A method of reinforcing an engine case head

Abstract

This invention discloses a method for reinforcing engine housing heads in the field of engine housing manufacturing technology. First, based on the three-dimensional contour of the shoulder region of the head flange, a detachable specialized winding fixture is prepared. An elastic material layer with a hardness gradient is laid on the surface of the fixture, containing a multi-level porous network and a regularly distributed array of pits. Then, a carbon fiber yarn bundle is wound with pressure using a double-pressure roller device on the winding fixture. The roller spacing is adjusted to achieve precise pre-compaction. Finally, the reinforcing layer undergoes pre-compaction treatment and rotational isothermal curing. This invention, by setting up specialized fixtures and elastic material layers, achieves high-fidelity winding of complex curved surfaces, improves the density and interfacial bonding of the reinforcing layer, and the pit array and exhaust channel jointly suppress fuzzing, warping, and defect generation, thereby significantly improving local load-bearing capacity, reducing stress concentration, and extending the structural fatigue life.

Description

Technical Field

[0001] This invention relates to the field of engine housing manufacturing technology, and in particular to a method for reinforcing engine housing end caps. Background Technology

[0002] In aerospace liquid rocket engines, the combustion chamber shell, as the core load-bearing structure that withstands high-temperature and high-pressure gas loads, directly affects the overall safety and reliability of the engine. Currently, mainstream combustion chamber shell structures are generally manufactured using lightweight composite materials. These are formed by circumferentially or helically winding continuous fibers and epoxy resin systems on a CNC winding machine, creating a reinforced structure with high specific strength and high specific stiffness. While these structures typically possess excellent axial compressive strength and circumferential load-bearing capacity, significant weaknesses in local mechanical properties exist in areas of abrupt geometric changes—particularly at sharp angles or areas of rapid curvature transition between the flange shoulder and the shell—due to significant stress concentration effects.

[0003] Currently, the most widely used reinforcement method in the industry is to lay one or more layers of carbon fiber plain weave fabric as an additional reinforcing layer in the flange shoulder area. The plain weave fabric structure consists of intersecting warp and weft fiber bundles, with the fiber directions aligned circumferentially and axially, providing a balanced load-bearing capacity for tensile and shear loads in both directions. Therefore, this technology improves the overall strength of the structure to a certain extent, especially under conditions with large axial loads.

[0004] However, this reinforcement method has revealed several serious technical defects in practical applications: First, since the joint flange shoulder area is a typical strain concentration area, its actual stress state is mainly circumferential tension, while the axial stress is relatively small, showing the mechanical mismatch characteristics of "circumferential weakness and axial excess". When plain weave cloth is used for reinforcement, the fibers are evenly distributed along the axial and circumferential directions. This not only fails to specifically enhance the circumferential load-bearing capacity, but also introduces a large number of fibers arranged along the axial direction. These fibers play almost no role in the working load, but significantly increase the unit area mass of the structure.

[0005] Secondly, the interwoven warp and weft structure of plain weave fabric makes it prone to defects such as fiber slippage, layering wrinkling, and end curling during the winding process. Especially in areas with small radii of curvature or sharp points, the fibers cannot naturally adhere to the surface, forming obvious "accumulation areas" and "porosity areas," leading to local resin enrichment or dry spot defects. This severely reduces the interfacial bonding quality and becomes the initial source of fatigue crack initiation. Therefore, we propose a method for reinforcing engine casing heads. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for reinforcing engine housing heads. It utilizes an elastic material layer with a continuous hardness gradient and multi-stage exhaust paths, constructs a fiber pre-compaction control system based on the synergistic effect of a pressure roller and a flexible buffer layer, and combines this with a pre-forming temperature control mechanism based on resin rheological properties. This achieves directional, dense, and low-mass reinforcement of the circumferential stress concentration area in the flange shoulder region of the engine housing joint. This effectively solves key problems of traditional plain weave reinforcement methods, such as excessive negative mass, fiber slippage and wrinkling, poor exhaust flow, and poor interface bonding caused by directional mismatch. It significantly improves the load-bearing efficiency and service reliability of the reinforcement structure.

[0007] The objective of this invention is achieved as follows: a method for reinforcing an engine housing head, comprising the following steps:

[0008] S1. Based on the three-dimensional outline of the engine housing head and the joint flange shoulder area, a special winding tool is prepared for circumferential winding.

