An epoxy resin matrix, prepreg, composite material and method for their production

Abstract

The application discloses an epoxy resin matrix, a prepreg, a composite material and a preparation method thereof, and relates to an epoxy resin matrix which comprises the following raw materials in parts by weight: 40-65 parts by weight of a material containing an epoxy group; 10-20 parts by weight of a first toughening agent; and 7-36 parts by weight of a curing agent; the material containing the epoxy group comprises a mixture of a bifunctional material, a trifunctional material and a tetrafunctional material; and the solubility of the first toughening agent in the material containing the epoxy group is greater than a first preset threshold value. The epoxy resin matrix has the characteristics of a wide curing process window and a holding platform, the composite material prepared by curing the prepreg prepared from the epoxy resin matrix has high impact resistance, high tensile strength, high tensile modulus and high compression modulus, and meets the requirements of the commercial aviation field on the mechanical properties, physical and chemical properties, service life properties and moisture and heat resistance of high-performance composite materials.

Description

Technical Field

[0001] This application relates to the field of composite materials technology, and in particular to an epoxy resin matrix, a prepreg, a composite material, and a method for preparing the same. Background Technology

[0002] Fiber-reinforced resin matrix composites are non-metallic matrix composites with outstanding specific strength and specific modulus, strong designability, and good fatigue and corrosion resistance. Due to their excellent mechanical properties, they have been widely used as high-performance composites in various fields, especially the aerospace industry. With the increasing proportion of composite materials used in aircraft components, improving the impact resistance, tensile and compressive properties of composite materials while simultaneously considering layup processability and service life has become a key research direction for commercial aerospace prepregs. Summary of the Invention

[0003] To address the issue of poor mechanical property stability of prepregs under slow heating conditions, this application provides an epoxy resin matrix, a prepreg, a composite material, and a method for preparing the same. The epoxy resin matrix possesses a wide curing process window and a thermal insulation platform suitable for molding commercial aerospace structural components. It is a high-performance composite material that is compatible with curing regimes of slow to fast heating rates (0.3~3℃ / min) while ensuring stable mechanical properties. Specifically, it exhibits stable impact resistance (compressive strength after impact) within a wide curing window, and also possesses extremely high tensile strength, tensile modulus, and compressive strength.

[0004] According to a first aspect of this application, an epoxy resin matrix is ​​provided, the epoxy resin matrix comprising the following raw materials in parts by weight: 40-65 parts by weight of material containing epoxy groups; 10-20 parts by weight of the first toughening agent; 7-36 parts by weight of curing agent; The materials containing epoxy groups include mixtures of bifunctional materials, trifunctional materials, and tetrafunctional materials; The solubility of the first toughening agent in the material containing epoxy groups is greater than a first preset threshold.

[0005] In some embodiments of this application, the epoxy resin matrix comprises the following raw materials in parts by weight: 50-65 parts by weight of material containing epoxy groups; 14-20 parts by weight of the first toughening agent; Hardener 15-36 parts by weight; The weight ratio of the bifunctional material, trifunctional material and tetrafunctional material is 2.33~3.43:3.00~4.14:1.

[0006] In some embodiments of this application, the weight ratio of the material containing epoxy groups to the first toughening agent is 2.85 to 4.64:1.

[0007] In some embodiments of this application, the epoxy resin matrix further includes: 0-25 parts by weight of the second toughening agent; The solubility of the second toughening agent in the material containing epoxy groups is less than a second preset threshold.

[0008] In some embodiments of this application, the epoxy resin matrix comprises the following raw materials in parts by weight: 40-52 parts by weight of material containing epoxy groups; 10-16 parts by weight of the first toughening agent; 15-28 parts by weight of the second toughening agent; 7-35 parts by weight of curing agent; The weight ratio of the bifunctional material, trifunctional material and tetrafunctional material is 1.15~3.17:1.62~3.83:1.

[0009] In some embodiments of this application, the weight ratio of the epoxy group-containing material, the first toughening agent, and the second toughening agent is 1.54~2.67:0.57~0.80:1.

[0010] According to a second aspect of this application, a prepreg is provided, the prepreg comprising a reinforcing fiber layer and an epoxy resin matrix, the epoxy resin matrix covering the reinforcing fiber layer and filling the gaps within the reinforcing fiber layer; The volume fraction of the reinforcing fiber layer is 55-65% of the volume of the prepreg; The epoxy resin matrix is ​​any of the epoxy resin matrices described above.

[0011] In some embodiments of this application, the epoxy resin matrix includes a first resin matrix and a second resin matrix, wherein the first resin matrix includes any of the epoxy resin matrices described above; and the second resin matrix includes any of the epoxy resin matrices described above. The first resin matrix coats the reinforcing fiber layer and fills the gaps within the reinforcing fiber layer; The second resin matrix coats the first resin matrix.

[0012] According to a third aspect of this application, a composite material is provided, which is formed by curing any of the prepregs described above according to a preset regime.

[0013] According to a fourth aspect of this application, a method for preparing a composite material is provided. The method for preparing the composite material described above includes: The prepreg is cured according to a preset regime to obtain the composite material; the preset regime includes a heat preservation regime and / or a curing regime; The heat preservation system includes: a heat preservation temperature of 130~140℃ and a heat preservation time of 2~4h; or, a heat preservation temperature of 105~115℃ and a heat preservation time of 2~4h. The curing regime includes: a curing temperature of 170~190℃, a curing time of 2~12h, and a heating rate of 0.3~3℃ / min.

[0014] The technical solution provided in this application may include the following beneficial effects: This application, based on the adjustment of the relative proportions of epoxy group-containing materials, a first toughening agent, and a curing agent in an epoxy resin matrix, enables prepreg products prepared from this epoxy resin matrix to adapt to the slow to rapid heating rates (0.3℃ / min to 3℃ / min) required for the molding of aerospace structural components. Under a wide curing window (curing temperature 180±10℃, curing time 2~12h) and a holding plateau regime (135℃±5℃ / 110℃±5℃, holding time 2h~4h), the composite material exhibits stable mechanical properties, especially excellent impact resistance. The epoxy resin matrix of this application provides a high-temperature toughened resin matrix with balanced and excellent performance in terms of material strength, material modulus, impact resistance, hygrothermal properties, and lay-up processability, making it suitable for high-temperature toughened epoxy resin prepregs in the commercial aerospace field.

[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0017] Figure 1 This is a schematic diagram illustrating the structural composition of carbon fiber prepreg prepared by the four-film method according to an exemplary embodiment.

[0018] Figure 2 This is a schematic diagram of a production line for preparing carbon fiber prepreg using a four-film method according to an exemplary embodiment.

[0019] Figure 3 This is an electron microscope image of the carbon fiber prepreg resin in Example 3.

[0020] Figure 4 These are metallographic microscope images of the interlayer of carbon fiber prepreg in Example 3.

[0021] Figure 5 This is a spectrum of dynamic mechanical testing (DMA) of the carbon fiber prepreg in Example 3 after curing at 180℃-2h-2℃ / min. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0023] Currently, research on composite materials primarily focuses on the toughening and modification of epoxy resin matrices. A common method for toughening epoxy resin matrices involves adding thermoplastic toughening particles or toughening agents to thermosetting resins, and then impregnating the resulting resin with reinforcing fibers (such as carbon fiber preforms) to prepare prepregs. Adding thermoplastic resins or thermoplastic particles to the epoxy resin matrix can effectively inhibit crack propagation, thereby improving the impact resistance of the composite material. Therefore, the development of high-performance toughened epoxy resins is a prerequisite for obtaining high-service-temperature, high-toughness carbon fiber composites.

