Method for improving shearing performance of wave-absorbing prepreg and wave-absorbing prepreg
Through multi-scale fiber topology control technology, the pore size and interface structure of fiber fabrics are optimized, and the problem of weak bonding ability between traditional fiber fabrics and resins is solved, and the shear performance and stability of wave absorbing prepregs are improved.
Patent Information
- Application Number
- CN202510673619.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-23
- Publication Date
- 2025-07-25
AI Technical Summary
Traditional fiber fabrics are difficult to improve their binding ability with resin through conventional sizing agents or surface treatment methods, resulting in insufficient shearing performance of the absorbing prepreg and unable to meet the requirements of the absorbing composite materials.
Multi-scale fiber topology control technology is adopted to optimize the pore size and interface structure of the fiber fabric through twisting, stretching, cyclic wetting and yarn braiding, forming a multi-layer core-shell structure, enhancing the bonding force between the fiber and the resin, and improving shear performance.
It significantly improves the shear strength and stability of the absorbing prepreg, solves the problem of falling off after the absorbing prepreg and the target substrate, and ensures the safety performance of the applied products.
Smart Images
Figure CN120363510A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the technical field of composite prepregs, and specifically relates to a method for improving the shear performance of microwave-absorbing prepregs and microwave-absorbing prepregs. Background Art
[0002] Microwave-absorbing composite materials are a type of structural functional material with independent load-bearing and protection capabilities. Structural components made of microwave-absorbing composite materials can replace or partially replace the corresponding metal structures on the target body, thereby reducing the stealth function of the target detected by radar. Therefore, when structural microwave-absorbing materials that combine microwave-absorbing functions with load-bearing or anti-ballistic protection functions appear, it directly demonstrates their superiority in use as radar-band stealth materials on weaponry. The difference between microwave-absorbing composite materials and ordinary composite materials lies in that a certain proportion of electromagnetic loss attenuation materials (absorbents) need to be incorporated into the microwave-absorbing composite material layers. Only when these absorbent materials can be quantitatively and uniformly distributed in the various structural layers of the composite material can the corresponding microwave-absorbing performance be obtained. Therefore, as a special application field of resin-based composite materials, the prepreg preparation process of microwave-absorbing composite materials requires ensuring the various properties of the materials, especially the microwave-absorbing performance and shear performance.
[0003] Among various properties, the shear modulus is an important indicator for evaluating the performance of prepreg composite materials, characterizing the possibility of the microwave-absorbing prepreg peeling off from the carbon fiber substrate when local defects occur. Generally, the higher the shear performance, the more difficult it is for the microwave-absorbing prepreg to peel off from the carbon fiber substrate, and thus the higher the safety of the functional layer. However, currently, traditional fiber fabrics, especially aramid fiber fabrics, are difficult to improve surface activity through conventional sizing agents or surface treatment methods, resulting in weak binding ability between the fiber fabric and the resin, and the shear strength is even more difficult to meet the requirements of microwave-absorbing composite materials. Therefore, there is an urgent need for a method to improve the binding ability between the fiber fabric and the resin to further improve the shear performance of microwave-absorbing prepregs. Summary of the Invention
[0004] The purpose of this application is to provide a method for improving the shear performance of microwave-absorbing prepregs and microwave-absorbing prepregs, which can improve the binding ability between the fiber fabric and the microwave-absorbing resin, and thus significantly improve the shear strength of microwave-absorbing prepregs.
[0005] To achieve the above purpose, this application provides a method for improving the shear performance of microwave-absorbing prepregs, including the following steps:
[0006] Mix the resin and the absorbent in proportion and heat to melt to obtain a composite microwave-absorbing resin;
[0007] Twist the fiber into yarn, then perform stretching treatment, and use the resin and the composite microwave-absorbing resin to infiltrate cyclically. After the infiltration is completed, heat and pre-cure to obtain a pretreated yarn;
[0008] Perform doubling and weaving treatment on the pretreated yarn to obtain a fiber-reinforced fabric;
[0009] Prepare an absorbent adhesive film by double-roll grinding of the composite absorbent resin;
[0010] After coating the absorbent adhesive film on both sides of the fiber-reinforced fabric respectively, perform composite treatment to obtain an absorbent prepreg;
[0011] Among them, the doubling and weaving treatment specifically includes: performing doubling and weaving treatment on the pretreated yarn by combining any 2 to 5 pretreated yarns into 1 yarn, and the pretreated yarn includes at least one of the pretreated yarns in the warp direction and the pretreated yarns in the weft direction;
[0012] The linear density of the fiber is 500 dtex to 7000 dtex, and the unfolded width of the fiber is 10 μm to 1000 μm.
[0013] Furthermore, the texture of the fiber-reinforced fabric includes at least one of plain weave, twill weave, and satin weave.
