A flexible cushioning material and its preparation method and application

Abstract

The present application relates to a kind of flexible cushioning material and its preparation method and application, belong to shock-absorbing material technical field, solve the uneven pressure transmission in prior art, insufficient pressure conduction, pressurization interface and the interface contact of material to be handled is not close, easily damaged material to be handled, poor wear resistance, elasticity and ductility is not good one of the problems.The present application discloses a kind of flexible cushioning material, the flexible cushioning material has the three-layer structure of sequentially laminated flexible rubber layer, fiber reinforced composite sandwich core, wear-resistant rubber layer;Wherein, the fiber reinforced composite sandwich core includes multiple gradient density units.The flexible cushioning material wear resistance, elasticity is excellent, realizes the high-quality pressurization bonding for easily damaged material, under the premise of guaranteeing pressure transmission uniform, interface contact closely, pressure conduction standard, to material to be handled plays certain protection.

Description

Technical Field

[0001] The present invention relates to the technical field of shock-absorbing materials, and in particular to a flexible buffer material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the aerospace industry, there is an urgent need for materials that are lightweight, high-temperature resistant, and high-load-bearing. In order to achieve the greatest weight reduction while meeting the service environment requirements of high-temperature resistant, load-bearing, and heat-resistant integration, external heat-resistant materials and load-bearing structural materials are generally used to form load-bearing and heat-resistant integrated composite components to protect the internal components of the aircraft. Due to their different functions, the external heat-resistant layer and the load-bearing layer have different material characteristics. The external heat-resistant layer uses lightweight insulation materials with low density, soft and brittle texture, and poor impact and compression resistance. The load-bearing layer uses high-temperature resistant resin-based composite materials with high specific strength and stiffness, and is prone to deformation. Therefore, the mode of action and transmission effect of molding pressure during the composite molding process of the two are crucial to the molding quality of the component.

[0003] The existing lamination process used to composite the two components can easily cause structural damage and uneven bonding. Even with the use of cushioning materials as a protective measure, these materials are not compatible with the special materials of the outer heat shield, resulting in uneven pressure transmission, which can affect the internal molding quality of the component and even damage the material itself. Summary of the Invention

[0004] In view of the above analysis, the embodiments of the present invention aim to provide a flexible buffer material and its preparation method and application, so as to solve one of the problems of existing buffer materials, namely, insufficient wear resistance, poor elasticity and ductility, poor pressure conduction performance, and easy damage to the material to be processed.

[0005] The present invention discloses a flexible buffer material, characterized in that: the flexible buffer material has a three-layer structure stacked in the order of a flexible rubber layer 1, a fiber-reinforced composite sandwich core, and a wear-resistant rubber layer 5;

[0006] Wherein, the fiber reinforced composite sandwich core comprises multiple gradient density units.

[0007] Specifically, the fiber-reinforced composite sandwich core is made of a fiber preform and resin.

[0008] Specifically, the fiber preform is composed of one or more of inorganic glass fiber, quartz fiber, carbon fiber, phenolic fiber, glass fiber, mullite fiber or alumina fiber.

[0009] Specifically, the resin is one or more of thermoplastic phenolic resin, thermosetting phenolic resin, organosilicon-modified phenolic resin, boron phenolic resin, and polyarylacetylene resin.

[0010] Specifically, the density is lowest at the junction of the fiber-reinforced composite sandwich core and the flexible rubber layer 1 , and the density is highest at the junction of the fiber-reinforced composite sandwich core and the wear-resistant rubber layer 5 .

[0011] Specifically, the total thickness of the flexible buffer material is 0.6-1.0 mm, wherein the thicknesses of the flexible rubber layer 1 and the wear-resistant rubber layer 5 are respectively 0.15-0.25 mm, and the thickness of the fiber-reinforced composite sandwich core is 0.3-0.5 mm.

[0012] The present invention also discloses a method for preparing the flexible cushioning material according to any one of claims 1 to 6, comprising the following steps:

[0013] S1: prepare flexible rubber sheet;

[0014] S2: Fiber preforms of different volume densities are prepared, cut to appropriate sizes, and stacked in order of volume density to form a gradient reinforcement; resin is diluted with a solvent, injected into the gradient reinforcement, and dried to obtain a fiber-reinforced composite sandwich core;

[0015] S3: Prepare wear-resistant rubber sheet;

[0016] S4: placing the cut flexible rubber sheet, the fiber-reinforced composite sandwich core, and the wear-resistant rubber sheet in a vulcanization mold in sequence, and obtaining a flexible cushioning material after vulcanization and demoulding.

[0017] Specifically, the step S2 includes: diluting the resin with a solvent to a mass concentration of 10-50%, controlling the injection pressure to 0.01-0.15 MPa, and injecting the diluted resin into the gradient reinforcement body.

[0018] The present invention also discloses a tool for integrally forming a composite component, the tool consisting of an upper mold, a buffer pad, and a bottom mold, wherein the buffer pad is made of the flexible buffer material described in any one of claims 1 to 6 or the flexible buffer material prepared by the preparation method described in any one of claims 7 to 8.

[0019] The present invention also discloses an application of the tooling, which is used to realize the integrated molding of composite components through the steps of material surface treatment, adhesive coating, pressurization and curing, and demoulding.

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0021] 1. The buffer material provided by the present application has uniform and sufficient pressure transmission and is not easy to damage the material. The buffer material provided by the present application adopts a sandwich structure of a flexible rubber layer, a gradient fiber reinforced composite sandwich core and a wear-resistant rubber layer. A better pressure transmission effect is provided by the multiple gradient density units. When the system is affected by external pressure changes, the changed pressure can be transmitted to the fiber reinforced composite sandwich core through the flexible rubber layer. The preform sandwich produces a certain degree of deformation and absorbs part of the impact energy, so that the pressure in the system is reasonably dispersed, thereby playing a pressure buffering role. If the pressure in the system suddenly changes or there is pulsation, and the mutation reaches the upper limit of damage to the outer thermal protection layer, since the density gradient fiber reinforced composite sandwich core adopts the same fiber weaving structure as the outer thermal protection layer, the low density unit is preferentially destroyed, thereby protecting the material body. For example, when the material quality (fiber and resin type) of the sandwich core and the material to be processed are the same, and the density gradient distribution of the sandwich core is 0.4-1.0 g / cm 3 , the outer thermal protection layer material (material to be processed) with a density greater than 0.4 g / cm 3 can be protected; if the density of the outer thermal protection layer is 0.4-1.0 g / cm 3 , the protection can fully conduct the pressure, and the buffering effect is better.

