Carbon ceramic brake disc blank with layered composite structure and its moulding method

Abstract

The present application relates to a kind of carbon ceramic brake disc blank body with layered composite structure molding method, comprising the following steps: preparation high-density carbon fiber reinforced layer preform;Preparation short fiber / particle reinforced porous functional layer mixture;High-density carbon fiber reinforced layer preform and porous functional layer mixture are placed into mould according to the layered composite structure of upper high-density carbon fiber reinforced layer preform, middle porous functional layer mixture and lower high-density carbon fiber reinforced layer preform;Molding, obtain carbon ceramic brake disc blank body with functional gradient structure.The intermediate layer porosity gradient design of the present application is from center zone 38% to transition zone 32% to bonding zone 25%, thereby optimizing molten silicon infiltration path, and intermediate layer adopts zoned weighing, to form the matrix that there is difference in radial and circumferential powder density, to further form the rheological supplement located in the radial of blank and the sandwich air duct structure of circumferential side.

Description

Technical Field

[0001] This invention relates to the field of high-performance brake material manufacturing technology, and in particular to a carbon ceramic brake disc blank with a layered composite structure and its molding method, which is applicable to high-end braking systems such as aviation, rail transportation and supercars. Background Technology

[0002] Carbon-ceramic (C / C-SiC) composite brake discs, with their high specific strength, excellent high-temperature stability, good friction performance, and wear resistance, have become an ideal choice for braking systems in aircraft, high-speed rail transportation, and high-end sports cars. Currently, the core technologies in this field revolve around two major process routes: Chemical Vapor Infiltration (CVI) and Reactive Melt Infiltration (RMI).

[0003] Chemical vapor infiltration (CVI) can produce C / C-SiC composites with uniform structure and excellent performance. However, the main bottleneck of this process is its extremely long production cycle, which usually takes hundreds of hours to complete the densification process. This leads to a significant increase in manufacturing costs, making it difficult to meet the needs of large-scale industrial production and lacking economic competitiveness.

[0004] While reactive melt infiltration significantly shortens the production cycle and reduces costs, it still has inherent limitations in its technical implementation. On one hand, during this process, the infiltration reaction of molten silicon into the porous carbon framework often struggles to achieve uniform control of the microstructure, easily leading to the formation of free silicon-rich regions within the material. These silicon-rich regions act as "weak points" within the material, not only weakening the overall high-temperature mechanical properties of the composite material but also potentially becoming a source of thermal crack initiation and propagation. This is particularly problematic under repeated high- and low-temperature thermal shock environments, severely reducing the reliability and lifespan of brake discs.

[0005] On the other hand, traditional carbon-ceramic brake disc designs often employ a single homogeneous material structure or a simple two-dimensional laminated design. Homogeneous structures cannot effectively coordinate the significant temperature gradient and thermal stress distribution between the friction surface and internal regions during intense braking, making the friction surface area highly susceptible to thermal fatigue cracks and leading to a decline in braking performance. Simple two-dimensional laminated structures, on the other hand, rely excessively on the resin or pyrolytic carbon matrix between the layers as the load-bearing medium. Their inherent interlayer strength deficiency is difficult to eliminate, making them prone to delamination failure under complex stress conditions (especially braking pressure), becoming a key bottleneck restricting the overall load-bearing capacity of the brake disc.

[0006] Chinese patent CN115823151A discloses a sandwich-structured carbon / ceramic brake disc, belonging to the technical field of vehicle braking components. This brake disc is a sandwich structure composed of a friction functional layer, a mechanical functional layer, and another friction functional layer in sequence, with the friction and mechanical functional layers connected by mortise and tenon joints. Specifically, it is prepared by molding a sandwich structure matrix of carbon cloth composite layer, short fiber layer, and carbon cloth composite layer, followed by high-temperature pyrolysis and silicon infiltration reaction. This patented brake disc possesses excellent overall mechanical properties, friction and wear resistance, and long service life. Moreover, it is prepared through solid-state molding, pyrolysis, and infiltration, resulting in a simple manufacturing process, short production cycle, and low production cost, demonstrating promising application prospects.

[0007] However, the patent's shortcomings lie in its core concept of "homogeneous core layer + interlayer mechanical connection + surface dimension gradient." While this solves some of the problems of interlayer debonding and surface edge chipping in traditional short-fiber brake discs, it still has significant limitations in structural design, process adaptability, and performance balance. Its short-fiber mechanical functional layer is a monolithic structure, achieving interlayer mortise and tenon joints only through the thickness gradient reduction of the carbon cloth composite layer and regularly arranged connecting holes. Essentially, it's a "structural reinforcement-oriented" interlayer bonding design, without addressing density control or functional structure construction within the intermediate layer. This patent only serves "interlayer anti-debonding," and the simple process cannot achieve heat dissipation, limiting it to a solid disc. Furthermore, the patent's short-fiber layer uses monolithic filling without zonal optimization for molding rheological characteristics, failing to compensate for edge rheological losses, resulting in significant radial and circumferential density deviations in the finished product. This patent achieves a porous matrix with 15-40% porosity through high-temperature pore opening (1800-2500℃), but the porosity is uniform across the entire matrix without a gradient distribution. This fails to provide ordered channels for molten silicon penetration and cannot provide graded buffering of thermal stress, leading to uneven molten silicon distribution or matrix cracking. In summary, the core design concept of this patent is limited to "solving interlayer debonding and surface edge chipping," focusing solely on the single objective of "mechanical strengthening" without considering the synergistic relationship between "rheological loss, thermal stress, and heat dissipation requirements" during the braking process. Its structural design (regular connecting holes, stepped dimensions), process design (homogeneous filling, integral molding), and performance requirements (uniform density, efficient heat dissipation, and composite stress adaptation) are disconnected, failing to achieve integrated optimization of "structure-process-performance," resulting in insufficient overall product competitiveness.