[0014] Furthermore, the fiber includes one or two of glass fiber, quartz fiber, aramid fiber, poly(p-phenylene benzobisoxazole) fiber, and polyimide fiber, and the mixing ratio of any two fibers is 50 wt% to 95 wt%, preferably aramid fiber.
[0015] Furthermore, the tensile strength is 10 MPa to 50 MPa.
[0016] Furthermore, the absorbent includes at least one of carbon-based absorbents, iron-based absorbents, and dielectric-based absorbents. The mass fraction of the absorbent in the absorbent adhesive film (or the composite absorbent resin) is 50 wt% to 90 wt%, and the mass fraction of the absorbent adhesive film in the absorbent prepreg is 80 wt% to 98 wt%. It can be understood that the absorbent content in the composite absorbent resin and the absorbent adhesive film is the same.
[0017] Even further, the carbon-based absorbent includes at least one of graphene, carbon black, carbon nanotubes, expanded graphene, and their composites; the iron-based absorbent includes at least one of carbonyl iron, iron silicon aluminum, and magnetite and their composites; the dielectric-based absorbent includes at least one of silicon carbide, alumina, carbon fiber, and their composites.
[0018] Furthermore, the resin in the composite absorbent resin includes at least one of epoxy resin, bismaleimide resin, and cyanate resin.
[0019] Further, in the cyclic infiltration, the number of times of infiltrating with the resin and the composite wave-absorbing resin is 3 to 5 times each;
[0020] The temperature of the heat pre-curing is 60°C to 90°C, and the time of the heat pre-curing is 10 min to 30 min.
[0021] Further, the composite treatment includes: passing through a pressure roller with a pressure of 20 MPa to 25 MPa, so that the fiber-reinforced fabric is combined with the wave-absorbing adhesive film coated on its surface.
[0022] This application also discloses a wave-absorbing prepreg prepared by the above method.
[0023] To sum up, this application has the following advantages:
[0024] The method for improving the shear performance of the wave-absorbing prepreg disclosed in this application innovatively realizes the directional optimization of the interfacial mechanical properties of the wave-absorbing prepreg through the multi-scale fiber topology regulation technology. Specifically, by adopting the multi-axial spiral twisting process combined with the design of the gradient densification weaving topology structure, the following effects are achieved on the premise of maintaining the constant areal density and bulk density of the fibers:
[0025] (1) Precise regulation of mesoscopic structure parameters: ① The fiber unfolding width is optimized to the micron level (10 μm to 1000 μm), forming a continuous gradient distribution; ② After the fabric pore size distribution is iteratively optimized by the weaving parameters, the relationship between the pore size and the strength can be balanced; ③ A permeation channel network with fractal characteristics is constructed, significantly improving the resin infiltration kinetic efficiency.
[0026] (2) Reconstruction of the failure mechanism and interface strengthening. Through the design of the fiber-resin interface energy matching, the weak interface failure dominated by physical adsorption in the traditional process is transformed into the cohesive failure mode within the resin matrix phase. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 It is a schematic flow chart of the method for improving the shear performance of the wave-absorbing prepreg provided by this application;
[0028] Figure 2 It is the surface state of the fiber fabric with and without doubling treatment provided in Example 1 and Comparative Example 2 of this application, where Figure 2 (A) is the surface state of the fiber fabric without doubling treatment in Comparative Example 1, Figure 2 (B) is the surface state of the fiber fabric with doubling treatment in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0029] The principles and features of the present application will be described below in conjunction with embodiments. The examples cited are only used to explain the present application and are not intended to limit the scope of the present application. For those conditions not specified in the embodiments, they shall be carried out according to conventional conditions or the conditions recommended by the manufacturer. For those reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.
[0030] In an application field of the present application, the shear strength of the wave-absorbing prepreg (also known as the radar wave-absorbing material prepreg) used in aircraft is mainly affected by the following factors. By regulating these factors, the required shear strength can be achieved: matrix resin type, fiber type, fiber content, curing process, interfacial compatibility, and material treatment. Generally, by selecting appropriate resins and fibers, and by optimizing the fiber content, controlling the curing process, and interfacial modification and other methods, the shear strength of the wave-absorbing prepreg can be effectively improved to meet the requirements of the aircraft in terms of stealth and structural performance. However, for traditional fiber fabrics, it is difficult to carry out interfacial modification by traditional sizing agents or surface treatment methods. Therefore, it is impossible to effectively improve the surface activity of the fiber fabric, resulting in weak bonding ability between the fiber fabric and the resin and insufficient shear strength.
[0031] Aiming at the deficiencies of the prior art, the present application adopts precise twisting technology and specific weaving technology to finely regulate the arrangement width of fibers and the pore size of fiber fabrics, thereby realizing the efficient penetration of wave-absorbing resin in fiber fabrics. In this process, the present application innovatively transforms the weak link caused by the insufficient interfacial bonding between resin and fiber in the traditional preparation process, and optimizes it into a failure mode dominated by the cohesive failure of the wave-absorbing resin, significantly enhancing the bonding strength between the wave-absorbing resin and the fiber fabric interface. In addition, this optimization strategy ensures that the shear performance of the wave-absorbing prepreg is significantly improved while the areal density and bulk density of the fibers remain constant, thus realizing the overall improvement of material performance.
