A low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces and a preparation method thereof

Abstract

The present invention relates to the field of adhesive films, and particularly to a low-dielectric and high-toughness adhesive film for heterogeneous interfaces and a preparation method thereof, which includes a matrix phase and a fiber felt. The fiber felt is impregnated in the matrix phase to form an adhesive film; the matrix phase includes a thermosetting resin system; the fiber felt is prepared by using short fibers as carriers to load nano-SiO2 to obtain nano-SiO2 grafted short fibers, and then making a fiber felt; the short fibers are organic synthetic fibers or inorganic fibers with a low dielectric constant. The adhesive film of the invention can exhibit strong adhesive strength at the heterogeneous interface, improve the overall critical energy release rate of the material, effectively inhibit the interlaminar delamination failure, through-thickness damage and non-through-thickness damage caused by out-of-plane impact to the composite material, and at the same time has high wave-transmitting performance. It can be applied to structures with high requirements for anti-impact and wave-transmitting performance, such as meteorological radomes, vehicle-mounted antenna covers, aircraft shells, etc.

Description

Technical Field

[0001] The invention relates to the field of adhesive films, and in particular to a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces and a preparation method thereof. Background Art

[0002] Composite materials are important protective materials for radar antenna covers. While providing an electromagnetic window for the antenna system, they also protect the antenna system from damage from the harsh natural environment and high-speed impacts from unknown objects outside the surface. With the increasing complexity of the battlefield environment, more stringent protection performance requirements are placed on it. Not only must it provide excellent wave transmission performance in complex and changeable battlefield environments and maintain the overall mechanical properties of the structure, but it must also minimize weight to provide better maneuverability. Fiber-reinforced resin-based composite materials such as ultra-high molecular weight polyethylene (UHMWPE) fibers, poly(p-phenylene benzobisoxazole) fibers (PBO) fibers, and aramid fibers are a new generation of protective materials. They have been a hot topic in this field in recent years and have also been widely used, such as the Canadian Challenger aircraft radar cover. Fiber-reinforced resin-based composite materials have excellent impact resistance and protective properties, and the density is mostly 3 g / cm 3 Compared with traditional metals, it has promoted the development of lightweight and high mobility of weapons and equipment. However, in practical applications, fiber-reinforced composite materials are prone to delamination and large back protrusion under impact. Although they can effectively protect against penetrating damage, they are prone to material structural failure caused by non-penetrating damage, and it is difficult to provide the necessary stiffness for structural materials. Therefore, the interlayer phase is often studied to achieve the purpose.

[0003] The current design of protective materials mainly focuses on the method of energy dissipation. Under the premise of providing the necessary stiffness for the structure, anti-penetration and anti-penetration are the main improvement points. However, for protective materials designed with a combination of multiple heterogeneous materials, the forces and damage caused by the combination of fiber shearing, fiber stretching and fiber compression during the initial impact stage, erosion stage and fracture stage during the impact process are diverse, and the coupling effect of the shock wave diffusion layer by layer is significant. A single energy dissipation method is difficult to exert specific energy absorption characteristics under different damage forms, which makes it impossible to enhance the interface between layers in different regions through a single energy dissipation method. In addition, protective materials also face challenges such as insufficient protection against multiple impacts and a significant decrease in bearing capacity after impact.

[0004] Due to the need to resist penetration damage, composite materials need to have a large in-plane tensile deformation under the action of out-of-plane loads, so as to give full play to the axial tensile properties of the fiber; for non-penetrating damage, it is hoped that the composite material has a high in-plane stiffness to reduce the depression deformation. Traditional research based on the energy dissipation mechanism believes that anti-penetration performance and anti-depression performance are a pair of contradictory characteristics. For composite materials with special application environments, such as those used in wave-transmitting radar antenna covers, low dielectric properties are also an important issue that cannot be avoided. This requires that while reinforcing the composite material, materials and structures with high dielectric parameters cannot be introduced. The key point of the above problem lies in the interface, so seeking a heterogeneous interface bonding method with excellent bonding strength, fracture toughness, low plastic deformation, and low dielectric and high wave transmission characteristics is a key problem that needs to be solved in the current application of composite materials in radar antenna covers. Summary of the invention

[0005] The present invention provides a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces and a preparation method thereof. The adhesive film has the performance characteristics of low dielectric and high toughness; the preparation method has the characteristics of simple preparation process and simple use method; compared with traditional single-component adhesives, the composite structure protective material using the adhesive film has the advantages of low deformation, high impact resistance, low dielectric, high wave transmittance and the like.

[0006] To achieve the above object, the present invention provides the following technical solution: a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces, comprising a matrix phase and a fiber mat, wherein the fiber mat is impregnated in the matrix phase to form an adhesive film; the matrix phase comprises a thermosetting resin system; the fiber mat is a short fiber used as a carrier to load nano-SiO 2 Prepared nano-SiO 2 Short fibers are grafted and made into fiber felt; the short fibers are organic synthetic fibers or inorganic fibers with low dielectric constant.

