Preparation method of combined fiber disc spring

Abstract

The invention discloses a preparation method of a combined fiber disc spring, which comprises the following steps: preparing single disc springs on the basis of a prepreg forming method, and combining a plurality of single disc springs to obtain a combined disc spring; wherein when the green body is prepared, the glass fiber prepreg is firstly laminated and paved according to a set fiber direction, and then the glass fiber prepreg is cut into the green body in the shape of a single disc spring. According to the invention, the process of'first overall laying and then uniform cutting 'is adopted, and through innovative adjustment of the process sequence, the problems of difficult film tearing, easy dislocation of laying layers, easy damage of edges and the like existing in the process of processing small-size prepreg sheets by the traditional process of'first cutting of single sheets and then piece-by-piece laying' are effectively solved. According to the improvement, the continuity and accuracy of fiber laying are guaranteed from the source, then the uniformity and consistency of the internal quality, the size precision and the mechanical property of the component are remarkably improved, and the strict requirements of the small disc spring for high bearing reliability and long fatigue life are met.

Description

Technical Field

[0001] This invention belongs to the field of disc spring design and manufacturing technology, specifically relating to a small composite disc spring made of fiber-reinforced resin matrix composite material, and particularly to the structural parameter design, layup process and molding method of such disc spring. Background Technology

[0002] Disc springs (or disc springs for short) are conical discs that can be used as single or multiple discs and are widely used in aerospace, precision machinery, vehicle engineering and industrial equipment.

[0003] Currently, commercial disc springs mainly use metal materials such as spring steel. Although the technology of these metal disc springs is mature, their material properties also bring the following inherent limitations: First, the overall stiffness of metal disc springs is relatively high, making it difficult to achieve ideal stiffness matching in applications requiring high precision; second, the high material density makes the disc springs heavy, which is not conducive to achieving lightweight design in modern equipment; in addition, metal materials are prone to fatigue failure under long-term alternating loads, and their durability and reliability will be significantly reduced in humid and corrosive environments.

[0004] Fiber-reinforced resin matrix composites, with their high specific strength, designable specific modulus, and excellent fatigue and corrosion resistance, offer a new approach to overcoming the aforementioned limitations and developing a new generation of high-performance disc springs. However, applying fiber-reinforced resin matrix composites to intricately designed small disc springs still faces the following technical challenges: Firstly, in terms of precision molding, small disc springs are characterized by thin walls, curved surfaces, and precise dimensions. If the traditional prepreg molding method, as represented by patent CN108506393B, is used, the small size of the prepreg sheet and its "first cut a single sheet and then lay it up" process not only presents difficulties in tearing the film, but also leads to operational difficulties, easy layup misalignment, edge damage, and interface contamination. This results in uneven internal quality, poor dimensional accuracy, and large dispersion in mechanical properties of the molded part, making it difficult to meet the stringent requirements of disc springs for load-bearing consistency and fatigue life.

[0005] Secondly, in terms of performance design, the mechanical properties of fiber-reinforced resin matrix composites are highly dependent on fiber orientation, fiber volume fraction, and resin properties. Disc springs, under load, are in a complex stress state, and their performance is extremely sensitive to structural parameters. Currently, there is a lack of mature and reliable design guidelines and methods for synergistically optimizing material parameters (fiber orientation, fiber volume fraction, etc.) and structural parameters (cone height, thickness, etc.) to balance key indicators such as load-bearing capacity, deformation, reset accuracy, and stability, taking into account the specific truncated conical structure and boundary conditions of disc springs used in combination. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing composite fiber disc springs. By optimizing the layup and cutting processes (layup first, then cutting) and coordinating the design of its structural parameters and material layup scheme, the method can solve the problems of poor molding quality and difficult performance control of small fiber disc springs in the prior art, thereby obtaining high-precision, high-performance lightweight disc spring products.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing a composite fiber disc spring, wherein a single disc spring is prepared based on a prepreg molding method, and then multiple single disc springs are combined to obtain a composite disc spring; in the preparation of the green blank, glass fiber prepreg is laminated and laid in a set fiber direction, and then cut into a green blank in the shape of a single disc spring.

