Epoxy composite standard sample preparation method capable of eliminating bending interference and based on prismatic mandrel

Abstract

The invention belongs to the technical field of high-voltage power transmission, and discloses a prism type mandrel-based epoxy composite standard sample preparation method for eliminating bending interference, which comprises the following steps of: rolling a flexible insulating material for an epoxy composite standard sample through a prism type mandrel, and performing post-treatment to obtain an epoxy composite insulating part; wherein the flexible insulating material is insulating paper for a glue impregnated paper sleeve or fiber cloth for a tubular insulating rod. The post-treatment process is basically the same as the existing process after rolling through a cylindrical mandrel, and comprises the processes of drying, dipping and curing, cooling treatment is carried out after curing is completed, then machining and surface treatment are carried out, and after the prismatic mandrel is pulled out, the epoxy composite insulating part is obtained. Sampling is carried out at the position, corresponding to the side face of the prism-shaped core shaft, of the epoxy composite insulating part, and then the planar epoxy composite standard sample can be obtained. According to the invention, the problem of inaccurate spline performance test caused by bending of the insulation paper and the fiber cloth after winding and curing can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of high-voltage power transmission, and in particular relates to a method for preparing an epoxy composite standard sample based on a prismatic mandrel for eliminating bending interference. Background Art

[0002] The production of tubular insulating rods and bushings requires a mandrel as an auxiliary support for rolling the fiber cloth or insulating paper, respectively, followed by drying, impregnation, and curing. Traditional tubular insulating rods and rubber-impregnated paper bushings are typically rolled using a cylindrical mandrel, resulting in a cylindrical insulating component from which samples are taken for analysis. However, the cylindrical shape of the insulating component causes the cut specimen to exhibit a certain degree of curvature in both the axial and radial directions. Furthermore, the fiber orientation in the resulting specimen varies with the sampling position, causing measurement errors in tensile strength, flexural strength, and other tests, affecting test results.

[0003] Testing the electrical and mechanical properties of standard epoxy fiber composite specimens is crucial for optimizing the design of insulating components. However, epoxy fiber composites are anisotropic, and their key properties are closely related to fiber orientation. A scientific and rational method is urgently needed to prepare epoxy fiber composites that meet engineering requirements and eliminate interference from cutting orientation. Therefore, the team considered replacing the cylindrical mandrel with a prismatic mandrel to create a flat side for the insulating component. The specimens were then cut on this flat surface, eliminating the effects of bending. This also allows for more controllable sampling location and fiber orientation within the specimen, resulting in more accurate test results.

[0004] Existing methods for preparing epoxy fiber composite materials for standard spline analysis primarily involve the aforementioned method of winding insulating paper and fiber cloth using a cylindrical mandrel. Splines cut directly from insulating components such as rolled sleeves and rods are severely affected by the cutting position and direction. The cylindrical mandrel causes the rolled insulating component to exhibit a certain degree of curvature in both the axial and radial directions, and the fiber orientation within the specimen is difficult to control. This morphology can introduce errors in the measurement of tensile and electrical properties, affecting the accuracy and reliability of the results. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing epoxy composite standard samples based on a prismatic mandrel to eliminate bending interference. The present invention can solve the problem of inaccurate performance testing of the sample strips due to bending of insulating paper and fiber cloth after winding and curing.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing an epoxy composite standard sample based on a prismatic mandrel to eliminate bending interference includes the following steps: The flexible insulating material for the epoxy composite standard sample is rolled by a prismatic mandrel and then post-processed to obtain an epoxy composite insulating part; Sampling is performed at a position on the epoxy composite insulation member corresponding to the side surface of the prismatic core shaft to obtain a planar epoxy composite standard sample.

[0007] Preferably, rounded chamfers are provided at each edge of the prismatic core shaft.

[0008] Preferably, in the prismatic mandrel, the radius of the fillet Ra=(0.1-0.2)R', wherein R' is the length of the straight portion of each side of the cross section of the prismatic mandrel.

[0009] Preferably, the radius of the circumscribed circle of the cross section of the prismatic mandrel is 10 to 50 mm.

[0010] Preferably, the inner hole radius of the prismatic mandrel is 0.5 to 0.6 times the radius of the circumscribed circle of the cross section of the prismatic mandrel.

[0011] Preferably, when the flexible insulating material for the epoxy composite standard is rolled by the prismatic mandrel, the rotation speed of the prismatic mandrel is kept stable, and the rotation speed of the discharge device is adaptively changed so that the winding tension of the flexible insulating material during the rolling process reaches the preset tension requirement.

[0012] Preferably, the post-treatment includes drying, impregnation and curing processes, and after curing is completed, a cooling treatment is performed, followed by machining and surface treatment. After the prismatic core shaft is extracted, the epoxy composite insulation component is obtained.

