A method for forming complex structural parts of dynamically cross-linked polymer-based composite materials

Abstract

The present invention relates to the field of composite materials, and specifically to a method for forming complex structural parts of dynamically cross-linked polymer-based composite materials. Specifically, the method comprises the following steps: loading a dynamically cross-linked polymer prepolymer on a fiber cloth to obtain a dynamically cross-linked polymer preimpregnated fiber cloth; laying the dynamically cross-linked polymer preimpregnated fiber cloth layer by layer, and curing the cloth to obtain a flat dynamically cross-linked polymer-based composite material; using the dynamically cross-linked polymer-based composite material as a simple flat plate unit, placing the dynamically cross-linked polymer-based composite material in a mold, and reshaping and shaping the molded parts by hot pressing to obtain parts of different shapes; assembling parts of different shapes according to complex structural parts, and connecting them at the connection interface by hot pressing welding or stock solution bonding to obtain complex structural parts. The present invention provides a simple and efficient new method for the preparation of complex structural parts of dynamically cross-linked polymer-based composite materials, which overcomes the problems of cumbersome preparation of complex structural parts, low fault tolerance, and poor flexibility in the prior art.

Description

Technical Field

[0001] The invention belongs to the field of composite materials, and in particular relates to a method for forming complex structural parts of dynamically cross-linked polymer-based composite materials. Background Art

[0002] Thermosetting resin-based composite materials are widely used in the aerospace and automotive manufacturing industries due to their excellent properties of high specific strength, high specific stiffness, high temperature resistance and fatigue resistance. In the aerospace field, thermosetting resin-based composite materials for aircraft structures can reduce aircraft weight and improve fuel efficiency, and are one of the key technologies for improving the core performance of the new generation of large aircraft. In the automotive manufacturing field, thermosetting resin-based composite materials have huge development potential in lightweight manufacturing. They can not only reduce fuel consumption and carbon emissions, but also improve driving comfort, and have received widespread attention from automakers. With the increasing application of thermosetting resin-based composite materials, more and more complex structures are being made of composite materials, and the difficulty of manufacturing complex structural parts based on thermosetting resin-based composite materials is also gradually increasing. So far, how to manufacture complex structural parts with complex shapes has become an important technical difficulty in the field of industrial production.

[0003] At present, there are two main methods for obtaining complex structural parts in the industrial field. The first is to use a machine to accurately lay out the wire and tape, and then directly solidify and shape them into complex structural parts with complex shapes. The second method is to manually load uncured thermosetting resin-based composite materials into customized molds. When laying the layers, the thermosetting resin-based composite materials need to be tediously laid and adjusted according to the shape of the complex structural parts. The mold is placed in an autoclave, and the autoclave provides the required temperature and pressure for solidification and molding to obtain complex structural parts. However, automatic laying technology is currently difficult to promote. At the same time, the more complex the shape of the complex structural parts, the more complicated the laying process is, resulting in low efficiency. The hot pressing process requires customized molds for the curing and molding of complex structural parts, and there are many process flows. Manually laying up uncured thermosetting resin-based composite material blanks is time-consuming and inefficient, which greatly increases the production cost. In addition, no matter what molding method is used to prepare the thermosetting resin-based composite material plate or complex structural part, once it is cured and formed, its shape is permanently fixed and cannot be reconstructed again, which leads to its single function. It not only limits the flexible processing and molding of thermosetting resin-based composite materials, but also greatly reduces the application potential of thermosetting resin-based composite materials after molding.

[0004] In the industrial field, heterogeneous bonding or mechanical connection methods are usually used to further assemble parts into a complex structure. Traditional connection methods have significant inherent defects. Mechanical connection methods include riveting and bolting. Regardless of which method is used, holes need to be opened in the parts, which destroys the integrity of the complex structure. In addition, the area around the hole is prone to significant stress concentration during service, and the use of mechanical connection fasteners greatly increases the weight of the complex structure and destroys the flatness and aesthetics of the surface of the part. Traditional heterogeneous bonding uses heterogeneous adhesives to connect two or more parts together, which requires special treatment of the bonding surface in advance. More importantly, heterogeneous adhesives cannot form chemical bonds with thermosetting resin-based composite materials, that is, they cannot form a whole. Each layer is independent, resulting in poor connection strength. In summary, the limitations of these connection methods are the key factors that restrict the efficient and high-quality processing of complex composite structures.

