JPH07225222A - Fiber break detection method for carbon fiber reinforced plastic tube - Google Patents

Abstract

PURPOSE:To provide a method for detecting fiber break by using a rectangular excitation coil for making induction current selectively flow in each direction of the reinforced fiber of carbon fabric reinforced plastic tube. CONSTITUTION:Due to an excitation coil 10a wound around the periphery of CFRP (carbon fiber reinforced plastic) tube l. alternating field H takes place in the direction of tube's axis, and thanks to the magnetic field H, induction current i flaws in the axis direction of the tube 1. Diamagnetic field h takes place based on the induction current i, so, the impedance of a detection coil 10b changes. The detection coil 10b is wound along the inside of the excitation coil 10a. Since, in a carbon fiber reinforced plastic, the electric resistance in the direction of carbon fiber is lower than in perpendicular direction by about three digits, the induction current selectively flows in the fiber direction of 0 deg. direction. Therefore, if fiber break exists in that direction, electric resistance will increase, with the result of decrease in the induction current i and Diamagnetic field h, so, from the impedance changes at the detection coil, fabric break is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting fiber breakage of a carbon fiber reinforced plastic tubular body such as a golf shaft or a fishing rod.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting fiber breakage of carbon fiber reinforced plastics (hereinafter referred to as CFRP), the conductivity of carbon fiber is used to detect fiber breakage from changes in electrical resistance and electromagnetic induction current. A method for detecting is introduced in the literature and the like.

However, none of them are practical techniques at the stage of being researched at the test piece level.

For example, in p203-205 of the published papers of the Japan Society of Mechanical Engineers Material Mechanics Lecture ('90 -11-28, 29 Toyohashi City), which has already been published, one-way reinforced CFRP is included.
An example has been reported in which a tensile test is performed while measuring the electrical resistance of the plate in the fiber axis direction, and fiber breakage is detected from changes in the electrical resistance.

However, in this method, the electrical resistance in the direction perpendicular to the fiber is higher by 3 to 4 orders of magnitude than that in the fiber direction. Breakage becomes difficult to detect and cannot be used.

Further, it is necessary to apply a conductive paint to both end faces of the test piece to take out the lead wire, which is not suitable for product inspection.

[0007] In addition, p47 of the proceedings of the 4th non-destructive evaluation symposium of new materials and their products (January 1993)
-52 is unidirectionally reinforced CF with artificial fiber breaking scratches
An example in which an RP laminate and a 0 ° and 90 ° bidirectionally reinforced CFRP laminate are inspected by an electromagnetic induction test method (eddy current method) is reported.

However, in the unidirectional reinforcing material, the above-mentioned CFR is used.
It is described that the detection cannot be performed because the induced current is difficult to flow due to the electrical anisotropy of P.

Regarding the bidirectional reinforcing material, the anisotropy is alleviated, so that induced current can easily flow and can be detected, but the fiber breaking scratches are included in both the 0 ° layer and the 90 ° layer. It can be predicted from the result of the unidirectional strengthening that there is no sensitivity when only one of the layers is placed.

The problem with this method is that it is strongly affected by the anisotropy of electrical resistance because a spiral induced current is flowing in the plate surface, and it should be improved as a practical technique.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and provides a fiber breakage detection method capable of detecting fiber breakage of a CFRP tubular body with high sensitivity regardless of the fiber direction. With the goal.

[0012]

In order to solve the above problems, the present invention provides a method of detecting fiber breakage of a CFRP tubular body, wherein an exciting coil group for selectively passing an induced current is provided in each direction of reinforcing fibers. It is characterized in that the breakage of the reinforcing fiber is detected from the impedance change of the exciting coil or a detection coil paired with the exciting coil group is separately provided and the change of the impedance of the detecting coil is detected.

[0013]

The present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing an embodiment of the present invention. A CFRP tubular body 1 (for example, a golf shaft or a fishing rod) laminated with four types of prepregs having fiber directions of 0 °, ± 45 °, and 90 ° penetrates the cylindrical bobbins 2, 3, 4, and 5, respectively. Run.

On the outer peripheral surface of the cylindrical bobbin, 0 °, 90 °
Exciting coils 9a, 10a, 11 for selectively flowing an induced current in the respective fiber directions of °, +45 °, and -45 °
a and 12a are arranged, and detection coils 9b, 10b, 11b and 12b are arranged on the inner peripheral surface of the cylindrical bobbin.