[0007] In the present invention, the thermosetting resin system as the matrix phase can bond the reinforcement into a whole and maintain a certain shape, transfer interlayer stress, and protect the reinforcement from external erosion and damage; the short fiber as the nano-SiO 2 The carrier plays a role in carrying nano-SiO 2 And make nano-SiO 2 The fiber felt composed of short fibers can enhance the interlayer bonding strength and improve the overall mechanical properties of the composite material. 2 As the main low dielectric filler, it limits the molecular chain activity, hinders the carrier transmission, and reduces the dielectric value; short fibers and nano-SiO 2 Composite preparation of nano-SiO 2The modified short fibers are grafted and prepared into fiber felt. The modified short fibers have a feather-like bionic structure. The short fibers are interlocked, which effectively enhances the friction between the short fibers, limits the slippage of the short fibers, enhances the interlayer bonding strength, inhibits delamination, limits crack propagation, and improves the overall mechanical properties of the composite material.

[0008] As a further improvement of the technical solution of the adhesive film of the present invention, the thermosetting resin system is a thermosetting resin system having molecular-scale cross-linked network structure characteristics formed by fully moderating the resin matrix, curing agent and reaction aid through mechanical stirring and chemical reaction.

[0009] As a further improvement of the technical solution of the adhesive film of the present invention, the short fibers include any one or more mixtures of glass fibers, quartz fibers, aramid fibers, and ultra-high molecular weight polyethylene fibers.

[0010] As a further improvement of the technical solution of the adhesive film of the present invention, the resin matrix is ​​any one or more mixtures of epoxy resin, unsaturated polyester resin and phenolic resin.

[0011] As a further improvement of the technical solution of the adhesive film of the present invention, the nano-SiO 2 Nano-SiO in grafted short fibers 2 The loading amount on the staple fibers was 1~5 wt% of the staple fibers.

[0012] As a further improvement of the technical solution of the adhesive film of the present invention, the length of the short fiber is 0.2-15 mm, and the aspect ratio is 200-3000; the nano-SiO 2 It is a sphere with a diameter of 50~100 nm.

[0013] As a further improvement of the technical solution of the adhesive film of the present invention, the fiber felt is made of nano-SiO 2 The grafted short fibers are prefabricated into a randomly oriented, uniformly dispersed mat with a thickness of 15-200 μm and an area density of 5-100 g / m 2 .

[0014] As a further improvement of the technical solution of the adhesive film of the present invention, the thickness of the adhesive film is 0.05~0.2 mm; the dielectric constant value of the cured product of the adhesive film can reach 2.38~2.64, and the dielectric loss value can reach 0.0014~0.0025; the bending strength of the cured product of the adhesive film can reach 120~160 MPa, the maximum bending strain of the cured product of the adhesive film can reach 5~9%, and the type I critical energy release rate of the cured product of the adhesive film can reach 1.3~1.7 kJ / m 2 ; The critical energy release rate of type I bonding interface can reach 1.4~2.0 kJ / m2 The critical energy release rate of the bonding interface type II can reach 2.1~2.8 kJ / m 2 , the interlaminar shear strength can reach 79~95 MPa.

[0015] The present invention further provides a method for preparing a low-dielectric and high-toughness adhesive film that can be used for a heterogeneous interface, comprising the following steps:

[0016] a. Short fiber loaded with nano-SiO 2 Preparation of Nano-SiO 2 Grafted staple fibers:

[0017] The continuous fibers are cut to a predetermined length and soaked in acetone to remove impurities or sizing agents attached to the surface; the nano-SiO 2 Add to the mixed solvent of deionized water / anhydrous ethanol, stir the prepared solution to form nano-SiO 2 Suspension; put the treated short fibers into the stirred nano-SiO 2 Suspension, take out the short fibers and dry them in vacuum; add KH-550 to a mixed solvent of deionized water / anhydrous ethanol to prepare a KH-550 solution, soak the dried short fibers in the prepared KH-550 solution, take them out, and dry them in vacuum;

[0018] b. Preparation of Nano-SiO 2 Grafted short fiber mat:

[0019] Nano-SiO 2 Grafted short fibers and hydroxyethyl cellulose are added to deionized water in sequence; through mechanical stirring, hydroxyethyl cellulose is completely dissolved in water, and short fibers are stably suspended in the aqueous solution without settling; the suspension is slowly poured into a sieve parallel to the horizontal plane at a uniform speed, and after being rinsed, shaped, and dried, it is taken out to obtain nano-SiO 2 Grafted short fiber mat;

[0020] c. Prepare glue solution:

[0021] The resin matrix and the curing agent are mixed, and mechanically stirred until the color is uniform and there is no stratification; a reaction aid is added to the obtained product, and mechanically stirred until the color is uniform; then, the product is degassed in a vacuum oven until no bubbles are generated and then taken out for use;

[0022] d. Preparation of preformed adhesive film:

[0023] The glue prepared in step c. is applied by spraying or brushing to impregnate the nano-SiO prepared in step b. 2 The grafted short fiber mat uses a calender to control the content of the thermosetting resin system and the thickness of the film, and finally rolls it up to complete the preparation of the adhesive film.

[0024] The present invention further provides a further improvement of the technical solution of the preparation method, wherein the curing agent is any one or more mixtures of amine curing agents and acid anhydride curing agents; and the reaction aid includes any one or more mixtures of initiators, promoters, and catalysts.

