A right-angle male die forming process for composite parts

Abstract

This invention discloses a process for forming right-angle male molds for composite material parts, comprising the following steps: Step A, fabric cutting; Step B, sheet laying; Step C, twisting and directional filling; Step D, outer skin constraint laying; Step E, mold closing and hot pressing pre-forming; Step F, segmented curing and forming. The beneficial effects of this invention are: by constructing an integrated forming system of "precise cutting - stepped pre-pressing - directional filling - closed-loop constraint - gradient hot pressing - segmented curing" through the above steps, it overcomes the limitations of isolated operations in traditional processes. Through dimensional accuracy control of ≤±0.5mm in the fabric cutting stage, and directional scraping and stepped vacuum pre-pressing in the sheet laying stage, the tightness of interlayer bonding is ensured from the source, significantly reducing interlayer porosity and avoiding the wrinkle accumulation problem easily caused by multi-layer laying. This lays a high-precision foundation for subsequent right-angle forming, and its process system and controllability are significantly superior to existing extensive forming methods.

Description

Technical Field

[0001] This invention relates to a process for forming right-angle male molds for composite material parts. Background Technology

[0002] With the rapid development of high-end fields such as aerospace, automotive, shipbuilding, and new energy, stringent requirements have been placed on the structural precision, mechanical properties, and dimensional stability of composite material parts. This is especially true for composite material parts with right-angle structures, which are increasingly widely used in various high-end equipment due to the need to balance high load-bearing capacity with precise assembly adaptability. However, existing molding processes for right-angle composite material parts still face numerous technical bottlenecks, making it difficult to meet actual application needs.

[0003] Traditional molding processes often employ a crude operational model, lacking coordinated design between processes and resulting in isolated operations. This leads to insufficient systematization and controllability of the process. In the fabric cutting stage, dimensional accuracy control is rudimentary, resulting in significant errors in the edge contours of the fabric sheets, creating potential accuracy risks for subsequent laying and molding. During fabric laying, positioning methods are rudimentary, interlayer air venting is insufficient, and a scientific pre-compression strategy is lacking. The common practice of uniform interval pre-compression or overall pre-compression not only easily leads to residual air between layers and high porosity but also frequently causes wrinkle accumulation, severely affecting the tightness of interlayer bonding. Regarding the filling of right-angle areas, existing technologies mostly rely on conventional prepreg laying, which easily creates transitional radius corners, failing to guarantee the regularity of the right-angle contour. This also results in core problems such as fiber breakage, insufficient adhesive, and uneven filling, making it difficult to balance the contour accuracy and fiber continuity of the right-angle structure, thus turning right-angle areas into structural weak points.

[0004] In the constraint and curing stages, traditional processes lack an effective closed-loop constraint mechanism, making the filler layer prone to displacement and deformation during molding, further exacerbating deviations in right-angle contours. Inadequate design of hot-pressing and curing process parameters, often employing constant-pressure heating and uniform-rate cooling, easily leads to thermal stress accumulation and internal stress concentration, resulting in defects such as cracking and deformation after cooling. Furthermore, the direct contact between the hard mold and the part surface during mold closing easily causes surface wear, affecting the part's appearance quality and structural integrity. Simultaneously, existing processes lack sufficient quantitative control over key parameters, resulting in poor dimensional consistency and low yield rates in finished products. Moreover, some processes rely on specialized high-end equipment, leading to high production barriers and limited industrial application.

[0005] The numerous defects of the aforementioned traditional processes make it difficult for the molded composite material right-angle parts to meet the stringent standards of high-end fields in terms of right-angle deviation, edge fillet radius, and mechanical property stability, which seriously restricts the promotion and application of composite material right-angle parts in high-end equipment such as aerospace, automobiles, and ships.

[0006] In view of this, the present invention proposes a process for forming right-angle male molds for composite material parts to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a process for forming right-angle male molds for composite material parts, so as to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for forming a right-angle male mold for composite material parts includes the following steps:

[0010] Step A: Cutting the fabric:

[0011] According to the layup diagram, use a CNC fabric cutting machine or a high-precision hand cutting method to cut the material, ensuring that the edge contour accuracy error of the material sheet is ≤ ±0.5mm;

[0012] Step B, Sheet Laying:

[0013] Precise material sheet placement is achieved by positioning with a projector or tooling engraving. Material sheets are sequentially placed in the right-angle forming area of ​​the male mold. After each layer of material sheet is placed, a special scraping tool is used to scrape and press out air in one direction along the fiber direction. After the first layer is placed, a vacuum pre-compression is performed. Subsequent vacuum pre-compression is performed every 2-3 layers to form a stepped pre-compression structure.

