JP2002131265A - Damage detection sensor, production method thereof and composite material with the same incorporated therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a damage detection sensor, capable of specifying a damaged site, a composite material enabling inhibition of the spread of damages at the damaged site, and to a provide manufacturing method of the damage detection sensor. SOLUTION: The damage detection sensor 1 has a titanium-nickel alloy foil 2, an electric circuit 3 bonded on one side of the titanium-nickel alloy foil 2 and a strain gauge 4 disposed on the electric circuit 3. The composite material 10 is made up of the damage detection sensor 1, which is arranged between fiber-reinforced resin layers 11 given distortions under normal temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a damage detection sensor for specifying a damaged portion of a composite material, a method for manufacturing the damage detection sensor, and a composite material incorporating the damage detection sensor.

[0002]

2. Description of the Related Art Composite materials applied to aircraft, space equipment, skyscrapers, public infrastructures and high-speed vehicles have a design allowance because the inside of the material is easily damaged by impact loads. It is set low and does not make full use of the inherent strength of the composite material. In addition, in order to raise the design tolerance, a material that has a damage suppressing effect is embedded inside the composite material, and even when an impact load is applied to the composite material, the load and damage at that time are detected to enhance safety. Such composites are known.

[0003] The use of a titanium-nickel alloy as an actuator for suppressing the propagation of cracks in a structural composite material or a vibration damping material for suppressing vibration by causing a change in rigidity by using the shape memory effect of the titanium-nickel alloy is, for example, disclosed in, Kaihei 8-1520
No. 8, JP-A-7-48637 and JP-A-7-48637
-48637.

Japanese Patent Application Laid-Open No. 8-15208 discloses that when a fine wire of a titanium-nickel shape memory alloy is embedded in a composite material having a laminated structure, an electric current is applied to the fine wire to cause cracks or damage to the matrix material. A composite damage detection system for detecting a change in current resistance of a thin wire is described.

Japanese Patent Application Laid-Open No. 6-212018 describes a polymer-based composite functional material having a structure in which at least one or more shape memory alloy materials having a temperature equal to or lower than a reverse transformation end temperature are arranged on the surface of or in the base material. Have been.

Japanese Patent Application Laid-Open No. 7-48637 describes a metal-based composite material having a structure in which at least one or more types of shape memory alloy material elements that cause thermoelastic transformation are mixed or arranged in a base material.

[0007]

Problems to be Solved by the Invention
Japanese Patent Application Laid-Open Publication No. H10-157, discloses a technical means for identifying a damaged portion by utilizing a change in the electric resistance characteristic of a shape memory alloy, and heating and shrinking the shape memory alloy in the vicinity of the damaged portion to prevent the progress of damage. However, with this technical means, when the length of the shape memory alloy is increased, the amount of change in the characteristics becomes smaller and the change becomes difficult to catch, and the damaged portion that caused the change in the characteristics of the relevant shape memory alloy is identified. It may not be possible.

JP-A-6-212018 and JP-A-7-148637 describe that a titanium-nickel alloy is used as an actuator for suppressing the growth of a crack in a structural composite material. Only describes that a strain gauge or a piezoelectric element can be used, but does not describe how to use them.

The present invention has been made in consideration of the above points, and provides a damage detection sensor capable of specifying a damaged portion of a composite material, a method of manufacturing the damage detection sensor, and a method of manufacturing a damaged portion of a composite material by incorporating the damage detection sensor. An object of the present invention is to provide a composite material capable of suppressing the progress of damage.

[0010]

A damage detection sensor according to the present invention comprises a titanium-nickel alloy foil, an electric circuit adhered to one surface of the titanium-nickel alloy foil, and a strain gauge arranged in the electric circuit. For example, when applied to a composite material, a damaged portion of the composite material can be specified by the amount of strain detected by the strain gauge.

A method for manufacturing a damage detection sensor according to the present invention comprises:
A predetermined amount of strain is applied to the titanium-nickel alloy foil, and the oxide film is removed from the titanium-nickel alloy foil having the strain amount by using a mixed aqueous solution of hydrofluoric acid and nitric acid. It is configured by anodizing with a sodium oxide solution and attaching a film having an electric circuit to which a strain gauge is connected on a titanium-nickel alloy foil that has been anodized.

A method for manufacturing a damage detection sensor according to the present invention comprises:
A predetermined amount of strain is applied to the titanium-nickel alloy foil, the oxide film is removed from the titanium-nickel alloy foil having the strain amount by a mixed aqueous solution of hydrofluoric acid and nitric acid, and the surface of the titanium-nickel alloy foil from which the oxide film is removed Is formed by applying a titanium coating treatment, further subjecting to a chemical conversion coating treatment, and attaching a film having an electric circuit to which a strain gauge is connected on the titanium coating subjected to the chemical conversion coating treatment.