[0005] In addition, in addition to the assembly and molding of parts, the manufacturing of complex structural parts also includes integrated molding methods, such as using 3D printing technology to directly print out molded complex structural parts, or using the idea of ​​integral molding of thermosetting resin-based composite materials. During the design and manufacturing process, the flexibility of thermosetting resin-based composite materials before curing is fully utilized, and the corresponding parts are combined in advance for co-curing and co-bonding to achieve integrated molding of complex structural parts. However, 3D printing technology has stringent requirements for thermosetting resin-based composite materials. Currently, only a small amount of thermosetting resin matrices can meet the printing requirements. At the same time, the weak interlayer bonding performance leads to relatively poor mechanical properties of 3D printed thermosetting resin-based composite materials. Moreover, the overall molding curing idea has low fault tolerance and poor flexibility. Although it can reduce dozens or even hundreds of parts to a few parts, it also means that once problems occur during the molding process, a large amount of material will be wasted, resulting in a significant increase in costs. Summary of the Invention

[0006] In response to the deficiencies in the above-mentioned prior art, the present invention provides a method for forming complex structural parts of dynamically cross-linked polymer-based composite materials. The present invention loads a dynamically cross-linked polymer prepolymer on a fiber cloth to obtain a dynamically cross-linked polymer preimpregnated fiber cloth, lays the dynamically cross-linked polymer preimpregnated fiber cloth layer by layer and solidifies it to obtain a flat plate-shaped dynamically cross-linked polymer-based composite material, and then reshapes and shapes the flat plate-shaped dynamically cross-linked polymer-based composite material to obtain parts of different shapes. The parts of different shapes are then assembled according to the complex structural parts and connected by hot pressing welding or liquid bonding to obtain complex structural parts. The present invention provides a new shape reshaping and connection assembly method based on dynamically cross-linked polymer materials. The dynamically cross-linked polymer materials can undergo dynamic covalent bond exchange reactions under high temperature and high pressure, thereby realizing efficient and high-quality molding of complex structural parts using parts of different shapes, overcoming the problems of cumbersome preparation, low fault tolerance and poor flexibility of complex structural parts of thermosetting resin-based composite materials in the prior art.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A method for forming a complex structural part of a dynamically cross-linked polymer-based composite material comprises the following steps:

[0009] After laying the dynamically cross-linked polymer material pre-impregnated fiber cloth layer by layer and curing it, a flat plate-shaped dynamically cross-linked polymer-based composite material is obtained;

[0010] Among them, the dynamically cross-linked polymer pre-impregnated fiber cloth is a fiber cloth in which the dynamically cross-linked polymer prepolymer is loaded;

[0011] The dynamically cross-linked polymer-based composite material is used as a simple flat plate unit, and the dynamically cross-linked polymer-based composite material is placed in a mold. It is reshaped and processed for 0.5-6 hours at 60-240°C and 1-15MPa. During the reshaping process, the dynamic covalent bonds inside the dynamically cross-linked polymer material of the dynamically cross-linked polymer-based composite material are activated to undergo exchange reactions, thereby changing the topological structure of the internal network of the dynamically cross-linked polymer material, releasing the stress caused by deformation, achieving permanent deformation, and completely reshaping the shape to produce parts of different shapes.

[0012] Components of different shapes and / or flat-plate dynamically cross-linked polymer-based composite materials are assembled according to complex structural parts. Hot pressing welding or stock solution bonding is used at the connection interface to activate the dynamic covalent bonds between components of different shapes to cause exchange reactions, forming an interface with the synergy of covalent bonds, intermolecular forces and physical entanglement to obtain complex structural parts.

[0013] Preferably, the connection interface is formed by laminating together a number of dynamically cross-linked polymer-based composite materials of components of different shapes.

[0014] Preferably, the operation of the hot pressing welding method is: hot pressing the connection interface at 60-240° C. and 3-18 MPa for 2-8 hours.

[0015] Preferably, the operation of the stock solution bonding method is: applying the dynamically cross-linked high molecular prepolymer to the connection interface between parts of different shapes, and heating the connection interface at 80-200° C. for 5-120 minutes.

[0016] Preferably, components of different shapes can also be connected at the connection interface using traditional heterogeneous bonding methods or mechanical connection methods, that is, the technical solution of the present invention is also applicable to the heterogeneous bonding methods or mechanical connection methods of the prior art.

[0017] Preferably, the dynamically cross-linked polymer-based composite material is placed in front of the mold and is subjected to a heating and softening treatment.

[0018] Preferably, the heating and softening treatment is performed by heating and softening at 100-160° C. for 10-60 minutes.

[0019] Preferably, the dynamic covalent bond of the dynamically cross-linked high molecular prepolymer is selected from an ester bond, a boron-oxygen bond, an imine bond, a disulfide bond, a borate ester bond, a thioester bond, a thioether bond, an amide bond or a urea bond.

[0020] Preferably, the dynamically cross-linked polymer prepolymer can also be incorporated with a reinforcing phase material, which includes a fiber material and a particulate material. The fiber material is selected from carbon fiber, glass fiber, aramid fiber, high-strength polyethylene fiber, ceramic fiber, metal fiber, carbon nanotube fiber, boron fiber, liquid crystal polymer fiber or natural fiber, and the particulate material is selected from carbon nanotubes, carbon black, graphite particles, graphene, cellulose nanoparticles, rubber particles, aluminum hydroxide particles, magnesium hydroxide particles, silver particles, nickel particles, silica, ceramic particles, glass particles, carbonate particles or silicate clay.