[0014] Step C, Twisting and Orienting Filling:

[0015] Unidirectional tape is used as the twisting material, and it is continuously filled along the edge direction of the right-angle forming area. During the filling process, the filling amount is precisely controlled by the unidirectional tape twisting width calculation formula d=a*s / h.

[0016] Where d is the width of the unidirectional belt twisted yarn, a is an empirical coefficient and a=0.7~0.9, s is the cross-sectional area of ​​the twisted yarn region, and h is the thickness of a single layer of the unidirectional belt to ensure the continuity of fibers in the right-angle region;

[0017] Step D, Outer Skin Constraint Installation:

[0018] After laying the outer skin sheet, each layer of material is scraped and pressed in both directions along the right-angle contour to ensure that the outer skin sheet is completely bonded to the bottom layer of material and the twisted wire filling layer. After the laying is completed, the whole vacuum pre-compression is performed to form a closed-loop constraint on the twisted wire.

[0019] Step E: Mold closing and hot pressing pre-forming:

[0020] Remove pre-compression materials such as isolation membrane, breathable felt, and vacuum bag. Precisely align and combine the rigid cover plate with the male mold. Use an oven or autoclave for gradient hot compaction. After hot compaction, allow it to cool naturally to room temperature. Separate the mold to check the surface flatness and right-angle contour accuracy of the parts and remove surface defects.

[0021] Step F: Segmented curing and molding:

[0022] After re-molding, the parts are heated and cured in sections using an oven or autoclave. After cooling and demolding, the finished right-angle parts are obtained. The section curing and hot pressing pre-forming work together to avoid internal stress in the right-angle area.

[0023] As an improvement to the above technical solution, in step B, for flat-plate components, pre-compaction is performed every 3 to 5 layers.

[0024] For curved parts with a curvature radius ≤50mm, pre-compaction is performed every 2~3 layers. The pre-compaction vacuum degree is -85~-90Kpa, and the pre-compaction time is 12~15min to ensure that there is no air residue between layers.

[0025] As an improvement to the above technical solution, in step B, the scraping surface of the special scraping tool is an arc-shaped structure with an arc radius of 3~5mm and a scraping pressure of 0.1~0.3MPa, so as to avoid damaging the fiber of the material sheet during the scraping process.

[0026] As an improvement to the above technical solution, in step C, the unidirectional belt is a carbon fiber unidirectional belt or a glass fiber unidirectional belt, the fiber volume fraction of the unidirectional belt is 55%~65%, the fit between the twisted yarn and the right angle surface of the male mold after filling is ≥99%, and the gap between the twisted yarns is ≤0.05mm.

[0027] As an improvement to the above technical solution, in step C, the twisting and filling process adopts a segmented compaction method, with local scraping and compaction performed every 5-8mm of filling length, and the cumulative filling length deviation ≤ ±0.3mm, further ensuring the uniformity of filling in the right-angle area.

[0028] As an improvement to the above technical solution, in step D, the vacuum degree of the vacuum pre-compression is -88~-95Kpa, the pre-compression time is 15~20min, and the bonding gap between the outer skin sheet and the twisted wire filling layer after pre-compression is ≤0.1mm, thereby enhancing the constraint effect.

[0029] As an improvement to the above technical solution, in step E, the heating rate of the gradient hot compaction is 2~5℃ / min, the hot compaction temperature is 60~90℃, the holding time is 20~45min, and the pressure is 0.3~0.6MPa. The pressure increases linearly with the temperature to avoid thermal stress damage.

[0030] As an improvement to the above technical solution, in step F, the segmented curing includes a heating section, a heat preservation section, and a cooling section. The heating section has a heating rate of 3~6℃ / min, a curing temperature of 120~185℃, and a heat preservation time of 1.5~3h. The cooling section adopts a stepped cooling method with a cooling rate of 2~4℃ / min until room temperature is reached, thereby eliminating the internal stress generated during the curing process.

