A low leakage rate process forming method for a glass fiber reinforced resin matrix composite sealing box

Abstract

The present invention provides a low-leakage rate process forming method for a glass fiber reinforced composite material sealed box body. Based on the box body blank, an enhanced sealing forming technology is adopted for the inner cavity of the box body, that is, vacuum bag pressing forming + sealing spraying process, to ensure reliable airtightness of the box body. The specific process flow of this method includes: Step 1: Forming the box body blank; Step 2: Trimming the box body blank; Step 3: Mixing the resin; Step 4: Soaking the glass fiber cloth with the resin; Step 5: Laying the glass fiber cloth; Step 6: Encapsulation; Step 7: Vacuum curing; Step 8: Demolding; Step 9: Trimming the edges; Step 10: Spraying the primer; Step 11: Spraying the polyurea coating; Step 12: Spraying the sealing paint; Step 13: Curing treatment; Step 14: Inspection. The present invention can effectively improve the airtight performance of the composite material box body and is applicable to the popularization and application of similar composite material packaging boxes with room temperature curing forming.

Description

Technical Field

[0001] The present invention relates to the field of composite material box process forming, and particularly to a low leakage rate process forming method for a glass fiber reinforced resin based composite material sealed box. Background Art

[0002] The VARI (Vacuum Assisted Resin Infusion) forming technology is a forming method that, under vacuum pressure, uses the flow and penetration of resin to impregnate fibers and their fabrics and cures under vacuum pressure. It is a low-cost forming technology for manufacturing large composite parts and is mostly used for manufacturing the boxes of large glass fiber composite material packaging boxes. The main structure of a glass fiber composite material packaging box is a glass fiber outer skin, an integral steel load-bearing frame, a PVC foam core layer, and a glass fiber inner skin. Through research, it is found that the permeability of the preform of the reinforcing material has an important influence on the flow characteristics of the vacuum-assisted process resin, which can effectively improve the airtight performance of the composite material packaging box. By processing resin flow channels on the PVC foam board, processing porous structures on the steel frame medium, and reasonably arranging resin flow pipes, etc., the resin flow permeability can be improved. In recent years, for the sealing performance of the assembly docking surface of the composite material packaging box, assembly structure design can be carried out, such as adjusting the assembly gap between the sealing groove and the sealing ring, the electroless plating process on the sealing surface, adding sealing structure parts, etc., to improve the airtight performance of the composite material packaging box.

[0003] A packaging box and its manufacturing method proposed in the patent document with the publication number CN 114030205A in the prior art prepares a fiber material layer on the pretreated surface; wherein, the fiber material layer includes resin and fiber reinforcing materials; a dry fiber, a skeleton, and a skin are sequentially laid on the fiber material layer to form a preform of the packaging box. The VARI forming technology is used to manufacture the composite material packaging box, making it have excellent properties of stability and not being prone to cracking.

[0004] A packaging box sealing structure proposed in the patent document with the publication number CN 211919184U in the prior art designs the assembly structure of the packaging box sealing groove and the sealing ring, including a sealing protrusion portion circumferentially arranged on the sealing surface of the box cover, a groove located on the box body and adapted to the sealing protrusion portion, and a silicone rubber sealing strip filled in the groove and used to achieve the airtight seal of the packaging box. When the box cover is closed on the box body, the bottom surface and each side surface of the sealing protrusion portion contact and extrude the silicone rubber sealing strip to form a sealing path with a zigzag path and achieve the airtight seal of the packaging box.

[0005] A packaging box sealing structure proposed in the patent document with the publication number CN 212530527U in the prior art conducts the design of the packaging box sealing assembly structure, including a support block, a base main frame, a waterproof inclined groove plate, a sealing sheath, a packaging box side wall, and a sealing ring. The base main frame is arranged on the support block, an embedding groove is recessed on the peripheral edge of the surface of the base main frame, the waterproof inclined groove plate is fixed on the base main frame, the sealing sheath is embedded and fixed in the embedding groove, the bottom of the packaging box side wall is curled inward and vertically presses the sealing sheath, a reinforcing beam is fixed on the inner side surface of the side wall, and the sealing ring is clamped between the reinforcing beam and the waterproof inclined groove plate. By using the packaging box side wall to vertically press the sealing sheath, a first layer of seal is formed. At the same time, the reinforcing beam presses the sealing ring, forming a second layer of seal. It effectively solves the problem that the assembly of the packaging box base and the box body cannot form a good seal.