[0021] Preferably, the dynamically cross-linked polymer prepolymer is loaded on the fiber cloth by spray molding, hand lay-up molding, vacuum bag molding, autoclave molding, compression molding, resin transfer molding (RTM), vacuum assisted resin transfer molding (VARTM), co-curing molding, pultrusion molding or injection molding.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention loads a dynamically cross-linked polymer prepolymer on a fiber cloth to obtain a dynamically cross-linked polymer pre-impregnated fiber cloth, lays the dynamically cross-linked polymer pre-impregnated fiber cloth layer by layer and solidifies it to obtain a flat plate-shaped dynamically cross-linked polymer-based composite material, and then reshapes the flat plate-shaped dynamically cross-linked polymer-based composite material to obtain parts of different shapes, and then assembles the parts of different shapes according to complex structural parts, and connects them by hot pressing welding or stock solution bonding to obtain complex structural parts. The present invention uses the dynamically cross-linked polymer material in the thermosetting resin-based composite material as a raw material, and the dynamic covalent bonds inside the dynamically cross-linked polymer material can undergo an exchange reaction, so that the dynamic covalent bonds of parts of different shapes can continue to undergo an exchange reaction after the reshaping and shaping treatment, and realizes efficient and high-quality manufacturing and molding without the need for any heterogeneous material assistance and mechanical fastening, overcoming the technical defects of the prior art heterogeneous bonding or mechanical connection.

[0024] In addition, considering that the complex structural parts in the existing technology are made by curing the entire uncured thermosetting resin-based composite material, which has the problem of not being able to be reprocessed and reshaped, the present invention assembles parts of different shapes and then connects them using hot pressing welding or liquid bonding to obtain complex structural parts, breaking through the limitations of traditional complex structural part molding methods and realizing modular part processing. The present invention is simpler to operate, has a lower fault tolerance, and makes the molding of complex structural parts more flexible.

[0025] 2. In the present invention, any single component of any shape can be hot-pressed by a simple flat plate unit, and there is no need to perform tedious laying and adjustment according to the shape of complex structural parts during layering, which makes the processing of basic components modular, greatly simplifies the process and improves efficiency.

[0026] 3. The method provided by the present invention breaks through the limitation that the functions of complex structural parts of traditional thermosetting resin-based composite materials are fixed after shape molding, so that the complex structural parts after molding can still be reshaped and reassembled into new complex structural parts, enabling them to be used in various scenarios, greatly enhancing the application potential of dynamically cross-linked polymer-based composite materials.

[0027] 4. The method provided by the present invention does not require opening holes to damage complex structural parts. While maintaining the smooth and beautiful surface of the complex structural parts, it also avoids the occurrence of stress concentration at the hole edges and reduces the risk of material damage.

[0028] 5. The method provided by the present invention does not require the use of additional fasteners, which reduces the production cost while reducing the weight of complex structural parts, which is of great significance for obtaining "lightweight" complex structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1The figure is a flow chart of the complex structure molding method of the dynamic cross-linked polymer-based composite material of the present invention.

[0030] Figure 2 This is a diagram showing the reshaping principle of the dynamic cross-linked polymer material of the present invention.

[0031] Figure 3 This is a flow chart of the method for forming parts of different shapes according to the present invention.

[0032] Figure 4 The figure is a flow chart of the hot pressing welding and assembly process of the components of the present invention.

[0033] Figure 5 This is a flow chart of the molding method of the dynamically cross-linked polymer-based composite material according to Examples 1 to 3 of the present invention. DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0035] Many devices in the aerospace and automotive fields contain composite structural parts with very complex shapes and structures, such as aircraft wall panels, automobile anti-collision beams and energy absorption boxes. These structural parts not only greatly reduce the weight of the overall equipment, achieving lightweight aircraft or automobiles, but also have excellent strength, stiffness and impact resistance. The method provided by the present invention can be used to manufacture these composite structural parts efficiently and with high quality.

[0036] The following is an explanation of the mechanism of action:

[0037] In the present invention, the reshaping and assembly method of the dynamically cross-linked polymer-based composite material is as follows Figure 1 As shown, simple flat plate units are reshaped into parts of different shapes under high temperature and high pressure conditions, and then the corresponding parts of different shapes are connected and assembled, and complex structural parts are formed by hot pressing welding or raw liquid bonding. Parts of different shapes can also be connected and assembled by traditional heterogeneous bonding or mechanical bonding. Of course, hot pressing welding or raw liquid bonding is a better technical solution.

[0038] Dynamically cross-linked polymer material is a type of thermosetting resin material. The method of the present invention utilizes the dynamic covalent bonds in the dynamically cross-linked polymer material to carry out an exchange reaction. After the dynamically cross-linked polymer material is deformed by force, the stress generated by the deformation is stored in the network, causing it to be unable to maintain the deformed state. When the dynamic network in the dynamically cross-linked polymer material is activated by high temperature, a bond exchange reaction occurs between the dynamic covalent bonds. After the new bonds are formed, the old bonds are broken. In this process, the stress stored in the dynamically cross-linked polymer material is released, causing the network to transform into a stress-free state, realizing network reconstruction, and finally achieving permanent deformation, thereby achieving the effect of shape reshaping, such as Figure 2 shown.

