Heterogeneous connection anti-fatigue structural adhesive prepreg and preparation method thereof

Abstract

The invention discloses a dissimilar connection anti-fatigue structural adhesive prepreg and a preparation method thereof, belongs to the field of resin-based composite materials, and is suitable for lightweight connection and anti-fatigue enhancement of dissimilar materials such as resin-based composite materials and honeycomb materials in high-end equipment such as aerospace and traffic transportation. Epoxy resin is used as a basis, a specific type of toughened resin and a curing agent are matched to form a three-component system, the bearing function of a traditional prepreg and the bonding function of an adhesive film are integrated, and a traditional two-step method mode is replaced. Epoxy resin and toughened resin are firstly subjected to vacuum drying treatment, then full mixing and cooling are achieved through segmented stirring and curing, then a curing agent is added in batches, precise homogenization is conducted, finally, a one-step curing process is adopted, prepreg and dissimilar materials are directly attached and cured, and independent adhesive film related procedures are omitted. While weight reduction is achieved, the anti-fatigue performance and the interface bonding strength of connection of the dissimilar materials are guaranteed, the production cost and the bad piece rate are reduced, the production process is simplified, and the requirements for lightweight connection and anti-fatigue enhancement of the dissimilar materials in high-end equipment such as aerospace equipment and traffic transportation equipment are met.

Description

Technical Field

[0001] This invention belongs to the field of resin-based composite material technology, specifically relating to a non-metallic bonding anti-fatigue structural adhesive prepreg and its preparation method, which is particularly suitable for lightweight bonding and fatigue-resistant reinforcement of resin-based composite materials and non-metallic materials (such as honeycomb materials) in high-end equipment such as aerospace, transportation, and shipbuilding. Background Technology

[0002] Resin-based composite materials are widely used in aerospace, transportation, and other fields due to their excellent strength and designability. However, in practical engineering applications, these materials still face significant technical bottlenecks in areas such as fatigue resistance, dissimilar material bonding processes, and production cost control. These challenges severely restrict the further promotion and application of resin-based composite materials in high-end equipment.

[0003] Resin-based composites inherently suffer from fatigue resistance, primarily due to insufficient interfacial bonding strength between the fiber and matrix, and the resulting microscopic defect formation mechanism. During composite material preparation, issues such as resin viscosity, wettability, and mismatched process parameters can easily lead to the formation of micropores and localized defects at the fiber / matrix interface. These microscopic defects gradually expand under cyclic loading or environmental stress, ultimately resulting in a significant decline in material properties. The performance degradation is even more pronounced when composites are exposed to environments containing water vapor and experiencing large temperature fluctuations. Moisture penetration plasticizes the resin matrix, lowering its glass transition temperature and inducing internal stresses that cause damage. Furthermore, deformation under frequent external forces accelerates delamination in composite materials.

[0004] In aerospace structures, the combination of honeycomb materials and fiber-reinforced composites is a common lightweight design strategy. However, due to the limited adhesive properties of the resin matrix itself, structural adhesives are required at the junction of the two materials to achieve a reliable connection. This process significantly increases the weight of the final product, posing a severe limitation for weight-sensitive fields, especially aerospace applications. Furthermore, while structural adhesives can create products that meet structural strength requirements without the use of mechanical fasteners or welding and are well-suited for various substrates, including plastics, metals, and composites, their weight accumulation effect cannot be ignored. In large aerospace structures such as wing skin-honeycomb core structures, the amount of adhesive used is considerable, and the resulting weight gain directly impacts the aircraft's fuel economy and load capacity.

[0005] Besides the added weight, relying solely on resin matrices for joining dissimilar materials also poses reliability risks. Resin-based composites and cellular materials (such as Nomex or aluminum cellular) differ significantly in their coefficients of thermal expansion, stiffness, and toughness. Under thermal cycling or external forces, stress concentration easily occurs at the interface, further exacerbating the risk of interface failure. Especially at high temperatures, the softening of the resin matrix weakens adhesion and accelerates the development of damage mechanisms. Introducing structural adhesives for joining dissimilar materials not only increases weight but also significantly increases the complexity of the production process and overall cost. Each new material added to the production process requires the introduction of corresponding new processes, including surface treatment, adhesive coating, and curing cycle control, greatly increasing process complexity and directly leading to increased production costs and decreased yield. There are compatibility issues between different material systems, including compatibility in terms of thermal expansion coefficients, chemical compatibility, and curing shrinkage rates. The more types of materials involved, the more pronounced these compatibility issues become, ultimately leading to lower yields and further increasing overall costs. Furthermore, verifying the quality consistency and reliability of multi-material systems also faces significant challenges. The introduction of each new material and process requires comprehensive performance verification and process qualification, which consumes significant time and resources. This process is particularly rigorous and time-consuming in fields with extremely high safety requirements, such as aerospace, further increasing overall costs and technological risks.

