JP2002116004A - Distortion-measuring method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distortion-measuring method and device which do not require use of a large number of gauges, or special knowledge, techniques, or expensive apparatus, and moreover provide a method and device capable of detecting internal damages, even if damaged parts and broken points are at a location in a base material and detecting internal damages, without embedding an optical fiber or a piezoelectric material in the material, and composite materials to be used for the same. SOLUTION: A composite reinforcing fiber (10), with a conductive core material (12) and a coating layer (13), with which the core material (12) is coated and which has an electrical resistance substantially larger than the core material (12), is embedded in works (W and WA) of resin, metal, ceramics, and a composite material, and both ends (10E and 10E) of the core material (12) are connected to a resistance-variable electrical resistance measuring device (16) and the distortion-measuring device (18). Variations (δR) in the electrical resistance which occur in the composite reinforcing fiber (10) are converted into distortions, to measure the distortion in the works (W and WA).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring strain of a material.

[0002]

2. Description of the Related Art As is well known, if the strain of a material is determined,
The stress acting on it can be determined immediately. Therefore, in the prior art, when measuring the stress in a material, the strain of the material was measured using a strain gauge or a displacement gauge.

However, when measuring the strain of a large measuring object such as the material of a large structure, there is a problem that a large number of cages must be specified.

[0004] Other conventional techniques include ultrasonic method, AE
A method of searching for a local microscopic change, such as a method or an X-ray method, is widely used. However, these methods generally require special knowledge and skills. Also, the equipment to be installed is expensive, and cannot be said to be a versatile method.

[0005] On the other hand, there has been a demand for detecting the presence or absence of damage inside the material in addition to the measurement of strain or stress of the material. Again,
It has been conventionally performed to respond by measurement using a strain gauge or a displacement gauge. When the damaged part or the break point is located at or near the measuring point or the gauge attachment point, the related art is also effective.

[0006] However, it is difficult to cope with a case where a damaged part or the like is separated from a place where the gauge is attached by measuring with a strain gauge or a displacement gauge.

[0007] As another internal damage detection technique, conventionally, an optical fiber or a piezoelectric material is buried in the material.
Techniques for detecting internal damage have been proposed.

However, materials having an internal damage detection function, such as optical fibers and piezoelectric materials, are not known to be compatible with an embedded base material (material to be detected).
In application, there is a problem that both interfaces must be sufficiently evaluated.

[0009] Further, since the optical fiber and the piezoelectric element are materials that are lower in heat and strength than the embedded material, there is also a problem that the strength of the composite material as a whole is reduced.

[0010]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned problems of the prior art, and it is not necessary to use a large number of cages even when measuring a large strain. It is an object of the present invention to provide a strain measuring method and apparatus which do not require special knowledge and technology and expensive equipment, and materials used for the same.

Another object of the present invention is to detect internal damage regardless of the location of a damage or a break point in a base material, and to bury an optical fiber or a piezoelectric material in the material. It is an object of the present invention to provide a method and an apparatus for detecting internal damage without any problem.

[0012]

As a result of various studies, the inventor of the present invention has found that a composite comprising a conductive core and a coating layer surrounding the core and having a higher electric resistance than the core is provided. It has been found that the reinforcing fiber changes the electric resistance of the core material in response to the stress acting thereon or the strain generated there. Then, it has been found that if such a composite reinforcing fiber is embedded in a measurement object whose strain is to be measured and the amount of change in electric resistance is measured, the strain generated in the measurement object can be easily obtained. The present invention has been proposed based on such findings.

The strain measuring method of the present invention includes a step of measuring the electric resistance (R) of the composite reinforcing fiber (10), and the composite reinforcing fiber (10) is an object to be measured (work: W).
A conductive core material (12), and a coating layer (13) covering around the core material (12) and having a higher electrical resistance than the core material (12). Obtaining a variation (δR) of the electric resistance when a load acts on the measurement target (W); and determining a strain of the measurement target (W) based on the variation (δR). have.