[0008] As a limitation of this invention, the maximum deformation of the single-piece disc spring is no greater than 0.75h0, and The ratio is no greater than 0.6; Where h0 is the height of the inner cone and t is the thickness.

[0009] As a further limitation of the present invention, the outer cone height H0 of the single disc spring is 3mm, the inner cone height h0 is 1.17mm, the outer diameter D is 41.5mm, the inner diameter d is 30mm, and the thickness t is 2mm.

[0010] As a further limitation of the present invention, the single disc spring has an upper inner edge support surface and a lower outer edge support surface, both with a width w of 0.5 mm.

[0011] As another limitation of the present invention, the method specifically includes the following steps: S1, Laying: Laying multiple layers of glass fiber prepreg according to a set fiber direction to form a preform blank; S2, Cutting: Cutting the preform blank into a green blank corresponding to the shape of a single disc spring; S3, Shaping: After hot pressing and curing the green blank, grinding it into the shape of the single disc spring; S4, Combining: Combining multiple single disc springs to obtain a combined disc spring.

[0012] As a further limitation of the present invention, the volume fraction of fiber in the glass fiber prepreg is 40% to 42%, and the resin matrix is ​​epoxy resin.

[0013] As a further limitation of the present invention, in step S1, the single-layer thickness of the glass fiber prepreg is 0.14 to 0.18 mm, and the number of layers is 12.

[0014] As a further limitation of the present invention, in step S1, the fiber direction is 0° / 90° or ±45°.

[0015] As a further limitation of the present invention, in step S1, the glass fiber prepreg is a square of 50mm*50mm.

[0016] As another limitation of the present invention, the hot-press curing process parameters in step S3 include: Molding pressure: lower limit is 3 MPa, upper limit is 3.5 MPa; Curing temperature and time: Increase the temperature from room temperature to 80°C within 30 minutes and hold for 30 minutes; then increase the temperature from 80°C to 150°C within 30 minutes and hold for 30 minutes; finally, maintain pressure and allow to cool naturally to room temperature.

[0017] By adopting the above-described technical solution, the beneficial effects achieved by this invention compared to the prior art are as follows: (1) The “first lay up the whole, then cut uniformly” process adopted in this invention effectively solves the problems of difficult film tearing, easy misalignment of the layup, and easy damage to the edges in the traditional “first cut the single piece, then lay up piece by piece” process when processing small-sized prepreg sheets through innovative adjustment of the process sequence. This improvement ensures the continuity and accuracy of fiber layup from the root, thereby significantly improving the internal quality, dimensional accuracy and uniformity and consistency of mechanical properties of the component, and meeting the strict requirements of high load-bearing reliability and long fatigue life of small disc springs.

[0018] (2) This invention provides clear design boundaries for the application of fiber composite materials in components such as disc springs by setting two core design principles: the maximum deformation should not exceed 0.75h0 and the h0 / t ratio should not exceed 0.6. The former effectively prevents the risk of material stress exceeding limits and failure due to excessive deformation; the latter fundamentally avoids the risk of negative stiffness or structural instability of the disc spring during compression. The two work together to ensure that the disc spring obtains the required deformation while also possessing excellent recovery ability, structural stability and load-bearing safety.

[0019] (3) The product structural parameters defined in this invention (including but not limited to inner cone height h0=1.17mm, inner diameter d=30mm and thickness t=2mm) are a set of specific values ​​that have been systematically designed and have clear functional orientation and synergistic effect. Among them, the ratio of inner cone height h0 to thickness t is precisely set to 0.585. This specific value ensures that the disc spring maintains positive stiffness throughout the compression process and avoids the risk of instability, while providing the optimal geometric basis for achieving a stiffness much lower than that of metal disc springs (such as achieving the best stiffness matching of 108.6N / mm).

