Laminate condition calculation method, laminate condition calculation device and laminate condition calculation program

Abstract

Laminate condition calculation method of a carbon fiber reinforced plastic laminate (10), wherein the method comprises: Obtaining a plurality of images of a cross-section (15) of the laminate (10) orthogonal to a lamination direction (P) by imaging the laminate (10) with X-rays at a plurality of different positions in the lamination direction (P), wherein the laminate (10) comprises first layers (11) with carbon fibers oriented in a first direction orthogonal to the lamination direction (P) and second layers (12) with carbon fibers oriented in a second direction which is orthogonal to the lamination direction (P) and differs from the first direction, wherein the first layers (11) and the second layers (12) are laminated alternately; Calculating a parameter correlated with the number of cavities formed in the first layers (11) and the second layers (12) from the majority of obtained images, and distinguishing between the first layers (11) and the second layers (12) using the calculated parameter; and Eliminating the influence of second cavities from an area containing first cavities in the majority of obtained images, where the cavities extending in the first direction are defined as the first cavities and the cavities extending in the second direction are defined as the second cavities; where the parameter of a standard deviation (σ) corresponds to a luminance of a region containing the first cavities in the majority of images.

Description

background

[0001] The present invention relates to a laminate state calculation method, a laminate state calculation device, and a laminate state calculation program. The present invention relates, for example, to a laminate state calculation method, a laminate state calculation device, and a laminate state calculation program for a carbon fiber reinforced plastic laminate.

[0002] Japanese patent application JP 2008-122 178 A discloses a method for detecting a laminate state by calculating a power spectrum using a CT image and obtaining a lamination angle of a fiber arc from the power spectrum in order to detect a laminate state of a laminate.

[0003] Japanese patent application JP 2007-187 545 A discloses a method for determining the orientation direction of fibers in a fiber-reinforced plastic used in a hydrogen tank by capturing a trajectory of a bright part using a reflection characteristic of light to determine the orientation direction of the fibers.

[0004] Furthermore, US Patent 2015 / 0046098A1 discloses a method and a system for characterizing and quantifying composite laminate structures. The method and system take a composite laminate with unknown composition and layer stack sequence and determine various pieces of information about each layer, such as layer stack, orientation, microstructure, and type. The method and system can distinguish between fabric types that may exhibit similar planar stiffness behavior but would give rise to different failure mechanisms. The information about each layer can then be used to derive the bulk properties of the laminate from externally provided constitutive properties of the fiber and matrix, including tensile stiffness, flexural-strain coupling stiffness, bending stiffness, and the like.

[0005] US Patent 2015 / 0212008A1 discloses a device for checking the application condition of a plurality of strips of fiber-reinforced plastic tape arranged in rows on a surface of a structure, wherein the device comprises a lighting component that emits observation light beams in the direction of an inspection area of ​​the fiber-reinforced plastic tape, an observation component that observes reflected light from the inspection area, and an inspection component that checks the application condition of the fiber-reinforced plastic tape based on an image observed by the observation component.The illumination component comprises several irradiation units that illuminate simultaneously and are arranged such that a pair of observation light rays is emitted from directions that are symmetrical to each other with respect to a normal of the test area, and an illumination direction change component that changes the directions of the pair of observation light rays emitted by the illumination component around the normal.

[0006] Further relevant prior art is disclosed in the non-patent literature SCHUMACHER, David [et al.]: Defect recognition in CFRP components using various NDT methods within a smart manufacturing process. In: AIP conference proceedings, Vol. 1949, 2018, No. 1, Article no. 020024, 11 pp. ISSN 0094-243X. https: / / doi.org / 10.1063 / 1.5031521. Summary

[0007] Since the detection method of Japanese patent application JP 2008-122178A requires CT imaging with a resolution high enough to confirm the orientation of fibers, it is difficult to detect the laminate condition over a large area. With the determination method of Japanese patent application JP 2007-187545A, only the orientation of the fibers on an outermost layer of the hydrogen tank can be determined, and it is difficult to determine the orientation of fibers inside the hydrogen tank.

[0008] The present invention is made to solve such a problem and provides a laminate state calculation method, a laminate state calculation device and a laminate state calculation program which can easily determine a laminate state of a laminate comprising a plurality of laminated layers with different fiber orientations in a carbon fiber reinforced plastic or the like.

[0009] An exemplary aspect corresponds to a method for calculating a laminate state, or a laminate state calculation method, of a carbon fiber reinforced plastic laminate. The method comprises: obtaining a plurality of images of a cross-section of the laminate orthogonal to a lamination direction by imaging the laminate with X-rays at a plurality of different positions in the lamination direction, wherein the laminate comprises first layers with carbon fibers oriented or aligned in a first direction orthogonal to the lamination direction, and second layers with carbon fibers oriented in a second direction which is orthogonal to the lamination direction and differs from the first direction, wherein the first layers and the second layers are laminated alternately; and calculating a parameter that corresponds to a number orThe quantity of voids formed in the first and second layers is correlated from the majority of images obtained, and the difference between the first and second layers is determined using the calculated parameter. With such a configuration, it is possible to easily determine the laminate condition of a CFRP or CFK laminate 10.

[0010] The above method further includes eliminating the influence of secondary cavities from an area containing primary cavities in the majority of obtained images, provided that the cavities extending in the first direction are defined as the primary cavities and the cavities extending in the second direction are defined as the secondary cavities. With such a configuration, it is possible to improve the accuracy of determining the laminate condition.

