JP2020169852A - Fiber orientation distribution measuring method and fiber orientation distribution measuring system - Google Patents

Abstract

To provide a fiber orientation distribution measuring method and a fiber orientation distribution measuring system capable of dimensionally measuring the orientation distribution.SOLUTION: A fiber orientation distribution measuring method includes: a scattered X-ray acquisition step S1 of acquiring scattered X-rays by a small angle X-ray scattering device; and an acquisition step S2 of calculating the scattering intensity of scattered X-rays in three dimensions and obtaining a relationship between an azimuth angle φ' and the scattering intensity after the scattered X-ray acquisition step S1. Further, the fiber orientation distribution measuring method includes the orientation distribution calculating step S3 of calculating the orientation distribution of the reinforcing fibers in a fiber reinforced composite material from the relationship between the azimuth angle φ' acquired in the acquisition step S2 and the scattering intensity.SELECTED DRAWING: Figure 7

Description

The present invention relates to a fiber orientation distribution measuring method and a fiber orientation distribution measuring system.

Fiber reinforced composites are used as lightweight and high-strength materials. The fiber-reinforced composite material has a structure because the mechanical properties (mechanical properties) are improved as compared with the matrix material itself by combining the reinforcing fibers (reinforced base material) in the matrix material such as resin and ceramics. Preferable as a part. In such a fiber-reinforced composite material, the orientation state of the reinforcing fibers has a great influence on the mechanical properties. Therefore, in the fiber-reinforced composite material, it is important to grasp the orientation distribution of the reinforcing fibers. For example, the fiber orientation calculation device disclosed in Patent Document 1 includes a profile acquisition unit, which is around the center of a circular diffraction image generated by irradiating a fiber-reinforced composite material with X-rays. Obtain a profile showing the relationship between the angle and the diffraction intensity of the diffraction image. Further, the fiber orientation degree calculation device includes a crystal orientation degree calculation unit, and the crystal orientation degree calculation unit calculates the crystal orientation degree based on the acquired profile. The profile acquisition unit acquires a profile of the fiber composite material in which the reinforcing fibers are aligned in one direction. The crystal orientation calculation unit calculates the crystal orientation of the fiber-reinforced composite material based on the acquired profile. The fiber orientation calculation unit of the fiber orientation calculation device calculates the fiber orientation of the fiber composite material based on the crystal orientation.

Japanese Unexamined Patent Publication No. 2016-90259

However, the fiber orientation calculation device of Patent Document 1 can only calculate the two-dimensional fiber orientation distribution of the fiber-reinforced composite material.
An object of the present invention is to provide a fiber orientation distribution measuring method and a fiber orientation distribution measuring system capable of three-dimensionally measuring an orientation distribution.

The fiber orientation distribution measuring method for solving the above problem detects the scattered X-rays having a small scattering angle among the X-rays scattered by irradiation of the fiber-reinforced composite material containing the reinforcing fibers with X-rays, and the fiber-reinforced composite. A fiber orientation distribution measuring method for measuring the orientation distribution of the reinforcing fibers in a material, wherein the scattering X-ray acquisition step of acquiring the scattered X-rays and one axis orthogonal to the orientation axis of the reinforcing fibers are the x-axis. The origin is the intersection of the x-axis and the alignment axis, the azimuth angle with respect to the alignment axis is φ, the angle around the alignment axis is α, and the orientation axis is about the point at a distance s from the origin. The azimuth angle at a position deviated by an angle α is set to φ', and the scattering intensity of the scattered X-rays in three dimensions is calculated from the following (Equation 1), which is performed after the scattered X-ray acquisition step. An acquisition step for acquiring the relationship between the angle φ'and the scattering intensity, and an orientation distribution calculation step for calculating the orientation distribution of the reinforcing fibers in the fiber-reinforced composite material from the acquired relationship performed after the acquisition step. , Is included in the gist.