[0032] As Figure 1 shown, the present application provides a method for improving the shear performance of wave-absorbing prepregs, including the following steps:
[0033] S10. Mix the resin and the absorbent in proportion and heat them to melt to obtain a composite wave-absorbing resin;
[0034] S20. Twist the fibers into yarns, then carry out stretching treatment, and use the resin and the composite wave-absorbing resin to infiltrate cyclically. After the infiltration is completed, heat and pre-cure to obtain pre-treated yarns;
[0035] S30. Carry out ply-yarn weaving treatment on the pre-treated yarns to obtain fiber-reinforced fabrics;
[0036] S40. Prepare a wave-absorbing adhesive film by double-roll grinding of the composite wave-absorbing resin;
[0037] S50. After coating the wave-absorbing adhesive film on both sides of the fiber-reinforced fabric respectively, perform a composite treatment to obtain a wave-absorbing prepreg.
[0038] In this application, by twisting, stretching, and cyclically infiltrating liquid resin, the mechanical properties of the fiber can be enhanced, and the bonding force between the fiber and the resin can also be enhanced; then through ply yarn weaving, a fiber-reinforced fabric with a specific structure and high strength can be formed, controlling the pore size of these fiber-reinforced fabrics, making it easier for the wave-absorbing resin to penetrate. Coating the wave-absorbing adhesive film (solid resin) on the surface of the fiber-reinforced fabric and through pressure composite, a prepreg with excellent shear properties and wave-absorbing properties can be prepared. Generally speaking, the preparation method of this application first enhances the mechanical properties of the fiber itself through pretreatment steps such as twisting, stretching, and cyclic infiltration, and then provides the basic structure of the fiber fabric through ply yarn weaving. Only the combined fiber fabric has good overall performance. The wave-absorbing adhesive film is responsible for providing the wave-absorbing function, and the fiber-reinforced fabric is responsible for providing support and structural strength. Therefore, the wave-absorbing prepreg prepared by the composite of the two can achieve the combination of function and structure. During the entire process, cyclic infiltration ensures the full combination of the resin and the fiber and forms a multi-layer core-shell structure. By heating and pre-curing this structure, the shear properties and stability of the prepreg are further improved. Thus, the problem of peeling off after the wave-absorbing prepreg is combined with the target substrate is solved, which not only improves the strength of the fiber fabric but also ensures the safety performance of the final application product, such as the flight safety of an aircraft. Therefore, the wave-absorbing prepreg prepared in this application can be widely used in military stealth, electromagnetic compatibility and other fields.
[0039] In summary, the process method of this application combines multiple pretreatment steps of the fiber with various weaving modes, breaks through the technical barrier that traditional wave-absorbing materials have high absorption rate but low mechanical properties, and through the coupling optimization of parameters such as absorbent content, fiber linear density, and rolling pressure, realizes the simultaneous improvement of wave-absorbing performance and mechanical properties, and improves the shear strength of the wave-absorbing prepreg from multiple aspects.
[0040] In some alternative embodiments of this application, the ply yarn weaving treatment specifically includes: performing ply yarn weaving treatment on any 2 to 5 of the pretreated yarns by combining them into 1 yarn, and the pretreated yarns include at least one of the pretreated yarns in the warp direction and the pretreated yarns in the weft direction;
[0041] The texture of the fiber-reinforced fabric includes at least one of plain weave, twill weave, and satin weave.
[0042] In this application, through the discrete multi-axial parallel yarn topology technology, 2 to 5 pre-treated yarns (warp / weft) are integrated into a single reinforcement unit, which can form a quasi-fractal spatial arrangement of fiber bundles at the mesoscopic scale, form a hyperbolic pore structure, and effectively reduce the fiber density per unit area. Thus, without sacrificing the overall strength of the fiber fabric, the pore size of the fiber fabric is effectively increased. This improvement significantly enhances the permeability of liquid resin to the fiber fabric. It should be noted that the weaving methods in this application are all planar weaving techniques, and the core lies in precisely controlling the fabric pore size between 5000μm and 500000μm. If the fabric pores are too small, the shear strength will be insufficient due to the difficulty of resin infiltration; if the fabric pores are too large, the mechanical properties will be affected, such as insufficient tensile properties. The collaborative application of the parallel yarn operation and the twisting process together act to increase the pores of the fiber fabric, and this process will not have any negative impact on the areal density and bulk density of the fibers.