[0031] As an improvement to the above technical solution, in step E, the right-angled area of ​​the hard cover plate is provided with a wear-resistant coating with a thickness of 0.1~0.2mm. The coating material is polytetrafluoroethylene or ceramic, so as to avoid wear on the surface of the parts during the mold closing process.

[0032] As an improvement to the above technical solution, in step F, after cooling and demolding, the right angle deviation of the part is ≤ ±0.5°, and the radius of the rounded corner of the right angle edge is ≤ 0.3mm, which meets the right angle structure requirements of special composite materials.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] The above steps construct an integrated molding system of "precise material cutting - stepped pre-compression - directional filling - closed-loop constraint - gradient hot pressing - segmented curing", breaking through the limitations of isolated operation of each step in traditional processes. By controlling the dimensional accuracy of ≤±0.5mm in the fabric cutting stage, and the directional scraping and stepped vacuum pre-compression in the material laying stage, the tightness of interlayer bonding is guaranteed from the source, significantly reducing the interlayer porosity and avoiding the wrinkle accumulation problem that is easy to occur in multi-layer laying. This lays a high-precision foundation for subsequent right-angle molding. Its process system and controllability are significantly better than the existing extensive molding methods.

[0035] Addressing the core pain points of existing prepreg laying methods, such as the formation of rounded corners, fiber breakage in right-angle areas, insufficient adhesive, and uneven filling, this invention innovatively employs unidirectional directional twisting filling technology. Combined with the precise quantitative formula d=a*s / h and segmented compaction, it achieves continuous, unbroken fiber filling in right-angle areas. After filling, the fit between the twisted fibers and the right-angle surface of the male mold is ≥99%, with a gap ≤0.05mm. This completely solves the problem that traditional processes cannot simultaneously achieve both the regularity of the right-angle contour and the continuity of the fibers. Simultaneously, the closed-loop constraint formed by the bidirectional scraping and vacuum pre-compression of the outer skin effectively limits the displacement and deformation of the twisted fiber filling layer, ensuring that the radius of the right-angle edge rounding is ≤0.3mm and the angle deviation is ≤±0.5°, meeting the stringent precision requirements for right-angle structures in specialized fields.

[0036] Through the synergistic design of gradient hot compaction and segmented curing, precise control and elimination of internal stress are achieved. The linear increase in pressure with temperature during gradient hot compaction avoids damage to the parts caused by thermal stress. The segmented curing process—heating-holding-step cooling—combined with the synergistic effect of hot compaction preforming, fully releases the internal stress generated throughout the process, eliminating cracking and deformation problems caused by stress concentration in right-angle areas. Simultaneously, the wear-resistant coating design in the right-angle areas of the rigid cover plate prevents surface wear during mold closing, further ensuring the surface quality and structural integrity of the parts, significantly improving the mechanical properties, dimensional stability, and service life of the molded parts.

[0037] By quantitatively defining key parameters for each step, such as pre-compression vacuum, hot-pressing temperature and pressure, and curing time, the consistency of finished products is ensured, significantly improving the production qualification rate. It does not rely on special high-end equipment and can be molded using an oven or autoclave, lowering the production threshold. It can meet the high strength and high precision requirements of composite material right-angle parts in high-end fields such as aerospace, automotive, shipbuilding, and new energy. Compared with existing processes, it has significant practicality and industrialization value. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of the present invention.

[0039] In the diagram: 1. Male mold; 2. Sheet material; 3. Twisted wire; 4. Outer skin sheet; 5. Rigid cover plate. Detailed Implementation

[0040] 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.

[0041] Example:

[0042] like Figure 1 As shown in the figure, this embodiment proposes a process for forming right-angle male molds for composite material parts, including the following steps:

[0043] Step A: Cutting the fabric:

[0044] According to the layup diagram, use a CNC fabric cutting machine or a high-precision hand cutting method to cut the material, ensuring that the edge contour accuracy error of material piece 2 is ≤ ±0.5mm;

[0045] Step B, Sheet Laying:

[0046] Precise placement of sheet 2 is achieved by positioning with a projector or by tooling engraving. Sheet 2 is placed sequentially in the right-angle forming area of ​​the male mold 1. After each layer of sheet 2 is placed, a special scraping tool is used to scrape and press out air in one direction along the fiber direction. After the first layer is placed, a vacuum pre-compression is performed. Subsequent vacuum pre-compression is performed every 2-3 layers to form a stepped pre-compression structure.

