Forming method of high-pressure dipping forming composite material rod piece

Abstract

The invention discloses a manufacturing method of a high-pressure dipping forming composite material rod piece. The manufacturing method comprises the following steps: programming a numerical control winding machine; a composite material rod piece framework is wound; the low-density winding rod piece is pre-cured to form a high-porosity composite material rod piece framework of a porous structure; coating a glue storage layer outside the pre-cured framework, making a bag, and vacuumizing to form a negative pressure cavity; heating and pressurizing to extrude the high-density glue solution into a high-density cavity of a rod piece framework, synchronously removing gas in pores of the framework in a vacuum environment, and curing to form a product; and nondestructive inspection. According to the method, the preformed framework is formed under the normal pressure through winding of the low-density glue solution, the product is preformed at the low temperature, the boundary dimension is basically fixed in the subsequent glue injection or glue pressing curing process, compared with a conventional wet winding product, the problems of fiber wrinkles and poor flaw detection caused by large fiber compression amount are reduced, and the product quality is improved. And meanwhile, the problems of large surface finishing amount and even single-side wall deviation of wet winding round rod products are reduced.

Description

Technical Field

[0001] The invention relates to a molding method of a high-pressure impregnation molding composite material rod, belonging to the technical field of processing and molding of composite material structural parts. Background Art

[0002] With the continuous development of the aerospace industry, the demand for lightweight spacecraft is increasing. Composite materials, with their excellent designability, high specific strength and specific modulus, are gradually replacing metal materials in various spacecraft, which not only reduces launch costs, but also streamlines the use of payload space.

[0003] At present, the main load-bearing structural components of the payload series in satellite spacecraft are mainly formed by wet winding or tube rolling. The composite rods formed by this method have a large compression volume and the glue content is difficult to control accurately. During the curing and pressing, the products are prone to fiber material slippage and extrusion wrinkles, resulting in poor fiber continuity of the main load-bearing rods and unilateral wall thickness. These problems, in turn, lead to many machining damages on the rod surface, loss of fiber continuity, and a decrease in effective mechanical bearing capacity.

[0004] Patent document CN104260367A discloses a method for forming a lightweight composite material structural connector, which involves stacking multiple layers of carbon fiber plain fabric in an RTM mold, sewing the multiple layers of carbon fiber plain fabric, and injecting resin into the mold for curing to form a product. This method is a conventional RTM molding method, and the molded product has the advantages of light weight, high strength, and good thermal stability, and has a significant weight reduction effect compared to aluminum alloys of the same specification. However, the surface of the product of the molding method mentioned in this scheme is highly dependent on the RTM molding mold, and the outer contour must be defined by the mold. Moreover, for products with thicker wall thickness, the porosity of ordinary RTM molded products is relatively high, and there are many internal defects.

[0005] Patent 201210187197.5 discloses a method for impregnation molding of composite structural parts, which is composed of a skeleton part and a woven fiber together to form a preform with the same shape as the composite part to be processed and is impregnated. This method will not produce interlayer deformation and dislocation defects, and increases the interlayer strength as well as the compressive and bending strength of the composite material. However, its interlayer porosity is difficult to control, and the woven preform is very prone to impregnation and unevenness, and has many internal defects. Summary of the invention

[0006] The purpose of the present invention is to provide a method for forming a composite material rod by high-pressure impregnation molding in view of the shortcomings of the prior art.

[0007] In order to achieve the above object, the present invention provides a method for forming a composite rod by high pressure infusion molding, comprising the following steps: Step S1, CNC programming: CNC programming is performed according to the structure and size of the required composite rod; Step S2, winding the shaped skeleton: placing the core mold on a CNC winding machine, impregnating the carbon fiber with a low-density resin glue solution and winding the composite material rod skeleton according to the winding procedure; Step S3, pre-curing the skeleton: pre-curing the rod skeleton formed in step S2 to form a composite rod skeleton with a porous structure; Step S4, bag making: coating the outer surface of the frame with a rubber storage layer to make a vacuum bag; Step S5, pressing and curing: heating and evacuating the composite material rod skeleton, and pressing (ie, high pressure impregnation) and curing and shaping the composite material rod product.

[0008] Preferably, in step S1, the CNC programming is performed according to the geodesic winding line type based on the rod structure. This programming method not only takes into account the geometric shape and size specifications of the rod, but also covers the requirements of surface roughness, tolerance grade, etc., to ensure that the processed product can accurately meet the design standards.

[0009] Preferably, in step S2, the carbon fiber is selected from high-strength carbon fiber with a longitudinal tensile strength of ≥2000 MPa and a longitudinal tensile modulus of ≥130 MPa; the resin glue is selected from a density of 0.9±0.015 g / cm 3 The epoxy resin used for wet winding is about 10000 square meters. The resin glue at this density contains a large amount of volatile solvents, which causes a high porosity of 15% to 25% to be formed between the skeleton layers during the heating process.

