Method for evaluating a twist amount

Abstract

The application provides a torsion amount evaluation method, which is applied to the study of the torsion amount of prepreg laying on a non-developable surface in the preparation process of a carbon fiber mirror and comprises the following steps: S1, a mold model is established and is divided into a first grid on the surface, and first grid data is exported; S2, the first grid data is mapped onto a plane disc through harmonic mapping; S3, a second grid is established and is overlaid on the plane disc; S4, the second grid is mapped onto the surface of the mold model based on the inverse mapping of the harmonic mapping; and S5, the first grid and the second grid on the surface of the mold model are projected to a plane, and the torsion amount is obtained according to the interval of the first parallel lines. The application fills the gap in the study of the torsion amount of prepreg laying in the preparation of a carbon fiber mirror in the prior art, can quickly obtain the torsion amount of prepreg laying on a non-developable surface, thereby evaluates the layability and the preparability of a corresponding type of carbon fiber mirror, and provides planning and support for the laying path in the laying process.

Description

Technical Field

[0001] This invention relates to the field of optical element fabrication, and specifically provides a method for evaluating the torsion of prepreg laid on an undevelopable surface during the fabrication of carbon fiber mirrors. Background Technology

[0002] Carbon fiber reinforced polymer (CFRP) composites are a popular material for mirror fabrication due to their high specific stiffness, strong design flexibility, and good corrosion resistance. Mirror surfaces mainly include planes, spheres, parabolic surfaces, hyperboloids, and freeform surfaces. Based on differential geometry and using Gaussian curvature as the standard, mirror surfaces can be divided into developable surfaces (with zero Gaussian curvature) and non-developable surfaces (with non-zero Gaussian curvature).

[0003] In the fabrication of non-developable carbon fiber mirrors, carbon fiber prepreg (planar material) is laid on the mold surface using a multi-piece splicing method. Although this method achieves good adhesion to the mold surface, the splicing gaps severely affect the fabrication accuracy of the carbon fiber mirror. Since the fabrication of carbon fiber mirrors requires a mirror-like surface finish, seamless splicing of the carbon fiber prepreg is necessary. However, during the fabrication process, the prepreg laid on the non-developable mold will cause fiber bundle twisting, tearing, and resin layer distortion, all of which affect the fabrication accuracy. Therefore, a method for evaluating the twisting amount of the prepreg laid on the non-developable surface during carbon fiber mirror fabrication, enabling quantitative analysis of the twisting amount, is of significant research value. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for evaluating the torsion of prepreg laid on an unspreadable surface during the fabrication of carbon fiber reflectors. This method can quickly obtain the torsion value, thereby evaluating the layability and fabrication feasibility of the corresponding type of carbon fiber reflector, and providing layup path planning support for the layup process.

[0005] The torsion assessment method provided by this invention is specifically applied to the study of the torsion of prepreg laid on an undevelopable surface during the fabrication process of carbon fiber mirrors, and includes the following steps:

[0006] S1. Create a mold model, divide the surface of the mold model into the first mesh, and export the first mesh data;

[0007] S2. Map the first grid data onto the planar disk using harmonic mapping;

[0008] S3. The carbon fibers in the prepreg of the mold model are equivalent to the first parallel lines, and the resin in the prepreg is equivalent to the second parallel lines. The first parallel lines and the second parallel lines are perpendicular to each other to form a second grid. The second grid is then covered on the flat disk.

[0009] S4. Based on the inverse mapping of the harmonic mapping, the second mesh is mapped onto the surface of the mold model;

[0010] S5. Project the first and second meshes on the surface of the mold model onto the plane, and obtain the amount of twist based on the spacing of the first parallel lines on the plane.

[0011] Preferably, the mold model is modeled using UG software.

[0012] Preferably, the surface of the mold model is divided into a first mesh using a Delaunay triangulation mesh.

[0013] Preferably, the flat disk is a flat circular disk.

[0014] Preferably, after S5, the amount of torsion can be accurately calculated by increasing the number of the first and second parallel lines.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0016] This invention fills the gap in the existing technology regarding the study of the torsion amount of prepreg in the fabrication of carbon fiber reflectors. This invention can quickly obtain the torsion amount of prepreg laid on an unspreadable surface, thereby evaluating the layability and fabrication feasibility of the corresponding type of carbon fiber reflector, and providing planning and support for the layup path in the layup process. Attached Figure Description

[0017] Figure 1 This is a flowchart of a torsion estimation method provided according to an embodiment of the present invention;

[0018] Figure 2 This is a curve showing the change in the amount of twist versus the number of the first parallel line, provided according to an embodiment of the present invention.

[0019] Figure 3 This is a graph showing the variation of the torsion amount with the number of the first parallel line under different radii of curvature and aperture conditions, provided by the present invention. Detailed Implementation

[0020] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0022] Figure 1The flowchart of the torsion amount evaluation method provided according to an embodiment of the present invention is shown.