[0047] Step C, Twisting and Orienting Filling:

[0048] Unidirectional belt is used as the raw material for twisted yarn 3, and it is continuously filled along the edge direction of the right-angle forming area. During the filling process, the filling amount is precisely controlled by the formula d=a*s / h for calculating the width of the unidirectional belt twisted yarn 3.

[0049] Where d is the width of the unidirectional belt twisted yarn 3, a is an empirical coefficient and a=0.7~0.9, s is the cross-sectional area of ​​the twisted yarn 3 region, and h is the thickness of a single layer of the unidirectional belt to ensure fiber continuity in the right-angle region;

[0050] Step D, Outer Skin Constraint Installation:

[0051] The outer skin sheet 4 is laid. After each layer of sheet 2 is laid, it is scraped and pressed in both directions along the right-angle contour so that the outer skin sheet 4 is completely attached to the bottom sheet 2 and the twisted wire 3 filling layer. After the laying is completed, the whole vacuum pre-compression is carried out to form a closed loop constraint on the twisted wire 3.

[0052] Step E: Mold closing and hot pressing pre-forming:

[0053] Remove the pre-compression isolation membrane, breathable felt, vacuum bag and other auxiliary materials, accurately align and combine the rigid cover plate 5 with the male mold 1, use an oven or autoclave for gradient hot compaction, and allow it to cool naturally to room temperature after hot compaction. Separate the mold to check the surface flatness and right angle contour accuracy of the parts, and remove surface defects.

[0054] Step F: Segmented curing and molding:

[0055] After re-molding, the parts are heated and cured in sections using an oven or autoclave. After cooling and demolding, the finished right-angle parts are obtained. The section curing and hot pressing pre-forming work together to avoid internal stress in the right-angle area.

[0056] In this embodiment, an integrated molding system of "precise material cutting - stepped pre-compression - directional filling - closed-loop constraint - gradient hot pressing - segmented curing" is constructed through the above steps, breaking through the limitations of isolated operation of each step in the traditional process. By controlling the dimensional accuracy of ≤±0.5mm in the fabric cutting stage, and the directional scraping and stepped vacuum pre-compression in the material sheet 2 laying stage, the tightness of interlayer bonding is guaranteed from the source, significantly reducing the interlayer porosity and avoiding the wrinkle accumulation problem that is easy to occur in multi-layer laying. This lays a high-precision foundation for subsequent right-angle molding. Its process system and controllability are significantly better than the existing extensive molding methods.

[0057] Addressing the core pain points of existing prepreg laying, such as the formation of rounded corners, fiber breakage in right-angle areas, insufficient adhesive, and uneven filling, this invention innovatively adopts a unidirectional directional twisted yarn filling technology. Combined with a precise quantitative formula of d=a*s / ha=0.7~0.9 and segmented compaction operation, it achieves continuous and unbroken fiber filling in right-angle areas. After filling, the fit between the twisted yarn 3 and the right-angle surface of the male mold 1 is ≥99%, and the gap is ≤0.05mm, completely solving the problem that traditional processes cannot simultaneously achieve the regularity of right-angle contours and fiber continuity. At the same time, the closed-loop constraint formed by the bidirectional scraping and vacuum pre-compression of the outer skin effectively limits the displacement and deformation of the twisted yarn 3 filling layer, ensuring that the radius of the right-angle edge rounding is ≤0.3mm and the angle deviation is ≤±0.5°, meeting the stringent precision requirements of right-angle structures in special fields.

[0058] Through the synergistic design of gradient hot compaction and segmented curing, precise control and elimination of internal stress are achieved. The linear increase in pressure with temperature during gradient hot compaction avoids damage to the parts caused by thermal stress. The segmented curing process—heating-holding-step cooling—combined with the synergistic effect of hot compaction preforming, fully releases the internal stress generated throughout the process, eliminating cracking and deformation problems caused by stress concentration in right-angle areas. Simultaneously, the wear-resistant coating design in the five right-angle areas of the rigid cover plate prevents surface wear during mold closing, further ensuring the surface quality and structural integrity of the parts, significantly improving the mechanical properties, dimensional stability, and service life of the molded parts.