[0008] Furthermore, existing compression molding processes suffer from finished product quality defects caused by material rheology. During compression molding, due to the rheological effect of the material, the material in the edge area of ​​the brake disc tends to flow outwards, resulting in a lower edge density than the central area. This makes the edge of the finished product significantly weaker in strength and wear resistance than the central area, creating a weak point for brake disc failure. This problem has not yet been effectively solved in existing technologies.

[0009] In summary, existing carbon-ceramic brake discs have shortcomings in terms of manufacturing process efficiency, microstructure control, structural design rationality, and molding quality stability. They are difficult to simultaneously meet the demands of large-scale industrial production and the stringent requirements of high-end braking systems for high-temperature stability, thermal shock resistance, interlaminar failure resistance, and friction and wear performance of brake discs. Therefore, there is an urgent need for a carbon-ceramic brake disc manufacturing technology and corresponding product structure that balances efficient manufacturing with excellent service performance.

[0010] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention provides a molding method for a carbon-ceramic brake disc blank with a layered composite structure, comprising the following steps:

[0012] Preparation of high-density carbon fiber reinforced layer preforms;

[0013] Preparation of short fiber / particle-reinforced porous functional layer mixtures;

[0014] The high-density carbon fiber reinforced layer preform and the porous functional layer mixture are laid into the mold in a layered composite structure consisting of the upper high-density carbon fiber reinforced layer preform, the middle porous functional layer mixture and the lower high-density carbon fiber reinforced layer preform.

[0015] Compression molding yields a carbon-ceramic brake disc preform with a functionally graded structure; wherein...

[0016] During the process of laying the porous functional layer mixture into the mold, the intermediate porous functional layer mixture is weighed in sections to form a matrix with differences in powder density in the radial and circumferential directions;

[0017] When molding a carbon-ceramic brake disc preform with a functional gradient structure, the regions with different powder densities will form a rheological supplement located in the radial direction of the preform and a sandwich air duct structure on the circumferential side.

[0018] According to a preferred embodiment, the porous functional layer mixture comprises several powder density difference regions arranged regularly or irregularly. The distance between two adjacent powder density difference regions is 10-30 mm. The powder density difference regions extend radially and circumferentially with different shapes to extend to the edge of the porous functional layer.

[0019] According to a preferred embodiment, the high-density carbon fiber reinforcement layer preform is a PAN-based carbon fiber fabric pre-impregnated with phenolic resin, with a resin content of 20wt%-50wt% and a single-layer thickness of 0.25±0.05mm.

[0020] According to a preferred embodiment, the step of preparing the short fiber / particle-reinforced porous functional layer mixture further includes:

[0021] It is made by mixing short-cut carbon fibers, thermosetting phenolic resin powder, nano carbon powder, silicon carbide particles, pore-forming agent and dispersant in parts by weight.

[0022] According to a preferred embodiment, the porous functional layer mixture satisfies at least one of the following characteristics:

[0023] The length of chopped carbon fiber ranges from 5mm to 20mm;

[0024] The particle size of thermosetting phenolic resin powder is 500-1000 mesh;

[0025] Nano-carbon powder is nano-sized vapor-grown carbon powder with a particle size of 500-1000 mesh;

[0026] The silicon carbide particles are 500-1000 mesh, and the mass ratio of nano-carbon powder to silicon carbide particles is 1:(2-3).

[0027] The pore-forming agent is PMMA microspheres, 500-1000 mesh.

[0028] According to a preferred embodiment, before laying the high-density carbon fiber reinforced preform and the porous functional layer mixture into a mold, the method further includes:

[0029] Preheat the mold to 80°C and spray with release agent.

[0030] According to a preferred embodiment, in the process of molding a high-density carbon fiber reinforced layer preform and a porous functional layer mixture into a mold to obtain a carbon ceramic brake disc blank with a functional gradient structure, the molding process adopts a stepped pressure increase process, applying an initial pressure of 15±2MPa in the range of 100-120℃ and a final pressure of 30±3MPa in the range of 150-160℃.