[0011] In the above method, eliminating the influence of the second cavities can involve: converting the image into a power spectrum by a fast Fourier transform; removing a spectrum of the second cavities from the converted power spectrum; and converting the power spectrum, from which the spectrum of the second cavities has been removed, back into the image by an inverse fast Fourier transform. With such a configuration, it is possible to further improve the accuracy of determining the laminate state.

[0012] In the above method, the parameter of a standard deviation corresponds to the luminance of a region containing the first cavities in the majority of images. With such a configuration, it is possible to improve the accuracy of determining the laminate condition.

[0013] In another embodiment of the above method, the parameter corresponds to the change in a standard deviation of the luminance of a region containing the first cavities in the majority of images. With such a configuration, it is possible to improve the accuracy of determining the laminate condition.

[0014] In the above method, the laminate can have a cylindrical shape with a central axis, and the lamination direction can be orthogonal to the central axis. With such a configuration, it is possible to improve the accuracy of determining the laminate condition.

[0015] In the above method, the second direction can correspond to a direction of rotation about the central axis, and the first direction can correspond to a direction inclined to the second direction. With such a configuration, it is possible to improve the accuracy of determining the laminate condition.

[0016] Another exemplary aspect corresponds to a laminate state calculation device for a carbon fiber reinforced plastic laminate, comprising: an imaging unit configured to obtain a plurality of images of a cross-section of the laminate orthogonal to a lamination direction by imaging the laminate with X-rays at a plurality of different positions in the lamination direction, wherein the laminate comprises first layers of carbon fibers oriented in a first direction orthogonal to the lamination direction and second layers of carbon fibers oriented in a second direction which is orthogonal to the lamination direction and differs from the first direction, wherein the first layers and the second layers are laminated alternately;and an image processing unit configured to calculate a parameter, correlated with a number of cavities formed in the first and second layers, from the majority of acquired images, and to differentiate between the first and second layers using the calculated parameter. With such a configuration, it is possible to determine the laminate condition of the CFRP laminate 10 in a simple manner.

[0017] In the aforementioned laminate condition calculation device, the image processing unit is configured to eliminate the influence of secondary cavities from an area containing primary cavities in the majority of acquired images, provided that the cavities extending in the first direction are defined as the primary cavities and the cavities extending in the second direction are defined as the secondary cavities. Such a configuration makes it possible to improve the accuracy of determining the laminate condition.

[0018] In the aforementioned laminate state calculation device, if the image processing unit eliminates the influence of the second cavities, the image processing unit can be configured to convert the image into a power spectrum by means of a fast Fourier transform; the image processing unit can be configured to remove a spectrum of the second cavities from the converted power spectrum; and the image processing unit can be configured to convert the power spectrum from which the spectrum of the second cavities has been removed into the image by means of an inverse fast Fourier transform. With such a configuration, it is possible to further improve the determination accuracy of the laminate state.

[0019] In the aforementioned laminate condition calculation device, the parameter of a standard deviation corresponds to the luminance of an area containing the first cavities in the majority of images. With such a configuration, it is possible to improve the accuracy of determining the laminate condition.

[0020] In another embodiment of the aforementioned laminate condition calculation device, the parameter corresponds to the change in a standard deviation of the luminance of a region containing the first cavities in the majority of images. With such a configuration, it is possible to improve the accuracy of determining the laminate condition.

[0021] In the aforementioned laminate condition calculation device, the laminate can have a cylindrical shape with a central axis, and the lamination direction can be orthogonal to the central axis. With such a configuration, it is possible to improve the accuracy of determining the laminate condition.

[0022] In the aforementioned laminate condition calculation device, the second direction can correspond to a rotational direction about the central axis, and the first direction can correspond to a direction inclined to the second direction. With such a configuration, it is possible to improve the accuracy of determining the laminate condition.

[0023] Another exemplary aspect corresponds to a laminate state calculation program for a carbon fiber reinforced plastic laminate, which causes a computer to perform the following: Obtaining a plurality of images of a cross-section of the laminate orthogonal to a lamination direction by imaging the laminate with X-rays at a plurality of different positions in the lamination direction, wherein the laminate comprises first layers with carbon fibers oriented in a first direction orthogonal to the lamination direction, and second layers with carbon fibers oriented in a second direction which is orthogonal to the lamination direction and different from the first direction, wherein the first layers and the second layers are laminated alternately;and calculating a parameter correlated with the number of cavities formed in the first and second layers from the majority of images obtained, and distinguishing between the first and second layers using the calculated parameter. With such a configuration, it is possible to determine the laminate state of the CFRP laminate 10 in a simple manner.

[0024] The aforementioned laminate state calculation program further causes the computer to eliminate the influence of secondary cavities from an area containing primary cavities in the majority of acquired images, provided that the cavities extending in the first direction are defined as primary cavities and the cavities extending in the second direction are defined as secondary cavities. With such a configuration, it is possible to improve the accuracy of the laminate state determination.

[0025] In the aforementioned laminate state calculation program, if the computer is instructed to eliminate the influence of the second cavities, the computer can further be instructed to perform the following: converting the image into a power spectrum by means of a fast Fourier transform; removing a spectrum of the second cavities from the converted power spectrum; and converting the power spectrum from which the spectrum of the second cavities has been removed back into the image by means of an inverse fast Fourier transform. With such a configuration, it is possible to further improve the accuracy of the laminate state determination.

