Molding method of revolution-shaped needle-punched fabric composite material product

Abstract

The invention belongs to the technical field of composite materials, and provides a forming method of a revolution-shaped needle-punched fabric composite material product, which comprises the following steps: designing a needle-punched fabric and a mold, preparing and pre-curing a prepreg, putting the prepreg into the mold, and carrying out compression molding and demolding. The inner molded surface pressurizing mode of the revolution-shaped needle-punched fabric is designed, wrinkles of the inner molded surface of the product are avoided, meanwhile, impurities such as small molecules generated in the curing reaction process of resin can be greatly removed, the internal porosity of the composite material is reduced, and the internal quality of the product is improved. The problems that in the prior art, a liquid transfer molding forming process is small in forming pressure, low in efficiency and high in mold manufacturing cost are solved. Meanwhile, the problems that the inner molded surface of an autoclave molding process product has more wrinkles and the appearance and use requirements of a composite material component are difficult to meet are solved, and high-quality and low-cost preparation of the revolution-shaped needle-punched fabric composite material product is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of resin matrix composites, and particularly relates to a method for forming a rotary body-shaped needled fabric composite product. Background Art

[0002] A needled fabric is a non-woven material made by a needling process. Its core is to entangle and reinforce the fibers in the fiber web through mechanical action to form a fabric structure with a certain strength. The high-performance resin matrix composites prepared with needled fabrics as the reinforcement have moderate manufacturing costs and overcome the disadvantages of weak interlaminar shear strength of bulk molding compounds and fiber cloth laminated composites. At present, the forming and preparation processes of rotary body-shaped needled fabric reinforced resin matrix composites are relatively single, mainly including liquid transfer molding (RTM) and autoclave molding.

[0003] Song Ruokang et al. (Song Ruokang et al., "Preparation and Properties of Ablative Thermal Protection / Anti-Radar Multifunctional Composites", Acta Materiae Compositae Sinica, Vol. 41, January 2024) used needled quartz fiber fabrics as the reinforcement and traditional phenolic resin and new silicone resin as the matrix, and prepared two kinds of ablative thermal protection / anti-radar multifunctional composites by high-pressure resin transfer molding (HP-RTM) process, and studied the ablation / thermal protection / anti-radar properties.

[0004] Gao Wei et al. (Gao Wei et al., "Study on the Properties of RTM-Molded Needled Preform Reinforced Furfural Ketone Resin Ablative Composites", Fiberglass / Composites, July 2010) used carbon cloth / carbon mesh tire laminated needled preforms as the reinforcement and furfural ketone resin as the matrix, and prepared composites with good surface quality by RTM process, and tested and analyzed the mechanical properties and ablation properties of the composites.

[0005] The liquid transfer molding (RTM) process has the advantage of near-net size, but its main disadvantages are small molding pressure, low molding efficiency, and high mold manufacturing cost; the autoclave molding has the advantages of large molding pressure and batch molding, but its main disadvantage is that there are many wrinkles on the inner surface of the product, which affects the product quality and is difficult to meet the appearance and use requirements of composite components. Therefore, a compression molding method for rotary body-shaped needled fabric composite products is proposed. Summary of the Invention

[0006] Aiming at the deficiencies existing in the prior art, the present invention provides a method for forming a toroidal needle-punched fabric composite material product, which solves the problems of small forming pressure, low efficiency and high mold manufacturing cost in the existing liquid transfer molding (RTM) process; at the same time, it solves the technical problem that there are many wrinkles on the inner surface of the product in the autoclave forming process, making it difficult to meet the appearance and use requirements of composite material components. The method provided by the present invention can replace the traditional RTM process and the autoclave forming process with external surface pressurization, realizing the high-quality and low-cost preparation of toroidal needle-punched fabric composite material products.

[0007] The object of the present invention is achieved as follows: According to the structural characteristics of the large compressibility of the toroidal needle-punched fabric in the thickness direction, a method of pressurizing the inner surface of the toroidal needle-punched fabric is designed. Through the overall structural design of the forming mold and the needle-punched fabric, the size of the female mold surface is made consistent with the outer surface size of the needle-punched fabric, and the female mold surface serves as the pressure-bearing surface. The size of the male mold surface is larger than the inner surface size of the needle-punched fabric, and the male mold surface serves as the pressure-applying surface. Using the radial expansion pressure generated by the male mold closing downward and inserting into the inner surface of the needle-punched fabric prepreg, the prepreg is slowly compressed to the forming surface of the product, and then heat preservation and curing are carried out to obtain a toroidal needle-punched fabric composite material product. The difference from the existing RTM forming process and autoclave forming process is that: the pressure-applying surface of the method provided in this application is the inner surface of the product and the forming pressure is large, which avoids the generation of wrinkles on the inner surface of the product. At the same time, it can greatly remove impurities such as small molecules generated during the curing reaction of the resin, reduce the porosity inside the composite material, and improve the internal quality of the product.

