Welding-dewelding reversible composite material connection method
By inserting thermoplastic films on the surface of thermoset composite materials and using heating and ultrasonic welding technology, the welding-desoldering of thermoset composite materials is realized, which solves the problem of non-dissociation in the prior art and promotes the recycling of composite materials. Utilization and circular economy.
Patent Information
- Application Number
- CN202411308237.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-19
- Publication Date
- 2024-12-24
AI Technical Summary
The existing thermoset composite connection methods cannot be dissociated, which limits the recycling and reuse of composite materials and violates the principles of circular economy and sustainable development.
By inserting thermoplastic plastic film on the surface of the thermoset composite material, welding connection is achieved by heating and ultrasonic welding, and desoldering is achieved through microwave and other methods, so as to achieve bidirectional reversibility of the thermoset composite material.
It realizes convenient disassembly, recycling and repair of thermoset composite materials, supports the recycling of composite materials, and complies with the principles of circular economy and sustainable development.
Smart Images
Figure CN119175890A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of composite material manufacturing, and in particular to a welding-desoldering reversible composite material connection method. Background Art
[0002] At present, the recycling and reuse of high-value composite materials for aerospace is becoming a new technical challenge faced by the next step of development and application in the field of composite materials. Among them, the dissociation of composite structures assembled by connection is a key technology that has not yet been solved; of course, mechanical connections such as screws or rivets are not included.
[0003] The current thermosetting composite material connection is mainly achieved through co-curing bonding and secondary bonding, both of which cannot be dissociated (non-destructive decomposition); although thermoplastic composite materials can be welded, they cannot be dissociated at the welding position after welding. Since the connection of the above composite materials does not have the possibility and feasibility of "debonding" or "desoldering", the recycling and reuse of these composite materials can only rely on mechanical crushing or thermal decomposition, which does not conform to the development principles of "circular economy" and "sustainable development". The key is that the current thermosetting composite material connection method is not bidirectionally reversible. Summary of the invention
[0004] The technical problem to be solved by the present invention is: in view of the technical problems existing in the prior art, the present invention provides a welding-desoldering reversible composite material connection method, by embedding a thermoplastic plastic film on the surface of a thermosetting composite material, to achieve bidirectional reversibility of welding connection and desoldering dissociation of the thermosetting composite material.
[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is:
[0006] A welding-desoldering reversible composite material connection method comprises the following steps:
[0007] Step S1, prefabricating a hot melt adhesive film material on the surface of an uncured continuous fiber reinforced high-performance thermosetting resin-based composite material prepreg, and embedding the hot melt adhesive film material on the surface of the thermosetting composite material during the curing process of the thermosetting prepreg;
[0008] Step S2, selecting two sheets of thermosetting composite materials with prefabricated surfaces of hot-melt adhesive films, laminating them, and then welding them by heating, ultrasonic welding or other connection methods to obtain a co-cured welded connection joint of the thermosetting composite materials.
[0009] As a further improvement of the above technical solution:
[0010] Preferably, in the above technical solution, the hot melt adhesive film material is selected from one of EVA, PO, TPU, PES, PVB, and PA.
[0011] In the above technical solution, preferably, the prepreg is a medium-temperature curing thermosetting prepreg or a high-temperature curing thermosetting prepreg, such as an epoxy prepreg, a bismaleimide prepreg, or the like.
[0012] Preferably, in the above technical solution, the temperature difference between the curing temperature of the hot melt adhesive film and the thermosetting composite material is between 0-30 degrees.
[0013] Preferably, in the above technical solution, four-needle zinc oxide whiskers are scattered on the surface of the thermosetting prepreg, with an area coverage of 10%-50%.