[0043] The areal density of fibers refers to the mass of fibers per unit area, and the size of the areal density of fibers directly affects the physical and process properties of prepregs. Generally speaking, the higher the areal density of fibers, the greater the strength of the prepreg, but at the same time, it will also increase its weight and thickness. On the contrary, reducing the areal density of fibers can reduce the weight of the prepreg, but may sacrifice a certain amount of strength. In addition, the areal density of fibers also affects the impregnation effect of the prepreg. Impregnation refers to the process in which the resin fully penetrates into the fiber bundles, and it is a key step in preparing high-quality prepregs. If the areal density of fibers is too high, the resin may be difficult to fully penetrate into the fiber interior, resulting in poor impregnation effect; while if the areal density of fibers is too low, the resin may penetrate excessively, causing too much resin on the surface of the prepreg and affecting its wave absorption performance. The bulk density of fibers (abbreviated as bulk density) refers to the mass of fiber materials per unit volume, which reflects the degree of compactness inside the fibers, that is, the arrangement and void conditions between fiber molecules. The bulk density can also affect the strength and durability of the fibers. Generally speaking, fibers with a higher bulk density have higher strength and better durability because the molecular bonding inside them is more compact. If the bulk density changes, it may affect the electromagnetic properties of the fibers, such as the dielectric constant and magnetic permeability, and thus affect the wave absorption performance. The change in bulk density will also affect the interfacial bonding ability between the fibers and the resin and the internal structure of the composite material, such as affecting the porosity, fiber distribution, etc., and thus affect the wave absorption performance.
[0044] Therefore, to avoid affecting the bonding ability between the resin and the fiber fabric and the wave absorption performance of the prepreg, in this application, planar parallel yarn weaving is adopted, so as to avoid affecting the areal density and bulk density of the fibers, that is, to ensure that while improving the shear performance of the wave-absorbing material through parallel yarn weaving, it will not affect the wave absorption performance of the wave-absorbing material.
[0045] In some alternative embodiments of the present application, the fiber includes one or two of glass fiber, quartz fiber, aramid fiber, poly(p-phenylene benzobisoxazole) fiber (PBO fiber), and polyimide fiber. When there are two kinds of fibers, their proportion relationship is any ratio, preferably 50wt% - 95wt%. Among them, due to the skin-core structure of aramid fiber, its shear performance is weaker among the above several kinds of fibers; therefore, in the subsequent embodiments of the present application, aramid fiber is mainly used as an example for illustration. The above fibers all have good wave-transparent performance, so that electromagnetic waves can fully enter the resin matrix for effective loss.
[0046] To ensure the permeability of the resin to the fiber fabric and the infiltration uniformity, in some alternative embodiments of the present application, the linear density of the fiber is 500 dtex - 7000 dtex, and the unfolded width of the fiber is 10 μm - 1000 μm. The main influencing factor of the unfolded width of the fiber is the thickness of the fiber, which is usually quantified by the linear density. The smaller the linear density of the fiber, the finer the fiber and the smaller the unfolded width. The present application selects fibers with a smaller linear density, effectively controlling the unfolded width of the fiber in the fabric, thereby increasing the surface pore size of the fiber fabric and promoting the infiltration of the resin into the fiber fabric. It should be noted that when the linear density of the fiber is too high, the infiltration degree of the resin will be reduced, which will in turn affect the uniform distribution of the resin in the fiber fabric. Therefore, the technical solution of the present application not only optimizes the pore structure of the fiber fabric but also improves the infiltration efficiency and infiltration uniformity of the resin in the fiber fabric by precisely selecting the linear density of the fiber, thus providing a key technical guarantee for the preparation of high-performance wave-absorbing prepregs.
[0047] In some alternative embodiments of the present application, the tensile strength is 10 MPa - 50 MPa. Applying an appropriate strength to stretch the fiber can improve the orientation and mechanical properties of the fiber. If the tensile strength is too large, the fiber will break, so it needs to be controlled between 10 MPa and 50 MPa. Combining the above stretching treatment with the twisting treatment can effectively prevent the yarn from loosening during the cyclic infiltration process, thereby improving the fiber load-bearing efficiency.
[0048] In some alternative embodiments of the present application, the absorbent includes at least one of carbon-based absorbents, iron-based absorbents, and dielectric-based absorbents. The mass fraction of the absorbent in the wave-absorbing adhesive film is 50wt% - 90wt%, and the mass fraction of the wave-absorbing adhesive film in the wave-absorbing prepreg is 80wt% - 98wt%. By adding and compounding the absorbent, the present application enables the wave-absorbing prepreg to have good wave-absorbing performance in the characteristic band, expanding the application range of the wave-absorbing prepreg in the field of aircraft.
[0049] In some alternative embodiments of the present application, the resin in the composite wave-absorbing resin includes at least one of epoxy resin, bismaleimide resin, and cyanate ester resin. The resins described in the present application are all thermosetting resins, which are more beneficial to improving the strength and high-temperature resistance of fiber fabrics.