[0008] To achieve the object of the present invention, the following technical solutions are specifically adopted:

[0009] A method for forming a toroidal needle-punched fabric composite material product, including needle-punched fabric and mold design, prepreg preparation and pre-curing, prepreg entering the mold, molding and demolding, and the specific steps are as follows:

[0010] S1. Needle-punched fabric and mold design

[0011] According to the outer shape size and volume density requirements of the product blank, the outer shape size and volume density of the toroidal needle-punched fabric are designed, so that the outer surface of the needle-punched fabric is consistent with the outer surface of the product blank. The wall thickness of the needle-punched fabric is thickened in proportion to the wall thickness of the product blank to meet the compression margin requirements of the needle-punched fabric. The thickening ratio value is 1.1 - 1.5, and the volume density of the needle-punched fabric is 0.4 g / cm 3 ~0.8 g / cm 3 ,as Figure 1 shown;

[0012] According to the outer dimension of the needle-punched fabric, the structure of the forming die is designed so that the size of the female die surface is the same as that of the outer surface of the needle-punched fabric. During the process of molding and curing under pressure, the outer diameter of the needle-punched fabric always remains unchanged; the size of the male die surface is larger than the inner surface size of the needle-punched fabric and is the same as the inner surface size of the product. The main purpose is that when the male die closes downward and inserts into the inner surface of the needle-punched fabric, it can generate a certain radial expansion pressure, so that the inner diameter of the needle-punched fabric is expanded by the male die to the inner diameter of the product The ratio range is 1.1 - 1.5, as Figure 2 shown;

[0013] S2. Preparation of prepreg and pre-curing

[0014] The resin is introduced into the needle-punched fabric by vacuum-assisted liquid infusion process to obtain a rotary-shaped needle-punched fabric prepreg. The prepreg is put into an oven for pre-curing treatment. The pre-curing treatment temperature is 50°C - 100°C, and the pre-curing treatment time is 0.5h - 1h to obtain a needle-punched fabric prepreg with a certain degree of crosslinking;

[0015] S3. Insertion of prepreg into the mold

[0016] The surface of the pre-cured needle-punched fabric prepreg is treated, and the treated prepreg is put into the female mold cavity for fitting, so that the outer surface of the prepreg is closely fitted with the female mold cavity. After the fitting is completed, the needle-punched fabric prepreg is taken out, the mold is heated up and a release agent is applied, and then the needle-punched fabric prepreg is put in; considering the design tolerance and the deformation of the fabric during the pre-impregnation process, the fitting is carried out to ensure the product forming quality

[0017] S4. Molding and demolding under pressure

[0018] After the mold cavity temperature rises to the pressurizing temperature of 100°C - 200°C, the mold is closed and pressed. The prepreg is slowly compressed by the radial expansion pressure generated by the downward movement of the male die. At the same time, observe the overflow state of the prepreg in the mold cavity, adjust the mold closing speed, and the mold closing speed is 10cm / min - 50cm / min until the mold closing is completed, pressurize to 10MPa - 30MPa, heat up to 150°C - 250°C, and keep warm for 0.5h - 1.5h for curing and forming. After the product is completely cured, slowly eject the product from the mold cavity and cool it naturally. Adjusting the mold closing speed can avoid excessive overflow or incomplete pressing, further ensuring the product quality.

[0019] Furthermore, in step S1, the rotary-shaped needle-punched fabric is a hollow frustum-shaped rotary-shaped needle-punched fabric, and the bulk density is 0.4g / cm 3 - 0.6g / cm 3 .

[0020] Furthermore, in step S1, the rotating body-shaped needle-punched fabric substrate is one or both of carbon fiber and glass fiber.

[0021] Preferably, in step S1, the wall thickness of the needle-punched fabric is increased in proportion to the wall thickness of the product blank, and the ratio is 1.1 to 1.3.

[0022] Furthermore, in step S1, the mold substrate is one of 45# steel, P20 steel, and H13 steel.

