is drawn and pressure maintained for 30 minutes; then the pressure is continued to be maintained and placed in a curing furnace for curing, and the curing process is to heat up to 80°C for 30 minutes and keep the temperature constant for 1 hour, then heat up to 110°C for 15 minutes and keep the temperature constant for 1 hour, and finally heat up to 135°C for 15 minutes and keep the temperature constant for 2 hours; the pressure holding time and the curing temperature and time can be adjusted according to actual needs.

[0046] In the optional scheme of this embodiment, it is more preferred that the prefabricated sand core adopts a conventional water-soluble sand core; in the demolding step, the stepped shaft sand core 2 with the preformed stepped shaft is immersed in water, and the stepped shaft sand core 2 is washed away by the water flow to demold the preformed stepped shaft, and then processed to obtain a formed stepped shaft.

[0047] The water-soluble sand core is prepared by weighing corresponding quantities of 200-mesh quartz sand, chopped glass fibers with a length of 2 to 3 mm, 200-mesh polyvinyl alcohol powder and water in a ratio of 35:3 to 5:3:1; firstly, the polyvinyl alcohol powder, quartz sand and chopped glass fibers are uniformly stirred at a low speed by a stirrer, and then hot water is poured in and uniformly stirred at a high speed to form a water-soluble sand core; water-soluble sand cores obtained by other conventional material ratios can also be used; by selecting a water-soluble sand core, demolding is facilitated; specifically, after the step shaft sand core 2 is soaked in hot water for 2 hours, the sand core and the inner and outer demolding cloths are washed away with a high-pressure water gun, the core shaft 14 is taken out, and the thickness accumulation of the formed step shaft is polished until the thickness is uniform everywhere, and then it is machined according to the predetermined size to obtain the final required formed step shaft.

[0048] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for forming a carbon fiber stepped shaft, characterized in that: The steps include: Preparation of a stepped shaft sand core: forming and demoulding in a sand core mold (1) to obtain the stepped shaft sand core (2); Preforming: laying a carbon fiber prepreg cloth (3) on the outer wall of the stepped shaft sand core (2), and performing pressure-maintaining curing to obtain a preformed stepped shaft; Demolding and molding: demolding the preformed stepped shaft from the stepped shaft sand core (2) to obtain a molded stepped shaft.

2. The method for forming a carbon fiber stepped shaft according to claim 1, characterized in that: In the step of preparing a stepped shaft sand core, the sand core mold (1) has a plurality of sand core cavities (11) along the axial direction, and adjacent sand core cavities (11) have different cross-sectional sizes. The sand core cavities (11) are used to fill the prefabricated sand cores, and the sand core mold (1) filled with the prefabricated sand cores is solidified, and then demoulding and grinding of the prefabricated sand cores are carried out to obtain the stepped shaft sand core (2).

3. The method for forming a carbon fiber stepped shaft according to claim 2, characterized in that: In the step of preparing a stepped shaft sand core, the adjacent sand core cavities (11) of the sand core mold (1) can be detachably connected, and each of the sand core cavities (11) includes a plurality of sub-cavities (12) that can be detachably connected along the circumferential direction; and covers (13) are detachably provided at both ends of the sand core mold (1).

4. The method for forming a carbon fiber stepped shaft according to claim 3, characterized in that: In the step of preparing the step shaft sand core, a demoulding cloth is laid on the inner wall of each sand core cavity (11), and the prefabricated sand core is filled and compacted in each sand core cavity (11) in turn, and a core shaft (14) is coaxially arranged in the sand core mold (1) to fix and penetrate the prefabricated sand core in each sand core cavity (11); the sand core mold (1) filled with the prefabricated sand core is solidified, and then the sand core mold (1) is removed to demould and the prefabricated sand core is polished to obtain the step shaft sand core (2).

5. The method for forming a carbon fiber stepped shaft according to claim 1, characterized in that: In the preforming step, firstly, an inner demoulding cloth is laid on the periphery of the step shaft sand core (2), then the carbon fiber prepreg cloth (3) is laid on the periphery of the inner demoulding cloth, and an outer demoulding cloth is laid on the periphery of the carbon fiber prepreg cloth (3), and the whole is pressure-maintained and cured to obtain the preformed step shaft.

6. The method for forming a carbon fiber stepped shaft according to claim 5, characterized in that: In the preforming step, the carbon fiber prepreg (3) is laid on each shoulder (21) and each shaft body (22) of the stepped shaft sand core (2), and the outer circle and inner circle of the carbon fiber prepreg (3) laid on the shoulder (21) are both provided with a circumferential overlap portion (31), and the circumferential overlap portion (31) is used to overlap with the carbon fiber prepreg (3) laid on the outside of the adjacent shaft body (22).

7. The method for forming a carbon fiber stepped shaft according to claim 6, characterized in that: The circumferential overlapping portions (31) each include a plurality of circumferentially distributed sawtooth portions (32), and each of the sawtooth portions (32) is used to overlap with the carbon fiber prepreg (3) laid outside the adjacent shaft body (22).

8. The method for forming a carbon fiber stepped shaft according to claim 7, characterized in that: In the preforming step, multiple layers of the carbon fiber prepreg (3) are laid outside the stepped shaft sand core (2), and the circumferential overlap portion (31) at each shaft shoulder (21) is overlapped with the carbon fiber prepreg (3) laid outside the adjacent shaft body (22) in sequence; and the circumferential overlap portions (31) between two adjacent layers are arranged in an alternating manner.

9. The method for forming a carbon fiber stepped shaft according to claim 1, characterized in that: During the preforming step, vacuum bag is used for vacuuming and pressure maintenance.

10. The method for forming a carbon fiber stepped shaft according to claim 2, characterized in that: The prefabricated sand core is a water-soluble sand core; in the demoulding and molding step, the stepped shaft sand core (2) with the preformed stepped shaft is immersed in water, and the stepped shaft sand core (2) is washed away by water flow, so that the preformed stepped shaft is demoulded, and then processed to obtain the formed stepped shaft.

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