Method for manufacturing a long-thin-ratio thin-walled composite material pipe beam and the pipe beam manufactured thereby

Abstract

The application discloses a preparation method of a large-length-ratio thin-wall composite material pipe beam and the pipe beam prepared by the method. The method comprises the following steps: step S1, preparing a foam core mold; step S2, sleeving a tubular air bag outside the foam core mold and vacuumizing; step S3, laying a prepreg sheet on the air bag; step S4, transferring the foam core mold and the air bag with the completed prepreg sheet to a mold cavity of a metal mold; step S5, filling the air bag with high-pressure gas, and then sending the air bag into an oven for heating and curing; step S6, after curing, opening the mold to obtain a product, and extracting the air bag and the foam core mold residues from the product, thereby obtaining the pipe beam product. The application overcomes the problems of the conventional metal positive mold laying-vacuum bag forming-heat press tank curing method, such as demolding difficulty, product straightness out-of-tolerance caused by mold deformation, poor surface quality and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of composite pipe beam preparation method, and particularly relates to a large-length-diameter-ratio thin-wall composite pipe beam preparation method and a prepared pipe beam. BACKGROUND

[0002] At present, the application range of advanced composite materials in the field of aircraft manufacturing is continuously expanding, from various secondary load-bearing structures such as floors and fairings to primary load-bearing structural components. Beam structural components are the main load-bearing structures of an aircraft, which are large in size, heavy in weight, and complex in stress. The use of carbon fiber composite materials to manufacture beam structural components can significantly reduce structural weight and improve stiffness, which is of great significance.

[0003] Large unmanned aerial vehicle composite beam structural components have the structural characteristics of large length-diameter ratio and thin wall thickness. Using the conventional metal male mold laying-vacuum bag forming-heat press tank curing process, there are problems such as difficulty in demolding, poor mold stiffness affecting the straightness of the product, poor quality of the outer surface, and the like, which are difficult to meet the high-precision size requirements of the aircraft pipe beam assembly, and the production cost is relatively high. SUMMARY

[0004] The present application provides a large-length-diameter-ratio thin-wall composite pipe beam preparation method and a prepared pipe beam to overcome the deficiencies and defects mentioned in the above background technology.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A large-length-diameter-ratio thin-wall composite pipe beam preparation method comprises the following steps:

[0007] Step S1, preparing a foam core mold;

[0008] Step S2, sleeving a tubular air bag around the foam core mold, the air bag being closed at one axial end and open at the other axial end, and vacuumizing through the open end of the air bag to make the air bag tightly wrap and adhere to the circumferential outer wall of the foam core mold;

[0009] Step S3, laying multiple layers of prepreg sheets on the circumferential outer wall of the air bag, each layer of prepreg being composed of multiple sheets, the butt joint between adjacent sheets in the fiber direction, the overlap joint between adjacent sheets perpendicular to the fiber direction, and the joints of the upper and lower layers of prepreg sheets being staggered in the thickness direction;

[0010] Step S4, transferring the foam core mold and air bag with the prepreg sheets laid in step S3 to the mold cavity of a metal mold, and closing the upper and lower molds of the metal mold to meet the process requirements of the gap;

[0011] Step S5, high pressure air is filled into the air bag through the open end of the air bag, the air inflation pressure is used to make the laid sheet fully adhere to the cavity of the metal mold, and then the metal mold is sent into the oven as a whole to be heated and cured to form;

[0012] Step S6, after curing, the mold is opened to obtain the product, and the air bag and the foam core mold residue are extracted from the inside of the product, thereby obtaining the tubular beam product.

[0013] Further, in step S1, the foam core mold is assembled by splicing multiple EPS foam blocks according to the required size.

[0014] Further, the size of each EPS foam block is reduced by 1-2 mm on one side compared to the inner surface size of the product obtained in step S6.

[0015] Further, the material of the tubular air bag in step S2 is nylon, latex, or polyester.

[0016] Further, the prepreg in step S3 is one or more of carbon fiber resin prepreg, glass fiber resin prepreg, and aramid fiber resin prepreg.

[0017] Further, the heating and curing process in step S5 is:

[0018] First, pressurize step by step with 0.1 MPa as a step to the target pressure 0.8-1.5 MPa, and hold pressure for 3-5 minutes at each step; after reaching the target pressure 0.8-1.5 MPa, start running the curing curve: heat at a rate of 0.5-2 ℃ / min to 60-100 ℃, hold for 0.5-1 hour, then continue to heat to 120-150 ℃, hold for 1-3 hours; finally, cool to not more than 60 ℃, and then release pressure, thereby completing the heating and curing.

