Large lightweight composite material packaging box and forming method thereof

Abstract

The present invention relates to the field of packaging box forming methods, specifically a large-scale lightweight composite material packaging box and its forming method. It solves the technical problems that the existing RTM process cannot process large variable cross-section structures with reinforced ribs, and there is a contradiction between lightweight and performance. The main innovations of the present invention are as follows: 1) The product is designed as a frame-skin structure, and the process adopts a combination of hand lay-up and RTM. The frame part and surface reinforcement adopt the hand lay-up process, and the skin part adopts the RTM forming process. The proportion of laying fiber layers by the two processes is allocated to solve the problem that large variable cross-section structures are difficult to form; 2) The design adopts the addition of lightweight PET material filling material, and the filling position and filling amount are designed to reduce the weight while ensuring that all performance standards of the packaging box are met.

Description

Technical Field

[0001] The invention relates to the field of packaging box forming methods, in particular to a large lightweight composite material packaging box and a forming method thereof. Background Art

[0002] Composite packaging boxes are made from a composite of reinforced fibers and resins. They offer advantages such as light weight, high specific strength, fatigue resistance, and excellent thermal insulation. They are primarily used for product packaging, transportation, and storage. Specialty products require packaging boxes with appropriate drop resistance, high and low temperature resistance, and sealing properties. Four main methods exist for manufacturing composite packaging boxes: 1. Hand lay-up (wet process); 2. Compression molding (SMC); 3. Vacuum infusion (dry process); and 4. RTM molding. Hand lay-up is simple to operate, but product quality is inconsistent and cannot meet the mass production requirements of high-performance packaging boxes. Compression molding offers high surface quality and stable performance, but due to the discontinuous fibers, its performance cannot meet the requirements for packaging boxes with strict sealing and strength requirements. Furthermore, the initial mold and equipment costs are high, making it difficult to reduce costs later if production volumes are insufficient. Vacuum infusion, a more advanced molding process commonly used for high-performance products, only guarantees single-sided quality and cannot meet the overall appearance requirements of the packaging box. Furthermore, the process consumables are expensive, making mass production costs difficult to control. The RTM process can meet the performance and appearance requirements of packaging boxes, but it is difficult to implement if the product has a large variable cross-section (greater than 9mm). There are few cases in which it can be used in large packaging box molding applications. Summary of the Invention

[0003] The present invention aims to solve the following technical problems: (1) the existing RTM process cannot process structures with large variable cross-sections of reinforcement ribs; (2) large packaging boxes need to meet lightweight requirements as well as high performance indicators such as strength, sealing, and stacking, and there is a contradiction between lightweight and performance.

[0004] The large lightweight composite material packaging box described in the present invention is realized by adopting the following technical solution: a large lightweight composite material packaging box, including a box body and a box cover, and the box cover and the box body skin are respectively provided with a plurality of upper and lower corresponding ring rib sections, and the upper and lower ring rib sections form a complete plurality of ring ribs after the box cover and the box body are buckled together; at the same time, the box cover and the middle part of the box body are provided with axial ribs along the axial direction; the ring ribs and axial ribs are both variable cross-section structures with a thickness greater than the skin on both sides thereof; the inside of the ring ribs and the axial ribs are filled with foam preforms; metal embedded parts are fixed inside the ring ribs, and metal embedded parts are also fixed in the skin at both ends of the box body and the box cover; the metal embedded parts are arranged close to the junction of the box body and the box cover.

[0005] The packaging box of the present invention fills the annular ribs and the axial ribs with foam prefabricated parts, thereby meeting the strength requirements of the large variable cross-section structure while reducing the weight of the packaging box; at the same time, the strength of the packaging box is effectively improved by the metal embedded parts provided in the skin.

[0006] The method for forming a large lightweight composite material packaging box of the present invention is achieved by adopting the following technical solution: a method for forming a large lightweight composite material packaging box, wherein the mold used includes a box body female mold, a box body male mold, a box cover female mold, and a box cover male mold; and the method comprises the following steps:

[0007] 1. Hand lay-up part:

[0008] S1. Spray a 0.4±0.02mm thick layer of epoxy vinyl gel coat on each of the working surfaces of the box body mold, box body mold, box cover mold, and box cover mold.

[0009] S2. After S1 is cured, hand-lay a layer of 30g / ㎡ surface felt and a layer of 150g / ㎡ chopped fiber felt on the working surfaces of the box body mold, box body mold, box cover mold, and box cover mold.