[0023] like Figure 1 As shown, the torsion evaluation method of the present invention is described in detail in conjunction with the process of preparing a spherical reflector of concave carbon fiber composite material for long-wave infrared, including the following steps:

[0024] S1. The effective aperture of the carbon fiber spherical reflector to be prepared is determined to be 200mm. Due to the edge effect, the aperture of the carbon fiber spherical reflector is prepared according to 220mm, and the radius of curvature of the reflector is 750mm. Based on the parameters of the carbon fiber spherical reflector to be prepared, the aperture of the carbon fiber spherical reflector preparation mold is determined to be 220mm and the radius of curvature is 750mm. According to the set parameters of the carbon fiber spherical reflector preparation mold, the model of the carbon fiber spherical reflector preparation mold is built using UG modeling software. The diameter of the mold model is 220mm, and the light-transmitting surface is a spherical cap with a radius of curvature of 750mm. The spherical cap surface is imported into Comsol software, and the surface of the mold model is divided into Delaunay triangulation meshes with a spacing of 1mm. The obtained Delaunay triangulation mesh data is imported into Meshlab and converted into mesh data that can be read by the harmonic processing program, i.e., the first mesh data, and then exported.

[0025] S2. Import the first mesh data obtained in S1 into the harmonic mapping program, which is used to map the surface mesh data of the carbon fiber spherical mirror preparation mold model onto the planar disk.

[0026] S3. The carbon fibers in the carbon fiber prepreg of the mold model are equivalent to 21 first parallel lines, and the resin in the prepreg is equivalent to 21 second parallel lines. The first parallel lines and the second parallel lines are perpendicular to each other to form a second grid. The second grid is then covered on the planar disk.

[0027] S4. Based on the inverse mapping of the harmonic mapping, the second mesh is mapped onto the surface of the mold model.

[0028] S5. Project the first and second grids on the surface of the mold model onto the plane, and obtain the amount of twist based on the spacing of the first parallel lines.

[0029] Figure 2 The curve showing the change in the amount of twist versus the number of the first parallel line provided according to an embodiment of the present invention is illustrated.

[0030] like Figure 2As shown in the figure, the curves of the variation of the torsion amount of the 10 first parallel lines of the hemispherical crown are displayed. In this embodiment, it was found that the maximum torsion amount occurred at the 6th first parallel line, with a maximum distance of 0.169 mm. The distance of the sixth line relative to the symmetrical mid-plane of the reflector is 100 mm, and the torsion amount accounts for 1.69% of the distance.

[0031] After initially obtaining the torsion data, this invention can further refine the torsion calculation by increasing the number of first and second parallel lines and reducing their spacing. The first and second grids projected onto the plane tend to overlap in areas with dense lines and tear in areas with sparse lines, similar to contour lines. By observing the changes in torsion, the tiling trajectory can be obtained, thereby evaluating the tiling and fabrication feasibility of the reflector and providing planning and support for the tiling path during the tiling process.

[0032] The layup twist of a carbon fiber spherical mirror is mainly related to two factors: aperture and radius of curvature. The following study investigates the variation of layup twist under different radii of curvature and aperture conditions. With the aperture of the carbon fiber spherical mirror remaining constant, the layup twist is obtained by changing the radius of curvature using the method of this invention. Since both aperture and radius of curvature affect the layup twist of the carbon fiber spherical mirror blank, the ratio of radius of curvature to aperture is used as a reference value to analyze its relationship with the layup twist. The ratio of radius of curvature to aperture is defined as F. Q-C That is, to enlarge or reduce the aperture and radius of curvature by the same magnification.

[0033] Figure 3 The curves showing the variation of the amount of torsion with the number of the first parallel line under different radii of curvature and aperture conditions provided by the present invention are shown.

[0034] like Figure 3 As shown, taking carbon fiber spherical mirrors with an aperture of 200mm and radii of curvature of 400mm, 600mm and 800mm respectively as examples, the amount of twist in the laying of the carbon fiber spherical mirror blank is analyzed, and the relationship between the amount of twist and the ratio between the two is evaluated.

[0035] Depend on Figure 3 Therefore, for different F Q-C The value, the amount of distortion, and the trend of change in the line number are consistent with the change of F. Q-C As the value increases, the amount of twist decreases; that is, for the same diameter, the larger the radius of curvature, the less twist occurs during installation. Based on this trend, it can be concluded that when F... Q-C When the value approaches infinity, the carbon fiber spherical mirror blank becomes a carbon fiber planar mirror blank, and there will be no twisting during installation.

[0036] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0037] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method of evaluating a twist amount, characterized by, The method comprises the following steps: S1, establishing a mold model, dividing the surface of the mold model into a first grid, and exporting first grid data; S2, mapping the first grid data to a planar disc through harmonic mapping; S3, equivalent carbon fibers in a prepreg of the mold model to first parallel lines, equivalent resin in the prepreg to second parallel lines, the first parallel lines and the second parallel lines being perpendicular to each other to form a second grid, and covering the second grid on the planar disc; S4, mapping the second grid to the surface of the mold model based on inverse mapping of the harmonic mapping; S5, projecting the first grid and the second grid on the surface of the mold model to a plane, and obtaining a twist amount according to the interval of the first parallel lines on the plane.

2. The torsion amount evaluation method according to claim 1, characterized by, The mold model is modeled by using UG software.

3. The torsion amount evaluation method according to claim 1, characterized by, The surface of the mold model is divided into the first grid by using Delaunay triangulation grid division.

4. The torsion amount evaluation method according to claim 1, characterized by, The planar disc is a planar disc.

5. The torsion amount evaluation method according to claim 1, wherein After S5, the twist amount can be accurately solved by increasing the number of the first parallel lines and the second parallel lines.

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