Composite toughened rod and its forming method and mold

Abstract

The present application relates to a kind of composite toughening thin stick and its forming method and mould, specifically relates to a kind of forming method and its forming mould for the composite thin stick of laminated board for toughening high-temperature forming.The forming process includes the following steps: first, high-performance fiber bundle is twisted and plied with water-soluble polyvinyl alcohol fiber, and is held to form a bundle of hybrid fiber bundle;Second, the hybrid fiber bundle is immersed in resin by passing through the resin tank containing polyethylene glycol aqueous solution;Third, the hybrid fiber bundle immersed in resin is made into regular shape by passing through the three-section forming mould with equal cross-section through hole;Fourth, after the hybrid fiber bundle is pulled out from the mould hole, it is heated and dried, and the moisture is evaporated, so that it is hardened into thin stick material.The forming method of the composite toughening thin stick of the present application solves the problem of difficult impregnation of polyvinyl alcohol by means of twisting, multi-section mould and polyethylene glycol solution resin promoter, thereby improving the toughening effect of the composite thin stick.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of manufacturing composite rods, in particular to a molding method of composite rods for toughening high-temperature molded laminates and a molding die thereof. BACKGROUND

[0002] Composite rod toughening technology is a new technology for improving the interlaminar performance of composite materials developed in recent years. It realizes the toughening effect by implanting composite rods into the thickness direction of the laminated composite. Since the rods can be bonded with the laminates during the molding process and play a bridging role, this technology can significantly enhance the interlaminar performance of the composite material, and has a low cost, which has been applied in engineering practice and achieved good results.

[0003] The traditional composite toughening rod material is fiber-reinforced epoxy resin or bismaleimide resin. Epoxy resin or bismaleimide resin is not suitable for high-temperature molded composites because the matrix of the rod will crack under high temperature during the composite molding process, and the solid products of the cracking of epoxy resin or bismaleimide resin will be left between the rod fibers and the matrix of the laminates. The presence of residues will cause defects in the material, thereby affecting the performance of the toughened material. In order to solve this problem, the problem of residue of the toughening rod matrix must be solved, and in addition, if a new material is used as the matrix resin of the rod, the problems of infiltration and molding also need to be solved. SUMMARY

[0004] In view of the above problems, the present application aims to provide a composite toughening rod which is high-temperature molded and has very little solid residue after the cracking of the resin matrix, and a molding method thereof. The present application innovatively uses polyethylene glycol and polyvinyl alcohol as the matrix resin as the matrix material of the toughening rod. After high temperature, there is very little solid residue, and the method of twisting and plying the high-performance fiber bundle and the water-soluble polyvinyl alcohol fiber bundle to infiltrate the polyethylene glycol aqueous solution is used to achieve better infiltration, solving the problem of difficulty in infiltrating the fiber bundle due to the high viscosity of polyvinyl alcohol. The molding of the composite rod is realized through a grooved die, solving the problem of lack of glue in the twisted fiber bundle. The present application is simple, practical and easy to realize automation.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions to realize it: a molding method of a composite toughening rod, characterized in that the method comprises the following steps:

[0006] First, twist and ply the high-performance fiber bundle and the water-soluble polyvinyl alcohol fiber respectively, so that the two fibers are held together to form a bundle of hybrid fiber bundles.

[0007] Second, the mixed fiber bundles are passed through a resin tank containing an aqueous solution of polyethylene glycol to impregnate the resin.

[0008] Third, the resin-impregnated fiber bundles pass through a molding die with a uniform cross-section through hole having the desired fine rod cross-section shape, so that the cross-section of the resin-impregnated mixed fiber bundles is of a regular shape.

[0009] Fourth, after the mixed fiber bundles are pulled out of the mold channel, they are heated and dried to evaporate the moisture and harden them into thin rod materials.

[0010] In this invention, the resin temperature in the impregnation tank should be controlled between 60°C and 100°C to allow the polyethylene glycol (PEG) to melt. As the hybrid fiber bundle passes through the resin tank, on the one hand, the molten PEG can enter between the fibers of the high-performance fiber bundle, impregnating the high-performance fiber bundle with PEG; on the other hand, the water-soluble polyvinyl alcohol (PVA) fibers twisted with the high-performance fiber bundle will gradually absorb moisture from the resin tank, changing from a solid to a liquid state. Simultaneously, due to the twisting and binding effect of the hybrid fiber bundle, part of the traction force on the hybrid fiber bundle will be decomposed into centripetal force, causing the PVA solution, which has changed from a solid to a liquid state, to be squeezed and impregnated into the high-performance fiber bundle, thereby achieving the impregnation of the high-performance fiber bundle with PVA.