[0006] The existence of these technical bottlenecks makes it difficult to achieve the original intention of lightweight design when joining dissimilar materials (such as resin-based composites and honeycomb materials). Furthermore, problems such as interface stress concentration and weakened adhesion at high temperatures lead to a significant decline in connection reliability. At the same time, the problems of increased process complexity, high production costs and low yield further hinder its large-scale application in high-end equipment fields such as aerospace and shipbuilding. Ultimately, the high stability and low cost of engineering implementation of dissimilar material joining have been greatly limited, and it is urgent to solve them through technological innovation and material optimization. Summary of the Invention

[0007] This invention aims to replace the traditional two-step process of "prepreg + adhesive film" to achieve high-performance and low-cost bonding of composite materials with dissimilar materials (such as honeycomb), thus solving one of the technical problems in related technologies to a certain extent.

[0008] This invention, through the design of a three-component system and its precise mass ratio, improves toughness while maintaining heat resistance and strength, fundamentally solving the problems of weak interfacial bonding and easy delamination in existing technologies. A precisely controlled chemical reaction process ensures good prepreg coverage and wettability, and the elimination of a separate adhesive film layer significantly improves weight reduction.

[0009] The purpose of this invention is to provide a non-ferrous bonding anti-fatigue structural adhesive prepreg, characterized in that it comprises epoxy resin, toughening resin and curing agent; the mass ratio is 100:120-180:15-30.

[0010] Among them, the toughening resin is one of the following: nitrile rubber toughening epoxy resin, p-aminophenol triglycidyl epoxy resin, and PES modified epoxy resin. The curing agent is one of dicyandiamide, 2-methylimidazole-salicylic acid complex, 2-methylimidazole or 2-ethyl-4-methylimidazole.

[0011] The present invention also aims to provide a method for preparing a fatigue-resistant structural adhesive prepreg for heterogeneous bonding, characterized by comprising: Step 1: Vacuum dry the epoxy resin and toughening resin at 80-100℃ for 2-3 hours, and then seal and mix them at 110-220℃ with a temperature fluctuation range of less than ±5℃ for 48 hours under normal pressure.

[0012] Step 2: Cool the mixture to a final temperature of 80-120℃, hold it at that temperature, and then add the curing agent.

[0013] In step 1, the stirring speed is reduced to 50-100 r / min for the first 24 hours and then reduced to 200-300 r / min for the next 24 hours.

[0014] Step 2: The cooling process adopts a uniform cooling rate of 5-10℃ / min.

[0015] Add the curing agent in 2-3 batches. After each addition, stir at 300 rpm for 10-15 minutes to quickly disperse the agent, and then stir at 150 rpm for 30 minutes to slowly homogenize it.

[0016] Step 3 involves a one-step curing process, where the prepreg is directly bonded and cured with the dissimilar material at a curing temperature of 120-180℃.

[0017] Furthermore, the composition includes epoxy resin, toughening resin, and curing agent; the mass ratio is 100:120-180:15-30.

[0018] Furthermore, the curing agent is one of dicyandiamide, 2-methylimidazole-salicylic acid complex, 2-methylimidazole, or 2-ethyl-4-methylimidazole.

[0019] Furthermore, the particle size of the toughening resin after dispersion in step 2 is less than 100 nm.

[0020] Furthermore, the viscosity of the prepreg obtained in step 2 is less than 200,000 centipoise.

[0021] Furthermore, the bonding pressure in step 3 is 0.3-0.5 MPa.