[0022] 2. The buffer material provided by the present application can be arranged between the equipment and the material to be processed, thereby fully ensuring that the equipment interface and the material to be processed are in full contact. The buffer material can also regulate the thickness of the equipment / tool cavity, thereby ensuring that the bonding surface is in full contact and is uniformly stressed, and solving the problem of poor bonding effect caused by insufficient contact and air gap between the bonding surfaces. For example, when preparing a load protection integrated composite component, the thickness tolerance of the outer thermal protection layer and the load layer itself can be compensated.

[0023] 3. The buffer material provided by the present application adopts a sandwich structure of a flexible rubber layer, a gradient fiber reinforced composite sandwich core and a wear-resistant rubber layer, and has high elasticity, large deformation, wear resistance and certain vulnerability (good protection for the material body). Therefore, the buffer material has high safety, applicability and durability.

[0024] In the present application, the above technical solutions can be combined with each other to realize more preferred combination solutions. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification or will be understood by implementing the present application. The purpose and other advantages of the present application can be realized and obtained from the contents specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and are not intended to limit the scope of the application, and the same reference numerals designate the same elements throughout the drawings.

[0026] Figure 1 Schematic diagram of flexible cushioning material structure (3-layer fiber preform)

[0027] Figure 2 Schematic diagram of tooling structure for integrally forming a composite component

[0028] Figure 3 Flow chart of method for integrally forming a heat-resistant load-bearing composite component.

[0029] Reference signs:

[0030] 1-flexible rubber layer; 2-first density unit (first layer of fiber preform); 3-second density unit (second layer of fiber preform); 4-third density unit (third layer of fiber preform); 5-abrasion-resistant rubber layer; 6-bottom mold; 7-edge pressing stop block; 8-wedge positioning block; 9-bearing layer; 10-outer heat-resistant layer; 11-cushion pad; 12-top mold; 13-positioning screw. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present application will be described in detail below with reference to the drawings, which form a part of this specification, and together with the embodiments of the present application illustrate the principles of the present application, but are not intended to limit the scope of the present application.

[0032] The present application discloses a flexible cushioning material, having a three-layer structure of flexible rubber layer, fiber-reinforced composite sandwich core, and abrasion-resistant rubber layer, in order; wherein the fiber-reinforced composite sandwich core comprises multiple gradient density units.

[0033] Specifically, the fiber-reinforced composite sandwich core is made of a fiber preform and a resin, and is a pre-solidified material with a density gradient gradually changing from the fiber preform and the resin.

[0034] In use, the flexible rubber layer of the flexible cushioning material of the present application is in contact with an adhesive device (pressurizing device or tooling, etc.), for transmitting the pressure of the device to the fiber-reinforced composite sandwich core with a density gradient and then to the product, playing a role of preliminary pressure buffering and transmission.

[0035] The fiber-reinforced composite sandwich core with a density gradient comprises multiple gradient density units, thus providing a better pressure transmission effect. When affected by external pressure changes, the composite sandwich core deforms to a certain extent, absorbs part of the impact energy, so that the pressure in the system is reasonably dispersed, playing a role of pressure buffering.

[0036] In actual use, the cushioning material can be made of a fiber reinforced composite sandwich core body with the same or similar weaving structure and material (fiber type and resin type) as the material to be treated. Since the two have similar composition and structure, the structural strength and density are positively correlated. When the external pressure exceeds a certain limit, the low-density unit of the fiber reinforced composite sandwich core body will be damaged first, thereby providing better protection to the material body.

[0037] For example, when the fiber reinforced composite sandwich core body has the same or similar structure and material (fiber and resin type) as the material to be treated, the density gradient distribution of the fiber reinforced composite sandwich core body is 0.4-1.0 g / cm 3 . If the three-layer density unit structure has three layers of density units with increasing or decreasing density, the density of the three layers can be 0.4, 0.7, and 1.0 g / cm 3 , respectively. In this case, the outer heat protection layer material (material to be treated) with a density greater than 0.4 g / cm 3 can be protected. If the density of the outer heat protection layer is 0.4-1.0 g / cm 3 , the protection can be provided while the pressure can be fully transmitted, and the cushioning effect is better. If the pressure in the system suddenly changes or has pulsation and suddenly changes to the upper limit of damage of the outer heat protection layer, since the fiber reinforced composite sandwich core body with a density gradient has the same weaving structure as the outer heat protection layer, the low-density unit is damaged first, thereby providing better protection to the material body, and thus having high safety, applicability, and durability.

[0038] The wear-resistant rubber layer has excellent wear resistance and long service life, and can withstand long-time friction without being easily worn.

[0039] Specifically, the fiber preform is composed of one or more of inorganic glass fiber, quartz fiber, carbon fiber, phenolic fiber, glass fiber, mullite fiber, or alumina fiber. The above fibers are common fibers for special materials in the field of aerospace thermal protection.

[0040] Specifically, the resin is one or more of thermoplastic phenolic resin, thermosetting phenolic resin, silicone modified phenolic resin, boron phenolic resin, and polyarylacetylene resin. The above resins are common resins for special materials in the field of aerospace thermal protection.

[0041] The combination of the fiber preform and the resin can cover most of the composition systems of aerospace special outer heat protection materials, the fiber reinforced composite interlayer core formed by the combination has a similar structure to most of the aerospace special outer heat protection materials, and thus has similar force transmission performance and similar structural strength in a similar density range, thereby playing a better stress buffering role between the bonding equipment and the outer heat protection layer, avoiding the problem of damage to the outer heat protection layer due to excessive local stress, fully playing a pressure transmission and product protection role, and improving product quality and qualification rate.