[0020] (4) The present invention introduces an upper inner edge support surface and a lower outer edge support surface on a single disc spring. This design transforms potential line / point contact into a controllable uniform annular bearing surface, significantly reducing stress concentration at the contact edge, effectively mitigating the risk of interlaminar delamination of fiber composite materials, and directly improving fatigue resistance. At the same time, this design provides a stable load transfer interface for multi-piece combinations, preventing off-center loading and slippage during combined use, and ensuring the overall performance stability of the combined disc spring.

[0021] (5) The product structure parameters defined by the present invention, together with the selected material parameters (such as 0° / 90° layup direction, 40% to 42% fiber volume fraction), work together to achieve the core advantages of lightweight and low stiffness in the final product, as well as excellent load-bearing reliability, fatigue life and performance consistency.

[0022] In summary, this invention successfully fabricates a high-performance composite fiber disc spring through systematic process and design innovation. It fully leverages the advantages of fiber composite materials, such as lightweight, fatigue resistance, and corrosion resistance, achieving significant weight reduction while providing superior stiffness matching and damping characteristics. It is particularly suitable for high-end equipment fields such as aerospace and precision instruments, where stringent requirements for weight, precision, reliability, and environmental adaptability exist, demonstrating outstanding technical competitiveness and application prospects. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] Figure 1 This is a perspective view of the structural relationship of the combined fiber disc spring in Embodiment 1 of the present invention; Figure 2 This is a front view of the structural relationship of the combined fiber disc spring in Embodiment 1 of the present invention; Figure 3 This is a perspective view of the structural relationship of the single disc spring in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the longitudinal section of the single disc spring in Embodiment 1 of the present invention; Figure 5 This is a load-displacement curve of the combined fiber disc spring in Embodiment 3 of the present invention; In the diagram: 1. Single disc spring. Detailed Implementation

[0025] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustrative and understanding purposes only and are not intended to limit the scope of the invention.

[0026] Example 1: A method for preparing a composite fiber disc spring In this embodiment, the composite fiber disc spring uses glass fiber / epoxy resin unidirectional prepreg as the raw material. The volume fraction of glass fiber in the prepreg is controlled between 40% and 42%, and the thickness of a single layer of prepreg is 0.14 mm to 0.18 mm. In one specific embodiment, a prepreg with a fiber volume fraction of 41% and a single layer thickness of 0.16 mm is preferably selected.

[0027] like Figure 3 and Figure 4 As shown, the geometric dimensions of the single-piece disc spring 1 are as follows: The height of the outer cone, H0, is 3.0 mm. The inner cone height h0 = 1.17 mm; Outer diameter D = 41.5 mm; Inner diameter d=30.0mm; Thickness t = 2.0 mm; The width of the upper inner edge and lower outer edge support surface is w=0.5mm.

[0028] Based on the above dimensions, the monolithic disc spring 1 has the following specially designed key features: Firstly, =0.585 (satisfied) The ratio is no greater than 0.6, which ensures that the single disc spring 1 maintains positive stiffness during compression and avoids instability; Secondly, the maximum deformation is no more than 0.75h0. This limit can effectively prevent the risk of material stress exceeding the limit and failure due to excessive deformation.

[0029] In this embodiment, the preparation process specifically includes four stages: lay-up, cutting, molding and curing, and assembly.

[0030] S1. Layering and pasting to form a preform blank. First, the glass fiber prepreg is cut into square sheets with sides of 50mm. After removing the release film, it is laid in alternating 0° and 90° directions, for a total of 12 layers. During laying, ensure that the edges of each layer are aligned, and use rollers to remove air bubbles between layers, ultimately forming a multi-layered, integrated square preform. The key to this process is to first complete the lamination of all glass fiber prepreg according to the set fiber direction to form an integrated preform.

[0031] S2. Cutting to obtain the disc spring blank. The preformed blank is placed into a precision punching die and punched out in one step to produce a ring-shaped disc spring blank with an outer diameter of 41.5 mm and an inner diameter of 30.0 mm. This process achieves direct contour forming of the preformed blank.