[0010] S3. After S2 is cured, a lightweight base layer of fiber is prepared on the mold's annular and axial reinforcements. 600g / m2 multi-axial basalt fiber cloth is laid using a wet process. The layers, from inside to outside, are: 600g / m2 multi-axial basalt fiber cloth --- 150g / m2 basalt chopped fiber mat --- 600g / m2 multi-axial basalt fiber cloth --- 150g / m2 basalt chopped fiber mat --- 600g / m2 multi-axial basalt fiber cloth. The layers are laid in a concave shape to ensure firm adhesion of the fibers.

[0011] Place the 150g / m³ PET foam preform processed by CNC (computer numerical control) machine into the rib groove with a filling thickness of 15±2mm. Fill the gap between the rib groove and the rib groove with basalt fiber yarn.

[0012] S4. Use structural adhesive to secure the metal embedded part to the designated position within the rib groove. Use hand lay-up to level this position along the rib groove surface.

[0013] 2. RTM process

[0014] S5. Lay one layer of 350g / ㎡ basalt fiber cloth and one layer of 450g / ㎡ basalt fiber cloth on the positive mold surface of the box after S4.

[0015] S6. Lay a layer of lightning protection copper mesh on the box cavity mold after S4, with the upper edge of the mesh 25 mm from the mold parting line. Secure it with spray adhesive during laying. After laying, dry-lay a layer of 350 g / m2 basalt fiber cloth and a layer of 450 g / m2 basalt fiber cloth on the copper mesh surface.

[0016] S7. Close the molds of S5 and S6. Before injecting glue, check the sealing performance of the molds. Vacuum to 0.06 kPa and maintain the pressure for 20 minutes.

[0017] After vacuum verification, RTM molding is carried out, and the process parameters are as follows:

[0018] 1). Injection pressure: 2 bar, injection rate: 80g / time, 25-30 times per minute; injection volume: 30kg;

[0019] 2) Resin formula: Calculated by mass ratio, MFE-27L pre-cured epoxy resin 100%, M50 curing agent 0.75-2.25;

[0020] 3) Gel time: Before injection, a casting test should be conducted within the curing agent ratio range to determine the curing agent gel time;

[0021] 4). After gelling, heat curing is carried out. The curing temperature curve is: room temperature (8h)--45℃ (1h)--55℃ (1h)--60℃ (2h)--room temperature;

[0022] 5). After solidification and cooling, demoulding, the box is completed;

[0023] S8. The laying process of the box cover is the same as that of the box body. The RTM process parameters are:

[0024] 1). Injection pressure: 2 bar, injection rate: 80g / time, 25-30 times per minute; injection volume: 20kg;

[0025] 2) Resin formula: by mass ratio, MFE-27L pre-accelerated epoxy resin 100%, M50 curing agent 1-1.5;

[0026] 3) Gel time: Before injection, a casting test should be conducted within the curing agent range to determine the curing agent specific gel time;

[0027] 4). After gelling, heat curing is carried out. The curing temperature curve is: room temperature (8h)--45℃ (1h)--55℃ (1h)--60℃ (2h)--room temperature;

[0028] 5). After solidification and cooling, demoulding, the box cover is completed;

[0029] S9. Assemble various accessories as required and the basalt box product is completed.

[0030] The main solutions to the aforementioned technical problems in this preparation method are as follows:

[0031] 1) The product is designed as a frame-skin structure, using a combination of hand lay-up and RTM processes. The frame and surface reinforcement are hand-laid, while the skin is molded using RTM. The fiber layer layup ratios of the two processes are adjusted to address the difficulty in molding large variable cross-section structures.

[0032] 2) The design uses lightweight PET filling material. The filling location and filling amount are designed to reduce the weight while ensuring that the performance of the packaging box meets the standards.

[0033] The sandwich structure of reinforced fiber composite material (3-5mm thick) - PET material (about 18mm thick) - reinforced fiber composite material (7-9mm thick) is formed by laying it on the filling parts such as the hoop reinforcement and axial reinforcement. While all performances are guaranteed, the rigidity is effectively improved and the weight is reduced.