According to this, by using (Equation 1) in the acquisition step after the scattered X-ray acquisition step, the scattering intensity of the scattered X-rays obtained by small-angle X-ray scattering can be calculated in three dimensions, and the scattering intensity can be calculated. The relationship between and the azimuth angle φ'can be obtained. Therefore, by using (Equation 1), the orientation distribution of the reinforcing fibers can be grasped three-dimensionally. Then, by calculating the orientation distribution in the orientation distribution calculation step, the orientation distribution of the reinforcing fibers can be measured three-dimensionally in the fiber-reinforced composite material.

Regarding the fiber orientation distribution measurement method, in the acquisition step, a profile showing the relationship between the azimuth φ'and the scattering intensity was acquired, and in the orientation distribution calculation step, the azimuth φ'was different. A plurality of profiles may be created, a calibration curve showing the relationship between the amount of increase in the peak width of each profile and the orientation distribution may be created, and the orientation distribution may be calculated from the calibration curve.

According to this, the orientation distribution can be quickly obtained by creating a calibration curve in the orientation distribution calculation step. If the peak width increases significantly and the amount of increase cannot be defined, the orientation distribution of the reinforcing fibers corresponds to non-orientation.

The fiber orientation distribution measurement system for solving the above problems is a small-angle X-ray scattering device that detects scattered X-rays having a small scattering angle among the X-rays scattered by irradiation of a fiber-reinforced composite material containing reinforcing fibers with X-rays. The x-axis is one axis orthogonal to the orientation axis of the reinforcing fiber, the intersection of the x-axis and the alignment axis is the origin, and the azimuth angle with respect to the orientation axis is φ at a point located at a distance s from the origin. When the angle around the alignment axis is α and the azimuth angle at a position deviated by the angle α around the alignment axis is φ', 3 of the scattered X-rays acquired from the small-angle X-ray scattering device. The scattering intensity in the dimension is calculated from the following (Equation 1), the profile acquisition unit that acquires the profile showing the relationship between the azimuth angle φ'and the scattering intensity, and the peak width of the acquired profile are measured. , A profile calculation unit that creates a plurality of the profiles having different azimuth angles φ'and creates a calibration line showing the relationship between the increase amount of the peak width of each profile and the orientation distribution, and the orientation distribution from the calibration line. It is a gist to have an orientation distribution calculation unit for calculating.

According to this, after the scattered X-rays are detected by the small-angle X-ray scattering device, the profile acquisition unit uses (Equation 1) to scatter the scattered X-rays obtained by the small-angle X-ray scattering in three dimensions. Can be calculated, and the profile can be obtained from the scattering intensity. Therefore, by using (Equation 1), it is possible to obtain a profile that captures the orientation distribution of the reinforcing fibers in three dimensions. Then, the orientation distribution of the reinforcing fibers can be measured three-dimensionally by creating a calibration curve by the profile calculation unit and calculating the orientation distribution using the calibration curve by the orientation distribution calculation unit.

Further, the fiber orientation distribution measurement system may include a display unit that displays the orientation distribution calculated by the orientation distribution calculation unit.
According to this, the orientation distribution can be confirmed on the display unit.

According to the present invention, the orientation distribution can be measured three-dimensionally.

The figure which shows typically the fiber orientation distribution measurement system. The figure which shows typically the small angle X-ray scattering apparatus. The figure for demonstrating polar coordinates. The figure for demonstrating the minute area. (A) is a diagram schematically showing perfectly oriented carbon fibers, (b) is a diagram schematically showing a scattering pattern, and (c) is a graph showing an azimuth angle and scattering intensity. (A) is a diagram schematically showing oriented carbon fibers, (b) is a diagram schematically showing a scattering pattern, and (c) is a graph showing an azimuth angle and scattering intensity. The flowchart which shows the fiber orientation distribution measurement method.

Hereinafter, an embodiment in which the fiber orientation distribution measuring method and the fiber orientation distribution measuring system are embodied will be described with reference to FIGS. 1 to 7.
As shown in FIG. 1, the fiber orientation distribution measuring system 100 includes a small-angle X-ray scattering device 10, a measuring unit 20 for measuring the fiber orientation distribution, and a display unit 30 for displaying the measurement result by the measuring unit 20. ..