[0050] In some alternative embodiments of the present application, in the cyclic infiltration, the number of times of infiltration with the resin and the composite wave-absorbing resin is 3 to 5 times each, that is, a cyclic mode of resin infiltration, composite wave-absorbing resin infiltration, resin infiltration, and composite wave-absorbing resin infiltration is adopted;
[0051] The temperature of the heat pre-curing is 60°C to 90°C, and the time of the heat pre-curing is 10 min to 30 min.
[0052] Multiple cyclic infiltrations can ensure that the fiber filaments are fully coated to form a multi-layer core-shell structure (the innermost layer is a pure resin reinforcement structure). This structure has a gradient interface, which can relieve thermal stress. The temperature of the heat pre-curing matches the gel point of the epoxy resin and the bismaleimide resin, which can avoid fiber thermal degradation. If the temperature is too high, it may cause resin coking; if the temperature is too low, it may cause incomplete curing.
[0053] In some alternative embodiments of the present application, the composite treatment includes: passing through a pressure roller with a pressure of 20 MPa to 25 MPa to composite the fiber-reinforced fabric with the wave-absorbing adhesive film coated on its surface. The present application uses high-pressure roller pressing (20 MPa to 25 MPa) to enable microscopic interlocking between the adhesive film and the fabric to form a mechanical interlocking structure. If the pressure is less than 20 MPa, the interfacial bonding force will be affected, thereby reducing the peel strength; if the pressure is greater than 25 MPa, the probability of fiber fracture will increase.
[0054] In a second aspect, based on a general inventive concept, the present application also discloses a wave-absorbing prepreg prepared by the above method. The wave-absorbing prepreg of the present application uses the fiber fabric in the middle layer as the structural layer, and the wave-absorbing resins on both sides of the fiber fabric as the functional materials, and significantly improves the permeability of the wave-absorbing resin through the double-sided dipping method.
[0055] The above technical solutions of the present application will be described in detail below with specific embodiments.
[0056] Example 1
[0057] This example provides a method for improving the shear performance of a wave-absorbing prepreg, including the following steps:
[0058] S1: Weigh carbonyl iron and epoxy resin according to a mass ratio of 80:10, and mix them to obtain a composite wave-absorbing resin;
[0059] S2: Twist the aramid fiber with a linear density of 600 dtex and an unfolded width of 500 μm into yarn; stretch the yarn with a force of 10 MPa.
[0060] S3: Then, sequentially infiltrate the stretched yarn with epoxy resin and composite wave-absorbing resin for 4 times each to obtain an infiltrated yarn.
[0061] S4: Heat and pre-cure the infiltrated yarn at 90 °C for 20 min to obtain a pre-treated yarn.
[0062] S5: Weave the pre-treated yarn in a plain weave, that is, take the form of combining 2 warp fibers in the pre-treated yarn into 1 (if not otherwise specified for the warp / weft direction, 1 pre-treated yarn is used for weaving, the same below). As Figure 2 (B) shows, the pore size of the finally obtained aramid cloth is 78300 μm 2 , and the warp breaking strength of the aramid cloth measured according to the GB / T 3923.1 standard (the same below) is 3500 N / 50 mm, and the weft breaking strength is 3200 N / 50 mm.
[0063] S6: Prepare the composite wave-absorbing resin that has not been used for cyclic infiltration into a wave-absorbing adhesive film by double-roll grinding.
[0064] S7: Coat the wave-absorbing adhesive film on both sides of the aramid cloth respectively, and then pass through a pressure roller under a pressure of 20 MPa to compound the aramid cloth with the wave-absorbing adhesive film to obtain a wave-absorbing prepreg. The AL-AL (representing the shear strength when bonding aluminum to aluminum) shear strength of the wave-absorbing prepreg measured according to the GB / T 7124 standard (the same below) is 17.2 MPa.
[0065] Example 2
[0066] This example provides a method for improving the shear performance of a wave-absorbing prepreg, including the following steps:
[0067] S1: Weigh carbonyl iron and epoxy resin according to a mass ratio of 80:10, and then mix them to obtain a composite wave-absorbing resin.
[0068] S2: Twist the aramid fiber with a linear density of 600 dtex and an unfolded width of 380 μm into yarn; stretch the yarn with a force of 10 MPa.
[0069] S3: Then, sequentially infiltrate the stretched yarn with epoxy resin and composite wave-absorbing resin for 4 times each to obtain an infiltrated yarn.
[0070] S4: Heat and pre-cure the infiltrated yarn at 90 °C for 20 min to obtain a pre-treated yarn.
[0071] S5: Weave plain weave with the pretreated yarn, that is, weave in the form of combining the warp fibers and weft fibers in 2 pretreated yarns into 1 each, and the pore size of the finally obtained aramid fabric is 112300 μm 2 , and the measured warp breaking strength of the aramid fabric is 3200 N / 50 mm, and the weft breaking strength is 2900 N / 50 mm.