[0039] The method of the present invention is suitable for the reshaping and assembly of dynamically cross-linked polymer-based composite materials. Reinforcement phase materials can also be added to the dynamically cross-linked polymer prepolymer to improve the overall performance. The reinforcement phase materials include fiber materials and particulate materials. The fiber materials are selected from carbon fibers, glass fibers or polymer fibers, and the particulate materials are selected from carbon nanotubes, silica, ceramic particles or silicate clay.

[0040] The experimental operating conditions are described below:

[0041] In the present invention, the recommended temperature for the shaping and reshaping process is 60-240°C. In actual operation, it is carried out at temperatures including 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, and 240°C as needed. Different temperature conditions will affect the shaping and reshaping time and the shaping and reshaping effect. The recommended time is 0.5-6h. If the shaping and reshaping temperature is too low or the time is too short, the reshaping effect of the dynamically cross-linked polymer-based composite material will be significantly reduced, which is specifically manifested in shape rebound and retention of internal residual stress, making it impossible to assemble with other parts of different shapes. Even if assembled and formed, it will affect the dimensional stability of complex structural parts, posing a hidden danger for actual service use. On the contrary, too high a shaping and reshaping temperature or too long a time may cause aging of the dynamically cross-linked polymer material and reduce the overall mechanical properties of the complex structural parts.

[0042] The recommended pressure for reshaping is 1MPa-15MPa. Providing appropriate pressure can induce the release of stress inside the dynamic cross-linked polymer material while ensuring sufficient deformation of the dynamic cross-linked polymer-based composite material, thereby achieving the reshaping effect. Too little pressure may cause the dynamic cross-linked polymer-based composite material to deform too little and be unable to be shaped into the target shape, while too much pressure will destroy the dynamic cross-linked polymer-based composite material and cause the entire dynamic cross-linked polymer-based composite material to be crushed.

[0043] Hot-press welding or stock solution bonding methods are used to join components of different shapes. Hot-press welding requires high temperature and high pressure. High pressure ensures a tight fit at the interface, while high temperature activates dynamic covalent bond exchange reactions at the interface, forming a synergistic interface characterized by covalent bonds, intermolecular forces, and physical entanglement. Stock solution bonding requires high temperature. Similarly, high temperature activates dynamic covalent bond exchange reactions at the interface, forming a synergistic interface characterized by covalent bonds, intermolecular forces, and physical entanglement. Hot-press welding eliminates the need for heterogeneous adhesives to assemble complex structural components. Stock solution bonding, on the other hand, only requires a dynamically cross-linked polymer prepolymer from a dynamically cross-linked polymer-based composite material as an adhesive. Both hot-press welding and stock solution bonding overcome the technical drawbacks of mechanical joining methods. Traditional heterogeneous bonding or mechanical joining methods can also join components of different shapes, but the resulting performance is not as good as with hot-press welding or stock solution bonding.

[0044] In the present invention, the recommended temperature for the hot pressing welding method is 60-240°C. In actual operation, it is carried out at temperatures including 60°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, and 240°C as needed; the recommended time for the connection process is 2-8 hours. If the hot pressing time is too short or the temperature is too low, the bond exchange reaction at the connection interface may be insufficient, and sufficient dynamic covalent bonds cannot be formed, thereby failing to provide sufficient connection strength. On the contrary, if the temperature is too high or the connection time is too long, the dynamically cross-linked polymer material may oxidize at high temperature, resulting in thermal damage, thereby reducing the mechanical properties of complex structural parts.

[0045] The recommended pressure for hot pressing welding is 3MPa-18MPa. Too low a pressure can lead to loose fit between components, making it difficult for molecular chains to diffuse at the interface and forming sufficient dynamic covalent bonds to provide the required connection strength. Higher pressures improve the connection and increase efficiency, but exceeding 18MPa can also cause the dynamically cross-linked polymer-based composite material to collapse and be destroyed, affecting performance and usability.

[0046] The stock solution bonding method requires a temperature of 80-200°C, no pressure assistance is required, and successful bonding can be achieved after heating for 5-120 minutes. If the temperature is too low or the time is too short, sufficient dynamic covalent bonds will not form at the bonding interface, resulting in poor bonding and low bonding strength.

[0047] The innovations of this application are further described below:

[0048] 1. Compared with the prior art, the mold used in the present invention is a component manufacturing mold, which is used to reshape the flat-plate dynamically cross-linked polymer-based composite material. Therefore, it is only necessary to consider the shape of the component when designing the mold. Therefore, the mold structure is simple and the mold customization requirements are low, which effectively reduces the cost. The mold of the prior art realizes the overall solidification molding of complex structural parts, so the mold structure needs to be customized according to the overall structure of the complex structural parts. The mold structure is complex and the mold customization requirements are high, which increases the cost.