[0042] Specifically, the density of the fiber reinforced composite interlayer core is the lowest at the interface with the flexible rubber layer, and the density of the fiber reinforced composite interlayer core is the highest at the interface with the wear-resistant rubber layer. The flexible buffer material described below is in the order from top to bottom, the flexible rubber layer, the fiber reinforced composite interlayer core, and the wear-resistant rubber layer.

[0043] The fiber reinforced composite interlayer core has a density decreasing gradient in the thickness direction (i.e., the lowest density unit is at the interface between the flexible rubber layer and the fiber reinforced composite interlayer core), which is realized by the multiple density units of the fiber preform. The fiber preform includes n density units in the thickness direction, where n≥3. The density difference between adjacent density units can be determined according to actual needs, and is preferably uniformly distributed within the selected density range, such as a density difference Δρ=0.3 g / cm 3 In an ideal case, i.e., n is infinite, the density difference between adjacent density units is infinitely small, and the technical effect is best. However, this is not possible in actual implementation. Therefore, the density difference between adjacent density units should be determined comprehensively according to the thickness of the fiber reinforced composite interlayer core and the thickness of the selected single-layer density unit. In general, the larger n is, the better the buffering performance and pressure transmission performance are.

[0044] Through the density gradient design, on the one hand, the pressure transmission process is gradually buffered layer by layer, thereby achieving better pressure transmission effect. On the other hand, the low-density unit has certain damage protection characteristics. If the pressure in the system suddenly changes or has pulsation and suddenly changes to the upper limit of damage to the outer heat protection layer, the low-density unit is preferentially destroyed due to the density gradient fiber reinforced composite interlayer core adopting the same fiber weaving structure as the outer heat protection layer, thereby playing a protection role.

[0045] In fact, the fiber reinforced composite interlayer core also has a certain buffering function in the thickness direction with a density increasing gradient (i.e., the highest density unit is at the interface between the flexible rubber layer and the fiber reinforced composite interlayer core), but the buffering effect is slightly worse.

[0046] Specifically, the total thickness of the flexible buffer material is 0.6-1.0 mm, the thickness of the flexible rubber layer and the wear-resistant rubber layer is 0.15-0.25 mm respectively, and the thickness of the fiber reinforced composite interlayer core is 0.3-0.5 mm.

[0047] One important application scenario of the flexible cushioning material disclosed in the present application is the preparation of aerospace special composite components. By pressure bonding of the outer heat-proof layer and the load-bearing layer, a heat-proof load-bearing integrated composite component is prepared. The total thickness tolerance of the component is generally not more than 0.6 mm. In order to ensure the uniformity of pressure transmission and the full adhesion of the equipment interface and the material interface, the thickness of the cushioning material should not be less than the size of the total tolerance of the material to be processed, i.e. 0.6 mm. In addition, the thickness of the cushioning material should not be too thick. According to practical experience, it is appropriate to be not more than 1 mm.

[0048] Preferably, in order to fully ensure the sufficiency of pressure conduction and take into account the protection of the material to be processed, the thickness of the fiber-reinforced composite sandwich core should be not less than twice the thickness of the flexible rubber layer or the wear-resistant rubber layer. Since the fiber-reinforced composite sandwich core can be damaged in advance when the pressure approaches or exceeds the tolerance limit of the material to be processed, a thicker fiber-reinforced composite sandwich core is beneficial to leave more safety protection margin. According to practical experience, considering factors such as pressure transmission and cost, the thickness of the fiber-reinforced composite sandwich core should not be thickened unlimitedly, i.e. it is appropriate to be 0.3-0.5 mm.

[0049] Specifically, the flexible rubber layer is one or more of natural rubber, styrene-butadiene rubber, nitrile rubber, silicone rubber, thermoplastic polyurethane flexible body, styrene thermoplastic flexible body, and ethylene-propylene-diene rubber. The flexible rubber layer composed of the above materials can meet the requirements of strength ≥ 2.0 MPa, elongation ≥ 300%, and elasticity ≥ 60%, has good deformation performance and coating effect, and is beneficial to the full contact and pressure conduction between interfaces.

[0050] Specifically, the wear-resistant rubber layer is made of one or more of natural rubber, styrene-butadiene rubber, nitrile rubber, silicone rubber, thermoplastic polyurethane flexible body, styrene thermoplastic flexible body, and ethylene-propylene-diene rubber, and adds wear-resistant fillers; the wear-resistant fillers are one or more of carbon fibers, graphite, polytetrafluoroethylene particles, and molybdenum disulfide.

[0051] Preferably, the addition amount of the wear-resistant filler is 3%-10% by mass based on the total mass of the wear-resistant rubber layer. If the addition amount is too small, the wear-resistant effect cannot be good, and if the addition amount is too high, the adhesion and uniformity of the rubber body are affected, and the vulcanization molding of the rubber layer is affected.

[0052] The present application also discloses a preparation method of the flexible cushioning material, comprising the following steps:

[0053] S1: preparing a flexible rubber sheet;

[0054] S2: prepare fiber preforms with different volume densities, cut to appropriate size and stack according to volume density as gradient reinforcement; after dilution by solvent, inject resin into the gradient reinforcement, and after drying, obtain a fiber-reinforced composite sandwich core;

[0055] S3: prepare wear-resistant rubber sheet;

[0056] S4: sequentially place the cut flexible rubber sheet, fiber-reinforced composite sandwich core, and wear-resistant rubber sheet in the vulcanization mold, and after demolding, obtain a flexible cushioning material.

[0057] Specifically, the flexible rubber sheet can be purchased or prepared by oneself.

[0058] The present application provides a preparation method of a rubber sheet, and the preparation raw materials include a rubber base material, a softening agent, an anti-aging agent, a toughening agent, and a processing aid, and the method comprises the following steps:

[0059] After the preparation raw materials are mixed according to the proportions, they are placed in a mixer for mixing treatment, and after uniform mixing, a rubber lump is obtained.

[0060] The rubber lump obtained by mixing is calendered to obtain a flexible rubber sheet with a specific thickness and width.

[0061] For example, in the above preparation raw materials, the rubber base material accounts for 70-80%, the softening agent accounts for 5-10%, the anti-aging agent accounts for 0.5-2%, the toughening agent accounts for 10-20%, and the processing aid accounts for 1-3% by mass fraction, and the calendering temperature is 60-95°C.