[0023] Furthermore, in step S2, the resin used in the resin vacuum-assisted liquid infusion process is one of phenolic resin and aromatic acetylene resin.

[0024] Preferably, in step S2, the pre-curing treatment temperature is 50°C to 70°C, and the pre-curing treatment time is 0.5h to 0.8h.

[0025] Preferably, in step S4, the pressurizing temperature is 100°C to 150°C, the molding pressure is 20MPa to 30MPa, the molding temperature is 150°C to 200°C, and the heat preservation time is 0.5h to 1h.

[0026] The mold used in the present invention can be designed with a conventional structure, has a simple structure, and has a surface size that satisfies the mold's negative model surface size and the needle-punched fabric's outer surface size, the positive model surface size is larger than the needle-punched fabric's inner surface size, and the positive model surface size is consistent with the product's inner surface size.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The method provided by the present invention replaces the traditional RTM process and the autoclave molding process with external surface pressurization, and solves the problems of low molding pressure and many wrinkles on the internal surface of the product in the existing molding process. The method of the present invention has the following characteristics:

[0029] 1. High molding pressure. The use of high-temperature presses and molds with internal pressure on the mold surface to press the product overcomes the disadvantages of low RTM molding pressure and many wrinkles in autoclave molding. Especially for phenolic resin matrix, high-pressure molding can eliminate small molecules generated by phenolic resin during the curing reaction as much as possible, reduce the internal porosity of the composite material, and improve the internal quality of the product.

[0030] 2. The molded surface of the product is smooth with few defects. The method of using the male mold to pressurize the inner surface of the prepreg instead of the external surface pressurization method such as the autoclave avoids the formation of wrinkles on the inner surface of the product. The smoothness of the inner surface of the product is almost the same as that of the outer surface of the male mold, with few defects.

[0031] 3. The production cost of the product is low. Compared with the RTM molding process, the production cycle of a single-piece product in the compression molding process is significantly shortened. At the same time, it replaces the high-energy-consuming autoclave molding process, reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the external shape of a rotary-shaped needled fabric related to the present invention

[0033] Figure 2 Schematic diagrams of a rotary-shaped needled fabric before and after compression related to the present invention

[0034] Figure 3 Schematic diagram of the mold structure of a rotary-shaped needled fabric related to the present invention

[0035] Figure 4 Figure 3 Cross-sectional view

[0036] Figure 5 Inner surface topography of the product formed by the compression molding method in Example 5

[0037] Figure 6 Inner surface topography of the product formed by the autoclave method in Comparative Example 2

[0038] Wherein: 1 - upper template, 2 - middle mold, 3 - lower template, 4 - male mold, 5 - pressure plate, 6 - needled fabric, 7 - product, 8 - female mold, 9 - top block, 10 - guide post, 11 - heating rod hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The technical solution of the present invention will be further described in detail below in conjunction with the drawings and specific embodiments, but it is not a limitation to the technical solution of the present invention. All raw materials used in the present invention are commercially available. The resin content of the needled fabric prepreg is tested according to GB / T32788.5 - 2016 for the product; the density of the needled fabric composite material is tested according to GB / T 1463 - 2005; the oxy - acetylene linear ablation rate of the needled fabric composite material is tested according to GJB 323A - 1996.

[0040] The mold used in the present invention includes an upper template 1, a middle mold 2, a lower template 3, and a male mold 4. The middle mold 2 is composed of a pressure plate 5, a female mold 8, a top block 9, and a guide post 10, as Figure 3 , Figure 4 shown. The upper template 1 is fixedly installed on the male mold 4, and the upper template 1 and the male mold 4 are connected to the upper bolster of the press through metal bolts and reciprocate up and down with the upper bolster of the press as the pressure - applying body; the lower template 3 is fixedly connected to the female mold 8, and the lower template 3 and the female mold 8 are connected to the lower bolster of the press through metal bolts and are fixed as the pressure - bearing body. One side of the upper template 1 and the lower template 3 is each machined with There are 4 through holes, and a total of 8 heating rods with a single heating power of 2 kW are placed. The cavity between the male mold 4 and the female mold 8 is the mold cavity, and the mold cavity matches the shape of the product. The forming surface of the male mold 4 is conical. The pressure plate 5 is a metal ring, which is detachable. Its outer shape matches the groove-shaped surface at the top of the female mold 8. During molding, it is placed at the groove at the top of the female mold 8, and its inner edge presses the outer edge of the needled fabric by 5 mm and is connected to the female mold 8 through 4 M10 bolts to lock the needled fabric in the female mold. The top block 9 is a movable unit. During molding, it is placed at the bottom of the female mold 8. The ejector rod of the press acts on the top block 9, and the top block 9 acts on the product to facilitate the smooth demolding of the product. The guide posts 10 are composed of the upper template guide posts and the lower template guide posts. The upper template guide posts are 4 metal rods with a diameter of 25 mm and a length of 200 mm, and the lower template guide posts are 4 metal rods with a diameter of 27 mm and a length of 300 mm. They are connected to the upper and lower templates through a tight fit and are evenly distributed on the upper and lower templates along the same axis to ensure the mold closing accuracy of the molding device. The fixed connection methods between the upper template 1 and the male mold 4, the lower template 3 and the female mold 8, and the pressure plate 5 and the female mold 8 can also adopt welding, riveting, etc.