[0049] 2. Compared with the prior art, the molds of the prior art contain flowing thermosetting resin-based composite materials. Therefore, when designing the mold, factors such as curing and molding must also be considered. For example, to prevent the internal thermosetting resin-based composite materials from leaking out, the mold edges must be equipped with high-quality sealing strips, and the joints between the molds must be well-matched to avoid gaps. Alternatively, considering that the layers cannot shift, the mold surface must be highly flat and smooth to ensure that the layers are tightly compacted and do not slip. These all place high demands on the mold design. The present invention, however, reshapes the solidified flat plate-shaped dynamic cross-linked polymer-based composite material, and does not have the technical problems of the prior art mentioned above. Therefore, the mold operation of the present invention is simpler.

[0050] 3. Compared with the existing technology, the existing technology uses heterogeneous bonding or mechanical connection to achieve connection. The present invention uses hot pressing welding or stock solution bonding. Both hot pressing welding and stock solution bonding activate dynamic covalent bonds to produce exchange reactions, forming an interface with the coordination of covalent bonds, intermolecular forces and physical entanglement, and then forming a whole, overcoming the technical defects of the existing technology heterogeneous bonding or mechanical connection.

[0051] 4. Thermosetting resin-based composite materials have an irreversible permanent covalent cross-linking network, which makes it difficult to perform secondary processing and repeated shaping once the thermosetting resin-based composite materials are cured and formed. The present invention uses dynamic cross-linked polymer-based composite materials as raw materials. The dynamic cross-linked polymer materials can continue to undergo covalent bond exchange reactions after reshaping and shaping, thereby realizing secondary processing and repeated shaping.

[0052] The technical solution of the present invention is described in detail below, specifically as follows:

[0053] Acquisition of parts of different shapes:

[0054] S1. Simple flat plate units of different sizes are cut out from the dynamically cross-linked polymer-based composite material as components for the final assembly into complex structural parts.

[0055] S2. preheating the dynamically cross-linked polymer-based composite material at 100-160° C. for 5-30 minutes to soften the dynamically cross-linked polymer-based composite material for easy reshaping and shaping, thereby obtaining a softened dynamically cross-linked polymer-based composite material;

[0056] S3, press the softened dynamically cross-linked polymer-based composite material into the arc-shaped groove of the lower mold, cover the upper mold, heat it to 60-240℃, and then apply 1-15MPa pressure to close the mold and hot press for 0.5-6h; after the hot pressing treatment, wait for the upper mold and the lower mold to cool naturally to room temperature, and then parts of different shapes are obtained, realizing the reshaping from flat plate to different morphological plates. The reshaping steps are as follows: Figure 3 shown.

[0057] Taking single lap joint as an example, two pieces of dynamic cross-linked polymer-based composite materials are connected by hot pressing welding method, such as Figure 4 As shown, the following steps are included:

[0058] S1. After cleaning the surfaces of two pieces of dynamically cross-linked polymer-based composite materials to be connected (60 mm long × 10 mm wide × 2 mm thick), scrub the connection interface with industrial alcohol. After air drying or heat drying, select a 10 mm × 10 mm connection interface, stack the connection interfaces of the two pieces of dynamically cross-linked polymer-based composite materials, and bind and fix the stacked area with high-temperature tape. Place a gasket under the suspended area of ​​the dynamically cross-linked polymer-based composite material stacked on the upper layer, with the gasket and the dynamic cross-linked polymer-based composite material having the same thickness to ensure uniform force on the connection interface, thereby obtaining a part to be formed;

[0059] S2. Place the part to be formed into a hot pressing mold and hot press it at 60-240°C and 3-18MPa for 2-8 hours. After the hot pressing treatment is completed, wait for the hot pressing mold to cool naturally to room temperature to obtain a single lap component connected by two flat-plate dynamically cross-linked polymer-based composite materials.

[0060] Taking single lap joint as an example, two flat-plate dynamically cross-linked polymer-based composite materials are connected using the stock solution bonding method, which includes the following steps:

[0061] S1. Clean the surfaces of two pieces of dynamically cross-linked polymer-based composite materials to be connected (60 mm long × 10 mm wide × 2 mm thick), scrub the connection interface with industrial alcohol, and after air drying or heat drying, select a 10 mm × 10 mm connection interface;

[0062] S2. Coat a dynamically cross-linked polymer prepolymer on the connection interface of one of the dynamically cross-linked polymer-based composite materials. The coated dynamically cross-linked polymer prepolymer has the same composition as the dynamic cross-linked polymer prepolymer of the dynamically cross-linked polymer-based composite material. Fit the two dynamically cross-linked polymer-based composite materials at the connection interface, press to squeeze out excess dynamic cross-linked polymer prepolymer, wipe off excess dynamic cross-linked polymer prepolymer remaining near the connection interface, and heat at 80-200°C for 5-120 minutes. After the dynamically cross-linked polymer prepolymer is completely cured, a single-lap component formed by connecting two flat-plate dynamically cross-linked polymer-based composite materials is obtained.

[0063] At the same time, parts of different shapes can be connected at the connection interface using traditional heterogeneous bonding methods or mechanical connection methods.