[0024] High-service-temperature and high-toughness carbon fiber composites are mainly used in large-area and large-size structural components such as aircraft wings, mid- and rear fuselages, and vertical tails. These large structural components must be cured and molded in ultra-large autoclaves. Inevitably, there are deviations in curing conditions at different locations inside the large autoclave (the actual measured heating rate of thermocouples at different locations of the tooling varies by 0.3~3℃ / min, the measured curing temperature has a deviation of ±10℃, and the measured curing time may vary by ±2~4 hours). Therefore, in actual aerospace engineering applications, carbon fiber prepregs need a wide curing process molding window, that is, the impact resistance performance must meet the mechanical stability requirements of impact resistance under three working conditions: the longest thermal history (slow heating + high curing temperature + long curing time), the shortest thermal history (rapid heating + low curing temperature + short curing time), the normal thermal history (uniform heating + normal curing temperature + normal curing time), and the thermal insulation platform.

[0025] However, prepregs exhibit material aging issues during the longest thermal history curing process (high curing temperature, slow heating rate, long curing time), leading to a decrease in resin toughness (excessive crosslinking density or altered chain segment structure), which in turn affects their impact resistance (post-impact compressive strength). Therefore, the resistance to slow heating, high-temperature curing, and long-term curing of prepreg resins remains a technical challenge in the development of domestic aerospace carbon fiber prepreg resins. The essence lies in the significant differences in toughness variation of toughening resins under different curing conditions, and there are few reports in related technologies on solutions to overcome the sensitivity of aerospace-grade carbon fiber prepreg resin toughness to the curing regime.

[0026] Furthermore, conventional toughening methods for resins mainly revolve around interlayer toughening particles in prepregs, including the interfacial bonding between toughening particles and resin, the size gradation of toughening particles, and the combination of high-melting-point and low-melting-point toughening particles. The aforementioned technical approaches suffer from the problem of overly complex interlayer toughening designs and excessively high costs (involving various grinding or screening and grading of thermoplastic toughening particles, and particle treatment using chemical or physical methods).

[0027] In related technologies, insufficient attention is paid to the toughness of the resin within the fiber / resin layer. Potential defects may lead to excessive redundancy in the design of interlayer toughness indicators, resulting in a mismatch between the toughness indicators of the resin within the layer and the toughness between the layers, causing economic costs and losses in toughening performance.

[0028] This application provides an epoxy resin matrix comprising the following raw materials in parts by weight: 40-65 parts by weight of a material containing epoxy groups; 10-20 parts by weight of a first toughening agent; and 7-36 parts by weight of a curing agent. The epoxy group-containing material includes a mixture of bifunctional, trifunctional, and tetrafunctional materials. The solubility of the first toughening agent in the epoxy group-containing material is greater than a first preset threshold. By mixing lower-cost bifunctional, trifunctional, and tetrafunctional materials, the cost of epoxy resin raw materials is reduced. Furthermore, this application does not require complex processing or size gradation of the interlayer toughening particles; it only requires adjusting the type of epoxy group-containing material and the relative proportions of the epoxy group-containing material, the first toughening agent, and the curing agent. The composite material prepared from the prepreg of this epoxy resin matrix, after curing, achieves an excellent balance between rigidity and impact resistance, exhibiting high impact resistance, high tensile strength, tensile modulus, and compressive modulus. Furthermore, the epoxy resin matrix of this application has a wide curing process window (suitable for curing temperatures of 180±10℃, curing time compatible with 2~12h, and heating rate compatible with slow to rapid heating processes of 0.3~3℃ / min) and features a heat preservation platform for curing (heat preservation platform 135℃±5℃ / 110℃±5℃, heat preservation time 2h~4h; curing temperature 180±10℃, curing time 2h~12h). Utilizing this epoxy resin matrix, high-temperature and high-toughness epoxy resin prepregs can be obtained at low cost. These prepregs maintain excellent impact strength even during slow heating and long-term high-temperature curing of large aerospace structural components. Simultaneously, the prepregs prepared from the epoxy resin matrix of this application exhibit good layup processability, and their operational and mechanical lifespans meet the stringent requirements of the civil aviation manufacturing industry for carbon fiber prepregs, resulting in good economic benefits.

[0029] The specific embodiments described below are intended to help those skilled in the art understand this embodiment, but this embodiment is not limited to the specific embodiments described below.

[0030] An exemplary embodiment of this application provides an epoxy resin matrix, which comprises the following raw materials in parts by weight: 40-65 parts by weight of material containing epoxy groups; 10-20 parts by weight of the first toughening agent; 7-36 parts by weight of curing agent; Materials containing epoxy groups include mixtures of difunctional, trifunctional, and tetrafunctional materials; The solubility of the first toughening agent in materials containing epoxy groups is greater than a first preset threshold.

[0031] In this embodiment, the epoxy group-containing materials include mixtures of difunctional, trifunctional, and tetrafunctional materials. By mixing the lower-cost difunctional materials with the trifunctional and tetrafunctional materials, the cost of epoxy resin raw materials is reduced. By adjusting the types of epoxy group-containing materials and the relative proportions of the epoxy group-containing materials, the first toughening agent, and the curing agent, a balanced match between the intralayer fracture toughness and interlayer fracture toughness of the fiber / resin layer in the prepreg is achieved. The composite material made from the prepreg prepared from this epoxy resin matrix, after curing, achieves an excellent balance between rigidity and impact resistance, possessing high impact resistance, high tensile strength, tensile modulus, and compressive modulus.

[0032] The first preset threshold refers to the degree of solubility of the first toughening agent in a material containing epoxy groups at a preset preparation temperature. For example, when the first preset threshold is 90%, the solubility of the first toughening agent in a material containing epoxy groups is greater than 90%. Therefore, the solubility of the first toughening agent in a material containing epoxy groups can be 92%, 95%, or 100%, indicating that the first toughening agent has good solubility in a material containing epoxy groups at the preset preparation temperature.

[0033] For example, the preparation temperature of the epoxy resin matrix is ​​140~170℃, the first preset threshold is 95%, the solubility of the first toughening agent in the material containing epoxy groups is greater than 95%, and the solubility of the first toughening agent in the material containing epoxy groups can be 100%. During the preparation of the epoxy resin matrix, the system temperature is heated to 140~170℃, the first toughening agent is added to the material containing epoxy groups, and the solubility of the first toughening agent in the material containing epoxy groups is 100%, that is, the first toughening agent can be fully dissolved in the material containing epoxy groups.

[0034] The epoxy resin matrix has a significant impact on the layup processability of prepregs. Prepregs are made by impregnating reinforcing fibers into an epoxy resin matrix. The layup processability of prepregs refers to the ease and quality of laying them onto the mold surface manually or using automated equipment during the fabrication of composite components. Process indicators for prepreg layup processability include the inter-sheet tack in the quantitative tack ratio; for example, the inter-sheet tack needs to meet a requirement of 18~20N.