[0009] S2, a layer of elastic material is laid on the surface of the special winding tool to enhance friction, and then compacted by a vacuum device to form a pre-compacted surface;

[0010] S3, using a winding machine to perform pressure-assisted winding on the pre-compacted surface to form a reinforcing winding layer that matches the shape of the flange shoulder area;

[0011] S4, the reinforced winding layer that has been wound is pre-compacted by a pre-compression fixture, and then transferred to a curing device for rotary curing;

[0012] S5, fix the cured reinforcing wrapping layer to the flange shoulder area.

[0013] Optionally, the elastic material layer is disposed between the special winding tooling and the reinforcing winding layer. The elastic material layer exhibits a continuous hardness gradient in the thickness direction, with a low-hardness soft layer on the side closer to the tooling and a high-hardness support layer on the side closer to the fiber.

[0014] Optionally, the elastic material layer is provided with a pressure relief passage to discharge locally accumulated gas or resin residue during the fiber compaction process;

[0015] The pressure relief pathway is a multi-level porous network continuously distributed within the elastic material layer.

[0016] Optionally, the multi-level pore network is configured based on a hardness gradient, and the multi-level pore network includes an inlet region, a main channel region, and an outlet region;

[0017] The inlet area is an array of air inlets formed by a low-hardness layer of elastic material.

[0018] The main channel region is a main channel array of the intermediate layer of the elastic material layer;

[0019] The outlet area is a high-hardness layer of elastic material with an array of pressure-resistant holes.

[0020] The above three channels are connected to form a continuous exhaust path extending from the tooling surface to the fiber surface.

[0021] Optionally, the elastic material layer has an array of pits on the fiber contact surface, the array of pits being regularly distributed to physically limit the fiber ends during the winding process.

[0022] Optionally, the pressure-assisted winding includes the following steps:

[0023] S31, a pair of adjustable-gap pressure rollers are set at the output end of the winding machine to apply pre-compacting pressure to the fiber yarn bundle;

[0024] S32, A flexible buffer layer is provided in the gap between the two pressure rollers;

[0025] The thickness of the flexible buffer layer is less than the set thickness value of the reinforcing winding layer;

[0026] S33, based on the mathematical relationship between the pressure roller spacing and the target winding layer thickness, adjusts the spacing between the two pressure rollers;

[0027] S34, the fiber bundle passes through the first pressure roller, the flexible buffer layer and the second pressure roller in sequence, and is pre-compressed into a dense bundle structure close to the thickness of the target winding layer before contacting the tooling surface;

[0028] S35, finally, the pre-compressed fiber yarn bundle is continuously wound in a circumferential direction on the surface of a special winding tool to form a circumferential reinforcing winding layer.

[0029] Optionally, the mathematical relationship between the distances between the two pressure rollers is as follows:

[0030]

[0031] In the formula: To adjust the spacing between the pressure rollers;

[0032] The target winding layer thickness;

[0033] The thickness of the flexible buffer layer;

[0034] is the compression deformation coefficient of the fiber during the pre-compaction process.

[0035] Optionally, the compressibility coefficient is taken as:

[0036]

[0037] In the formula: This refers to the actual thickness of the winding layer;

[0038] The compressive deformation coefficient was obtained through preliminary experiments, specifically:

[0039] Using carbon fiber yarn, resin, and winding yarn under the same conditions as the formal process, a complete circumferential winding is performed on a standard tooling, and the actual winding layer thickness is measured.

[0040] Optionally, before the pressure-assisted winding begins, the rheological properties of the resin system are tested, and the pre-forming temperature value of the reinforcing winding layer is set, specifically:

[0041] The resin sample was placed in a rheometer and heated from room temperature to 200°C at a heating rate of 5°C / min. The viscosity-temperature curve was collected in real time, and the temperature corresponding to the lowest viscosity point was determined.

[0042] The pre-forming temperature of the reinforcing winding layer is set based on the temperature value of the lowest viscosity point.

[0043] The winding fixture is heated to the pre-forming temperature and subjected to constant temperature treatment, followed by pressure winding in this temperature environment.

[0044] Optionally, the mathematical relationship between the preforming temperature of the reinforcing winding layer and the temperature at the lowest viscosity point is as follows:

[0045] ;

[0046] In the formula, a is the temperature corresponding to the lowest viscosity point;

[0047] b represents the pre-forming temperature value of the reinforcing winding layer.