[0059] By quantitatively defining key parameters for each step, such as pre-compression vacuum, hot-pressing temperature and pressure, and curing time, the consistency of finished products is ensured, significantly improving the production qualification rate. It does not rely on special high-end equipment and can be molded using an oven or autoclave, lowering the production threshold. It can meet the high strength and high precision requirements of composite material right-angle parts in high-end fields such as aerospace, automotive, shipbuilding, and new energy. Compared with existing processes, it has significant practicality and industrialization value.

[0060] Specifically, in step B, for flat-panel components, pre-compaction is performed every 3 to 5 layers;

[0061] For curved parts with a curvature radius ≤50mm, pre-compaction is performed every 2~3 layers. The pre-compaction vacuum degree is -85~-90Kpa, and the pre-compaction time is 12~15min to ensure that there is no air residue between layers.

[0062] In this embodiment, a differentiated pre-compaction strategy is adopted for composite material parts with different structural types. For flat-like parts with a flat structure and easy air expulsion between layers, pre-compaction is set to be performed every 3 to 5 layers. For curved parts with a curvature radius ≤ 50 mm, complex structure and difficult air expulsion between layers, pre-compaction is set to be performed every 2 to 3 layers. This achieves precise matching between the pre-compaction process and the structural characteristics of the parts, and solves the dual pain points of "over-pre-compaction of flat-like parts resulting in wasted efficiency" and "insufficient pre-compaction of curved parts resulting in residual air" caused by the uniform pre-compaction interval in the traditional process. This significantly improves the targeting and adaptability of the process.

[0063] By limiting the pre-compaction vacuum degree to -85~-90Kpa and the pre-compression time to 12~15min, sufficient negative pressure strength is ensured to efficiently extract air and excess resin between the two layers of the sheet, while avoiding problems such as fiber damage and resin loss in the two layers of the sheet caused by excessive vacuum or excessive pre-compression time. This ensures that there is no air residue between the layers, significantly reduces the interlayer porosity, and strengthens the bonding tightness and stability between the two layers of the sheet, providing a key guarantee for the subsequent molding quality of the right-angle area and the overall mechanical properties of the part.

[0064] Specifically, in step B, the scraping surface of the special scraping tool has an arc-shaped structure with an arc radius of 3~5mm and a scraping pressure of 0.1~0.3MPa to avoid damaging the fibers of the material sheet 2 during the scraping process.

[0065] In this embodiment, by designing the scraping surface of the special scraping tool as an arc-shaped structure and limiting the arc radius to 3~5mm, the contact area between the scraping surface and the fiber of the material sheet 2 is significantly increased, avoiding the problem of local pressure concentration caused by traditional flat or sharp scraping structures. It provides buffer protection for the fiber of the material sheet 2 from a structural level, effectively reducing the risk of fiber being crushed or damaged during the scraping process, and ensuring the integrity and continuity of the fiber.

[0066] Specifically, in step C, the unidirectional belt is a carbon fiber unidirectional belt or a glass fiber unidirectional belt, the fiber volume fraction of the unidirectional belt is 55%~65%, the fit between the twisted yarn 3 and the right angle surface of the male mold 1 after filling is ≥99%, and the gap between the twisted yarns 3 is ≤0.05mm.

[0067] In this embodiment, the unidirectional tape is precisely defined as either carbon fiber unidirectional tape or glass fiber unidirectional tape. These two types of materials have high strength, high modulus and excellent fiber continuity, which are precisely matched with the core requirements of right-angle parts for structural load-bearing capacity. From the raw material level, this provides a key guarantee for the structural strength of the right-angle area and solves the technical pain point of easy deformation and breakage in the right-angle area caused by insufficient strength of traditional filling materials.