[0013] The composite material of the present invention comprises the damage detection sensor according to claim 1 disposed between the fiber reinforced resin layers in a state where the strain is applied at room temperature, and recovers the shape of the titanium-nickel alloy foil. By using the function as a damage suppression function, the progress of damage can be suppressed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view of a damage detection sensor according to the present invention. The damage detection sensor 1 has a titanium-nickel alloy foil 2 surface-treated to enhance adhesiveness, and a titanium-nickel alloy foil 2 on one side. The electric circuit 3 includes the bonded electric circuit 3 and the strain gauge 4 disposed on the electric circuit 3.

The titanium-nickel alloy foil 2 is immersed in a room temperature bath of a mixed aqueous solution of hydrofluoric acid and nitric acid to remove the oxide film formed on the surface during the heat treatment, and then anodized with a sodium hydroxide solution. To form an anodized film on the surface.

The surface treatment for removing the oxide film from the titanium-nickel alloy foil 2 is performed, for example, by using 3% hydrofluoric acid and 1% hydrofluoric acid.
This is performed by immersing in a mixed aqueous solution of 0 to 15% nitric acid at room temperature for 3 to 5 minutes. The surface treatment for forming an anodic oxide film on the titanium-nickel alloy foil 2 is performed, for example, by treating a 10 to 15% NaOH electrolytic solution at a temperature of 10 to 20 ° C. at a voltage of 10 to 20 V for 30 to 60 seconds. .

Alternatively, the titanium-nickel alloy foil 2 is subjected to a titanium coating treatment on the surface from which the oxide film has been removed, and further subjected to a chemical conversion treatment to form a chemical conversion film. Preferably, the titanium coating is formed by an ion plating method.

As shown in FIG. 3, the electric circuit 3 uses a commercially available film in which a copper foil 6 is integrally bonded to a resin sheet 5, and uses a resin ink 7 on the surface of the copper foil 6 to use a strain gauge. Is formed by drawing a circuit diagram for extracting a signal from the resin sheet, etching the film with a ferric chloride solution, and removing the copper foil 6 from the resin sheet 5 except for the portion drawn with the resin ink 7. The strain gauge mounting portion is indicated by reference numeral 7a, and the portion drawn by the resin ink 7 is a lead wire 7b.
It is.

As shown in FIG. 1, the electric circuit 3 is designed so that the distance between the strain gauge mounting portions 7a is set so that the strain gauges 4 arranged on the strain gauge mounting portion 7a can detect damage of a required size. It is determined so as to correspond to an interval predetermined by simulation calculation. According to experiments,
An appropriate distance between the strain gauges 4 is in the range of 50 to 100 cm. In the electric circuit 3 shown in FIG. 1, the respective strain gauges 4 are arranged at predetermined intervals in the same direction.

The above-mentioned titanium-nickel alloy foil 2 integrally connects the electric circuit 3 via an adhesive layer 8 applied on one surface. Thereby, a required strain detection circuit is formed on the surface of the titanium-nickel alloy foil 2. In this case, titanium
The adhesive layer 8 applied to the nickel alloy foil 2, the resin sheet 5, and the resin sheet (not shown) covering the strain gauge 4 are made of the same or the same resin as that used for the base material of the fiber-reinforced resin composite material. The familiar one is chosen. Also,
It is desirable that the copper foil portion left as a circuit be sufficiently thin so as not to affect the adhesive strength between the prepreg and the titanium-nickel alloy foil 2.

FIG. 4 shows another embodiment of the damage detection sensor according to the present invention. This damage detection sensor 1a is composed of a titanium-nickel alloy foil 2 surface-treated so as to enhance adhesion, and a titanium-nickel alloy. It is composed of an electric circuit 3a adhered to one surface of the foil 2 and a strain gauge 4 arranged on the electric circuit 3a.

The electric circuit 3a is, as shown in FIG.
A Wheatstone bridge 9 having a 45-degree inclination in the direction of the force is formed, and four strain gauges 4a, 4b, 4c, and 4d are arranged on the Wheatstone bridge 9. In this case, the adjacent strain gauges 4a and 4b, 4b and 4c, 4c and 4d, 4d and 4a are arranged in directions orthogonal to each other.