[0048] Compared with existing technologies, the advantages of this invention are as follows: Traditional methods rely on a plain weave fabric structure with interwoven fibers, where the fibers are evenly distributed in the circumferential and axial directions. However, this area mainly bears the circumferential tensile load, and the axial fibers cannot effectively participate in the stress, resulting in material waste and structural redundancy. Furthermore, plain weave fabrics are prone to fiber slippage, layer wrinkling, and end curling during winding on complex curved surfaces, especially in areas with abrupt curvature changes where tight bonding is impossible, leading to localized accumulation and dry spot defects, severely affecting interlayer bonding performance and becoming a source of fatigue damage. This invention, by employing a high-precision, specialized winding fixture oriented towards the actual geometry, ensures that the reinforcing layer completely conforms to the three-dimensional contour of the flange shoulder area, guaranteeing accurate and deviation-free fiber paths and fundamentally avoiding wrinkling and porosity.

[0049] Secondly, this invention achieves comprehensive and precise control over the fiber laying process by introducing a gradient functionalized elastic material layer. This elastic material layer not only possesses flexibility and high adaptability, automatically filling minor unevenness and local gaps on the tooling surface, but also incorporates multi-level interconnected venting paths to efficiently remove gas and resin residues, greatly reducing the risk of internal defect formation. Simultaneously, a regularly distributed pit structure on its surface actively physically limits and anchors the fiber ends, forming a mechanical locking effect that significantly enhances the interface's shear and peel resistance, greatly improving the bonding strength between the reinforcing layer and the parent structure. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0051] Figure 1 This is a flowchart of the steps of the engine housing head reinforcement method provided by the present invention.

[0052] Figure 2 This is a schematic diagram of the pressure-assisted winding process provided by the present invention.

[0053] Figure 3 This is a schematic diagram of the shoulder area of ​​the connector flange provided by the present invention.

[0054] Figure 4 This is a schematic diagram of the process framework for the engine housing head reinforcement method provided by the present invention.

[0055] In the diagram, 1 represents the winding reinforcement area. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] like Figures 1 to 4This invention discloses a method for reinforcing engine housing heads. The entire process revolves around constructing a high-precision, high-density circumferential reinforcing structure. Its core lies in the effective reinforcement of the complex curved surface of the flange shoulder area at the engine housing head through the structural design of a specialized winding tooling, the gradient functionalization of the elastic material layer, the construction of a multi-stage exhaust path, the establishment of a fiber pre-compaction control system, and the precise control of the pre-forming temperature field. During service, this reinforcing structure can significantly improve local load-bearing capacity, reduce stress concentration, and effectively suppress the initiation of microcracks caused by the coupling effect of thermal cycling and mechanical loads.

[0058] The process includes the following steps: S1, based on the three-dimensional outline of the engine housing head and the joint flange shoulder area, prepare a special winding tool for circumferential winding;

[0059] Specifically, the preparation of the specialized winding fixture involved in step S1 is the foundation of the entire process. This fixture uses the actual three-dimensional outline of the flange shoulder area at the engine housing head as the modeling reference, acquiring its surface geometric data. After obtaining measured point cloud data through 3D scanning, it is digitally reconstructed using modeling software to generate a 3D solid model. Subsequently, the fixture is manufactured using high-performance titanium alloy or high-strength aluminum alloy through CNC precision machining to ensure the fit between the subsequent winding layer and the parent structure. The specialized winding fixture is designed as a detachable ring structure, equipped with a positioning reference surface and axial limiting pins, facilitating rapid clamping and high repeatability positioning accuracy on the winding machine.

[0060] Specifically, in S2, an elastic material layer is laid on the surface of the special winding tool to enhance friction, and then compacted by a vacuum device to form a pre-compacted surface.

[0061] The elastic material layer is placed between the special winding tooling and the reinforcing winding layer. The elastic material layer has a continuous hardness gradient in the thickness direction. The side closer to the tooling is a low-hardness soft layer, and the side closer to the fiber is a high-hardness support layer.

[0062] Furthermore, an elastic material layer is laid on the surface of the special winding tool. This step is used to prevent the composite material layers from sticking together, thereby improving the demolding performance and achieving tight edge adhesion. The elastic material layer is not an ordinary rubber gasket, but a sandwich structure based on composite materials, which has multi-level gradient hardness distribution characteristics.