[0014] The present invention also provides a welding-desoldering reversible composite material connection method, for a porous fabric reinforced thermosetting resin-based composite material, specifically comprising the following steps:
[0015] Step A1, for a porous fabric-reinforced thermosetting resin-based composite material, prefabricate hot melt adhesive films on the upper and lower surfaces of the porous fabric and press them together, allowing the hot melt adhesive to flow into the porous fabric to form a layer of embedded thermoplastic hot melt adhesive film on the surface of the porous fabric;
[0016] Step A2, placing the fabric embedded with the hot melt adhesive film in step A1 on the outer layer of the multilayer preform, preparing a thermosetting composite material part with a thermoplastic hot melt adhesive film on the surface through the flow, impregnation and curing of the thermosetting resin, and obtaining a porous fabric-reinforced thermosetting composite material welding connection structure.
[0017] The welding-desoldering reversible composite material connection method provided by the present invention has the following advantages compared with the prior art:
[0018] The welding-desoldering reversible composite material connection method of the present invention realizes bidirectional reversibility of welding connection and desoldering dissociation of thermosetting composite materials by embedding a thermoplastic plastic film on the surface of the thermosetting composite material, thereby providing technical guidance and process manufacturing methods for conveniently realizing the disassembly, recycling and repair of thermosetting composite materials. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 It is a schematic diagram of the thermosetting prepreg with a hot melt adhesive film embedded on the surface and the "face-to-face" welding of the present invention.
[0020] Figure 2 It is a schematic diagram of the present invention of compounding thermoplastic films on the upper and lower surfaces of a porous fabric reinforcement.
[0021] Figure 3 It is a schematic diagram of desoldering of the welding position of the welding composite material of the present invention under heating and external force.
[0022] FIG. 4( a ) is a schematic diagram of a typical aviation composite T-rib wall panel of the present invention.
[0023] FIG. 4( b ) is a schematic diagram of a typical aerospace composite material cap-shaped wall panel of the present invention.
[0024] FIG. 4( c ) is a schematic diagram of a typical aviation composite material Z-shaped rib panel of the present invention.
[0025] FIG. 5( a ) is a schematic diagram of a multilayer preform fabric embedded with a hot melt adhesive film.
[0026] FIG5( b ) is a schematic diagram of multi-layer preform fabric welding.
[0027] FIG5( c ) is a schematic diagram of the thermosetting composite material after welding.
[0028] Figure 6 Schematic diagram of the four-needle zinc oxide whisker of the present invention.
[0029] Figure 7 It is a schematic diagram of the four-needle zinc oxide whisker of the present invention deposited on the surface of the prepreg fabric. DETAILED DESCRIPTION
[0030] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.
[0031] The welding-desoldering reversible composite material connection method of the present invention is described by taking a hot melt adhesive film and a thermosetting composite material as an example, and comprises the following steps:
[0032] Step S1, select a hot melt adhesive film and a thermosetting composite material with the same or similar curing temperature, and similar curing temperature means that the temperature difference is between 0-30 degrees. The hot melt adhesive film is prefabricated on the surface of an uncured continuous fiber reinforced high-performance thermosetting resin-based composite prepreg, and during the curing process of the thermosetting prepreg, the hot melt adhesive film is embedded in the surface of the thermosetting composite material; that is, the hot melt adhesive film is prefabricated on the surface of the thermosetting composite material, laying the foundation for the next step of thermoplastic-thermoplastic welding.
[0033] Hot melt adhesive films include EVA (110℃-130℃), PO (130℃-160℃), TPU (120℃-150℃), PES (140℃-160℃), PVB (150℃-170℃), PA (150℃-180℃), etc., which correspond to medium temperature curing epoxy prepreg and high temperature curing epoxy prepreg.
[0034] like Figure 6 and Figure 7As shown, in this embodiment, in order to improve the bonding effect, four-needle zinc oxide whiskers are scattered on the surface of the thermosetting prepreg, with an area coverage rate of 10%-50%. The special geometric structure of the zinc oxide whiskers is used to form a rigid mechanical "anchoring" structure in the interlayer position. Through physical rather than chemical reinforcement, the adhesion between the thermosetting prepreg and the thermoplastic surface film is greatly improved to increase the "roughness" and mechanical "riveting" points.