[0025] The low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces and the preparation method thereof described in the present invention have the following beneficial effects compared with the prior art: the adhesive film described in the present invention is suitable for various heterogeneous structure interfaces such as metal phase and fiber-reinforced composite materials, ceramic phase and fiber-reinforced composite materials, fiber-reinforced composite materials and fiber-reinforced composite materials, and can also be used for bonding and compounding sandwich materials with non-continuous characteristics, such as foam materials, honeycomb materials, etc. The adhesive film of the present invention can show strong heterogeneous interface bonding strength, improve the critical energy release rate of the entire material, effectively inhibit interlayer delamination failure and penetrating damage and non-penetrating damage caused by out-of-plane impact to the composite material, and at the same time have high wave transmission performance. It can be applied to structures with high requirements for impact resistance and wave transmission performance, such as weather radar covers, vehicle antenna covers, aircraft shells, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] Figure 1 The present invention is a schematic structural diagram of a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces.

[0029] Figure 2 The nano-SiO 2 Schematic diagram of feather bionic structure grafted with short fibers. A is nano-SiO 2 Schematic diagram of the interaction between grafted staple fibers, and B is a schematic diagram of the corresponding feather interlocking structure.

[0030] Figure 3 The nano-SiO2 loaded on the surface of the short fiber under the microscope in Example 1 2 State diagram. It can be observed that nano-SiO 2 The particle size is relatively consistent and evenly dispersed on the fiber surface. DETAILED DESCRIPTION

[0031] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0033] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0034] The present invention provides a specific embodiment of a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces, comprising a matrix phase and a fiber mat, wherein the fiber mat is impregnated in the matrix phase to form an adhesive film; the matrix phase comprises a thermosetting resin system; the fiber mat is a short fiber used as a carrier to load nano-SiO 2 Prepared nano-SiO 2 Short fibers are grafted and made into fiber felt; the short fibers are organic synthetic fibers or inorganic fibers with low dielectric constant.

[0035] In one embodiment provided by the present invention, the matrix phase is made of a thermosetting resin system, which is a thermosetting resin system having molecular-scale cross-linked network structure characteristics formed by a resin matrix, a curing agent and a reaction aid being fully moderated by mechanical stirring and formed through a chemical reaction.

[0036] Specifically, the resin matrix is ​​any one or more mixtures of epoxy resin, unsaturated polyester resin, and phenolic resin. The epoxy resin includes E-44 epoxy resin, E-51 epoxy resin, etc. The unsaturated polyester resin includes 901 unsaturated polyester resin, 904 unsaturated polyester resin, etc. The phenolic resin includes 2402 phenolic resin, 2123 phenolic resin, etc.

[0037] Further, the curing agent is any one or more mixtures of amine curing agents and acid anhydride curing agents, such as D400 polyurethane amine curing agent, D800 polyurethane amine curing agent, etc. The acid anhydride curing agent includes HHPA acid anhydride curing agent, PSPA acid anhydride curing agent, etc.

[0038] Furthermore, the reaction aid includes any one or more mixtures of initiators, promoters, and catalysts. The initiators include V-50 initiators, VA-044 initiators, etc., the promoters include DMP-30 promoters, BDMA promoters, etc., and the catalysts include imidazole catalysts, BF 3 -Cationic catalysts, etc.

[0039] In one embodiment provided by the present invention, the nano-SiO 2 Nano-SiO in grafted short fibers 2 The loading amount on the staple fibers was 1~5 wt% of the staple fibers.

[0040] In another embodiment provided by the present invention, the short fibers include any one or more mixtures of glass fibers, quartz fibers, aramid fibers, and ultra-high molecular weight polyethylene fibers. The length of the short fibers is 0.2 to 15 mm, and the aspect ratio is 200 to 3000. 2 It is a sphere with a diameter of 50~100 nm.

[0041] In one embodiment provided by the present invention, the fiber felt is made of nano-SiO 2 The grafted short fibers are prefabricated into a randomly oriented, uniformly dispersed mat with a thickness of 15-200 μm and an area density of 5-100 g / m 2 .

[0042] In the present invention, the thickness of the adhesive film is 0.05-0.2 mm; the dielectric constant value of the cured product of the adhesive film can reach 2.38-2.64, and the dielectric loss value can reach 0.0014-0.0025; the bending strength of the cured product of the adhesive film can reach 120-160 MPa, the maximum bending strain of the cured product of the adhesive film can reach 5-9%, and the type I critical energy release rate of the cured product of the adhesive film can reach 1.3-1.7 kJ / m 2 ; The critical energy release rate of type I bonding interface can reach 1.4~2.0 kJ / m 2 The critical energy release rate of the bonding interface type II can reach 2.1~2.8 kJ / m 2 , the interlaminar shear strength can reach 79~95 MPa.