[0063] Furthermore, the elastic material layer exhibits a continuous stiffness transition along its thickness. The side closer to the tooling is a low-hardness soft layer, typically composed of silicone or PU elastomers, possessing excellent elastic recovery and interfacial adaptability, capable of fully filling microscopic unevenness and tiny gaps on the tooling surface. The side closer to the fiber contact surface is a high-hardness support layer, made of modified epoxy resin matrix and chopped carbon fiber reinforcement, its main function being to provide compressive support and geometric positioning guidance for subsequent fiber paths. The middle region is a transition layer; by adjusting the filler ratio and curing regime, a continuous nonlinear hardness curve is formed, causing the overall material to produce a gradual deformation response under load, avoiding interfacial delamination or stress concentration caused by abrupt changes in rigidity.

[0064] Specifically, the elastic material layer has a pressure relief channel inside, which is used to release locally accumulated gas or resin residue during the fiber compaction process;

[0065] The pressure relief pathway is a multi-level porous network continuously distributed within the elastic material layer.

[0066] Specifically, the multi-level pore network is set based on the hardness gradient, and the multi-level pore network includes an inlet region, a main channel region, and an outlet region;

[0067] The inlet area is an array of air inlets made of a low-hardness layer of elastic material.

[0068] The main channel region is the main channel array of the intermediate layer of the elastic material layer;

[0069] The outlet area is an array of pressure-resistant pores in a high-hardness layer of elastic material;

[0070] The above three channels are connected to form a continuous exhaust path extending from the tooling surface to the fiber surface.

[0071] Furthermore, the elastic material layer is internally configured with pressure relief pathways, employing a multi-level porous network structure. The distribution design of this network is synergistically optimized based on the hardness gradient of the material layer. The multi-level porous network comprises three functional zones: an inlet zone, a main channel zone, and an outlet zone. These three zones are spatially connected by interconnected microchannels, forming a continuous exhaust path extending from the tooling surface to the surface of the composite fiber layer.

[0072] The inlet area is located in the low-hardness region of the elastic material layer. Its pore structure is an array of air inlets, with the pore depth gradually increasing from the surface to the inside, effectively capturing the escape demand of the initial gas accumulation area.

[0073] The main channel region is located in the intermediate layer and is a linear array of main channels with a length that runs through the entire thickness of the intermediate layer. It utilizes capillary effect and pressure difference to achieve directional gas guidance.

[0074] The outlet area is located in the high-hardness support layer and is set as a pressure-resistant hole array. The surface of the hole wall is hydrophobically treated (such as fluorination) to avoid resin wetting and clogging, and to ensure that the passage remains unobstructed during high-pressure compaction.

[0075] The structural design of the entire multi-level porous network is based on a numerical simulation model. By simulating the resin flow and gas diffusion behavior during the fiber yarn laying process, the optimal pore distribution density and path continuity parameters are determined to ensure maximum venting during the pre-compaction stage and significantly reduce the risk of bubble and resin residue accumulation.

[0076] Specifically, the elastic material layer has an array of pits on the fiber contact surface. The array of pits is regularly distributed and is used to physically limit the fiber ends during the winding process.

[0077] Furthermore, the elastic material layer has an array of pits on its outer surface that is in direct contact with the fibers. This array is constructed on the surface of the low-hardness layer. The shape of the pits is preferably a regular circle or a regular hexagon, with a diameter controlled in the range of 0.8mm to 1.5mm and a depth of 0.3mm to 0.6mm. The center-to-center spacing between adjacent pits is set between 3mm and 5mm, forming a regular square or hexagonal densely distributed structure, which has a high degree of spatial consistency and processing repeatability.

[0078] This array of pits not only serves as a physical limiting structure for the fiber ends, effectively preventing the fibers from shifting, loosening, or accumulating locally during circumferential winding due to uneven tension, insufficient friction, or interlayer slippage, but also achieves active interlocking and microscopic anchoring of the fiber bundle ends during the pre-compaction stage: when the pressure roller applies pressure, the fiber end material is forced into the pits, forming a "mechanical locking" effect, which significantly increases the interface's resistance to shearing and peeling.

[0079] This structure constructs a three-dimensional anchoring network at the microscopic level, greatly enhancing the interfacial bonding force between the fiber bundle and the resin matrix, effectively suppressing microcrack initiation and interfacial debonding. Laboratory tests based on multiple comparative experiments show that, compared to traditional flat tooling, the reinforcement structure equipped with the pit array increases the fiber end delamination strength by an average of 38.2%, while significantly reducing fiber fuzzing and curling rates during winding, and substantially improving surface quality and interlayer density.