[0034] The packaging box formed by the process method of the present invention can meet the following performance requirements:

[0035] Sealing performance: 5.2KPa×30min, 25℃, no pressure drop;

[0036] 40 KPa×30min, 25℃, no pressure drop;

[0037] Strength performance: stacking 1150kg for 1h, -40℃, no deformation;

[0038] Stacking 1150kg for 1h, 70℃, no deformation;

[0039] Drop performance: 10.5m vertical without wind box, the items inside will not be damaged;

[0040] The weight of the box cover shall not exceed 45kg (including metal embedded parts and lightning protection copper mesh, etc.);

[0041] The box weight does not exceed 70kg (including metal embedded parts and lightning protection copper mesh, etc.);

[0042] Lightning protection, fire resistance, flame retardancy, dynamic load, static load, train transportation, road transportation, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the structure of a top-down opening composite material packaging box according to an embodiment of the present invention.

[0044] Figure 2This is a schematic diagram of the longitudinal variable cross-section of the packaging box cover according to an embodiment of the present invention.

[0045] Figure 3 This is a partially enlarged schematic diagram of the longitudinal variable cross-section of the packaging box cover of an embodiment of the patent of the present invention.

[0046] Figure 4 This is a schematic cross-sectional view of the lightweight material filling position of the packaging box lid according to an embodiment of the present invention.

[0047] Figure 5 Composite material packaging box with large variable cross-section filling structure (including embedded parts).

[0048] Figure 6 for Figure 5 NN cross-sectional view in.

[0049] 1-Box cover, 2-Box body, 3-Skin, 4-Circular reinforcement, 5-Axial reinforcement, 6-Metal embedded parts, 7-Foam prefabricated parts, 8-Bolts. DETAILED DESCRIPTION Example 1

[0050] like Figure 1-6 As shown, a large lightweight composite packaging box includes a box cover 1 and a box body 2, and the box cover 1 and the box body 2 are respectively provided with a plurality of upper and lower corresponding ring rib sections on the skin 3. When the box cover 1 and the box body 2 are buckled together, the upper and lower ring rib sections form a complete plurality of ring ribs 4; at the same time, the box cover 1 and the box body 2 are both provided with axial ribs 5 in the middle along the axial direction; the ring ribs 4 and the axial ribs 5 are both variable-section structures with a thickness greater than the skins on both sides thereof; the inside of the ring ribs 4 and the axial ribs 5 are filled with foam preforms 7; metal embedded parts 6 are fixed inside the ring ribs 4, and metal embedded parts 6 are also fixed in the skins 3 at both ends of the box cover 1 and the box body 2; the metal embedded parts 6 are all arranged near the junction of the box cover 1 and the box body 2; the thickness of the skin 3 constituting the box body and the box cover is 3~5mm, and the thickness of the ring ribs 4 and the axial ribs 5 is 23±2mm; the preferred skin thickness is 3mm, and the thickness of the ring ribs and the axial ribs is 23mm. Example 2

[0051] Two metal embedded parts 6 are embedded in each ring rib section on the box body, and two metal embedded parts 6 are embedded in each end skin of the box body; two metal embedded parts 6 are embedded in each ring rib section on the box cover, and two metal embedded parts 6 are embedded in each end skin of the box cover. Each metal embedded part 6 is fixed by a pair of bolts 8. Example 3

[0052] like Figure 1 As shown, there are six ring bars in total;

[0053] The box body and the cover are connected by a sealed buckle; the cover and the box body are also embedded with a lightning protection copper mesh; the lightning protection copper mesh laid on the box body is connected by 16 buckles (assembled after molding) around the circumference, and then connected to the metal grounding device installed on the box body.

[0054] The packaging box of the present invention is prepared by the following method.

[0055] 1) Main raw materials: MET-27L pre-catalyzed flame-retardant epoxy vinyl resin, M50 curing agent, epoxy vinyl gel coat, 600g / m2 multi-axial (0° / 90° / ±45°) basalt fiber cloth, 450g / m2 axial (0° / 90°) basalt fiber cloth, 350g / m2 axial (0° / 90°) basalt fiber cloth, 30g / m2 basalt fiber chopped strand mat, 150g / m2 basalt fiber chopped strand mat, structural adhesive.

[0056] 2) Mold: Use 45# steel metal mold, consisting of a box body female mold, box body male mold, box cover female mold, and box cover male mold. After the mold is closed, the skin cavity thickness is 3.0mm, and the annular reinforcement cavity thickness is 23mm.

[0057] 3) Process implementation:

[0058] 1. Hand lay-up part:

[0059] S1. Spray a layer of epoxy vinyl gel coat (approximately 0.4 mm thick) on the working surfaces of the box body female mold, box body male mold, box cover female mold, and box cover male mold.