[0062] Preferably, the rubber base material of the flexible rubber sheet is one or more of natural rubber, styrene-butadiene rubber, nitrile rubber, silicone rubber, cis-butadiene rubber, thermoplastic polyurethane flexible body, styrene thermoplastic flexible body, and ethylene-propylene-diene rubber.

[0063] The flexible rubber layer prepared from the above materials can meet the requirements of strength ≥ 2.0 MPa, elongation ≥ 300%, and elasticity ≥ 60%, has good deformation performance and coating effect, and is conducive to full contact and pressure conduction between interfaces.

[0064] Specifically, in step S2, the number of stacked layers of the fiber preform is not less than 3. Using more stacked layers can obtain a smoother density gradient, which is conducive to pressure conduction and the stability of the internal structure of the fiber-reinforced composite sandwich core. However, considering that the total thickness of the fiber-reinforced composite sandwich core should not exceed 0.5 mm, the number of stacked layers of the fiber preform should not be increased indefinitely.

[0065] For example, in the direction from the wear-resistant rubber layer to the flexible rubber layer, the volume density difference between adjacent fiber preforms (for example, a total of 3 layers) is 0.1-0.2 g / cm3 The uniform distribution of the volume density difference between adjacent fiber preforms within the density upper and lower limit range is beneficial to improve the structural stability of the flexible cushioning material, and also helps to obtain better pressure transmission effect.

[0066] Specifically, the fiber preform is prepared by a fiber net tire, needling, composite needling or sewing, etc., and is a three-dimensional multi-layer grid structure, and the volume density is 0.12-0.4 g / cm 3 The core density of the fiber-reinforced composite sandwich core prepared in the volume density range covers the density range of common thermal protection layer materials, thereby playing a more sufficient pressure transmission effect and protection effect.

[0067] The fiber preform has a porosity of greater than 65%, and the higher porosity meets the density requirement, is beneficial to resin impregnation during subsequent pre-solidification, and on the other hand, the porous network structure can effectively absorb external energy when subjected to external pressure impact, so that the fiber preform has a higher stress absorption and buffering effect.

[0068] Specifically, the step S2 is specifically operated as follows: the resin is diluted to a mass concentration of 10-50% by a solvent, and the injection pressure is controlled to be 0.01-0.15 Mpa to inject the gradient reinforcement. The solvent is one or a mixture of several of ethanol, isopropanol, water, ethylene glycol or glycerol. When the mass concentration is too high, the resin cannot be uniformly dispersed, which affects the molding effect, and when the concentration is too low, the sandwich core of a specific density cannot be prepared, which affects the final material buffering effect.

[0069] The application further discloses a tool for integrally forming the composite component, the composite component being a heat-proof load-bearing integrated composite component composed of an outer heat-proof layer and a load-bearing layer bonded and combined together; and the tool is composed of an upper mold, a cushion pad and a bottom mold, wherein the cushion pad is made of the flexible cushioning material.

[0070] Specifically, the bottom mold is provided with a positioning device composed of an edge pressing limiting block and a middle wedge-shaped limiting block. The lower surface of the edge pressing limiting block is provided with a screw structure matched with a screw hole in the corresponding position of the bottom mold, so as to realize the connection and fixation of the edge pressing limiting block and the bottom mold.

[0071] This tooling achieves precise positioning and assembly of the outer heat protection layer and the load-bearing layer through the cooperation of the edge pressure stop block and the middle wedge-shaped positioning block, thus achieving overall high-precision and high-quality bonding molding. What is particularly important is that based on the dual-function design of cavity thickness control and stress buffering, a flexible buffer layer (i.e., cushion) is introduced between the composite component and the tooling. On the one hand, it compensates for the surface and thickness tolerances of the outer heat protection layer and the load-bearing layer itself, controls the cavity thickness, and ensures that the bonding surface is in close contact and the force is evenly distributed; on the other hand, it provides a better stress buffering effect between the tooling upper mold and the outer heat protection layer, and has good wear resistance, avoiding the problem of damage to the outer heat protection layer due to excessive local stress, effectively protecting the product, and improving product quality and pass rate.

[0072] Specifically, the buffer pad is fixed to the lower surface of the upper mold in a bonding manner.

[0073] Specifically, the thickness of the cushion is 0.6 to 1.0 mm. The total thickness tolerance of the load-bearing layer and the outer heat shield (the material to be treated) generally does not exceed 0.6 mm. To ensure uniform pressure transmission and adequate fit between the device and material interfaces, the cushioning material's thickness should be no less than the total tolerance of the material to be treated, i.e., 0.6 mm. Furthermore, the cushioning material should not be too thick; based on practical experience, no more than 1 mm is appropriate.

[0074] Specifically, the upper and lower molds match in shape, either flat, with a specific arc or a variable curvature. The lower mold is provided with a cavity. The cavity's profile matches the carrier layer, and the inner sidewalls of the cavity mate with the side edges of the carrier layer to secure the carrier layer. In other words, the cavity's design is closely tied to the size and thickness of the material being processed. Once the cavity's dimensions are determined, the size and thickness of the material that the tooling can process are also fixed.

[0075] Specifically, the positioning device consists of edge pressure-stopping blocks and a central wedge-shaped positioning block. The edge pressure-stopping blocks secure the material to be processed, effectively preventing warping and deformation that could lead to inaccurate positioning. The positioning blocks simultaneously determine the material's perimeter, allowing for rough adjustment of the material's position as a pre-positioning reference. The central wedge-shaped positioning block, acting as a secondary positioning reference, allows for more precise adjustment of the relative positions of multiple layers (two or more) of material to be processed, ensuring they are fixed at the ideal bonding position.

[0076] Specifically, the bottom surface contour of the edge pressure stopper matches the bottom mold and can be designed as a flat surface, a specific arc, or a variable curvature. Threaded holes are provided at corresponding locations on the bottom mold, and the stopper is connected to the bottom mold via fastening screws. Optionally, the number of stoppers can be two or more, depending on the specific size and shape of the material being processed.