In the Wheatstone bridge 9, the output voltage is the strain E of each of the strain gauges 4a, 4b, 4c and 4d.
E1-E2 + E calculated from E1, E2, E3 and E4
Since a voltage proportional to 3-E4 is output, the location can be estimated from the sign of the output value. For example, when a positive voltage is output, a crack is generated in a portion near the strain gauge 4a or 4c, and when a negative voltage is output, the strain gauge 4b is output.
Alternatively, it can be seen that a crack is generated in a portion near 4d.

Next, a method of manufacturing the damage detection sensor according to the present invention will be described. First, titanium-nickel alloy foil 2
And a film in which the copper foil 6 is integrally bonded to the resin sheet 5 is prepared.

Next, the both ends of the titanium-nickel alloy foil 2 are gripped and pulled, whereby the titanium-nickel alloy foil 2
Is given a predetermined amount of distortion. The strained titanium-nickel alloy foil 2 is immersed in a mixed aqueous solution of hydrofluoric acid and nitric acid to remove an oxide film formed on the surface of the titanium-nickel alloy foil 2. The alloy foil 2 is anodized with a sodium hydroxide solution. Thereby, an anodic oxide film is generated on the surface of the titanium-nickel alloy foil 2. It has been experimentally found that this anodized film has a function of improving the adhesion performance of the titanium-nickel alloy foil 2.

It is also possible to perform a titanium coating treatment on the surface from which the oxide film has been removed, and further a surface treatment so as to form a chemical conversion film by performing a chemical conversion coating treatment. Preferably, the titanium coating is formed by an ion plating method. Then, a resin material is applied on the anodic oxide film or the chemical conversion film of the titanium-nickel alloy foil 2.

On the other hand, for the film having the resin sheet 5 and the copper foil 6, a circuit diagram for extracting a signal from the strain gauge using the resin ink 7 on the surface of the copper foil 6 is drawn and etched with a ferric chloride solution. By removing the portion drawn by the resin ink 7, the lead wire 7b is formed. The strain gauges 4 are arranged at the respective strain gauge mounting portions 7a of the electric circuit so as to face in the same direction.

Next, a film having an electric circuit 3 to which a strain gauge 4 is connected is adhered on a resin material applied to one surface of the titanium-nickel alloy foil 2 via an adhesive, and the titanium-nickel alloy foil 2 and the film are integrally joined.
Thereby, the damage detection sensor 1 is manufactured.

Next, a composite panel incorporating the damage detection sensor 1 will be described with reference to FIGS. In FIG. 5, reference numeral 10 denotes a composite panel according to the present invention. The composite panel 10 is configured by disposing a plurality of damage detection sensors 1, 1,... Between fiber-reinforced resin layers 11, 11. .

Each of the damage detection sensors 1 is arranged between the fiber reinforced resin layers 11 in a state where strain is applied at room temperature, that is, in a state where strain is maintained at a temperature lower than the transformation point. Each fiber reinforced resin layer 11 is formed by laminating a plurality of prepregs of fiber reinforced resin, and is cured by heating in a state where the titanium-nickel alloy foil 2 is restrained so as not to shrink. Further, by using this heating, the adhesive for bonding the resin sheet 5 to which the electric circuit 3 is bonded and the titanium-nickel alloy foil 2 can be cured.

As shown in FIG. 1, the damage detection sensor 1 is disposed on a titanium-nickel alloy foil 2, an electric circuit 3 bonded to one surface of the titanium-nickel alloy foil 2, and the electric circuit 3. And a strain gauge 4.

The titanium-nickel alloy foil 2 constituting the damage detection sensor 1 generally has the property of reversibly returning to the original crystal structure state by external heat, and the low-temperature martensite phase has a high temperature. About 1/3 to 1/3 softer than the stable austenite phase and easy to deform, the rigidity increases about 2 to 3 times from low temperature to high temperature, and pre-strain is applied to restrain the deformation. In this case, on the contrary, it has a characteristic that a large recovery force of about 2 to 3 times can be obtained.

In the composite panel 10 of the present invention, the damage detection sensor 1 is disposed between the fiber reinforced resin layers 11 in a state where the deformation is restrained at a temperature lower than the transformation point. By heating the alloy foil 2 to a temperature equal to or higher than the transformation point to change the shape, a shear stress is generated in each layer of the composite material, thereby generating a stress for suppressing delamination (delamination).

