An adaptive morphing flexible composite material and its forming method and application

Abstract

The application relates to a self-adapting deformation flexible composite material and a forming method and application thereof, and belongs to the technical field of heat-resistant material preparation. The forming method of the flexible composite material comprises the following steps: mixing phenolic fibers and hot-melt yarns according to a mass ratio, obtaining a phenolic fiber needle-punched preform through carding, parallel web laying and needle punching processes; soaking the phenolic fiber needle-punched preform in a modified solution, and drying after soaking; preparing a modified preform; stirring and mixing a hybrid phenolic resin, a toughening agent solution and a surface heat dissipating agent to prepare a modified phenolic resin; and using mold forming to make the modified phenolic resin infiltrate the modified preform to prepare the flexible composite material. The overall strength and flexibility of the composite material are enhanced, the self-adapting deformation capability is realized, active adhesion to the thermal deformation and vibration deformation of a space engine cabin body can be realized, and the phenomena of warping and debonding can be avoided.

Description

Technical Field

[0001] This invention relates to the field of heat-resistant material preparation technology, and in particular to an adaptive deformation flexible composite material, its molding method, and its application. Background Technology

[0002] The external thermal protection system for aerospace engine nacelles is a critical component in ensuring the structural integrity and reliability of the engine. External thermal protection for aerospace engine nacelles primarily employs high-temperature resistant coating technology, which is typically applied using a spraying process.

[0003] However, existing coating technologies have many inherent defects. First, the spraying process is complex and the quality is inconsistent. For irregularly shaped components such as engine compartment exteriors with many vertical ribs, concave corners, and irregular curved surfaces, the spraying airflow interference is severe, and the coating is prone to defects such as blistering and uneven thickness. Second, under high-temperature service conditions, the coating strength is poor and cannot adapt to the deformation requirements of the engine compartment exterior structure under thermo-mechanical coupling, making the coating prone to cracking and peeling. Third, coating construction requires specialized equipment and a clean environment, the spraying cycle is long and the cost is high, and once it fails, it needs to be completely removed and repainted, resulting in poor maintainability.

[0004] To address the shortcomings of existing coatings, such as long construction cycles, high costs, insufficient material strength, poor thermal insulation synergy, and weak deformation adaptability, a flexible thermal protection composite material with simple construction process, controllable cost, adaptive deformation capability, and reliable bonding to the outer wall of the engine compartment via adhesive bonding is developed. This overcomes the inherent defects of existing high-temperature resistant coating technologies and improves the reliability and maintainability of the aerospace engine thermal protection system. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide an adaptive deformation flexible composite material, its molding method and application, to solve one of the problems of insufficient strength, poor deformation adaptability and poor heat insulation synergy of existing flexible heat-resistant materials.

[0006] On one hand, the present invention provides a method for molding an adaptive deformation flexible composite material, comprising the following steps: S1: Phenolic fibers are mixed with hot melt yarn according to the mass ratio, and after carding, parallel web laying and needle punching processes, phenolic fiber needle punched preforms are obtained. The phenolic fiber is a chopped fiber with a length of 50-80 mm; The length of the hot-melt yarn is 30-40 mm, and the fineness is 2.2-3.3 dtex; The mass ratio of the phenolic fiber to the hot-melt yarn is 10-15:1-2; the needle-punching density of the needle-punching process is 15-25 needles / cm. 2 ; S2: The phenolic fiber needle-punched preform is immersed in a modification solution and then dried; the modified preform is obtained. The modified solution is a solution obtained by dissolving the coupling agent in an organic solvent; S3: The hybrid phenolic resin, toughening agent solution and surface heat dissipation agent are stirred and mixed to obtain the modified phenolic resin; the mass ratio of the hybrid phenolic resin, the toughening agent solution and the surface heat dissipation agent is 100:10-20:0.5-1; S4: A flexible composite material is obtained by molding a modified phenolic resin to impregnate the modified preform.

[0007] Further, in step S1, the phenolic fiber is a chopped fiber with a length of 55-75 mm; The length of the hot-melt yarn is 35-40 mm, and the fineness is 2.3-3.2 dtex; The hot melt yarn is one or more of nylon hot melt yarn (PA), polyester hot melt yarn (PET), and polyethylene-polypropylene bicomponent core-sheath hot melt yarn (ES).

[0008] Furthermore, the mass ratio of the phenolic fiber to the hot melt yarn is (11-15):(1-2).

[0009] Furthermore, in step S1, the needle density of the needle-punching process is 16-20 needles / cm. 2 .

[0010] Further, in step S2, the coupling agent is one or more of isopropyl tris(dioctylphosphoyloxy)titanate, isopropyl tris(isostearoyl)titanate, and di(dioctylpyrophosphoyloxy)ethylenetitanate.

[0011] Further, in step S3, the mass ratio of the hybrid phenolic resin, the toughening agent solution, and the surface heat dissipation agent is 100:(11-19):(0.5-1).

[0012] Furthermore, the toughening agent solution is a mixture of a toughening agent and an organic solvent; The toughening agent is one or more of polycaprolactone diol, polypropylene glycol, and polycarbonate diol.