[0077] Specifically, the middle wedge-shaped positioning block is provided with a threaded hole communicated with the bottom die, and the threaded hole is used for fixing the wedge-shaped positioning block in the positioning groove of the bottom die, and the positioning block is aligned with the threaded hole of the bottom die when the wedge-shaped block is completely matched with the product.

[0078] Preferably, the thickness / height of the edge pressing limiting block and the middle wedge-shaped positioning block should not be too large, and the specific size is adjusted according to the thickness of the material to be processed, so as to avoid that the top of the positioning device is too high and interferes with the bottom surface of the upper die, resulting in uneven pressure.

[0079] The application also discloses an application of the above tooling, namely an integrated forming method of a heat-resistant load-bearing integrated composite component.

[0080] The specific steps include:

[0081] S21: preparing a load-bearing layer and an outer heat-resistant layer;

[0082] S22: roughening the bonding surfaces of the load-bearing layer and the outer heat-resistant layer;

[0083] S23: placing the load-bearing layer on the tooling bottom die and pre-positioning and fixing the load-bearing layer;

[0084] S24: coating the bonding surfaces of the load-bearing layer and the outer heat-resistant layer with an adhesive, placing the outer heat-resistant layer above the load-bearing layer, positioning and fixing the outer heat-resistant layer, and combining the upper die with the buffer pad on the upper surface;

[0085] S25: placing the tooling on a press, setting the parameters of the press, and pressurizing and curing;

[0086] S26: taking out the tooling, demolding, and obtaining the composite component.

[0087] Specifically, the load-bearing layer in step S21 is a high-temperature-resistant resin such as bismaleimide resin or polyimide, and a corresponding prepreg is prepared by a hot melting method or a wet method, and a composite load-bearing layer is prepared by using a molding process or a autoclave molding process.

[0088] Specifically, the outer heat-resistant layer is a composite material prepared by impregnating a fiber preform with a resin glue solution, and the outer heat-resistant layer is obtained by the following steps: combining the fiber preform in a forming mold, pressurizing and injecting a resin precursor glue solution, and after sufficient composite impregnation, curing and drying.

[0089] Specifically, the fiber preform of the outer heat protection layer is composed of one or more of inorganic glass fiber, quartz fiber, carbon fiber, phenolic fiber, glass fiber, mullite fiber or alumina fiber, and the above fibers are commonly used fibers for special materials in the field of aerospace thermal protection.

[0090] Specifically, the resin used in the outer heat protection layer is one or more of thermoplastic phenolic resin, thermosetting phenolic resin, silicone modified phenolic resin, boron phenolic resin, and polyarylacetylene resin. The above resins are commonly used resins for special materials in the field of aerospace thermal protection.

[0091] Specifically, step S22 may roughen the bonding surface by using processes such as surface grinding and sandblasting, thereby increasing the roughness of the bonding surface, making it more fully in contact with the adhesive and having a larger contact area, which is conducive to obtaining a better bonding effect.

[0092] Preferably, the bonding surface of the bearing layer is sandblasted with emery grit of 50 or less, and the bonding surface of the outer heat-resistant layer is polished with sandpaper of 50 or less. If the sandblasting or polishing grit is too high, the surface roughness will decrease, and the surface roughening effect will not be achieved. If the grit is too low, the surface quality will be even rougher and uneven, which will damage the performance of the material itself.

[0093] Specifically, step S23 involves placing the load-bearing layer on the tooling base mold, aligning the inner surface with the base mold surface, and securing it with edge stoppers. The outer heat shield layer is then trial-assembled, using the edge stoppers as a pre-positioning reference to determine the circumferential edge position, and then aligned, positioned, and adjusted. This step only pre-positions and secures the load-bearing layer; trial-assembling the outer heat shield layer serves only to verify the ideal pre-positioning of the load-bearing layer.

[0094] Specifically, step S24 involves placing the outer heat shield layer above the load-bearing layer, using wedge-shaped positioning blocks to align the load-bearing and outer heat shield layers, and securing the outer heat shield layer in place. In practice, the wedge-shaped positioning blocks perforate the centers of the load-bearing and outer heat shield layers. The final product is typically cut and discarded.

[0095] Specifically, the adhesive in step S24 is silicone rubber, silicon oxynitride glue, or other adhesives with good heat resistance and bonding properties. This type of adhesive has a temperature resistance rating of above 300°C, meeting the operating temperature requirements, and a coating thickness of 0.5 to 1 mm. If the adhesive layer is too thin, it may not be able to penetrate both sides of the bonded object, or even only have adhesive on one side, which will have a negative impact on the internal bonding quality. If the adhesive layer is too thick, the probability of defects inside the adhesive layer increases, and when subjected to external force, it is easy to cause stress concentration around these defects, resulting in subsequent product damage to the adhesive layer in a high heat flow service environment.

[0096] Specifically, the press parameters are 1.5 MPa to 3 MPa. If the bonding pressure is too high, the outer heat-proof material is easily damaged, resulting in irreversible structural damage such as delamination and fracture. If the bonding pressure is too low, the adhesive cannot flow effectively inside the material, affecting the wetting effect of the bonding surface and adversely affecting the bonding effect.

[0097] Specifically, the curing temperature is room temperature to 60°C. If the temperature is too high, the outer heat-proof layer is easily chemically reacted after being affected by the temperature, destroying the bulk structure and affecting the subsequent service performance.

[0098] Specifically, the specific operation of step S25 is as follows: after curing at room temperature for 72 hours, the upper mold is opened, the fastening screws of the edge pressure stop limit block and the middle wedge-shaped positioning block are loosened respectively, the positioning block is taken out, the residual adhesive is cleaned and partially trimmed, and the product after bonding and forming is obtained.

[0099] Examples and comparative examples:

[0100] Example 1

[0101] Step one: preparation of flexible rubber layer

[0102] The mass fractions of 78% nitrile rubber, 8% softening agent, 1% anti-aging agent, 10% toughening agent, and 3% processing aid are mixed according to the proportion, then put into the mixer for mixing treatment, and uniformly mixed to obtain a rubber mass. The rubber mass obtained by mixing is calendered to form a flexible rubber sheet with a fixed thickness and width.