The composite material panel 10 is specifically shown in FIG.
As shown in the figure, six fiber-reinforced resin layers 11b, 11c,
11d, 11e, 11f, 11g and five damage detection sensors 1b, 1c, 1d, 1e, 1f, 6
The fiber reinforced resin layers 11b and 11g located on the end side of the fiber reinforced resin layers are formed by laminating two carbon fiber reinforced resins, and the fiber reinforced resin layer 11 located in the middle is formed.
c, 11d, 11e, and 11f are formed by laminating three carbon fiber reinforced resins, and the damage detection sensors 1b, 1
c, 1d, 1e, and 1f1 are converted to fiber-reinforced resin layers 11b and 11
c, 11d, 11e, 11f, and 11g11.

Next, a method of controlling damage to the composite panel 10 will be described. Each damage detection sensor 1b, 1c, 1
Reference numerals d, 1e, and 1f denote a configuration having the titanium-nickel alloy foil 2 and the electric circuit 3 shown in FIG. 1. By passing a weak constant current through the titanium-nickel alloy foil 2, cracks are generated inside the composite material. Occurs, local distortion occurs in the titanium-nickel alloy foil 2, and this distortion causes
The electric resistance of the nickel alloy foil 2 changes.

That is, when delamination occurs in the composite material panel 10 as shown in FIG. 6, the stress applied to the fiber reinforced resin layer 11e or the stress caused by the stress concentration when the fiber reinforced resin layer 11 is damaged. The balance is changed, and the change in the stress balance is sensed as distortion of the titanium-nickel alloy foil 2 of the damage detection sensors 1d and 1e, and the change in the distortion is detected by the titanium-nickel alloy foil 2.
Changes in the electrical resistance due to the change in the shape. Therefore,
By detecting which of the plurality of damage detection sensors 1b, 1c, 1d, 1e, 1f arranged in the composite material panel 10 has changed the electrical resistance of the titanium-nickel alloy foil 2, the composite material panel 10 Throat fiber reinforced resin layer 11
It is possible to detect whether or not b, 11c, 11d, 11e, 11f, and 11g are damaged.

In the composite panel 10 shown in FIG. 6, if delamination occurs in the fiber reinforced resin layer 11e, the titanium-nickel alloy foils 2 of the damage detection sensors 1d and 1e sandwiching the fiber reinforced resin layer 11e. 2 and the electric resistance of the titanium-nickel alloy foil 2 of the other damage detection sensor also changes. Depending on the degree of damage, damage detection sensor 1
The electrical resistance between the titanium-nickel alloy foils 2 and 2 of d and 1e changes rapidly. At this time, the damage detection sensor 1
By applying a current to the titanium-nickel alloy foils 2 and 2 of d and 1e, delamination of the layers constituting the fiber-reinforced resin layer 11e can be prevented.

Next, a description will be given of a method of detecting a damage position of a composite material using the damage detection sensor shown in FIG. A titanium-nickel alloy foil 2, an electric circuit 3 bonded to one surface of the titanium-nickel alloy foil 2, and a plurality of strain gauges 4 arranged in the same direction at predetermined intervals in the electric circuit 3.
Is provided between the fiber reinforced resin layers 11 and 11 in a state where distortion is applied at normal temperature.

Further, an analyzer is provided for measuring and analyzing the amount of strain detected by the strain gauge, and the analyzer is made to store in advance the amount of strain of the plurality of strain gauges which varies depending on the damaged part and store them as strain patterns in advance. Put.

Next, the strain gauge 4 of the damage detection sensor 1
Calculates the strain pattern by relativizing the detected strain amount, and compares the calculated strain pattern with a strain pattern stored in advance in the analysis device to specify a damaged portion generated in the composite material.

For example, when a reinforcing fiber of the fiber reinforced resin layer 11 of the composite material is cut in a direction perpendicular to the direction of the transversal crack stress and a crack is generated, the amount of strain detected by the strain gauge 4 surrounding the crack is greatly increased. . Then, the magnitude of the damage can be determined from the magnitude of the distortion.

When delamination occurs,
On the one hand, the above-mentioned stress can be distinguished from the normal damage because of the discontinuity in which the value of the strain gauge surrounding the damaged part increases on the one hand and decreases on the other. Then, since a strain value due to the influence of the damage position appears on the strain gauge surrounding the damaged portion, the position and size of the damage can be specified in the same manner as in the case of the damage in the perpendicular direction.

As an example of the distortion pattern, an iso-distortion diagram can be used. In this case, the amount of distortion at each point is measured at predetermined time intervals and further compared to determine the maximum point and the maximum value. After that, the distortion value of each point is divided by the maximum value, and the relative value to the maximum value is stored as the value of each point. In this state, an iso-strain line is obtained by using a relative value, and an accurate damage position can be obtained by obtaining the iso-strain line by simulation in advance and comparing it with an iso-strain diagram stored in an analyzer. . Alternatively, the center of the iso-distortion diagram obtained simply from the measured values may be used as the damage point.