[0068] By strictly limiting the fiber volume fraction of the unidirectional tape to 55%~65%, an optimal balance system of "fiber reinforcement-resin impregnation" was constructed. This volume fraction range can fully utilize the load-bearing and force-transferring role of the fiber, ensuring that the mechanical properties of the right-angle region meet the standards. It can also avoid the problems of insufficient resin impregnation and resin deficiency caused by excessive fiber volume fraction, or the weakening of fiber reinforcement effect caused by excessively low fiber volume fraction. This significantly improves the structural uniformity and reliability of the twisted yarn filling layer 3.

[0069] Specifically, in step C, the twisting and filling process adopts a segmented compaction method. Every 5-8mm of filling is locally scraped and compacted, and the cumulative filling length deviation is ≤±0.3mm, which further ensures the uniformity of filling in the right-angle area.

[0070] In this embodiment, addressing the technical pain points of the traditional twisted yarn filling process, which uses an overall compaction method that easily leads to loose filling and fiber accumulation in right-angle areas and makes it difficult to control dimensional deviations after long-distance filling, an innovative segmented compaction scheme is designed. This scheme limits local scraping and compaction to every 5-8mm of filling length, which can eliminate local voids and fiber misalignment and accumulation problems generated during the filling process in real time. This ensures that each segment of the filling layer in the right-angle area reaches a dense state, fundamentally solving the core defect of the traditional overall compaction process that cannot take into account the uniformity of local filling, and achieving precise control of filling quality.

[0071] By further limiting the cumulative filling length deviation to ≤±0.3mm, a collaborative technical system of "segmented compaction + precise closed-loop control of dimensions" is formed. This not only ensures the compactness of local filling but also achieves high-precision control of the overall filling length. It effectively avoids problems such as deformation of right-angle contours and excessive gaps between the filling material 2 or the outer skin due to filling size deviations. It significantly improves the compatibility of the twisted wire 3 filling layer with the surrounding structure, laying a solid foundation for the smooth implementation of subsequent processes such as outer skin constraint laying and mold hot compaction, ensuring the contour regularity and structural integrity of right-angle parts.

[0072] The combined design of segmented compaction and length deviation control ensures a uniform density distribution of the twisted yarn filling layer in the right-angle region, effectively avoiding structural weaknesses caused by uneven local filling and significantly improving the interlayer bonding strength and overall mechanical load-bearing capacity in the right-angle region. Simultaneously, this design eliminates the need for additional complex equipment, exhibits strong compatibility with existing molding processes, and balances process feasibility and production efficiency while ensuring filling quality. Compared to traditional filling processes lacking precise control, it significantly improves the consistency and reliability of the finished product, highlighting the creativity and practicality of the process design and better meeting the stringent quality requirements of high-end composite right-angle parts.

[0073] Specifically, in step D, the vacuum degree of the vacuum pre-compression is -88~-95Kpa, the pre-compression time is 15~20min, and the bonding gap between the outer skin sheet 4 and the twisted wire 3 filling layer after pre-compression is ≤0.1mm, which strengthens the constraint effect.

[0074] Specifically, in step E, the heating rate of the gradient hot compaction is 2~5℃ / min, the hot compaction temperature is 60~90℃, the holding time is 20~45min, and the pressure is 0.3~0.6MPa. The pressure increases linearly with the temperature to avoid thermal stress damage.

[0075] In this embodiment, by precisely limiting the heating rate of gradient hot compaction to 2~5℃ / min, the slow and uniform heating of each structural layer of the part is achieved, avoiding the temperature difference stress caused by the inconsistent thermal expansion and contraction rates of each layer in the traditional rapid heating process. This reduces the accumulation of thermal stress from the source and effectively avoids core defects such as fiber breakage, interlayer peeling or right-angle contour deformation caused by thermal stress, ensuring the integrity of the part structure and the initial molding accuracy.

[0076] By specifying the hot compaction temperature as 60~90℃ and the holding time as 20~45min, this parameter combination creates a suitable thermal environment for the resin: the temperature range of 60~90℃ allows the composite resin to be in a moderately fluid state, which facilitates the expulsion of residual air and excess resin between layers without causing the resin to cure prematurely and lose its fluidity; the holding time of 20~45min ensures that heat penetrates evenly to the corners of the right-angle area, achieving full adhesion and compaction of each structural layer. This completely solves the problems of insufficient local compaction and residual voids between layers caused by uneven heating in traditional hot compaction, laying a solid foundation for improving the interlayer bonding strength.