Further, the strain measuring apparatus of the present invention has a composite reinforcing fiber (10) embedded in an object to be measured (W), and the composite reinforcing fiber (10) is a conductive core material (1).
2) and a core material (1) covering the periphery of the core material (12).
2) a coating layer (13) having an electric resistance higher than that of (2), an electric resistance measuring means (16) for measuring the electric resistance (R) of the composite reinforcing fiber (10), and a measurement object ( Means (18-1, 18-2) for determining the variation (δR) of the electric resistance when a load acts on W), and determining the strain of the object to be measured (W) based on the variation (δR) (18-1, 18-3).

According to the present invention having such a configuration, the amount of change in the electrical resistance of the composite reinforcing fiber embedded in the object to be measured is determined, and the strain of the composite reinforcing fiber is determined based on the amount of change. Thus, the strain of the object to be measured is determined. Here, since a fibrous or long member called a composite reinforcing fiber is used as a measuring member, it is not necessary to arrange a large number of large measuring objects like a strain gauge. Since the measurement itself is performed by an extremely versatile method of detecting an electric resistance value, no special technique or instrument is required.

Here, when the inventor has created a characteristic curve of stress and strain based on the strain measured by the above-described composite reinforcing fiber and the data on the external force, the inventor has found that the curve is linearly related to the curve. When a region (variation: CR) that fluctuates in a linear relationship exists, it has been found that damage has occurred inside the measurement object (work). The internal damage detection method and device of the present invention have been created based on such knowledge.

The method for detecting internal damage according to the present invention comprises the step of measuring the electrical resistance (R) of the composite reinforcing fiber (10),
The composite reinforcing fiber (10) is an object to be measured (work: W
A) comprising a conductive core material (12) embedded in A) and a coating layer (13) which covers around the core material (12) and has higher electric resistance than the core material (12). And
A step of obtaining a variation (δR) of the electric resistance when a load is applied to the object to be measured (WA);
Determining the strain of the object to be measured (WA) based on the above, obtaining the characteristic curve of the stress and strain from the determined strain and the load applied to the object to be measured (WA), and the characteristic curve of the stress and strain Determining the presence or absence of internal damage to the measurement object (WA) based on the presence or absence of the above-mentioned fluctuation region (CR).

The internal damage detecting device according to the present invention provides a composite reinforcing fiber (1) embedded in a measurement object (WA).
0), wherein the composite reinforcing fiber (10) covers the conductive core material (12) and the periphery of the core material (12) and has a higher electrical resistance than the core material (12). Coating layer (13)
And an electric resistance measuring means (16) for measuring the electric resistance (R) of the composite reinforcing fiber (10), and a fluctuation amount of the electric resistance when a load acts on the measurement object (WA). Means for calculating (δR) (18-1, 18-2)
Means (18-1, 18-3) for determining the strain of the object to be measured (WA) based on the variation (δR), and the stress from the determined strain and the load acting on the object to be measured (WA) And a means for outputting a characteristic curve of strain (18, 18-
(1) determining means (30) configured to determine the presence or absence of internal damage of the measurement object (WA) based on the presence or absence of a fluctuation region (CR) on the output characteristic curve of stress and strain;
And

In the above-described strain measuring method and apparatus, and internal damage detecting method and apparatus, a measuring object or a composite material (W, W
A) has a matrix and a composite reinforcing fiber (10, 10-C) embedded in the matrix, and the composite reinforcing fiber (1
0) includes a conductive core material (12) and a coating layer (13) that covers the periphery of the core material (12) and has a higher electric resistance than the core material (12). An end (10E) of the reinforcing fiber (10) protrudes from the base material, and the coating layer (13) is peeled off at the end (10E) to remove the core material (1).
2) is characterized by being exposed.

According to the composite material of the present invention having the above-mentioned structure, the composite reinforcing fiber embedded in the base material is subjected to a change in electric resistance (change in strain) of the core material against damage from external load or heat. In addition, the stress applied to the material can be detected. In addition, a characteristic curve of stress and strain is created, and internal damage can be detected based on whether or not there is a region (variation: CR) that shifts from a linear relationship to a non-linear relationship.

In practicing the present invention, the relationship between the resistance of the core material and the coating material may be such that the electric resistance value of the core material is so small that it can be almost ignored compared to the electric resistance value of the coating material. For example, when the electric resistance value of the core material is R12 and the electric resistance value of the coating material is R13, R12
It suffices that a relational expression such that + R13 is substantially equal to R13 holds.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 to FIG. 4 show an embodiment relating to the strain measurement of the present invention. 5 to 8 show an embodiment relating to the detection of internal damage of the present invention.

In FIG. 1, a non-measurement material (work) indicated by a reference character W is made of, for example, resin, metal, ceramics, or a composite material, and has embedded therein a composite reinforcing fiber 10 functioning as a strain measuring member. .

The composite reinforcing fiber (fibrous strain measuring member) 10 is made of a core material 1 made of a material having good conductivity.
2 and a coating layer 13 made of a material having a much higher electric resistance value than the core material 12 and covering the surface of the core material 12. In the illustrated embodiment,
Tungsten (chemical symbol: W) is used as the core material 12, and boron (chemical symbol: B) is used as the coating material. Here, each electric resistance value is 8 cm, tungsten is 0.3 kΩ, and boron is about 600 kΩ-800 kΩ.

Here, the core material 12 and the coating material 13 are not limited to tungsten and boron. Any other combination may be used as long as the electrical resistance value of the core material 12 is so small that it can be almost neglected compared to the electrical resistance value of the coating material 13. Alternatively, any combination may be used as long as the relationship represented by the following formula is established between the electric resistance value R12 of the core material 12 and the electric resistance value R13 of the coating material 13. R12 + R13 is approximately equal to R13.

For example, carbon (chemical symbol: C) can be used as the core material 12 and silicon carbide (chemical symbol: SiC) can be used as the coating material 13. Alternatively, tungsten may be selected as the core material 12 and silicon carbide may be selected as the coating material 13.

In order to improve the strength of the work W made of resin, metal, ceramics, composite material and the like, a composite reinforcing fiber (fibrous strain measuring member) 10 is embedded in the work W. And both ends 10E of the fiber 10 for composite reinforcement,
In 10E, the covering material 13 is peeled off from the core material 12, and the core material 12 is exposed.

The cores 12 exposed at both ends of the composite reinforcing fiber 10 are connected to signal lines CL-1 and CL-1, and are connected to the electric resistance measuring device 16 via the signal lines. I have. The electric resistance measuring device 16 is a type that measures electric resistance using a bridge box (bridge circuit) having a variable resistance, and the electric resistance value indicated by an arrow R in FIG. 1, that is, the longitudinal direction of the composite reinforcing fiber 10. The electrical resistance of the sample is measured. Specifically, the ridge box 6 having a variable resistance measures the electrical resistance value R in the longitudinal direction of the composite reinforcing fiber 10 based on the principle of Wheatstone pledge. In addition, as the electric resistance measuring device 16, a known / commercial one can be used.

The electric resistance measuring device 16 is connected to the signal line CL.
-2 is connected to the strain measuring device 18. The strain measuring device 18 has a processing unit 18-1 and storage units 18-2 and 18-3, and the electric resistance value (composite reinforcing fiber 1) transmitted from the signal line CL-2.
The strain generated in the composite reinforcing fiber 10, that is, the strain of the work W, is determined from the variation amount of the electrical resistance value R) in the longitudinal direction of 0.

Specifically, the storage unit 18-2 includes:
Composite reinforcing fiber 10 measured by electric resistance measuring device 16
Is stored, and the stored electric resistance R is stored in the processing unit 1 via the signal line CL-3.
8-1 and the processing unit 18-1 makes an appropriate comparison to determine a variation amount δR of the electrical resistance value R in the longitudinal direction of the composite reinforcing fiber 10. And the storage unit 1
8-3 stores a relational expression, a characteristic curve, or a map between the variation amount of the electrical resistance value R in the longitudinal direction of the composite reinforcing fiber 10 and the “strain” amount in the longitudinal direction of the composite reinforcing fiber 10. ing.

When the variation δR of the electric resistance R is determined by the processing unit 18-1, a relational expression or the like is called from the storage unit 18-3 via the signal transmission line CL-4,
The strain amount in the longitudinal direction of the composite reinforcing fiber 10, that is, the strain amount of the work W can be determined. Note that a relational expression between a variation amount δR of the electrical resistance value R in the longitudinal direction of the composite reinforcing fiber 10 stored in the storage unit 18-3 and a “strain” amount in the longitudinal direction of the composite reinforcing fiber 10, and a characteristic curve Alternatively, the map or the like is measured and prepared in advance.

The relationship between the strain and the stress in the composite reinforcing fiber 10 (relational expression, characteristic curve, map, or chart) is measured and stored in the storage unit 18-3 in advance. Therefore, if the strain is determined, the stress acting on the work W can be calculated immediately.

The work W determined by the strain measuring device 18
Is displayed on the display unit 22 via the signal transmission line CL-6, or printed and output by the printing unit 24 via the signal transmission line CL-7.

FIGS. 2 and 3 show experimental examples for proving that the composite reinforcing fiber 10 functions as a strain measuring member. Specifically, the method of the four-point bending test of the work W1 in which the composite reinforcing fiber 10 is embedded and the result are shown.

In FIG. 2, in order to perform a so-called four-point bending test on the work W1 in which the composite reinforcing fiber 10 is embedded in the epoxy resin, the load W is applied to the work W1 while supporting the work W1 at the supporting points SL and SR. The loads F, F are applied. Arrows FR at the fulcrums SL and SR indicate reaction forces to the loads F and F, respectively.

In the experimental example shown in FIG.
Numeral 0 indicates that the core 12 is made of tungsten, and the coating layer 13 that covers the periphery of the core 12 is made of boron. The wire diameter of the composite reinforcing fiber 11 is 0.1 mm in diameter.

In FIG. 2, the size of the work W1 is 6 mm.
X 5 mm x 65 mm (width x height x length). The above-described composite reinforcing fiber 10 is embedded at a depth of 0.3 mm from the surface of the work W1 (made of epoxy resin).
Then, at both ends 10E and 10E of the composite reinforcing fiber 10, the boron coating layer 13 is peeled off, and the tungsten core material 12 is exposed. Although not shown in FIG. 2, the exposed core 12 is connected to signal lines CL-1 and CL-1 as shown in FIG.
6. Strain measuring device 18, display means 22 or printing means 2
4 are provided. Further, on the surface of the work W1,
A strain gauge 16 is attached.

In this state, by applying loads F, F to the load application points RL, RR, a four-point bending load is applied to the work W1. When a four-point bending load is applied to the work W1, the strain gauge 30 stuck on the surface of the work W1 shows a stress-strain characteristic as indicated by a plot “□” in FIG. On the other hand, the characteristic based on the strain obtained by the strain measuring device 18 shown in FIG.
(In FIG. 3, it is described as "damage detection functional material")
As shown in FIG.

The characteristics indicated by the plot “□” in FIG. 3 and the characteristics indicated by the plot “●” almost coincide with each other, as apparent from comparison. From this, the measurement of the tensile or compressive strain performed by the composite reinforcing fiber 10 composed of the core material having relatively good conductivity and the coating material having a large resistance value is the same as when the strain gauge 30 is used. It is understood that this is done.

Next, a method for measuring strain according to the first embodiment will be described with reference to FIGS. First,
A tensile force or a compressive force is applied to the work W by means not shown (step S1). When a tensile force or a compressive force acts on the work W to generate a strain, the composite reinforcing fiber 10 embedded in the work W also generates a strain, and the electrical resistance value R in the longitudinal direction of the composite reinforcing fiber 10 decreases. fluctuate.

As shown in FIG. 1, the composite reinforcing fiber 10 is connected to an electric resistance measuring device 16 via signal lines CL-1 and CL-1, and its electric resistance value R is used for measuring the strain. The fluctuation amount δR of the electric resistance value R is calculated by being stored in the storage unit 18-2 in the device 18 and being appropriately compared by the processing unit 18-1 (FIG. 4: step S2).

If the variation δR of the electric resistance value R is determined,
Relational expressions and the like stored in the storage unit 18-3 in the strain measuring device 18 (the amount of variation in the electrical resistance value R in the longitudinal direction of the composite reinforcing fiber 10 and the “strain” in the longitudinal direction of the composite reinforcing fiber 10). The amount of strain in the longitudinal direction of the composite reinforcing fiber 10, that is, the amount of strain of the work W is determined using a relational expression with respect to the amount, a characteristic curve, a map, or the like (step S3).

When the strain of the work W is determined, the stress of the work W can be immediately calculated from the relationship between the stress and the strain of the composite reinforcing fiber 10 stored in the storage means 18-3. The determined strain and / or stress is displayed on the display unit 22 or printed by the printing unit 24,
Is output.

By appropriately setting the embedding position of the composite reinforcing fiber 10, not only strain against tension and compression but also strain against torsion can be measured.

The second embodiment shown in FIGS.
1 is an embodiment according to a technique for detecting internal damage of a hologram. FIG.
The configuration, operation, and effect of the device shown by are substantially the same as those of the device shown in FIG.

However, in the apparatus shown in FIG.
A control unit (for example, a computer) 30 for evaluating the internal damage of the vehicle is provided. Further, the strain measuring device 18 is further provided with another storage unit 19, and the storage unit 19 is provided with a signal line CL.
It is connected to the load unit 20 via -5. The load unit 20 controls a unit (not shown) for applying a tensile force or a compressive force to the work WA.
The external force (load) acting on A is adjusted. Then, the external force applied to the work WA is stored in the storage unit 19. Here, if the sectional area of the work WA is known, the work W
The stress acting on A is determined.

Therefore, in addition to determining the strain in the longitudinal direction of the composite reinforcing fiber 10, that is, the strain of the work WA, the “stress− It is possible to create a "strain diagram". That is, when the processing unit 18-1 of the strain measuring device 18 combines the strain determined in the same manner as in FIGS. 1 to 4 with the data of the external force or stress given from the storage unit 19, FIG. A stress-strain diagram or a stress-strain characteristic curve as shown in (described later) can be created.

The processing for determining the distortion of the work WA is the same as the processing procedure described with reference to FIGS.

However, the processing performed after determining the distortion of the work WA (steps S14-S1 in FIG. 8)
8: described later), the detection of the internal damage of the work WA is different from the strain measurement of the work W described with reference to FIGS.

Before describing the specific procedure for detecting the internal damage of the work WA, the reason why the internal damage of the work WA can be detected will be described with reference to FIGS. FIG. 6 shows an outline of a structure and a tensile test of a work WA1 as an object for detecting internal damage, and FIG.
The result of the tensile test of A1 is shown.

In FIG. 6, the work WA1 has a width of 16 mm.
The thickness is set to 1.5 mm x 80 mm in length, and is formed by embedding 11 of the above-mentioned composite reinforcing fibers 10 (the core material is tungsten and the coating layer is boron) in an ethoxy resin. Among the eleven composite reinforcing fibers 10, the central composite reinforcing fiber indicated by reference numeral 10-C is shown in FIG.
-It functions as a member for strain measurement described in FIG. 4 and also as a member for detecting damage in a work.

The work WA1 shown in FIG. 6 is subjected to a tensile test by a load acting means (not shown) by applying a tensile force indicated by the symbol PL. A strain gauge 30A is attached to a central portion of the surface of the work WA1 in FIG. At the same time as measuring the strain using the composite reinforcing fiber 10-C,
The strain is measured using the strain gauge 30A.

FIG. 7 shows the relationship between strain and stress as a result of the tensile test performed on the work WA1 shown in FIG. In FIG. 7, the characteristic curve indicated by the symbol “C30A”
It shows the strain-stress characteristics based on the measurement results using the strain gauge 30A, and the characteristic curve denoted by the symbol “C10-C” indicates the strain-stress due to the measurement results using the composite reinforcing fiber 10-C.
Shows stress characteristics.

When the characteristic curves C30A and C10-C are compared, the points (strain 4500 μS, stress 20
Up to MPa). However, the characteristic curve C10-C clearly fluctuates in the region indicated by the symbol CR, and the two subsequent characteristic curves are completely different. That is, the stress and strain shift from a linear relationship to a nonlinear relationship at the region CR. Here, in the tensile test shown in FIG. 6, at the stage corresponding to the region indicated by the symbol CR (region where stress and strain shift from a linear relationship to a nonlinear relationship: fluctuation), the composite reinforcement functioning as a detection member Fibers other than the fiber for use 10-C are broken. That is, the fluctuation CR in the characteristic curve C10-C indicates damage inside the work WA1. On the other hand, strain gauge 3
In the strain-stress characteristic C30A based on 0A, such damage inside the work is not detected at all.

FIG. 7 shows two characteristic curves C10-C and C30.
Comparing A, it is clear that if the strain-stress characteristics are obtained using the composite reinforcing fiber 10 (10-C), damage inside the work can be detected. In other words, using the composite reinforcing fiber 10 (10-C) enables not only strain measurement but also detection of damage in the material. In particular,
Using the composite reinforcing fiber 10 as described above as a detection member, a strain-stress characteristic curve (or a stress-strain diagram) is created, and the characteristic curve (characteristic curve C1 in FIG.
The presence / absence of a change inside the work (such as the region CR in 0-C) can be detected.

Hereinafter, referring to FIG. 5 and FIG.
(FIG. 5) Detection of presence or absence of internal damage will be described.
8, steps S11-S13 are the same as steps S1-S3 in FIG.

As described above, the means (not shown) for applying a tensile force or a compressive force to the work WA is controlled by the load unit 20, and the external force applied to the work WA is stored in the storage unit 19 of the strain measuring device 18. . Work W
Since the cross-sectional area of A is known, the stress acting on the work WA is immediately determined. As a result, in addition to determining the strain of the work WA, a “stress-strain diagram” of the work W can be created (step S14).

When the stress-strain diagram is created and output (step S14 is completed), the control unit 30 causes a variation (variation CR) on the diagram as shown by a region CR in FIG. It is determined whether or not to perform (step S15).

If there is no variation CR on the stress-strain diagram created in step S14 (NO in step S15), it is determined that no damage has occurred in the work WA (step S16). On the other hand, if there is a variation CR on the stress-strain diagram (step S15: YES), it is determined that damage has occurred in the work WA (step S17).

Although not shown, the composite reinforcing fiber 1
If a large amount of data can be obtained for the stress-strain diagram and the variation CR created using 0, the position of the internal damage and the scale of the internal damage are determined from the position where the variation CR occurs and the subsequent variation of the stress-strain characteristic curve. Note that identification is also possible.
Note that the control unit 30 is not limited to a computer, and can be configured by an operator.

In the illustrated embodiment, only the tensile load and the compressive load are described as the external influences applied to the work. However, the present invention can be applied to the case where deformation is caused by external force such as torsion or heat. Is applicable.

[0063]

The effects of the present invention are listed below. According to (1), the strain of the material is measured (from the amount of change in the electric resistance value) by utilizing the fact that the electric resistance value of the core material changes in response to external load or heat damage. Can be done. (2) Since the stress acting on the material is determined from the strain,
The strength limit of the material can be predicted in advance, and sudden breakage of the material can be prevented. (3) Damage inside the material, which was impossible with a conventional strain cage or the like, can be detected. (4) The strength of the material can be improved by embedding the fiber for reinforcing the double bed into the material. (5) Since a fibrous measuring member is used, a large number of measuring members are not required even for a large measuring object. (6) Measurement is possible only with general-purpose equipment, and
Does not require skilled operators. (7) Since the measurement member is formed in a relatively thin fiber shape, the problem of matching with the material (base material) to be measured does not occur much. Therefore, detailed interface evaluation is unnecessary.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a measuring device for measuring strain using composite reinforcing fibers.