[0072] S6: Prepare the absorbent wave adhesive film by double-roll grinding the composite absorbent wave resin not used for cyclic infiltration;
[0073] S7: Coat the absorbent wave adhesive film on both sides of the aramid fabric respectively, and then pass through the pressure roller under a pressure of 20 MPa to make the aramid fabric and the absorbent wave adhesive film composite to obtain the absorbent wave prepreg. The measured AL-AL shear strength of the absorbent wave prepreg is 19.6 MPa.
[0074] Example 3
[0075] This example provides a method for improving the shear performance of the absorbent wave prepreg, including the following steps:
[0076] S1: Weigh carbonyl iron and epoxy resin according to a mass ratio of 80:10, and mix them to obtain the composite absorbent wave resin;
[0077] S2: Twist the aramid fiber with a linear density of 600 dtex and an unfolded width of 500 μm into yarn; stretch the yarn with a force of 10 MPa;
[0078] S3: Then infiltrate the stretched yarn with epoxy resin and the composite absorbent wave resin in turn for 4 times each to obtain the infiltrated yarn;
[0079] S4: Heat and pre-cure the infiltrated yarn at 90 °C for 20 min to obtain the pretreated yarn;
[0080] S5: Weave plain weave with the pretreated yarn, that is, weave in the form of combining the warp fibers in 3 pretreated yarns into 1, and the pore size of the finally obtained aramid fabric is 87400 μm 2 , and the measured warp breaking strength of the aramid fabric is 3400 N / 50 mm, and the weft breaking strength is 3300 N / 50 mm.
[0081] S6: Prepare the absorbent wave adhesive film by double-roll grinding the composite absorbent wave resin not used for cyclic infiltration;
[0082] S7: Coat the absorbent wave adhesive film on both sides of the aramid fabric respectively, and then pass through the pressure roller under a pressure of 20 MPa to make the aramid fabric and the absorbent wave adhesive film composite to obtain the absorbent wave prepreg. The measured AL-AL shear strength of the absorbent wave prepreg is 18.6 MPa.
[0083] Example 4
[0084] This embodiment provides a method for improving the shear performance of microwave absorbing prepreg, including the following steps:
[0085] S1: Weigh carbonyl iron and epoxy resin according to a mass ratio of 80:10, and then mix them to obtain a composite microwave absorbing resin;
[0086] S2: Twist aramid fibers with a linear density of 1200 dtex and an unfolded width of 800 μm into yarns; stretch the yarns with a force of 10 MPa;
[0087] S3: Then, sequentially infiltrate the stretched yarns with epoxy resin and the composite microwave absorbing resin 4 times each to obtain infiltrated yarns;
[0088] S4: Heat and pre-cure the infiltrated yarns at 90 °C for 20 min to obtain pre-treated yarns;
[0089] S5: Weave the pre-treated yarns in a plain weave, that is, weave them in a form where the warp and weft fibers in 2 pre-treated yarns are combined into 1 respectively. The pore size of the finally obtained aramid fabric is 57200 μm 2 , and the warp breaking strength of the aramid fabric is measured to be 4600 N / 50 mm, and the weft breaking strength is 4200 N / 50 mm.
[0090] S6: Prepare the microwave absorbing adhesive film by double-roll grinding of the composite microwave absorbing resin that has not been used for cyclic infiltration;
[0091] S7: Coat the microwave absorbing adhesive film on both sides of the aramid fabric respectively, and then pass through a pressure roller under a pressure of 20 MPa to make the aramid fabric and the microwave absorbing adhesive film composite to obtain a microwave absorbing prepreg. The AL-AL shear strength of the microwave absorbing prepreg is measured to be 15.9 MPa.
[0092] Comparative Example 1
[0093] This comparative example provides a method for improving the shear performance of microwave absorbing prepreg, including the following steps:
[0094] S1: Weigh carbonyl iron and epoxy resin according to a mass ratio of 80:10, and then mix them to obtain a composite microwave absorbing resin;
[0095] S2: Twist aramid fibers with a linear density of 600 dtex and an unfolded width of 500 μm into yarns; stretch the yarns with a force of 10 MPa;
[0096] S3: Then, sequentially infiltrate the stretched yarns with epoxy resin and the composite microwave absorbing resin 4 times each to obtain infiltrated yarns;
[0097] S4: Heat and pre-cure the infiltrated yarns at 90 °C for 20 min to obtain pre-treated yarns;
[0098] S5: Use the pretreated yarn for ordinary plain weaving, without using the method of doubling the yarn in both warp and weft directions, as Figure 2 shown in (A), the pore size of the finally obtained aramid fabric is 13200 μm 2 . The warp breaking strength of the measured aramid fabric is 3400 N / 50 mm, and the weft breaking strength is 3100 N / 50 mm.