[0080] In addition, while maintaining the overall structural integrity of the high-rigidity support layer, the array structure does not interfere with the ventilation function of the main channel area, thereby achieving multi-dimensional synergy of positioning and limiting, interface enhancement and exhaust connection.

[0081] Furthermore, the elastic material layer is not simply composed of a superposition of structures such as gradient hardness, multi-level pore network and pit array. During the fiber laying and compaction process, the system achieves multiple synergies of stress transmission path optimization, gas escape path guidance, fiber anchoring position preset and structural stability maintenance.

[0082] Specifically, the low-hardness soft layer serves as the system's inlet area. Its air inlet array not only possesses excellent initial airflow capture capabilities but also generates local elastic displacement with the irregular deformation of the tooling surface, actively filling micro-gaps and ensuring full contact and fit with the tooling. This layer also serves as the supporting matrix for the pit array. Its moderate flexibility allows the fiber ends to undergo controllable embedding deformation under the action of the pressure roller, achieving precise positioning and mechanical locking, preventing slippage and accumulation. The intermediate transition layer establishes a smooth transition in stiffness through a continuous hardness gradient, preventing stress concentration at the interface and providing structural support for the internal main channel area, ensuring that the main channel remains unobstructed under high pressure, and avoiding blockage caused by resin migration or bubble collapse. The main channel area further achieves directional guidance of gas and resin residue through a regularly distributed main channel array. Its length and distribution density are optimized through numerical simulation and dynamically matched with the free space between fiber bundles. Finally, the pressure-resistant hole array of the high-hardness support layer serves as the outlet area. While maintaining the integrity of the overall structure, it ensures that gas is discharged with minimal resistance, and the hole walls are hydrophobically treated to prevent resin infiltration and blockage of the passage.

[0083] Furthermore, the three functional zones do not operate independently, but rather form a multi-dimensional collaborative mechanism involving space, mechanics, and fluid. The flexible deformation of the low-hardness layer leads to fine-tuning of the pit position, achieving continuous anchoring of the fiber ends. The unobstructed flow of the main channel depends on the stiffness support of the intermediate layer, while the maintenance of stiffness depends on the resistance of the high-hardness layer to local pressure, thus forming a closed-loop feedback system. This system maintains dynamic equilibrium throughout the process of the fiber transitioning from a fluffy state to a dense state, thereby achieving high-fidelity, high-density, and defect-free reinforcement of complex curvature regions without relying on external stable support.

[0084] S3, using a winding machine to perform pressure-assisted winding on the pre-compacted surface to form a reinforcing winding layer that matches the shape of the flange shoulder area;

[0085] Specifically, the pressure-assisted winding includes the following steps:

[0086] S31, a pair of adjustable-gap pressure rollers are set at the output end of the winding machine to apply pre-compacting pressure to the fiber yarn bundle;

[0087] S32, a flexible buffer layer is provided in the gap between the two pressure rollers;

[0088] The thickness of the flexible buffer layer is less than the set thickness value of the reinforcing winding layer;

[0089] S33, based on the mathematical relationship between the pressure roller spacing and the target winding layer thickness, adjusts the spacing between the two pressure rollers;

[0090] S34, the fiber bundle passes through the first pressure roller, the flexible buffer layer and the second pressure roller in sequence, and is pre-compressed into a dense bundle structure close to the thickness of the target winding layer before contacting the tooling surface;

[0091] S35, finally, the pre-compressed fiber yarn bundle is continuously wound in a circumferential direction on the surface of a special winding tool to form a circumferential reinforcing winding layer.

[0092] Furthermore, during the pressure-assisted winding process, the winding machine is also equipped with an adjustable-gap double pressure roller device. The two pressure rollers are controlled in coordination by a precision ball screw driven by a servo motor and a closed-loop feedback system to achieve dynamic adjustment of the pressure roller gap at the millimeter or even micrometer level. This ensures that the target pressing parameters can be automatically matched under different yarn tension, linear path and multi-layer winding conditions, effectively guaranteeing the stability and consistency of the pre-compaction process.