[0060] S2. After S1 is cured, a layer of 30g / ㎡ surface (inner layer) felt and a layer of 150g / ㎡ chopped fiber felt (outer layer) are hand-laid on the working surfaces of the four molds: the box body mold, the box body mold, the box cover mold, and the box cover mold.

[0061] S3. After S2 is cured, a lightweight base fiber layer is applied to the mold's annular and axial reinforcements. Specifically, a 600g / m2 multi-axial basalt fiber cloth is laid using a wet process. The layers, from inside to outside, are: 600g / m2 multi-axial basalt fiber cloth --- 150g / m2 basalt chopped fiber mat --- 600g / m2 multi-axial basalt fiber cloth --- 150g / m2 basalt chopped fiber mat --- 600g / m2 multi-axial basalt fiber cloth. The layers are laid in a concave shape, ensuring a tight fit.

[0062] Through calculation, the 150g / m³ PET foam preform ( Figure 4 The filling thickness is 15mm, and the gap between the ribs and the groove is filled with basalt fiber.

[0063] S4. Use structural adhesive to fix the metal embedded parts at the designated position in the rib groove, and use hand lay-up to level this position along the rib groove surface.

[0064] 2. RTM process

[0065] S5. On the positive mold working surface of the box after completing S4, lay one layer of 350g / ㎡ basalt fiber cloth and one layer of 450g / ㎡ basalt fiber cloth.

[0066] S6. Lay a layer of lightning protection copper mesh on the negative mold after completing S4. Place the upper edge of the mesh 25 mm from the mold parting line and secure it with spray adhesive. After laying, dry-lay a layer of 350 g / m2 basalt fiber cloth and a layer of 450 g / m2 basalt fiber cloth on the copper mesh.

[0067] S7. Close the molds of laid S5 and S6. Before injecting glue, check the sealing performance after closing the molds. Vacuum to 0.06KPa and maintain the pressure for 20 minutes.

[0068] After vacuum verification, RTM molding is carried out, process parameters

[0069] 1). Injection pressure: 2 bar, injection rate: 80g / time, 25-30 times per minute; injection volume: 30kg;

[0070] 2) Resin formula: by mass ratio, MFE-27L pre-accelerated epoxy vinyl resin 100%, M50 curing agent 0.75-2.25;

[0071] 3). Gel time: Before injecting glue, a casting test should be carried out within the curing agent ratio range to determine the curing agent ratio gel time: about 70 minutes in summer and about 45 minutes in winter.

[0072] 4). After gelation, heat curing is carried out. The curing temperature curve is: RT (8h)--45℃ (1h)--55℃ (1h)--60℃ (2h)--RT (RT refers to room temperature, usually 25℃).

[0073] 5). After solidification and cooling, demoulding is carried out and the box is completed.

[0074] S8. The laying process of the box cover is the same as that of the box body. The RTM process parameters are:

[0075] 1). Injection pressure: 2 bar, injection rate: 80g / time, 25-30 times per minute; injection volume: 20kg;

[0076] 2) Resin formula: MFE-27L pre-accelerated epoxy vinyl resin 100%, M50 curing agent 1-1.5;

[0077] 3). Gel time: Before injecting glue, a casting test should be carried out within the curing agent range to determine the curing agent gel time: about 70 minutes in summer and about 45 minutes in winter.

[0078] 4). After gelation, heat curing is carried out. The curing temperature curve is: RT (8h)--45℃ (1h)--55℃ (1h)--60℃ (2h)--RT.

[0079] 5). After solidification and cooling, demoulding, the box cover is completed.

[0080] S9. Assemble various accessories as required and the basalt box product is completed.

[0081] The main innovations of the present invention are:

[0082] 1) Hand lay-up-RTM molding process. Combining hand lay-up and RTM processes leverages the advantages of each process while overcoming its shortcomings. Hand lay-up offers high operability, allowing for proportional filling of large variable cross-sections to meet RTM process requirements and achieve the desired performance for composite packaging boxes.

[0083] 2) Lightweighting: In this molding process, the placement of the lightweight PET material, the volume ratio of fiber to lightweight material, and the layering process effectively control the fiber and resin content.