[0011] The reason this invention uses polyvinyl alcohol (PVA) and polyethylene glycol (PEG) as the matrix resins for the Z-pin is that, under high temperatures, the vast majority of the decomposition products of these two materials are gaseous, with very little solid residue. This improves the interfacial properties between the toughened rods and the laminate, preventing defects between them. While PVA possesses excellent properties and high toughness, its high viscosity makes it unsuitable for wetting. Therefore, a PEG solution is incorporated to promote the wetting of PVA.

[0012] Compared with existing molding dies, the molding die used in this invention includes at least three paths along the stretching direction of the mixed fiber bundle. The first section is conical, which can gradually reduce the excess resin carried by the fiber bundle. The third section has the desired cross-sectional shape of a fine rod. The middle section is based on the structure of the third section, and has at least three grooves or hollow structures along the circumference. This allows it to provide pressure to maintain the shape of the fiber bundle and to replenish resin at the concave positions of the twisted fiber bundle, preventing local material shortage caused by twisting.

[0013] The mold can be made of high-temperature resistant resin or metal, and can be produced by 3D printing.

[0014] If the mold adopts a hollow design, the length of the cavity in the hollow area along the direction of movement of the mixed fiber bundle can be greater than the length of the hollow surface in contact with the fiber, so as to store more resin and facilitate full impregnation of the fiber. This structure enables the mixed fiber bundle to be fully impregnated with polyethylene glycol resin when it is shaped in the mold, thereby greatly improving the performance of the product.

[0015] The through holes with equal cross-sections in molds are mostly round holes, with a diameter typically ranging from 0.1 to 3 mm.

[0016] High-performance fiber materials can include carbon fiber, quartz fiber, basalt fiber, hemp, and other high-performance fibers. Water-soluble polyvinyl alcohol (PVA) fibers are preferably those that readily dissolve in water at low temperatures. Compared to using a single high-performance fiber bundle as a reinforcing material, in this invention, the twisted PVA fibers in the hybrid fiber bundle transform into a liquid state under the high temperature during the molding process. Simultaneously, due to the twisting and binding effect between the high-performance fiber bundle and the PVA fiber bundle, the traction force is converted into a centripetal force for the liquid PVA to impregnate the high-performance fiber bundle, allowing it to penetrate more extensively into the interior of the high-performance fiber. This significantly improves the wetting effect of the PVA resin and solves the problem of high viscosity and difficulty in wetting of PVA in the toughened fine rods of the composite material. Furthermore, the water absorbed by the PVA exists in the aqueous solution of polyethylene glycol (PEG). PEG itself can melt into a liquid state between 60 and 100°C. Its fusion with the dissolved PVA also reduces the viscosity of the PVA, promoting PVA wetting. Therefore, the aqueous solution of PEG acts as both the wetting resin solution for the fine rods and an accelerator for promoting PVA wetting.

[0017] As the polyvinyl alcohol fibers in the hybrid fiber bundle will fuse with water to form liquid resin during the impregnation process and transform into the matrix material of composite fine rod carbon fiber, the hybrid fiber bundle will change from a state of two strands combined to a state of a single fiber bundle containing twist after impregnation.

[0018] The molding method of this invention will ultimately yield high-performance fiber-reinforced polyvinyl alcohol / polyethylene glycol composite rods.

[0019] The key to the performance of composite material rod products lies in ensuring sufficient resin impregnation of the fiber bundles during the preparation process, including resin impregnation inside and outside the fiber bundles. To this end, the resin tank of this invention is equipped with a roller. When the fiber bundles are pulled forward in the resin tank, the roller applies pressure to the fiber bundles, thereby enhancing the resin impregnation effect on the fiber bundle surface and improving the performance of the product. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of two types of fibers twisted into a hybrid fiber bundle in the composite toughening rod of Embodiment 1 of the present invention.

[0021] Figure 2 This is a schematic diagram of the resin impregnation and molding process of composite toughened fine rods mixed with fiber bundles in Embodiment 1 of the present invention.

[0022] Figure 3 This is a schematic diagram of the molding die for the groove structure of the composite toughened thin rod in Embodiment 1 of the present invention.

[0023] Figure 4 This is a schematic diagram of the hollow structure molding die for toughened thin rods made of composite materials in Embodiment 2 of the present invention. Detailed Implementation

[0024] The following describes in detail the implementation examples of the present invention with reference to the accompanying drawings.

[0025] Example 1

[0026] This implementation case takes the manufacture of carbon fiber reinforced polyvinyl alcohol / polyethylene glycol composite material rods as an example. The manufactured carbon fiber composite material rods have a circular cross-section and a diameter of 0.60 mm. The specific implementation steps are as follows:

[0027] First, a bundle of 3K T300 carbon fiber 101 with a twist of 4 twists / cm and a bundle of water-soluble polyvinyl alcohol fiber 102 with a twist of 4 twists / cm and a fineness of 60 denier are twisted together to form a hybrid fiber bundle 100 with a twist of 3 twists / cm. Figure 1 As shown.

