A composite material thick wall tube and preparation method thereof

Abstract

The invention discloses a composite material thick-walled tube and a preparation method thereof, belonging to the technical field of composite materials. By winding three winding groups in different directions, a polyester surface felt is added between two adjacent winding groups, the interface shear strength is increased, the overall strength of the thick-walled tube is improved, and interface cracking is avoided. The use of nano-toughening materials improves the toughness of the resin system, which is conducive to preventing crack propagation caused by stress release during the curing process of the product. The invention can solve the problem of interface cracking of thick-walled tubes during one-time curing molding.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and in particular relates to a composite material thick-walled tube and a preparation method thereof. Background Art

[0002] At present, winding process is a common process method in composite material molding, and has been widely used in the molding of composite chemical pipelines, pressure vessels, storage tanks, rocket launch tubes, torpedo tubes and other products. When winding thick-walled tubular products, in order to ensure product quality, it is generally necessary to use multiple winding and layered curing processes, that is, first winding a certain thickness of resin-impregnated fiber on the core mold, solidifying it, and then winding it a second time to solidify it until the product thickness reaches the design requirements. Although this molding method can meet the actual use requirements, the production efficiency is low, multiple windings require multiple curings, and there are many process requirements in the winding process, and the energy consumption is large, which greatly increases the manufacturing cost of the product.

[0003] In the prior art, patent CN106531378A discloses a method for manufacturing a solid cylinder, CN106158170A discloses a method for preparing an insulator core rod, and CN106448958A discloses a dry yarn-wound preform, an insulator core rod, and a preparation method. These three patents propose a method for preparing a solid insulator core rod, and the preform is prepared by dry yarn fiber winding or fabric laying, and then vacuum infusion molding is used for one-time curing, but none of them discloses a composite material thick-walled tube, and the problem of cracking of the thick-walled tube interface during one-time curing molding is solved. Therefore, in view of the above shortcomings, it is very necessary to provide an efficient method for preparing a composite material thick-walled tube. Summary of the invention

[0004] The purpose of the present invention is to provide a composite material thick-walled tube and a preparation method thereof, which can solve the problem of interface cracking of the thick-walled tube during one-step solidification molding.

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

[0006] A method for preparing a composite material thick-walled tube comprises the following steps:

[0007] 1) Weaving one or both of fiber yarn and fiber fabric with reinforcing fibers not impregnated with resin;

[0008] 2) Using a metal core shaft as a mold, spraying a release agent evenly on the surface of the mold, and then winding one or two of fiber yarn and fiber fabric on the outside of the mold, with no limit on the ratio when two, the winding method includes a first winding group, a second winding group and a third winding group, the first winding group is warp winding, the second winding group is weft winding, the third winding group is ±45° winding, and a layer of polyester surface felt is respectively provided between the first winding group and the second winding group and between the second winding group and the third winding group to form a fiber preform;

[0009] 3) weighing epoxy resin, diluent, nano toughening material, accelerator and curing agent and mixing them evenly to obtain an epoxy resin solution;

[0010] 4) The mold is closed and locked, and the epoxy resin solution is injected into the mold cavity to infiltrate the fiber preform, and a composite material thick-walled tube is prepared by adopting RTM process (vacuum injection molding process) or SCRIMP process (vacuum assisted resin transfer molding process).

[0011] Preferably, the reinforcing fiber is one or a mixed fiber of carbon fiber, glass fiber, basalt fiber, quartz fiber.

[0012] Preferably, the weaving method is one of plain weave, uniaxial weave, biaxial weave, multiaxial weave, satin weave and twill weave.

[0013] Preferably, the mold release agent is evenly sprayed on the mold surface for 3 times, with a time interval of more than 15 minutes between each spraying.

[0014] Preferably, the mass fractions of the reinforcing fiber and the epoxy resin are 60% to 80% and 20% to 40% respectively.

[0015] Preferably, the mass fractions of the epoxy resin, diluent, nano-toughening material, accelerator and curing agent are 100%, 5% to 25%, 3% to 10%, 1% to 5% and 80% to 150% respectively.

[0016] Preferably, the epoxy resin is selected from bisphenol A epoxy resin, bisphenol F epoxy resin, alicyclic multifunctional epoxy resin or a combination thereof; the diluent is selected from glycidyl ether; the accelerator is selected from one of amine accelerators, urea accelerators and imidazole accelerators; the curing agent is selected from one of methyltetrahydrophthalic anhydride and methylhexahydrophthalic anhydride.