[0031] According to a preferred embodiment, the molding process includes the following stages:

[0032] Pre-pressure exhaust stage: temperature 90-100℃, pressure 2-5MPa, time 5min;

[0033] Curing Stage I: Temperature 120℃, Pressure 15MPa, Time 10min;

[0034] Curing Stage II: Temperature 160℃, Pressure 30MPa, Time 30min, with a heating rate ≤5℃ / min, and pressure fluctuation ≤±0.5MPa during the holding stage.

[0035] The present invention also relates to a carbon-ceramic brake disc blank, which is manufactured by the compression molding method of the carbon-ceramic brake disc blank having a layered composite structure as described above.

[0036] According to a preferred embodiment, the thermal conductivity of the carbon-ceramic brake disc blank is 30-50 W / m·K in both the transverse and longitudinal directions, the coefficient of friction at 350°C is 0.5±0.05, and the specific wear rate is 7.2×10-7 mm3 / N·m.

[0037] 1. This invention employs a sandwich-style structure consisting of an upper high-density carbon fiber reinforcement layer, a middle porous functional layer, and a lower high-density carbon fiber reinforcement layer. This overcomes the design limitations of traditional homogeneous structures or simple two-dimensional stacked layers, achieving multiple technological advantages. Surface Enhancement for Failure Resistance: The upper and lower layers of PAN-based carbon fiber fabric pre-impregnated with phenolic resin (such as T700SC-12K) provide high flexural strength (flexural strength ≥100MPa), effectively resisting braking pressure during braking and completely solving the problem of insufficient strength in traditional short-fiber carbon ceramic brake discs. Precise Control of Thermal Stress: By matching the performance gradient between the high-density surface layer and the porous middle layer, the temperature gradient between the friction surface and the internal region is coordinated, reducing the thermal stress generated during braking by more than 40%. This significantly reduces the initiation and propagation of thermal fatigue cracks, improving the high-temperature stability and thermal shock resistance of the brake disc. Optimized Functional Division of Labor: The surface layer undertakes the core functions of wear resistance and load bearing, while the middle layer is responsible for buffering thermal stress and guiding molten silicon penetration, forming a synergistic system of "load bearing-buffering-penetration," comprehensively improving the service reliability of the brake disc.

[0038] 2. This invention innovatively employs a mid-layer partitioned weighing strategy to increase the powder density in the edge region, specifically addressing key defects of traditional molding processes. It compensates for rheological losses: effectively offsetting the density decay caused by the outward flow of edge material during molding, ensuring that the density of the brake disc edge is consistent with the central region, preventing the edge from becoming a weak point in strength and wear resistance. It improves dimensional accuracy and yield: improved density uniformity ensures the overall structural stability of the brake disc. Combined with mold preheating (80℃) and mold release agent spraying, it significantly reduces dimensional deviations after molding. Combined with subsequent machining tolerance control (±0.05mm), it significantly improves the finished product qualification rate. It enhances edge serviceability: after optimizing edge density, its wear resistance and strength are on par with the central region, preventing preferential wear or failure at the edges during braking and extending the overall service life of the brake disc.

[0039] 3. The intermediate layer adopts a porosity gradient design of "38% in the central area, 32% in the transition area, and 25% in the bonding area," combined with a specific component ratio, achieving multiple technological breakthroughs. Guiding uniform penetration of molten silicon: The gradient porosity structure provides orderly penetration channels for molten silicon, avoiding the problem of free silicon enrichment caused by uneven molten silicon distribution in traditional processes. Simultaneously, the "micro-nano composite reinforcement" effect of nano-carbon powder and silicon carbide particles enhances the high-temperature mechanical properties of the material. Enhanced thermal stress buffering: The gradient porosity can absorb and release thermal expansion stress during braking in stages, further enhancing thermal shock resistance. Combined with a consistent thermal conductivity of 30-50 W / m·K in both the transverse and longitudinal directions, efficient heat dissipation is achieved, preventing localized overheating. Optimized friction and wear performance: The synergistic effect of the porosity gradient with short-cut carbon fibers and silicon carbide particles stabilizes the friction coefficient of the brake disc at 0.5±0.05 at 350℃, with a specific wear rate as low as 7.2×10⁻⁻⁻⁶. 7 mm³ / N・m, far superior to traditional homogeneous materials (specific wear rate 1.5×10⁻ 6 (mm³ / N・m), ensuring the stability and durability of braking performance. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0041] Figure 1 This is a simplified logic flow diagram of a molding method for a carbon ceramic brake disc blank with a layered composite structure according to a preferred embodiment of the present invention.

[0042] Figure 2 This is a simplified logic flow diagram of a molding method for a carbon-ceramic brake disc blank with a layered composite structure in an optional embodiment of a preferred embodiment of the present invention. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments, and therefore should not be construed as limiting this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or server that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0045] Example 1

[0046] This invention provides a compression molding method for a carbon-ceramic brake disc preform with a layered composite structure, which is used for brake disc manufacturing, especially to meet the needs of large-scale industrial production, and significantly improves the overall service performance of brake discs. This invention focuses on high-temperature stability, thermal shock resistance, resistance to interlaminar failure, and tribological properties, and proposes a new material structure and its preparation method.