[0006] A composite sealing layer and a sealing structure of a composite material packaging box proposed in the patent document with the publication number CN 114231957A in the prior art adopt a sealing form of "flange sealing surface - O-ring - flange sealing surface". Flange sealing surfaces are formed on the packaging box lid and the lower box body of the packaging box. The flange sealing surface on the packaging box lid is a planar structure, and an annular groove is formed on the flange sealing surface of the lower box body of the packaging box. The O-ring is embedded in the groove, and a clamping buckle is used to press the flange sealing surfaces of the box lid and the box body tightly. A nickel composite molybdenum disulfide sealing layer is prepared by electroless plating on the surface of the O-ring, and a diamond-like composite molybdenum disulfide sealing layer is prepared by sputtering on the surface of the carbon fiber composite material flange to achieve the sealing effect.

[0007] The above-mentioned patent CN 114030205A uses the VARI molding technology to manufacture a composite material packaging box, and does not involve a process molding method for solving the airtightness problem of the packaging box body. Patents CN 211919184U, CN 212530527U, and CN114231957A only focus on the design of the packaging box assembly structure to improve the airtight performance of the box body docking sealing surface, and do not involve ensuring the "low leakage rate" performance index requirements of the packaging box by improving the composite material box body molding process method.

[0008] The applicant has studied a large number of documents and patents for this invention, but due to space limitations, all details and contents are not listed in detail. The applicant reserves the right to add relevant prior art in the background art. Summary of the Invention

[0009] To solve the problem of air leakage in a large glass fiber reinforced resin-based composite material sealed box, the present invention provides a low leakage rate process molding method for a glass fiber reinforced resin-based composite material sealed box.

[0010] A low leakage rate process molding method for a glass fiber reinforced resin-based composite material sealed box proposed by the present invention includes the following steps:

[0011] Prepare a blank of a composite material box body;

[0012] Lay glass fiber cloth impregnated with resin in the inner cavity of the box body blank, and perform vacuum bag pressing to form;

[0013] Spray paint the inner cavity of the box body after vacuum bag pressing by using a sealing spraying process, and perform curing treatment to obtain a glass fiber reinforced resin matrix composite material sealed box body.

[0014] Further, the preparation of the blank of the composite material box body includes: preparing the blank of the box body by using VARI forming technology, and trimming the surface of the blank of the box body.

[0015] Further, the trimming of the surface of the blank of the box body includes: using a grinding machine to grind the positions with burrs at the corners of the blank of the box body; using sandpaper to grind the release agent remaining on the surface of the blank of the box body; using a vacuum cleaner or a brush to remove the sundries on the inner and outer surfaces of the blank of the box body.

[0016] Further, the laying of the glass fiber cloth impregnated with resin in the inner cavity of the box body blank includes: using a resin matrix of the same type as the blank of the box body, adding a curing agent and an accelerator for resin blending; impregnating the glass fiber cloth in the blended resin; laying the impregnated glass fiber cloth in the inner cavity of the box body blank, and scraping it flat with a rubber squeegee to make the glass fiber cloth fit the inner cavity profile without bubbles and wrinkles.

[0017] Further, the glass fiber cloth is a glass fiber multi-axial warp knitted fabric.