[0026] In the aforementioned laminate condition calculation program, the parameter of a standard deviation corresponds to the luminance of a region containing the first cavities in the majority of images. With such a configuration, it is possible to further improve the accuracy of determining the laminate condition.

[0027] In another embodiment of the aforementioned laminate state calculation program, the parameter corresponds to the change in a standard deviation of the luminance of a region containing the first cavities in the majority of images. With such a configuration, it is possible to improve the accuracy of determining the laminate state.

[0028] In the aforementioned laminate state calculation program, the laminate can have a cylindrical shape with a central axis, and the lamination direction can be orthogonal to this central axis. With such a configuration, it is possible to improve the accuracy of determining the laminate state.

[0029] According to the embodiments, it is possible to provide a laminate state calculation method, a laminate state calculation device and a laminate state calculation program which can determine a laminate state in a simple manner.

[0030] The foregoing and further tasks, features and advantages of the present invention will become more apparent from the detailed description given below and the accompanying figures, which are provided for illustrative purposes only, and are therefore not intended to limit the present invention. Brief description of the illustrations Fig. Figure 1 is a perspective cross-sectional view showing an example of a CFRP laminate according to one embodiment; Fig. Figure 2 is a perspective cross-sectional view showing an example of a CFRP laminate according to the embodiment; Fig. Figure 3 is a configuration diagram showing an example of a laminate state calculation device according to the embodiment; Fig. Figure 4 shows an example of an imaging method of an imaging unit in the laminate condition calculation device according to the embodiment; Fig. Figure 5 shows an example of the imaging method of the imaging unit in the laminate condition calculation device according to the embodiment; Fig. Figure 6 shows an example of the imaging method of the imaging unit in the laminate condition calculation device according to the embodiment; Fig. Figure 7 shows an example of the imaging method of the imaging unit in the laminate condition calculation device according to the embodiment; Fig. Figure 8 is a schematic illustration showing an example of an image of a cross-section taken by the imaging unit of the laminate condition calculation device according to the embodiment; Fig. Figure 9 is a flowchart showing an example of a laminate state calculation method according to the embodiment; Fig. Figure 10 is a schematic figure showing an image of an area with cavities used in the laminate state calculation method according to the embodiment, and shows an area that is in Fig. 8 is marked with an X; Fig. Figure 11 is a schematic figure showing an example of power spectra in the laminate state calculation method according to the embodiment; Fig. 12 is a schematic figure showing an example of power spectra, one of which is a spectrum formed by the cavities in a circumferential direction, removed by the laminate state calculation method according to the embodiment; Fig. Figure 13 is a schematic illustration showing an example of a reverse-converted image in the laminate state calculation method according to the embodiment; Fig. Figure 14 is a diagram showing an example of a standard deviation of an image's luminance used in the laminate state calculation method according to the embodiment, wherein the horizontal axis represents a depth of an inner circumferential surface of a CFRP laminate and the vertical axis represents the standard deviation; and Fig. Figure 15 is a diagram showing an example of the change in standard deviation used in the laminate state calculation method according to the embodiment, wherein the horizontal axis represents the depth of the inner circumferential surface and the vertical axis represents the change in standard deviation. Description of embodiments

[0031] The present invention is described below with reference to embodiments of the invention, the invention being not limited to the following embodiments according to the claims. Furthermore, not all of the components described in the embodiments are essential for solving the problem. For the sake of clarity, the following description and the figures have been omitted and simplified where necessary. In the figures, the same elements are designated with the same reference numerals, and repeated descriptions are omitted where necessary. [Version]

[0032] A laminate state calculation method according to one embodiment is described. First, the laminate in question is described. Next, a laminate state calculation device for calculating the laminate state is described. Finally, the laminate state calculation method is described. <laminat>

[0033] A laminate whose laminate state is calculated by the laminate state calculation method according to this embodiment is, for example, a fiber-reinforced plastic (hereinafter referred to as FRP or FRP) laminate, such as a carbon fiber-reinforced plastic (hereinafter referred to as CFRP) laminate. The CFRP laminate is described below as an example of the FRP laminate. The CFRP laminate comprises a plurality of laminated layers. Each layer comprises a plurality of carbon fibers oriented or aligned in a predetermined direction.

[0034] The Fig. 1 and Fig. Figure 2 shows perspective cross-sectional views illustrating an example of the CFRP laminate according to the embodiment. As shown in Fig. As shown in Figure 1, a CFRP laminate 10 can be in the form of a plate. As in Fig. As shown in Figure 2, the CFRP laminate 10 can have a cylindrical shape encompassing a central axis C. In the case of the plate-shaped CFRP laminate 10, the lamination direction P is orthogonal to a plate surface. In the case of the cylindrical CFRP laminate 10, however, the lamination direction P is orthogonal to the central axis C of the cylinder. The orientation direction of the fibers contained in each layer of the CFRP laminate 10 corresponds, for example, to the predetermined direction orthogonal to the lamination direction.

[0035] A fiber-reinforced composite (FRP) laminate, such as the CFRP laminate 10, is used for various components, including those in automobiles and aircraft. For example, the CFRP laminate 10 can be used for the hydrogen tank of a fuel cell vehicle. The CFRP laminate 10 can also be used for other components beyond hydrogen tanks.