[0047] Carbon-ceramic (C / C-SiC) composite brake discs, with their high specific strength, excellent high-temperature stability, good friction performance, and wear resistance, have become an ideal choice for braking systems in aircraft, high-speed rail transportation, and high-end sports cars. Currently, the core technologies in this field mainly revolve around two major process routes: Chemical Vapor Infiltration (CVI) and Reactive Melt Infiltration (RMI).

[0048] Chemical vapor infiltration (CVI) can produce C / C-SiC composites with uniform structure and excellent performance. However, the main bottleneck of this process is its exceptionally long production cycle, typically requiring hundreds of hours to complete the densification process. This significantly increases manufacturing costs, making it difficult to meet the needs of large-scale industrial production and resulting in a lack of economic competitiveness. Therefore, this invention focuses on improving the reactive melt infiltration process.

[0049] While reactive melt infiltration significantly shortens the production cycle and reduces costs, it still has inherent limitations in its technical implementation, specifically:

[0050] In this process, the infiltration reaction of molten silicon into the porous carbon skeleton often fails to achieve uniform control of the microstructure, easily leading to the formation of free silicon-rich areas in localized regions within the material. The existence of these silicon-rich areas acts as a "weak point" within the material, not only weakening the overall high-temperature mechanical properties of the composite material but also potentially becoming a source of thermal crack initiation and propagation. In particular, under repeated high and low temperature alternation thermal shock environments, this reduces the reliability and service life of the brake disc.

[0051] On the other hand, traditional carbon-ceramic brake disc designs often employ a single homogeneous material structure or a simple two-dimensional laminated design. Homogeneous structures cannot effectively coordinate the significant temperature gradient and thermal stress distribution between the friction surface and internal regions of the brake disc during intense braking. As a result, thermal fatigue cracks easily form on the friction surface, leading to a decline in braking performance. Meanwhile, simple two-dimensional laminated structures rely excessively on the resin or pyrolytic carbon matrix between the layers as the load-bearing medium. Their inherent problem of insufficient interlayer strength is difficult to eliminate, making them prone to delamination failure under complex stress conditions (especially braking pressure), becoming a key bottleneck restricting the overall load-bearing capacity of the brake disc.

[0052] Based on this, the material structure and preparation process of the present invention are optimized to achieve a carbon ceramic brake disc that combines high-efficiency manufacturing, optimized microstructure control, and significantly improved overall service performance, meeting the needs of high-end braking systems such as aviation, rail transportation, and supercars.

[0053] The technical solutions of the embodiments of this application will be described in detail below, such as... Figure 1 As shown, a molding method for a carbon-ceramic brake disc blank with a layered composite structure according to the present invention includes the following steps:

[0054] S1: Preparation of high-density carbon fiber reinforced layer preform;

[0055] S2: Preparation of short fiber / particle-reinforced porous functional layer mixture;

[0056] S3: The high-density carbon fiber reinforced layer preform and the porous functional layer mixture are laid into the mold in a layered composite structure of upper high-density carbon fiber reinforced layer preform, middle porous functional layer mixture and lower high-density carbon fiber reinforced layer preform.

[0057] S4: Compression molding to obtain a carbon ceramic brake disc blank with a functional gradient structure.

[0058] Specifically, in step S1, the high-density carbon fiber reinforcement layer preform is a PAN-based carbon fiber fabric pre-impregnated with phenolic resin. The PAN-based carbon fiber fabric on the surface layer provides high flexural strength, which is greater than or equal to 100 MPa. Preferably, the carbon fiber fabric is at least one of plain weave, unidirectional weave, or twill weave. The specification of the carbon fiber fabric is, for example, T700SC-12K. In some embodiments, the resin content of the PAN-based carbon fiber fabric is 20wt%-50wt%, and the single-layer thickness is 0.25±0.05 mm. It is understood that the resin content of the PAN-based carbon fiber fabric can be any value within the range of 20wt%-50wt%. The single-layer thickness of the PAN-based carbon fiber fabric can also be any value within the range of 0.25±0.05 mm. For example, the resin content of the PAN-based carbon fiber fabric can be 46 wt%, 47 wt%, 48 wt%, etc., and the single-layer thickness of the PAN-based carbon fiber fabric can be 0.21 mm, 0.23 mm, 0.26 mm, 0.28 mm, etc. In this way, the carbon fiber fabric has a uniform composition, which is beneficial to its shear strength.

[0059] The choice of T700SC-12K PAN-based carbon fiber plain weave fabric for both the upper and lower layers is not accidental. While the commonly used T300 carbon fiber in existing technologies has a lower cost, its strength is only 3000MPa, which cannot meet the wear resistance requirements of the surface layer. The higher-performance T800 carbon fiber, although stronger, costs more than twice that of T700 and has poor wettability with phenolic resin. Through extensive experimental verification, this invention has determined that the combination of T700SC-12K carbon fiber and 20wt%-50wt% phenolic resin achieves the optimal balance between strength, cost, and wettability. Controlling the single-layer thickness to 0.25±0.05mm ensures the dimensional accuracy of the multilayer composite.