[0013] Preferably, the cross section of the prismatic mandrel is a regular polygon, and the number of sides of the regular polygon is 6 to 8.

[0014] The present invention also provides an epoxy composite standard sample, which is prepared by the epoxy composite standard sample preparation method based on a prismatic mandrel and eliminating bending interference as described above.

[0015] Preferably, the flexible insulating material is fiber cloth or insulating paper, and the shape of the epoxy composite standard sample is at least one of a dumbbell shape, a disc shape and a plate shape.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts a prismatic core shaft to keep the rolled insulating paper flat in the axial and radial directions, eliminating the influence of paper sample bending on its performance test, and making the fiber arrangement controllable during sampling, thereby improving the accuracy and reliability of the measurement results.

[0017] Furthermore, the edges of the prism are rounded, which can effectively reduce the risk of stress concentration in the insulating paper or fiber cloth.

[0018] Furthermore, the radius and edges of the prismatic mandrel are determined according to actual conditions so that it can better simulate the winding effect of the cylindrical mandrel, thereby helping to maintain the consistency of fiber density. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a cylindrical mandrel used in the prior art for rolling a flexible insulating material for an epoxy composite standard sample; Figure 2 This is a schematic diagram of the prismatic mandrel used in the present invention for rolling the flexible insulating material used for the epoxy composite standard sample; Figure 3 It is a cross-sectional view of a cylindrical mandrel used in the prior art; Figure 4 is a cross-sectional view of a prismatic mandrel used in the present invention; Figure 5 Schematic diagram of the side surface of the hexagonal prism core shaft and the cut dumbbell-shaped, disc-shaped, and plate-shaped standard samples in the present invention.

[0020] In the figure, 1-cylindrical mandrel, 2-flexible insulating material, 3-prismatic mandrel, 4-sampling surface, 5-dumbbell-shaped standard sample, 6-disc-shaped standard sample, 7-plate-shaped standard sample. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0022] See also Figure 2 The present invention provides a method for preparing epoxy composite standard samples based on a prismatic mandrel to eliminate bending interference, comprising the following steps: The flexible insulating material 2 used for the epoxy composite standard is rolled using a prismatic mandrel 3 and then post-processed to obtain an epoxy composite insulation component. The flexible insulating material 2 is insulating paper for a rubber-impregnated paper bushing or fiber cloth for an insulating pull rod. The post-processing process is essentially the same as that used for conventional rolling using a cylindrical mandrel, including drying, impregnation, and curing. After curing, the material is cooled, then machined and surface treated. After removing the prismatic mandrel 3, the epoxy composite insulation component is obtained.

[0023] Sampling is performed on the epoxy composite insulation member at a position corresponding to the side surface of the prismatic core shaft to obtain a planar epoxy composite standard sample. Figure 5 The shape of the epoxy composite standard sample can be at least one of a dumbbell shape, a disc shape and a plate shape.

[0024] The key to the above-mentioned sample preparation method of the present invention is to improve the conventional cylindrical mandrel used in the fiber winding link into a prismatic mandrel, so that the epoxy composite standard sample finally cut is flat both in the axial and radial directions, and at the same time, the sample with the required fiber arrangement can be cut, reducing the error caused by sample bending during tensile and electrical performance tests, making the test results more accurate.

[0025] Based on the above solution, the present invention further optimizes the design, that is, each edge of the prismatic core shaft 3 is provided with a rounded chamfer, and the radius of the rounded chamfer is Ra. Figure 3 and Figure 4 The cylindrical mandrel 1 has an outer radius R and an inner radius r; R ranges from 10 to 50 mm, and r ranges from (0.5 to 0.6)R. In the prismatic mandrel 3 of the present invention, the inner radius r' is equal to r, and the radius of the fillet Ra is (0.1 to 0.2)R', where R' is the length of the straight portion of each side of the cross section of the prismatic mandrel 3. The inner radius r' of the prismatic mandrel 3 is 0.5 to 0.6 times the radius of the circumscribed circle of the cross section of the prismatic mandrel 3, where the radius of the circumscribed circle of the cross section of the prismatic mandrel 3 is equal to the outer radius of the cylindrical mandrel 1.

[0026] As a preferred embodiment of the present invention, the cross section of the prismatic core shaft 3 used in the present invention is a regular polygon with 6 to 8 sides.