[0022] Epoxy resin forms the basic framework of the system. The epoxy groups in the epoxy resin molecular chain can crosslink with the curing agent to form a three-dimensional network structure. This structure has excellent rigidity and thermal stability, which is the core source of the "load-bearing function" of the prepreg, meeting the strength requirements of high-end scenarios such as aerospace (180°C high-temperature conditions) and shipbuilding (humid and hot environments). Uncured epoxy resin has a certain degree of fluidity, which can wet the surface of dissimilar materials (such as honeycomb materials). It combines with dissimilar materials through interfacial intermolecular forces (van der Waals forces, hydrogen bonds), making it possible to "eliminate the need for a separate adhesive film"—in traditional solutions, the prepreg is only responsible for load bearing, and an additional adhesive film is required for bonding. However, this invention achieves preliminary functional integration through the "load bearing + bonding" dual properties of epoxy resin. After crosslinking, the epoxy resin molecular chain is highly rigid and brittle, and is prone to cracking under cyclic loading. Moreover, the interfacial wettability is easily affected by micropores—this is the core reason why toughening resin needs to be introduced.

[0023] The nitrile rubber molecular chain contains flexible butadiene segments and active carboxyl groups, which can be dispersed into nanoscale particles of <100nm during the mixing process. The PES (polyethersulfone) molecular chain has both rigid aromatic rings and flexible ether bonds, which can form a "semi-interpenetrating network structure" with epoxy resin, which retains rigidity (ensuring strength) and improves toughness through flexible ether bonds. The p-aminophenol triglycidyl epoxy resin contains multiple epoxy groups and amino groups, which can react with epoxy resin and honeycomb materials (such as the amide groups of surface-activated Nomex honeycomb) to form "chemical bridges", directly solving the problem of "large difference in thermal expansion coefficient and interfacial stress concentration" between resin-based composite materials and honeycomb materials.

[0024] At 80-100℃ (the temperature at which the resin softens but is not yet cured), negative pressure is used to extract moisture, unreacted monomers, and other volatiles from the epoxy and toughening resins, preventing the formation of micropores during subsequent mixing and curing. This step directly improves the interfacial bonding strength. It also prevents moisture and low-molecular-weight volatiles from forming bubbles during curing, which can become the starting point for crack propagation under cyclic loading.

[0025] High-speed stirring (200-300 rpm) breaks up the agglomerates of the toughening resin, dispersing it into nanoparticles <100 nm. Uneven dispersion will cause the toughening agent to form large agglomerates, which become stress concentration points, leading to delamination. Low-speed curing (50-100 rpm) allows the epoxy resin and toughening resin to undergo a "pre-reaction"—for example, the carboxyl and epoxy groups of nitrile rubber initially react to form a "graft copolymer," improving the compatibility of the two components and preventing "phase separation" (i.e., resin and toughening agent delamination) during subsequent curing. Low-speed stirring also reduces shear heat within the system, preventing excessively high local temperatures that could cause premature resin curing.

[0026] Strict temperature control (±5℃): Excessive temperature (e.g., above 220℃) will cause resin molecular chain degradation and decreased strength; excessively low temperature (e.g., <110℃) will result in high resin viscosity, high stirring resistance, and uneven dispersion. A fluctuation range of ±5℃ can ensure a stable mixing process.

[0027] Uniform cooling and phased addition of the curing agent can avoid internal stress and ensure uniform cross-linking. When cooling the resin system from 110-220℃, if the cooling is too rapid (e.g., >10℃ / min), the large temperature difference between the inside and outside of the system will generate "thermal shrinkage stress"—this internal stress will remain after curing, causing interfacial gaps when the prepreg and honeycomb are bonded, reducing peel strength. Allowing the system temperature to decrease slowly and uniformly gives the molecular chains enough time to adjust their conformation, avoiding the accumulation of internal stress; the goal of cooling to 80-120℃ is to control the resin viscosity—at this temperature, the resin viscosity is moderate (final prepreg viscosity <200,000 centipoise), which ensures uniform dispersion of the subsequent curing agent without resin loss due to excessively low viscosity.