[0060] According to a preferred embodiment, the step of preparing the short fiber / particle-reinforced porous functional layer mixture in step S2 further includes:

[0061] S21: It is made by mixing short-cut carbon fibers, thermosetting phenolic resin powder, nano carbon powder, silicon carbide particles, pore-forming agent and dispersant in parts by weight.

[0062] Specifically, in step S21, the chopped carbon fibers can be machined carbon powder and its scraps to improve the recycling rate. In some embodiments, the length of the chopped carbon fibers is 5mm-20mm; it can be understood that the length of the chopped carbon fibers is any value within the range of 5mm-20mm; for example, the length of the chopped carbon fibers is 6mm, 12mm, 18mm, etc.; thus, the addition of chopped carbon fibers can effectively improve the overall strength of the intermediate porous functional layer and facilitate overall processing and preparation, making it suitable for large-scale production. The length of the chopped carbon fibers is controlled within the range of 5mm-20mm, which ensures the overlap strength between fibers while avoiding the problem of uneven dispersion caused by excessively long fibers.

[0063] In some exemplary embodiments, the thermosetting phenolic resin powder has good wetting ability and good molding performance, which is beneficial to improving the overall adhesion and stability of the intermediate porous functional layer structure. In some embodiments, the particle size of the thermosetting phenolic resin powder is 500-1000 mesh; it can be understood that the particle size of the thermosetting phenolic resin powder is any value between 500 mesh and 1000 mesh; exemplaryly, the particle size of the thermosetting phenolic resin powder is 656μm, 711μm, 800μm, etc. The small and relatively uniform particle size of the phenolic resin is beneficial to improving the mixing uniformity, thereby improving the adhesion reliability, structural uniformity, and structural stability of the structure. The particle size of the thermosetting phenolic resin powder of 500-1000 mesh ensures that it can be uniformly filled between the fibers and particles.

[0064] In some exemplary embodiments, the nano-carbon powder is nanoscale vapor-grown carbon powder with a particle size of 500-1000 mesh. The use of 500-1000 mesh vapor-grown carbon powder not only improves the thermal conductivity of the material but also promotes the uniform penetration of molten silicon due to its high specific surface area and electrical conductivity.

[0065] In some exemplary embodiments, the silicon carbide particles are 500-1000 mesh, and the mass ratio of carbon nanoparticles to silicon carbide particles is 1:(2-3). The silicon carbide particles, with a particle size of 500-1000 mesh, form an optimal mass ratio with the carbon nanoparticles, constructing a "micro-nano composite reinforcement" structure, which significantly improves the high-temperature stability of the material.

[0066] In some exemplary embodiments, the pore-forming agent is PMMA microspheres, 500-1000 mesh. The 500-1000 mesh size of the PMMA microsphere pore-forming agent precisely matches the porosity requirements of the intermediate layer. The pores formed after complete volatilization at high temperature can both relieve thermal stress and provide channels for the penetration of molten silicon.

[0067] In some exemplary embodiments, the dispersant is polyvinylpyrrolidone (PVP). PVP dispersant effectively solves the agglomeration problem of chopped carbon fibers and nanoparticles, improving the dispersion uniformity of each component by more than 60%.

[0068] Specifically, the porous functional layer mixture is dry-mixed to improve the thoroughness and uniformity of mixing. In some embodiments, the components of the porous functional layer mixture are mixed in parts by weight, with the following proportions: 20-30 parts of chopped carbon fiber (5mm-20mm in length); 15-20 parts of thermosetting phenolic resin powder (500-1000 mesh particle size); 10-15 parts of nano-carbon powder (500-1000 mesh); 25-35 parts of silicon carbide particles (500-1000 mesh); 5-8 parts of pore-forming agent (PMMA microspheres, 500-1000 mesh); and 0.5-1 part of dispersant (polyvinylpyrrolidone). It is understood that these parts by weight can be any of the above values, which will not be listed here. This facilitates integrated preparation for large-scale production.

[0069] Specifically, in some exemplary embodiments, before laying the high-density carbon fiber reinforced preform and the porous functional layer mixture into a mold, the method further includes:

[0070] S31: Preheat the mold to 80℃ and spray with release agent.

[0071] Specifically, in some exemplary embodiments, during the process of laying the porous functional layer mixture into the mold, i.e., in step S3, the method steps further include:

[0072] S32: The intermediate porous functional layer mixture is weighed in sections. During the process of laying the porous functional layer mixture into the mold, the intermediate porous functional layer mixture is weighed in sections to form a matrix with differences in powder density in the radial and circumferential directions.

[0073] When molding a carbon-ceramic brake disc preform with a functional gradient structure, the regions with different powder densities will form a rheological supplement located in the radial direction of the preform and a sandwich air duct structure on the circumferential side.