[0035] This application proposes a theory that the viscosity of the resin matrix affects the surface tack of the prepreg, specifically demonstrating an inverse relationship between the viscosity of the epoxy resin matrix and the surface tack of the prepreg. The surface tack of the prepreg is characterized by quantitative testing of the adhesion between the prepreg and the steel sheet (mold) and between the prepreg and the prepreg itself. In this application, the viscosity level of the resin matrix is ​​increased by optimizing the proportions of the epoxy resin matrix raw materials. Optimization directions include: reducing the proportion of low-viscosity monomer resins, increasing the proportion of high-viscosity monomer resins, and increasing the proportion of the first toughening agent dissolved in the resin, thereby meeting the layup process index of 18-20N inter-sheet tack in quantitative tack testing.

[0036] The layability of prepreg is also related to its stiffness. This application also proposes a theory that the impregnation level of the prepreg affects its stiffness, specifically, the higher the impregnation level, the higher the stiffness. The impregnation level is characterized by the water absorption of the prepreg, and the stiffness is characterized by testing the drape of the prepreg. In this application, the impregnation level of the prepreg is maintained in the range of 40~75mg to meet the layability index of 240~280mm stiffness of the prepreg.

[0037] In summary, through the rational design of the amount of epoxy group-containing materials, the first toughening agent, the curing agent, and the proportion of each component of the epoxy group-containing materials in the epoxy resin matrix of this application, the prepreg prepared from the resin matrix of this application has excellent mechanical property stability within a wide curing process window, good lay-up processability under ambient temperature of 18~26℃ and humidity of 45~65%RH, and is suitable for the production of masterbatch for hand-laying, tape-laying, and wire-laying materials. It can be used in hand-laying and machine-laying scenarios for tooling of planar and curved aerospace structural parts.

[0038] In one embodiment, an epoxy resin matrix is ​​provided, comprising the following raw materials in parts by weight: 40 parts by weight of material containing epoxy groups; 10 parts by weight of the first toughening agent; 7 parts by weight of curing agent; Materials containing epoxy groups include mixtures of difunctional, trifunctional, and tetrafunctional materials; The solubility of the first toughening agent in materials containing epoxy groups is greater than a first preset threshold.

[0039] In another embodiment, an epoxy resin matrix comprises the following raw materials in parts by weight: 55 parts by weight of material containing epoxy groups; 15 parts by weight of the first toughening agent; 20 parts by weight of curing agent; Materials containing epoxy groups include mixtures of difunctional, trifunctional, and tetrafunctional materials; The solubility of the first toughening agent in materials containing epoxy groups is greater than a first preset threshold.

[0040] In another embodiment, an epoxy resin matrix comprises the following raw materials in parts by weight: 65 parts by weight of material containing epoxy groups; 20 parts by weight of the first toughening agent; 36 parts by weight of curing agent; Materials containing epoxy groups include mixtures of difunctional, trifunctional, and tetrafunctional materials; The solubility of the first toughening agent in materials containing epoxy groups is greater than a first preset threshold.

[0041] Bifunctional materials include epoxy resin monomers or polymers containing two epoxy groups. By having lower viscosity, bifunctional materials can improve the lay-up processability of prepregs prepared from epoxy resin matrices. For example, bifunctional materials include one or more mixtures of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol A epoxy resin, and bisphenol S diglycidyl ether. For example, Epon 828 resin can be selected as the bisphenol A epoxy resin, which has a low molecular weight. Bisphenol F diglycidyl ether, model DER351, can be selected as the bifunctional material, purchased from DOW Resins Ltd. Bifunctional materials can also be selected as mixtures of various of the above materials; for example, the bifunctional material can be bisphenol F diglycidyl ether and bisphenol A diglycidyl ether in a weight ratio of 1.35-2.48:1.

[0042] Trifunctional materials include epoxy resin monomers or polymers containing three epoxy groups. Compared to difunctional materials, trifunctional materials have better mechanical properties and heat resistance, but their viscosity is slightly higher. For example, trifunctional materials include one or more mixtures of triglycidylaminophenol, phenol-phenolic epoxy resin, aromatic epoxy resin, and acetaminophen-based trifunctional epoxy resin. For instance, acetaminophen-based trifunctional epoxy resin, model JD939, purchased from Hunan Jiashengde Co., Ltd., can be selected as a trifunctional material. Alternatively, a mixture of multiple materials can be selected; for example, a trifunctional material can be acetaminophen-based trifunctional epoxy resin and triglycidylaminophenol in a weight ratio of 1.00~1.85:1.

[0043] Tetrafunctional materials include epoxy resin monomers or polymers containing four epoxy groups. Compared to difunctional materials, tetrafunctional materials have better mechanical properties and heat resistance, but their viscosity is higher. For example, tetrafunctional materials include one or more mixtures of tetraglycidyl diaminodiphenylmethane, tetrafunctional diphenylamine epoxy resin, and dicyclopentadiene epoxy resin. For instance, tetraglycidyl diaminodiphenylmethane, model AG80, can be purchased from Yongcheng Chemical Co., Ltd. Tetrafunctional materials can also be mixtures of multiple materials mentioned above; for example, a tetrafunctional material can be a dicyclopentadiene epoxy resin and a tetrafunctional diphenylamine epoxy resin in a weight ratio of 2.25~3.08:1.

[0044] The first toughening agent can be a material with high solubility in materials containing epoxy groups. For example, the first toughening agent includes one or more of polysulfone (PS), polyethersulfone (PES), and polyphenylene ether (PPO). For example, the first toughening agent can be polyethersulfone, specifically model 4100P-PES, purchased from Sumitomo Chemical. The first toughening agent can also be a mixture of multiple materials mentioned above; for example, the first toughening agent can be polyethersulfone and polyphenylene ether in a weight ratio of 1.78 to 3.18:1.

[0045] The average particle size (D50) of the first toughening agent is less than or equal to 1000µm. For example, the first toughening agent can be polyethersulfone with an average particle size (D50) of 400~900µm. The larger particle size of polyethersulfone can effectively reduce the flow properties of prepregs prepared from epoxy resin matrix and reduce the thickness deviation of aerospace structural parts.

[0046] The curing agent includes one or more of diaminodiphenylmethane, diaminodiphenyl sulfone, diethyltoluenediamine, and dicyandiamide. For example, 4,4'-Diaminodiphenylsulfone (DDS), specifically 4-4'DDS® 1449, can be selected as the curing agent and is available from Hansort Ltd. Choosing the less reactive 4-4'DDS is beneficial for achieving the external life requirements of aerospace prepregs, including an operational life of over 240 hours and a mechanical life of over 720 hours.

[0047] Among them, the curing agent can be, for example, diaminodiphenyl sulfone with an average particle size (D50) of 5~15µm. The curing agent particles with small particle size have a larger specific surface area, which can effectively improve the crosslinking density of carbon fiber composites and improve their heat resistance.

[0048] In one exemplary embodiment, the epoxy resin matrix comprises the following raw materials in parts by weight: 50-65 parts by weight of material containing epoxy groups; 14-20 parts by weight of the first toughening agent; Hardener 15-36 parts by weight; The weight ratio of difunctional, trifunctional, and tetrafunctional materials is 2.33~3.43:3.00~4.14:1.

[0049] In this embodiment, the mechanical and processing properties of the epoxy resin matrix are improved by further optimizing the dosage of the epoxy group-containing material, the first toughening agent, the curing agent, and the weight ratio of the difunctional, trifunctional, and tetrafunctional materials.

[0050] In one embodiment, for example, the epoxy resin matrix comprises the following raw materials in parts by weight: 50 parts by weight of material containing epoxy groups; 14 parts by weight of the first toughening agent; 15 parts by weight of curing agent; The weight ratio of the difunctional, trifunctional, and tetrafunctional materials is 2.33:3.00:1.