[0035] In addition, a "mace"-shaped needle-piercing device can be used to pierce holes on the surface of the thermosetting prepreg, creating a basis for the thermoplastic surface film to be hot-melt mechanically embedded into the thermosetting prepreg.
[0036] Alternatively, low-density, three-dimensional "particles" such as nickel foam are sprinkled on the surface of the thermosetting prepreg, which acts similarly to zinc oxide whiskers. Specifically, the nickel foam film is mechanically crushed into small particles with adjustable particle size of about 10-50 microns, and the surface coverage rate of the sprinkler is also 10% to 50%.
[0037] Step S2, select two sheets of thermosetting composite material with prefabricated hot melt adhesive film surfaces, and laminate them "face to face", such as Figure 1 As shown, a thermal connection method is then used for welding, such as heating molding, induction heating, ultrasonic heating and other process methods, to obtain a co-curing welding connection of the thermosetting composite material.
[0038] Since zinc oxide, nickel foam, etc. will generate heat under the action of microwaves, the heat can heat the thermoplastic adhesive layer, melt the thermoplastic material in the middle of the thermosetting material, and then realize the separation and dissociation of the thermosetting material. Therefore, microwave welding is preferably used, which is also convenient for desoldering.
[0039] The welding-desoldering reversible composite material connection method of the present invention is described by taking a porous fabric-reinforced thermosetting resin-based composite material as an example, and comprises the following steps:
[0040] Step A1, for porous fabric reinforced thermosetting resin-based composite materials, such as plant fiber cloth reinforced composite materials, the hot melt adhesive film can be prefabricated on the upper and lower surfaces of the porous fabric and pressed together at a temperature close to the melting temperature of the hot melt adhesive film, so that the hot melt adhesive flows and "permeates" the porous fabric, thereby embedding a layer of thermoplastic hot melt adhesive film on the surface of the porous fabric, and even forming multiple layers.
[0041] Step A2, placing the fabric embedded with the hot melt adhesive film in step A1 on the outermost layer of the multilayer preform, and preparing a thermosetting composite material product with a hot melt adhesive film on the surface by flow impregnation of thermosetting resin. Select two thermosetting composite materials with hot melt adhesive film prefabricated surfaces and laminate them "face to face", such as Figure 1As shown, a thermal connection method is then used for welding, such as heating molding, induction heating, ultrasonic heating and other process methods, to obtain a porous fabric reinforced thermosetting composite material welding connection structure.
[0042] During the manufacturing process, maintenance, repair and replacement process, or recycling and reuse of the welded composite material structure of the present invention, two parts welded by the hot-melt adhesive film can be desoldered and separated by simply heating and applying appropriate external force.
[0043] After desoldering, if necessary, a "fresh" hot melt adhesive welding film can be appropriately filled in the hot melt adhesive film position of the composite material, so that welding can be performed again according to the steps.
[0044] Example 1
[0045] First, epoxy resin prepreg (YHP-170) is laid on the mold to form a T-type, C-type, Z-type or cap profile (II), etc., as shown in (a), (b), and (c) of Figure 4. Then, a hot melt adhesive film (polyvinyl butyral PVB film) is pre-fixed at the position where the skin and the ribs are to be welded, and then both are cured. After curing, the two are placed in the mold according to the connection structure design, and then the two are welded into one by co-curing means.
[0046] In some cases, a layer of peeling film can be pre-laid on the surface of the PVB hot melt adhesive film to ensure that the PVB film is clean and not contaminated, and solidifies along with the prefabricated parts. Before welding, be sure to remove the pre-laid peeling film before starting the welding operation.
[0047] In some examples, conventional thermoplastic welding techniques such as induction welding, ultrasonic welding, and even resistance welding may be used to locally weld the ribs to the skin.
[0048] In some instances, the two composite parts to be welded do not necessarily need to be welded after curing is completed, but can be "dry-wet" co-curing welding, such as the welding of "dry" ribs and "wet" skins commonly used in the aviation industry, or vice versa. In this case, the "dry" and "wet" parts need to be placed face to face in a suitable mold, and then welded using conventional co-curing methods for thermosetting composite materials, such as autoclave molding or compression molding.