[0041] To better understand the beneficial effects of the method involved in the present invention, Comparative Example 1 and Comparative Example 2 are provided. Compared with Example 5, the raw materials used are the same, and the traditional RTM molding process and autoclave molding process are respectively used to prepare the rotary body needled fabric products.

[0042] Example 1

[0043] A method for molding a rotary body needled fabric composite product includes the following steps:

[0044] S1. Needled fabric and mold design

[0045] According to the outer shape size and volume density requirements of the product blank, the outer shape size and volume density of the rotary body needled fabric are designed so that the outer surface of the needled fabric is consistent with the outer surface of the product blank. The wall thickness of the needled fabric is thickened in proportion to the wall thickness of the product blank, and the proportional value is 1.5. The substrate of the needled fabric is carbon fiber, and the volume density of the needled fabric is 0.6 g / cm 3 ;

[0046] According to the outer shape size of the needled fabric, the structure of the molding mold is designed. The substrate of the mold is P20 steel, so that the size of the female mold cavity is consistent with the outer surface size of the needled fabric, and the size of the male mold cavity is consistent with the inner surface size of the product;

[0047] S2. Prepreg preparation and pre-curing

[0048] The phenolic resin is introduced into the needled fabric by the vacuum-assisted liquid infusion process to obtain the rotary body needled fabric prepreg. The prepreg is placed in an oven for pre-curing treatment. The pre-curing treatment temperature is 50 °C, and the pre-curing treatment time is 8 h to obtain the needled fabric prepreg with a certain degree of crosslinking;

[0049] S3. Pre-impregnated material into the mold

[0050] Trim the outer surface of the pre-cured needled fabric pre-impregnated material to remove redundant dimensions and excess burrs on the outer surface of the pre-impregnated material. Place the processed pre-impregnated material into the female mold cavity for fitting, so that the outer surface of the pre-impregnated material fits tightly with the female mold cavity. After the fitting is completed, take out the needled fabric pre-impregnated material, heat up the mold and apply a release agent, and then put the needled fabric pre-impregnated material in;

[0051] S4. Compression molding and demolding

[0052] After the mold cavity temperature rises to the pressurizing temperature of 150 °C, close the mold for pressing. Use the radial expansion pressure generated by the male mold downward to slowly compress the pre-impregnated material. At the same time, observe the overflow state of the pre-impregnated material in the mold cavity, adjust the mold closing speed to 10 cm / min until the mold closing is completed, pressurize to 20 MPa, heat up to 200 °C, and keep warm for 0.5 h for curing and forming. After the product is completely cured, slowly eject the product from the mold cavity and cool it naturally to obtain a rotary-shaped needled fabric composite product. The performance test results are shown in Table 1.

[0053] Example 2

[0054] A method for compression molding a rotary-shaped needled fabric composite product, comprising the following steps:

[0055] S1. Needled fabric and mold design

[0056] According to the requirements of the blank shape size and volume density of the product, design the outer shape size and volume density of the rotary-shaped needled fabric, so that the outer surface of the needled fabric is consistent with the outer surface of the product blank. The wall thickness of the needled fabric is thickened in proportion to the wall thickness of the product blank, and the proportional value is 1.3. The substrate of the needled fabric is glass fiber, and the volume density of the needled fabric is 0.8 g / cm 3 ;

[0057] According to the outer shape size of the needled fabric, design the structure of the molding mold. The substrate of the mold is H13 steel, so that the size of the female mold surface is consistent with the outer surface size of the needled fabric, and the size of the male mold surface is consistent with the inner surface size of the product;