[0077] An innovative dynamic and coordinated control mechanism with "pressure increasing linearly with temperature" is designed, combined with a pressure range of 0.3~0.6MPa, to form a precise "temperature-pressure" adaptation system: at low temperatures, the resin viscosity is higher, and the corresponding lower pressure can avoid fiber damage or structural misalignment caused by forced compaction; as the temperature rises, the resin viscosity decreases, and the pressure increases synchronously, which can make full use of the resin fluidity to achieve tight compaction between layers. This completely solves the technical contradiction in the traditional constant pressure hot compaction process of "insufficient compaction at low temperatures and excessive pressure at high temperatures damaging the structure". While maximizing the compaction effect, it also achieves precise protection of the part structure.

[0078] Specifically, in step F, the segmented curing includes a heating section, a heat preservation section, and a cooling section. The heating section has a heating rate of 3~6℃ / min, a curing temperature of 120~185℃, and a heat preservation time of 1.5~3h. The cooling section adopts a stepped cooling method with a cooling rate of 2~4℃ / min until room temperature is reached, thereby eliminating the internal stress generated during the curing process.

[0079] In this embodiment, addressing the technical pain points of traditional curing processes, such as the lack of segmented control and the lack of precise matching of heating / cooling rates, which leads to inconsistent thermal responses and internal stress accumulation in the structural layers of composite materials, and the tendency for incomplete curing or stress concentration cracking, an innovative three-stage segmented curing system of "heating stage - heat preservation stage - cooling stage" is designed. Through precise quantification and coordinated control of key parameters at each stage, the technical contradiction of the traditional single curing process being unable to simultaneously achieve "sufficient curing" and "internal stress control" is overcome, and a systematic improvement in molding quality is achieved.

[0080] The precise heating rate of 3~6℃ / min in the heating section ensures that multiple structural layers, including the two-layer sheet, the three-layer twisted yarn filling layer, and the outer skin layer, are heated synchronously and uniformly. This avoids internal stress caused by temperature differences due to the different rates of thermal expansion and contraction of different structures, effectively protecting the fiber continuity and interlayer bonding structure. It also prevents defects such as interlayer delamination and fiber breakage caused by local stress concentration during the heating process, laying a solid structural foundation for subsequent full curing and ensuring the consistency of the stress distribution among all structural layers.

[0081] Specifically, in step E, the right-angled area of ​​the rigid cover plate 5 is provided with a wear-resistant coating with a thickness of 0.1~0.2mm. The coating material is polytetrafluoroethylene or ceramic to avoid wear on the surface of the parts during the mold closing process.

[0082] Specifically, in step F, after cooling and demolding, the right-angle deviation of the part is ≤ ±0.5°, and the radius of the rounded corner of the right-angle edge is ≤ 0.3mm, which meets the right-angle structure requirements of special composite materials.

[0083] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for forming right-angle male molds for composite material parts, characterized in that: Includes the following steps: Step A: Cutting the fabric: According to the layup diagram, use a CNC fabric cutting machine or a high-precision hand cutting method to cut the material to ensure that the edge contour accuracy error of the material sheet (2) is ≤ ±0.5mm; Step B, Sheet Laying: The material sheet (2) is accurately laid by positioning with a projector or tooling engraving. The material sheet (2) is laid in sequence in the right-angle forming area of ​​the male mold (1). After each layer of material sheet (2) is laid, a special scraping tool is used to scrape and press the air out in one direction along the fiber direction. After the first layer is laid, a vacuum pre-press is performed. Subsequently, a vacuum pre-press is performed every 2-3 layers to form a stepped pre-press structure. Step C, Twisting and Orienting Filling: Unidirectional belt is used as the raw material for twisting (3), and it is continuously filled along the edge direction of the right-angle forming area. During the filling process, the filling amount is precisely controlled by the formula d=a*s / h for calculating the width of the unidirectional belt twisting (3). Where d is the width of the unidirectional twisted yarn (3), a is an empirical coefficient and a = 0.7~0.9, s is the cross-sectional area of ​​the twisted yarn (3) region, and h is the thickness of a single layer of the unidirectional belt to ensure the continuity of fibers in the right-angle region; Step D, Outer Skin Constraint Installation: The outer skin sheet (4) is laid. After each layer of sheet (2) is laid, it is scraped and pressed in both directions along the right angle contour so that the outer skin sheet (4) is completely attached to the bottom sheet (2) and the twisted wire (3) filling layer. After the laying is completed, the whole vacuum pre-press is carried out to form a closed loop constraint on the twisted wire (3). Step E: Mold closing and hot pressing pre-forming: Remove the pre-compression isolation film, breathable felt, vacuum bag and other auxiliary materials, and accurately align and combine the hard cover plate (5) with the male mold (1). Use an oven or autoclave for gradient hot compaction. After hot compaction, let it cool naturally to room temperature. Separate the mold to check the flatness of the part surface and the accuracy of the right angle contour, and remove surface defects. Step F: Segmented curing and molding: After re-molding, the parts are heated and cured in sections using an oven or autoclave. After cooling and demolding, the finished right-angle parts are obtained. The section curing and hot pressing pre-forming work together to avoid internal stress in the right-angle area.