[0051] In another embodiment, the epoxy resin matrix comprises the following raw materials in parts by weight: 58 parts by weight of material containing epoxy groups; 17 parts by weight of the first toughening agent; 26 parts by weight of curing agent; The weight ratio of the difunctional, trifunctional, and tetrafunctional materials is 2.68:3.54:1.

[0052] In another embodiment, the epoxy resin matrix comprises the following raw materials in parts by weight: 65 parts by weight of material containing epoxy groups; 20 parts by weight of the first toughening agent; 36 parts by weight of curing agent.

[0053] The weight ratio of the difunctional, trifunctional, and tetrafunctional materials is 3.43:4.14:1.

[0054] In one exemplary embodiment, the weight ratio of the material containing epoxy groups to the first toughening agent is 2.85 to 4.64:1.

[0055] In this embodiment, by controlling the weight ratio of the material containing epoxy groups to the first toughening agent, the epoxy resin matrix can possess both good mechanical strength, toughness, and processability.

[0056] For example, the weight ratio of the epoxy group-containing material to the first toughening agent can be 2.85:1, 3.19:1, 3.48:1, 4.05:1, or 4.64:1. The weight ratio of the epoxy group-containing material to the first toughening agent can also be any value between the exemplary weight ratios; for example, the weight ratio of the epoxy group-containing material to the first toughening agent can also be any value between 3.19 and 4.05:1.

[0057] In one exemplary embodiment, the epoxy resin matrix further includes: 0-25 parts by weight of the second toughening agent; The solubility of the second toughening agent in materials containing epoxy groups is less than a second preset threshold.

[0058] In this embodiment, the epoxy resin matrix may further include a second toughening agent. The second preset threshold refers to the degree of solubility of the second toughening agent in the material containing epoxy groups at a preset preparation temperature. For example, when the second preset threshold is 10%, the solubility of the second toughening agent in the material containing epoxy groups is less than 10%. Therefore, the solubility of the second toughening agent in the material containing epoxy groups can be 0%, 3%, or 5%, indicating that the second toughening agent has poor solubility in the material containing epoxy groups at the preset preparation temperature, and the second toughening agent is difficult to dissolve in the material containing epoxy groups.

[0059] For example, the preparation temperature of the epoxy resin matrix is ​​140~170℃, the second preset threshold is 5%, the solubility of the second toughening agent in the material containing epoxy groups is less than 5%, and the solubility of the second toughening agent in the material containing epoxy groups can be 0%. During the preparation of the epoxy resin matrix, the system temperature is heated to 140~170℃, the second toughening agent is added to the material containing epoxy groups, and the solubility of the second toughening agent in the material containing epoxy groups is 0%, meaning the first toughening agent cannot dissolve in the material containing epoxy groups.

[0060] The second toughening agent can be selected from materials with low solubility in materials containing epoxy groups. For example, the second toughening agent includes one or more of polyphthalamide, polyetherimide, and polyamide. The second toughening agent can be, for example, polyamide, model A170, from Zhongfu Shenying Co., Ltd. The second toughening agent can also be a mixture of multiple materials mentioned above; for example, the second toughening agent can be polyamide and polyphthalamide in a weight ratio of 1.23~2.26:1.

[0061] The average particle size (D50) of the second toughening agent is less than or equal to 100µm. For example, the second toughening agent can be a polyamide with an average particle size (D50) of 5~20µm. The small particle size of the polyamide particles can increase the contact area between the polyamide and the resin matrix, and exhibit stronger crack resistance in the impact test.

[0062] In one exemplary embodiment, the epoxy resin matrix comprises the following raw materials in parts by weight: 40-52 parts by weight of material containing epoxy groups; 10-16 parts by weight of the first toughening agent; 15-28 parts by weight of the second toughening agent; 7-35 parts by weight of curing agent; The weight ratio of difunctional, trifunctional, and tetrafunctional materials is 1.15~3.17:1.62~3.83:1.

[0063] In this embodiment, by adjusting the amounts of materials containing epoxy groups, the first toughening agent, the second toughening agent, and the curing agent, as well as the weight ratios of difunctional, trifunctional, and tetrafunctional materials, the mechanical strength, toughness, and processing performance of the epoxy resin matrix are further improved.

[0064] In one embodiment, for example, the epoxy resin matrix comprises the following raw materials in parts by weight: 40 parts by weight of material containing epoxy groups; 10 parts by weight of the first toughening agent; 15 parts by weight of the second toughening agent; 7 parts by weight of curing agent; The weight ratio of the difunctional, trifunctional, and tetrafunctional materials is 1.15:1.62:1.

[0065] In another embodiment, the epoxy resin matrix comprises the following raw materials in parts by weight: 46 parts by weight of material containing epoxy groups; 14 parts by weight of the first toughening agent; 20 parts by weight of the second toughening agent; 20 parts by weight of curing agent; The weight ratio of the bifunctional material, trifunctional material and tetrafunctional material is 2.65:2.98:1.

[0066] In another embodiment, the epoxy resin matrix comprises the following raw materials in parts by weight: 52 parts by weight of material containing epoxy groups; 16 parts by weight of the first toughening agent; 28 parts by weight of the second toughening agent; 35 parts by weight of curing agent; The weight ratio of the difunctional, trifunctional, and tetrafunctional materials is 3.17:3.83:1.

[0067] In an exemplary embodiment, the weight ratio of the material containing epoxy groups, the first toughening agent, and the second toughening agent is 1.54~2.67:0.57~0.80:1.

[0068] In this embodiment, the mechanical strength, toughness, and processing performance of the epoxy resin matrix are further improved by controlling the weight ratio of the material containing epoxy groups, the first toughening agent, and the second toughening agent.

[0069] For example, the weight ratio of the epoxy-containing material, the first toughening agent, and the second toughening agent can be 1.54:0.57:1, 1.88:0.67:1, 2.12:0.70:1, 2.32:0.75:1, or 2.67:0.80:1. The weight ratio of the epoxy-containing material, the first toughening agent, and the second toughening agent can also be any ratio between these exemplary weight ratios; for example, the weight ratio of the epoxy-containing material, the first toughening agent, and the second toughening agent can be any ratio between 1.88 and 2.32:0.67 and 0.75:1.

[0070] An exemplary embodiment of this application provides a prepreg comprising a reinforcing fiber layer and an epoxy resin matrix, wherein the epoxy resin matrix covers the reinforcing fiber layer and fills the gaps within the reinforcing fiber layer; The volume fraction of the reinforcing fiber layer is 55-68% of the prepreg volume; The epoxy resin matrix is ​​the epoxy resin matrix of any of the above embodiments.

[0071] In this embodiment, a prepreg is obtained by impregnating the epoxy resin matrix with a reinforcing fiber layer as described in the above embodiment. The volume fraction of the reinforcing fiber layer can be 55%, 58%, 61%, 63%, 65%, or 68% of the prepreg volume. The volume fraction of the reinforcing fiber layer can also be any of the above-mentioned volume percentages; for example, the volume fraction of the reinforcing fiber layer can be 58-63% of the prepreg volume. The reinforcing fiber layer includes a carbon fiber layer, a glass fiber layer, an aramid fiber layer, etc.