[0093] A flexible buffer layer is set between the two pressure rollers. The flexible buffer layer is preferably a polytetrafluoroethylene elastic composite film. Its matrix is ​​a high molecular elastomer (such as thermoplastic polyurethane TPE or silicone rubber) and its surface is coated with PTFE. It has an ultra-low coefficient of friction and excellent anti-adhesion properties. It can prevent fibers from sticking to the pressure rollers, fuzzing or delamination in high resin content environments. At the same time, it has good fatigue resistance, heat resistance and quiet operation characteristics.

[0094] It should be noted that the thickness of the flexible buffer layer is strictly less than the target thickness of the reinforcing winding layer to ensure that the fiber bundle is close to the target thickness in its final dense state after being pre-compressed by the pressure roller, thus avoiding fiber damage or structural collapse due to excessive compression. At the same time, its good elastic recovery performance can quickly release stress during the retraction of the pressure roller, preventing residual deformation or interlayer separation of the fiber bundle during relaxation and loading cycles.

[0095] In addition, the flexible buffer layer can be designed with a microporous structure or surface microtexturation, which has a certain degree of air permeability. It can help to expel some volatile components during the pre-compaction stage, further improving the uniformity of pre-lay density. This method can not only reduce defects such as fiber slippage, wrinkling and end fuzzing in the early stage of winding, but also effectively improve the interlayer density and overall contour fidelity of the subsequent circumferential winding layer, so that the reinforcement structure has better compression resistance, shear resistance and fatigue resistance under high load conditions.

[0096] Specifically, the mathematical relationship between the distance between the two pressure rollers is as follows:

[0097]

[0098] In the formula: To adjust the spacing between the pressure rollers;

[0099] The target winding layer thickness;

[0100] The thickness of the flexible buffer layer;

[0101] is the compression deformation coefficient of the fiber during the pre-compaction process.

[0102] Furthermore, carbon fiber bundles, in their uncompacted state, exhibit a loose, low-density structure (porosity often exceeding 40%). When they enter between the two pressure rollers, they undergo multi-stage compression under the pressure:

[0103] First stage: Free fibers on the surface of the fiber bundle undergo initial densification through shear slip and local bending;

[0104] Second stage: The pores between the internal fiber bundles are squeezed out, and the resin undergoes micro-migration and filling;

[0105] The third stage: Local plastic deformation and accumulation occur at the contact points between the fibers, resulting in irreversible thickness compression (i.e., "permanent compression").

[0106] This process exhibits nonlinear, inelastic, and dynamic behavior strongly coupled with contact pressure, time, and frequency. Experiments show that under typical roller contact pressures of 200 kPa to 600 kPa, the compression of a single-layer carbon fiber yarn bundle can result in a thickness loss of 15% to 30%. This loss is not uniformly distributed but depends on yarn tension, prepreg resin content, resin flowability, and winding speed.

[0107] Therefore, if the target thickness is used directly as the reference for the distance between the pressure rollers, the final thickness will be lower than the design value, resulting in an "over-compression" effect. To address this, a compression deformation coefficient must be introduced to compensate for the compression process. This means that a compression space must be reserved before the pressure rollers contact each other, so that the fiber has sufficient thickness to be compressed during the pressing process, ultimately reaching the target thickness.

[0108] Secondly, the flexible buffer layer combines low friction, anti-adhesion, impact resistance, and elastic recovery properties, but it also has its own thickness. Under the action of the pressure roller, it will undergo elastic deformation, and the compression amount is approximately ( The material's compressibility modulus. (This refers to the contact pressure). If this compression contribution is ignored, the gap between the pressure rollers will be too large, resulting in insufficient clamping force.

[0109] Specifically, the compressibility coefficient is set to:

[0110]

[0111] In the formula: This refers to the actual thickness of the winding layer;

[0112] The compressive deformation coefficient was obtained through preliminary experiments, specifically:

[0113] Using carbon fiber yarn, resin, and winding yarn under the same conditions as the formal process, a complete circumferential winding is performed on a standard tooling, and the actual winding layer thickness is measured.

[0114] Furthermore, in the pressure-assisted winding process, the compression coefficient is obtained through a pre-experiment that completely simulates the formal process conditions. Specifically, on standard tooling, using the exact same carbon fiber yarn, resin system, winding path, tension control method, linear speed, and pressure roller pressure as in formal production, a complete circumferential winding process is completed. After winding, a high-precision laser thickness gauge or X-ray tomography is used to measure the thickness of the formed winding layer at multiple points. The average value is taken as the actual winding layer thickness, and the compression coefficient is calculated based on this.