[0019] Further, in step S5, the target pressure is 1.2 MPa.

[0020] A large aspect ratio thin-walled composite tubular beam is prepared by the above-mentioned large aspect ratio thin-walled composite tubular beam preparation method.

[0021] Compared with the prior art, the beneficial effects of the present application are that the shape size and surface quality of the EPS foam + air bag inner expansion forming product are guaranteed by the metal mold, and the metal mold does not need to be suspended and supported during curing, so that the product formed by the process method has good straightness, high size accuracy, smooth surface and dense internal structure, and overcomes the problems of demolding difficulty, product straightness out-of-tolerance caused by mold deformation and poor surface quality existing in the conventional metal male mold laying-vacuum bag forming-heat press tank curing method of the large-length-diameter-thin-walled composite pipe beam, and does not need to use the heat press tank equipment, thereby reducing the production cost and having obvious advantages in the forming of the large-length-diameter-thin-walled composite pipe beam. BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1 is a cross-sectional structure schematic diagram of the air bag inner expansion forming of the composite pipe beam.

[0023] Fig. 2 is a longitudinal section structure schematic diagram of the air bag inner expansion forming of the composite pipe beam.

[0024] In the figure, 1 is a foam core mold; 2 is an air bag; 3 is a sheet; 4 is a metal upper mold; 5 is a metal lower mold; 6 is a metal mold locking bolt; 7 is a gas charging connector; and 8 is a gas supply pipeline. DETAILED DESCRIPTION

[0025] The present application will be further described below in combination with the drawings and examples.

[0026] The present embodiment discloses a preparation method of a large-length-diameter-thin-walled composite circular variable cross-section pipe beam, as shown in the figure, comprising the following steps: Figs. 1-2

[0027] Step S1, splice and assemble multiple EPS foam blocks into a foam core mold 1 according to the required size, and fix the abutting position of adjacent EPS foam blocks with paper adhesive tape, and the size of each EPS foam block is 1-2 mm smaller than the single side of the inner type surface size of the finally obtained product.

[0028] Step S2, sleeve a tubular air bag 2 with a width of 140 mm (circumference of 280 mm) into the foam core mold 1, and the material of the air bag 2 is nylon, or latex, or polyester. The air bag 2 is open at one end in the axial direction and is sealed at the other end in the axial direction, the length of the air bag 2 is greater than the total length of the foam core mold 1, and 100-150 mm excess is reserved at the sealed end of the air bag 2, and 200-250 mm excess is reserved at the open end of the air bag 2.

[0029] Then, the open end of the air bag 2 is sealed with sealing tape and connected with a vacuum nozzle, the inside of the air bag 2 is vacuumized through the vacuum nozzle at the open end, so that the air bag 2 is tightly wrapped and attached to the circumferential outer wall of the foam core mold 1.

[0030] ​Step S3, laying up 9 layers of prepreg pieces 3 on the circumferential outer wall of the air bag 2, wherein the prepreg is one or more of carbon fiber resin prepreg, glass fiber resin prepreg, aramid fiber resin prepreg.

[0031] When laying up, each layer of prepreg is composed of multiple pieces, the joint gap between adjacent pieces in the fiber direction is 0-2mm, and the overlap width between adjacent pieces perpendicular to the fiber direction is 15-20mm. The joint gaps of the upper and lower layers of prepreg in the thickness direction are staggered by at least 30mm.

[0032] Step S4, transferring the foam core mold 1 and the air bag 2 with completed piece laying to the lower mold cavity of the metal lower mold 5 in the metal mold, connecting the inflation joint 7 at the open end of the air bag 2 to the clamping groove at the end of the metal lower mold 5, and then closing the metal upper mold 4 of the metal mold on the metal lower mold 5 to form a complete metal mold. The lower mold cavity of the metal lower mold 5 and the upper mold cavity of the metal upper mold 4 form a complete mold cavity, and the closing gap of the metal upper and lower molds is pressurized by connecting the bolts 6 to meet the process requirements (less than 0.1mm in this embodiment).

[0033] Step S5, connecting the external gas supply pipeline 8 to the inflation joint 7 at the end of the metal mold 5, slowly inflating high-pressure gas into the air bag 2, and using the inflation pressure to make the laid-up pieces 3 fully adhere to the mold cavity of the metal mold, and then sending the metal mold into the oven for heating and curing forming. The heating and curing forming process is as follows:

[0034] First, gradually pressurize to the target pressure of 0.8-1.5MPa at a step of 0.1MPa, and hold for 3-5 minutes at each step. After reaching the target pressure of 0.8-1.5MPa, start running the curing curve: heat at a rate of 0.5-2℃ / min to 60-100℃, hold for 0.5-1 hour, then continue to heat to 120-150℃, hold for 1-3 hours; finally, cool to not more than 60℃ and release pressure, thereby completing the heating and curing forming.