[0058] S2. Pre-impregnated material preparation and pre-curing

[0059] Use the vacuum-assisted liquid infusion process to introduce the aryl acetylene resin into the needled fabric to obtain a rotary-shaped needled fabric pre-impregnated material. Place the pre-impregnated material in an oven for pre-curing treatment. The pre-curing treatment temperature is 100 °C, and the pre-curing treatment time is 1 h to obtain a needled fabric pre-impregnated material with a certain degree of cross-linking;

[0060] S3. Pre-impregnated material into the mold

[0061] Trim the outer surface of the pre-cured needle-punched fabric prepreg to remove redundant prepreg size, excess burrs on the outer surface, etc. Place the treated prepreg into the female mold cavity for fitting, so that the outer surface of the prepreg fits tightly with the female mold cavity. After the fitting is completed, take out the needle-punched fabric prepreg, heat up the mold and apply a release agent, and then put in the needle-punched fabric prepreg;

[0062] S4. Compression molding and demolding

[0063] After the mold cavity temperature rises to the pressurization temperature of 200 °C, close the mold for pressing. Use the radial expansion pressure generated by the male mold to slowly compress the prepreg. At the same time, observe the overflow state of the prepreg in the mold cavity, adjust the mold closing speed to 50 cm / min until the mold closing is completed, pressurize to 10 MPa, heat up to 250 °C, and keep warm for 1.5 h for curing and forming. After the product is completely cured, slowly eject the product from the mold cavity and cool it naturally to obtain a rotary-shaped needle-punched fabric composite product. The performance test results are shown in Table 1.

[0064] Example 3

[0065] A method for compression molding a rotary-shaped needle-punched fabric composite product includes the following steps:

[0066] S1. Needle-punched fabric and mold design

[0067] According to the requirements of the blank shape size and volume density of the product, design the outer shape size and volume density of the rotary-shaped needle-punched fabric so that the outer surface of the needle-punched fabric is consistent with the outer surface of the product blank. The wall thickness of the needle-punched fabric is thickened in proportion to the wall thickness of the product blank, and the proportional value is 1.1. The needle-punched fabric substrate is glass fiber, and the volume density of the needle-punched fabric is 0.4 g / cm 3 ;

[0068] According to the outer shape size of the needle-punched fabric, design the structure of the molding mold. The mold substrate is 45# steel, so that the size of the female mold surface is consistent with the size of the outer surface of the needle-punched fabric, and the size of the male mold surface is consistent with the size of the inner surface of the product;

[0069] S2. Prepreg preparation and pre-curing

[0070] Use the vacuum-assisted liquid infusion process to introduce phenolic resin into the needle-punched fabric to obtain a rotary-shaped needle-punched fabric prepreg. Place the prepreg in an oven for pre-curing treatment. The pre-curing treatment temperature is 70 °C, and the pre-curing treatment time is 0.5 h to obtain a needle-punched fabric prepreg with a certain degree of crosslinking;

[0071] S3. Prepreg into the mold

[0072] Trim the outer surface of the pre-cured needle-punched fabric prepreg to remove redundant prepreg size, excess burrs on the outer surface, etc. Place the treated prepreg into the female mold cavity for fitting to make the outer surface of the prepreg closely fit the female mold cavity. After the fitting is completed, take out the needle-punched fabric prepreg, heat up the mold and apply a release agent, and then place the needle-punched fabric prepreg into it.

[0073] S4. Compression molding and demolding

[0074] After the mold cavity temperature rises to the pressurization temperature of 100 °C, close the mold for pressing. Use the radial expansion pressure generated by the male mold to slowly compress the prepreg. At the same time, observe the overflow state of the prepreg in the mold cavity, adjust the mold closing speed to 30 cm / min until the mold closing is completed, pressurize to 30 MPa, heat up to 150 °C, and keep warm for 1 h for curing and forming. After the product is completely cured, slowly eject the product from the mold cavity and cool it naturally to obtain a rotary body-shaped needle-punched fabric composite product. The performance test results are shown in Table 1.