[0018] Further, for the inner cavity of a large rectangular horizontal box, the laying sequence of the glass fiber cloth is as follows: the operator enters the inner cavity of the box, and evenly lays the glass fiber cloth only on the lower surface of the cavity from the inside to the outside. When wrinkles cannot be opened at special-shaped or corner positions, cut a notch with scissors and then lay it flat; after the glass fiber cloth fits the inner cavity profile, let it stand for 10 - 20 minutes. After the resin cures and the viscosity of the resin increases and can meet the wall-hanging viscosity, rotate the box by 90°, and complete the laying work of the glass fiber cloth on the remaining surfaces in the same operation mode.

[0019] Further, the vacuum bag pressing forming includes: simultaneously pasting sealing rubber strips from both ends along the edge of the skirt in the inner cavity of the box. The sealing rubber strips cannot be butt-jointed but must be lapped. Then, loosely lay the release cloth on the surface of the inner cavity of the box. The release cloth can be wrinkled but not tightened, and the edge of the release cloth should extend beyond the glass fiber cloth laying layer by a certain distance. Then, evenly lay a layer of flow guiding net on the release cloth. Equally spaced vacuum tube ports are arranged around the edge of the skirt in the inner cavity of the box, and the other end of the vacuum tube is connected to a vacuum pump. Stick the vacuum bag film on the pre-arranged sealing rubber strips to form a sealed space between the vacuum bag film and the inner cavity of the box. Vacuumize the vacuum bag film and carry out pressure holding and curing. Preferably, after the vacuum degree reaches -0.10 to -0.08 MPa, carry out pressure holding and curing, and the normal temperature curing time is required to be not less than 12 h. Carry out demolding, including removing the vacuum bag film, vacuum tube, flow guiding net and release cloth. Remove the excess burrs to ensure the smoothness of the surface of the inner cavity of the box.

[0020] Further, the inner cavity of the box after vacuum bag pressing forming is painted by using a seal spraying process, including spraying primer, spraying polyurea coating and spraying sealing paint.

[0021] Preferably, for the spraying of the primer, the distance between the spray gun nozzle and the surface of the inner cavity of the box is required to be 100 - 200 mm, the spray gun pressure is 2 - 4 KPa, the gun travel is kept at a constant speed, and the method of combining horizontal gun travel and vertical gun travel is used to control the paint layer thickness and uniformity. Spray 2 - 3 coats, the thickness of each paint film is 20 - 30 μm, the spraying interval is 30 - 60 min, and the normal temperature curing time after spraying is 8 - 12 h.

[0022] Preferably, for the spraying of the polyurea coating, the curing temperature of the polyurea topcoat in the oven is 60 - 80 °C, and the curing time is 30 - 60 min; or carry out normal temperature curing, and the normal temperature curing time is 8 - 12 h.

[0023] Preferably, for the spraying of the sealing paint, it includes selecting acrylic water-based sealing paint to spray the primer and topcoat; first spray the primer, the distance between the spray gun nozzle and the surface of the inner cavity of the box is 100 - 200 mm, the spray gun pressure is 0.1 - 0.3 MPa, spray 2 - 3 coats, the thickness of each paint film is 30 - 40 μm, the spraying interval is 30 - 60 min, and the normal temperature curing time after spraying is 8 - 12 h; then spray the topcoat, first spray the parts that are more difficult to spray, and then spray the whole, spray 2 - 3 coats, the thickness of each paint film is 30 - 40 μm, and the spraying interval is 30 - 60 min.

[0024] Further, the curing treatment is normal temperature curing, and the time is not less than 24 h.

[0025] The present invention also provides a glass fiber reinforced resin matrix composite material sealed box formed according to the above method.

[0026] The present invention has the following beneficial effects compared with the prior art:

[0027] Based on the blank of the composite material sealed box body after forming, the present invention adopts the vacuum bag molding + sealed spraying process for secondary forming, solves the hidden danger of air leakage in the composite material body of the packing box, and strengthens the airtight performance of the box body. It should be noted that a layer of glass fiber woven fabric is laid in the inner cavity of the box body, and a sealed rigid body fiberglass "inner liner" is formed after curing; considering the influence of sudden environmental changes on the box body, the brittle material of the body expands and contracts due to heat, and the risk of cracks appears due to the aggravation of internal stress. Preferably, a polyurea coating and a sealing paint with high elasticity, anti-aging, good high and low temperature performance, and strong adhesion are sprayed on the inner cavity of the box body to improve the toughness of the "inner liner" and form an elastomer sealing coating. The verified effect is reliable and is applicable to the composite material forming work of similar products. Brief Description of the Drawings

[0028] Figure 1 It is a process flow chart of the low leakage rate process for forming the sealed box body in the present invention.