[0028] Second, the mixed fiber bundle 100 is passed through a resin tank 200 containing a polyethylene glycol aqueous solution 201, wherein the polyethylene glycol concentration is 70%. A roller 202 in the middle of the resin tank 200 applies pressure to the fiber bundle 100. Under the traction force of the roller 600, the mixed fiber bundle is continuously pulled, achieving continuous impregnation and molding. The pulling speed is 0.2 meters per minute. Figure 2 As shown. The resin temperature in the tank should be controlled at 80℃. This temperature keeps the polyethylene glycol in a molten state and gives the solution a low viscosity to achieve polyethylene glycol impregnation. In addition, as the mixed fiber bundles move in the resin tank, the polyvinyl alcohol fibers that are bound together with the carbon fibers will gradually absorb the water from the polyethylene glycol aqueous solution in the resin tank, changing from a fibrous solid to a liquid state.

[0029] Under the continuous traction of the mixed fiber bundle, due to the twisting and binding effect with the carbon fiber, part of the traction force will be decomposed into the centripetal force inside the fiber bundle. This centripetal force will provide the extrusion force for the molten polyvinyl alcohol to impregnate into the carbon fiber bundle, thereby realizing the impregnation of the carbon fiber with polyvinyl alcohol.

[0030] Third, the resin-impregnated fiber bundles are passed through a molding die 300 with a 0.60mm diameter circular hole, resulting in a regular circular cross-section for the resin-impregnated mixed fiber bundles. The die 300 is made of high-temperature resistant resin and is manufactured using 3D printing. The structure of the die 300 is as follows... Figure 3 As shown, it includes three paths along the stretching direction of the mixed fiber bundle. The first section 301 is conical, which can gradually reduce the excess resin carried by the fiber bundle. The third section 303 is a circular through hole with a diameter of 0.60 mm and a uniform cross-section. The middle section 302 is based on the structure of the third section, with three annular grooves along the circumference. This allows it to provide pressure to maintain the shape of the fiber bundle and to replenish resin at the concave positions of the twisted fiber bundle, preventing local material shortage caused by twisting.

[0031] Fourth, the impregnated and shaped mixed fiber bundles are pulled out from the mold channel and then dried through a heating pipe 400 at a temperature of 110°C. The pipe is 2 meters long, allowing the moisture to evaporate and resulting in a hardened fine rod material 500. Finally, the composite toughened fine rods are wound onto a roll 600 for storage.

[0032] Example 2

[0033] Example 2 is basically the same as Example 1, except that the structure of the molding die in the third step is different:

[0034] The second section of the molding die 700 is a hollow structure 701, the structure of which is shown in the figure below. Figure 4 As shown.

[0035] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the claims. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that non-essential modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the essence of the technical solutions of the present invention and should all be within the scope of protection of the claims of the present invention.

Claims

1. A method for forming a toughened thin rod of composite material, characterized in that: First, high-performance fiber bundles and water-soluble polyvinyl alcohol fibers are twisted and then bonded together to form a hybrid fiber bundle. Second, the hybrid fiber bundle is impregnated in a resin bath containing a polyethylene glycol aqueous solution. The resin temperature in the bath should be controlled between 60°C and 100°C to allow the polyethylene glycol to melt. During the process of passing through the resin bath, the molten polyethylene glycol can penetrate between the fibers of the high-performance fiber bundle, impregnating the high-performance fiber bundle. Simultaneously, the water-soluble polyvinyl alcohol fibers bonded with the high-performance fiber bundle will gradually absorb the molten polyethylene glycol. The water in the resin bath will change from solid to liquid. At the same time, due to the twisting and binding of the mixed fiber bundles, part of the traction force on the mixed fiber bundles will be decomposed into centripetal force, causing the polyvinyl alcohol solution, which has changed from solid to liquid, to be squeezed and impregnated into the high-performance fiber bundles, thereby realizing the impregnation of high-performance fiber bundles by polyvinyl alcohol. Third, the fiber bundles impregnated with resin pass through a molding die with a uniform cross-section through hole having the desired cross-sectional shape of fine rods, so that the cross-section of the resin-impregnated mixed fiber bundles has a regular shape. Fourth, after the mixed fiber bundles are pulled out from the die hole, they are heated and dried to evaporate the water and harden them into fine rod materials.

2. The molding method of a composite toughened thin rod as described in claim 1, characterized in that: The molding die includes at least three paths along the stretching direction of the mixed fiber bundle. The first path is conical, which can gradually reduce the excess resin carried by the fiber bundle. The third path is a through hole with a uniform cross-section and the desired fine rod cross-section shape. The middle path is based on the third path and has at least three grooves or hollow structures along the circumference. This allows it to provide pressure to maintain the shape of the fiber bundle and to replenish resin to the recessed positions of the twisted fiber bundle, preventing local material shortage caused by twisting.

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