[0027] After replacing the cylindrical mandrel 1 with a prismatic mandrel 3, the present invention still expects the flexible insulating material 2 to be wound at a certain tension to ensure the tightness of the flexible insulating material 2. Therefore, under the premise of controlling the constant rotation speed of the prismatic mandrel 3, the rotation speed of the discharge device needs to be changed to a certain extent. The discharge device should be controlled by variable speed. The specific speed change program can be implemented through theories such as force analysis to meet the required tension of the fiber cloth winding. To this end, as a further optimization of the above-mentioned solution of the present invention, in this embodiment, when the flexible insulating material 2 for the epoxy composite standard sample is wound by the prismatic mandrel 3, the rotation speed of the prismatic mandrel 3 is maintained stable, and the rotation speed of the discharge device is adaptively changed to ensure that the winding tension of the flexible insulating material 2 meets the preset tension requirement during the winding process.

[0028] In addition, the radius, number of edges and chamfer radius of the prismatic core shaft 3 can also be determined according to actual conditions and are not limited to the above-described solution of the present invention.

[0029] The following embodiments of the present invention are described by taking the shape of the prismatic mandrel 3 as a regular hexagonal mandrel as an example, wherein the edges of the prismatic mandrel 3 are chamfered: The preparation of the epoxy impregnated fiber winding structure in this embodiment mainly includes the following steps: Step 1. Pre-treat the prismatic mandrel and degas the epoxy resin and curing agent before mixing. Step 2. The winding machine winds the flexible insulating material onto the prismatic mandrel at a certain tension; Step 3. After winding, fully impregnate with epoxy resin and cure; Step 4. After curing is completed, the temperature is lowered, and machining and surface treatment are performed. After the mandrel is removed, the epoxy composite insulation part is obtained; Step 5. Cut and sample the side of the epoxy composite insulation according to the test standards and test requirements.

[0030] See also Figure 5 The side surface of the hexagonal prism-shaped core shaft of this embodiment is flat, and the epoxy standard sample cut after rolling is flat.

[0031] Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for preparing epoxy composite standard samples based on a prismatic mandrel to eliminate bending interference, characterized in that: The process includes the following: The flexible insulating material (2) for epoxy composite standard sample is rolled by a prismatic core shaft (3), and then post-processed to obtain an epoxy composite insulating member; Sampling is performed at a position on the epoxy composite insulation member corresponding to the side surface of the prismatic core shaft to obtain a planar epoxy composite standard sample.

2. The method for preparing epoxy composite standard samples based on a prismatic mandrel to eliminate bending interference according to claim 1, characterized in that: Each edge of the prismatic core shaft (3) is provided with a rounded chamfer.

3. The method for preparing epoxy composite standard samples based on a prismatic mandrel to eliminate bending interference according to claim 2, characterized in that: In the prismatic core shaft (3), the radius of the round chamfer Ra=(0.1-0.2)R', wherein R' is the length of the straight portion of each side of the cross section of the prismatic core shaft (3).

4. The method for preparing epoxy composite standard samples based on a prismatic mandrel to eliminate bending interference according to claim 1, characterized in that: The radius of the circumscribed circle of the cross section of the prismatic core shaft (3) is 10 to 50 mm.

5. The method for preparing epoxy composite standard samples based on a prismatic mandrel to eliminate bending interference according to claim 1, characterized in that: The inner hole radius of the prismatic core shaft (3) is 0.5 to 0.6 times the radius of the circumscribed circle of the cross section of the prismatic core shaft (3).

6. The method for preparing epoxy composite standard samples based on a prismatic mandrel to eliminate bending interference according to claim 1, characterized in that: When the flexible insulating material (2) for epoxy composite standard sample is rolled by the prismatic core shaft (3), the rotation speed of the prismatic core shaft (3) is kept stable, and the rotation speed of the discharge device is adaptively changed so that the winding tension of the flexible insulating material (2) during the rolling process reaches a preset tension requirement.

7. The method for preparing epoxy composite standard samples based on a prismatic mandrel to eliminate bending interference according to claim 1, characterized in that: The post-processing includes drying, impregnation and curing processes. After the curing is completed, a cooling treatment is performed, followed by machining and surface treatment. After the prismatic core shaft (3) is extracted, an epoxy composite insulation part is obtained.

8. The method for preparing epoxy composite standard samples based on a prismatic mandrel to eliminate bending interference according to claim 1, characterized in that: The cross section of the prismatic core shaft (3) is a regular polygon, and the number of sides of the regular polygon is 6 to 8.

9. An epoxy composite standard, characterized in that: The epoxy composite standard sample is prepared by the epoxy composite standard sample preparation method based on a prismatic mandrel to eliminate bending interference according to any one of claims 1 to 8.

10. An epoxy composite standard sample according to claim 9, characterized in that: The flexible insulating material (2) is fiber cloth or insulating paper, and the shape of the epoxy composite standard sample is at least one of a dumbbell shape, a disc shape, and a plate shape.

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