[0029] Figure 2 It is a schematic diagram of the vacuum bag molding in the present invention.

[0030] In the figure: 1 - vacuum pump; 2 - vacuum tank; 3 - vacuum tube; 4 - sealing strip; 5 - breather felt; 6 - vacuum bag film; 7 - flow guiding net; 8 - release cloth; 9 - glass fiber multi-axial woven fabric; 10 - inner cavity of the box body. Detailed Embodiments

[0031] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] A method for forming a low leakage rate process of a glass fiber reinforced resin-based composite material sealed box body proposed by the present invention, the step flow of which is as Figure 1 shown, and the specific steps are as follows, where steps three to nine are vacuum bag molding, and steps ten to thirteen are sealed spraying process.

[0033] Step 1: Forming the box blank. Preferably, the VARI forming technology is adopted, and the process flow includes: mold preparation (cleaning the mold, applying release wax, and coating gel coat resin); material preparation (glass fiber fabric, resin, sandwich material, etc.); preform preparation (material laying); encapsulation (applying sealing strips, laying release cloth, laying flow guiding net, arranging vacuum tubes and spiral tubes, encapsulating vacuum bag film); vacuum leakage detection; resin injection (resin preparation and guiding); curing (in an oven or at room temperature); demolding.

[0034] Step 2: Trimming the box blank. Preferably, a handheld grinder is used to grind the positions with burrs at the edges and corners of the box blank, and sandpaper is used to grind the release agent remaining on the surface of the box blank; a vacuum cleaner or brush is used to remove the excess materials on the inner and outer surfaces of the box blank; it is checked that there should be no local defects, obvious cracks, etc. on the surface of the box blank, and it is required that a smooth surface layer is formed in the inner cavity.

[0035] Step 3: Resin preparation. Preferably, a resin matrix of the same type as the box blank is adopted, and an appropriate amount of curing agent, accelerator, etc. are added, and the preparation is carried out according to the requirements of the product instruction manual.

[0036] Step 4: Impregnating the fiberglass cloth with resin. Preferably, a multi-axial warp knitted fiberglass fabric with low permeability is adopted. After cutting it to an appropriate size, it is placed in the resin matrix, taken out after being impregnated and saturated, so as to carry out the laying work in Step 5.

[0037] Step 5: Laying the fiberglass cloth. Preferably, 1 - 2 layers of impregnated and saturated multi-axial warp knitted fiberglass fabrics are laid in the inner cavity of the box blank, and a scraping rubber plate (preferably, a self-made 5mm thick rubber plate) is used to scrape it flat. It is required that the fiberglass cloth is evenly scraped with glue closely attached to the inner cavity surface, so that the fiberglass cloth fits the inner cavity surface, and there should be no bubbles or wrinkles. It should be noted that in order to prevent problems such as misalignment and dropping of the fiberglass cloth on the side walls and upper surface of the inner cavity of the box blank due to poor adhesion, there are sequence requirements for laying the fiberglass cloth in the inner cavity of a large rectangular horizontal box: the operator enters the inner cavity of the box, and the fiberglass cloth is evenly laid only on the lower surface of the cavity from the inside to the outside. When there are wrinkles that cannot be opened at the special-shaped or corner positions, a cut can be made with scissors and then laid flat. After the fiberglass cloth fits the inner cavity surface, it is left standing for 10 - 20 minutes. After the resin curing viscosity increases to meet the wall hanging viscosity, the box is rotated 90°, and the laying work of the fiberglass cloth on the remaining surfaces can be completed in the same operation mode.