[0032] S3. Molding, Curing, and Post-processing S3.1 Mold preparation: Use a molding mold that matches the geometry and support surface structure of the target single disc spring 1, and spray a release agent evenly on the cavity surface; S3.2, Molding and Curing: Place the green blank into the lower mold of the forming mold, close the upper mold, and move it into the hot press. The pressure of the hot press is hydraulically driven, with a lower limit set at 3 MPa and an upper limit set at 3.5 MPa; and cure according to the following temperature program: Phase 1: The temperature is uniformly raised from room temperature to 80°C within 30 minutes, and then kept at 80°C for 30 minutes. Second stage: The temperature is uniformly increased from 80℃ to 150℃ within 30 minutes, and then kept at 150℃ for 30 minutes; Third stage: Hold pressure, stop heating, and allow the mold to cool naturally to room temperature; S3.3 Demolding and Grinding: After the mold is opened, the solidified single disc spring 1 is removed. Special equipment is used to precisely grind its inner hole and outer circle to remove burrs and ensure dimensional accuracy and smooth support surface.

[0033] S4, Combination like Figure 1 and Figure 2 As shown, eight qualified single disc springs 1 are stacked in a mating manner with their convex surfaces facing each other, and assembled into a combined disc spring with a total free height of approximately 24 mm.

[0034] Example 2: A method for preparing a composite fiber disc spring The main difference between this embodiment and Embodiment 1 lies in the layup scheme, the single-layer thickness of the prepreg, and the fiber volume fraction. The remaining structural parameters and preparation process are the same, in order to demonstrate another optional embodiment of the present invention.

[0035] Specifically, in this embodiment, the thickness of a single prepreg layer is 0.15 mm. During layup, alternating between +45° and -45° directions, a total of 12 layers are laid. The volume fraction of glass fiber in the prepreg is 40.5%, and the resin matrix remains epoxy resin.

[0036] The composite fiber disc spring prepared in this embodiment has different stiffness characteristics from that in Example 1, but it also has excellent restoring ability, structural stability and load-bearing safety, proving the feasibility of the ±45° layup scheme in the system of the present invention.

[0037] Example 3 Compression Test of Combined Fiber Disc Spring The composite fiber disc spring serves as the reset component of the anti-rotation mechanism, and its purpose is to completely reset the structure after the impact. In order to obtain the load-displacement curve of the disc spring loading and unloading process, the composite fiber disc spring obtained in Example 1 was subjected to compression test using an ETM electronic universal testing machine.

[0038] Since the composite fiber disc spring is composed of 8 individual disc springs combined in pairs, direct compression testing of it is prone to lateral slippage, leading to distorted test results. Therefore, a guide mandrel is required. Considering the gap caused by the decrease in the inner diameter of the disc spring during compression, the distance between the outer diameter of the guide mandrel and the inner diameter of the disc spring is set to 0.2 mm, i.e., the outer diameter of the guide mandrel is 29.8 mm.

[0039] During the test, the upper pressure plate of the ETM electronic universal testing machine contacted the upper end face of the guide mandrel and was uniformly loaded at a loading speed of 2 mm / min. The loading displacement was set to 6 mm, and the unloading displacement was 6 mm. To ensure that the upper pressure plate of the testing machine was in complete contact with the guide mandrel and to prevent fatigue cracks in the disc spring, a pre-compression deformation of 0.1 mm was applied to the glass fiber disc spring before the compression test began. When the load reached 6 mm, it was held for 15 seconds, and then unloaded. This cycle was repeated four times, and the result of the last test was taken.

[0040] Three sets of disc springs were tested under the same conditions, and the results of the last test were used. The load-displacement data during the test were acquired and processed by the testing machine's data acquisition system.