[0043] The present invention also provides a method for preparing a low-dielectric and high-toughness adhesive film that can be used for a heterogeneous interface, comprising the following steps:

[0044] a. Short fiber loaded with nano-SiO 2 Preparation of Nano-SiO 2 Grafted staple fibers:

[0045] The continuous fibers are cut to a predetermined length and soaked in acetone to remove impurities or sizing agents attached to the surface; the nano-SiO 2 Add to the mixed solvent of deionized water / anhydrous ethanol, stir the prepared solution to form nano-SiO 2Suspension; put the treated short fibers into the stirred nano-SiO 2 Suspension, take out the short fibers and dry them in vacuum; add KH-550 to a mixed solvent of deionized water / anhydrous ethanol to prepare a KH-550 solution, soak the dried short fibers in the prepared KH-550 solution, take them out, and dry them in vacuum;

[0046] b. Preparation of Nano-SiO 2 Grafted short fiber mat:

[0047] Nano-SiO 2 Grafted short fibers and hydroxyethyl cellulose are added to deionized water in sequence; through mechanical stirring, hydroxyethyl cellulose is completely dissolved in water, and short fibers are stably suspended in the aqueous solution without settling; the suspension is slowly poured into a sieve parallel to the horizontal plane at a uniform speed, and after being rinsed, shaped, and dried, it is taken out to obtain nano-SiO 2 Grafted short fiber mat;

[0048] c. Prepare glue solution:

[0049] The resin matrix and the curing agent are mixed, and mechanically stirred until the color is uniform and there is no stratification; a reaction aid is added to the obtained product, and mechanically stirred until the color is uniform; then, the product is degassed in a vacuum oven until no bubbles are generated and then taken out for use;

[0050] d. Preparation of preformed adhesive film:

[0051] The glue prepared in step c. is applied by spraying or brushing to impregnate the nano-SiO prepared in step b. 2 The grafted short fiber mat uses a calender to control the content of the thermosetting resin system and the thickness of the film, and finally rolls it up to complete the preparation of the adhesive film.

[0052] In step a., the length of the short fiber is 0.2-15 mm, and the aspect ratio is 200-3000. In the mixed solvent of deionized water / anhydrous ethanol, the volume ratio of deionized water to anhydrous ethanol is 1:3-1:4. The mass fraction of KH-550 in the KH-550 solution is 0.5%-1%. The nano-SiO 2 The treated short fibers are in the nano-SiO 2 The immersion time in the suspension is 0.5 h~1 h; 2 The short fibers taken out of the suspension are vacuum dried at a drying temperature of 50°C to 100°C and a drying time of 1 h to 2 h. The dried short fibers are immersed in the KH-550 solution for 0.5 h to 1 h; the short fibers taken out of the KH-550 solution are vacuum dried at a drying temperature of 50°C to 100°C and a drying time of 1 h to 2 h.

[0053] In step b., the nano-SiO 2 The mass ratio of the grafted staple fiber to the hydroxyethyl cellulose is 1:0.004~1:0.008; the stirring method is stirring with a magnetic stirrer, and the stirring rate is 1000r / min~3000r / min; the specific method of rinsing in the present invention is to use a spray pot to spray the fiber felt until water drips, and repeat it many times until the dripping liquid is no longer viscous, and the specific method of shaping is to put the fiber felt into a vacuum oven for vacuuming, and dry it at high temperature in a vacuum for shaping, the drying temperature is 50℃~100℃, and the drying time is 1 h~2 h.

[0054] In step c., the mass ratio of the resin matrix to the curing agent, the amount of the reaction aid added, and the degassing temperature in the vacuum oven need to be determined according to the set numerical system.

[0055] In step d., the thickness of the adhesive film is 0.05-0.2 mm.

[0056] When used specifically, the adhesive film prepared by the present invention is placed between objects to be bonded, and the adhesive is cured by hot pressing or autoclave technology to complete the bonding.

[0057] In the present invention, the nano-SiO 2 Grafted short fibers can improve the overall modulus of the interlayer phase of the heterogeneous interface, play a role in stress transfer, and improve the overall bearing capacity of the structure; when the structure is subjected to out-of-plane impact, the cracks extend between the layers. 2 When grafted with short fibers, they can connect the two sides of the crack, reduce and eliminate the stress concentration generated by the crack extension tip, hinder the crack from extending between layers, and thus play a role in inhibiting delamination. 2 Nano-SiO grafted onto short fibers 2 Through intrinsic plastic deformation, debonding from the matrix and short fibers, and inducing plastic deformation of the matrix, the crack propagation is hindered, the crack tip is blunted, and the interlayer delamination caused by out-of-plane impact is resisted. 2 The nano-SiO 2 The grafted short fibers adopt a bionic feather structure. When the interlayer is stretched tangentially, the adjacent fibers are interlocked, which limits the fiber pull-out, limits the plastic deformation to a small local scale, and reinforces the interlayer phase of the heterogeneous interface, so that the overall stiffness of the structure can be maintained. 2The amount of introduction is small, the curing degree of the thermosetting resin system will not be affected, and its chemical properties can be maintained. At the same time, because the thermosetting resin system as a matrix is 2 The wetting and coating of the grafted short fibers enhances the bridging effect between them and the heterogeneous interface, and the bonding strength and bending properties of the adhesive are greatly improved. 2 The amount of nano-SiO2 introduced is small, and it is loaded on short fibers to prepare fiber mats, which further increases its dispersion in the resin matrix, making it evenly distributed and showing obvious interface effects. 2 The particles act as connecting points between molecular chains in the resin matrix. Their steric hindrance reduces the mobility of molecular chain segments, thereby hindering the transmission of carriers, weakening the overall polarization strength, and thus reducing the dielectric constant of the adhesive.