[0103] Step two: preparation of fiber-reinforced composite sandwich core

[0104] The low-density fiber preform is prepared by a phenolic fiber web composite needling process. The volume density of the first density unit is 0.14 g / cm 3 , the volume density of the second density unit is 0.25 g / cm 3 , and the volume density of the third density unit is 0.30 g / cm 3 . The gradient fiber preform is used as a reinforcing body, the resin is diluted by ethanol solvent to control the mass concentration to 25%, and then injected into the reinforcing body for sol-gel reaction, the injection pressure is controlled to 0.10 MPa, and the fiber-reinforced composite sandwich core is obtained after drying at normal pressure. The density of the fiber-reinforced composite sandwich core is in the range of 0.50 to 0.80 g / cm 3 .

[0105] Step three: preparation of wear-resistant rubber layer

[0106] The mass parts of 75% nitrile rubber, 8% softener, 1% antioxidant, 10% toughening agent, 2% processing aid, 4% polytetrafluoroethylene particle wear-resistant filler are mixed according to the proportion, and then put into a mixer for mixing treatment, and the rubber rubber mass is obtained after uniform mixing. The rubber rubber mass obtained by mixing is calendered, and the calendering temperature is 70 DEG C, and the flexible rubber sheet with fixed thickness and width is obtained.

[0107] Step four: preparation of flexible buffer layer

[0108] First, the vulcanization mold is preheated to 150-180 DEG C, a layer of flexible rubber sheet is laid on the mold first, and then the fiber reinforced composite sandwich core is laid on it. The volume density of the fiber reinforced composite sandwich core is 0.14 g / cm 3 The third density unit is connected with the flexible rubber sheet, and the surface wear-resistant rubber sheet is laid on the last, and the mold is covered, and the vulcanization stage is entered, the vulcanization temperature is 180 DEG C, and the vulcanization temperature is 4 h, and the flexible buffer layer with a thickness of 1 mm is obtained after demolding.

[0109] The above flexible buffer material is used for bonding the outer heat protection layer and the bearing layer.

[0110] Prepare the tooling, including the upper mold, the buffer pad and the bottom mold;

[0111] The tooling is used for bonding the outer heat protection layer and the bearing layer, and the composite component is prepared, and the steps are as follows:

[0112] First step: preparation of bearing layer and outer heat protection layer:

[0113] The bearing layer is made of carbon fiber reinforced polyimide resin, and the bearing layer is prepared by molding process;

[0114] The outer heat protection layer is a composite material prepared by impregnating phenolic resin glue solution into uniform phenolic fiber preform, and the density is 0.60 g / cm 3 .

[0115] Second step: roughening treatment:

[0116] The outer surface of the bearing layer is sandblasted with 50 mesh diamond sand, and the inner surface of the outer heat protection layer is polished with 50 mesh sandpaper, and then cleaned and reserved.

[0117] Third step: placing the bearing layer on the tooling bottom mold and pre-positioning and fixing:

[0118] The bearing layer is placed in the concave cavity of the tooling bottom mold, and the inner surface is attached to the bottom mold surface, and the edge stop limiting block is used for fixing, and then the outer heat protection layer is assembled, and the edge stop limiting block is used as the pre-positioning reference to determine the circumferential edge position, and the alignment, positioning and adjustment are carried out.

[0119] Fourth step: bonding and forming:

[0120] The outer heat protection layer is placed on the carrier layer, positioned by the second positioning reference, and fixed in position after assembly. The upper mold of the tooling is closed and mounted on the press.

[0121] Fifth step: pressure curing, bonding pressure 2 MPa, completing the bonding molding of the heat protection carrier integrated composite component.

[0122] Sixth step: demolding:

[0123] After 72 hours of room temperature curing, the upper mold is opened, the fastening screws of the edge pressure stop limit block and the middle wedge-shaped positioning block are loosened, the positioning blocks are removed, the remaining adhesive is cleaned and partially trimmed, and the bonded molded product is obtained.

[0124] Implementation effect

[0125] The prepared flexible cushioning material has a strength of 3.0 MPa, an elongation of 350%, and an elasticity of 75%.

[0126] The product is detected by CT, the bonding quality of the carrier layer and the outer heat protection layer is good, there is no debonding area, the effective bonding area ratio is 100%, the structure of the outer heat protection layer and the carrier layer is intact, and there is no internal damage.

[0127] Example 2

[0128] Step one: preparation of flexible rubber layer

[0129] The mass fraction of 80% butadiene rubber, 6% softener, 2% antioxidant, 10% toughening agent, and 2% processing aid are mixed in proportion, then put into a mixer for mixing treatment, and uniformly mixed to obtain a rubber mass. The rubber mass obtained by mixing is calendered to form a flexible rubber sheet with a fixed thickness and width.

[0130] Step two: preparation of fiber-reinforced composite sandwich core

[0131] The low-density fiber preform is prepared by a glass fiber mesh tire composite needling process. The first density unit has a bulk density of 0.10 g / cm 3 , the second density unit has a bulk density of 0.22 g / cm 3 , and the third density unit has a bulk density of 0.30 g / cm 3The gradient fiber preform is used as the reinforcing body, the resin is diluted by ethanol solvent, the mass concentration is controlled to be 25%, the resin is injected into the reinforcing body to perform sol-gel reaction, the injection pressure is controlled to be 0.10 MPa, and the fiber-reinforced composite sandwich core body is obtained after normal pressure drying, the density of the fiber-reinforced composite sandwich core body ranges from 0.40 to 0.80 g / cm 3 .

[0132] Step three: preparation of the wear-resistant rubber layer

[0133] The mass fractions of 78% butadiene rubber, 6% softener, 2% anti-aging agent, 8% toughening agent, 2% processing aid and 4% polytetrafluoroethylene particle wear-resistant filler are mixed according to the proportions, and then the mixture is put into a mixer for mixing treatment, and the rubber mass is obtained after uniform mixing. The rubber mass obtained by mixing is calendered to form a flexible rubber sheet with a fixed thickness and width.