[0041] The load-displacement curves of the three sets of combined fiber disc springs during loading and unloading are as follows: Figure 5 As shown in the figure, the load-displacement curves of the three disc springs exhibit basically the same trend: the stiffness gradually increases with the increase of displacement. Further analysis leads to the following conclusions: ① The loading-unloading curves of the disc spring do not completely overlap. The loading curve is significantly higher than the unloading curve, and a certain enclosing area is formed between the two. This is mainly because there is a certain friction between the guide rod spindle and the disc spring during the compression process. During loading, the presence of friction makes the loading curve higher, and during unloading, the friction hinders the disc spring from recovering, making the unloading curve lower. ② The disc spring fully recovers its deformation after being compressed by 6mm, which indicates that the disc spring has excellent restoring ability; ③ The average stiffness of the disc spring is about 190 N / mm, which is much smaller than the stiffness of the metal disc spring. The average load value is 1140 N at 6 mm.

[0042] The above embodiments specifically illustrate the implementation of the technical solution of the present invention. By adopting the core process of "first laying up the entire structure, then uniformly cutting," and combining specially designed structural parameters (including but not limited to h0=1.17mm, t=2mm, d=30mm, support surface w=0.5mm), selectable fiber layup direction (0° / 90° or ±45°), specific material parameter ranges (fiber volume fraction 40%~42%, single layer thickness 0.14~0.18mm), and optimized curing process, high-performance small composite fiber disc springs can be successfully prepared. While achieving significant weight reduction, the product also exhibits low stiffness, excellent recovery ability, high structural stability, and good fatigue resistance.

Claims

1. A method for preparing a composite fiber disc spring, comprising preparing a single disc spring based on a prepreg molding method, and then combining multiple single disc springs to obtain a composite disc spring; characterized in that, In the preparation of green bodies, glass fiber prepreg is laid in layers according to the set fiber direction and then cut into green bodies in the shape of single disc springs.

2. The method for preparing a composite fiber disc spring according to claim 1, characterized in that, The maximum deformation of the single disc spring is no greater than 0.75h0, and The ratio is no greater than 0.6; Where h0 is the height of the inner cone and t is the thickness.

3. The method for preparing a composite fiber disc spring according to claim 2, characterized in that, The single disc spring has an outer cone height H0 of 3 mm, an inner cone height h0 of 1.17 mm, an outer diameter D of 41.5 mm, an inner diameter d of 30 mm, and a thickness t of 2 mm.

4. The method for preparing a composite fiber disc spring according to claim 3, characterized in that, The single disc spring has an upper inner edge support surface and a lower outer edge support surface, both with a width w of 0.5 mm.

5. A method for preparing a composite fiber disc spring according to any one of claims 1-4, characterized in that, The method specifically includes the following steps: S1, Laying: Laying multiple layers of glass fiber prepreg according to a set fiber direction to form a preform blank; S2, Cutting: Cutting the preform blank into a green blank corresponding to the shape of a single disc spring; S3, Shaping: After hot pressing and curing the green blank, grinding it into the shape of the single disc spring; S4, Combining: Combining multiple single disc springs to obtain a combined disc spring.

6. The method for preparing a composite fiber disc spring according to claim 5, characterized in that, The glass fiber prepreg has a fiber volume fraction of 40% to 42% and the resin matrix is ​​epoxy resin.

7. The method for preparing a composite fiber disc spring according to claim 6, characterized in that, In step S1, the thickness of a single layer of glass fiber prepreg is 0.14 to 0.18 mm, and the number of layers is 12.

8. A method for preparing a composite fiber disc spring according to claim 6 or 7, characterized in that, In step S1, the fiber orientation is 0° / 90° or ±45°.

9. The method for preparing a composite fiber disc spring according to claim 8, characterized in that, In step S1, the glass fiber prepreg is a 50mm*50mm square.

10. A method for preparing a composite fiber disc spring according to any one of claims 6, 7, and 9, characterized in that, In step S3, the hot-press curing process parameters include: Molding pressure: lower limit is 3 MPa, upper limit is 3.5 MPa; Curing temperature and time: Increase the temperature from room temperature to 80°C within 30 minutes and hold for 30 minutes; then increase the temperature from 80°C to 150°C within 30 minutes and hold for 30 minutes; finally, maintain pressure and allow to cool naturally to room temperature.

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