[0013] Furthermore, the surface heat dissipation agent is one or more of nano boron nitride, nano aluminum nitride, and nano aluminum oxide.

[0014] On the other hand, the present invention provides an adaptive deformation flexible composite material, which is obtained by the molding method described in the present invention.

[0015] Furthermore, the resulting adaptive deformation flexible composite material is used in the fabrication of temperature-resistant components.

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. In this invention, by combining phenolic fiber with hot melt yarn, combined with needle punching process and modification treatment, the compatibility between fiber preform and modified phenolic resin is greatly improved, the overall strength and flexibility of composite material are enhanced, and adaptive deformation capability is achieved. It can actively fit with the thermal deformation and vibration deformation of aerospace engine cabin, avoiding lifting and delamination.

[0017] 2. In this invention, the mass ratio of the hybrid phenolic resin, the toughening agent solution, and the surface heat dissipation agent is 100:(10-20):(0.5-1). The hybrid phenolic resin is flexibly modified by the toughening agent and a surface heat dissipation agent is added, which not only ensures the excellent high-temperature heat insulation performance and surface heat dissipation effect of the composite material, but also improves the toughness of the material, avoids cracking and peeling at high temperatures, and takes into account the erosion resistance of the material.

[0018] 3. Using the preparation method provided by this invention, the modified phenolic resin impregnated with the modified preform yields a composite material with a density of 0.46-0.5 g / cm³. 3 The composite material exhibits a tensile strength of 4.2-5.3 MPa, an elongation at break of 9.5-11.6%, a thermal conductivity of 0.050-0.054 W / (m·K), and a linear ablation rate of 0.005-0.006 mm / s (oxyacetylene at 1000℃, 30s). It also possesses good flexibility, with a bending angle exceeding 120° and a springback of less than 5% after stress. The resulting composite material demonstrates superior performance and can be used in the fabrication of heat-resistant components. It adapts to deformation and can be reliably bonded to the outer wall of the engine nacelle via adhesive bonding, thereby improving the reliability and maintainability of aerospace engine thermal protection systems.

[0019] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0021] Figure 1 This is a macroscopic view of the resulting flexible composite material. Detailed Implementation

[0022] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0023] The external thermal protection system for aerospace engine nacelles is a critical component in ensuring the structural integrity and reliability of the engine. External thermal protection for aerospace engine nacelles primarily employs high-temperature resistant coating technology, which is typically applied using a spraying process. However, this method has several drawbacks, such as insufficient material strength, poor thermal insulation synergy, and weak deformation adaptability.

[0024] Therefore, the present invention provides a method for molding an adaptive deformation flexible composite material, comprising the following steps: S1: Phenolic fibers are mixed with hot melt yarn according to the mass ratio, and after carding, parallel web laying and needle punching processes, phenolic fiber needle punched preforms are obtained. S2: The phenolic fiber needle-punched preform is immersed in a modification solution and then dried; the modified preform is obtained. The modified solution is a solution obtained by dissolving the coupling agent in an organic solvent; S3: The hybrid phenolic resin, toughening agent solution and surface heat dissipation agent are stirred and mixed to obtain the modified phenolic resin; S4: A flexible composite material is obtained by molding a modified phenolic resin to impregnate the modified preform.

[0025] Compared with existing technologies, this invention significantly improves the compatibility between fiber preforms and modified phenolic resins by combining phenolic fibers with hot-melt yarns, combined with needle punching and modification treatment. This enhances the overall strength and flexibility of the composite material, achieves adaptive deformation capability, and can actively adhere to the thermal deformation and vibration deformation of the aerospace engine cabin, avoiding lifting and delamination.

[0026] The composite material obtained by this invention has superior properties, with a density of 0.46-0.5 g / cm³. 3 It has a tensile strength of 4.2-5.3 MPa, an elongation at break of 9.5-11.6%, a thermal conductivity of 0.050-0.054 W / (m·K), a linear ablation rate of 0.005-0.006 mm / s (oxyacetylene 1000℃, 30s), and good flexibility, with a bending angle of over 100° and a springback of less than 5% after applying force.

[0027] The hybrid phenolic resin, after being flexibly modified with toughening agents and supplemented with surface heat dissipation agents, not only ensures the composite material's excellent high-temperature thermal insulation performance and surface heat dissipation effect, but also improves the material's toughness, preventing cracking and peeling at high temperatures, while also taking into account the material's erosion resistance. Furthermore, the flexible composite material exhibits good adhesive compatibility, allowing for rapid bonding to the outer surface of aerospace engine bays, replacing traditional high-temperature resistant coatings. It is also easy to maintain and can meet the thermal protection requirements of next-generation aerospace engines under extreme thermo-mechanical coupling conditions.

[0028] Specifically, in step S1, the phenolic fiber is a chopped fiber with a length of 50-80 mm.

[0029] It should be noted that in this invention, the length of the phenolic fiber or chopped fiber affects the mechanical properties and flexibility of the composite material. When the length of the chopped fiber is too short, i.e., less than 50 mm, the mechanical properties of the resulting composite material will be reduced; when the length of the chopped fiber is too long, i.e., greater than 80 mm, the elongation at break of the resulting composite material will decrease significantly, resulting in poor flexibility. When applied to aerospace engine cabins, this can also lead to warping and debonding.