[0038] Step Six: Encapsulation. Preferably, paste a sealing strip along the uniform closed-loop circumference at a position 10 - 20 mm away from the boundary of the inner cavity of the box. Do not tug on the sealing strip. The sealing strip cannot be butt-jointed and must be overlapped, with an overlap amount of 10 - 20 mm. Then, loosely lay the release cloth on the surface of the inner cavity of the box. The release cloth can be wrinkled but not taut, and the edge of the release cloth should extend about 200 mm beyond the glass fiber cloth laying layer. Uniformly lay a layer of flow guiding net on the release cloth. Arrange the vacuum tube at the position where the sealing strip is pasted in the inner cavity of the box, and fix it by bonding with the sealing strip. One end of the vacuum tube faces the inner cavity of the box and extends 30 - 40 mm based on the reference position of the sealing strip. The other end of the vacuum tube is connected to the vacuum pump outside the box. Stick the vacuum bag film on the pre-arranged sealing strip to form a sealed space between the vacuum bag film and the inner cavity of the box.

[0039] Figure 2 is a schematic diagram of vacuum bag molding. Among them, 1 is the vacuum pump, 2 is the vacuum tank, 3 is the vacuum tube, 4 is the sealing strip, 5 is the breather felt, 6 is the vacuum bag film, 7 is the flow guiding net, 8 is the release cloth, 9 is the multi-axial warp knitted glass fiber fabric, and 10 is the inner cavity of the box. Among them, the function of the breather felt 5 is to wrap the sharp corners of the edge of the vacuum tube to prevent the vacuum bag film from squeezing the tip of the vacuum tube and scratching and leaking air during the vacuum pumping process. The function of the vacuum tank 2 is to collect the resin precipitated during the vacuum pumping process to prevent the resin from flowing into the vacuum pump and causing equipment damage.

[0040] Step Seven: Vacuum pumping and curing. Preferably, conduct pre-vacuum pumping for leak detection. Open the vacuum pump valve and slowly and uniformly pump out the gas in the vacuum bag. If it is found that the release cloth at the corner, the flow guiding net, or the vacuum bag film is bridged and taut, close the vacuum pump valve and readjust. After the vacuum degree reaches -0.10 - -0.08 MPa, close the valve, keep the pressure for 10 - 15 min, and then check the sealing performance of the vacuum bag mold. After ensuring that the vacuum bag mold fits tightly, cure under pressure. It is required that the normal temperature curing time is not less than 12 h.

[0041] Step Eight: Demolding. Remove auxiliary materials such as the vacuum bag film, vacuum tube, flow guiding net, and release cloth.

[0042] Step Nine: Trimming. Preferably, use a hand-held grinding machine to grind the positions with burrs at the corners of the inner cavity of the box. It is required to remove the excess burrs and the surface should be smooth.

[0043] Step Ten: Spraying primer. In a preferred embodiment, the primer is formulated according to the requirements of the product instruction manual. Use a mechanical spraying device to spray the primer on the inner cavity of the box. The distance between the spray gun nozzle and the surface of the inner cavity of the box is required to be 100 - 200 mm, the spray gun pressure is 2 - 4 KPa, and the gun movement should be kept at a constant speed. The method of combining horizontal gun movement and vertical gun movement is adopted to control the thickness and uniformity of the paint layer. Spray 2 - 3 coats, with the thickness of each coat of paint film being 20 - 30 μm (preferably, the thickness is measured using a wet film gauge). The spraying interval is 30 - 60 min, and the curing time at room temperature after spraying is 8 - 12 h.

[0044] Step Eleven: Spraying polyurea coating. Preferably, select a polyurea coating with high elasticity, aging resistance, good high and low temperature performance, strong adhesion, and high elongation strength. The spraying method of the polyurea primer can be referred to. Among them, the curing temperature of the polyurea topcoat in the oven is 60 - 80 °C, and the curing time is 30 - 60 min; or the curing time at room temperature is 8 - 12 h.