[0115] By conducting experiments under real-world working conditions, we captured the compression behavior of carbon fiber and resin during the actual compression process, thereby obtaining the most accurate compression loss under these process conditions.

[0116] The advantage of this method lies in the shift from subjective experience to objective data. Relying on the operator's "feel" or "historical experience" not only introduces significant uncertainty but also makes it difficult to replicate across different batches and equipment. In contrast, parameters determined through pre-experiments are highly traceable, repeatable, and verifiable. Once established, they can be stored as templates in the system for subsequent production using the same material and process combinations, shortening the process debugging cycle. Furthermore, actual compression results avoid deviations in the pressure roller spacing settings caused by theoretical estimation errors, thus significantly improving the consistency of the final formed layer thickness.

[0117] Specifically, before the pressure-assisted winding begins, the rheological properties of the resin system are tested, and the pre-forming temperature of the reinforcing winding layer is set, specifically:

[0118] The resin sample was placed in a rheometer and heated from room temperature to 200°C at a heating rate of 5°C / min. The viscosity-temperature curve was collected in real time, and the temperature corresponding to the lowest viscosity point was determined.

[0119] The pre-forming temperature of the reinforcing winding layer is set based on the temperature value of the lowest viscosity point.

[0120] The winding fixture is heated to the pre-forming temperature and subjected to constant temperature treatment, followed by pressure winding in this temperature environment.

[0121] The mathematical relationship between the preforming temperature of the reinforcing winding layer and the temperature at the lowest viscosity point is as follows:

[0122] ;

[0123] In the formula, a is the temperature corresponding to the lowest viscosity point;

[0124] b represents the pre-forming temperature value of the reinforcing winding layer.

[0125] Furthermore, in the experiment, typical resin samples were selected and placed in a rheometer using a parallel plate clamp with a clamp spacing of 1.0 mm. The samples were heated from room temperature to 200°C at a heating rate of 5°C / min. Shear viscosity values ​​were collected every 1°C during the heating process, and the complete viscosity-temperature curve was recorded. Based on the measured data, the temperature corresponding to the lowest viscosity point was identified and denoted as a°C. This temperature point is the optimal flow window temperature of the resin system, indicating that the resin molecular chains are most mobile, have the best flowability, and the strongest wetting ability for fibers at this temperature.

[0126] This temperature difference setting is intended to allow sufficient time for structural shaping during the pre-compaction stage while ensuring good resin flowability. It prevents premature resin thickening due to excessively high temperatures, which would cause loss of compressibility. Therefore, heating and maintaining a constant temperature of the winding fixture ensures that the fixture surface remains in a stable thermal environment throughout the entire pressure-assisted winding process. This allows the fiber bundles to enter the fixture surface in a low-viscosity, highly wettable state, which is beneficial for achieving dense layup.

[0127] S4, the reinforced winding layer that has been wound is pre-compacted by a pre-compression fixture, and then transferred to a curing device for rotary curing;

[0128] S5, fix the cured reinforcing wrapping layer to the flange shoulder area.

[0129] Furthermore, after the winding is completed, a pre-compression fixture is used to pre-compact the completed reinforcing winding layer. This pre-compression fixture matches the inner cavity of the winding fixture, applies pressure, and holds the pressure for no less than 15 minutes. This step can further remove microbubbles, promote resin flow, and densify the fiber transition zone, providing a good structural foundation for subsequent curing.

[0130] After pre-compaction, the entire component is transferred to the rotary curing device for thermal curing. During the entire curing process, the fixture rotates at a constant speed to ensure uniform heat distribution and avoid local overheating or uneven curing that could lead to internal stress accumulation.

[0131] Finally, the cured reinforcing wrapping layer is fixedly connected to the flange shoulder area of ​​the engine housing head. This connection adopts a composite connection method of bolt pre-tightening and structural adhesive bonding. At the same time, epoxy structural adhesive is applied to the contact surface and pressure is applied. After 24 hours of complete curing, a high-strength and high-sealing integrated structure is obtained.