[0134] Step four: preparation of the flexible buffer layer

[0135] First, the vulcanization mold is preheated to 150-160 DEG C, a layer of flexible rubber sheet is laid on the mold, then the fiber-reinforced composite sandwich core body is laid on the flexible rubber sheet, the volume density of the fiber-reinforced composite sandwich core body is 0.10 g / cm 3 The third density unit is connected to the flexible rubber sheet, and finally the surface wear-resistant rubber sheet is laid on the mold, and the mold is covered, and the vulcanization stage is entered, the vulcanization temperature is 160 DEG C, and the vulcanization temperature is 4 h, and the flexible buffer layer with a thickness of 1 mm is obtained after demolding.

[0136] The above flexible buffer material is used for bonding the outer heat protection layer and the bearing layer.

[0137] Prepare the tooling, including the upper mold, the buffer pad and the bottom mold;

[0138] The tooling is used for bonding the outer heat protection layer and the bearing layer, and the composite component is prepared, and the steps are as follows:

[0139] First step: preparation of the bearing layer and the outer heat protection layer

[0140] The bearing layer is prepared by using carbon fiber reinforced bismaleimide resin through a molding process;

[0141] The outer heat protection layer is a composite material prepared by impregnating a glass fiber preform with a phenolic resin glue solution, and the density is 0.70 g / cm 3 .

[0142] Second step: roughening treatment

[0143] The outer surface of the bearing layer is sandblasted with 50-mesh diamond sand, and the inner profile of the outer heat protection layer is polished with 50-mesh sandpaper, and then cleaned and reserved.

[0144] Third step: placing the bearing layer on the tooling bottom die and pre-positioning and fixing:

[0145] Place the bearing layer in the tooling bottom die cavity, make the inner surface adhere to the bottom die surface, and fix it with the edge pressing stop limit block. Then assemble the outer thermal insulation layer, determine the circumferential edge position using the edge pressing stop limit block as the pre-positioning reference, and perform alignment, positioning, and adjustment.

[0146] Fourth step: bonding and forming:

[0147] Uniformly apply a total thickness of 0.5mm of KH-RTV-400 silicone rubber adhesive on the bonding surface of the bearing layer and the outer thermal insulation layer, place the outer thermal insulation layer above the bearing layer, position it using the second positioning reference, fix the position of the outer thermal insulation layer after assembly, close the tooling upper die, and mount it on the press.

[0148] Fifth step: pressure curing, bonding pressure 2MPa, complete the bonding and forming of the thermal insulation bearing integrated composite component.

[0149] Sixth step: demolding:

[0150] After curing at room temperature for 72h, open the upper die, loosen the fastening screws of the edge pressing stop limit block and the middle wedge-shaped positioning block, remove the positioning blocks, clean the remaining adhesive, and perform local finishing to obtain the bonded and formed product.

[0151] Implementation effect

[0152] The prepared flexible cushioning material has a strength of 3.5MPa, an elongation of 340%, and an elasticity of 82%.

[0153] Using CT to detect the product, the bonding quality of the bearing layer and the outer thermal insulation layer is good, there is no debonding area, the effective bonding area ratio is 100%, the outer thermal insulation layer and the bearing layer structure are intact, and there is no internal damage.

[0154] Example 3

[0155] Step one: preparation of flexible rubber layer

[0156] Mix 78% silicone rubber, 8% softening agent, 1% anti-aging agent, 10% toughening agent, and 3% processing aid in the proportions, then put them into a mixer for mixing and processing. After uniform mixing, a rubber mass is obtained. The rubber mass obtained by mixing is pressed into a flexible rubber sheet with a fixed thickness and width at a pressing temperature of 85℃.

[0157] Step two: preparation of fiber-reinforced composite sandwich core

[0158] The low-density fiber preform adopts a phenolic fiber web composite needling process, the first density unit volume density is 0.12 g / cm 3 , the second density unit volume density is 0.26 g / cm 3 , and the third density unit volume density is 0.36 g / cm 3 . The gradient fiber preform is used as a reinforcing body, a resin is diluted by ethanol solvent, the mass concentration is controlled to be 25%, the resin is injected into the reinforcing body to perform a sol-gel reaction, the injection pressure is controlled to be 0.10 MPa, and after normal pressure drying, a fiber-reinforced composite sandwich core body is obtained, and the fiber-reinforced composite sandwich core body density range is 0.44-0.85 g / cm 3 .

[0159] Step three: preparation of the wear-resistant rubber layer

[0160] 75% of the mass fraction of silicone rubber, 8% of the mass fraction of softening agent, 1% of the mass fraction of anti-aging agent, 10% of the mass fraction of toughening agent, 2% of the mass fraction of processing aid, and 4% of the mass fraction of molybdenum disulfide wear-resistant filler are fully mixed according to the proportion, and then are put into a mixer for mixing treatment. After uniform mixing, a rubber rubber mass is obtained. The rubber mass obtained by mixing is calendered to form a flexible rubber sheet with a fixed thickness and width.

[0161] Step four: preparation of the flexible buffer layer

[0162] First, the vulcanization mold is preheated to 150-180 DEG C. A flexible rubber sheet is first laid on the mold, then the fiber-reinforced composite sandwich core body is laid on the flexible rubber sheet, the volume density of the fiber-reinforced composite sandwich core body is 0.12 g / cm 3 of the third density unit is connected with the flexible rubber sheet, and finally the surface wear-resistant rubber sheet is laid on the mold. After the mold is covered, the vulcanization stage is entered, the vulcanization temperature is 180 DEG C, the vulcanization is kept for 4 h, and after demolding, a 1 mm thick flexible buffer layer is obtained.

[0163] The above flexible buffer material is used for bonding the outer heat protection layer and the bearing layer.

[0164] Prepare the tooling, including the upper mold, the buffer pad and the bottom mold;

[0165] The tooling is used for bonding the outer heat protection layer and the bearing layer to prepare a composite component, and the steps are as follows:

[0166] First step: preparation of the bearing layer and the outer heat protection layer

[0167] The bearing layer adopts carbon fiber reinforced polyimide resin, and the bearing layer is prepared by a molding process;

[0168] The outer heat protection layer is a composite material prepared by impregnating uniform phenolic fiber preform with phenolic resin glue, and the density is 0.68 g / cm 3 .