[0017] Preferably, the steps of preparing the composite material thick-walled tube by RTM process include:

[0018] The epoxy resin glue is injected into the mold cavity through the glue injection hole at 35-45°C and 0.05-2MPa, and the vacuum degree in the mold cavity is maintained below -0.09MPa;

[0019] After the glue injection is completed, the glue outlet and the glue inlet are closed, and the resin is cured by the heating device of the mold or the mold is placed in an oven. The curing temperature is 90-160°C and the curing time is 8-36 hours, which is carried out in multiple stages.

[0020] After curing is completed, demoulding is performed, and the metal core shaft is taken out to obtain a composite material thick-walled tube.

[0021] Preferably, the steps of preparing the composite thick-walled tube by the SCRIMP process include:

[0022] A plastic guide net is arranged on the outer layer of the fiber preform, and margins are left at both ends of the fiber preform, and the fiber preform is divided into four sections. A spiral tube is wound around the three boundaries and a three-way tube is used to inject glue, and two layers of vacuum bags are laid on the surface in sequence and sealed, and a layer of high-temperature resistant glass fiber felt is laid between the two layers of vacuum bags;

[0023] When injecting glue, first inject the epoxy resin system solution into the middle glue inlet, and when the resin reaches the glue inlets at both ends, inject glue into the three glue inlets at the same time until the fiber preform is completely soaked;

[0024] After the glue injection is completed, the glue outlet and the glue inlet are closed, and the resin is cured by the heating device of the mold or the mold is placed in an oven. The curing temperature is 90-160°C and the curing time is 8-36 hours, which is carried out in multiple stages.

[0025] After curing is completed, demoulding is performed, and the metal core shaft is taken out to obtain a composite material thick-walled tube.

[0026] A composite material thick-walled tube is prepared by the above preparation method.

[0027] The beneficial effects achieved by the present invention are as follows:

[0028] 1) The present invention adopts vacuum injection molding when molding the composite material thick wall tube, the fiber is more fully infiltrated, no bubbles and defects are generated inside, and the interface is well bonded. The fiber content of the preform can be controlled by adjusting the tension during the molding process.

[0029] 2) Add polyester surface felt between two adjacent winding groups to increase the resin content between the winding layers, thereby increasing the interface shear strength, improving the overall strength of the thick-walled tube, and avoiding interface cracking.

[0030] 3) The present invention uses nano-toughening materials to improve the toughness of the resin system, which is beneficial to preventing the crack expansion caused by stress release during the curing process of the product, and solves the one-time curing and molding of the large-thickness product of this patent.

[0031] 4) The composite material thick-walled tube formed by the present invention has a thickness of 20 to 260 mm, a length of 500 to 15000 mm, and a diameter of 300 to 3800 mm. It can be formed in one step, thus avoiding the material waste and high production cost caused by multiple forming.

[0032] 5) The volume content of the composite material thick-walled tube formed by the present invention can reach 65%, and by setting the fiber fabric layer angle, the composite material thick-walled tube is endowed with excellent strength and rigidity and excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the cross-sectional structure of a composite material thick-walled tube proposed by the present invention.

[0034] Figure 2 It is a schematic diagram of the preparation process of the composite material thick-walled tube of the present invention. DETAILED DESCRIPTION

[0035] In order to make the above features and advantages of the present invention more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings.

[0036] Embodiment 1:

[0037] 1) Mold assembly and surface treatment steps: Assemble the end plate and the mandrel, spray the mold release agent evenly on the mold surface, spray 3 times, each time interval is more than 15 minutes, and use it after treatment;

[0038] 2) Winding step: Wind the carbon fiber yarn directly on the diameter A fiber dry yarn preform is formed on a mold with a length of 500 mm; the winding group includes a first winding group of T700 carbon fiber warp winding, a second winding group of T700 carbon fiber weft winding, and a third winding group of T700 carbon fiber ±45° winding. The winding tension is controlled at 80-240 kg in a layer-by-layer decreasing manner, and the thickness ratio of the first winding group, the second winding group, and the third winding group is 6:1:3; a polyester surface felt is added between two adjacent winding group layers to form a fiber preform with a dry yarn thickness of 20 mm.