[0045] Step Twelve: Spraying sealing paint. Preferably, select an acrylic water-based sealing paint to spray the primer and topcoat. In a preferred embodiment, first spray the primer. The distance between the spray gun nozzle and the surface of the inner cavity of the box is 100 - 200 mm, the spray gun pressure is 0.1 - 0.3 MPa, spray 2 - 3 coats, with the thickness of each coat of paint film being 30 - 40 μm, the spraying interval is 30 - 60 min, and the curing time at room temperature after spraying is 8 - 12 h. Then spray the topcoat. First spray the parts that are difficult to spray, such as the corners and sides, and then spray the whole. Do not spray the same area for a long time. The paint layer should be uniform and in place, without missing spraying or being too thin or too thick locally, and without phenomena such as running, orange peel wrinkles, etc. Spray 2 - 3 coats, with the thickness of each coat of paint film being 30 - 40 μm, and the spraying interval is 30 - 60 min.

[0046] Step Thirteen: Curing treatment. The curing time at room temperature should be not less than 24 h.

[0047] Step Fourteen: Inspection. Check the surface of the inner cavity of the box after painting. It should be smooth, free of impurities, with a uniform paint layer color, no peeling, and no cracking.

[0048] In a specific embodiment of the present invention, a low leakage rate process forming method for a large rectangular horizontal sealed box of glass fiber reinforced resin matrix composite material is provided. The method includes the following steps:

[0049] Step One: Forming the box blank. Use the VARI forming technology to complete the production of the box blank.

[0050] Step Two: Trimming the box blank. Use a handheld grinding machine to grind the burrs at the corners of the box blank, and use 80# sandpaper to grind the release agent remaining on the surface of the box blank; use a vacuum cleaner or brush to remove the excess materials on the inner and outer surfaces of the box blank.

[0051] Step 3: Resin preparation. Use 901 vinyl epoxy resin, V388 curing agent, and 1305 accelerator produced by Shanghai Sunwise New Material Technology Co., Ltd. for preparation at normal temperature of 15 - 35°C. It is recommended that the resin matrix:curing agent:accelerator = 100:(1.5 - 1.8):0.8. Among them, as the ambient temperature rises, the proportion of the curing agent should be appropriately reduced. After injection, it should be evenly stirred for 1 minute.

[0052] Step 4: Fiberglass cloth impregnation with resin. Use the biaxial fiberglass warp knitted fabric of model SW100A - 100a produced by Nanjing Fiberglass Research and Design Institute Co., Ltd. Cut it into 1 layer according to the dimensions of each surface in the inner cavity of the packaging box, impregnate it in the resin matrix, and take it out for laying work.

[0053] Step 5: Fiberglass cloth laying. According to the size of the fiberglass cloth, manually lay 1 layer at the corresponding position in the inner cavity of the rough box body, and evenly scrape it flat with a rubber squeegee with a thickness of 5 mm to remove surface air bubbles and wrinkles. The operator enters the inner cavity of the box and evenly lays the fiberglass cloth only from the inside to the outside on the lower surface of the cavity. Make slits with scissors at the special-shaped or corner positions and then lay it flat. After the fiberglass cloth adheres to the inner cavity surface, let it stand for 10 - 20 minutes. After the resin curing viscosity increases to meet the wall - hanging viscosity, rotate the box by 90°. The laying work of the fiberglass cloth on the remaining surfaces can be completed in the same operation method.

[0054] Step 6: Encapsulation. Simultaneously paste sealing strips from both ends along the edge of the skirt in the inner cavity of the box. Loosely lay 1 layer of release cloth on the surface of the inner cavity of the box, and its edge exceeds the fiberglass cloth laying layer by about 200 mm. Evenly lay 1 layer of flow - guiding net on the release cloth. Equally spaced vacuum tube ports are arranged around the edge of the skirt in the inner cavity of the box, and the other end of the vacuum tube is connected to a vacuum pump. Stick the vacuum bag film on the pre - arranged sealing strips to form a sealed space between the vacuum bag film and the inner cavity of the box.