[0075] Example 4

[0076] A method for compression molding a rotary body-shaped needle-punched fabric composite product includes the following steps:

[0077] S1. Needle-punched fabric and mold design

[0078] According to the requirements of the blank shape size and volume density of the product, design the outer shape size and volume density of the rotary body-shaped needle-punched fabric so that the outer surface of the needle-punched fabric is consistent with the outer surface of the product blank. The wall thickness of the needle-punched fabric is thickened proportionally according to the wall thickness of the product blank, and the proportional value is 1.2. The needle-punched fabric substrate is carbon fiber, and the volume density of the needle-punched fabric is 0.7 g / cm 3 ;

[0079] According to the outer shape size of the needle-punched fabric, design the structure of the molding mold. The mold substrate is H13 steel, so that the size of the female mold surface is consistent with the size of the outer surface of the needle-punched fabric, and the size of the male mold surface is consistent with the size of the inner surface of the product;

[0080] S2. Preparation and pre-curing of prepreg

[0081] Use the vacuum-assisted liquid infusion process to introduce aryl acetylene resin into the needle-punched fabric to obtain a rotary body-shaped needle-punched fabric prepreg. Place the prepreg into an oven for pre-curing treatment. The pre-curing treatment temperature is 90 °C, and the pre-curing treatment time is 0.9 h to obtain a needle-punched fabric prepreg with a certain degree of cross-linking;

[0082] S3. Insertion of prepreg into the mold

[0083] Trim the outer surface of the pre-cured needled fabric prepreg to remove redundant prepreg size, excess burrs on the outer surface, etc. Place the treated prepreg into the female mold cavity for fitting to make the outer surface of the prepreg closely fit the female mold cavity. After the fitting is completed, take out the needled fabric prepreg, heat up the mold and apply a release agent, and then put the needled fabric prepreg back in.

[0084] S4. Compression molding and demolding

[0085] After the mold cavity temperature rises to the pressurizing temperature of 180 °C, close the mold for pressing. Use the radial expansion pressure generated by the male mold pressing downwards to slowly compress the prepreg. At the same time, observe the overflow state of the prepreg in the mold cavity, adjust the mold closing speed to 20 cm / min until the mold closing is completed, pressurize to 25 MPa, heat up to 230 °C, and keep warm for 1.3 h for curing and forming. After the product is completely cured, slowly eject the product from the mold cavity and let it cool naturally to obtain a rotary-shaped needled fabric composite product. The performance test results are shown in Table 1.

[0086] Example Five

[0087] A method for compression molding a rotary-shaped needled fabric composite product includes the following steps:

[0088] S1. Needled fabric and mold design

[0089] According to the requirements of the blank shape size and volume density of the product, design the outer shape size and volume density of the rotary-shaped needled fabric so that the outer surface of the needled fabric is consistent with the outer surface of the product blank. The wall thickness of the needled fabric is thickened in proportion to the wall thickness of the product blank, and the proportional value is 1.4. The substrate of the needled fabric is carbon fiber, and the volume density of the needled fabric is 0.5 g / cm 3 ;

[0090] According to the outer shape size of the needled fabric, design the structure of the molding mold. The substrate of the mold is P20 steel, so that the size of the female mold surface is consistent with the size of the outer surface of the needled fabric, and the size of the male mold surface is consistent with the size of the inner surface of the product;

[0091] S2. Prepreg preparation and pre-curing

[0092] Use the vacuum-assisted liquid infusion process to introduce phenolic resin into the needled fabric to obtain a rotary-shaped needled fabric prepreg. Place the prepreg in an oven for pre-curing treatment. The pre-curing treatment temperature is 60 °C, and the pre-curing treatment time is 0.7 h to obtain a needled fabric prepreg with a certain degree of crosslinking;

[0093] S3. Inserting the prepreg into the mold

[0094] Trim the outer surface of the pre-cured needle-punched fabric prepreg to remove redundant prepreg size, excess burrs on the outer surface, etc. Place the treated prepreg into the female mold cavity for fitting, so that the outer surface of the prepreg fits tightly with the female mold cavity. After the fitting is completed, take out the needle-punched fabric prepreg, heat up the mold and apply a release agent, and then place the needle-punched fabric prepreg into it.

[0095] S4. Compression molding and demolding

[0096] After the mold cavity temperature rises to the pressurizing temperature of 130 °C, close the mold for pressing. Use the radial expansion pressure generated by the male mold to slowly compress the prepreg. At the same time, observe the overflow state of the prepreg in the mold cavity, adjust the mold closing speed to 40 cm / min until the mold closing is completed, pressurize to 15 MPa, heat up to 180 °C, and keep warm for 0.7 h for curing and forming. After the product is completely cured, slowly eject the product from the mold cavity and cool it naturally to obtain a rotary body needle-punched fabric composite product. The performance test results are shown in Table 1, and the morphology of the forming surface of the rotary body needle-punched fabric composite product is shown in Figure 5 .