[0030] In this invention, the length of the chopped fiber can be 50mm, 55mm, 60mm, 65mm, 70mm, 75mm or 80mm.

[0031] Specifically, the length of the hot-melt yarn is 30-40 mm, and the fineness is 2.2-3.3 dtex; Specifically, the hot melt yarn is one or more of nylon hot melt yarn (PA), polyester hot melt yarn (PET), and polyethylene-polypropylene bicomponent core-sheath hot melt yarn (ES).

[0032] It should be noted that in this invention, the hot-melt yarn is selected from PA, PET, and ES, which have high performance stability. It can be used individually, such as PA, PET, or ES; in combination of two, such as PA and ES, PA and PET, or PET and ES; or in combination of three, such as PA, PET, and ES. When used in combination, the proportions are not limited, as long as the mass ratio of phenolic fiber to the hot-melt yarn is satisfied.

[0033] Similarly, in this invention, it is necessary to control the length and fineness of the hot-melt yarn. When the length of the hot-melt yarn is too short, its ability to bind and confine phenolic fibers is limited, failing to meet the mechanical performance requirements. When the length of the hot-melt yarn is too long, its ability to confine phenolic fibers is too strong, reducing the flexibility of the composite material. If the fineness of the hot-melt yarn is too small, its toughening effect on the composite material is limited and cannot be effectively improved. If the fineness of the hot-melt yarn is too large, macroscopic pores will be introduced during operation, thereby affecting the mechanical properties of the composite material.

[0034] In this invention, the length of the hot melt yarn can be 30mm, 35mm or 40mm.

[0035] In this invention, the fineness of the hot melt yarn can be 2.2dtex, 2.3dtex, 2.4dtex, 2.5dtex, 2.6dtex, 2.7dtex, 2.8dtex, 2.9dtex, 3.0dtex, 3.1dtex, 3.2dtex or 3.3dtex.

[0036] Specifically, the mass ratio of the phenolic fiber to the hot melt yarn is (10-15):(1-2).

[0037] It should be noted that by combining hot melt yarn with a fineness of 2.2~3.3dtex with phenolic fibers at a specific mass ratio of (10-15):(1-2), the hot melt yarn can be evenly inserted and wrapped inside the phenolic fiber matrix and in the fiber gaps. After being heated, the hot melt yarn can accurately melt and bond the interlacing nodes of the phenolic fibers, which improves the defects of pure phenolic fibers such as high brittleness, poor cohesion, and easy loosening and shedding, and ensures the overall flexibility and structural integrity of the composite material after molding.

[0038] When there is too much phenolic fiber or too little hot melt yarn, there are insufficient bonding points between fibers, resulting in poor cohesion of phenolic fibers and the composite material is prone to delamination, fuzzing, and loose structure.

[0039] When the mass of phenolic fiber is too small or the mass of hot melt yarn is too large, the excess hot melt yarn is prone to excessive melting and flow in a high-temperature environment, which will damage the original heat resistance and ablation resistance of phenolic fiber, resulting in a decrease in the thermal stability of the material and serious problems of high-temperature shrinkage and deformation.

[0040] In this invention, the mass ratio of the phenolic fiber to the hot-melt yarn can be 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 10:2, 11:2, 12:2, 13:2, 14:2 or 15:2.

[0041] Specifically, in step S1, the needle density of the needle-punching process is 15-25 needles / cm. 2 .

[0042] It should be noted that in this invention, a reasonable needle punching density is the key to balancing mechanical properties and interlaminar properties. Therefore, it is necessary to control the needle punching density in the needle punching process. When the needle punching density is too high, the fiber preform will be excessively damaged, affecting the mechanical properties and elongation at break of the composite material. When the needle punching density is too low, the interlaminar force of the composite material is too weak, and cracks will occur during operation.

[0043] It should be noted that the thickness of the phenolic fiber needle-punched preform is 1-10 mm. When the thickness of the phenolic fiber needle-punched preform exceeds 10 mm, the flexibility of the composite material will be reduced.

[0044] In this invention, the needle density of the needle-punching process can be 15 needles / cm. 2 16 stitches / cm 2 17 stitches / cm 2 18 stitches / cm 2 19 stitches / cm 2 20 stitches / cm 2 21 stitches / cm 2 22 stitches / cm 2 23 stitches / cm 2 24 stitches / cm 2 Or 25 stitches / cm 2 The thickness of the phenolic fiber needle-punched preform can be 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm.

[0045] Specifically, in step S1, phenolic fibers and hot-melt yarn are separately placed into an opening machine for opening treatment to ensure that the fibers are evenly dispersed and free of lumps. Then, the phenolic fibers and hot-melt yarn are mixed according to the mass ratio; the mixed phenolic fibers are fed into a carding machine to obtain a uniform mixed fiber web; and a parallel web laying machine is used to lay the web to form a multi-layered structure.

[0046] Specifically, in step S2, the coupling agent is one or more of isopropyl tris(dioctylphosphoyloxy)titanate, isopropyl tris(isostearoyl)titanate, and di(dioctylpyrophosphoyloxy)ethylenetitanate.