[0064] The technical solution is further explained using an embodiment below. The present invention uses carbon fiber cloth as a reinforcing fiber cloth. The carbon fiber cloth of the present invention is purchased from Zhongfu Shenying Carbon Fiber Co., Ltd., and is specifically shown below:

[0065] The dynamically cross-linked polymer-based composite materials of Examples 1-3 of the present invention were prepared according to the following steps:

[0066] (1) heating bisphenol A epoxy monomer to melt at 100° C., heating glutaric anhydride to melt at 80° C., stirring and mixing the heated and melted bisphenol A epoxy monomer and glutaric anhydride at 130° C., cooling to 90° C., adding zinc acetylacetonate hydrate catalyst, and further heating and stirring at 90° C. for 30 minutes to obtain a dynamically crosslinked polymer prepolymer;

[0067] The molar ratio of the epoxy functional group of the bisphenol A epoxy monomer, the acyl functional group of the glutaric anhydride, and the catalyst zinc acetylacetonate hydrate is 1:1:0.05:

[0068] (2) using a prepreg process to load a dynamically cross-linked polymer prepolymer on a carbon fiber cloth to obtain a dynamically cross-linked polymer prepreg fiber cloth, and laying the dynamically cross-linked polymer prepreg fiber cloth layer by layer until the number of dynamically cross-linked polymer prepreg fiber cloth is 4, thereby obtaining a composite material blank;

[0069] (3) The composite material blank was pre-cured at 130°C and 3 MPa for 2 h, and then deep-cured at 160°C and 3 MPa for 4 h to obtain a dynamically cross-linked polymer-based composite material.

[0070] Example 1

[0071] A method for forming a complex structural part of a dynamically cross-linked polymer-based composite material comprises the following steps:

[0072] S1. Cut out simple flat plate units of different sizes from the obtained dynamic cross-linked polymer matrix composite material, such as Figure 5 As shown in step 1.

[0073] S2. preheating the simple flat plate unit at 160° C. for 20 min to soften the dynamically cross-linked polymer-based composite material to facilitate reshaping and shaping, thereby obtaining a softened dynamically cross-linked polymer-based composite material;

[0074] S3. Press the softened dynamically cross-linked polymer-based composite material into the arc-shaped groove of the lower mold, cover it with the upper mold, heat it to 200°C, and then slowly apply a micro-pressure of 1MPa until the upper and lower molds are completely fitted together, then increase the pressure to 8MPa and hot press for 6h; after the hot pressing treatment, wait for the upper and lower molds to cool naturally to room temperature, and parts of different shapes are obtained, realizing the reshaping from flat plates to plates of different shapes. The reshaping steps are as follows: Figure 5 As shown in step 2.

[0075] Then, the surfaces of parts of different shapes are cleaned, and the connection interfaces are scrubbed with industrial alcohol. After natural air drying or heat drying, various connection methods can be used to assemble and shape them to obtain complex structural parts.

[0076] for Figure 5 For medium-complex structural parts ① and ②, the overall size of the complex structural parts is small and the contact area between the parts is large, so both hot pressing welding and liquid bonding can be used;

[0077] The specific operation of the hot pressing welding method is as follows: stacking parts of different shapes according to the assembly order of complex structural parts, binding and fixing the connection interface with high-temperature tape, and then hot pressing them with a mold at 200°C and 10MPa for 6 hours to obtain the assembled complex structural parts;

[0078] The specific operation of the stock solution bonding method is: according to the assembly order of complex structural parts, the dynamic cross-linked polymer prepolymer is evenly applied between parts of different shapes, the excess glue is wiped off after the dynamic cross-linked polymer prepolymer is squeezed, and then heated at 140°C for 30 minutes. After the treatment is completed, the mold is allowed to cool naturally to room temperature to obtain the assembled complex structural parts.

[0079] For complex structural parts with large size, small contact area between parts, and difficulty in stacking and fixing, such as Figure 5For complex structural parts ③ and ④, hot pressing welding is no longer applicable due to configuration limitations. Instead, the stock solution bonding method can be used. The specific operation is: according to the assembly sequence of the complex structural parts, evenly apply the dynamic cross-linking polymer prepolymer between parts of different shapes, extrude the dynamic cross-linking polymer prepolymer and wipe off the excess glue, then heat it at 140°C for 30 minutes. After the treatment is completed, wait for the mold to cool naturally to room temperature to obtain the assembled complex structural parts.

[0080] Example 2

[0081] A method for forming a complex structural part of a dynamically cross-linked polymer-based composite material comprises the following steps:

[0082] S1. Cut out simple flat plate units of different sizes from the obtained dynamic cross-linked polymer matrix composite material, such as Figure 5 As shown in step 1.