[0132] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for reinforcing the end cap of an engine casing, characterized in that, Includes the following steps: S1. Based on the three-dimensional outline of the engine housing head and the joint flange shoulder area, a special winding tool is prepared for circumferential winding. S2, a layer of elastic material is laid on the surface of the special winding tool to enhance friction, and then compacted by a vacuum device to form a pre-compacted surface; S3, using a winding machine to perform pressure-assisted winding on the pre-compacted surface to form a reinforcing winding layer that matches the shape of the flange shoulder area; S4, the reinforced winding layer that has been wound is pre-compacted by a pre-compression fixture, and then transferred to a curing device for rotary curing; S5, fix the cured reinforcing wrapping layer to the flange shoulder area.

2. The method for reinforcing an engine housing head according to claim 1, characterized in that: The elastic material layer is disposed between the special winding tooling and the reinforcing winding layer. The elastic material layer exhibits a continuous hardness gradient in the thickness direction, with a low-hardness soft layer on the side closer to the tooling and a high-hardness support layer on the side closer to the fiber.

3. The method for reinforcing an engine housing head according to claim 2, characterized in that: The elastic material layer is provided with a pressure relief passage to discharge locally accumulated gas or resin residue during the fiber compaction process. The pressure relief pathway is a multi-level porous network continuously distributed within the elastic material layer.

4. The method for reinforcing an engine housing head according to claim 3, characterized in that: The multi-level pore network is set based on a hardness gradient, and the multi-level pore network includes an inlet region, a main channel region, and an outlet region; The inlet area is an array of air inlets formed by a low-hardness layer of elastic material. The main channel region is a main channel array of the intermediate layer of the elastic material layer; The outlet area is a high-hardness layer of elastic material with an array of pressure-resistant holes. The above three channels are connected to form a continuous exhaust path extending from the tooling surface to the fiber surface.

5. The method for reinforcing an engine housing head according to claim 3, characterized in that: The elastic material layer has an array of pits on the fiber contact surface. The array of pits is regularly distributed and is used to physically limit the fiber ends during the winding process.

6. The method for reinforcing an engine housing head according to claim 1, characterized in that: The pressure-assisted winding includes the following steps: S31, a pair of adjustable-gap pressure rollers are set at the output end of the winding machine to apply pre-compacting pressure to the fiber yarn bundle; S32, A flexible buffer layer is provided in the gap between the two pressure rollers; The thickness of the flexible buffer layer is less than the set thickness value of the reinforcing winding layer; S33, based on the mathematical relationship between the pressure roller spacing and the target winding layer thickness, adjusts the spacing between the two pressure rollers; S34, the fiber bundle passes through the first pressure roller, the flexible buffer layer and the second pressure roller in sequence, and is pre-compressed into a dense bundle structure close to the thickness of the target winding layer before contacting the tooling surface; S35, finally, the pre-compressed fiber yarn bundle is continuously wound in a circumferential direction on the surface of a special winding tool to form a circumferential reinforcing winding layer.

7. The method for reinforcing an engine housing head according to claim 6, characterized in that: The mathematical relationship between the distances between the two pressure rollers is as follows: ； In the formula: To adjust the spacing between the pressure rollers; The target winding layer thickness; The thickness of the flexible buffer layer; is the compression deformation coefficient of the fiber during the pre-compaction process.

8. The method for reinforcing an engine housing head according to claim 7, characterized in that: The value of the compression deformation coefficient is: ； In the formula: This refers to the actual thickness of the winding layer; The compressive deformation coefficient was obtained through preliminary experiments, specifically: Using carbon fiber yarn, resin, and winding yarn under the same conditions as the formal process, a complete circumferential winding is performed on a standard tooling, and the actual winding layer thickness is measured.

9. A method for reinforcing an engine housing head according to claim 1, characterized in that: Before the pressure-assisted winding begins, the rheological properties of the resin system are tested, and the pre-forming temperature value of the reinforcing winding layer is set, specifically: The resin sample was placed in a rheometer and heated from room temperature to 200°C at a heating rate of 5°C / min. The viscosity-temperature curve was collected in real time, and the temperature corresponding to the lowest viscosity point was determined. The pre-forming temperature of the reinforcing winding layer is set based on the temperature value of the lowest viscosity point. The winding fixture is heated to the pre-forming temperature and subjected to constant temperature treatment, followed by pressure winding in this temperature environment.

10. A method for reinforcing an engine housing head according to claim 9, characterized in that: The mathematical relationship between the preforming temperature of the reinforcing winding layer and the temperature at the lowest viscosity point is as follows: ； In the formula, a is the temperature corresponding to the lowest viscosity point; b represents the pre-forming temperature value of the reinforcing winding layer.

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