[0169] Second step: roughening treatment:

[0170] The outer surface of the bearing layer is sandblasted with 50-mesh diamond abrasive, and the outer heat protection layer is polished with 50-mesh sandpaper. After cleaning, the bearing layer is ready for use.

[0171] Third step: placing the bearing layer on the tooling bottom mold and pre-positioning and fixing:

[0172] The bearing layer is placed in the concave cavity of the tooling bottom mold, with the inner surface adhering to the bottom mold surface. The edge stop limit block is used for fixing, and then the outer heat protection layer is assembled. The edge stop limit block is used as a pre-positioning reference to determine the circumferential edge position, and alignment, positioning, and adjustment are performed.

[0173] Fourth step: adhesive forming:

[0174] The bearing layer and the outer heat protection layer are evenly coated with a total thickness of 0.5mm of KH-CP silicone rubber adhesive. The outer heat protection layer is placed above the bearing layer, and the second positioning reference is used for positioning. After assembly, the outer heat protection layer position is fixed, the tooling upper mold is closed, and the press is assembled.

[0175] Fifth step: pressure curing, adhesive pressure 2MPa, complete the adhesive forming of the heat protection bearing integrated composite component.

[0176] Sixth step: demolding:

[0177] After curing at room temperature for 72h, the upper mold is opened, the fastening screws of the edge stop limit block and the middle wedge-shaped positioning block are loosened, the positioning blocks are removed, the remaining adhesive is cleaned, and local trimming is performed to obtain the adhesive formed product.

[0178] Implementation effect

[0179] The prepared flexible cushioning material has a strength of 3.2MPa, an elongation of 340%, and an elasticity of 80%.

[0180] The product is detected by CT, the bearing layer and the outer heat protection layer have good adhesive quality, there is no debonding area, the effective adhesive area ratio is 100%, the outer heat protection layer and the bearing layer structure are intact, and there is no internal damage.

[0181] Comparative Example 1

[0182] A commercially available low-elasticity polyurethane rubber layer is used as the flexible cushioning material, with a strength of 1.2MPa, an elongation of 100%, and an elasticity of 40%.

[0183] The preparation process of the flexible cushioning material is omitted, and a commercially available low-elasticity polyurethane rubber layer is used to replace the flexible cushioning material disclosed in the present application to make a tooling cushion pad. Other operations and parameter settings are exactly the same as in Example 1.

[0184] Effects of implementation

[0185] Adopting CT to detect the product, the bonding quality of the bearing layer and the outer heatproof layer is poor, large-area debonding area appears, and the proportion of effective bonding area is only 80%.

[0186] Comparative example 2

[0187] Adopting a commercially available high-elasticity rubber layer as the flexible cushioning material, the strength is 2.2 MPa, the elongation is 240%, and the elasticity is 60%.

[0188] The preparation process of the flexible cushioning material is omitted, and a commercially available high-elasticity rubber layer is used to replace the flexible cushioning material disclosed in the application to manufacture the tool cushion pad. Other operations and parameter settings are completely the same as those in example 1.

[0189] Effects of implementation

[0190] Adopting CT to detect the product, the bonding quality of the bearing layer and the outer heatproof layer is good, the proportion of effective bonding area is 94%, but the outer heatproof layer appears local delamination fracture, and the internal structure is damaged.

[0191] The above description is only the preferred specific implementation of the application, but the protection scope of the application is not limited to this. Any changes or replacements that can be easily thought of by those skilled in the art within the technical range disclosed in the application should be covered in the protection scope of the application.

Claims

1. A tooling for integrally forming a composite component, characterized by: The tooling is composed of an upper mold, a buffer pad, and a bottom mold, wherein the buffer pad is made of a flexible buffer material. The flexible buffer material has a three-layer structure of a flexible rubber layer (1), a fiber-reinforced composite sandwich core, and a wear-resistant rubber layer (5) stacked in order. The fiber-reinforced composite sandwich core has a density gradient that increases or decreases in the thickness direction.

2. The tooling for integrally forming a composite structure of claim 1, wherein: The fiber-reinforced composite sandwich core is made of a fiber preform and a resin.

3. A tooling for integrally forming a composite structure according to claim 2, wherein: The fiber preform is composed of one or more of quartz fiber, carbon fiber, phenolic fiber, glass fiber, mullite fiber, or alumina fiber.

4. The tooling for integrally forming a composite structure of claim 2, wherein: The resin is one or more of thermoplastic phenolic resin, thermosetting phenolic resin, silicone-modified phenolic resin, boron phenolic resin, and polyarylacetylene resin.

5. The tooling for integrally forming a composite structure of claim 1, wherein: The fiber-reinforced composite sandwich core has the lowest density at the interface with the flexible rubber layer (1) and the highest density at the interface with the wear-resistant rubber layer (5).

6. The tooling for integrally forming a composite structure of claim 1, wherein: The total thickness of the flexible buffer material is 0.6-1.0 mm, wherein the thickness of the flexible rubber layer (1) and the wear-resistant rubber layer (5) is 0.15-0.25 mm, and the thickness of the fiber-reinforced composite sandwich core is 0.3-0.5 mm.

7. A tooling for integrally forming a composite structure according to any one of claims 1 to 6, wherein The flexible buffer material is prepared by the following method, comprising the following steps: S1: Prepare a flexible rubber sheet; S2: Prepare fiber preforms with different bulk densities, cut them to the appropriate size, and stack them in order as gradient reinforcements according to the bulk density; dilute the resin with a solvent, inject it into the gradient reinforcements, and dry to obtain a fiber-reinforced composite sandwich core; S3: Prepare a wear-resistant rubber sheet; S4: Place the cut flexible rubber sheet, fiber-reinforced composite sandwich core, and wear-resistant rubber sheet in a vulcanization mold in order, and after demolding, obtain the flexible buffer material.

8. A tooling for integrally forming a composite structure according to claim 7, wherein: The step S2 includes diluting the resin to a mass concentration of 10-50% with a solvent, and injecting the diluted resin into the gradient reinforcements at a controlled injection pressure of 0.01-0.15 MPa.

9. Use of a tool according to any one of claims 1-8, characterized in that: The tooling is used to realize the one-piece molding of the composite component through the steps of material surface treatment, adhesive coating, pressure curing, and demolding.

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