[0074] According to a preferred embodiment, several powder density difference regions of the porous functional layer mixture are arranged regularly or irregularly. The distance between two adjacent powder density difference regions is 10-30 mm. These powder density difference regions extend radially and circumferentially with different shapes to the edge of the porous functional layer. Preferably, the intermediate functional layer is divided into rings radially to form a central region, a transition region, and an edge region, resulting in a radial density gradient of "low at the center and high at the edge." The radial density gradient difference forms an inclined airflow channel. Preferably, the intermediate functional layer is divided circumferentially, resulting in alternating density fluctuations in the circumferential direction. The irregular structures formed by the bending extension of the powder density difference regions include at least one of spiral, wavy, and forked shapes. Preferably, all powder density difference regions extend to the edge of the functional layer, forming a density gradient network without dead angles.

[0075] The core concept of this invention is "functional gradient-oriented density differentiation design," focusing on the two-way density difference in the radial (center-edge) and circumferential (ring-shaped) directions of the intermediate functional layer. The difference regions are irregular structures with "curved extensions and different shapes," rather than the regular connecting holes or dimensional steps of the prior art. The spacing between the density difference regions in this invention is precisely controlled to 10-30mm (adapting to molding rheological compensation and airflow channel dimensions), and all difference regions extend to the edge of the porous functional layer, forming a continuous structure. This invention uses cross-regional weighing of radial rings (such as central rings, transition rings, and edge rings) and circumferential sectors (such as arc-shaped sectors and zigzag sectors) to create a radial density gradient of "low at the center and high at the edge" (edge ​​density is 15% higher than the center), and a circumferential density fluctuation. Each density difference region is a curved, extended irregular structure (such as spiral, wavy, or forked), with no repetition in shape and all extending to the edge of the functional layer, forming a density gradient network without dead angles. In this invention, during the molding process, the radial high-density region replenishes the low-density region through material rheology, while the circumferential irregular density region forms a natural curved air channel through rheological extrusion. The air channel wall is composed of a porosity gradient caused by the density difference (the high-density region is the air channel wall, and the low-density region is the air channel cavity), requiring no additional processing. During the molding process, due to the rheological effect of the material, the material in the edge area of ​​the brake disc tends to flow outward, resulting in a lower density than the central area. This problem has not been effectively solved in the prior art, making the strength and wear resistance of the finished product edge significantly lower than that of the central area, becoming a weak point in brake disc failure. This invention, through the coordinated design of partitioned weighing and molding, achieves "simultaneous completion of structural forming, strength enhancement, and air channel construction in a single molding process."

[0076] Specifically, the mold is pre-filled by preheating it to 80°C and spraying it with a silicone oil-based release agent. The lower layer of carbon cloth, the middle layer of mixture, and the upper layer of carbon cloth are then filled in sequence. The middle layer is weighed in sections, and the powder density in the edge area is increased by 15% to compensate for the loss of molding rheology.

[0077] Specifically, in some exemplary embodiments, the method further includes, during the process of molding a high-density carbon fiber reinforced layer preform and a porous functional layer mixture into a mold to obtain a carbon-ceramic brake disc blank with a functionally graded structure, the following steps are taken:

[0078] S41: Compression molding adopts a stepped pressure increase process, applying an initial pressure of 15±2MPa in the 100-120℃ range and a final pressure of 30±3MPa in the 150-160℃ range.

[0079] According to a preferred embodiment, the molding process includes the following stages:

[0080] S411: Pre-pressure exhaust stage: temperature 90-100℃, pressure 2-5MPa, time 5min;

[0081] S412: Curing Stage I: Temperature 120℃, Pressure 15MPa, Time 10min;

[0082] S413: Curing Stage II: Temperature 160℃, Pressure 30MPa, Time 30min, with a heating rate ≤5℃ / min, and pressure fluctuation ≤±0.5MPa during the holding stage.

[0083] The gradient molding process of this invention is divided into three stages, each with clearly defined technical objectives, forming an organic whole. The pre-compression and venting stage uses a low temperature of 90-100℃ and a low pressure of 2-5MPa to effectively expel air and volatiles from the material and avoid residual bubbles. If the temperature or pressure is too high in this stage, the resin will cure prematurely, which is detrimental to venting. The curing stage I increases the temperature to 120℃ and 15MPa to promote resin flow and wetting, ensuring tight interlayer bonding. The curing stage II further increases the temperature to 160℃ and 30MPa, allowing the resin to fully cross-link and cure, forming a high-strength three-dimensional network structure.

[0084] The heating rate at each stage is controlled within 5℃ / min. This is determined based on the curing kinetics of the resin. An excessively fast heating rate will lead to uneven resin curing and generate internal stress. The pressure fluctuation during the holding stage is controlled within ±0.5MPa to ensure the uniformity of material density.

[0085] According to a preferred embodiment, the compression molding method further includes post-processing steps, such as... Figure 2 As shown, the steps are as follows:

[0086] S42: Carbonization, heated to 800℃ in steps at a rate of 2℃ / min under nitrogen protection, and held at that temperature for 4 hours;

[0087] S43: Melting infiltration, vacuum silicon infiltration is carried out at 1600℃, in which the ratio of silicon ingot to silicon carbide is 3:1, and complete infiltration is achieved.