[0055] Step 7: Vacuum pumping and curing. Conduct pre - vacuum pumping for leak detection. Open the vacuum pump valve and slowly and evenly pump out the gas in the vacuum bag. After the vacuum degree reaches - 0.10 MPa, close the valve, keep the pressure for 10 - 15 minutes, check the sealing performance of the vacuum bag mold. After ensuring that the vacuum bag mold fits tightly, cure it at normal temperature under pressure for 12 hours.

[0056] Step 8: Demolding. Remove auxiliary materials such as the vacuum bag film, vacuum tube, flow - guiding net, and release cloth.

[0057] Step 9: Trimming. Use a hand - held grinding machine to grind the positions with burrs at the corners in the inner cavity of the box to remove the burrs.

[0058] Step Ten: Spray the primer. Select a sealing primer and prepare the primer according to the instruction manual. Use a spraying device of model H20 / 35Pm and a spray gun of model W101 made by Iwata of Japan to spray the inner cavity of the box. The distance between the nozzle and the surface of the inner cavity of the box is 100 - 200 mm, and the spray gun pressure is 2 KPa. Spray 2 coats, with the thickness of each coat being 20 - 30 μm, the spraying interval being 30 min, and cure at room temperature for 8 h after spraying.

[0059] Step Eleven: Spray the polyurea coating. Select a polyaspartic ester polyurea coating and prepare it according to the instruction manual. Refer to the spraying method of the polyurea primer. It should be noted that it cures at room temperature and the curing time is 12 h.

[0060] Step Twelve: Spray the sealing paint. Select the TZ-002 odorless special sealing paint and TZ-02 curing agent produced by Beijing Red Lion Paint Industry Co., Ltd. It is recommended that the ratio of the odorless special sealing paint to the curing agent is 6:1. First, spray the primer. The distance between the spray gun nozzle and the surface of the inner cavity of the box is 100 - 200 mm, the spray gun pressure is 0.1 MPa, spray 2 coats, with the thickness of each coat being 30 - 40 μm, the spraying interval being 30 min, and cure at room temperature for 12 h after spraying. Then spray the topcoat. First, spray the parts that are difficult to spray, such as the corners and sides, and then spray the whole. Spray 2 coats, with the thickness of each coat being 30 - 40 μm, and the spraying interval being 30 min.

[0061] Step Thirteen: Curing treatment. Carry out curing treatment at room temperature, and the curing time is 24 h.

[0062] Step Fourteen: Inspection. Check the surface of the inner cavity of the box after painting. It should be smooth, free of impurities, the paint layer color should be uniform, without peeling or cracking.

[0063] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and implement it accordingly. Those of ordinary skill in the art can understand that various substitutions, changes, and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the content disclosed in the embodiments of this specification, and the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A method for forming a glass fiber reinforced resin matrix composite sealing box with a low leakage rate, characterized in that, It includes the following steps: Prepare a blank of a composite material box body; Lay glass fiber cloth impregnated with resin in the inner cavity of the box body blank and perform vacuum bag pressing; the glass fiber cloth is a glass fiber multi-axial warp knitted fabric; Use a sealed spraying process to spray paint the inner cavity of the box body after vacuum bag pressing and perform a curing treatment to obtain a glass fiber reinforced resin matrix composite material sealed box body; The vacuum bag pressing includes: Simultaneously paste sealing rubber strips from both ends along the edge of the skirt in the inner cavity of the box body. The sealing rubber strips cannot be butted and must be overlapped; then loosely lay the release cloth on the surface of the inner cavity of the box body. The release cloth can be wrinkled but not tightened, and the edge of the release cloth should exceed the glass fiber cloth laying layer by a certain distance; then evenly lay a layer of flow guiding net on the release cloth; arrange vacuum tube ports at equal intervals around the edge of the skirt in the inner cavity of the box body, and connect the other end of the vacuum tube to a vacuum pump; stick the vacuum bag film on the pre-arranged sealing rubber strips to form a sealed space between the vacuum bag film and the inner cavity of the box body; Vacuumize the vacuum bag film. After the vacuum degree reaches -0.10 to -0.08 MPa, close the valve, keep the pressure for 10 to 15 minutes, then check the airtightness of the vacuum bag mold. After ensuring that the vacuum bag mold fits tightly, keep the pressure for curing. It is required that the normal temperature curing time is not less than 12 hours; Demold, including removing the vacuum bag film, vacuum tube, flow guiding net and release cloth; Remove the excess burrs to make the surface of the inner cavity of the box body smooth; The use of the sealed spraying process to spray paint the inner cavity of the box body after vacuum bag pressing includes spraying a primer, spraying a polyurea coating and spraying a sealing paint on the inner cavity of the box body; The preparation of the composite material box body blank includes: using the VARI molding technology to prepare the box body blank and trimming the surface of the box body blank; The laying of the glass fiber cloth impregnated with resin in the inner cavity of the box body blank includes: Use the same type of resin matrix as the box body blank, add a curing agent and an accelerator for resin blending; Immerse the glass fiber cloth in the blended resin for treatment; Lay the treated glass fiber cloth in the inner cavity of the box body blank and scrape it flat with a rubber scraper to make the glass fiber cloth fit the inner cavity profile without bubbles and wrinkles; The use of the sealed spraying process to spray paint the inner cavity of the box body after vacuum bag pressing includes: Spray a primer on the inner cavity of the box body. It is required that the distance between the spray gun nozzle and the surface of the inner cavity of the box body is 100 to 200 mm, the spray gun pressure is 2 to 4 KPa, the gun travel is kept at a constant speed, and a method combining horizontal gun travel and vertical gun travel is used to control the paint layer thickness and uniformity; spray 2 to 3 coats, the thickness of each coat of paint film is 20 to 30 μm, the spraying interval is 30 to 60 minutes, and the normal temperature curing time after spraying is 8 to 12 hours; Spray a polyurea coating. The curing temperature of the polyurea topcoat in the oven is 60 to 80 °C, and the curing time is 30 to 60 minutes; or perform normal temperature curing, and the normal temperature curing time is 8 to 12 hours; Spray the sealing paint, including selecting acrylic water-based sealing paint to spray the primer and topcoat; first spray the primer, with the distance between the spray gun nozzle and the inner cavity surface of the box being 100 - 200 mm, the spray gun pressure being 0.1 - 0.3 MPa, spraying 2 - 3 coats, the thickness of each coat of paint film being 30 - 40 μm, the spraying interval being 30 - 60 min, and the normal temperature curing time after spraying being 8 - 12 h; then spray the topcoat, first spray the parts that are difficult to spray, and then spray the whole, spraying 2 - 3 coats, the thickness of each coat of paint film being 30 - 40 μm, and the spraying interval being 30 - 60 min.

2. The method according to claim 1, characterized in that, The surface finishing of the box blank includes: using a handheld grinding machine to grind the positions with burrs at the corners of the box blank; using sandpaper to grind the release agent remaining on the surface of the box blank; using a vacuum cleaner or brush to remove the debris on the inner and outer surfaces of the box blank.

3. The method according to claim 1, wherein For the inner cavity of a large rectangular horizontal box, the laying sequence of the fiberglass cloth is as follows: The operator enters the inner cavity of the box and evenly lays the fiberglass cloth from the inside to the outside only on the lower surface of the cavity. When wrinkles cannot be opened at special-shaped or corner positions, cut a notch with scissors and then lay it flat; After the fiberglass cloth adheres to the inner cavity profile, let it stand for 10 - 20 min. After the resin cures and the viscosity increases to meet the wall-hanging viscosity, rotate the box by 90° and complete the laying of the fiberglass cloth on the remaining surfaces in the same operation mode.

4. The method according to claim 1, wherein The curing treatment is normal temperature curing for no less than 24 h.

5. A glass fiber reinforced resin matrix composite sealing box formed by the method according to any one of claims 1 - 4.

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