2. The method for forming a right-angle male mold for composite material parts according to claim 1, characterized in that: In step B, for flat-panel components, pre-compaction is performed every 3 to 5 layers; For curved parts with a curvature radius ≤50mm, pre-compaction is performed every 2~3 layers. The pre-compaction vacuum degree is -85~-90Kpa, and the pre-compaction time is 12~15min to ensure that there is no air residue between layers.

3. The method for forming a right-angle male mold for composite material parts according to claim 1, characterized in that: In step B, the scraping surface of the special scraping tool is an arc-shaped structure with an arc radius of 3~5mm and a scraping pressure of 0.1~0.3MPa to avoid damaging the fiber of the material sheet (2) during the scraping process.

4. The method for forming a right-angle male mold for composite material parts according to claim 1, characterized in that: In step C, the unidirectional belt is a carbon fiber unidirectional belt or a glass fiber unidirectional belt. The fiber volume fraction of the unidirectional belt is 55%~65%. After filling, the fit between the twisted yarn (3) and the right angle surface of the male mold (1) is ≥99%, and the gap between the twisted yarn (3) is ≤0.05mm.

5. The method for forming a right-angle male mold for composite material parts according to claim 1, characterized in that: In step C, the twisted wire (3) filling process adopts a segmented compaction method. Every 5~8mm of filling length is locally scraped and compacted, and the cumulative filling length deviation is ≤±0.3mm, which further ensures the uniformity of filling in the right angle area.

6. The method for forming a right-angle male mold for composite material parts according to claim 1, characterized in that: In step D, the vacuum degree of the vacuum pre-compression is -88~-95Kpa, the pre-compression time is 15~20min, and the bonding gap between the outer skin sheet (4) and the twisted wire (3) filling layer after pre-compression is ≤0.1mm, which strengthens the constraint effect.

7. The method for forming a right-angle male mold for composite material parts according to claim 1, characterized in that: In step E, the heating rate of the gradient hot compaction is 2~5℃ / min, the hot compaction temperature is 60~90℃, the holding time is 20~45min, and the pressure is 0.3~0.6MPa. The pressure increases linearly with the temperature to avoid thermal stress damage.

8. The method for forming a right-angle male mold for composite material parts according to claim 1, characterized in that: In step F, the segmented curing includes a heating section, a heat preservation section, and a cooling section. The heating section has a heating rate of 3~6℃ / min, a curing temperature of 120~185℃, and a heat preservation time of 1.5~3h. The cooling section adopts a stepped cooling method with a cooling rate of 2~4℃ / min until room temperature is reached, thereby eliminating the internal stress generated during the curing process.

9. The method for forming a right-angle male mold for composite material parts according to claim 1, characterized in that: In step E, the right-angled area of ​​the hard cover plate (5) is provided with a wear-resistant coating with a thickness of 0.1~0.2mm. The coating material is polytetrafluoroethylene or ceramic to avoid wear on the surface of the parts during the mold closing process.

10. The method for forming a right-angle male mold for composite material parts according to claim 1, characterized in that: In step F, after cooling and demolding, the right-angle deviation of the part is ≤ ±0.5°, and the radius of the rounded corner of the right-angle edge is ≤ 0.3mm, which meets the right-angle structure requirements of special composite materials.

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