[0058] The technical solution of the present invention is described in detail below through specific embodiments. Example 1

[0059] In this embodiment, the two materials to be bonded are respectively a glass fiber reinforced epoxy resin-based composite material and an ultra-high molecular weight polyethylene fiber reinforced epoxy resin-based composite material.

[0060] The preparation method of the glass fiber reinforced epoxy resin-based composite material is as follows: weigh 150g of E-51 epoxy resin, add 118.5g of HHPA anhydride curing agent and 0.7g of DMP-30 accelerator, stir the three evenly and then ultrasonically disperse for 10 minutes, then put the prepared resin into a vacuum oven at 50℃ for vacuum degassing for 10 minutes. Apply a mold release agent to the mold and repeat three times. Orthogonal laying is adopted, the fiber cloth is impregnated with resin, and an adhesive film is directly laid between every two layers of glass fiber prepreg, and 10 layers are laid to prepare the prepreg. The prepreg is placed in the mold, the mold is covered with a polytetrafluoroethylene film, and hot-pressed in a hot press at 100℃ and 0MPa for 45 minutes; then the temperature is adjusted to 140℃ and hot-pressed for 2 hours. After the hot pressing is completed, the prepared glass fiber reinforced epoxy resin-based composite material is taken out.

[0061] 2) The preparation method of ultra-high molecular weight polyethylene fiber reinforced epoxy resin-based composite material is as follows: weigh 150g of E-51 epoxy resin, add 118.5g of HHPA anhydride curing agent and 0.7g of DMP-30 accelerator, stir the three evenly and ultrasonically disperse for 10 min, then put the prepared resin into a vacuum oven at 50℃ for vacuum degassing for 10 min. Apply mold release agent to the mold and repeat three times. Orthogonal laying is adopted, the fiber cloth is impregnated with resin, and an adhesive film is directly laid between every two layers of ultra-high molecular weight polyethylene fiber prepreg, and 10 layers are laid to prepare prepreg. The prepreg is placed in the mold, the mold is covered with polytetrafluoroethylene film, and hot pressed at 100℃ and 0MPa in a hot press for 45 min; then the temperature is adjusted to 140℃ and hot pressed for 2 h. After the hot pressing, the prepared ultra-high molecular weight polyethylene fiber reinforced epoxy resin-based composite material is taken out.

[0062] 3) The method for preparing the adhesive film of this embodiment comprises the following steps:

[0063] a. Short fiber loaded with nano-SiO 2 Preparation of Nano-SiO 2 Grafted staple fibers:

[0064] 10g of continuous glass fiber was cut into 5 mm in length and 1000 in aspect ratio, and then soaked in acetone for 0.5 h to remove impurities or sizing agents attached to the surface. 1g of nano-SiO 2 Add deionized water / anhydrous ethanol (volume ratio 1:3) into the mixed solvent, stir the prepared solution to form nano-SiO 2 Suspension; put the treated short fibers into the stirred nano-SiO 2 The suspension was soaked for 0.5 h, and then the short fibers were taken out and placed in a vacuum oven at 70 °C for vacuum drying for 1 h. KH-550 was added to a mixed solvent of deionized water / anhydrous ethanol (volume ratio 1:3) to prepare a KH-550 solution, wherein the mass fraction of KH-550 in the KH-550 solution was 0.5%. The dried short fibers were placed in the prepared KH-550 solution and soaked for 0.5 h and taken out, and then placed in a vacuum oven at 70 °C for vacuum drying for 1 h. Nano-SiO 2 The loading amount is 5 wt%.

[0065] b. Preparation of Nano-SiO 2 Grafted short fiber mat:

[0066] Nano-SiO 2Grafted short fibers and hydroxyethyl cellulose were added to deionized water in a ratio of 1:0.006; the mixture was stirred at 2000 r / min in a magnetic stirrer to make the hydroxyethyl cellulose completely dissolved in water and the short fibers stably suspended in the aqueous solution without settling; the suspension was slowly poured into a sieve parallel to the horizontal plane at a uniform speed, and the fiber felt was sprayed with a spray bottle until water dripped, and the process was repeated several times until the dripping liquid was no longer viscous, and the fiber felt was placed in a vacuum oven for high-temperature drying and shaping, with a drying temperature of 70°C and a time of 2 h; the obtained fiber felt had a thickness of 100 μm and a surface density of 50 g / m 2 .

[0067] c. Prepare glue solution:

[0068] 10g E-51 epoxy resin matrix was mixed with 7.9g HHPA curing agent, and mechanically stirred until the color was uniform and without stratification; 0.06g DMP-3 accelerator was added to the obtained product, and mechanically stirred until the color was uniform; then, the product was degassed in a vacuum oven at 50°C until no bubbles were generated and then taken out for use.

[0069] d. Preparation of preformed adhesive film:

[0070] The glue prepared in step c. is applied by brushing to impregnate the nano-SiO 2 Grafted short fiber thin mat, the impregnated short fiber thin mat is calendered by a calender at 5MPa, the film thickness is controlled to be 0.15mm, and finally rolled up to complete the preparation of the adhesive film.

[0071] 4) Use a hard single-sided mold, first apply a release agent on the mold surface three times, wait for the release agent to dry, and after there is no obvious trace of liquid on the mold surface, place a glass fiber prepreg on it, and directly lay an adhesive film between every two layers of glass fiber prepreg, and then lay an ultra-high molecular weight polyethylene fiber prepreg of the same specification on it, and lay the same adhesive film between the two. Lay an adhesive film between every two layers of ultra-high molecular weight polyethylene fiber prepreg, place the material system after laying in a hot press, and cure it at a pressure of 15 MPa for 4 hours to complete the secondary bonding preparation of low dielectric and high toughness composite materials. Comparative Example 1

[0072] A pure epoxy resin prepolymer adhesive film, the preparation process of which is based on step 3) in reference to Example 1, without adding nano-SiO 2 The thickness of the adhesive film is 0.15 mm. The preparation of the composite material is based on steps 1), 2) and 4) in Example 1.

[0073] The dielectric constant of the cured adhesive film is 3.86, and the dielectric loss is 0.0260; the flexural strength of the cured adhesive film is 97 MPa, the maximum flexural strain of the cured adhesive film is 5%, and the type I critical energy release rate of the cured adhesive film is 0.9 kJ / m 2 ; The critical energy release rate of type I bonding interface is 1.1 kJ / m 2 The critical energy release rate of type II bonding interface is 1.4 kJ / m 2 , the interlaminar shear strength is 61 MPa. Comparative Example 2

[0074] A method of adding nano-SiO2 to epoxy resin 2 The adhesive film is prepared by referring to steps cd in Example 1, and only the nano-SiO2 on the short fibers of Example 1 is added to the epoxy resin matrix. 2 The loading amount is equal to that of nano-SiO 2 The thickness of the obtained adhesive film was 0.15 mm. The preparation of the composite material was carried out according to steps 1), 2) and 4) in Example 1.

[0075] The dielectric constant of the cured adhesive film is 2.96, and the dielectric loss is 0.0025. The flexural strength of the cured adhesive film is 116 MPa, the maximum flexural strain of the cured adhesive film is 6%, and the type I critical energy release rate of the cured adhesive film is 1.2 kJ / m 2 ; The critical energy release rate of type I bonding interface can reach 1.3 kJ / m 2 The critical energy release rate of type II bonding interface is 1.7 kJ / m 2 , the interlaminar shear strength is 65 MPa. Comparative Example 3

[0076] An adhesive film of a fiber mat impregnated with epoxy resin, wherein the preparation process is based on the relevant steps in Example 1, and when preparing the fiber mat, the short fibers are not loaded with nano-SiO 2 The fiber felt prepared by impregnating pure short fibers with epoxy resin alone was used to obtain an adhesive film. The thickness of the obtained adhesive film was 0.15 mm. The preparation of the composite material was based on steps 1), 2) and 4) in Example 1.

[0077] The dielectric constant of the cured adhesive film is 2.78, and the dielectric loss is 0.0023. The flexural strength of the cured adhesive film is 124 MPa, the maximum flexural strain of the cured adhesive film is 8%, and the type I critical energy release rate of the cured adhesive film is 1.4 kJ / m 2 ; The critical energy release rate of type I bonding interface can reach 1.5 kJ / m2 The critical energy release rate of type II bonding interface is 1.9 kJ / m 2 , the interlaminar shear strength is 74 MPa. Example 2

[0078] In this embodiment, the two materials to be bonded are glass fiber reinforced epoxy resin based composite material and B 4 C ceramics.

[0079] 1) The preparation method of the glass fiber reinforced epoxy resin-based composite material is as follows: weigh 150g of E-51 epoxy resin, add 118.5g of HHPA anhydride curing agent and 0.7g of DMP-30 accelerator, stir the three evenly and then ultrasonically disperse for 10 minutes, then put the prepared resin into a vacuum oven at 50℃ for vacuum degassing for 10 minutes. Apply a mold release agent to the mold and repeat three times. Orthogonal laying is adopted, the fiber cloth is impregnated with resin, and an adhesive film is directly laid between every two layers of glass fiber prepreg, and 10 layers are laid to prepare the prepreg. The prepreg is placed in the mold, the mold is covered with a polytetrafluoroethylene film, and hot-pressed in a hot press at 100℃ and 0MPa for 45 minutes; then the temperature is adjusted to 140℃ and hot-pressed for 2 hours. After the hot pressing is completed, the prepared glass fiber reinforced epoxy resin-based composite material is taken out.

[0080] 2) B 4 The treatment method for C ceramics is to clean the dirt on the surface of the ceramic piece with deionized water, and then wipe it with ethanol several times.

[0081] 3) The method for preparing the adhesive film of this embodiment comprises the following steps:

[0082] a. Short fiber loaded with nano-SiO 2 Preparation of Nano-SiO 2 Grafted staple fibers:

[0083] 10g of continuous glass fiber was cut into 10 mm lengths with an aspect ratio of 2000 and soaked in acetone for 0.5 h to remove impurities or sizing agents attached to the surface. 1g of nano-SiO 2 Add deionized water / anhydrous ethanol (volume ratio 1:3) into the mixed solvent, stir the prepared solution to form nano-SiO 2 Suspension; put the treated short fibers into the stirred nano-SiO 2The suspension was soaked for 0.5 h, and then the short fibers were taken out and placed in a vacuum oven at 70 °C for vacuum drying for 1 h. KH-550 was added to a mixed solvent of deionized water / anhydrous ethanol (volume ratio 1:3) to prepare a KH-550 solution, wherein the mass fraction of KH-550 in the KH-550 solution was 0.5%. The dried short fibers were placed in the prepared KH-550 solution and soaked for 0.5 h and taken out, and then placed in a vacuum oven at 70 °C for vacuum drying for 1 h. Nano-SiO 2 The loading amount is 5 wt%;

[0084] b. Preparation of Nano-SiO 2 Grafted short fiber mat:

[0085] Nano-SiO 2 Grafted short fibers and hydroxyethyl cellulose were added to deionized water in a ratio of 1:0.006. The mixture was stirred at 2000 r / min in a magnetic stirrer to make the hydroxyethyl cellulose completely dissolved in water and the short fibers stably suspended in the aqueous solution without settling. The suspension was slowly poured into a sieve parallel to the horizontal plane at a uniform speed, and the fiber felt was sprayed with a spray bottle until water dripped, and the process was repeated several times until the dripping liquid was no longer viscous. The fiber felt was placed in a vacuum oven for high-temperature drying and shaping, with a drying temperature of 70 °C and a time of 2 h. The obtained fiber felt had a thickness of 100 μm and an area density of 80 g / m 2 .

[0086] c. Prepare glue solution:

[0087] 10 g of E-51 epoxy resin matrix and D400 curing agent were mixed and mechanically stirred until the color was uniform and there was no stratification; then, the mixture was degassed in a vacuum oven at 50°C until no bubbles were generated and the mixture was taken out for use;

[0088] d. Preparation of preformed adhesive film:

[0089] The glue prepared in step c. is applied by brushing to impregnate the nano-SiO 2 Grafted short fiber thin mat, the impregnated short fiber thin mat is calendered by a calender at 5 MPa, the film thickness is controlled to be 0.15 mm, and finally rolled up to complete the preparation of the adhesive film.

[0090] 4) A hard single-sided mold is used, and a ceramic sheet is placed on it as a substrate. After the surface of the ceramic is cleaned, an adhesive film is directly laid on it, and then glass fiber prepregs are arranged layer by layer. An adhesive film is laid between every two layers of carbon fiber prepregs. The material system after laying is sealed in a sealed tooling; the tooling is transferred to an autoclave, and it is cured and molded for 2 hours under the conditions of an internal pressure of 1 atm and an external pressure of 3 atm to complete the one-piece preparation of a low-dielectric and high-toughness composite material. Comparative Example 4

[0091] A pure epoxy resin prepolymer adhesive film, the preparation process of which is based on step 3) in reference to Example 2, without adding nano-SiO 2 The thickness of the adhesive film is 0.15 mm. The preparation of the composite material is based on steps 1), 2) and 4) in Example 2.

[0092] The dielectric constant of the cured adhesive film is 3.91, and the dielectric loss is 0.0268; the flexural strength of the cured adhesive film is 115 MPa, the maximum flexural strain of the cured adhesive film is 4%, and the type I critical energy release rate of the cured adhesive film is 1.1 kJ / m 2 ; The critical energy release rate of type I bonding interface is 1.4 kJ / m 2 The critical energy release rate of bonding interface type II is 2.0 kJ / m 2 , the interlaminar shear strength is 73 MPa. Comparative Example 5

[0093] A method of adding nano-SiO2 to epoxy resin 2 The adhesive film is prepared by referring to steps cd in Example 2, and only the nano-SiO2 on the short fibers in Example 2 is added to the epoxy resin matrix. 2 The loading amount is equal to that of nano-SiO 2 The thickness of the obtained adhesive film was 0.15 mm. The preparation of the composite material was carried out according to steps 1), 2) and 4) in Example 2.

[0094] The dielectric constant of the cured adhesive film is 3.11, and the dielectric loss is 0.0031. The bending strength of the cured adhesive film is 122 MPa, the maximum bending strain of the cured adhesive film is 5%, and the type I critical energy release rate of the cured adhesive film is 1.2 kJ / m 2 ; The critical energy release rate of type I bonding interface can reach 1.5kJ / m 2 The critical energy release rate of type II bonding interface is 2.1 kJ / m 2 , the interlaminar shear strength is 78 MPa. Comparative Example 6

[0095] An adhesive film of a fiber mat impregnated with epoxy resin, wherein the preparation process is based on the relevant steps in Example 2, and when preparing the fiber mat, the short fibers are not loaded with nano-SiO 2The fiber felt prepared by impregnating pure short fibers with epoxy resin alone was used to obtain an adhesive film. The thickness of the obtained adhesive film was 0.15 mm. The preparation of the composite material was carried out in accordance with steps 1), 2) and 4) in Example 2.