[0083] S2. preheating the simple flat plate unit at 100° C. for 10 minutes to soften the dynamically cross-linked polymer-based composite material to facilitate reshaping and shaping, thereby obtaining a softened dynamically cross-linked polymer-based composite material;

[0084] S3. Press the softened dynamically cross-linked polymer-based composite material into the arc-shaped groove of the lower mold, cover it with the upper mold, heat it to 60°C, and then slowly apply a micro-pressure of 1MPa until the upper and lower molds are completely fitted together, then increase the pressure to 15MPa and hot press for 5h; after the hot pressing treatment, wait for the upper and lower molds to cool naturally to room temperature, and parts of different shapes are obtained, realizing the reshaping from flat plates to plates of different shapes. The reshaping steps are as follows: Figure 5 As shown in step 2.

[0085] Then, the surfaces of parts of different shapes are cleaned, and the connection interfaces are scrubbed with industrial alcohol. After natural air drying or heat drying, various connection methods can be used to assemble and shape them to obtain complex structural parts.

[0086] for Figure 5 For medium-complex structural parts ① and ②, the overall size of the complex structural parts is small and the contact area between the parts is large, so both hot pressing welding and liquid bonding can be used;

[0087] The specific operation of the hot pressing welding method is as follows: stacking parts of different shapes according to the assembly order of complex structural parts, binding and fixing the connection interface with high-temperature tape, and then hot pressing with a mold at 240°C and 3MPa for 2 hours to obtain the assembled complex structural parts;

[0088] The specific operation of the stock solution bonding method is: according to the assembly order of complex structural parts, evenly apply the dynamic cross-linking polymer prepolymer between parts of different shapes, extrude the dynamic cross-linking polymer prepolymer and wipe off the excess glue, then heat it at 80°C for 120 minutes. After the treatment is completed, wait for the mold to cool naturally to room temperature to obtain the assembled complex structural parts.

[0089] For complex structural parts with large size, small contact area between parts, and difficulty in stacking and fixing, such as Figure 5 For complex structural parts ③ and ④, hot pressing welding is no longer applicable due to configuration limitations. Instead, the stock solution bonding method can be used. The specific operation is: according to the assembly sequence of the complex structural parts, evenly apply the dynamic cross-linking polymer prepolymer between parts of different shapes, extrude the dynamic cross-linking polymer prepolymer and wipe off the excess glue, then heat it at 80°C for 120 minutes. After the treatment is completed, wait for the mold to cool naturally to room temperature to obtain the assembled complex structural parts.

[0090] Example 3

[0091] A method for forming a complex structural part of a dynamically cross-linked polymer-based composite material comprises the following steps:

[0092] S1. Cut out simple flat plate units of different sizes from the obtained dynamic cross-linked polymer matrix composite material, such as Figure 5 As shown in step 1.

[0093] S2. preheating the simple flat plate unit at 140° C. for 30 minutes to soften the dynamically cross-linked polymer-based composite material to facilitate reshaping and shaping, thereby obtaining a softened dynamically cross-linked polymer-based composite material;

[0094] S3. Press the softened dynamically cross-linked polymer-based composite material into the arc-shaped groove of the lower mold, cover it with the upper mold, heat it to 240°C, and then slowly apply a micro-pressure of 1 MPa until the upper and lower molds are completely fitted together, then increase the pressure to 10 MPa and hot press for 0.5 h; after the hot pressing treatment, wait for the upper and lower molds to cool naturally to room temperature, and parts of different shapes are obtained, realizing the reshaping from flat plates to plates of different shapes. The reshaping steps are as follows: Figure 5 As shown in step 2.

[0095] Then, the surfaces of parts of different shapes are cleaned, and the connection interfaces are scrubbed with industrial alcohol. After natural air drying or heat drying, various connection methods can be used to assemble and shape them to obtain complex structural parts.

[0096] for Figure 5For medium-complex structural parts ① and ②, the overall size of the complex structural parts is small and the contact area between the parts is large, so both hot pressing welding and liquid bonding can be used;

[0097] The specific operation of the hot pressing welding method is as follows: stacking parts of different shapes according to the assembly order of complex structural parts, binding and fixing the connection interface with high-temperature tape, and then hot pressing with a mold at 60°C and 18MPa for 8 hours to obtain the assembled complex structural parts;

[0098] The specific operation of the stock solution bonding method is: according to the assembly order of complex structural parts, the dynamic cross-linked polymer prepolymer is evenly applied between parts of different shapes, the excess glue is wiped off after the dynamic cross-linked polymer prepolymer is squeezed, and then heated at 200°C for 90 minutes. After the treatment is completed, the mold is allowed to cool naturally to room temperature to obtain the assembled complex structural parts.

[0099] For complex structural parts with large size, small contact area between parts, and difficulty in stacking and fixing, such as Figure 5 For complex structural parts ③ and ④, hot pressing welding is no longer applicable due to configuration limitations. Instead, the stock solution bonding method can be used. The specific operation is: according to the assembly sequence of the complex structural parts, evenly apply the dynamic cross-linking polymer prepolymer between parts of different shapes, extrude the dynamic cross-linking polymer prepolymer and wipe off the excess glue, then heat it at 200°C for 90 minutes. After the treatment is completed, wait for the mold to cool naturally to room temperature to obtain the assembled complex structural parts.