[0049] When these welded structural parts expire or are ready for recycling, they can be desoldered and separated. At this time, the welded parts are heated to a temperature above the softening temperature of the PVB hot melt adhesive film and appropriate separation force is applied to desolder and separate the welded structure. Figure 3 .
[0050] In some instances, the assembly of the ribs may require repeated positioning and correction. In this case, the welded structure can be separated by heating the welded portion to the softening or melting temperature of the hot melt adhesive film and applying a normal or separation force, and then, final welding can be performed as needed.
[0051] For composite parts separated by desoldering, if they need to be used again (old parts can be reused and recycled), the desoldering parts can be properly cleaned, and then a layer of the same type of hot melt adhesive film can be applied, and then welded again according to the above process flow, so as to give full play to the deep utilization value of composite parts. In this case, the two parts to be welded are usually one new and one old, or two old parts.
[0052] Example 2
[0053] Polyvinyl Butyral (PVB) is selected as the hot melt adhesive film material. First, it is applied to the surface of any high-temperature epoxy prepreg. There is no limit on the number and thickness of the epoxy prepreg. The thickness of the PVB film varies from 30 to 300 μm. If necessary, a layer of peel-off film can be applied for protection or not. Then, it is co-cured according to the curing system of the high-temperature epoxy prepreg (for example, about 180°C) to obtain a preform with a PVB plastic film on the surface (see Figure 1 ).
[0054] like Figure 1 , two preforms with PVB film (without peeling film) are placed face to face for induction welding. In one example, the induction welding operating frequency is 600kHz, the voltage is 220V, the power is between 1-2kW, and the coil feed speed is 2mm / s. Depending on the thickness of the PVB film, the thickness of the PVB weld is different. For a sample with a measured film thickness of 250μm, the thickness of the PVB weld is about 200-400μm; for a 75μm PVB film, the thickness of the weld is about 130-180μm. Subsequently, the shear-tensile joint strength of the welded joint (20×20mm single-sided overlap) was tested (see Figure 1 ), for a sample with a welding film thickness of 250mm, the welding joint strength is 22MPa; for a sample with a film thickness of 75mm, the joint strength is 13MPa.
[0055] In some instances, ultrasonic welding technology is used. Depending on the thickness of the PVB film, the thickness of the PVB ultrasonic weld is also different. For a sample with a measured film thickness of 250μm, the PVB weld thickness is about 100-200μm; for a 75μm PVB film, the weld thickness is about 120-180μm. Then ultrasonic welding is performed. For a 75μm thick PVB film, a 250μm thick planar energy director is placed between the parts to be welded to ensure that heat is preferentially generated at the welding interface; for a 250μm thick PVB film sample, no energy director is placed. The average welding vibration time of the 75μm and 250μm PVB welding samples is approximately 300 milliseconds and 250 milliseconds, respectively. Subsequently, the shear-tensile joint strength of the welded joint was tested. For a specimen with a welding film thickness of 250 mm (20×20 mm single-sided overlap), the welded joint strength was 29 MPa; while for a specimen with a film thickness of 75 mm (25 wide×12.5 mm single-sided overlap), the joint strength was 25 MPa.
[0056] In some instances, a simpler molded welding connection is used. In this case, the two preforms to be welded are placed in a suitable mold and co-cured at a process condition of about 180°C / 2bar / 1hr. Without a vacuum bag, a composite welded connection joint of epoxy resin / PVB welding layer / epoxy resin can be obtained. The strength of the welded joint (20mm×20mm) is about 20MPa.
[0057] Desoldering, separation and reconnection. The glass transition temperature of PVB hot melt adhesive film is between 60℃-85℃, and the melting range is about 150℃-170℃. It has good flexibility, high tensile strength, impact strength and bonding strength, so the welding strength of the above joints is very high. When desoldering, just put the joint at a suitable temperature, such as above 150℃, and apply external force at the same time to achieve desoldering and separation. The higher the temperature, the smaller the desoldering force. After desoldering, if necessary, repeat the above steps to weld the joint again.