[0097] Comparative Example 1

[0098] A method for forming a rotary body needle-punched fabric composite product by RTM molding includes the following steps:

[0099] S1. Needle-punched fabric and mold design

[0100] Design the outer dimensions of the rotary body needle-punched fabric according to the blank shape dimensions of the product. The needle-punched fabric substrate is carbon fiber, and the bulk density of the needle-punched fabric is 0.5 g / cm 3 ;

[0101] According to the outer dimensions of the needle-punched fabric, design the structure of the RTM molding mold. The mold substrate is P20 steel, so that the dimensions of the female mold surface are the same as those of the outer surface of the needle-punched fabric, and the dimensions of the male mold surface are the same as those of the inner surface of the needle-punched fabric;

[0102] S2. Insert the needle-punched fabric into the mold

[0103] Heat up the RTM mold and apply a release agent. Place the needle-punched fabric into the RTM mold for fitting. After the fitting is completed, close the mold and evacuate to check the sealing performance of the RTM mold, so that the vacuum degree of the RTM mold cavity is maintained below -0.095 MPa.

[0104] S3. Resin infusion and curing and forming

[0105] Connect the pipeline between the RTM injection tank and the RTM mold, and evacuate the gas in the pipeline by vacuum. Heat the RTM mold to 80 °C, then open the perfusion valve to introduce phenolic resin into the needled fabric. After perfusion, close the valve, heat the RTM mold to 180 °C, and keep it warm for 0.7 h for curing and forming. After the product is completely cured, take the product out of the mold cavity and cool it naturally to obtain a rotary-shaped needled fabric composite product. The performance test results are shown in Table 1.

[0106] Comparative Example 2

[0107] A method for autoclave molding of a rotary-shaped needled fabric composite product, comprising the following steps:

[0108] S1. Design of needled fabric and mold

[0109] Design the outer dimension of the rotary-shaped needled fabric according to the outer dimension of the product blank. The base material of the needled fabric is carbon fiber, and the volume density of the needled fabric is 0.5 g / cm 3 ;

[0110] According to the outer dimension of the needled fabric, design the structure of the autoclave molding mold. The base material of the mold is P20 steel, so that the size of the male mold surface is consistent with the inner surface size of the needled fabric;

[0111] S2. Preparation and pre-curing of prepreg

[0112] Use the vacuum-assisted liquid infusion process to introduce phenolic resin into the needled fabric to obtain a rotary-shaped needled fabric prepreg. Put the prepreg into an oven for pre-curing treatment. The pre-curing treatment temperature is 60 °C, and the pre-curing treatment time is 0.7 h to obtain a needled fabric prepreg with a certain degree of crosslinking;

[0113] S3. Vacuum bag coating of prepreg

[0114] Heat up the autoclave molding mold and apply a release agent. Put the needled fabric prepreg on the autoclave molding mold, and successively cover the release cloth, absorbent felt, and vacuum bag on the outer surface of the prepreg. Evacuate the air to check the sealing performance of the vacuum bag system, so that the system vacuum degree is kept below -0.095 MPa.

[0115] S4. Loading into the autoclave and curing and forming

[0116] Put the prepreg wrapped with the vacuum bag into the autoclave, set and start the heating program and the pressure boosting program for autoclave curing and forming. After the product is completely cured, take the product out of the autoclave and cool it naturally to obtain a rotary-shaped needled fabric composite product. The performance test results are shown in Table 1.

[0117] Table 1 Performance of rotary-shaped needled fabric composite products

[0118]

[0119] It can be seen from the analysis of the data of the examples and comparative examples in Table 1 that the oxygen-acetylene linear ablation rate of the rotary-shaped needled fabric composite products prepared by the molding method (Examples 1 to 5) is approximately between 0.011 mm / s and 0.028 mm / s, the molding surface is smooth, and excellent ablation and erosion resistance performance is exhibited.

[0120] The oxygen-acetylene linear ablation rate of the rotary-shaped needled fabric composite product prepared by the RTM molding method (Comparative Example 1) is 0.055 mm / s. Although the molding surface is smooth, due to the relatively small molding pressure and the relatively large content of small molecules, the ablation and erosion resistance performance decreases significantly.

[0121] Comparison of the molding surface morphologies of the rotary-shaped needled fabric composite products prepared by the molding method and the autoclave molding method is as Figure 5 、 Figure 6 shown. The oxygen-acetylene linear ablation rate of the rotary-shaped needled fabric composite product prepared by the autoclave molding method (Comparative Example 2) is 0.017 mm / s, but there are many wrinkles on the molding surface, which does not meet the requirements of the ablation surface of the product.