[0036] In the CFRP laminate 10, which is to be processed by the laminate state calculation method according to this embodiment, the orientation direction of each layer differs from the orientation direction of the upper and lower layers. For example, if the CFRP laminate 10 comprises layers L1, L2, L3, and ..., and LN, the orientation direction of layer L2 differs from the orientation directions of layers L1 and L3. For example, in the CFRP laminate 10, first layers 11 and second layers 12 are laminated alternately. In the first layer 11, carbon fibers are oriented in a first direction orthogonal to the lamination direction P, while in the second layer 12, carbon fibers are oriented in a second direction that is orthogonal to the lamination direction P and differs from the first direction.

[0037] As in Fig. As shown in Figure 2, in the case of the cylindrical CFRP laminate 10, the direction orthogonal to the central axis C and to the lamination direction P, i.e., the direction of rotation about the central axis C, is referred to in this description, for the sake of simplicity, as the circumferential direction H2. The direction that is orthogonal to the lamination direction P and inclined to the circumferential direction H2 is referred to in this description, for the sake of simplicity, as a spiral direction H1. In this case, the first direction corresponds, for example, to the spiral direction H1 and the second direction to the circumferential direction H2. In the CFRP laminate 10, the spirally wound first layers 11, which are oriented in the spiral direction H1, and the circumferentially wound second layers 12, which are oriented in the circumferential direction H2, are therefore laminated alternately. <laminatzustandsberechnungsvorrichtung>

[0038] Next, a laminate condition calculation device according to this embodiment will be described. Fig. Figure 3 is a configuration diagram showing an example of the laminate condition calculation device according to the embodiment. As in Fig. As shown in Figure 3, the laminate condition calculation device 1 comprises an imaging unit 2 and an image processing unit 3. The imaging unit 2 is, for example, an X-ray CT scanner. The laminate condition calculation device 1 obtains multiple images of a cross-section by having the imaging unit 2 image the CFRP laminate 10 with X-rays. The laminate condition calculation device 1 uses the image processing unit 3 to determine the laminate condition of each layer of the CFRP laminate 10 from the multiple images of the cross-section. The operation of the laminate condition calculation device 1 is described in detail below with reference to the figures.

[0039] The Fig. Figures 4 to 7 show an example of an imaging method which is carried out by the imaging unit 2 in the laminate condition calculation device 1 according to the embodiment. Fig. Figure 8 is a schematic illustration showing an example of the cross-sectional image taken by the imaging unit 2 at the laminate condition calculation device 1 according to the embodiment.

[0040] As in Fig. As shown in Figure 4, the imaging unit 2 emits X-ray radiation XR from the lamination direction P of the CFRP laminate 10. This allows the imaging unit 2 to image a cross-section 15 orthogonal to the lamination direction P at a predetermined depth Z of the CFRP laminate 10. Then, by rotating the CFRP laminate 10 about the central axis C, as shown in Figure 4, the following images are obtained: Fig. Figure 5 shows images of the cross-section 15 of the CFRP laminate 10 obtained at constant depth Z for 360 degrees.

[0041] Next, as in Fig. As shown in Figure 6, the imaging unit 2 expands the images of the cross-section 15 and, as shown in Figure 6, achieves a resolution of 15 cm. Fig. Figure 7 shows a planar image of cross-section 15. In this way, the imaging unit 2, as shown in Fig. Figure 8 shows the image of cross-section 15 of the CFRP laminate 10. The image of cross-section 15 obtained by the imaging unit 2 depicts a pattern caused by the cavities. For example, the image of cross-section 15 shows a pattern extending in the spiral direction H1 and a pattern extending in the circumferential direction H2.

[0042] The pattern extending in the spiral direction H1 corresponds to a pattern caused by the cavities formed by the orientation of the carbon fibers in the spiral direction H1. That is, the pattern extending in the spiral direction H1 is formed by the cavities that extend in the spiral direction. On the other hand, the pattern extending in the circumferential direction H2 corresponds to a pattern caused by the cavities formed by the orientation of the carbon fibers in the circumferential direction H2. That is, the pattern extending in the circumferential direction H2 is formed by the cavities extending in the circumferential direction.

[0043] If, for example, the resulting image of the cross-section 15 represents the spirally wound first layer 11, then the pattern caused by the cavities is initially the only pattern caused by the cavities extending in the spiral direction H1. However, cavities extending in the circumferential direction H2 can be formed in the first layer 11 during the manufacturing process of the CFRP laminate 10. Consequently, the pattern caused by the cavities extending in the circumferential direction H2 is also formed in the first layer 11.

[0044] Imaging Unit 2 repeats the steps described in the Fig. The processes shown in Figures 4 to 7 are carried out at a plurality of different positions (depths) in the lamination direction P. As described above, the imaging unit 2 images the CFRP laminate 10 at a plurality of different positions in the lamination direction P using X-rays and thereby obtains a plurality of images of the cross-section 15 orthogonal to the lamination direction P.

[0045] The image processing unit 3 processes the majority of the images of cross-section 15 acquired by the imaging unit 2. Therefore, the image processing unit 3 can be comprised of hardware components, such as a central processing unit (CPU), a read-only memory (ROM), a random-access memory (RAM), an interface unit (I / F), etc. The CPU processes the input images of cross-section 15 and the like. The ROM stores a laminate state calculation program, a control program, and the like, which are executed by the CPU. The RAM stores the images of cross-section 15 and the like. The interface unit (I / F) is used for input and output of data and the like to / from other devices, such as the imaging unit 2, a display device, and an external storage device. The CPU, the ROM, the RAM, and the interface unit are interconnected via a data bus or the like.