[0096] The dielectric constant of the cured adhesive film is 2.86, and the dielectric loss is 0.0026; the flexural strength of the cured adhesive film is 139 MPa, the maximum flexural strain of the cured adhesive film is 8%, and the type I critical energy release rate of the cured adhesive film is 1.4 kJ / m 2 ; The critical energy release rate of type I bonding interface can reach 1.7 kJ / m 2 The critical energy release rate of type II bonding interface is 2.3 kJ / m 2 , the interlaminar shear strength is 82 MPa.

[0097] Performance comparison between each embodiment and comparative example:

[0098] By comparing the embodiment with the comparative example, due to the low dielectric properties of the materials used and the special feather-like bionic structure of the adhesive film prepared by the method, the embodiment has a low dielectric constant and dielectric loss while taking into account good mechanical properties. At the same time, the interface energy release rate and interlayer shear strength are significantly improved, indicating that the interface obtained by using the adhesive film of the present invention has excellent resistance to crack generation and expansion, improves the interlayer bonding strength, and has broad application prospects.

[0099] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A method for preparing a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces. It is characterized in that The steps include: a. Short fiber loaded with nano-SiO 2 Preparation of Nano-SiO 2 Grafted staple fibers: The continuous fibers are cut to a predetermined length and soaked in acetone to remove impurities or sizing agents attached to the surface; the nano-SiO 2 Add to the mixed solvent of deionized water / anhydrous ethanol, stir the prepared solution to form nano-SiO 2 Suspension; put the treated short fibers into the stirred nano-SiO 2 suspension, taking out the short fibers and drying them under vacuum; adding KH-550 to a mixed solvent of deionized water / anhydrous ethanol to prepare a KH-550 solution, soaking the dried short fibers in the prepared KH-550 solution, taking them out, and drying them under vacuum; the short fibers include any one or more mixtures of glass fibers, quartz fibers, aramid fibers, and ultra-high molecular weight polyethylene fibers; b. Preparation of Nano-SiO 2 Grafted short fiber mat: Nano-SiO 2 Grafted short fibers and hydroxyethyl cellulose are added to deionized water in sequence; through mechanical stirring, hydroxyethyl cellulose is completely dissolved in water, and short fibers are stably suspended in the aqueous solution without settling; the suspension is slowly poured into a sieve parallel to the horizontal plane at a uniform speed, and after being rinsed, shaped, and dried, it is taken out to obtain nano-SiO 2 Grafted short fiber mat; c. Prepare glue solution: The resin matrix and the curing agent are mixed, and mechanically stirred until the color is uniform and there is no stratification; a reaction aid is added to the obtained product, and mechanically stirred until the color is uniform; then, the product is degassed in a vacuum oven until no bubbles are generated and then taken out for use; d. Preparation of preformed adhesive film: The glue prepared in step c. is applied by spraying or brushing to impregnate the nano-SiO prepared in step b. 2 The grafted short fiber mat uses a calender to control the content of the thermosetting resin system and the thickness of the film, and finally rolls it up to complete the preparation of the adhesive film.

2. A method for preparing a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces according to claim 1, It is characterized in that The thermosetting resin system is a thermosetting resin system having a molecular-scale cross-linked network structure formed by fully mixing a resin matrix, a curing agent and a reaction aid through mechanical stirring and chemical reaction.

3. A method for preparing a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces according to claim 2, It is characterized in that The resin matrix is ​​any one or more mixtures of epoxy resin, unsaturated polyester resin and phenolic resin.

4. The method for preparing a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces according to claim 1, It is characterized in that The nano-SiO 2 Nano-SiO in grafted short fibers 2 The loading amount on the short fibers is 1~5wt% of the short fibers.

5. The method for preparing a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces according to claim 1, It is characterized in that The short fiber has a monofilament length of 0.2-15 mm and an aspect ratio of 200-3000; the nano-SiO 2 It is a sphere with a diameter of 50~100 nm.

6. The method for preparing a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces according to claim 1, It is characterized in that The nano-SiO 2 Grafted short fiber mat is made of nano-SiO 2 The grafted short fibers are preformed into randomly oriented, uniformly dispersed mats with a thickness of 15-200 μm and an area density of 5-100 g / m 2 .

7. The method for preparing a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces according to claim 1, It is characterized in that The thickness of the adhesive film is 0.05-0.2 mm; the dielectric constant value of the cured adhesive film can reach 2.38-2.64, and the dielectric loss value can reach 0.0014-0.0025; the bending strength of the cured adhesive film can reach 120-160 MPa, the maximum bending strain of the cured adhesive film can reach 5-9%, and the type I critical energy release rate of the cured adhesive film can reach 1.3-1.7 kJ / m 2 ; The critical energy release rate of type I bonding interface can reach 1.4~2.0 kJ / m 2 The critical energy release rate of the bonding interface type II can reach 2.1~2.8 kJ / m 2 , the interlaminar shear strength can reach 79~95 MPa.

8. The method for preparing a low-dielectric and high-toughness adhesive film that can be used for heterogeneous interfaces according to claim 1, It is characterized in that The curing agent is any one or more mixtures of amine curing agents and acid anhydride curing agents; the reaction aid includes any one or more mixtures of initiators, accelerators, and catalysts.

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