[0035] In this embodiment, the target pressure of the stepwise pressurization is 0.8-1.5MPa, which can meet the molding process requirements. However, after testing, considering the pressure-bearing capacity of the air bag and the internal quality of the product, the target pressure of 1.2MPa is the optimal value.

[0036] S6, because the EPS foam will shrink during heating, the mold is opened after curing to obtain the product, and the air bag and foam core mold residues are extracted from the inside of the product, thereby obtaining the tubular beam product.

[0037] The large-diameter-ratio thin-walled composite pipe beam product prepared in the embodiment has a circular, oval, rounded rectangular or other geometric cross section, and an equal cross section or a variable cross section. In the preparation, only a foam core 1 with a proper cross section and a metal mold with a matching cross section are selected, and the preparation can be completed.

[0038] The preferred embodiments of the present application are described in detail above with reference to the drawings, and the embodiments described in the present application are only used to describe the preferred embodiments of the present application, and do not limit the concept and scope of the present application. In the above specific embodiments, each specific technical feature described above can be combined in any appropriate manner without contradiction, and such combination should also be considered as disclosed by the present disclosure as long as it does not deviate from the concept of the present application. In order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0039] The present application is not limited to the specific details described in the above embodiments, and various modifications and improvements of the technical solutions of the present application made by those skilled in the art within the technical concept of the present application and without departing from the design concept of the present application should fall within the protection scope of the present application. The technical content claimed by the present application has been fully recorded in the claims.

Claims

1. A method for fabricating a thin-walled composite tube beam with a large aspect ratio, characterized in that, The method comprises the following steps: Step S1, preparing a foam core mold; Step S2, sleeving a tubular air bag on the foam core mold, the air bag being closed at one axial end and open at the other axial end, and vacuumizing through the open end of the air bag to make the air bag tightly wrap the circumferential outer wall of the foam core mold; Step S3, laying and pasting multiple layers of prepreg sheets on the circumferential outer wall of the air bag, each layer of prepreg being composed of multiple sheets, the butt joint between adjacent sheets in the fiber direction, and the overlap joint between adjacent sheets perpendicular to the fiber direction, and the joint seams of the upper and lower layers of prepreg being staggered in the thickness direction; Step S4, transferring the foam core mold and the air bag on which the sheets are laid and pasted in step S3 to the mold cavity of a metal mold, and closing the upper and lower molds of the metal mold to meet the process requirements; Step S5, filling high-pressure air into the air bag through the open end of the air bag, using the air inflation pressure to make the laid and pasted sheets fully adhere to the mold cavity of the metal mold, and then sending the metal mold to an oven for heating and curing; Step S6, after curing, opening the mold to obtain a product, and extracting the air bag and the foam core mold residues from the inside of the product, thereby obtaining a tubular beam product; The heating and curing process in step S5 is: first, gradually pressurize by 0.1 MPa to the target pressure 1.2 MPa, and keep pressure for 3-5 minutes at each step; after reaching the target pressure 1.2 MPa, start the curing curve: heat at a rate of 0.5-2 ℃ / min to 60-100 ℃, keep for 0.5-1 hour, then continue to heat to 120-150 ℃, keep for 1-3 hours; finally, cool to not more than 60 ℃, and then release the pressure, thereby completing the heating and curing.

2. The method for preparing a thin-walled composite tube beam with a large aspect ratio according to claim 1, characterized in that, In step S1, the foam core mold is assembled by splicing multiple EPS foam blocks according to the required size.

3. The method of claim 2, wherein the method further comprises: The size of each EPS foam block is 1-2 mm smaller than the inner surface size of the product obtained in step S6.

4. The method for preparing a thin-walled composite tube beam with a large aspect ratio according to claim 1, characterized in that, The material of the tubular air bag in step S2 is nylon, latex, or polyester.

5. The method for preparing a thin-walled composite tube beam with a large aspect ratio according to claim 1, characterized in that, The prepreg in step S3 is one or more of carbon fiber resin prepreg, glass fiber resin prepreg, and aramid fiber resin prepreg.

6. A large-aspect-ratio thin-walled composite tube beam, characterized by, The large-aspect-ratio thin-walled composite tubular beam is prepared by the method of any one of claims 1-5.

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