[0072] For example, the reinforcing fiber layer may have an areal density of 184~194 g / m². 2The carbon fiber layer can be made of high-strength, medium-modulus carbon fiber with a tensile modulus of at least 280 GPa, a tensile strength of at least 5.8 GPa, and an elongation of at least 1.7%. The single fiber fineness can be 0.4–1.5 dtex. If the single fiber fineness is less than 0.4 dtex, the carbon fiber bundle is easily damaged during twisting due to contact with the guide roller. If the single fiber fineness exceeds 1.5 dtex, the resin may not be able to fully penetrate the carbon fiber layer, leading to a decrease in the product's mechanical properties. For example, the carbon fiber can be SYT-59G carbon fiber from Zhongfu Shenying Co., Ltd. The carbon fiber should have a fiber areal density of 184–194 g / m³. 2 The fibers are arranged unidirectionally according to specifications, and the yarn unfolding adopts 120℃ infrared heating and vibration unfolding mode to make the fibers neatly arranged and without gaps, resulting in a unidirectional carbon fiber layer.

[0073] In an exemplary embodiment, the epoxy resin matrix includes a first resin matrix and a second resin matrix, wherein the first resin matrix includes the epoxy resin matrix as described in any of the above embodiments; and the second resin matrix includes the epoxy resin matrix as described in any of the above embodiments. The first resin matrix coats the reinforcing fiber layer and fills the gaps within the reinforcing fiber layer; The second resin matrix coats the first resin matrix.

[0074] In this embodiment, the epoxy resin matrix includes a first resin matrix and a second resin matrix. An inner film is formed through the first resin matrix to impregnate the reinforcing fiber layer, thereby obtaining a prepreg intermediate. An outer film is formed through the second resin matrix to impregnate the prepreg intermediate, thereby obtaining a prepreg.

[0075] The first resin matrix comprises the following raw materials in parts by weight: 50-65 parts by weight of material containing epoxy groups; 14-20 parts by weight of the first toughening agent; Hardener 15-36 parts by weight; The weight ratio of the bifunctional material, trifunctional material and tetrafunctional material is 2.33~3.43:3.00~4.14:1.

[0076] The second resin matrix comprises the following raw materials in parts by weight: 40-52 parts by weight of material containing epoxy groups; 10-16 parts by weight of the first toughening agent; 15-25 parts by weight of the second toughening agent; 7-35 parts by weight of curing agent; The weight ratio of the bifunctional material, trifunctional material and tetrafunctional material is 1.15~3.17:1.62~3.83:1.

[0077] In this embodiment, a four-film impregnation method is used, namely, an inner layer film is prepared using a first resin matrix, and an outer layer film is prepared using a second resin matrix, to impregnate the carbon fiber layer. The outer layer film contains a second toughening agent that is insoluble in the resin. See schematic diagram below. Figure 1 , Figure 1 The meanings of the markings are as follows: 1J - Inner layer adhesive film; 2J - Outer layer adhesive film; 1C - Carbon fiber layer; Figure 1 The "arrows" indicate that the inner and outer adhesive films are impregnated into the carbon fiber layer under preset impregnation temperature and pressure. The carbon fiber prepreg prepared using the four-film method can restrict the entry of the second toughening agent toughening particles into the carbon fiber layer, resulting in a fiber-reinforced composite material with excellent and stable post-impact compressive strength, tensile strength, and tensile modulus.

[0078] The inner layer film can be prepared by the following method: The first resin matrix is ​​placed into the glue tank of a coating machine for preparing dry prepreg film. The temperature of the glue roller and the glue tank is controlled at 65~75℃, and preheating is performed for 30~60 minutes to soften the first resin matrix. Then, the glue roller speed is set to 5~15 rpm, and the gap between the glue rollers is adjusted according to the film weight design. In the carbon fiber prepreg manufacturing of this application, the gap between the glue rollers is set to 10~100 micrometers. The softened first resin matrix is ​​then coated onto release paper using a coating machine to form the inner layer film.

[0079] The outer film can be prepared by the following method: The matrix resin is placed in the glue tank of a coating machine for preparing dry prepreg films. The temperature of the glue rollers and the glue tank is set to 75±5℃, and preheating is performed for 60~90 minutes to soften the second resin matrix. Then, the glue roller speed is set to 5~15 rpm, and the gap between the glue rollers is adjusted according to the film basis weight design. In the carbon fiber prepreg manufacturing of this application, the gap between the glue rollers is set to 10~100 micrometers. The softened second resin matrix is ​​coated onto release paper using a coating machine to form the outer film.

[0080] The basis weight of the inner film is 25~35 g / m². 2 For example, the basis weight of the inner film can be 25 g / m². 2 28 g / m 2 30g / m 2 35 g / m 2 The outer film weight is 15~25 g / m². 2 For example, the basis weight of the outer film can be 15 g / m². 2 18 g / m 2 20g / m 2 25 g / m 2 The ratio of the basis weight of the inner film to that of the outer film can be 1.00 to 1.67:1.

[0081] An exemplary embodiment of this application provides a dry impregnation method for prepreg: i) Check the basis weight of the film. The first resin matrix is ​​coated to a basis weight of 25±2g / m³. 2 The inner layer of the adhesive film is coated with the second resin matrix to form a film with a basis weight of 25±2g / m². 2 The outer film.

[0082] ii) Prepare SYT-59G carbon fiber according to a fiber areal density of 184~194 g / m 2 The fibers are arranged unidirectionally according to specifications, and the yarn unfolding adopts 120℃ infrared heating and vibration unfolding mode to make the fibers neatly arranged and without gaps, resulting in a unidirectional carbon fiber layer.

[0083] iii) such as Figure 2 As shown in the diagram, the meanings of each mark are as follows: 1J - Inner layer adhesive film; 2J - Outer layer adhesive film; 1G - ① Hot roller; 1B - ① Hot plate; 2G - ② Hot roller; 2B - ② Hot plate; 3G - ③ Hot roller; 3B - ③ Hot plate; 4G - ④ Hot roller; 4B - ④ Cold plate; 5G - ⑤ Hot roller; 5B - ⑤ Hot plate; 6G - ⑥ Hot roller; 6B - ⑥ Cold plate; 7B - ⑦ Cold plate; 7G - Traction take-up roller.

[0084] The inner layer adhesive film is applied to the unidirectionally arranged carbon fiber layer from both the top and bottom. The temperature of the hot press rollers ①~④ is adjusted to 100℃, and the recommended temperature of the hot plates ①~③ is set to 95±5℃. The pressure of the impregnation rollers ①~④ is 500±100kg, and the impregnation line speed is 5~10m / min, so that the inner layer adhesive film fully impregnates the carbon fiber layer and obtains the prepreg intermediate. Then, the outer layer adhesive film is attached to the prepreg intermediate from both the top and bottom. The temperature of the hot press rollers ⑤~⑥ is adjusted to 110±5℃, the temperature of the hot plate ⑤ is set to 105±5℃, the pressure of the impregnation rollers ⑤~⑥ is 350±50kg, and the impregnation line speed is 5~10m / min, to obtain the finished carbon fiber prepreg.

[0085] After obtaining the carbon fiber prepreg, it can be cured in an autoclave to prepare carbon fiber composite materials. The autoclave curing temperature range is 180±10℃, the curing time is 120min~720min, and the curing pressure is 0.5~0.7MPa. The heating rate can be set from 0.3℃ / min to 3℃ / min depending on the autoclave's heating capacity and the size of the structural component being prepared.