[0039] 3) placing the dry yarn preform with the winding mold in step 2) in the cavity of the infusion mold and closing the mold;

[0040] 4) bisphenol A epoxy resin, diluent glycidyl ether, nano toughening material, amine accelerator, and curing agent methyltetrahydrophthalic anhydride are uniformly mixed in the proportions of 100%, 5%, 3%, 1%, and 80%, and the epoxy resin system solution is obtained after complete mixing;

[0041] 5) After the mold is closed and locked, the prepared epoxy resin glue is injected into the mold cavity from the injection hole at a temperature of 35°C and a pressure of 2MPa to infiltrate the fiber braided body; during the molding process, the relative vacuum degree in the mold is maintained below -0.09MPa, the resin used for injection is an epoxy resin system solution, the injection speed is 400g / min, and the injection and reflux time is 5h.

[0042] 6) After the glue injection is completed, the glue outlet and the glue inlet are closed, and the resin is cured by the heating device of the mold or in an oven. In this embodiment, the specific curing system is 90° C. for 2 hours, 120° C. for 4 hours, and then 160° C. for 4 hours.

[0043] 7) After curing, clean the injection tube and other auxiliary materials for demoulding, and take out the mandrel to form a composite material thick-walled tube product.

[0044] Figure 1 The schematic diagram of the structure of the prepared composite material thick wall tube product is shown in Figure 2. Figure 2 Schematic diagram of the preparation process of composite thick-walled tube products.

[0045] Embodiment 2:

[0046] 1) Mold assembly and surface treatment steps: Assemble the end plate and the mandrel, spray the mold release agent evenly on the mold surface, spray 3 times, each time interval is more than 15 minutes, and use it after treatment;

[0047] 2) Winding step: Wind the fiber yarn directly on the diameter A carbon fiber dry yarn preform is formed on a mold with a length of 15000 mm; wherein, according to the design requirements of high-rigidity composite material thick-walled tubes, the winding group includes a first winding group of T700 carbon fiber warp winding, a second winding group of M40 carbon fiber weft winding, and a third winding group of T800 carbon fiber ±45° winding; the winding tension is controlled at 80-240 kg in a layer-by-layer decreasing manner, and the thickness ratio of the first winding group, the second winding group, and the third winding group is 6:3:1; the first winding group, the second winding group, and the third winding group are alternately arranged, and a polyester surface felt is added between two adjacent winding group layers to form a fiber preform with a dry yarn thickness of 260 mm.

[0048] 3) uniformly mixing bisphenol A epoxy resin, diluent glycidyl ether, nano toughening material, amine accelerator, and curing agent methyltetrahydrophthalic anhydride according to 100%, 25%, 10%, 5%, and 150%, and completely mixing to obtain an epoxy resin system solution;

[0049] 4) Using vacuum assisted resin transfer molding process (SCRIMP) to form a composite thick-walled tube, the specific steps are as follows:

[0050] a. A plastic guide net is set on the outer layer of the fiber preform as the guide layer medium for the vacuum injection resin. A margin of 200 to 260 mm is left at both ends of the fiber preform. The fiber preform is divided into four sections. The spiral tube is wound around the three boundaries and the glue is injected with a three-way pipe. The first layer of vacuum bag is laid on the surface and sealed. A layer of high-temperature resistant glass fiber felt needs to be laid between the two layers of vacuum bags to achieve a better vacuuming effect.

[0051] b. When pouring, first inject the epoxy resin system solution into the middle inlet, and when the resin reaches the inlets at both ends, pour the resin into the three inlets at the same time. When the glue outlets at both ends are more than 500mm, the pouring is completed and the preform fibers are completely infiltrated.

[0052] c. After the glue injection is completed, the glue outlet and the glue inlet are closed and placed in an oven for curing; the curing system adopts the principle of low-temperature and long-time curing. The specific curing system in this embodiment is 90°C curing for 2h, 120°C curing for 10h, and then 160°C curing for 6h.

[0053] d. After curing, clean up the vacuum bag, injection tube and other auxiliary materials, remove them, demould the metal core mold, and process the surface to form a composite material thick-walled tube product.

[0054] Embodiment three:

[0055] The method is basically the same as Example 1, except that in step 4), bisphenol A epoxy resin, diluent glycidyl ether, nano toughening material, amine accelerator, and curing agent methyltetrahydrophthalic anhydride are uniformly mixed according to 100%, 10%, 5%, 3%, and 100%; in step 5), after the mold is closed and locked, the prepared epoxy resin glue is injected into the mold cavity through the glue injection hole at a temperature of 45° C. and a pressure of 0.05 MPa.