The axial direction of the tube is 0 ° and the circumferential direction is 90 °. The exciting coils are connected to four-channel high-frequency power sources 6 whose frequencies can be changed for each channel, and the detection coils are connected to an impedance measuring device 7, respectively.

The impedance measuring device 7 converts the impedance change into a voltage and outputs the voltage, and the recorder 8 records the voltage.

Next, the means for detecting the breakage of the reinforcing fiber with the configuration of FIG. 1 will be described with reference to FIGS.

2 to 3 are explanatory views for detecting the breakage of the fiber in the 90 ° direction, and an alternating magnetic field H in the tube radial direction is generated by the rectangular exciting coil 9a arranged on the outer periphery of the CFRP tubular body 1. Then, due to the magnetic field H, an induced current i flows in the circumferential direction in the tubular body 1 as shown in FIG.

A demagnetizing field h is generated by this induced current i,
The impedance of the detection coil 9b shown in FIG. 3 changes.

The detection coil 9b is arranged between the exciting coil 9a and the tubular body 1 and is a rectangular coil. For the purpose of reducing noise and improving sensitivity, the detection coil 9b should be a differential coil as shown in the figure. Is desirable.

In the CFRP prepreg, the electric resistance in the fiber direction is smaller by about three orders of magnitude than that in the perpendicular direction, so that the induced current selectively flows in the prepreg having the fiber direction of 90 °.

Therefore, if there is a break in the fiber in this direction, the electrical resistance increases, the induced current i decreases, the demagnetizing field h decreases, and the break of the fiber can be detected from the impedance change of the detection coil.

FIGS. 4 to 5 are explanatory views for detecting the breakage of the fiber in the 0 ° direction. The rectangular exciting coil 10a arranged on the outer peripheral surface of the CFRP tubular body 1 causes an alternating magnetic field H in the radial direction of the tube. The generated magnetic field H causes an induced current i to flow in the tubular body 1 in the tube axis direction as shown in FIG.

A demagnetizing field h is generated by this induced current i,
The impedance of the detection coil 10b shown in FIG. 5 changes.

The detection coil 10b is arranged between the exciting coil 10a and the tubular body 1 and is a rectangular differential coil. For the reason described above, the induced current i in this case selectively flows in the prepreg in which the fiber direction is 0 °, and the fiber breakage in the same direction is detected with high sensitivity from the impedance change of the detection coil.

When detecting the breakage of the fiber in the ± 45 ° direction, the same rectangular exciting coil and detecting coil as shown in FIGS. 4 to 5 are arranged in the ± 45 ° direction on the outer peripheral surface of the CFRP tubular body. do it.

A coil in which the outer circumference of the CFRP tubular body is wound by 360 ° is also effective in selectively passing an induced current through the fibers in the 90 ° direction. The rectangular coil along the fiber direction is more effective than the coil obtained by winding the outer circumference of the CFRP tubular body through 360 ° in order to selectively flow the induced current to the fiber reinforced in the + 80 ° to -80 ° direction.

Although the above has described the operation relating to the method of claim 3, the method of claims 1 and 2 is the same since the exciting coil is also used as the detection coil. Also in this case, it is desirable that the exciting coil is of the differential type.

[0029]

EXAMPLE With the apparatus configuration of FIG. 1, two layers of prepregs having an outer diameter of 25 mm, a wall thickness of 1.4 mm, a length of 1000 mm, and a fiber direction of + 45 °, −45 °, 0 °, and 90 ° are arranged in this order from the inside. In a CFRP tubular body consisting of 8 layers each, 200 mm from the tip for a 90 ° prepreg, 400 mm for a 0 ° prepreg, and 6 for a -45 ° prepreg.
A test body in which artificial scratches having a length of 5 mm were inserted into the prepregs of 00 mm and + 45 ° at positions of 800 mm at right angles to the fiber direction was inspected.

6 to 9 show the inspection results, and FIGS. 6, 7, 8 and 9 show the voltage output proportional to the impedance change of each of the detection coils 9b, 10b, 11b and 12b.

From FIG. 6, the detection coil 9b detects the breakage of the fiber in the 90 ° direction with the highest sensitivity, and has a certain sensitivity to the breakage of the fiber in the ± 45 ° direction, but in the 0 ° direction. It can be seen that there is almost no sensitivity to fiber breakage.