As shown in FIG. 2, the small-angle X-ray scattering device 10 irradiates the fiber-reinforced composite material H as an evaluation target with X-rays and scatters X-rays having a small scattering angle (hereinafter referred to as scattered X-rays). ) Is a device that detects. The small-angle X-ray scattering device 10 includes an X-ray irradiation unit 11 and a detection unit 12 for detecting scattered X-rays. The small scattering angle means that the scattering angle is 5 degrees or less. Since FIG. 2 schematically shows the small-angle X-ray scattering device 10, the scattering angle is larger than 5 degrees. Further, the distance L from the fiber-reinforced composite material H to the detection unit 12 changes according to the thickness of the fiber-reinforced composite material H.

In FIG. 1, the measuring unit 20 includes a CPU (not shown) and a storage unit including a RAM, a ROM, and the like. The CPU and the storage unit are signal-connected. A program or the like for measuring the orientation distribution of fibers is stored in the storage unit. The CPU may be provided with dedicated hardware that executes at least a part of the various processes, for example, an integrated circuit for a specific application: ASIC. The CPU may be configured as one or more processors operating according to a computer program, one or more dedicated hardware circuits such as an ASIC, or a circuit including a combination thereof. The processor includes a CPU and memories such as RAM and ROM. The memory stores a program code or a command configured to cause the CPU to execute the process. Memory, or computer-readable medium, includes anything that can be accessed by a general purpose or dedicated computer. Then, the CPU of the measurement unit 20 functions as a profile acquisition unit 21, a profile calculation unit 22, and an orientation distribution calculation unit 23.

The fiber-reinforced composite material H whose orientation distribution is measured is formed by impregnating a reinforcing base material made of reinforcing fibers with a matrix material. Although not shown, the reinforcing base material of the fiber-reinforced composite material H is formed by arranging threads at an arbitrary angle and laminating them in an arbitrary number of layers. The reinforcing base material may be formed, for example, by weaving a first thread and a second thread in a plain weave, a twill weave, or a satin weave. Further, the reinforced base material may be formed by laminating a plurality of single-layer woven fabrics and bonding them with binding threads in the laminating direction, or may be formed by multi-layer weaving.

The fiber orientation distribution measuring system 100 measures the orientation distribution of the reinforcing fibers in the fiber-reinforced composite material H. The reinforcing fiber whose orientation distribution can be measured may be a fiber material in which the pattern of scattered X-rays detected by the small-angle X-ray scattering device 10 causes streaks extending in the horizontal direction across a central circle.

Examples of such fiber materials include PAN-based carbon fibers having a nanovoid structure, anisotropic carbon fibers such as Pitch-based carbon fibers, and organic fibers having a nanovoid or fibril structure (polyester, nylon, Kevlar®, Zyrone, etc.). Polyarylate fiber, aramid fiber), ceramic fiber (silicon carbide fiber) can be mentioned. Examples thereof include glass whiskers, carbon nanofibers, carbon nanotubes, alumina whiskers, and silicon carbide whiskers. These fiber materials may be long fibers, short fibers, or milled fibers.

Next, a fiber orientation distribution measuring method using the fiber orientation distribution measuring system 100 will be described. In the present embodiment, the fiber orientation distribution of the fiber-reinforced composite material H using carbon fibers as reinforcing fibers is measured.

As shown in FIG. 7, the fiber orientation distribution measuring method is performed after the scattered X-ray acquisition step S1 for acquiring scattered X-rays generated by small-angle X-ray scattering and the scattered X-ray acquisition step S1 and the orientation of the scattered X-rays. It includes an acquisition step S2 for acquiring the relationship between the angle and the scattering intensity, and an orientation distribution calculation step S3 performed after the acquisition step S2 for calculating the orientation distribution of carbon fibers based on the acquired relationship.

When the carbon fibers are irradiated with X-rays using the small angle X-ray scattering device 10 in the scattered X-ray acquisition step S1, streaks in the direction orthogonal to the fiber axis direction are reflected, reflecting the nanovoids extending in the fiber axis direction of the carbon fibers. A scattering pattern is obtained.

In the acquisition step S2, the scattering pattern is measured. In measuring this scattering pattern, consider the reciprocal space obtained by the square of the absolute value of the Fourier transform of the electron density distribution of carbon fibers, and consider the pattern crossed by the Ewald reflective sphere. Since the small-angle X-ray scattering has a small scattering angle, the reflected sphere of Ewald is approximated by a plane. Therefore, the cut surface on the plane passing through the origin in the reciprocal space gives a scattering pattern of small-angle X-rays. As a result, in the case of carbon fibers, the scattering pattern reflects the nanovoids and in the reciprocal space it becomes a cylindrical object whose axial direction coincides with the normal direction.

As shown in FIG. 3, the polar coordinates of the scattering pattern in the reciprocal space are (s, φ). In setting the polar coordinates, one axis orthogonal to the alignment axis z of the carbon fiber is defined as the x-axis, and the point where the orientation axis z and the x-axis are orthogonal to each other is defined as the origin O. Then, s is the distance from the origin O, and φ is the azimuth angle from the orientation axis z.

The scattering intensity I (s) in this polar coordinate is represented by the following (Equation 2).

The scattering intensity I (s) is the case where there is only one carbon fiber. Here, since the fiber-reinforced composite material H has a three-dimensional orientation distribution, the three-dimensional orientation distribution is also taken into consideration. Let the three-dimensional orientation distribution function be f (φ', α). Assuming that the azimuth angle at a position deviated by an angle α about the orientation axis z with respect to the polar coordinates is φ', the scattering intensity I considering the three-dimensional orientation distribution is expressed by the following (Equation 1).

The above (Equation 2) is represented by the following (Equation 3) using trigonometric functions.

Further, in the above (Equation 1), the portion represented by the following (Equation 4) is a minute area formed on the reflection sphere of Ewald as shown in FIG. This minute area is calculated by the product of one side sinφ'dα and the other side dα intersecting the one side. Then, in the above (Equation 1), the orientation distribution of the carbon fibers in the three-dimensional direction is added by integrating this minute area as well.

Therefore, in (Equation 1), the scattering intensity I (φ) in consideration of the three-dimensional orientation distribution can be calculated from the three-dimensional orientation distribution function f (φ', α) and the minute area.

In the acquisition step S2, the profile acquisition unit 21 of the measurement unit 20 calculates the scattering intensity I (φ) from (Equation 1) and acquires a profile based on the scattering pattern from the calculated scattering intensity I (φ).

As shown in FIG. 5A, when the carbon fibers are aligned on the orientation axis z, the scattering pattern detected by the detection unit 12 sandwiches the central circle as shown in FIG. 5B. A streak P extending in the horizontal direction will be generated. When this scattering pattern is a profile in which the horizontal axis is the azimuth and the vertical axis is the scattering intensity, the profile is as shown in FIG. 5 (c). The azimuth is 0 ° to 180 °. As shown in FIG. 5C, in the profile when the carbon fibers are aligned on the orientation axis z, it is shown that the peak width W is narrow and the orientation distribution is small. That is, it is shown that the carbon fibers are concentrated in the vicinity of the azimuth angle φ of 90 °.

As shown in FIG. 6A, when there is an orientation distribution with respect to the orientation axis z, as shown in FIG. 6B, the scattering pattern is such that a streak P extending in the vertical direction is generated in addition to the horizontal direction. become. In FIG. 6C, the profile when the carbon fibers are aligned on the alignment axis z is shown by a chain line, and the profile when the carbon fibers are aligned with respect to the alignment axis z is shown by a solid line. When there is an orientation distribution with respect to the orientation axis z, the scattering intensity I has a wider range of the azimuth angle φ and a wider peak width W. From this, it is shown that the orientation distribution becomes large.

When there is an orientation distribution with respect to the orientation axis z, the spread of the peak width W of the profile does not simply spread by the amount of the orientation distribution, but is the same as the peak width W when the carbon fibers are aligned with the orientation axis z. , It depends on the peak width W when there is an orientation distribution. Therefore, the scattering intensity I at several azimuth angles φ'is calculated in advance from the predicted orientation distribution function, for example, the normal distribution function, and a plurality of standard deviations σ representing the spread of the peak width W of the profile are calculated, and the peak width is calculated. Create a calibration line showing the relationship between the spread of W and the actual orientation distribution.

The calibration curve is created by the profile calculation unit 22. The profile calculation unit 22 measures the peak width W of the acquired profile, creates a plurality of profiles having different azimuth angles φ', and determines the relationship between the increase amount of the peak width W of each profile and the standard deviation σ. Create a calibration curve to represent.

First, the scattering intensity I (φ) is converted into (Equation 5) so that the spread of the orientation distribution can be converted by the standard deviation σ.

Note that in Equation _{(5), f σ (φ '} i, α j) , the orientation distribution function to be predicted, for example, a normal distribution function.

Then, the scattering intensity I (φ _k ) is calculated using (Equation 5).
Next, for the profile based on the calculated scattering intensity I (φ _k ), the peak width W is calculated by (Equation 6) using the integrated width. The peak width W may be calculated using the full width at half maximum.

Next, the amount of increase Δb _σ of the peak width W representing the spread of the peak width W is calculated based on (Equation 7). In (Equation 7), the increase amount Δb _σ of the peak width W is the peak width W (b ₀ ) in the profile of one carbon fiber in the perfect orientation from the peak width W (b _σ ) based on the calculated scattering intensity I. ) Is subtracted.

Then, an approximate equation is calculated using the power equation for the relationship between the increase amount Δb _σ of the peak width W and the standard deviation σ, and a calibration curve is created. In the orientation distribution calculation step S3, the standard deviation σ of the orientation distribution can be calculated by substituting the increase amount Δb _σ of the peak width W into the created calibration curve. The calculation of the standard deviation σ is performed by the orientation distribution calculation unit 23. In the orientation distribution, the smaller the value of the standard deviation σ, the smaller the variation in the three-dimensional orientation of the carbon fibers along the orientation axis z. The larger the value of the standard deviation σ, the greater the variation of the carbon fibers in the three-dimensional direction with respect to the orientation axis z. Then, the measuring unit 20 causes the display unit 30 to display the calculated standard deviation σ. In the acquired profile, when the peak width W increases significantly and the amount of increase cannot be defined, the orientation distribution of the carbon fibers corresponds to non-orientation.

According to the above embodiment, the following effects can be obtained.
(1) In the acquisition step S2, the profile acquisition unit 21 can calculate the three-dimensional scattering intensity of the scattered X-rays obtained by small-angle X-ray scattering by using (Equation 1), and acquire the profile from the scattering intensity. it can. Therefore, by using (Equation 1), it is possible to obtain a profile that captures the orientation distribution of carbon fibers in three dimensions. Then, the orientation distribution calculation unit 23 calculates the orientation distribution in the orientation distribution calculation step S3, so that the three-dimensional orientation distribution of the carbon fibers can be measured in the fiber-reinforced composite material H.

(2) In the orientation distribution calculation step S3, the orientation distribution calculation unit 23 creates a calibration curve and substitutes the increase amount of the integral width into the calibration curve to quickly obtain a three-dimensional orientation distribution of the carbon fibers. Can be done.

(3) The fiber orientation distribution measurement system 100 includes a display unit 30. Since the measuring unit 20 displays the orientation distribution on the display unit 30, the operator can easily confirm the orientation distribution.
(4) In the small-angle X-ray scattering device 10, the scattering pattern detected by the detection unit 12 depends on the distance L between the X-ray irradiation unit 11 and the detection unit 12, and is also affected by the thickness of the fiber-reinforced composite material H. .. In the case of wide-angle X-ray diffraction, if the thickness of the fiber-reinforced composite material H is large, the effect on the distance L is large and the accuracy tends to decrease. However, since small-angle X-ray scattering is used, the distance L is long and the fiber-reinforced composite The influence of the thickness of the material H is reduced, and more accurate evaluation of the orientation distribution becomes possible.

The embodiment can be modified and implemented as follows. The embodiments and the following modifications can be implemented in combination with each other to the extent that they are technically consistent.
○ The fiber orientation distribution measurement system 100 does not have to include the display unit 30. In this case, the measuring unit 20 may feed back the orientation distribution calculated by the orientation distribution calculation unit 23 to the apparatus for manufacturing the reinforcing base material in the fiber-reinforced composite material H. Then, the reinforcing base material manufacturing apparatus may adjust the orientation of the carbon fibers according to the feedback orientation distribution.