[0028] Hardeners (such as dicyandiamide) are in powder form and tend to agglomerate into "hardener particles" when added all at once. These particles can cause excessively rapid local cross-linking, forming "hard spots" that become crack initiation points under stress. Adding them in 2-3 batches with high-speed stirring can break the hardener particles into micron-sized particles, ensuring that each hardener particle comes into contact with the resin. After high-speed stirring, the hardener concentration is high in some areas, requiring low-speed stirring to allow it to diffuse evenly within the resin system. High-speed stirring alone will result in uneven distribution of the hardener, with some areas having high cross-linking density (brittle) and others having low cross-linking density (soft), leading to large fluctuations in strength. Low-speed stirring at 150 r / min can achieve uniform diffusion.

[0029] Traditional methods employ a "prepreg curing alone (first step) + adhesive film bonding curing (second step)" approach, which presents two core problems: ① the additional adhesive film increases weight; ② the prepreg-adhesive film-honeycomb structure forms two interfaces, prone to stress concentration. One-step curing directly bonds the prepreg to the dissimilar material (honeycomb), simultaneously curing at 120-180℃ (depending on the type of curing agent) and 0.3-0.5MPa pressure. During curing, the resin in the prepreg both completes its own cross-linking (achieving load-bearing capacity) and wets and bonds to the honeycomb surface (achieving adhesion), essentially "integrating the functions of the prepreg and the adhesive film into one," fundamentally resolving the contradiction between "weight reduction" and "weak interface." Eliminating the separate adhesive film layer reduces weight per unit area. One-step curing eliminates the "prepreg-film" interface, leaving only the "prepreg-honeycomb" interface. Furthermore, the resin and honeycomb are chemically bonded, and the interface stress concentration significantly reduces pressure, allowing air to escape between the prepreg and the honeycomb. This ensures that the resin fully wets the honeycomb surface and avoids interface voids. Excessive pressure can lead to excessive resin loss and reduced strength, while insufficient pressure prevents air from escaping, resulting in pores. Beneficial effects

[0030] 1. The structural adhesive prepreg of this invention achieves a 50% weight reduction in certain areas compared to the traditional "adhesive film + prepreg" solution through "functional integration" design. It can balance load-bearing and bonding functions without the need for an additional structural adhesive film, and the weight reduction does not sacrifice performance. The interlaminar shear strength is ≥40MPa, the peel strength is ≥6N / mm or the bonded substrate is destroyed before the adhesive joint, and the flowability at the coating temperature is <200,000 centipoise. It has core value in aerospace (weight reduction and energy saving of wing skin), transportation (range improvement of new energy vehicles), and shipbuilding (navigation stability optimization), effectively breaking through the technical bottleneck of weight-sensitive equipment.

[0031] 2. The modified carbon fiber composite material exhibits outstanding performance: at 70% of its ultimate tensile strength, its fatigue resistance is 10 times that of conventional epoxy resin-based products. Conventional materials fracture after 300,000 bending vibrations, while the product of this invention remains undelaminated after 3.2 million cycles. This breakthrough stems from the selection of a special toughening agent (AFG-95 toughening resin produced by Tianjin Honeycomb), and the optimization of processes such as vacuum drying and segmented stirring curing. This can significantly extend the service life of high-frequency load components such as aircraft wings and automobile chassis, and reduce maintenance costs and failure risks.

[0032] 3. In terms of cost control, the cost reduction is directly proportional to the amount of composite material adhesive film used because one layer of adhesive film is eliminated: it reduces the cost of adhesive film procurement and storage, and eliminates adhesive film processing and coating processes, thereby reducing equipment investment and labor costs; at the same time, the single prepreg system reduces the risk of multiple material matching, and the scrap rate is reduced from the traditional 8%-12% to below 2%-3%.

[0033] The synergistic effect of weight reduction, fatigue resistance, and cost reduction not only improves the economic efficiency of equipment throughout its entire life cycle, but also promotes the large-scale application of resin-based composite materials in the field of high-end equipment. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] With regard to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagents. The toughening resin was purchased from Tianjin Honeycomb, AFG-95 type.

[0040] Example 1: Intermediate ratio formulation (cured at 180℃, for general applications) Mixing process: 100 parts by weight of bisphenol A type epoxy resin (E-51) and 150 parts by weight of toughening resin (nitrile rubber toughening epoxy resin) are first vacuum dried at 80-100℃ for 2-3 hours, and then sealed and mixed at 180℃ and normal pressure for 48 hours; the first 24 hours are stirred at high speed of 250r / min, and the last 24 hours are cured at low speed of 80r / min, with the temperature fluctuating by ±3℃ throughout the process.

[0041] Cooling and adding curing agent: Cool down to 100℃ at a uniform rate of 8℃ / min, and add 20 parts by weight of dicyandiamide in two batches (10 parts each time); after each addition, stir at 300r / min for 12min to quickly disperse, and then stir at 150r / min for 30min to slowly homogenize.

[0042] Curing process: The "one-time curing" mode is adopted, with a bonding pressure of 0.4MPa. The prepreg and the honeycomb core are cured simultaneously, without the need for secondary processing.

[0043] Example 2: Low toughening agent ratio formulation (cured at 120℃, low temperature sensitive scene) Mixing process: 100 parts by weight of bisphenol F type epoxy resin (E-54) and 150 parts by weight of toughening resin (p-aminophenol triglycidyl epoxy resin) are first vacuum dried at 80-100℃ for 2-3 hours, and then sealed and mixed at 150℃ and normal pressure for 48 hours; the first 24 hours are stirred at high speed of 200r / min, and the last 24 hours are matured at low speed of 50r / min, with temperature fluctuations of ±4℃ throughout the process.

[0044] Cooling and adding curing agent: Cool to 80℃ at a uniform rate of 5℃ / min, and add 15 parts by weight of 2-methylimidazole (5 parts each time) in 3 portions; after each addition, stir at 300r / min for 10min to quickly disperse, and then stir at 150r / min for 30min to slowly homogenize.

[0045] Curing process: It adopts the "one-time curing" mode, with a bonding pressure of 0.3MPa and a curing temperature of 120℃. It is suitable for low-temperature sensitive substrates and requires no secondary processing.

[0046] Example 3: High toughening agent ratio formulation (cured at 180℃, high impact resistance scenario) Mixing process: 100 parts by weight of phenolic epoxy resin (F-44) and 180 parts by weight of toughening resin (PES modified epoxy resin) are first vacuum dried at 80-100℃ for 2-3 hours, and then sealed and mixed at 200℃ and normal pressure for 48 hours; the mixture is stirred at high speed of 300r / min for the first 24 hours and at low speed of 100r / min for the next 24 hours, with the temperature fluctuating by ±5℃ throughout the process.

[0047] Cooling and adding curing agent: Cool down to 120℃ at a uniform rate of 10℃ / min, and add 30 parts by weight of 2-ethyl-4-methylimidazole (15 parts each time) in two batches; after each addition, stir at 300r / min for 15min to quickly disperse, and then stir at 150r / min for 30min to slowly homogenize.

[0048] Curing process: It adopts a "one-time curing" mode, with a bonding pressure of 0.5MPa, which is suitable for high load components and requires no secondary processing.

[0049] Comparative Example 1: Traditional two-step method of "conventional prepreg + independent film" Material preparation: Select Huibai New Materials WP-R1312 conventional epoxy resin prepreg (resin matrix + fiber only, no toughening design) and commercially available conventional epoxy resin film (E-51 + dicyandiamide system); the prepreg substrate needs to be sanded and cleaned before use, and the film needs to be stored at low temperature (5-10℃).

[0050] Step 1 Curing: Cur the conventional prepreg separately at 180℃ for 2 hours.

[0051] The second step is curing: the cured prepreg is bonded to the honeycomb core, with an independent adhesive film sandwiched in between, and the secondary curing conditions are 180℃ / 1.5h.

[0052] Comparative Example 2: Pure Conventional Prepreg Material preparation: Only Huibai New Materials WP-R1312 conventional epoxy resin prepreg (without toughening agent or additional adhesive film) is used, relying on the adhesive force of the resin matrix itself to achieve heterogeneous bonding.

[0053] Curing process: The "one-step curing" mode is adopted (the prepreg and the honeycomb core are directly bonded and cured under curing conditions of 180℃ / 2h), without surface treatment or additional bonding reinforcement steps.

[0054] The testing method is as follows: Interlaminar shear strength: Tested using the short beam shear method according to ASTM D2344 standard.

[0055] Peel strength: Both the 180℃ and 120℃ cured versions were tested according to the industry-standard peel test method, and the maximum force value at the material interface was converted.