[0046] Image processing unit 3 obtains the number of voids formed in the first layers 11 and the second layers 12 from the acquired majority of images of cross-section 15. Image processing unit 3 therefore calculates a parameter that is correlated with the number of voids. This parameter corresponds, for example, to a standard deviation σ and a change Δσ of the standard deviation σ. Image processing unit 3 then uses the calculated parameter to distinguish between the first layers 11 and the second layer 12. The following description of the laminate state calculation method details the processes of imaging unit 2 and image processing unit 3. <laminatzustandsberechnungsverfahren>

[0047] Next, the laminate condition calculation method according to the embodiment is described. Fig. Figure 9 is a flowchart showing an example of the laminate state calculation method according to the embodiment.

[0048] As in step S11 of Fig. As shown in Figure 9, the majority of images of the cross-section 15 of the CFRP laminate 10 are obtained. In particular, the imaging unit 2 images the CFRP laminate 10 at a plurality of different positions in the lamination direction P using X-rays, thereby obtaining a plurality of images of the cross-section 15 orthogonal to the lamination direction P.

[0049] Fig. Figure 10 is a schematic figure showing an image of an area with cavities used in the laminate state calculation method according to the embodiment, and shows an area that is in Fig. 8 is marked with an X. As in Fig. As shown in Figure 10, the image processing unit 3 uses the area with the pattern caused by the cavities in the image of cross-section 15 for processing. The area with the pattern caused by the cavities includes a pattern VP1, caused by the cavity extending in the spiral direction H1, and a pattern VP2, caused by the cavity extending in the circumferential direction H2.

[0050] The image processing unit 3 can eliminate the influence of the cavities extending in the circumferential direction H2 from the area with the cavities extending in the spiral direction H1 in the majority of acquired images of cross-section 15. The following steps S12 to S14 serve to eliminate the influence of the cavities extending in the circumferential direction H2 in the majority of acquired images.

[0051] As in step S12 of Fig. As shown in Figure 9, the performance spectrum is obtained by a fast Fourier transform (hereinafter referred to as FFT) of the images of cross-section 15. Fig. Figure 11 is a schematic diagram showing an example of the performance spectra in the laminate state calculation method according to the embodiment. As in Fig. As shown in Figure 11, the image processing unit 3 converts the image of the cross-section 15 into a power spectrum using FFT. Therefore, power spectra are obtained at spatial frequencies u and v. The obtained power spectra include a spectrum SP1, which is caused by the cavities in the spiral direction H1, and a spectrum SP2, which is caused by the cavities in the circumferential direction H2.

[0052] Next, as in step S13 of Fig. Figure 9 shows the spectrum SP2 masked to remove the spectrum SP2 caused by the cavities in the circumferential direction H2. Fig. Figure 12 is a schematic diagram showing an example of the power spectrum obtained by removing the spectrum SP2 caused by the cavities in the circumferential direction H2 using the laminate state calculation method according to the embodiment. As shown in Fig. As shown in Figure 12, the image processing unit 3 removes the SP2 spectrum from the converted power spectrum.

[0053] Next, as in step S14 of Fig. As shown in 9, the power spectrum is converted back into an image using inverse FFT. Fig. Figure 13 is a schematic diagram showing an example of the image reconstructed by the laminate state calculation method according to the embodiment. As in Fig. As shown in Figure 13, the image processing unit 3 converts the power spectrum, from which the spectrum SP2 has been removed, into an image using the inverse FFT. The pattern VP2, extending in the circumferential direction H2, has been removed from the converted image.

[0054] The image processing unit 3 obtains the image, which is obtained by performing FFT processing, masking processing and inverse FFT processing on the majority of images of the cross-section, which were taken at the majority of different positions in the lamination direction.

[0055] Next, as in step S15 of Fig. Figure 9 shows how to obtain the standard deviation σ of the luminance of the acquired image. In particular, the image processing unit 3 calculates the standard deviation σ of the luminance from the luminance of the area containing the pattern of cavities in each image.

[0056] Fig. Figure 14 is a diagram showing an example of the standard deviation σ of the image luminance used in the laminate state calculation method according to the embodiment, wherein the horizontal axis represents the depth of an inner circumferential surface of the CFRP laminate 10 and the vertical axis represents the standard deviation σ. As in Fig. As shown in Figure 14, the standard deviation σ of the luminance of the image changes with a change in depth of the inner circumferential surface of the CFRP laminate 10.

[0057] Next, as in step S16 of Fig. Figure 9 shows that the obtained standard deviation σ is differentiated to obtain the change in the standard deviation σ. In particular, the image processing unit 3 differentiates the standard deviation σ calculated from the luminance of the image. Therefore, the image processing unit 3 calculates the change Δσ of the standard deviation σ. Fig. Figure 15 is a diagram showing an example of the change Δσ of the standard deviation σ in the laminate state calculation method according to the embodiment, wherein the horizontal axis represents the depth of the inner circumferential surface and the vertical axis represents the change Δσ of the standard deviation σ. As in Fig. As shown in Figure 15, the amount of change Δσ of the standard deviation σ varies with the change in depth of the inner circumferential surface of the CFRP laminate 10.

[0058] Next, the image processing unit 3 differentiates, as described in step S17 of Fig. Figure 9 shows the standard deviation σ and a threshold of the change Δσ of the standard deviation σ between the first layers 11 and the second layers 12. The image processing unit 3 calculates the thickness of each layer from the boundary of each layer.

[0059] For example, a method for determining the laminate state using the standard deviation σ is described. As in Fig. As shown in Figure 14, a threshold SH1 of the standard deviation σ is set. Then the standard deviation σ at depths D1, D2, D3, and D4 is less than or equal to the threshold SH1. Except for depths D1, D2, D3, and D4, the standard deviation σ is greater than the threshold SH1.

[0060] Here, if the standard deviation σ ≤ the threshold SH1, the layer is determined to be the circumferentially wound second layer 12, whereas if the standard deviation σ > the threshold SH1, the layer is determined to be the spirally wound first layer 11. In this example, the layers at depths D1, D2, D3, and D4 of the CFRP laminate 10 can be determined to be the circumferentially wound second layers 12. The layers other than those at depths D1, D2, D3, and D4 of the CFRP laminate 10 can be determined to be the spirally wound first layers 11.

[0061] The following describes a procedure for determining the laminate condition using the change Δσ of the standard deviation σ. For example, the thresholds of the change Δσ are set to (-SH2) and (+SH2). Then, at each of the depths D5 to D10, the change Δσ is (-SH2) ≤ Δσ ≤ (+SH2). Conversely, at positions other than depths D5 to D10, the change Δσ is < (-SH2) or (+SH2) < the change Δα.

[0062] Here, if (-SH2) ≤ change Δσ ≤ (+SH2), the layer is determined to be the circumferentially wound second layer 12, whereas if change Δσ < (-SH2) or (+SH2) < change Δσ, the layer is determined to be the helically wound first layer 11. In this example, the layers at depths D5 to D10 of the CFRP laminate 10 are determined to be the helically wound second layers 12. However, since the layers at depth D6 and the like, which are determined to be the circumferentially wound layers, are located at the depth at which the layer is to be determined to be the helically wound layer, it can be difficult to determine the layer to be the helically wound layer solely by the change Δσ.

[0063] In principle, the value of the standard deviation σ is stable in the circumferentially wound layer. On the other hand, the value of the standard deviation σ can be unstable in the spirally wound layer. This is because the rate of change Δσ changes significantly at the boundary where the layer transitions from the spirally wound layer to the circumferentially wound layer, or vice versa. Therefore, it is preferable to determine the circumferentially wound second layer 12 using the standard deviation σ, and to supplement the determination of the spirally wound first layer 11 using the rate of change Δσ.

[0064] The following equations are algorithms that show examples of the procedure for distinguishing between circumferential winding and spiral winding using the standard deviation σ and the amount of change Δσ of the standard deviation σ.

[0065] Assuming that a determination value of the standard deviation σ is defined as a, a = 0 if the standard deviation σ is less than or equal to the threshold, whereas a = 1 if the standard deviation σ is greater than the threshold. If the determination value of the change Δσ is defined as b, b = 0 if the change Δσ falls within the range of the threshold, whereas b = 1 if the change Δσ lies outside the range of the threshold. If equation (1) holds, the layer is determined to be the circumferentially wound layer. If equation (2) holds, the layer is determined to be the spirally wound layer. a+b≤0 a+b≥1

[0066] According to equation (1), if both the determination using the standard deviation σ and the determination using the change Δσ indicate circumferential winding, the layer is determined to be the circumferentially wound layer. According to equation (2), if the determination using the standard deviation σ and / or the determination using the change Δσ indicate helical winding, the layer is determined to be the helically wound layer.

[0067] In this embodiment, as described above, a parameter is calculated from the plurality of acquired images, which correlates with the number of cavities formed in the first layers 11 and the second layers 12, and the first layer 11 and the second layer 12 are distinguished from each other using the calculated parameter. If the cavities extending in the first direction are defined as the first cavities and the cavities extending in the second direction are defined as the second cavities, the parameter can correspond to the standard deviation σ of the luminance of the region containing the first cavities in the plurality of images or to the change Δσ of the standard deviation σ of the luminance. For example, the first cavities extend in the spiral direction and the second cavities extend in the circumferential direction.

[0068] The effect of this embodiment is described below. In the laminate condition calculation method according to this embodiment, the orientation direction of the carbon fibers is determined using the parameter that correlates with the number of voids. In this way, a resolution sufficient to confirm the orientation of the carbon fibers is not required. Thus, the laminate condition of the CFRP laminate 10 can be determined simply and cost-effectively.

[0069] Since the imaging unit uses two X-rays, the laminate condition can be determined non-destructively. Furthermore, the laminate condition is determined by eliminating the influence of the cavities extending in the circumferential direction H2 using the parameter correlated with the cavities extending in the spiral direction H1. Because the laminate condition can be determined using a single parameter correlated with the cavities extending in the spiral direction H1 and the parameter correlated with the cavities extending in the circumferential direction H2, the accuracy of the laminate condition determination can be improved.Furthermore, if the number of cavities extending in the spiral direction H1 is greater than the number of cavities extending in the circumferential direction H2, it is possible to determine the laminate condition using the parameter that correlates with the number of cavities extending in the spiral direction H1, and vice versa. This allows for further improvement in the accuracy of determining the laminate condition.

[0070] Although this embodiment has been described above, the present invention is not limited to the above embodiment and can be suitably modified without deviating from the basic concept and scope of protection of the invention. The following laminate state calculation program, for causing a computer to execute the laminate state calculation method according to this embodiment, is also within the scope of protection of the technical idea of ​​this embodiment.

[0071] That is, the laminate condition calculation program for a carbon fiber reinforced plastic laminate causes a computer to execute the following: Obtaining a plurality of images of a cross-section of the laminate orthogonal to a lamination direction by imaging the laminate with X-rays at a plurality of different positions in the lamination direction, wherein the laminate comprises first layers of carbon fibers oriented in a first direction orthogonal to the lamination direction, and second layers of carbon fibers oriented in a second direction which is orthogonal to the lamination direction and differs from the first direction, wherein the first layers and the second layers are laminated alternately; and Calculating a parameter correlated with the number of cavities formed in the first and second layers from the majority of obtained images, and distinguishing between the first and second layers using the calculated parameter.

[0072] The foregoing program can be stored and made available to a computer using any type of non-transitory computer-readable media. Non-transitory computer-readable media includes all types of physical storage media. Examples of non-transitory computer-readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), magnetic optical storage media (such as magneto-optical disks), CD-ROM (read-only memory), CD-R, CD-R / W, and semiconductor memory (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.).

[0073] The program can be delivered to a computer using any type of transient, computer-readable media. Examples of transient, computer-readable media include electrical signals, optical signals, and electromagnetic waves. Transient computer-readable media can deliver the program to a computer via a wired communication link (such as electrical wires and optical fibers) or a wireless communication link.

[0074] It is evident from the invention described above that the embodiments of the invention can be varied in many respects. Such variations are not to be considered a deviation from the basic concept and scope of protection of the invention, and all such modifications, which are apparent to a person skilled in the art, are to be included within the scope of protection of the following claims.< / laminatzustandsberechnungsverfahren> < / laminatzustandsberechnungsvorrichtung> < / laminat>