[0088] The vacuum degree of the melt infiltration process is 5×10-3 Pa, and the silicon infiltration time is 90 min;

[0089] The machining process employs laser drilling and diamond tool precision turning, with tolerances controlled within ±0.05mm.

[0090] This invention employs a stepped heating rate of 2℃ / min during the carbonization stage, which avoids oxidation of carbon fibers at high temperatures and allows for slow pyrolysis of the resin, forming a uniform pyrolytic carbon matrix. Holding at 800℃ for 4 hours ensures complete resin decomposition and reduces the impact of residual carbon. During the melting and infiltration stage, the ratio of silicon ingot to silicon carbide is controlled at 3:1, ensuring sufficient silicon source for the reaction while avoiding excessive silicon leading to free silicon enrichment. Complete infiltration ensures that silicon is mainly distributed on the outer surface and intermediate layers, forming a gradient distribution, improving the wear resistance of the surface layer while preventing excessive free silicon inside.

[0091] In the prior art, the structural design of carbon ceramic brake discs generally follows the idea of ​​"homogenization" or "simple stacking". Its core goal is to pursue the uniformity of material properties. However, the present invention takes the opposite approach and actively constructs a functional gradient structure of "high-density surface layer - porous intermediate layer - high-density bottom layer". This design concept is fundamentally different from the prior art.

[0092] The functionally graded structure of this invention is not a simple superposition of structures, but rather a meticulously designed structure based on the heat flow transfer patterns and stress distribution characteristics during braking. Finite element simulation analysis shows that this structure can reduce the thermal stress generated during braking by more than 40%, an effect that cannot be achieved by existing technologies. When faced with the technical problem of thermal stress concentration, those skilled in the art would conventionally choose to improve the overall strength or toughness of the material, rather than considering using a graded structure to disperse stress.

[0093] The functionally graded structure provides the structural basis for the gradient distribution of material properties, while the precise proportioning of layered materials endows this structure with corresponding properties. The gradient molding process ensures the stable realization of this structure and material composition, and edge density compensation solves the process defects in the molding process. The post-processing further optimizes the microstructure and properties of the material. Without the control of the gradient molding process, the porous structure of the intermediate functional layer cannot form a uniform pore distribution; and without the synergistic effect of nano-carbon powder and silicon carbide particles, even if a porous structure is formed, sufficient strength and wear resistance cannot be guaranteed. This overall synergistic effect enables the carbon ceramic brake disc of the present invention to achieve improvements in various performance indicators: bending strength ≥100MPa, friction coefficient stable at 0.5±0.05, and specific wear rate as low as 7.2×10-7mm³ / N・m.

[0094] Gradient molding, see Table 1 below:

[0095] Table 1 Gradient Molding

[0096]

[0097] Key controls: heating rate ≤ 5℃ / min, pressure fluctuation during the pressure holding stage ≤ ±0.5MPa.

[0098] Advantages of gradient functions:

[0099] The surface carbon cloth provides high flexural strength (measured flexural strength ≥100MPa), and the intermediate layer has a gradient porosity design (38% in the central area → 32% in the transition area → 25% in the bonding area) to optimize the molten silicon penetration path.

[0100] Example 2

[0101] This embodiment discloses a method for preparing a traditional homogeneous material, the steps of which include:

[0102] Step 1, Mixing:

[0103] Short-cut carbon fibers and phenolic resin are mixed according to a preset mass ratio of 30%–50% : 50%–70% to obtain a short-cut carbon fiber prepreg. The ratio is by mass percentage. This short-cut carbon fiber is composed of two types of carbon fibers with lengths of 15 mm and 30 mm mixed in a 1:1 ratio.

[0104] Step 2, Drying:

[0105] When drying short-cut carbon fiber prepreg, the drying temperature is 65-75℃ and the drying time is 2 hours.

[0106] Step 3, Press and solidify into shape:

[0107] The material is pressed and cured using a stepped pressurization and stepped heating method.

[0108] Step 4: Carbonization treatment to prepare pre-forms of automotive brake discs:

[0109] Example 3: Comparison between the carbon-ceramic brake disc preform with composite structure of the present invention and brake disc preforms prepared by traditional homogeneous materials.

[0110] Experimental Group 1: Carbon ceramic brake disc blanks were prepared using the same process as in Example 1.

[0111] Comparative Example 1: Brake disc preforms were prepared using the same process as in Example 2.

[0112] The present invention provides a carbon-ceramic brake disc blank, which is manufactured by compression molding method of carbon-ceramic brake disc blank with layered composite structure according to the above embodiment 1.

[0113] According to a preferred embodiment, the thermal conductivity of the carbon-ceramic brake disc blank prepared by the present invention is 30-50 W / m·K with consistent transverse and longitudinal properties, the coefficient of friction at 350℃ is 0.5±0.05, and the specific wear rate is 7.2×10⁻⁶. -7 mm 3 / N·m.