○ In the fiber orientation distribution measurement system 100, in the orientation distribution calculation step S3, the orientation distribution calculation unit 23 may calculate the orientation distribution without using a calibration curve. In this case, the orientation distribution is calculated by comparing the peak width W of the profile of the measured fiber-reinforced composite material H with the peak width W of the fully oriented profile.

○ In the orientation distribution calculation step S3, the orientation distribution may be calculated from the relationship between the scattering intensity calculated using (Equation 1) and the azimuth angle φ'without acquiring the profile in the acquisition step S2.
○ The two-dimensional orientation distribution function may be calculated by substituting the two-dimensional orientation distribution function into the orientation distribution function of (Equation 1).

Next, the technical idea that can be grasped from the above embodiment and another example will be added below.
(1) The reinforcing fiber is a carbon fiber.

H ... Fiber-reinforced composite material, 10 ... Small-angle X-ray scattering device, 21 ... Profile acquisition unit, 22 ... Profile calculation unit, 23 ... Orientation distribution calculation unit, 30 ... Display unit.

Claims (4)

Fiber orientation distribution for measuring the orientation distribution of the reinforcing fibers in the fiber-reinforced composite material by detecting scattered X-rays having a small scattering angle among the X-rays scattered by irradiation of the fiber-reinforced composite material containing the reinforcing fibers with X-rays. It ’s a measurement method,
The scattered X-ray acquisition step for acquiring the scattered X-rays and
One axis orthogonal to the orientation axis of the reinforcing fiber is the x-axis, the intersection of the x-axis and the alignment axis is the origin, and the azimuth angle with respect to the alignment axis is φ at a point located at a distance s from the origin, and the orientation. Let α be the angle around the axis, and φ'be the azimuth at the position where the angle α deviates around the alignment axis.
An acquisition step performed after the scattered X-ray acquisition step, in which the scattering intensity of the scattered X-rays in three dimensions is calculated from the following (Equation 1), and the relationship between the azimuth angle φ'and the scattering intensity is acquired. When,
A fiber orientation distribution measuring method, which is performed after the acquisition step and includes an orientation distribution calculation step of calculating the orientation distribution of the reinforcing fibers in the fiber-reinforced composite material from the acquired relationship.
In the acquisition step, profiles showing the relationship between the azimuth φ'and the scattering intensity are acquired, and in the orientation distribution calculation step, a plurality of the profiles having different azimuths φ'are created, and each profile The fiber orientation distribution measuring method according to claim 1, wherein a calibration curve showing the relationship between the amount of increase in the peak width and the orientation distribution is created, and the orientation distribution is calculated from the calibration curve. A small-angle X-ray scattering device that detects scattered X-rays with a small scattering angle among the X-rays scattered by irradiating a fiber-reinforced composite material containing reinforcing fibers with X-rays.
One axis orthogonal to the alignment axis of the reinforcing fiber is the x-axis, the intersection of the x-axis and the alignment axis is the origin, and the azimuth angle with respect to the alignment axis is φ for a point located at a distance s from the origin, and the alignment axis. When the angle around the is α, and the azimuth at a position deviated by the angle α around the orientation axis is φ',
The three-dimensional scattering intensity of the scattered X-rays acquired from the small-angle X-ray scattering device is calculated from the following (Equation 1), and a profile showing the relationship between the azimuth angle φ'and the scattering intensity is acquired. Profile acquisition department and
A profile that measures the acquired peak width of the profile, creates a plurality of the profiles with different azimuths φ', and creates a calibration curve showing the relationship between the increase in the peak width of each profile and the orientation distribution. Calculation department and
A fiber orientation distribution measurement system comprising an orientation distribution calculation unit for calculating the orientation distribution from the calibration curve.
The fiber orientation distribution measurement system according to claim 3, further comprising a display unit that displays the orientation distribution calculated by the orientation distribution calculation unit.