[0086] An exemplary embodiment of this application provides a composite material, which is formed by curing the prepreg of any of the above embodiments according to a preset regime.

[0087] The composite material formed by curing the carbon fiber prepreg of this application can be used for main load-bearing aerospace structural components (horizontal tail, vertical tail, winglets, fuselage, panels, etc.) and non-main load-bearing structural components. In other high-performance composite material applications, such as shipbuilding, rail transportation, automobiles, and drones, the composite material involved in this application, due to its excellent tensile, compressive, interlaminar fracture toughness and impact resistance, is sufficient to cover the aforementioned application areas.

[0088] An exemplary embodiment of this application provides a method for preparing a composite material. The method for preparing the composite material is as described above. The preparation method includes: The prepreg is cured according to a preset regime to obtain a composite material; the preset regime includes a thermal insulation regime and / or a curing regime. The heat preservation system includes: heat preservation temperature of 130~140℃ and heat preservation time of 2~4h; or, heat preservation temperature of 105~115℃ and heat preservation time of 2~4h. The curing regime includes: a curing temperature of 170~190℃, a curing time of 2~12h, and a heating rate of 0.3~3℃ / min.

[0089] The epoxy resin matrix of this application has a wide curing process window (suitable for curing temperatures of 180±10℃, curing time compatible with 2~12h, and heating rate compatible with slow to rapid heating processes of 0.3~3℃ / min) and features a heat preservation platform for curing (heat preservation platform 135℃±5℃ / 110℃±5℃, heat preservation time 2h~4h; curing temperature 180±10℃, curing time 2h~12h). Utilizing this epoxy resin matrix, high-temperature and high-toughness epoxy resin prepregs can be obtained at low cost. These prepregs maintain excellent impact strength even during slow heating and long-term high-temperature curing of large aerospace structural components. Furthermore, the prepregs of this application exhibit good layup processability, and their operational and mechanical lifespans meet the stringent requirements of the civil aviation manufacturing industry for carbon fiber prepregs, resulting in good economic benefits.

[0090] To more clearly explain the technical solution of this application, specific embodiments of the epoxy resin matrix are provided. The beneficial effects of selecting the above-mentioned range of component contents will be explained through specific experimental data provided in the specific embodiments.

[0091] Example It should be noted that, unless otherwise specified, all raw materials used in the following embodiments are commercially available. The reinforcing fiber used is SYT-59G carbon fiber.

[0092] Example 1: A prepreg is prepared using the following method: (1) Preparation of the first resin matrix: 21 parts by weight of bisphenol F diglycidyl ether, 27 parts by weight of trifunctional glycidyl ether, 9 parts by weight of tetraglycidyl diaminodiphenylmethane, and 20 parts by weight of polyethersulfone were placed in a reactor, heated to 150°C, stirred at 60 rpm, and dispersed at 500 rpm for 60 min to completely dissolve the polyethersulfone. After dissolution, the reactor was cooled to 60°C and stabilized for 5 min. Diaminodiphenyl sulfone was then added and stirred at 30 rpm for 40 min. Vacuum degassing mode was then activated to obtain the first resin matrix.

[0093] (2) Preparation of the second resin matrix: 15 parts by weight of bisphenol F diglycidyl ether, 21 parts by weight of trifunctional glycidyl ether, 13 parts by weight of tetraglycidyl diaminodiphenylmethane, and 15 parts by weight of polyethersulfone were placed in a reactor, heated to 150°C, stirred at 60 rpm, and dispersed at 500 rpm for 60 min to completely dissolve the polyethersulfone. After dissolution, the reactor was cooled to 80°C and stabilized for 5 min. Polydodecanoic acid was added and stirred at 30 rpm for 40 min. The temperature was then lowered to 60°C and stabilized for 5 min. Diaminodiphenyl sulfone was added and stirred at 30 rpm for 40 min. Vacuum degassing mode was activated to obtain the second resin matrix.

[0094] (3) Preparation of the adhesive film; the first resin matrix is ​​coated to form a film with a basis weight of 25 g / m 2 The inner layer of the adhesive film forms a second resin matrix coating with a basis weight of 25 g / m². 2 The outer film.

[0095] (4) Impregnation treatment: The inner layer of the film is impregnated with a basis weight of 188 g / m 2 The upper and lower surfaces of the carbon fiber layer are used to obtain a prepreg intermediate; the outer film is impregnated into the upper and lower surfaces of the prepreg intermediate to obtain the prepreg. In the prepreg, the weight of the resin matrix (the sum of the first resin matrix and the second resin matrix) accounts for 33% of the total weight of the prepreg.

[0096] To more clearly explain the technical solution of this application, this application also provides examples 2 to 10 of the prepreg, wherein the formulations of examples 2 to 10 are shown in Table 1.

[0097] Table 1 shows specific embodiments of the prepreg in this application. It should be noted that, except for the parameters listed in Table 1, the other parameters of Embodiments 2-10 are basically the same as those of Embodiment 1.

[0098] In Table 1, the ratio C1 represents the weight ratio of difunctional, trifunctional, and tetrafunctional materials in the first resin matrix. The ratio C2 is the weight ratio of the material containing epoxy groups to the first toughening agent in the first resin matrix; The ratio C3 is the weight ratio of difunctional, trifunctional, and tetrafunctional materials in the second resin matrix; The ratio C4 is the weight ratio of the material containing epoxy groups, the first toughening agent, and the second toughening agent in the second resin matrix.

[0099] Table 1. Formulation of prepregs in the embodiments (unit: parts by weight)

[0100] Table 1. Formulation of prepregs in the embodiments (unit: parts by weight)

[0101] Comparative Example Comparative Example 1: The main difference between this comparative example and Example 1 is that the raw material formulations of the first resin matrix and the second resin matrix are different. In Comparative Example 1, the first resin matrix comprises: 18 parts by weight of bisphenol A diglycidyl ether; 7 parts by weight of bisphenol F diglycidyl ether; 36 parts by weight of tetraglycidyl diaminodiphenylmethane; 12 parts by weight of polyethersulfone; and 27 parts by weight of diaminodiphenyl sulfone. The weight ratio (C2) of the material containing epoxy groups in the first resin matrix to the first toughening agent is 5.08:1. The second resin matrix comprises: 13 parts by weight of bisphenol A diglycidyl ether; 5 parts by weight of bisphenol F diglycidyl ether; 27 parts by weight of tetraglycidyl diaminodiphenylmethane; 10 parts by weight of polyethersulfone; 25 parts by weight of polydodecyl lactam; and 20 parts by weight of diaminodiphenyl sulfone; wherein the weight ratio (C4) of the material containing epoxy groups in the second resin matrix, the first toughening agent, and the second toughening agent is 1.80:0.40:1.

[0102] Performance testing The performance of the prepregs in the examples and comparative examples was tested according to the following method, and the test results are recorded in Tables 2-6.

[0103] 1. Mechanical property testing (standard curing regime): Prepregs were cured in autoclaves at 180℃ for 2 hours under standard curing conditions (heating rate set at 2~3℃ / min) to obtain composite laminates for mechanical testing. The tensile strength, tensile modulus, compressive strength and impact strength (post-impact compressive strength) of the composite laminates under standard curing conditions were tested.