[0058] Example 3
[0059] A bidirectional reversible welding-desoldering technology for porous fabric reinforced thermosetting resin-based composites
[0060] As shown in FIG5 , thermoplastic films, especially fiber-reinforced plastic films, such as polyethylene / glass fiber films, or hot-melt adhesive films, are pre-inserted into the upper and lower parts of a porous fabric where welding is required, and pressed together under suitable process conditions (as shown in the figure). Then, suitable thermosetting resins, such as vinyl resins, epoxy resins, etc., are introduced by vacuum, and then cured to obtain a preform with thermoplastic materials embedded on the surface and inside (the number of layers is optional).
[0061] In this embodiment, the porous fabric selected is coarse ramie cloth, the vacuum-introduced resin is commercially available EPOLAM 2040 resin that cures at room temperature and a matching curing agent; the polyethylene / glass fiber membrane is homemade, with a thickness of 0.8 μm and a glass fiber volume fraction of 30%. Then, a piece of the same thermoplastic film or hot-melt adhesive film is placed at the location where welding is required, and the plastic film or adhesive film is molded and pressed at a suitable temperature to weld the two together. In this embodiment, whether it is the prefabricated polyethylene plastic film or the welding process, the process conditions are all optional at 130°C / 1MPa / 30s-4min. After shear tensile test (lap length 30mm×15mm, welding strength is about 1.5MPa-2MPa.
[0062] Desoldering and reconnection: preheat the welded joint at 80℃ for 1min, and apply a little external force to dissociate and desolder the joint. Repeat the above operation and re-weld the joint, thus achieving a bidirectional reversible connection.
[0063] The above implementation cases are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, they are not intended to limit the present invention. Therefore, any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.
Claims
1. A welding-desoldering reversible composite material connection method, characterized in that: The following steps are involved: Step S1, prefabricating a hot melt adhesive film material on the surface of an uncured continuous fiber reinforced high-performance thermosetting resin-based composite material prepreg, and embedding the hot melt adhesive film material on the surface of the thermosetting composite material during the curing process of the thermosetting prepreg; Step S2, selecting two sheets of thermosetting composite materials with prefabricated surfaces of hot-melt adhesive films, laminating them, and then welding them by heating, ultrasonic welding or other connection methods to obtain a co-cured welded connection joint of the thermosetting composite materials.
2. The welding-desoldering reversible composite material connection method according to claim 1, characterized in that: The hot melt adhesive film material is selected from one of EVA, PO, TPU, PES, PVB, and PA.
3. The welding-desoldering reversible composite material connection method according to claim 1, characterized in that: The prepreg is a medium temperature curing thermosetting prepreg or a high temperature curing thermosetting prepreg.
4. The welding-desoldering reversible composite material connection method according to claim 1, characterized in that: The temperature difference between the curing temperature of the hot melt adhesive film and the thermosetting composite material is between 0 and 30 degrees.
5. The welding-desoldering reversible composite material connection method according to claim 1, characterized in that: Four-needle zinc oxide whiskers are scattered on the surface of the thermosetting prepreg, with an area coverage of 10%-50%.
6. A welding-desoldering reversible composite material connection method, characterized in that: For the porous fabric reinforced thermosetting resin-based composite material, the method specifically includes the following steps: Step A1, for a porous fabric-reinforced thermosetting resin-based composite material, prefabricate hot melt adhesive films on the upper and lower surfaces of the porous fabric and press them together, allowing the hot melt adhesive to flow into the porous fabric to form a layer of embedded thermoplastic hot melt adhesive film on the surface of the porous fabric; Step A2, placing the fabric embedded with the hot melt adhesive film in step A1 on the outer layer of the multilayer preform, preparing a thermosetting composite material part with a thermoplastic hot melt adhesive film on the surface through the flow, impregnation and curing of the thermosetting resin, and obtaining a porous fabric-reinforced thermosetting composite material welding connection structure.