[0099] S6: Prepare the wave-absorbing adhesive film from the composite wave-absorbing resin not used for cyclic infiltration by double-roll grinding;
[0100] S7: Coat the wave-absorbing adhesive film on both sides of the aramid fabric respectively, and then pass through the pressure roller under a pressure of 20 MPa to make the aramid fabric and the wave-absorbing adhesive film composite to obtain the wave-absorbing prepreg. The measured AL-AL shear strength of the wave-absorbing prepreg is 10.5 MPa.
[0101] Comparative Example 2
[0102] This comparative example provides a method for improving the shear performance of the wave-absorbing prepreg, including the following steps:
[0103] S1: Weigh carbonyl iron and epoxy resin according to a mass ratio of 80:10, and mix them to obtain the composite wave-absorbing resin;
[0104] S2: Twist the aramid fiber with a linear density of 600 dtex and an unfolded width of 500 μm into yarn;
[0105] S3: Weave in plain weave with the yarn, that is, adopt the form of combining the warp fibers in 2 pretreated yarns into 1 for weaving. The pore size of the finally obtained aramid fabric is 76500 μm 2 . The warp breaking strength of the measured aramid fabric is 3000 N / 50 mm, and the weft breaking strength is 2800 N / 50 mm.
[0106] S4: Prepare the wave-absorbing adhesive film from the composite wave-absorbing resin by double-roll grinding;
[0107] S5: Coat the wave-absorbing adhesive film on both sides of the aramid fabric respectively, and then pass through the pressure roller under a pressure of 20 MPa to make the aramid fabric and the wave-absorbing adhesive film composite to obtain the wave-absorbing prepreg. The measured AL-AL shear strength of the wave-absorbing prepreg is 16.3 MPa.
[0108] Comparative Example 3
[0109] This comparative example provides a wave-absorbing adhesive film, which is prepared by the following method:
[0110] Carbonyl iron was added to epoxy resin to obtain an electromagnetic wave absorbing resin with a carbonyl iron content of 70 wt%, and the electromagnetic wave absorbing resin was cured into an electromagnetic wave absorbing adhesive film. The AL-AL shear strength of the electromagnetic wave absorbing adhesive film was measured to be 23.1 MPa.
[0111] Comparative Example 4
[0112] This comparative example provides a method for improving the shear performance of electromagnetic wave absorbing prepreg, including the following steps:
[0113] S1: Carbonyl iron and epoxy resin were weighed according to a mass ratio of 80:10 and then mixed to obtain a composite electromagnetic wave absorbing resin;
[0114] S2: The composite electromagnetic wave absorbing resin was prepared into an electromagnetic wave absorbing adhesive film by two-roll grinding;
[0115] S3: It was measured that the commercially available aramid fabric had no voids, the warp breaking strength was 7200 N / 50 mm, and the weft breaking strength was 6800 N / 50 mm. The electromagnetic wave absorbing adhesive film was coated on both sides of the aramid fabric, and then passed through a pressure roller under a pressure of 20 MPa to make the aramid fabric and the electromagnetic wave absorbing adhesive film composite to obtain an electromagnetic wave absorbing prepreg. The AL-AL shear strength of the electromagnetic wave absorbing prepreg was measured to be 8.4 MPa.
[0116] For the convenience of performance comparison, the processing methods and performance parameters of the electromagnetic wave absorbing materials prepared in Examples 1-4 and Comparative Examples 1-4 are integrated as shown in Table 1:
[0117] Table 1
[0118]
[0119] By comparing Example 1 with Comparative Example 1 in Table 1, it can be seen that in Example 1, the form of combining two warp yarns into one was used for warp knitting, achieving the purpose of regulating the pore size of the fiber fabric; by comparing Example 2 with Example 4, it can be seen that by using different fiber spreading widths, the purpose of regulating the pore size of the fiber fabric can also be achieved, but the fiber spreading width and the range of the pore size of the fiber fabric also have an impact on the final shear performance. For example, although Example 4 used warp knitting, its fiber spreading width was large, resulting in a small fabric pore size, and too small a pore size may affect resin penetration, resulting in poor interfacial bonding and a decrease in shear performance. It shows that among various factors, the size of the fabric pore size is the most important reason affecting the shear performance. By comparing Example 1 with Example 3, it can be seen that different numbers of fibers in the warp knitting process can also affect the pore size of the fiber fabric. Thus, it can be known that in the method for improving the shear performance of the electromagnetic wave absorbing prepreg of the present application, by adjusting the fiber spreading width, the knitting method, and the warp knitting process, the pore size of the fiber fabric can be regulated, so that the electromagnetic wave absorbing resin can more easily penetrate the fiber fabric, further improving the AL-AL shear strength of the electromagnetic wave absorbing prepreg.
[0120] By comparing Example 1 in Table 1 with Comparative Example 2, it can be seen that in the early stage of fiber fabric weaving, the yarn used for weaving in Example 1 was subjected to cyclic impregnation treatment. This treatment method can form a multi-layer core-shell structure on the fiber surface. At the same time, the cyclic impregnation treatment starts with resin as the cycle. Therefore, the pure resin layer is located on the surface of the fiber, which can effectively improve the bonding strength between the fiber fabric and the wave-absorbing resin, thereby avoiding the formation of a weak interface between the fiber and the wave-absorbing resin directly (if the fiber surface is directly combined with the wave-absorbing resin, the absorbent contained in the wave-absorbing resin will reduce the bonding strength), and further improving the shear strength of the wave-absorbing prepreg.