[0084] 3) For boxes with a large slenderness ratio (length-to-width ratio greater than 5 times, length-to-depth ratio greater than 5 times, width-to-depth ratio less than 1.2 times, and length not less than 3 meters), see S8 for the RTM molding parameters for variable cross-section structures. These molding parameters meet the RTM molding requirements for top-and-bottom openings with large length-to-depth and width ratios. The finished products meet the 40 kPa airtightness requirements, as well as strength and stacking requirements.

[0085] Packaging box product performance test data and comparison with traditional hand lay-up process performance: .

Claims

1. A method for forming a large lightweight composite material packaging box, wherein the molds used include a box body female mold, a box body male mold, a box cover female mold, and a box cover male mold; characterized in that: The steps include:

1. Hand lay-up part: S1. Spray a 0.4 ± 0.02 mm thick layer of epoxy vinyl gel coat on each of the working surfaces of the box body female mold, box body male mold, box lid female mold, and box lid male mold. S2. After S1 is cured, hand-lay a layer of 30g / ㎡ surface felt and a layer of 150g / ㎡ chopped fiber felt on the working surfaces of the box body mold, box body mold, box cover mold, and box cover mold. S3. After S2 is cured, a lightweight base layer of fiber is applied to the mold's annular and axial reinforcements. 600g / m2 multi-axial basalt fiber cloth is laid using a wet process. The layers, from inside to outside, are: 600g / m2 multi-axial basalt fiber cloth --- 150g / m2 basalt chopped fiber mat --- 600g / m2 multi-axial basalt fiber cloth --- 150g / m2 basalt chopped fiber mat --- 600g / m2 multi-axial basalt fiber cloth. The layers are laid in a concave shape, ensuring firm adhesion of the fibers. Place the 150g / m³ PET foam preform processed by CNC into the rib groove with a filling thickness of 15±2mm, and fill the gap between the rib groove and the rib groove with basalt fiber yarn; S4. Use structural adhesive to secure the metal embedded part to the designated position within the rib groove. Use hand lay-up to level this position along the rib groove surface.

2. RTM process S5. Lay one layer of 350g / ㎡ basalt fiber cloth and one layer of 450g / ㎡ basalt fiber cloth on the positive mold surface of the box after S4. S6. Lay a layer of lightning protection copper mesh on the box cavity mold after S4, with the upper edge of the mesh 25 mm from the mold parting line. Secure it with spray adhesive during laying. After laying, dry-lay a layer of 350 g / m2 basalt fiber cloth and a layer of 450 g / m2 basalt fiber cloth on the copper mesh surface. S7. Close the molds of S5 and S6. Before injecting glue, check the sealing performance of the molds. Vacuum to 0.06 kPa and maintain the pressure for 20 minutes. After vacuum verification, RTM molding is carried out, and the process parameters are as follows: 1). Injection pressure: 2 bar, injection rate: 80g / time, 25-30 times per minute; injection volume: 30kg; 2) Resin formula: Calculated by mass ratio, MFE-27L pre-cured epoxy resin 100%, M50 curing agent 0.75-2.25; 3) Gel time: Before injection, a casting test should be conducted within the curing agent ratio range to determine the curing agent gel time; 4). After gelation, heat curing is carried out. The curing temperature curve is: room temperature for 8 hours - 45℃ for 1 hour - 55℃ for 1 hour - 60℃ for 2 hours - room temperature; 5). After solidification and cooling, demoulding, the box is completed; S8. The laying process of the box cover is the same as that of the box body. The RTM process parameters are: 1). Injection pressure: 2 bar, injection rate: 80g / time, 25-30 times per minute; injection volume: 20kg; 2) Resin formula: by mass ratio, MFE-27L pre-accelerated epoxy resin 100%, M50 curing agent 1-1.5; 3) Gel time: Before injection, a casting test should be conducted within the curing agent range to determine the curing agent specific gel time; 4). After gelation, heat curing is carried out. The curing temperature curve is: room temperature for 8 hours - 45℃ for 1 hour - 55℃ for 1 hour - 60℃ for 2 hours - room temperature; 5). After solidification and cooling, demoulding, the box cover is completed; S9. Assemble various accessories as required and the basalt box product is completed.

2. The method for forming a large lightweight composite material packaging box according to claim 1, characterized in that: The mold is made of 45# steel. After the mold is closed, the skin cavity thickness is 3.0~5.0mm, and the annular reinforcement cavity thickness is 23±2mm.

3. The method for forming a large lightweight composite material packaging box according to claim 1 or 2, characterized in that: In S7 and S8, gel time: 70±5min in summer and 45±5min in winter.

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