[0056] Flowability at coating temperature: The fluid viscosity (unit: 10,000 centipoise) was measured using a rotational viscometer at the corresponding curing temperatures (180℃ / 120℃).

[0057] Fatigue resistance: Under 70% ultimate tensile strength, bending vibration test was performed, and the number of vibrations before the material delaminated / fractured was recorded.

[0058] Local weight reduction rate: The weight reduction percentage is calculated by comparing the unit area weight of the prepreg of this invention with that of "traditional prepreg + independent film".

[0059] Cost reduction rate: Calculate the cost of "adhesive film procurement + adhesive film storage + secondary curing process" and compare the cost savings percentage of the solution of this invention.

[0060] Shear strength retention after damp heat aging: After 500 hours of damp heat aging treatment (temperature 40℃, humidity 95%), the interlaminar shear strength was tested, and the retention rate was calculated (strength after aging / initial strength × 100%).

[0061] Impact toughness (carbon fiber sheet): The impact absorbed energy of the carbon fiber sheet was measured using the simply supported beam impact test method (unit: KJ / ㎡).

[0062] Self-adhesiveness / re-adhesion: At room temperature, apply the prepreg to the bottom of the object to be bonded and observe whether it falls off; record the maximum number of times it can be repeatedly peeled off and re-attached.

[0063] Curing process steps / scrap rate: Count the number of curing operations; record the proportion of defective products in batch production (scrap rate = number of defective parts / total number of parts × 100%).

[0064] The test results are shown in Table 1.

[0065]

[0066] The three embodiments of the present invention (Examples 1-3) are based on epoxy resin, combined with specific types of toughening agents (nitrile rubber toughened epoxy resin, p-aminophenol triglycidyl epoxy resin or PES modified epoxy resin, all of which are Tianjin Honeycomb AFG-95 model) and curing agents (dicyandiamide, 2-methylimidazole, etc.), and constructed into a three-component system at a precise mass ratio of 100:120-180:15-30. During the preparation process, the resin micropores are removed by vacuum drying at 80-100℃ for 2-3 hours, and then sealed and mixed at 110-220℃ under normal pressure for 48 hours (high-speed stirring at 200-300r / min for the first 24 hours and low-speed curing at 50-100r / min for the last 24 hours). Finally, the temperature is uniformly reduced to 80-120℃ at 5-10℃ / min and the curing agent is added in 2-3 times. Finally, the preparation is completed by one-step curing at 120-180℃. In contrast, Comparative Example 1 uses a traditional two-step method of "conventional prepreg + independent adhesive film," which requires additional procurement and low-temperature storage of the adhesive film, as well as sanding and cleaning the surface of the prepreg and two curing processes at 180°C (first curing the prepreg separately, then sandwiching the adhesive film and honeycomb core for a second curing), resulting in a 60% increase in cost and significant weight gain. Comparative Example 2 uses only conventional prepreg without toughening design, relying on the adhesive force of the resin itself for bonding. Although it is a one-step curing process, there are no reinforcement measures, ultimately resulting in delamination after 250,000 vibrations and a scrap rate as high as 15%. In contrast, Examples 1-3, with their optimized formulations and processes, achieve a 49%-51% local weight reduction, an interlaminar shear strength of 41-48 MPa, a peel strength of 4.2-5.2 N / mm, and no delamination after 3.2-3.8 million bending vibrations at 70% ultimate tensile strength. The cost is reduced by 45%-52%, and the scrap rate is only 1.8%-2.5%, with all core performance characteristics surpassing the two comparative examples.

[0067] This solution integrates the load-bearing function of traditional prepregs with the adhesive function of adhesive films into a single system through a "functional integration" design. This fundamentally solves the inherent defects of traditional dissimilar bonding technologies, such as weak interfacial bonding and easy delamination, while avoiding the increased weight, higher costs, and reliability risks caused by additional adhesive films and multiple process steps. Traditional dissimilar bonding solutions require the use of additional adhesive films for bonding. This solution, through functional integration, combines the load-bearing function of traditional prepregs with the adhesive function of adhesive films into a single prepreg system. This solution uses only a "single prepreg system" to bond dissimilar materials (such as honeycomb), reducing the material types from "prepreg + adhesive film + dissimilar material" to "prepreg + dissimilar material," directly avoiding the compatibility problem between "prepreg and adhesive film." Simultaneously, the toughening resin in the prepreg (such as p-aminophenol triglycidyl epoxy resin) can form "chemical bridges" with the surface groups of the honeycomb material, further optimizing the interfacial compatibility between "prepreg and honeycomb." By "eliminating the adhesive film and reducing the types of materials", the multiple matching problems of "prepreg and adhesive film" in the traditional solution are eliminated from the root. At the same time, the process is simplified, and the yield rate is significantly improved from 8%-15% in the traditional solution to 1.8%-2.5% in this application.