[0010] Preferably, in step S3, the pre-curing conditions are: heating rate 1-2°C / min, heating to 120-140°C and keeping warm for 2-4h.

[0011] Preferably, the glue storage layer in step S4 is a high-density epoxy resin layer or epoxy hot melt adhesive film with a glue content of more than 70wt%, and the density of the glue used in the glue storage layer is 1.1±0.1g / cm 3 .

[0012] Preferably, in step S5, the pressing and curing molding specifically includes: First, keep it at 110℃ -115℃ for 0.5-1h, maintain the vacuum gauge pressure ≤-0.095MPa, and pressurize it at 0.2~0.5MPa; then keep it at 170℃ -180℃ for 3-3.5h, maintain the pressure at 0.2~0.5MPa, and then cool it to room temperature and take it out of the furnace; this vacuum pressing method can not only make the glue penetrate the high-porosity skeleton under high pressure, but also make the air trapped between layers be discharged with the vacuum environment to ensure the quality of the layers.

[0013] Preferably, the heating and cooling rates during the press-curing process are set to 0.3-0.5°C / min.

[0014] Preferably, the step S5 further includes a non-destructive testing step: removing auxiliary materials on the outer surface of the rod product, taking out the rod and performing ultrasonic non-destructive testing.

[0015] In the present invention, ultrasonic testing equipment is used to perform ultrasonic A scanning, and the non-destructive flaw detection standard meets the A-level requirements in GJB2895-97.

[0016] The invention also provides a composite material rod obtained by the above-mentioned molding method.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses low-density resin glue to impregnate fibers for winding and pre-curing to form a three-dimensional high-porosity skeleton, which is convenient for shaping composite rods and forming injection channels, and has strong overall designability. The present invention uses a method of forming a preformed skeleton by winding low-density glue under normal pressure, and pre-shapes the product at a relatively low temperature, and the external dimensions are basically fixed during the subsequent injection or glue pressing curing process.

[0018] 2. The composite rod skeleton with porous structure has no compression and wrinkles. During the subsequent pressure injection process, the resin penetrates along the fiber direction and the pore direction at the same time. At the same time, because the skeleton has been finalized, no additional machining and trimming are required, and there will be no fiber continuity damage and unilateral wall thickness problems caused by processing; and compared with conventional wet winding products, the fiber wrinkles and poor flaw detection caused by large fiber compression are reduced.

[0019] 3. Compared with wet winding molding, high-density glue liquid or hot melt glue film high-pressure impregnation reduces the air-drying time of volatile components such as acetone, shortens the molding cycle by half, and greatly improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the interior of a three-dimensional porous mesh skeleton. DETAILED DESCRIPTION

[0021] In order to make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0022] This embodiment provides a method for forming a composite rod by high-pressure infusion molding, comprising the following steps: Step S1, CNC programming: CNC programming is performed according to the required structure and size of the composite rod; in this embodiment, the CNC winding machine is a Hunan Jiangnan four-sided CNC winding machine, the equipment model is: SLW02.11-350-4 / 1-10000-CNC, and the size of the composite rod is Φ40×2-2000.

[0023] Step S2, skeleton winding: placing the core mold on a CNC winding machine, and winding the composite rod skeleton with carbon fiber impregnated with low-density resin glue according to the winding procedure. In this embodiment, the winding sequence used is ±45 / 02 / 90 / ±45 / 02 / 90 / 90 / 02 / ±45 / 90 / 02 / ±45. The three-dimensional skeleton after winding is as follows: Figure 1 As shown in the figure, the winding layer fibers at different angles such as ±45°, 0° and 90° form a three-dimensional porous gap structure that is cross-sectional and vertical, which is convenient for subsequent pre-curing and shaping. The carbon fiber used is high-strength carbon fiber T700SC-12K, and the resin glue used is AG-80 epoxy resin for wet winding. The density of the resin glue is 0.9±0.015g / cm 3 The resin glue at this density contains a large amount of volatile solvents, which causes high porosity to form between the skeleton layers during the heating process.

[0024] Step S3, pre-curing the skeleton: pre-curing the rods formed in step S2 to form a composite rod skeleton with a porous structure having a high porosity; in a preferred embodiment, the pre-curing conditions are: room temperature to 130°C, 1°C / min, and 130°C for 3 hours. In step S3, the porosity of the porous structure skeleton formed after pre-curing is 20%±5% through the low-density precise control of the AG-80 resin glue in step S2.