[0056] Embodiment 4:

[0057] The method is basically the same as the first embodiment, except that, after the mold is closed and locked in step 5), the prepared epoxy resin glue is injected into the mold cavity through the glue injection hole at a temperature of 40° C. and a pressure of 1 MPa.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a composite material thick-walled tube, characterized in that: The following steps are involved: Weaving the reinforcing fibers not impregnated with resin into one or both of fiber yarn and fiber fabric; A metal core shaft is used as a mold, a mold release agent is uniformly sprayed on the surface of the mold, and then one or two of fiber yarn and fiber fabric are wound on the outside of the mold, and the ratio of the two is not limited. The winding method includes a first winding group, a second winding group and a third winding group. The first winding group is warp winding, the second winding group is weft winding, and the third winding group is ±45° winding. A layer of polyester surface felt is respectively provided between the first winding group and the second winding group and between the second winding group and the third winding group. The polyester surface felt is used to increase the resin content between the winding layer groups to form a fiber preform; Weigh epoxy resin, diluent, nano toughening material, accelerator and curing agent and mix them evenly to obtain epoxy resin solution; The mold is closed and locked, and the epoxy resin solution is injected into the mold cavity to infiltrate the fiber preform, and a composite material thick-walled tube is prepared by using an RTM process or a SCRIMP process.

2. The preparation method according to claim 1, characterized in that The reinforcing fiber is one or a mixed fiber of carbon fiber, glass fiber, basalt fiber and quartz fiber.

3. The preparation method according to claim 1, characterized in that: The weaving method is one of plain weave, uniaxial weave, biaxial weave, multiaxial weave, satin weave and twill weave.

4. The preparation method according to claim 1, characterized in that: The mold release agent was sprayed evenly on the mold surface for 3 times, with a time interval of more than 15 minutes between each spraying.

5. The preparation method according to claim 1, characterized in that: The mass fractions of the reinforcing fiber and the epoxy resin are 60% to 80% and 20% to 40% respectively.

6. The preparation method according to claim 1, characterized in that: The epoxy resin is selected from one or a combination of bisphenol A epoxy resin, bisphenol F epoxy resin, alicyclic multifunctional epoxy resin; the diluent is selected from glycidyl ether; the accelerator is selected from one of amine accelerators, urea accelerators, and imidazole accelerators; the curing agent is selected from one of methyltetrahydrophthalic anhydride and methylhexahydrophthalic anhydride.

7. The preparation method according to claim 1, characterized in that: The steps of preparing thick-walled composite tubes using the RTM process include: The epoxy resin glue is injected into the mold cavity through the injection hole at 35-45° C. and 0.05-2 MPa, and the vacuum degree in the mold cavity is maintained below -0.09 MPa; After the glue injection is completed, the glue outlet and the glue inlet are closed, and the resin is cured by the heating device of the mold or the mold is placed in an oven. The curing temperature is 90~160℃ and the curing time is 8~36h, which is carried out in multiple stages; After curing is completed, demoulding is performed, and the metal core shaft is taken out to obtain a composite material thick-walled tube.

8. The preparation method according to claim 1, characterized in that: The steps of preparing the composite thick-walled tube by SCRIMP process include: A plastic guide net is arranged on the outer layer of the fiber preform, and margins are left at both ends of the fiber preform, and the fiber preform is divided into four sections. A spiral tube is wound around the three boundaries and a three-way tube is used to inject glue, and two layers of vacuum bags are laid on the surface in sequence and sealed, and a layer of high-temperature resistant glass fiber felt is laid between the two layers of vacuum bags; When injecting glue, first inject the epoxy resin system solution into the middle glue inlet, and when the resin reaches the glue inlets at both ends, inject glue into the three glue inlets at the same time until the fiber preform is completely soaked; After the glue injection is completed, the glue outlet and the glue inlet are closed, and the resin is cured by the heating device of the mold or the mold is placed in an oven. The curing temperature is 90~160℃ and the curing time is 8~36h, which is carried out in multiple stages; After curing is completed, demoulding is performed, and the metal core shaft is taken out to obtain a composite material thick-walled tube.

9. A composite material thick-walled tube, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

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