[0047] It should be noted that in this invention, the obtained phenolic fiber needle-punched preform needs to be immersed and modified in a modified solvent. The modified solvent is obtained by dissolving the coupling agent in an organic solvent. After the coupling agent fully wets the phenolic fiber needle-punched preform, it hydrolyzes to form active titanium hydroxyl groups, which undergo a condensation reaction with the hydroxyl groups on the fiber surface to form covalent bonds. The molecular structure of the coupling agent contains flexible aliphatic side chains, which can construct a low surface energy, high flexibility organic coating layer on the fiber surface, effectively reducing the coefficient of friction and interfacial adhesion between fibers. At the same time, it improves the bending toughness and extensibility of the fiber through the internal rotation ability of the molecular chain segments, thereby significantly improving the overall flexibility of the fiber.

[0048] Preferably, the mass concentration of the modified solution is 3-5%.

[0049] Preferably, the organic solvent is selected from isopropanol, acetone and ethyl acetate.

[0050] Preferably, in step S2, the soaking time is 20-30 minutes.

[0051] Preferably, in step S2, the drying temperature is 95-100℃ and the drying time is 2-3 hours.

[0052] It should be noted that in this invention, the obtained phenolic fiber needled preform is immersed in a modified solvent, with the organic solvent as a carrier, so that the coupling agent can be uniformly penetrated and dispersed throughout the phenolic fiber needled preform; then, by drying, the organic solvent is removed, and the coupling agent component is retained and uniformly attached to the surface of the phenolic fiber needled preform, thereby achieving surface modification of the phenolic fiber needled preform.

[0053] Specifically, in step S3, the mass ratio of the hybrid phenolic resin, the toughening agent solution, and the surface heat dissipation agent is 100:(10-20):(0.5-1).

[0054] For example, the mass ratio of the hybrid phenolic resin, the toughening agent solution, and the surface heat dissipation agent can be 100:10:0.5, 100:10:0.6, 100:10:0.7, 100:10:0.8, 100:10:0.9, 100:10:1.0, 100:11:0.5, 100:11:0.6, 100:11:0.7, 100:11:0.8, 100:11:0.9, 100:11:1.0, 100:12:0.5, 100:12:0.6, 100:12:0.7, 100:12:0.8, 100:12:0.9, 100:12:1.0, 100:13:0.5, 100:13:0.6, 100:13:0.7, 100:13:0.8, 100:13:0.9, 100:13:1.0, 100:14:0.5, 100:14:0.6, 100:14:0.7, 100:14:0.8, 100:14:0.9, 100:14:1.0, 100:15:0.5, 100: 15:0.6, 100:15:0.7, 100:15:0.8, 100:15:0.9, 100:15:1.0, 100:16:0.5, 100:16:0.6, 100:16:0.7, 100:16:0.8, 100:16:0.9, 100:16:1.0, 100:17:0.5, 100:17:0.6, 100:17:0.7, 100:17:0.8, 100:17:0.9, 100:17:1.0, 100:18: 0.5, 100:18:0.6, 100:18:0.7, 100:18:0.8, 100:18:0.9, 100:18:1.0, 100:19:0.5, 100:19:0.6, 100:19:0.7, 100:19:0.8, 100:19:0.9, 100:19:1.0, 100:20:0.5, 100:20:0.6, 100:20:0.7, 100:20:0.8, 100:20:0.9 or 100:20:1.0.

[0055] It should be noted that the hybrid phenolic resin is flexibly modified with a toughening agent and a surface heat dissipation agent is added. This not only ensures the excellent high-temperature heat insulation performance and surface heat dissipation effect of the composite material, but also improves the toughness of the material, preventing cracking and peeling at high temperatures, while also taking into account the material's erosion resistance.

[0056] In this invention, the hybrid phenolic resin is an organosilicon hybrid phenolic resin, and the viscosity of the organosilicon hybrid phenolic resin is 10-200 mPa. s, after curing, forms a nanoporous structure of 150-250nm; or the organosilicon hybrid phenolic resin is prepared by the method described in Chinese Patent Application No. CN201911266938.7, High-strength nanoporous ceramic erosion-resistant heat-resistant composite material and its preparation method.

[0057] The specific preparation method of organosilicon hybrid phenolic resin is as follows: phenol and aldehyde and catalyst are mixed and reacted to obtain phenolic resin, high molecular weight organosilicon is added, the mixture is refluxed and heated, the pH is adjusted, and finally vacuum is applied to obtain organosilicon hybrid phenolic resin. The molar ratio of phenol to aldehyde is (5-7):10; the temperature of the mixed reaction is 70-75℃ and the time is 1-2 h; the temperature of the reflux heating is 85-95℃ and the time is 2-3 h; and the pH is adjusted to 6-8.

[0058] The phenol includes one or both of resorcinol or phenol, the aldehyde includes one or both of formaldehyde or furfural, and the catalyst includes one or both of oxalic acid or hydrochloric acid. The catalyst has a molar amount of 4-6% of phenol, and the mass ratio of high molecular weight organosilicon to phenolic resin is (0.1-0.8):1.

[0059] It should be noted that in this invention, the hybrid phenolic resin, toughening agent solution, and surface heat dissipation agent are stirred and mixed to obtain the modified phenolic resin. The three components must be uniformly mixed and the system must remain stable without flocculation or phase separation to obtain a modified resin suitable for the injection molding process. Uneven mixing or phase separation will lead to decreased resin flowability and hinder the injection molding process; in severe cases, it can also cause component segregation and uneven microstructure within the cured composite material, making it difficult to guarantee the consistency of the final product in terms of mechanical properties, thermal stability, and heat dissipation.

[0060] Specifically, the toughening agent solution is a solution obtained by mixing a toughening agent with isopropanol; The toughening agent is one or more of polycaprolactone diol, polypropylene glycol, and polycarbonate diol.

[0061] It should be noted that adding toughening agents to hybrid phenolic resins significantly improves their defects such as brittleness, easy cracking, and poor impact resistance after curing, and enhances the material's flexibility, bending resistance, and structural integrity. Preferably, the number average molecular weights of the polycaprolactone diol, polypropylene glycol, and polycarbonate diol are 500-3000. These toughening agents can balance low temperature, low viscosity, fiber wettability, and compatibility with organosilicon hybrid phenolic resins.

[0062] In this invention, the toughening agent is selected from polycaprolactone diol, polypropylene glycol, and polycarbonate diol. It can be used as a single component, for example, the toughening agent is polycaprolactone diol, polypropylene glycol, or polycarbonate diol; it can also be used in combination of two components, for example, polycaprolactone diol and polypropylene glycol, preferably with a mass ratio of polycaprolactone diol to polypropylene glycol of (3~8):(7~2); for example, polycaprolactone diol and polycarbonate diol, preferably with a mass ratio of polycaprolactone diol to polycarbonate diol of (4~7):(6~3); for example, polypropylene glycol and polycarbonate diol, preferably with a mass ratio of polypropylene glycol to polycarbonate diol of (2~6):(8~4); it can also be used in combination of three components, for example, polycaprolactone diol, polypropylene glycol, and polycarbonate diol, preferably with a mass ratio of polycaprolactone diol, polypropylene glycol, and polycarbonate diol of (4~6):(1~3):(3~5).

[0063] Specifically, the surface heat dissipation agent is one or more of nano boron nitride, nano aluminum nitride, and nano aluminum oxide.

[0064] It should be noted that in the process of preparing modified phenolic resin in this invention, a surface heat dissipation agent needs to be added. Through the complementary and synergistic effect of the toughening agent and the organosilicon hybrid phenolic resin component, the thermal conductivity and heat dissipation efficiency and the stability of use of the final composite material surface are improved, and the linear ablation rate of the composite material is reduced.

[0065] The surface heat dissipation agent is selected from nano boron nitride, nano aluminum nitride, and nano aluminum oxide. It can be used as a single component, for example, the surface heat dissipation agent is nano boron nitride, nano aluminum nitride, or nano aluminum oxide; or it can be a compound of two or three. When two components are compounded, for example, nano boron nitride and nano aluminum oxide are compounded, the preferred mass ratio is (3~7):(7~3); for example, nano boron nitride and nano aluminum nitride are compounded, the preferred mass ratio is (5~9):(5~1); for example, nano aluminum oxide and nano aluminum nitride are compounded, the preferred mass ratio is (6~9):(4~1); when three components are compounded, the surface heat dissipation agent is nano boron nitride, nano aluminum nitride, and nano aluminum oxide, the preferred mass ratio is (4~7):(1~3):(2~5).

[0066] Preferably, in step S3, the mixing temperature is 30-40°C.

[0067] Preferably, in step S3, the stirring rate of the mixing is 150-200 rpm.

[0068] It should be noted that in this invention, the toughening agent is first prepared into a homogeneous solution using an organic solvent, then mixed with an organosilicon hybrid phenolic resin, and subsequently the surface heat dissipation agent is added in stages, which effectively prevents flocculation after mixing. Pre-dissolving the toughening agent in an organic solvent before compounding it with the organosilicon hybrid phenolic resin avoids the problems of localized agglomeration and phase separation caused by direct feeding.

[0069] During the mixing process, the present invention controls the temperature to 30-40℃, which can reduce the viscosity of the organosilicon hybrid phenolic resin, promote the uniform diffusion of each component, and avoid rapid solvent evaporation and premature cross-linking of the organosilicon hybrid phenolic resin.

[0070] In addition, it is necessary to control the stirring rate to 150-200 rpm to break up the soft agglomerates of the surface heat dissipation agent, while avoiding particle breakage, secondary agglomeration and air bubble entrainment, so as to achieve uniform and stable three-phase blending of organosilicon hybrid phenolic resin, toughening agent and surface heat dissipation agent.

[0071] In step S4, a 30-100 mesh metal mesh is laid on the mold, a release cloth is laid on the metal mesh, the modified preform is placed on the release cloth, the mold is locked, and the modified phenolic resin is fully impregnated into the fiber preform using the RTM molding process. The resin is cured, the product is demolded, dried, and processed to obtain an adaptive deformation flexible composite material.

[0072] Preferably, the metal mesh is a woven metal mesh with a wire diameter of 0.25 mm.

[0073] It should be noted that the metal mesh acts as a guide, enabling the surface dispersant to be evenly distributed on the ablation surface of the composite material, thus achieving the thermal radiation effect of the final surface heat dissipation agent.

[0074] Preferably, the vacuum negative pressure of the RTM molding process is 300-500 mbar, and the maximum injection pressure is controlled at 2-5 bar.

[0075] Preferably, the curing temperature is 90-120℃ and the curing time is 24-36h.

[0076] This invention also provides an adaptive deformation flexible composite material, prepared by the molding method described above. The resulting composite material has a density of 0.46-0.5 g / cm³. 3 The composite material exhibits a tensile strength of 4.2-5.3 MPa, an elongation at break of 9.5-11.6%, a thermal conductivity of 0.050-0.054 W / (m·K), and a linear ablation rate of 0.005-0.006 mm / s (oxyacetylene at 1000℃, 30s). It also possesses good flexibility, with a bending angle exceeding 100° and a springback of less than 5% after applying force, demonstrating good conformability to curved surfaces. This composite material can be used in the fabrication of high-temperature resistant components and then bonded to the outer wall of the engine compartment via adhesive bonding, completely replacing traditional high-temperature resistant coatings.

[0077] To more clearly describe the present invention, the following examples and comparative examples are provided for further illustration. In the examples and comparative examples of the present invention, the hybrid phenolic resin is an organosilicon hybrid phenolic resin, prepared by the method described in Example 1 of Chinese Patent Application No. CN201911266938.7.

[0078] Example 1 The preparation of an adaptive deformation flexible composite material includes the following steps: S1: Phenolic fibers and hot-melt yarn are separately placed into an opening machine for opening treatment to ensure that the fibers are evenly dispersed and free of lumps. The phenolic fibers and hot-melt yarn are mixed at a mass ratio of 10:1. The mixed phenolic fibers are fed into a carding machine to obtain a uniform mixed fiber web. A parallel web laying machine is used to lay the web to form a multi-layer superimposed structure. Then, it is fed into a needle punching machine and needle punched at a needle punching density of 15 needles / cm². During the needle punching process, the thickness compression of the fiber preform is controlled to be 2mm, and finally a phenolic fiber needle punched preform with a thickness of 5mm is prepared. The phenolic fiber is a short-cut phenolic fiber with a length of 50mm; The hot melt yarn is a nylon hot melt yarn PA with a length of 30mm and a fineness of 2.2dtex; S2: Isopropyl tris(dioctylphosphoyloxy)titanate was selected as the coupling agent and dissolved in isopropanol. The solution was stirred evenly to prepare a coupling agent solution with a mass concentration of 3%. The phenolic fiber needle-punched preform was placed in the coupling agent solution and the soaking time was controlled to be 20 min. After soaking, the phenolic fiber needle-punched preform was taken out, placed in a PTFE tray, and placed in a forced-air drying oven. It was dried at 95℃ for 2 h. After drying, it was taken out to obtain the modified preform. S3: Select polycaprolactone diol (number average molecular weight of 1500) as toughening agent, mix it with isopropanol, stir until completely dissolved, and prepare a toughening agent solution with a mass concentration of 10%. According to the mass ratio of hybrid phenolic resin: toughening agent solution: surface heat dissipation agent = 100:10:0.5, the hybrid phenolic resin, the above toughening agent solution and nano boron nitride (surface heat dissipation agent) are placed in a stirring vessel, the stirring temperature is controlled at 30℃ and the stirring speed is 150 rpm, and the mixture is stirred until the three are evenly mixed; after the mixture is completed, the mixture is placed in a vacuum degassing machine for vacuum degassing treatment, and after the degassing is completed, it is taken out to obtain modified phenolic resin; S4: Select a flat mold and evenly lay a layer of 30-mesh metal woven mesh on the mold surface. The wire diameter of the metal woven mesh is 0.25mm. Lay a layer of release cloth on the metal woven mesh, ensuring that the release cloth is flat and wrinkle-free. Lay the modified preform flat on the release cloth, adjust its position to fit tightly with the mold, and then lock the mold to ensure that the cavity is sealed. Use RTM molding process to slowly inject modified phenolic resin into the mold cavity. The vacuum negative pressure of RTM molding process is 600mbar, the injection pressure is controlled at 2bar, and the injection speed is controlled at 100-150g / min to ensure that the resin fully impregnates the fiber preform without any air bubbles remaining. After the resin is fully impregnated, the product is cured by heating according to the conventional phenolic resin curing process. The curing temperature is 95℃ and the curing time is 24 hours. After curing, the mold is opened to demold the product. The demolded product is placed in a forced-air drying oven for normal pressure drying. After drying, the edges are trimmed and other subsequent processing is carried out to finally obtain the adaptive deformation flexible composite material.

[0079] Example 2 Example 2 is prepared in a similar manner to Example 1, except that in step S1 of Example 2: the length of the chopped phenolic fiber is 65 mm; the length of the hot melt yarn is 30 mm and the fineness is 2.2 dtex; and a mixture of polyester hot melt yarn (PET) and polyethylene-polypropylene bicomponent core-sheath hot melt yarn (ES) is used (mass ratio of 1:1). The needle-punching technique is used, and the needle density is controlled at 20 needles / cm. 2 A phenolic fiber needle-punched preform with a thickness of 5 mm was prepared.

[0080] In step S2: A mixed coupling agent of isopropyl tris(isostearoyl) titanate and di(dioctylpyrophosphoryl) ethylene titanate (mixing ratio 1:1) is selected, dissolved in isopropanol, and prepared into a coupling agent solution with a mass concentration of 4%; the phenolic fiber needle-punched preform is immersed in the solution and intermittently pressed with a pressure plate for 25 minutes; after immersion, it is placed in a PTFE tray and dried in a 98℃ forced-air drying oven for 2.5 hours, and then cooled to room temperature to obtain the modified fiber preform.

[0081] In step S3: Select a toughening agent mixture of polypropylene glycol (number average molecular weight of 1500) and polycarbonate glycol (number average molecular weight of 1500) (mixing ratio 1:2), and mix it with isopropanol to prepare a toughening agent solution with a mass concentration of 15%; according to the mass ratio of hybrid phenolic resin: toughening agent solution: surface heat dissipation agent = 100:15:0.8, take hybrid phenolic resin, toughening agent solution and a mixed heat dissipation agent of nano aluminum nitride and nano aluminum oxide (mixing ratio 2:1), stir evenly at 35℃ and 180 rpm, and then use it after vacuum degassing treatment.

[0082] In step S4: a layer of 60-mesh metal woven mesh (wire diameter 0.25mm) is laid on the surface of the mold. After laying the release cloth, the modified fiber preform is placed on the release cloth and the mold is locked. Flexible modified phenolic resin is injected using RTM molding process to ensure that the resin fully impregnates the fiber preform. After heating and curing, demolding, normal pressure drying and subsequent processing, an adaptive deformation flexible composite material is obtained.

[0083] Example 3 The preparation process of Example 3 is largely the same as that of Example 1, except that in step S1 of Example 3: the length of the chopped phenolic fiber is 80 mm; the length of the hot melt yarn is 40 mm and the fineness is 3.3 dtex; the hot melt yarn is a polyethylene-polypropylene bicomponent core-sheath hot melt yarn ES. A phenolic fiber needled preform with a thickness of 10 mm was prepared by needle punching at a needle density of 25 needles / cm².

[0084] In step S2: Di(dioctylpyrophosphoryl)ethylene titanate is selected as the coupling agent and dissolved in isopropanol to prepare a coupling agent solution with a mass concentration of 5%. The phenolic fiber needle-punched preform is immersed in the solution for 30 minutes, and intermittently pressed during the immersion process. After immersion, it is placed in a PTFE tray and dried in a 100℃ forced-air drying oven for 3 hours. After cooling, the modified fiber preform is obtained.

[0085] In step S3: Polycarbonate diol (number average molecular weight of 1500) is selected as a toughening agent and mixed with isopropanol to prepare a toughening agent solution with a mass concentration of 20%; according to the mass ratio of hybrid phenolic resin: toughening agent solution: surface heat dissipation agent = 100:20:1, hybrid phenolic resin, toughening agent solution and nano boron nitride are taken and stirred evenly at 40℃ and 200 rpm, and then vacuum degassing treatment is performed before use.

[0086] In step S4: a layer of 100-mesh metal woven mesh (wire diameter 0.25mm) is laid on the surface of the mold, and after laying the release cloth, the modified fiber preform is placed and the mold is locked; flexible modified phenolic resin is injected using RTM molding process, and after impregnation, it is heated and cured. After demolding, it is dried under normal pressure and processed to obtain an adaptive deformation flexible composite material.

[0087] Comparative Example 1 The preparation process of Comparative Example 1 is largely the same as that of Example 1, except that step S2 is not included in Comparative Example 1 and the phenolic fiber needled preform is not modified.

[0088] Comparative Example 2 The preparation process of Comparative Example 2 is largely the same as that of Example 1, except that Comparative Example 2 does not include toughening agent solution and surface heat dissipation agent.

[0089] Comparative Example 3 The preparation process of Comparative Example 3 is largely the same as that of Example 1, except that no surface heat dissipation agent is added in step S3 of Comparative Example 3.

[0090] Comparative Example 4 The preparation process of Comparative Example 4 is largely the same as that of Example 1, except that the length of the chopped fiber in Comparative Example 4 is 100 mm and the length of the hot melt yarn is 50 mm.

[0091] Comparative Example 5 The preparation process of Comparative Example 5 is largely the same as that of Example 1, except that the mass ratio of the phenolic fiber to the hot melt yarn in Comparative Example 5 is 18:0.8.

[0092] Comparative Example 6 Comparative Example 6 is prepared in a manner largely similar to that of Example 1, except that the needle density in the needle-punching process described in Comparative Example 6 is 30 needles / cm². 2 .

[0093] Comparative Example 7 The preparation process of Comparative Example 7 is largely the same as that of Example 1, except that in step S3 of Comparative Example 7, the mass ratio of the hybrid phenolic resin, the toughening agent solution and the surface heat dissipation agent is 100:25:1.5.