[0104] Tensile strength and tensile modulus tests were conducted based on ASTM D 3039, with fibers laid in 6-8 layers at 0° and tested at room temperature. Tensile modulus was obtained using an extensometer with a 50mm gauge length. Compressive strength tests were conducted based on SACMA SRM1, with fibers laid in 6-8 layers at 0° and tested at room temperature. The compressive strength standard sample had a working length of 10mm, and 2mm thick carbon fiber laminate reinforcement sheets were required at both clamping ends. Impact compressive strength was tested using ASTM D 7136 & 7137 as reference standards, with fibers in the range of [45 / 0 / -45 / 90]. 3s The samples were laid out and their impact resistance was tested at room temperature (the impact energy of each sample was uniformly set at 30J).

[0105] 2. Wide curing process window test: Laminate samples were prepared using prepregs under the longest and shortest heat history curing regimes, respectively, and based on ASTM D 7136 & 7137 as reference standards, with fibers in the range of [45 / 0 / -45 / 90]. 3s The samples were laid out and their impact resistance was tested at room temperature (the impact energy of each sample was uniformly set at 30J).

[0106] The longest thermal history curing regime was the slow-heating, high-temperature, long-time curing regime (190℃-8h, 0.3℃ / min); the shortest thermal history curing regime was the rapid-heating, low-temperature, short-time curing regime (170℃-2h, 3℃ / min).

[0107] 3. Insulation platform system test: Prepreg was cured on an insulated platform and laminate samples were prepared, based on ASTM D 7136 & 7137 standards, with fibers in the range of [45 / 0 / -45 / 90]. 3s The samples were laid out and their impact resistance was tested at room temperature (the impact energy of all samples was uniformly set at 30J). The first curing regime for the insulation platform was: 135℃ for 3 hours, followed by curing at 190℃ for 6 hours, with a heating rate of 1.5℃ / min. The second curing regime for the insulation platform was: 110℃ for 4 hours, followed by curing at 190℃ for 12 hours, with a heating rate of 2.5℃ / min.

[0108] 4. Processing performance test: The operational life and mechanical life of the prepreg were tested separately.

[0109] The quantitative viscosity of the prepreg during its service life was tested according to ASTM D 8336; the impregnation degree of the prepreg was tested using the water absorption method; the stiffness of the prepreg was tested using the overhang distance; the short beam shear strength (interlaminar shear) of the prepreg at room temperature under mechanical life conditions was tested according to ASTM D 2344; and the glass transition temperature Tg after curing under the standard curing regime (180℃-2h, 2~3℃ / min) was tested according to ASTM D 7028.

[0110] 5. Moisture and heat resistance test: Under the standard curing regime (180℃-2h, 2~3℃ / min), the machined composite material specimens were boiled in a water bath at 71℃ for 14 days. The short beam shear strength (interlaminar shear) was tested according to ASTM D 2344 standard, and the impact compressive strength was tested with ASTM D 7136 & 7137 as reference standards.

[0111] Table 2. Mechanical property test results of laminates prepared from the prepregs of the examples and comparative examples under standard curing regimes.

[0112] As can be seen from Tables 1 and 2, compared to Comparative Example 1, the laminate prepared from the prepreg of this application exhibits superior tensile strength, tensile modulus, compressive strength, and post-impact compressive strength under standard curing conditions. As demonstrated in Examples 1-10, adjusting the proportions of components such as materials containing epoxy groups and toughening agents (first toughening agent and second toughening agent) can improve the tensile strength and impact resistance of the material, especially significantly enhancing the post-impact compressive strength.

[0113] Table 3. Post-impact compressive strength of laminates prepared from the prepregs of the examples and comparative examples within the curing window.

[0114] As can be seen from the data in Tables 1 and 3, the embodiments of this application can improve the compressive strength after impact testing of boards prepared under different curing regimes within the curing window by adjusting the proportions of components such as materials containing epoxy groups and toughening components (first toughening agent and second toughening agent).

[0115] Compared to the standard curing regime, the laminate prepared from the prepreg of this application exhibits a less than 10% decrease in compressive strength after impact under the longest thermal history curing regime (slow-heating, high-temperature, long-time curing regime), indicating that the prepreg of this application can be applied to the wide curing process window required for aerospace prepregs. In contrast, the laminate prepared from the prepreg of Comparative Example 1 exhibits a nearly 20% decrease in compressive strength after impact under the longest thermal history curing regime (slow-heating, high-temperature, long-time curing regime), indicating that Comparative Example 1 cannot meet the stability requirements for impact resistance within a wide curing process window. Therefore, the prepreg of this application demonstrates a significant advantage in compressive strength stability after impact within a wide curing process window.

[0116] Compared to the standard curing regime, the laminate prepared from the prepreg of this application exhibits a less than 10% decrease in compressive strength after impact under the first insulation platform curing regime (135℃-3h / 190℃-6h, 1.5℃ / min); and a less than 20% decrease in compressive strength after impact under the second insulation platform curing regime (110℃-4h / 190℃-12h, 2.5℃ / min). This demonstrates that the prepreg of this application is suitable for the insulation platform curing regime required for aerospace prepregs. In contrast, the laminate prepared from the prepreg of Comparative Example 1 exhibits a decrease in compressive strength after impact of greater than or equal to 20% under both insulation platform curing regimes, indicating that Comparative Example 1 is unsuitable for the insulation platform curing regime required for aerospace prepregs.

[0117] Table 4. Performance Test Table of Laying Process Prepared from Prepregs of Examples and Comparative Examples

[0118] As can be seen from Tables 1 and 4, the embodiments of this application can improve the service life of prepregs by adjusting the proportions of components such as materials containing epoxy groups and toughening components (first toughening agent and second toughening agent).

[0119] The prepregs prepared in the embodiments of this application have an operational life of greater than or equal to 240 hours, which meets the requirements of long-term external placement and long-term laying of prepregs in large structural components in the aerospace industry. Furthermore, under the extreme conditions of external lifespan, the aerospace industry generally recommends products with moderate prepreg / stainless steel viscosity and even lower prepreg / prepreg viscosity, which facilitates the separation of prepreg sheets. The inter-material viscosity in the embodiments is much lower than that in Comparative Example 1. Furthermore, Examples 3 and 4 achieve an optimal configuration with slightly higher steel viscosity and lower material viscosity due to the rational design of the ratio of epoxy group-containing materials and the first toughening agent. The impregnation levels of the prepregs in the embodiments all meet the laying process indicators of impregnation content of 40~75 mg and stiffness of 240~280 mm.

[0120] Table 5. Mechanical life performance test results of laminates prepared from the prepregs of the examples and comparative examples.

[0121] As can be seen from Tables 1 and 5, the embodiments of this application can improve the mechanical life of prepregs by adjusting the proportions of components such as materials containing epoxy groups and toughening components (first toughening agent and second toughening agent).

[0122] The prepregs prepared in the embodiments of this application have a mechanical life of ≥720 hours, which meets the requirements for long-term external placement and long-term laying of prepregs in large structural components in the aerospace industry. In particular, the prepregs of the embodiments can achieve a short beam shear strength greater than 100 MPa under external placement for more than one month, far exceeding that of Comparative Example 1. In addition, Example 3, by adjusting the proportion of the first toughening agent and the second toughening agent, achieved a preferred increase in Tg after curing to above 200°C.

[0123] Table 6. Test results of the damp heat resistance of laminates prepared from the prepregs of the examples and comparative examples.

[0124] As can be seen from Tables 1 and 6, the embodiments of this application can improve the moisture and heat resistance of prepregs by adjusting the proportions of components such as materials containing epoxy groups and toughening components (first toughening agent and second toughening agent).