The same can be said from FIGS. 7, 8 and 9. In other words, each detection coil can detect the breakage of the fiber in the direction in which the induced current selectively flows with the highest sensitivity, and the breakage of the fiber in the direction different by ± 45 ° with a certain sensitivity, but in the direction different by 90 °. It shows that there is almost no sensitivity to the breaking of the fiber.

From the above examples, it was confirmed that by selectively passing an induced current in each fiber direction, it is possible to detect with the same sensitivity without missing the breakage of the fiber in each direction.

[0034]

As described above, according to the present invention, an exciting coil group for selectively passing an induced current in each direction of the reinforcing fiber is provided, and the impedance change of the exciting coil group or the exciting coil group is paired with the exciting coil group. Since it is configured to measure the impedance change of the detection coil group that forms the, the fiber breakage of the CFRP tubular body having a plurality of fiber directions can be quantitatively and rapidly inspected regardless of the direction of the broken fiber.

Therefore, the present invention is very effective as a product inspection technique for CFRP golf shafts and fishing rods.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an apparatus configuration showing an embodiment of a method of the present invention.

FIG. 2 shows the shapes of the exciting coil and the detecting coil for detecting the breakage of the fiber in the 90 ° direction (circumferential direction) in the present invention,
FIG. 3 is an explanatory diagram showing the directions of induced currents generated in a material by the exciting coil.

FIG. 3 shows shapes of an exciting coil and a detecting coil for detecting breakage of a fiber in a 90 ° direction (circumferential direction) in the present invention,
FIG. 3 is an explanatory diagram showing the directions of induced currents generated in a material by the exciting coil.

FIG. 4 shows the shapes of an exciting coil and a detecting coil for detecting breakage of fibers in the 0 ° direction (tube axis direction) in the present invention,
FIG. 3 is an explanatory diagram showing the directions of induced currents generated in a material by the exciting coil.

FIG. 5 shows shapes of an exciting coil and a detecting coil for detecting fiber breakage in the 0 ° direction (tube axis direction) in the present invention,
FIG. 3 is an explanatory diagram showing the directions of induced currents generated in a material by the exciting coil.

FIG. 6 is a diagram showing an output voltage showing an example of a test result according to the present invention.

FIG. 7 is a diagram showing an output voltage showing an example of a test result according to the present invention.

FIG. 8 is a diagram showing an output voltage showing an example of a test result according to the present invention.

FIG. 9 is a diagram showing an output voltage showing an example of a test result according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CFRP tubular body 2 Coil bobbin 3 Coil bobbin 4 Coil bobbin 5 Coil bobbin 6 High frequency power source 7 Impedance measuring device 8 Recorder 9a Excitation coil 9b Detection coil 10a Excitation coil 10b Detection coil

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Aikawa 5-10-1 Fuchinobe, Sagamihara City Inside the Electronics Research Laboratory, Nippon Steel Corporation (72) Inventor Ken Sasaki 5-13-16 Ginza, Chuo-ku, Tokyo Nippon Steel Chemical Co., Ltd.

Claims (3)

[Claims] 1. A carbon fiber reinforced plastic tubular body having a plurality of reinforcing fiber directions, wherein an exciting coil group for selectively passing an induced current is provided in each direction of the reinforcing fibers, and each of the exciting coils is provided. A method for detecting fiber breakage of a tubular body made of carbon fiber reinforced plastics, characterized in that the fiber breakage in each direction of the reinforcing fiber is detected from the impedance change. 2. A carbon fiber reinforced plastic tubular body having a plurality of reinforcing fiber directions, wherein among the reinforcing fibers, fibers reinforced in a direction of + 80 ° to −80 ° with respect to the axis of the tubular body are selectively selected. Providing an exciting coil group for flowing an induced current, from each impedance change of the exciting coil, detecting fiber breakage in each direction of the reinforcing fiber, characterized in that the tubular body made of carbon fiber reinforced plastics Fiber breakage detection method. 3. The fiber breakage according to claim 1 and 2, wherein a detection coil group forming a pair with the excitation coil is provided separately from the excitation coil group, and a fiber breakage occurs in each direction of the reinforcing fiber from a change in impedance of each of the detection coils. A method for detecting fiber breakage in a tubular body made of carbon fiber reinforced plastics, which comprises: