JP3406045B2 - FRP member capable of detecting internal damage - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is an FR capable of detecting internal damage.
The present invention relates to a P (fiber reinforced plastic) member, and more particularly to an FRP member capable of detecting internal damage by utilizing the stress-magnetic property of a soft magnetic material.

[0002]

2. Description of the Related Art Conventionally, as this kind of FRP member, FR
It is publicly known that a P member main body is embedded with long carbon fibers (see, for example, JP-A-60-114741).

The detection of the internal damage of the FRP member is based on the fact that the electric resistance of the carbon long fibers is measured and, if the internal damage occurs, the carbon long fibers are broken and the electric resistance value changes. .

[0004]

However, the conventional F
In the RP member, a minute internal damage to the extent that the carbon long fibers are not broken, for example, a hair crack generated around the carbon long fibers (and thus the reinforcing fibers) in the plastic matrix, the carbon long fibers (and therefore the reinforcing fibers), and the plastic. There is a problem that interfacial separation between matrices cannot be detected.

In view of the above, it is an object of the present invention to provide the FRP member configured so that the minute internal damage as described above can be reliably detected.

[0006]

DISCLOSURE OF THE INVENTION The present invention is a FRP member main body in the form of a plate , which is an FRP member capable of detecting internal damage by utilizing the stress-magnetic characteristics of a soft magnetic material.
In the FRP member body, and the plurality of soft magnetic material which is embedded so as to form a single layer along the one of the FRP member body surface is constrained to a state of being applied an external force, the other
It is embedded so as to form one layer along the surface of the FRP member body.
And a plurality of the soft magnets that are restrained in a state in which an external force is applied
And one side of the FRP member body surface side
Of the plurality of soft magnetic materials present in the same and the other FRP member book
The plurality of soft magnetic bodies present on the body surface side are the FRP portion.
Plane symmetry with a virtual dividing surface that divides the thickness of the material body into two
It is characterized in that they are arranged in a relationship .

[0007]

With the above-mentioned structure, the stress of the soft magnetic material can be accurately measured from the respective surface sides of the FRP member main body.

In the FRP member body, if a hair crack occurs in the plastic matrix or an interfacial peeling occurs between the plastic matrix and the soft magnetic material,
Since the binding force of the plastic matrix to the soft magnetic material, and thus the external force initially applied, is reduced, the stress of the soft magnetic material is also reduced accordingly, so that minute internal damage to the FRP member can be detected.

[0009] and in this case, each surface of the FRP member body, its
There each soft magnetic body and is substantially equal distance along the surface of, and since the distance is short, the output level for the internal information of the FRP member resulting from their soft magnetic material is high, thereby high sensitivity the presence or absence of internal damage Can be detected with. In addition, a plurality of amorphous metals are formed on both surface sides of the FRP member body.
When the wires are arranged in layers, the cross-sectional structure of the FRP member is
Since it is the same on the side, the warp of the FRP member is prevented.
You can stop.

[0010] Incidentally, the FRP member body, when arranging a plurality of soft magnetic material so as to form two or more layers along one surface thereof, the magnitude of the distortion when the bending or the like occurs,
Damage is likely to occur near the surface of the FRP member, and when damage occurs near the surface of the FRP member, if other soft magnetic material exists in a undamaged region deeper than that, sound information is also detected at the same time. Ambiguous internal damage information.

The application of external force to the soft magnetic material is easily realized by the difference in coefficient of thermal expansion between the soft magnetic material and the soft magnetic material when the plastic matrix is heated and hardened. Means such as embedding in a matrix may be adopted.

[0012]

Reference Example of EXAMPLES internal damage detectable plate FRP member shown in FIG. 1 F, the member F is to FR such a plate
The P member main body Fa and the FRP member main body Fa are embedded so as to form one layer along one FRP member main body surface s ₁ and an external force, in this example, a tensile load is applied.
It is composed of a plurality of soft magnetic bodies w that are restrained in the closed state . In the embodiment of the plate-shaped FRP member F shown in FIG.
The member F includes a plate-shaped FRP member main body Fa and
One of the FRP member main bodies in the FRP member main body Fa
The external force is embedded so as to form one layer along the surface s ₁ ,
Similar to the above, the compound that is constrained in the state in which a tensile load is applied is
Number of the soft magnetic materials w and the other FRP member body surface s ₂
Is embedded to form one layer along with external force, same as above
A plurality of the above are constrained in a state in which a tensile load is applied to
It is composed of a soft magnetic material w. One FRP member body table
The plurality of soft magnetic bodies w on the surface s ₁ side and the other FRP
The plurality of soft magnetic materials w on the surface s _{2 of the} member body are
A virtual dividing surface s that divides the thickness T of the FRP member body Fa into two equal parts.
They are arranged in a plane-symmetrical relationship with ₃ in between .

The FRP member body Fa is composed of carbon fibers as reinforcing fibers and epoxy resin as a plastic matrix.

The soft magnetic material w is composed of an amorphous metal wire,
In the FRP member body Fa, a plurality of amorphous metal wires w
Are in parallel at regular intervals.

[0015]

When a plurality of amorphous metal wires w are arranged in layers on both surfaces s ₁ and s ₂ of the FRP member body Fa as described above , the cross-sectional structure of the FRP member F has both surfaces s ₁ and s _2. Since they are the same on the side, the warp of the FRP member F can be prevented.

In FIGS. 1 and 2, the amorphous metal wire w is
A part of the outer peripheral surface is the surface s ₁ , s of the FRP member main body Fa.
_It may be embedded in the FRP member main body Fa so as to be exposed from ₂ .

When the stress of the amorphous metal wire w in the FRP member F is measured, an alternating magnetic field exceeding the coercive force of the metal wire w is applied to the amorphous metal wire w to be measured by using an exciting coil. To induce an AC electromotive force in the detection coil through the amorphous metal wire w, and in the waveform of the AC electromotive force, one or more harmonic components including the stress information of the amorphous metal wire w are generated. A method of using the effective value E as the measurement amount is adopted.

In this way, the effective value E of one or more harmonic components including the stress information of the amorphous metal wire w is used as the measured quantity.
That is, if the harmonic component is captured as a quantity, the stress of the amorphous metal wire w can be measured with high accuracy, and thus the minute stress change can be accurately detected.

Next, the principle of the stress measuring method will be described.

In FIG. 3, an amorphous metal wire w is inserted through the exciting coil 2 connected to the oscillator 1 and the detecting coil 3, and a predetermined tensile load is applied to the metal wire w.

When the oscillator 1 is operated and the exciting coil 2 applies an alternating magnetic field H to the amorphous metal wire w which does not include a direct current magnetic field component and exceeds the coercive force Hc of the metal wire w,
Positive / negative symmetrical AC electromotive force V ₂ is induced in the detection coil 3 through the amorphous metal wire w.

Here, the AC electromotive force V ₂ is, as shown in [Equation 1],

[0024]

[Equation 1] Is represented. However, φ is magnetic flux, t is time, α is a coefficient, I is the strength of magnetization of the amorphous metal wire w, and H is the strength of the AC magnetic field.

The alternating magnetic field H is, as shown in [Equation 2],

[0026]

[Equation 2] Is represented. However, Hm is the amplitude of the alternating magnetic field, f ₀ is the frequency, and ψ ₀ is the phase angle.

Here, when [Equation 2] is differentiated with respect to time t, as shown in [Equation 3],

[0028]

[Equation 3] Becomes

Therefore, the dH / dt of [Equation 3] is changed to [Equation 1]
Substituting into, the AC electromotive force V ₂ is, as shown in [Equation 4],

[0030]

[Equation 4] Is represented.

In the magnetization process of the amorphous metal wire w, the magnetization curve as shown by the line a in FIG. 4 is obtained, so that [Equation 4] is obtained by using the instantaneous magnetic susceptibility dI (H) / dH. 5],

[0032]

[Equation 5] Is represented.

This AC electromotive force V ₂ contains a harmonic component because its waveform is a distorted wave as shown in FIG. In this case, since the AC magnetic field H does not include the DC magnetic field component as described above, the harmonic component of the AC electromotive force V ₂ is, in principle, composed of only odd harmonic components and does not include even harmonic components. Absent.

The harmonic component is the instantaneous magnetic susceptibility dI (H) /
It depends on dH, and its instantaneous magnetic susceptibility dI (H) / dH depends on the stress of the amorphous metal wire w. Therefore, the harmonic component contains the stress information of the amorphous metal wire w.

Therefore, the waveform of the AC electromotive force V ₂ is frequency-analyzed using a spectrum analyzer and divided into a fundamental wave component and a harmonic component, and the effective value E of one or more harmonic components is determined by the amorphous metal wire w. The stress measurement amount of.

For example, the harmonic components are the third, fifth, seventh,
When it is the 9th harmonic component, its effective value E is the effective value of the 3rd, 5th, 7th, and 9th harmonic component, which is E ₃ , respectively.
If E ₅ , E ₇ , and E ₉ are given, as shown in [Equation 6],

[0037]

[Equation 6] Is represented. An arithmetic unit is used to calculate the effective value E.

On the other hand, the magnetic characteristics of the amorphous metal wire w change with the change of the state in which the metal wire w is placed.
That is, the instantaneous magnetic susceptibility dA (H) / dH of the amorphous metal wire w
Changes from large to small as shown in FIG. 4, line c → line b → line a, when the tensile load on the metal line w changes from large to small, and as a result, the periodic function V ₂ (t) Changes, the effective value of the harmonic component also changes.

Therefore, by using the effective value E of the harmonic component as the measurement amount as described above, it is possible to accurately measure the minute stress change of the amorphous metal wire w as shown in FIG.

Specific examples will be described below.

In order to detect the presence or absence of internal damage due to fatigue of the FRP member F, the FRP member F in which the amorphous metal wire w is embedded.
Was manufactured by the following method. First, as an embodiment shown in FIG. 2, as shown in FIG. 7, eight cloths 5 _{1 to} 5 ₈ made of carbon fiber having a diameter of 6 μm are provided on both adjacent cloths 5.
₁ , 5 ₂ etc. are laminated so that the orientation of the carbon fibers changes by 45 °, and the first cloth 5 ₁ and the second cloth 5 ₂ are laminated.
A plurality of amorphous metal wires w each having a diameter of 125 μm were arranged in parallel with each other at a pitch of 0.3 mm between and, and between the seventh cloth 5 ₇ and the eighth cloth 5 ₈ . The composition of the amorphous metal wire w is Fe _66.5 Si _8.5 B ₁₂ Co ₁₁ Cr ₂ (numerical value is atomic%), and the coercive force Hc is 0.6 oersted.

[0042] impregnated with epoxy resin solution to the laminated body 6 in the cross 5 _{1-5 8} and the amorphous metal wires w, and then, the laminate 6 to 180 ° C., the epoxy resin is subjected to heat treatment for 2 hours As a result, the FRP member main body Fa having an epoxy resin matrix and carbon fibers is formed, and one layer is formed on each of the surfaces s ₁ and s ₂ of the FRP member main body Fa. An FRP member F including a plurality of embedded amorphous metal wires w was obtained.

In this case, the coefficient of thermal expansion of the amorphous metal wire w is 7.3 × 10 ^-6 / ° C., while the FRP member body Fa
Since it is 4.0 × 10 ⁻⁶ / ° C., each amorphous metal wire w is restrained in a state in which a tensile load is applied at room temperature after heat curing of the epoxy resin. When the amorphous metal wire w is magnetized, the metal wire w is elongated, that is, a magnetostriction phenomenon occurs, but the magnetostriction vibration phenomenon under an alternating magnetic field is suppressed by the carbon fiber and the cured epoxy resin. .

In this FRP member F, the carbon fiber volume fraction Vf is 58.3%, the epoxy resin volume fraction Vf is 37.5%, and the amorphous metal wire w has a volume fraction Vf of 4.2. %Met.

As Comparative Example 1, as shown in FIG.
Between the cross 5 ₁ and the second cross 5 ₂ , between the third cross 5 ₃ and the fourth cross 5 ₄ , between the fifth cross 5 ₅ and the sixth cross 5 ₆ , and 7th cross 5 ₇ and 8th
Of disposed respectively are arranged in parallel at 0.6mm pitch the same plurality of amorphous metal wire w between the cloth 5 ₈ was fabricated FRP member in the same manner. In this FRP member, a plurality of amorphous metal wires w are embedded so as to form two layers on each surface s ₁ and s ₂ .

As Comparative Example 2, as shown in FIG.
Between the cross 5 ₁ and the second cross 5 ₂ , between the second cross 5 ₂ and the third cross 5 ₃ , between the third cross 5 ₃ and the fourth cross 5 ₄ , Between the fifth cross 5 ₅ and the sixth cross 5 ₆ , between the sixth cross 5 ₆ and the seventh cross 5 _7, and between the seventh cross 5 ₇ and the eighth cross 5 _8. And a plurality of amorphous metal wires w similar to the above is 0.9 respectively.
FRPs are arranged in parallel at a mm pitch and are processed in the same manner as above.
I made the parts. In this FRP member, each surface s
_A plurality of amorphous metal wires w are embedded so as to form three layers for ₁ and s ₂ .

FIG. 10 shows an example of the stress measuring device 8, and the device 8 is constructed as follows. That is, the ferrite core 9 is formed in a U shape by the pair of leg portions 9a and the connecting portion 9b that connects one ends of the both leg portions 9a. Connecting part 9b
The detection coil 3 is wound around 100 turns (10 turns / mm), and the excitation coil 2 is wound around the detection coil 3 by 100 turns.
It is wound (10 turns / mm). The exciting coil 2 is connected to the oscillator 1. The detection coil 3 is connected to the spectrum analyzer 10, and the spectrum analyzer 10 is connected to the calculator 11.

First, stress measurement was performed on the amorphous metal wires w of Examples and Comparative Examples 1 and 2. In the stress measurement of the amorphous metal wire w, as shown in FIG. 10, the end surfaces of both leg portions 9a of the core 9 are brought into contact with one surface s ₁ of the FRP member F, and the oscillator 1 is set to include a DC magnetic field component. The sine wave, the frequency of 1 kHz, the peak-to-peak voltage, that is, the peak-to-peak voltage in one cycle, which is 15 V _pp , is applied to the exciting coil 2 to generate an AC magnetic field H exceeding the coercive force Hc of the amorphous metal wire w. Granted. As a result, a magnetic path is formed between the core 9 and the amorphous metal wire w, and an AC electromotive force V ₂ is induced in the detection coil 3. This AC electromotive force V ₂ is input to the spectrum analyzer 10, and then the calculator 11
The effective value E of the third, fifth, seventh, and ninth harmonic components, which are harmonic components, that is, as shown in [Equation 7],

[0049]

[Equation 7] Was output, and this was used as the stress measurement amount of the amorphous metal wire w.

Next, a tensile-tensile fatigue test was conducted on the examples and the like, and the stress of the amorphous metal wire w was measured at every predetermined number of stress cycle repetitions. The fatigue test conditions are a minimum tensile strain of 800 με (microstrain), a maximum tensile strain of 8000 με, and a repetition frequency of 20 Hz.

Then, the number of stress cycle repetitions and the effective value E
When the relationship with is obtained, the results shown in FIG. 11 and lines d _{1 to} d ₃ are obtained. In the figure, the line d ₁ is the example, and the line d ₂ is the comparative example 1.
And the line d ₃ corresponds to Comparative Example 2, respectively.

In the embodiment shown in FIG. 11 and line d ₁ , the effective value E is constant up to the stress cycle number of 6 × 10 ³ times, which indicates that the FRP member F is undamaged. When the number of stress cycle repetitions exceeds 6 × 10 ³ , the effective value E begins to fall. This is the FRP member F
Since hair cracks, interfacial delamination, etc. occur inside, the restraining force on the amorphous metal wire w is reduced, and as a result, the stress of the amorphous metal wire w is reduced and the magnetostrictive vibration phenomenon under an alternating magnetic field is reduced. This is because the suppression was eased. In this case, since the falling start point p of the effective value E is extremely clear, it can be surely confirmed that the FRP member F is internally damaged.

In Comparative Examples 1 and 2 of FIG. 11 and lines d ₂ and d ₃ , the output is low when the FRP member is undamaged,
As a result, the descent start point p is 1
Although it is 0 ⁴ , the descent start point p is unclear, and the internal damage detection sensitivity is significantly lower than that in the example.

[0054]

EFFECTS OF THE INVENTION According to the present invention, with the above-described structure, it is possible to provide an FRP member capable of accurately measuring the stress of a soft magnetic material and detecting internal damage with high sensitivity.

[Brief description of drawings]

FIG. 1 is a perspective view showing a reference example of an FRP member in which an amorphous metal wire is embedded.

FIG. 2 is a perspective view showing an embodiment of an FRP member having an amorphous metal wire embedded therein.

FIG. 3 is a principle diagram of a stress measuring method.

FIG. 4 is a magnetization curve diagram of an amorphous metal wire.

FIG. 5 is a waveform diagram of AC electromotive force V ₂ .

FIG. 6 is a graph showing the relationship between stress and effective value E of harmonic components.

In the embodiment of FIG. 7 FRP member is an explanatory diagram showing the relationship between the carbon fiber cloths and an amorphous metal wire.

In the comparative example of FIG. 8 FRP member is an explanatory diagram showing the relationship between the carbon fiber cloths and an amorphous metal wire.

In another comparative example of FIG. 9 FRP member is an explanatory diagram showing the relationship between the carbon fiber cloths and an amorphous metal wire.

FIG. 10 is a schematic view of a stress measuring device.

FIG. 11 is a graph showing the relationship between the stress cycle repetition number and the effective value E of the harmonic component.

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-6-126848 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 7/00-7/14 B29C 70 / 00-70/88 B32B 27/04

Claims (2)

(57) [Claims] 1. A FRP member (Fa) in the form of a plate , which is an FRP member capable of detecting internal damage by utilizing stress-magnetic characteristics of a soft magnetic material (w), and its FRP.
In member body (Fa), a plurality of said soft magnetic material is constrained to buried in a state where an external force is applied so as to form a single layer along the one of the FRP member body surface (s ₁₎ and (w) , Along the other FRP member body surface (s ₂ ) 1
In a state where it is embedded so as to form one layer and external force is applied
And a plurality of the soft magnetic materials (w) to be constrained,
A plurality of FRP member main body surface (s ₁ ) sides
The soft magnetic material (w) and the other FRP member main body surface
A plurality of the soft magnetic bodies (w) on the (s ₂ ) side are
Virtually dividing the thickness (T) of the FRP member body (Fa) into two equal parts
They are arranged in a plane-symmetrical relationship with the dividing surface (s ₃ ) in between.
Characterized in that the internal damage detectable FRP member. 2. The soft magnetic body (w) is an amorphous metal wire, and a plurality of the amorphous metal wires are arranged in parallel in the FRP member main body (Fa) at regular intervals. The FRP member according to 1, which can detect internal damage .