[0122] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for forming a rotating body-shaped needle-punched fabric composite product, comprising needle-punched fabric and mold design, prepreg preparation and precuring, prepreg mold insertion, compression molding and demoulding, characterized in that: The specific steps are as follows: S1. Needle-punched fabric and mold design According to the requirements of the product blank's outer dimensions and volume density, the outer dimensions and volume density of the rotating body needle-punched fabric are designed so that the outer surface of the needle-punched fabric is consistent with the outer surface of the product blank. The wall thickness of the needle-punched fabric is thickened in proportion to the wall thickness of the product blank. The thickening ratio is 1.1-1.5, and the volume density of the needle-punched fabric is 0.4g / cm 3 ~0.8g / cm 3 ; According to the outer dimensions of the needle-punched fabric, the forming mold cavity is designed so that the size of the female mold surface is consistent with the outer surface size of the needle-punched fabric, and the size of the male mold surface is larger than the inner surface size of the needle-punched fabric and consistent with the inner surface size of the product; S2. Prepreg preparation and precuring The resin is introduced into the needle-punched fabric by using a vacuum-assisted liquid infusion process to obtain a rotational body-shaped needle-punched fabric prepreg; the prepreg is placed in an oven for pre-curing treatment to obtain a needle-punched fabric prepreg with a certain degree of cross-linking; S3. Prepreg into mold The pre-cured needle-punched fabric prepreg is subjected to surface shaping treatment, and the treated needle-punched fabric prepreg is placed in the negative mold cavity of the mold for fitting, so that the outer surface of the needle-punched fabric prepreg is closely fitted with the negative mold cavity; After the adaptation is completed, the needle-punched fabric prepreg is taken out, the mold is heated up and a release agent is applied, and then the needle-punched fabric prepreg is placed; S4, compression molding and demoulding After the mold cavity temperature rises to the pressurization temperature point, the mold is closed and pressed, and the mold closing rate is adjusted. After the mold is closed, pressurization and temperature curing are performed, and a rotating body-shaped needle-punched fabric composite material product is obtained after demoulding.

2. The method for forming a rotating body-shaped needle-punched fabric composite product according to claim 1, characterized in that: The rotatable needle-punched fabric in S1 is a hollow truncated cone rotatable needle-punched fabric with a bulk density of 0.4 g / cm 3 ~0.6g / cm 3 .

3. The method for forming a rotating body-shaped needle-punched fabric composite product according to claim 1, characterized in that: The rotating body-shaped needle-punched fabric substrate in S1 is one or both of carbon fiber and glass fiber.

4. The method for forming a rotating body-shaped needle-punched fabric composite product according to claim 1, characterized in that: The wall thickness of the needle-punched fabric in S1 is increased in proportion to the wall thickness of the product blank, and the ratio is 1.1 to 1.

3.

5. The method for forming a rotational body-shaped needle-punched fabric composite product according to claim 1, characterized in that: The mold base material in S1 is one of 45# steel, P20 steel, and H13 steel.

6. The method for forming a rotational body-shaped needle-punched fabric composite material product according to claim 1, characterized in that: The resin in S2 is one of phenolic resin and aromatic acetylene resin.

7. The method for forming a rotational body-shaped needle-punched fabric composite material product according to claim 1, characterized in that: The pre-curing treatment temperature in S2 is 50° C. to 100° C., and the pre-curing treatment time is 0.5 h to 1 h.

8. The method for forming a rotational body-shaped needle-punched fabric composite product according to claim 7, characterized in that: The pre-curing treatment temperature in S2 is 50° C. to 70° C., and the pre-curing treatment time is 0.5 h to 0.8 h.

9. The method for forming a rotational body-shaped needle-punched fabric composite material product according to claim 1, characterized in that: In the S4, the pressurizing temperature point is 100°C to 200°C, the molding pressure is 10MPa to 30MPa, the molding temperature is 150°C to 250°C, the heat preservation is 0.5h to 1.5h, and the mold closing speed is 10cm / min to 50cm / min.

10. The method for forming a rotational body-shaped needle-punched fabric composite material product according to claim 9, characterized in that: In the S4, the pressurizing temperature point is 100°C to 150°C, the molding pressure is 20MPa to 30MPa, the molding temperature is 150°C to 200°C, the heat preservation is 0.5h to 1h, and the mold closing rate is 10cm / min to 40cm / min.

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