Claims

[1] Laminate state calculation method of a carbon fiber reinforced plastic laminate (10) wherein the method comprises: Obtaining a plurality of images of a cross-section (15) of the laminate (10) orthogonal to a lamination direction (P) by imaging the laminate (10) with X-rays at a plurality of different positions in the lamination direction (P), wherein the laminate (10) comprises first layers (11) with carbon fibers oriented in a first direction orthogonal to the lamination direction (P) and second layers (12) with carbon fibers oriented in a second direction which is orthogonal to the lamination direction (P) and differs from the first direction, wherein the first layers (11) and the second layers (12) are laminated alternately; Calculating a parameter correlated with the number of cavities formed in the first layers (11) and the second layers (12) from the majority of obtained images, and distinguishing between the first layers (11) and the second layers (12) using the calculated parameter; and Eliminating the influence of second cavities from an area containing first cavities in the majority of obtained images, where the cavities extending in the first direction are defined as the first cavities and the cavities extending in the second direction are defined as the second cavities; where the parameter of a standard deviation (σ) corresponds to a luminance of a region containing the first cavities in the majority of images. [2] Laminate state calculation method of a carbon fiber reinforced plastic laminate (10), wherein the method comprises: Obtaining a plurality of images of a cross-section (15) of the laminate (10) orthogonal to a lamination direction (P) by imaging the laminate (10) with X-rays at a plurality of different positions in the lamination direction (P), wherein the laminate (10) comprises first layers (11) with carbon fibers oriented in a first direction orthogonal to the lamination direction (P) and second layers (12) with carbon fibers oriented in a second direction which is orthogonal to the lamination direction (P) and differs from the first direction, wherein the first layers (11) and the second layers (12) are laminated alternately; Calculating a parameter correlated with the number of cavities formed in the first layers (11) and the second layers (12) from the majority of obtained images, and distinguishing between the first layers (11) and the second layers (12) using the calculated parameter; and Eliminating the influence of second cavities from an area with first cavities in the majority of obtained images, where the cavities extending in the first direction are defined as the first cavities and the cavities extending in the second direction are defined as the second cavities. where the parameter corresponds to the amount of change of a standard deviation (σ) of a luminance of a region containing the first cavities in the majority of images. [3] Method according to claim 1 or 2, wherein the elimination of the influence of the second cavities comprises: Converting the image into a power spectrum using a fast Fourier transform; Removing a spectrum of the second cavities from the converted power spectrum; and Converting the power spectrum, from which the spectrum of the second cavities has been removed, into the image by means of an inverse fast Fourier transform. [4] Method according to any one of claims 1 to 3, wherein the laminate (10) has a cylindrical shape with a central axis (C), and The lamination direction (P) corresponds to a direction orthogonal to the central axis (C). [5] Method according to claim 4, wherein the second direction corresponds to a direction of rotation about the central axis (C) and the first direction corresponds to a direction inclined to the second direction. [6] Laminate condition calculation device (1) for a carbon fiber reinforced plastic laminate (10), comprising: an imaging unit (2) configured to obtain a plurality of images of a cross-section (15) of the laminate (10) orthogonal to a lamination direction (P) by imaging the laminate (10) with X-rays at a plurality of different positions in the lamination direction (P), wherein the laminate (10) comprises first layers (11) with carbon fibers oriented in a first direction orthogonal to the lamination direction (P), and second layers (12) with carbon fibers oriented in a second direction which is orthogonal to the lamination direction (P) and differs from the first direction, wherein the first layers (11) and the second layers (12) are laminated alternately; and an image processing unit (3) which is configured to calculate a parameter, which is correlated with a number of cavities formed in the first layers (11) and the second layers (12), from the majority of obtained images, and to distinguish between the first layers (11) and the second layers (12) using the calculated parameter, wherein the image processing unit (3) is configured such that it eliminates the influence of second cavities from an area with first cavities in the majority of acquired images, if the cavities extending in the first direction are defined as the first cavities and the cavities extending in the second direction are defined as the second cavities, and where the parameter of a standard deviation (σ) corresponds to a luminance of a region containing the first cavities in the majority of images. [7] Laminate condition calculation device (1) for a carbon fiber reinforced plastic laminate (10), comprising: an imaging unit (2) configured to obtain a plurality of images of a cross-section (15) of the laminate (10) orthogonal to a lamination direction (P) by imaging the laminate (10) with X-rays at a plurality of different positions in the lamination direction (P), wherein the laminate comprises first layers (11) with carbon fibers oriented in a first direction orthogonal to the lamination direction (P), and second layers (12) with carbon fibers oriented in a second direction which is orthogonal to the lamination direction (P) and differs from the first direction, wherein the first layers (11) and the second layers (12) are laminated alternately; and an image processing unit (3) which is configured to calculate a parameter, which is correlated with a number of cavities formed in the first layers (11) and the second layers (12), from the majority of obtained images, and to distinguish between the first layers (11) and the second layers (12) using the calculated parameter, wherein the image processing unit (3) is configured such that it eliminates the influence of second cavities from an area with first cavities in the majority of acquired images, if the cavities extending in the first direction are defined as the first cavities and the cavities extending in the second direction are defined as the second cavities, and where the parameter corresponds to the amount of change of a standard deviation (σ) of a luminance of a region containing the first cavities in the majority of images. [8] Laminate condition calculation device according to claim 6 or 7, wherein, when the image processing unit (3) eliminates the influence of the second cavities, the image processing unit (3) is configured such that it converts the image into a power spectrum by means of a fast Fourier transform; the image processing unit (3) is configured such that it removes a spectrum of the second cavities from the converted power spectrum; and the image processing unit (3) is configured such that it converts the power spectrum from which the spectrum of the second cavities is removed into the image by means of an inverse fast Fourier transform. [9] Laminate condition calculation device according to one of claims 6 to 8, wherein the laminate (10) has a cylindrical shape with a central axis (C), and The lamination direction (P) corresponds to a direction orthogonal to the central axis (C). [10] Laminate condition calculation device according to claim 9, wherein the second direction corresponds to a direction of rotation about the central axis (C) and the first direction corresponds to a direction inclined to the second direction. [11] Laminate state calculation program for a carbon fiber reinforced plastic laminate (10) which causes a computer to execute the following: Obtaining a plurality of images of a cross-section (15) of the laminate (10) orthogonal to a lamination direction (P) by imaging the laminate (10) with X-rays at a plurality of different positions in the lamination direction (P), wherein the laminate (10) comprises first layers (11) with carbon fibers oriented in a first direction orthogonal to the lamination direction (P) and second layers (12) with carbon fibers oriented in a second direction which is orthogonal to the lamination direction (P) and differs from the first direction, wherein the first layers (11) and the second layers (12) are laminated alternately; Calculating a parameter correlated with the number of cavities formed in the first layers (11) and the second layers (12) from the majority of obtained images, and distinguishing between the first layers (11) and the second layers (12) using the calculated parameter; and Eliminating the influence of second cavities from an area with first cavities in the majority of obtained images, where the cavities extending in the first direction are defined as the first cavities and the cavities extending in the second direction are defined as the second cavities. where the parameter of a standard deviation (σ) corresponds to a luminance of a region containing the first cavities in the majority of images. [12] Laminate state calculation program for a carbon fiber reinforced plastic laminate (10) which causes a computer to execute the following: Obtaining a plurality of images of a cross-section (15) of the laminate (10) orthogonal to a lamination direction (P) by imaging the laminate (10) with X-rays at a plurality of different positions in the lamination direction (P), wherein the laminate (10) comprises first layers (11) with carbon fibers oriented in a first direction orthogonal to the lamination direction (P) and second layers (12) with carbon fibers oriented in a second direction which is orthogonal to the lamination direction (P) and differs from the first direction, wherein the first layers (11) and the second layers (12) are laminated alternately; Calculating a parameter correlated with the number of cavities formed in the first layers (11) and the second layers (12) from the majority of obtained images, and distinguishing between the first layers (11) and the second layers (12) using the calculated parameter; and Eliminating the influence of second cavities from an area with first cavities in the majority of obtained images, where the cavities extending in the first direction are defined as the first cavities and the cavities extending in the second direction are defined as the second cavities. where the parameter corresponds to the amount of change of a standard deviation (σ) of a luminance of a region containing the first cavities in the majority of images. [13] Laminate condition calculation program according to claim 11 or 12, wherein, when the computer is caused to eliminate the influence of the second cavities, the computer is further caused to execute the following: Converting the image into a power spectrum using a fast Fourier transform; Removing a spectrum of the second cavities from the converted power spectrum; and Converting the power spectrum, from which the spectrum of the second cavities has been removed, into the image by means of an inverse fast Fourier transform. [14] Laminate condition calculation program according to one of claims 11 to 13, wherein the laminate (10) has a cylindrical shape with a central axis (C), and The lamination direction (P) corresponds to a direction orthogonal to the central axis (C).

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