FIG. 2 is a diagram showing an embodiment of a four-point bending test on a work in which composite reinforcing fibers are embedded.

FIG. 3 is a characteristic diagram showing one example of a stress-strain diagram obtained by the four-point bending test shown in FIG.

FIG. 4 is a flowchart showing the procedure for implementing the strain measurement method of the present invention.

FIG. 5 is a block diagram showing a detection device that detects damage inside a work using a composite reinforcing fiber.

FIG. 6 is a diagram showing a mode of a tensile test of a work in which a plurality of composite reinforcing fibers are embedded.

FIG. 7 is a characteristic diagram showing one example of a stress-strain diagram obtained in the tensile test shown in FIG.

FIG. 8 is a flowchart showing an implementation procedure of the internal damage detection method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Fiber for composite reinforcement 12 ... Core material 13 ... Coating layer W, W1, WA, WA1 ... Work 10E ... End part of fiber for composite reinforcement CL-1-CL-7 ... Signal line 16: Electric resistance measuring device 18: Strain measuring device 18-1: Processing unit 18-2, 18-3: Storage unit 19: Storage unit 20: Load unit R ... Electrical resistance value of the composite reinforcing fiber in the longitudinal direction δR ... Amount of change in electric resistance value of the composite reinforcing fiber 22 ... Display means 24 ... Printing means 30 ... Control unit

Claims (5)

[Claims] A step of measuring an electric resistance of the composite reinforcing fiber, wherein the composite reinforcing fiber is embedded in an object to be measured, and covers a conductive core material and a periphery of the core material. And a coating layer having a larger electrical resistance than the core material, and a step of obtaining a variation of the electrical resistance when a load is applied to the measurement target; and a step of determining a distortion of the measurement target based on the variation. Determining the strain. 2. A composite reinforcing fiber embedded in an object to be measured, wherein the composite reinforcing fiber has a conductive core material and an electric resistance which covers the core material and is larger than the core material. An electrical resistance measuring means for measuring the electrical resistance of the composite reinforcing fiber, and means for determining the amount of change in electrical resistance when a load is applied to the object to be measured,
Means for determining the strain of the measurement object based on the variation amount,
And a strain measuring device. 3. A step of measuring an electric resistance of the composite reinforcing fiber, wherein the composite reinforcing fiber is embedded in an object to be measured, and covers a conductive core material and a periphery of the core material. And a coating layer having a larger electrical resistance than the core material, and a step of obtaining a variation of the electrical resistance when a load is applied to the measurement target; and a step of determining a distortion of the measurement target based on the variation. Determining, determining the characteristic curve of stress and strain from the determined strain and the load applied to the object to be measured, and internal damage of the object to be measured based on the presence or absence of a fluctuation region on the characteristic curve of stress and strain. Determining the presence or absence of
And a method for detecting internal damage. 4. A composite reinforcing fiber embedded in an object to be measured, wherein the composite reinforcing fiber has a conductive core and an electric resistance covering the core and having a larger electric resistance than the core. An electrical resistance measuring means for measuring the electrical resistance of the composite reinforcing fiber, and means for determining the amount of change in electrical resistance when a load is applied to the object to be measured,
Means for determining the strain of the object to be measured based on the variation, means for outputting a characteristic curve of stress and strain from the determined strain and the load applied to the object to be measured, and a characteristic curve of the output stress and strain A determination unit configured to determine the presence or absence of the internal damage of the measurement target based on the presence or absence of the above-mentioned fluctuation region. 5. A base material, and a composite reinforcing fiber embedded in the base material, wherein the composite reinforcing fiber covers a conductive core material, and covers the core material and forms a core material. A coating layer having a larger electric resistance than the core material, wherein the end of the composite reinforcing fiber protrudes from the base material, and the coating layer is peeled off at the end to expose the core material. And composite material.