[0025] Step S4, bag making: coating the outer surface of the skeleton with a glue storage layer to make a vacuum bag; in a preferred case, the glue storage layer is generally selected from a high-density epoxy resin rich glue layer or glue film (such as a high-density AG-80 epoxy resin layer or AG-80 epoxy hot melt adhesive film) with a glue content of more than 70wt%, and the glue density is preferably 1.1±0.1g / cm 3 .

[0026] Step S5, pressing and curing: heating and vacuuming the composite rod skeleton in a state of being covered with the rubber storage layer, and pressing and curing the composite rod skeleton to form a rod product; in this embodiment, the product curing conditions are: First, keep the temperature at 110℃ -115℃ for 0.5-1h, keep the vacuum gauge pressure ≤-0.095MPa, and pressurize at 0.2~0.5MPa; then keep the temperature at 170℃ -180℃ for 3-3.5h, keep the pressure at 0.2~0.5MPa, and then cool it down to room temperature. The rate of heating and cooling in the whole process is 0.3-0.5℃ / min. This vacuuming and pressing method can not only make the glue penetrate the high-porosity skeleton under high pressure, but also make the air mixed between the layers be discharged with the vacuum environment to ensure the quality of the layers.

[0027] Step S6, non-destructive testing: remove the outer surface auxiliary materials, take out the rod and perform ultrasonic non-destructive testing. In a preferred case, the ultrasonic method used is ultrasonic A scanning, and the non-destructive testing standard meets the A-level requirements in GJB2895-97.

[0028] The advantages of the high-pressure impregnation molding composite rod molding method selected in the present invention compared with conventional wet winding and conventional impregnation molding composite rod molding are as follows: Forming method Dimension control / mm Molding time / d Flaw detection qualified rate / % Wall thickness uniformity Wet Forming ±0.3 7 95 One-sided High pressure impregnation molding (pressure 0.5MPa) ±0.15 3 99 Uniform wall thickness Dip molding (no pressing) ±0.15 3 75 Uniform wall thickness The above description is only a preferred embodiment of the present invention and is not any formal or substantial limitation of the present invention. It should be pointed out that a person skilled in the art can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A method for forming a composite rod by high pressure infusion molding, characterized in that: The steps include: Step S1, CNC programming: CNC programming is performed according to the structure and size of the required composite material rod; Step S2, winding of the shaped skeleton: placing the core mold on a CNC winding machine, impregnating the carbon fiber with a low-density resin glue, and winding the composite material rod skeleton according to the winding procedure; Step S3, pre-curing the skeleton: pre-curing the rod skeleton formed in step S2 to form a composite rod skeleton with a porous structure; Step S4, bag making: coating the outer surface of the frame with a rubber storage layer to make a vacuum bag; Step S5, pressing and curing: heating and vacuumizing the composite material rod skeleton, and pressing and curing the composite material rod skeleton to form a rod product.

2. The method for forming a high pressure infusion composite rod according to claim 1, characterized in that: In the step S1, the numerical control programming is performed according to the rod structure and the geodesic winding line type.

3. The method for forming a high pressure infusion composite rod according to claim 1, characterized in that: In step S2, the carbon fiber is selected from high-strength carbon fiber with a longitudinal tensile strength of ≥2000 MPa and a longitudinal tensile modulus of ≥130 MPa; the resin glue is selected from epoxy resin for wet winding, and the density of the glue is 0.9±0.015 g / cm 3 .

4. The method for forming a high pressure infusion composite rod according to claim 3, characterized in that: In the step S3, the pre-curing conditions are: heating rate 1-2°C / min, heating to 120-140°C and keeping warm for 2-4h.

5. The method for forming a high pressure infusion composite rod according to claim 1, characterized in that: The glue storage layer in step S4 is a high-density epoxy resin layer or epoxy hot melt adhesive film with a glue content of more than 70%, and the density of the glue used in the glue storage layer is 1.1±0.1g / cm 3 .

6. The method for forming a high pressure infusion composite rod according to claim 1, characterized in that: In the step S5, the pressing and curing molding specifically includes: First, keep it at 110℃ -115℃ for 0.5-1h, keep the vacuum gauge pressure ≤-0.095MPa, and pressurize it at 0.2~0.5MPa; then keep it at 170℃ -180℃ for 3-3.5h, maintain the pressure at 0.2~0.5MPa, and then let the furnace cool to room temperature and take it out of the furnace.

7. The method for forming a high pressure infusion composite rod according to claim 6, characterized in that: The heating and cooling rates during the press curing process are set to 0.3-0.5°C / min.

8. The method for forming a high pressure infusion composite rod according to claim 1, characterized in that: The step S5 also includes a non-destructive testing step: removing the auxiliary materials on the outer surface of the rod product, taking out the rod and performing ultrasonic non-destructive testing.

9. A composite rod obtained by the molding method according to any one of claims 1 to 8.

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