[0094] Performance testing The flexible composite materials obtained in the above embodiments and comparative examples were subjected to performance tests, mainly including density, tensile strength, elongation at break, thermal conductivity, linear ablation rate (oxyacetylene 1000℃, 30s), bending angle, and springback. The test results are shown in Table 1.

[0095] Linear ablation rate is tested according to the standard: GJB323B-2018 "Test Method for Ablation of Absorbable Materials"; The bending angle is tested according to the standard GB / T38806-2020 "Metallic materials, thin plates and strips, test methods for bending properties"; The springback is referenced to the standard GB / T 22565.1-2021 "Metallic materials, thin plates and strips, evaluation method of springback performance".

[0096] Table 1 Performance Test Results

[0097] As can be seen from Examples 1-3 and Comparative Examples 1-7, and with reference to Table 1, in this invention, the compatibility between the fiber preform and the modified phenolic resin is significantly improved through the compounding of phenolic fibers and hot-melt yarns, combined with needle punching and modification treatment. This enhances the overall strength and flexibility of the composite material, achieving adaptive deformation capability and enabling active bonding with the thermal deformation and vibration deformation of the aerospace engine cabin. Using the preparation method provided by this invention, the modified phenolic resin impregnates the modified preform, resulting in a composite material with a density of 0.46-0.5 g / cm³. 3 The composite material exhibits a tensile strength of 4.2-5.3 MPa, an elongation at break of 9.5-11.6%, a thermal conductivity of 0.050-0.054 W / (m·K), and a linear ablation rate of 0.005-0.006 mm / s (oxyacetylene at 1000℃, 30s). It also demonstrates good flexibility, with a bending angle exceeding 100° and a springback of less than 5% after stress. The resulting composite material possesses superior performance and can be used in the fabrication of heat-resistant components. It adapts to deformation and is reliably bonded to the outer wall of the engine nacelle via adhesive bonding, thereby improving the reliability and maintainability of the aerospace engine's thermal protection system.

[0098] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A molding method for an adaptive deformation flexible composite material, characterized in that, Includes the following steps: S1: Phenolic fibers are mixed with hot melt yarn according to the mass ratio, and after carding, parallel web laying and needle punching processes, phenolic fiber needle punched preforms are obtained. The phenolic fiber is a chopped fiber with a length of 50-80 mm; The length of the hot-melt yarn is 30-40 mm, and the fineness is 2.2-3.3 dtex; The mass ratio of the phenolic fiber to the hot-melt yarn is 10-15:1-2; the needle-punching density of the needle-punching process is 15-25 needles / cm. 2 ; S2: The phenolic fiber needle-punched preform is immersed in a modification solution and then dried; the modified preform is obtained. The modified solution is a solution obtained by dissolving the coupling agent in an organic solvent; S3: A modified phenolic resin is prepared by stirring and mixing a hybrid phenolic resin, a toughening agent solution, and a surface heat dissipation agent; the mass ratio of the hybrid phenolic resin, the toughening agent solution, and the surface heat dissipation agent is 100:10-20:0.5-1; the toughening agent solution is a mixture of a toughening agent and an organic solvent; the toughening agent is one or more of polycaprolactone diol, polypropylene glycol, and polycarbonate diol. S4: A flexible composite material is obtained by molding a modified phenolic resin to impregnate the modified preform.

2. The molding method for an adaptive deformation flexible composite material according to claim 1, characterized in that, In step S1, the phenolic fiber is a chopped fiber with a length of 55-75 mm; The length of the hot-melt yarn is 35-40 mm, and the fineness is 2.3-3.2 dtex; The hot melt yarn is one or more of nylon hot melt yarn (PA), polyester hot melt yarn (PET), and polyethylene-polypropylene bicomponent core-sheath hot melt yarn (ES).

3. The molding method for an adaptive deformation flexible composite material according to claim 2, characterized in that, The mass ratio of the phenolic fiber to the hot melt yarn is 11-15:1-2.

4. The molding method for an adaptive deformation flexible composite material according to claim 1, characterized in that, In step S1, the needle density of the needle-punching process is 16-20 needles / cm. 2 .

5. The molding method for an adaptive deformation flexible composite material according to claim 1, characterized in that, In step S2, the coupling agent is one or more of isopropyl tris(dioctylphosphoyloxy)titanate, isopropyl tris(isostearoyl)titanate, and di(dioctylpyrophosphoyloxy)ethylenetitanate.

6. The molding method for an adaptive deformation flexible composite material according to claim 1, characterized in that, In step S3, the mass ratio of the hybrid phenolic resin, the toughening agent solution, and the surface heat dissipation agent is 100:11-19:0.5-1.

7. The molding method for an adaptive deformation flexible composite material according to claim 1, characterized in that, The surface heat dissipation agent is one or more of nano boron nitride, nano aluminum nitride, and nano aluminum oxide.

8. An adaptive deformation flexible composite material, characterized in that, It is obtained by the molding method according to any one of claims 1-7.

9. The adaptive deformation flexible composite material obtained by the molding method according to any one of claims 1-7 is used in a heat-resistant component.

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