[0100] In addition, parts of different shapes can also be connected and assembled using traditional heterogeneous bonding methods or mechanical connection methods, such as Figure 5 The middle structural member ④ can also be assembled and formed using conventional bolt connections, and the structural member ③ can also be formed by conventional heterogeneous bonding.

[0101] The specific operation of the mechanical connection method is: fit the connection interfaces of parts of different shapes together, then punch holes, and then fix them with bolts.

[0102] The specific operation of the heterogeneous bonding method is: apply adhesive to the connection interface of parts of different shapes, squeeze the adhesive and wipe off the excess glue, then fit the connection interface of the two parts together, and then heat at 80°C for 30 minutes.

[0103] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for forming complex structural parts of dynamically cross-linked polymer-based composite materials, characterized in that: The steps include: After laying the dynamically cross-linked polymer pre-impregnated fiber cloth layer by layer and curing it, a flat plate-shaped dynamically cross-linked polymer-based composite material is obtained; Among them, the dynamically cross-linked polymer pre-impregnated fiber cloth is a fiber cloth in which the dynamically cross-linked polymer prepolymer is loaded; The dynamically cross-linked polymer-based composite material is used as a simple flat plate unit, and the dynamically cross-linked polymer-based composite material is placed in a mold. It is reshaped and processed for 0.5-6 hours at 60-240°C and 1-15MPa. During the reshaping process, the dynamic covalent bonds inside the dynamically cross-linked polymer material of the dynamically cross-linked polymer-based composite material are activated to undergo exchange reactions, thereby changing the topological structure of the internal network of the dynamically cross-linked polymer material, releasing the stress caused by deformation, achieving permanent deformation, and completely reshaping the shape to produce parts of different shapes. Components of different shapes and / or flat-plate dynamically cross-linked polymer-based composite materials are assembled according to complex structural parts. Hot pressing welding or stock solution bonding is used at the connection interface to activate the dynamic covalent bonds between components of different shapes to cause exchange reactions, forming an interface with the synergy of covalent bonds, intermolecular forces and physical entanglement to obtain complex structural parts.

2. The method for forming complex structural parts of a dynamically cross-linked polymer-based composite material according to claim 1, characterized in that: The connection interface is formed by laminating together a number of dynamically cross-linked polymer-based composite materials of components of different shapes.

3. The method for forming a complex structural part of a dynamically cross-linked polymer-based composite material according to claim 2, characterized in that: The operation of the hot pressing welding method is: hot pressing the connection interface at 60-240°C and 3-18MPa for 2-8h.

4. The method for forming a complex structural part of a dynamically cross-linked polymer-based composite material according to claim 2, characterized in that: The operation of the stock solution bonding method is: apply the dynamic cross-linking polymer prepolymer to the connection interface between parts of different shapes, and heat the connection interface at 80-200℃ for 5-120min.

5. The method for forming a complex structural part of a dynamically cross-linked polymer-based composite material according to claim 2, characterized in that: Components of different shapes can also be connected at the connection interface using traditional heterogeneous bonding methods or mechanical connection methods.

6. The method for forming complex structural parts of a dynamically cross-linked polymer-based composite material according to claim 1, characterized in that: The dynamically cross-linked polymer-based composite material is placed in front of the mold, and the dynamically cross-linked polymer-based composite material is heated and softened.

7. The method for forming a complex structural part of a dynamically cross-linked polymer-based composite material according to claim 6, characterized in that: The operation of the heating and softening treatment is: heating and softening at 100-160°C for 10-60 minutes.

8. The method for forming complex structural parts of a dynamically cross-linked polymer-based composite material according to claim 1, characterized in that: The dynamic covalent bond of the dynamic cross-linked high molecular prepolymer is selected from ester bond, boron-oxygen bond, imine bond, disulfide bond, borate ester bond, thioester bond, thioether bond, amide bond or urea bond.

9. The method for forming a complex structural part of a dynamically cross-linked polymer-based composite material according to claim 1, characterized in that: Reinforcement materials can also be incorporated into the dynamically cross-linked polymer prepolymer. The reinforcement materials include fiber materials and particulate materials. The fiber materials are selected from carbon fibers, glass fibers, aramid fibers, high-strength polyethylene fibers, ceramic fibers, metal fibers, carbon nanotube fibers, boron fibers, liquid crystal polymer fibers or natural fibers. The particulate materials are selected from carbon nanotubes, carbon black, graphite particles, graphene, cellulose nanoparticles, rubber particles, aluminum hydroxide particles, magnesium hydroxide particles, silver particles, nickel particles, silica, ceramic particles, glass particles, carbonate particles or silicate clay.

10. The method for forming complex structural parts of a dynamically cross-linked polymer-based composite material according to claim 1, characterized in that: The dynamically cross-linked high molecular prepolymer is loaded on the fiber cloth by spraying molding, hand lay-up molding, vacuum bag molding, autoclave molding, compression molding, resin transfer molding, vacuum assisted resin transfer molding, co-curing molding, pultrusion molding or injection molding.

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