[0068] In terms of environmental resistance, after 500 hours of damp heat aging (40℃, 95% humidity), the shear strength retention rate of the embodiment still reached 62%-70%, which is much higher than 45% of Comparative Example 1 and 38% of Comparative Example 2. In terms of process adaptability, the embodiment has good self-adhesion at room temperature and can be repeatedly laid 3-5 times. The one-step curing process greatly reduces the complexity of operation. It not only meets the stringent requirements of high-end equipment such as weight reduction and energy saving of wing skin in the aerospace field, range improvement of new energy vehicles in the transportation field, and navigation stability optimization in the ship field, but also provides a practical and feasible technical path for the large-scale and low-cost engineering connection of resin-based composite materials and dissimilar materials such as honeycomb materials by simplifying the production process and reducing the scrap rate, thus promoting the further application of resin-based composite materials in the field of high-end equipment.

[0069] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0070] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0071] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A hetero-connection fatigue resistant structural adhesive prepreg, characterized by: The epoxy resin, the toughening resin and the curing agent; the mass ratio is 100:120-180:15-30.

2. The prepreg of claim 1, wherein the prepreg is characterized by: The toughening resin is one of carboxyl-terminated butyl nitrile rubber toughened epoxy resin, p-aminophenol triglycidyl epoxy resin and PES modified epoxy resin.

3. The prepreg of claim 1, wherein the prepreg is characterized by: The curing agent is one of dicyandiamide, 2-methyl imidazole-salicylic acid complex, 2-methyl imidazole and 2-ethyl-4-methyl imidazole.

4. A method for producing a prepreg of a hetero-connection fatigue resistant structural adhesive, characterized by: The method comprises the following steps: Step 1, vacuum drying the epoxy resin and the toughening resin at 80-100℃ for 2-3 hours, and then mixing the two at 110-220℃ with a temperature fluctuation range less than ±5℃ under normal pressure for 48 hours; in the first 24 hours, high-speed stirring is performed at 200-300r / min, and in the last 24 hours, low-speed curing is performed at 50-100r / min; Step 2, cooling the mixture, the final cooling temperature is 80-120℃, and then adding the curing agent; the cooling process is performed at a uniform speed of 5-10℃ / min; the curing agent is added in 2-3 times, and after each addition, fast dispersion is performed at 300r / min for 10-15 minutes, and then slow homogenization is performed at 150r / min for 30 minutes; Step 3, one-step curing is performed by directly bonding the pre-preg with a dissimilar material and curing, and the curing temperature is 120-180℃.

5. The method for preparing a dissimilar bonding anti-fatigue structural adhesive prepreg according to claim 4, characterized in that: The toughening resin is one of carboxyl-terminated butyl nitrile rubber toughened epoxy resin, p-aminophenol triglycidyl epoxy resin and PES modified epoxy resin.

6. The method of claim 4, wherein the method further comprises the step of: 6.

1. mixing the curable resin with the reinforcing material to form the prepreg. The curing agent is one of dicyandiamide, 2-methyl imidazole-salicylic acid complex, 2-methyl imidazole and 2-ethyl-4-methyl imidazole.

7. The method for preparing a dissimilar bonding anti-fatigue structural adhesive prepreg according to claim 4, characterized in that: The particle size of the toughening resin after dispersion in step 2 is less than 100nm.

8. The method for preparing a dissimilar bonding anti-fatigue structural adhesive prepreg according to claim 4, characterized in that: The viscosity of the pre-preg obtained in step 2 is less than 200,000 centipoises.

9. The method of claim 4, wherein the method further comprises the step of: 9.

1. mixing the curable resin with the reinforcing material to form the prepreg. The bonding pressure in step 3 is 0.3-0.5MPa.

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