[0121] In Table 1, it can be seen from Example 1 and Comparative Example 3 that the pure wave-absorbing resin has the highest shear strength, which is the result of the strength of the pure resin body without fiber reinforcement. Although the pure resin has high strength, it has no structural load-bearing capacity and will break due to brittleness. In practical applications, due to the lack of fiber-interface synergy, it cannot effectively transfer the load. Through interface-body synergistic enhancement in this application, the failure mode is transformed from interface peeling to resin cohesive failure. Although the strength value is lower than that of the pure resin, the synchronous optimization of wave-absorbing performance and mechanical properties is achieved.
[0122] In Table 1, it can be seen from Example 1 and Comparative Example 4 that when a pure wave-absorbing adhesive film is directly compounded with a commercially available aramid fabric without regulating its pore size, the shear strength of the obtained wave-absorbing prepreg is the lowest, indicating that the regulation of the fabric form, fiber unfolding width, and fabric pore size in this application can all improve the shear performance of the wave-absorbing prepreg.
[0123] Although the specific implementation manners of this application have been described in detail, it should not be construed as a limitation on the protection scope of this application. Within the scope described in the claims, various modifications and deformations that can be made by those skilled in the art without creative efforts still fall within the protection scope of this application.
Claims
1. A method for improving the shear performance of an electromagnetic wave absorbing prepreg, characterized in that, It includes the following steps: Mix the resin and the absorbent in proportion and heat them to melt to obtain a composite wave-absorbing resin; Twist the fiber into yarn, then perform stretching treatment, and use the resin and the composite wave-absorbing resin to infiltrate cyclically. After the infiltration is completed, heat and pre-cure to obtain a pretreated yarn; Perform parallel-yarn weaving treatment on the pretreated yarn to obtain a fiber-reinforced fabric; Prepare a wave-absorbing adhesive film by double-roll grinding of the composite wave-absorbing resin; Coat the wave-absorbing adhesive film on both sides of the fiber-reinforced fabric respectively, and then perform composite treatment to obtain a wave-absorbing prepreg; Among them, the parallel-yarn weaving treatment specifically includes: performing parallel-yarn weaving treatment on the pretreated yarn by combining any 2 to 5 pretreated yarns into 1 yarn. The pretreated yarn includes at least one of the pretreated yarns in the warp direction and the pretreated yarns in the weft direction; The linear density of the fiber is 500 dtex to 7000 dtex, and the unfolded width of the fiber is 10 μm to 1000 μm.
2. The method for improving the shear performance of the microwave absorbing prepreg according to claim 1, wherein The texture of the fiber-reinforced fabric includes at least one of plain weave, twill weave, and satin weave.
3. The method for improving the shear performance of the microwave absorbing prepreg according to claim 1, wherein The fiber includes one or two of glass fiber, quartz fiber, aramid fiber, poly(p-phenylene benzobisoxazole) fiber, and polyimide fiber. The mixing ratio of any two fibers is 50 wt% to 95 wt%.
4. The method for improving the shear performance of the microwave absorbing prepreg according to claim 1, characterized in that The stretching force is 10 MPa to 50 MPa.
5. The method for improving the shear performance of the microwave absorbing prepreg according to claim 1, characterized in that The absorbent includes at least one of carbon-based absorbents, iron-based absorbents, and dielectric absorbents. The mass fraction of the absorbent in the wave-absorbing adhesive film is 50 wt% to 90 wt%, and the mass fraction of the wave-absorbing adhesive film in the wave-absorbing prepreg is 80 wt% to 98 wt%.
6. The method for improving the shear performance of the microwave absorbing prepreg according to claim 1, wherein, The resin includes at least one of epoxy resin, bismaleimide resin, and cyanate resin.
7. The method for improving the shear performance of the microwave absorbing prepreg according to claim 1, characterized in that, In the cyclic infiltration, the number of times of infiltration with the resin and the composite wave-absorbing resin is 3 to 5 times each; The temperature of the heat pre-curing is 60 °C to 90 °C, and the time of the heat pre-curing is 10 min to 30 min.
8. The method for improving the shear performance of the microwave absorbing prepreg according to claim 1, wherein The composite treatment includes: passing through a pressure roller with a pressure of 20 MPa to 25 MPa to make the fiber-reinforced fabric and the wave-absorbing adhesive film coated on its surface be composite.
9. An absorbent wave prepreg, characterized in that, Prepared by the method according to any one of claims 1-8, the shear strength of the wave-absorbing prepreg is 15.5 MPa to 20.0 MPa.