[0114] Table 2 compares the performance indicators of experimental group 1 and comparative example 1:

[0115] Table 2 Performance Indicators

[0116]

[0117] It should be noted that the specific embodiments described above are exemplary. Those skilled in the art can devise various solutions inspired by the disclosure of this invention, and these solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and do not constitute a limitation on the claims. The scope of protection of this invention is defined by the claims and their equivalents. This specification contains multiple inventive concepts; phrases such as "preferred" or "according to a preferred embodiment" indicate that the corresponding paragraph discloses an independent concept. The applicant reserves the right to file divisional applications based on each inventive concept. Throughout the text, the feature introduced by "preferred" is only an optional mode and should not be construed as mandatory. Therefore, the applicant reserves the right to abandon or delete relevant preferred features at any time.

Claims

1. A method for molding a carbon-ceramic brake disc blank with a layered composite structure, characterized in that, Includes the following steps: Preparation of high-density carbon fiber reinforced layer preforms; Preparation of short fiber / particle-reinforced porous functional layer mixtures; The high-density carbon fiber reinforced layer preform and the porous functional layer mixture are laid into the mold in a layered composite structure consisting of the upper high-density carbon fiber reinforced layer preform, the middle porous functional layer mixture and the lower high-density carbon fiber reinforced layer preform. Compression molding yields a carbon-ceramic brake disc preform with a functionally graded structure; wherein... During the process of laying the porous functional layer mixture into the mold, the intermediate porous functional layer mixture is weighed in sections to form a matrix with differences in powder density in the radial and circumferential directions. When molding a carbon-ceramic brake disc preform with a functional gradient structure, the regions with different powder densities will form a rheological supplement located in the radial direction of the preform and a sandwich air duct structure on the circumferential side.

2. The molding method for a carbon-ceramic brake disc blank with a layered composite structure according to claim 1, characterized in that, The porous functional layer mixture has several powder density difference regions arranged regularly or irregularly, with a spacing of 10-30 mm between two adjacent powder density difference regions. The powder density difference regions extend radially and circumferentially with different shapes to the edge of the porous functional layer.

3. The molding method for a carbon-ceramic brake disc blank with a layered composite structure according to claim 1, characterized in that, The high-density carbon fiber reinforced layer preform is a PAN-based carbon fiber fabric pre-impregnated with phenolic resin, with a resin content of 20wt%-50wt% and a single-layer thickness of 0.25±0.05mm.

4. The molding method for a carbon-ceramic brake disc blank with a layered composite structure according to claim 3, characterized in that, The step of preparing the short fiber / particle-reinforced porous functional layer mixture further includes: It is made by mixing short-cut carbon fibers, thermosetting phenolic resin powder, nano carbon powder, silicon carbide particles, pore-forming agent and dispersant in parts by weight.

5. The molding method for a carbon-ceramic brake disc blank with a layered composite structure according to claim 4, characterized in that, The porous functional layer mixture satisfies at least one of the following characteristics: The length of the short-cut carbon fiber is 5mm-20mm; The particle size of the thermosetting phenolic resin powder is 500-1000 mesh. The nano-carbon powder is nanoscale vapor-grown carbon powder with a particle size of 500-1000 mesh. The silicon carbide particles are 500-1000 mesh, and the mass ratio of the nano-carbon powder to the silicon carbide particles is 1:(2-3). The pore-forming agent is PMMA microspheres, 500-1000 mesh.

6. The molding method for a carbon-ceramic brake disc blank with a layered composite structure according to claim 1, characterized in that, In the process of molding the high-density carbon fiber reinforced preform and the porous functional layer mixture into a mold to obtain a carbon ceramic brake disc blank with a functional gradient structure, the molding process adopts a stepped pressure increase process, applying an initial pressure of 15±2MPa in the 100-120℃ range and a final pressure of 30±3MPa in the 150-160℃ range.

7. The molding method for a carbon-ceramic brake disc blank with a layered composite structure according to claim 1, characterized in that, The molding process includes the following stages: Pre-pressure exhaust stage: temperature 90-100℃, pressure 2-5MPa, time 5min; Curing Stage I: Temperature 120℃, Pressure 15MPa, Time 10min; Curing Stage II: Temperature 160℃, Pressure 30MPa, Time 30min, with a heating rate ≤5℃ / min, and pressure fluctuation ≤±0.5MPa during the holding stage.

8. The molding method for a carbon-ceramic brake disc blank with a layered composite structure according to claim 1, characterized in that, The compression molding method further includes a post-processing step, which involves: Carbonization was carried out by stepwise heating to 800℃ at a rate of 2℃ / min under nitrogen protection and holding at that temperature for 4 hours. Melting and infiltration are carried out under vacuum at 1600℃, with the ratio of silicon ingot to silicon carbide being 3:1, resulting in complete infiltration.

9. A carbon-ceramic brake disc blank, characterized in that, It is manufactured by the compression molding method of the carbon ceramic brake disc blank having a layered composite structure as described in any one of claims 1-9.

10. The carbon-ceramic brake disc blank according to claim 9, characterized in that, The thermal conductivity of the carbon-ceramic brake disc blank is 30-50 W / m·K, consistent in both the transverse and longitudinal directions, and the coefficient of friction at 350℃ is 0.5±0.05.

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