[0125] As can be seen from the above, the adjustments to the proportions of components such as materials containing epoxy groups and toughening components (first toughening agent and second toughening agent) in the embodiments of this application have a significant impact on the mechanical properties and processing properties of the prepreg and its laminate.

[0126] For example, in Example 1, the first toughening agent has a high proportion in the first resin matrix, indicating that the addition of the first toughening agent can improve the impact resistance of the material. In Example 2, compared to Example 1, the proportion of the first toughening agent in the first resin matrix is ​​reduced. By reducing the proportion of the curing agent, the compatibility of the material with slow heating regimes within a wide curing process window is improved. In Example 3, compared to Examples 1 and 2, the proportions of the first toughening agent and the curing agent in the first resin matrix are balanced. The proportion of the first toughening agent has a significant impact on the prepreg's layup processability, while the proportion of the curing agent has a significant impact on the glass transition temperature (Tg) and compressive strength of the cured prepreg. In Example 4, compared to Examples 1, 2, and 3, the proportions of the first toughening agent and the second toughening agent in the second resin matrix are increased. The proportion of the first toughening agent has a significant impact on the prepreg's layup processability, while the proportion of the second toughening agent has a significant impact on the material's toughness.

[0127] To further observe the changes in the morphology and dynamic mechanical properties of the prepreg, a scanning electron microscope was used to observe the cross-sectional morphology of the prepreg casting in Example 3 (e.g., ...). Figure 3 As shown), the interlayer morphology of the prepreg in Example 3 was observed using a metallographic microscope (e.g. Figure 4 As shown), under mechanical life conditions, dynamic mechanical testing (DMA) was performed by curing at 180℃-2h-2℃ / min. Figure 5 (As shown).

[0128] Figure 3 In the fracture surface, the cracks indicate that the epoxy resin matrix has strong toughness and can withstand higher impact energy.

[0129] Figure 4 In the diagram, the white area represents the carbon fiber layer, and the gray area represents the second toughening agent distributed between the fiber layers. Figure 4 It can be seen that the second toughening agent is mainly distributed in the interlayer of the carbon fiber layer, indicating that the prepreg prepared by the four-film method of this application can effectively limit the entry of the second toughening agent into the carbon fiber layer and avoid damage to the carbon fiber layer structure.

[0130] Figure 5 In the graph, the horizontal axis represents temperature (unit: °C); line 1 is the storage modulus curve; line 2 is the loss modulus curve; and line 3 is the loss tangent (tan delta) curve. Storage modulus is an indicator of a material's ability to store energy during elastic deformation, reflecting its rigidity and viscoelastic behavior. It represents the material's ability to store elastic energy under stress or deformation; a higher storage modulus indicates a harder and less deformable material. Loss modulus is a measure of the energy dissipated by internal friction and molecular motion during dynamic deformation; it reflects the material's ability to convert energy into heat or other forms of energy under periodic stress. A higher loss modulus indicates greater viscosity. The loss tangent, the ratio of storage modulus to loss modulus, is used to describe the material's damping characteristics. Figure 5 It can be seen that the point at which the storage modulus of line 1 begins to decrease with increasing temperature is the glass transition temperature (Tgonset), which is 208℃ for this material.

[0131] In summary, the epoxy resin matrix provided in this application has a wide curing process window. According to the formulation design of this application, a high-toughness, high-temperature epoxy resin carbon fiber prepreg can be obtained, exhibiting excellent tensile strength, tensile modulus, and compressive strength, with a lifespan exceeding 240 hours of operational life and 720 hours of mechanical life. The prepreg of this application has good layup processability and is suitable for masterbatch production of hand-laid, tape-laid, and fiber-laid materials. Especially under conditions requiring slow heating and high-temperature long-term curing for large aerospace structural components, the prepreg of this application still maintains excellent impact resistance, meeting the manufacturing needs and safety requirements of large components for civil wide-body aircraft. In the civil aviation manufacturing industry or other structural component manufacturing scenarios that emphasize the external lifespan of prepregs, prepreg layup adhesion, and impact resistance of composite materials, the high-temperature toughened epoxy resin prepreg preparation technology of this application can be practically applied to these scenarios and generate good economic benefits.

[0132] This application improves the overall performance of aerospace prepregs by adjusting the relative proportions of materials containing epoxy groups with the first toughening agent, curing agent, and second toughening agent. Under the premise that the proportions of each input are appropriate, the resin synthesis process is simple and can reproduce the production of 20~300kg of resin, and the subsequent coating and impregnation process parameters have wide boundaries.

[0133] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0134] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An epoxy resin matrix, characterized in that, The epoxy resin matrix includes a first resin matrix and a second resin matrix, wherein the first resin matrix forms the inner layer film of the prepreg, and the second resin matrix forms the outer layer film of the prepreg. The first resin matrix comprises the following raw materials in parts by weight: 50-65 parts by weight of material containing epoxy groups; 14-20 parts by weight of the first toughening agent; Hardener 15-36 parts by weight; The material containing epoxy groups includes a mixture of difunctional, trifunctional, and tetrafunctional materials; the weight ratio of the difunctional, trifunctional, and tetrafunctional materials is 2.43~3.00:3.00~4.00:

1. The first toughening agent has a solubility of more than 90% in the material containing epoxy groups; The second resin matrix comprises the following raw materials in parts by weight: 40-52 parts by weight of material containing epoxy groups; 10-16 parts by weight of the first toughening agent; 15-28 parts by weight of the second toughening agent; 7-35 parts by weight of curing agent; The weight ratio of the difunctional, trifunctional, and tetrafunctional materials in the epoxy group-containing material is 1.50~2.85:2.50~3.23:1; The second toughening agent has a solubility of less than 10% in the material containing epoxy groups; The weight ratio of the material containing epoxy groups, the first toughening agent, and the second toughening agent is 2.08~2.65:0.60~0.76:1; The prepreg formed from the epoxy resin matrix has an inter-sheet tack of 18~20N, an impregnation degree of 40~75mg, and a stiffness of 240~280mg.

2. The epoxy resin matrix according to claim 1, characterized in that, The weight ratio of the material containing epoxy groups to the first toughening agent is 2.85~4.64:

1.

3. A prepreg, characterized in that, The prepreg comprises a reinforcing fiber layer and an epoxy resin matrix, wherein the volume fraction of the reinforcing fiber layer is 55-68% of the volume of the prepreg; The epoxy resin matrix is ​​the epoxy resin matrix as described in any one of claims 1 to 2; The first resin matrix coats the reinforcing fiber layer and fills the gaps within the reinforcing fiber layer; The second resin matrix coats the first resin matrix; The prepreg has an interfacial viscosity of 18-20 N, an impregnation degree of 40-75 mg, and a stiffness of 240-280 mg.

4. A composite material, characterized in that, The composite material is formed by curing the prepreg described in claim 3 according to a preset regime.

5. A method for preparing a composite material, characterized in that, The method for preparing the composite material is used to prepare the composite material as described in claim 4, the method comprising: The prepreg is cured according to a preset regime to obtain the composite material; the preset regime includes a heat preservation regime and / or a curing regime; The heat preservation system includes: a heat preservation temperature of 130~140℃ and a heat preservation time of 2~4h; or, a heat preservation temperature of 105~115℃ and a heat preservation time of 2~4h. The curing regime includes: a curing temperature of 170~190℃, a curing time of 2~12h, and a heating rate of 0.3~3℃ / min.

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