Another method of estimating the damage position is as follows.
When estimating the position of the delamination on the plane, for example, three lines arranged in one direction including a strain gauge showing the maximum strain value
A quadratic curve is derived from the strain gauges and their strain values, and the maximum strain point is obtained. Then, a straight line Y passing through the maximum point and orthogonal to the direction in which the three strain gauges are arranged is determined. In the same manner as above, a quadratic curve is derived in a direction orthogonal to the one direction, a maximum strain point is obtained, and a straight line X passing through the maximum strain point and parallel to the one direction is obtained. Then, the intersection of the straight lines X and Y is estimated as the damage position on the plane. When transversal cracks enter, the position of the strain gauges on both sides of the crack rapidly rises, so that the position is easily determined.

In the normal case, it is often unnecessary to specify both the location and the size accurately. Therefore, the damaged part is estimated from the strain gauge showing the maximum strain, and the magnitude of the damage is calculated from the sum of the strain values around the damaged part. Can also be estimated.

Thus, the strain amount detected by each strain gauge corresponding to the damaged part of the composite material is made relative to the strain amount of a plurality of strain gauges that vary depending on the damaged part by experiment or finite element analysis to form a strain pattern. It is stored in the analyzer, the strain pattern is calculated by relativizing the amount of strain of the strain gauge generated in the composite material, and the calculated strain pattern is compared with the strain pattern stored in the analyzer in advance. The damage site which occurs in can be specified. Or
The damaged site can be estimated from the measured strain pattern.

Further, if the output voltage is constantly monitored, it is possible to detect the damage inside the material by the change. By preliminarily testing and examining the change in voltage in the event of damage, if the change in voltage is stored in a computer, damage can be detected if there is an output equal to the damage. For example, if the normal pattern with no damage changes, damage can be detected by the appearance of a strain gauge that shows a greatly changed output than other parts, and the area near the strain gauge or the area surrounded by multiple strain gauges can be detected. If is assumed to be the damaged site, the damaged site can be estimated.

That is, the relationship between damage of different types, positions and sizes, such as transversal cracks and delaminations, and the electrical resistance generated in the composite material 10 and the distribution of the electrical resistance, and the distribution of the electrical resistance are grasped, so that the composite material 10 is generated. The type, location and size of the damage can be estimated.

FIG. 7 is a diagram showing the effect of the composite material obtained by laminating the shape memory alloys. In FIG. 7, the horizontal axis represents the strain (%),
The vertical axis is Transverse crack density (/ cm),
A white point indicates a composite material laminated with a shape memory alloy having a 2% permanent strain, and a black point indicates a composite material having no shape memory alloy. FIG.
According to the report, 0.4% of composite material laminated with shape memory alloy
It can be seen that the occurrence of the transversal crack is suppressed in the state where the distortion is given.

[0050]

The damage detection sensor according to the present invention has a titanium-
By arranging the strain gauge on the electric circuit bonded to one surface of the nickel alloy foil, it is possible to detect a damaged portion generated in the composite material when applied to the composite material.

The method for manufacturing the damage detection sensor of the present invention comprises:
After removing the oxide film from the strained titanium-nickel alloy foil, anodizing treatment is performed to form an anodic oxide film, so that the adhesion performance between the nickel alloy foil and the film having the electric circuit in which the strain gauges are connected. Can be increased.

The method for manufacturing the damage detection sensor according to the present invention comprises:
After removing the oxide film from the strained titanium-nickel alloy foil and forming a chemical conversion film by chemical conversion coating, adhesion between the titanium-nickel alloy foil and the film having an electric circuit in which the strain gauges are bonded. Performance can be enhanced.

According to the composite material of the present invention, a composite material capable of detecting damage and a damaged position can be obtained by disposing a damage detection sensor between fiber-reinforced resin layers in a state where strain is applied at ordinary temperature. In addition, titanium-
By utilizing the shape recovery function of the nickel alloy foil and the damage suppressing function, the progress of damage can be suppressed.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a damage detection sensor according to the present invention.

FIG. 2 is a sectional view taken along the line II of FIG. 1;

FIG. 3 is a diagram showing an electric circuit formed from a film having a resin sheet and a copper foil.

FIG. 4 is an exploded perspective view showing another embodiment of the damage detection sensor according to the present invention.

FIG. 5 is a perspective view of a composite material according to the present invention.

FIG. 6 is a view showing delamination of a composite material according to the present invention.

FIG. 7 is a view showing an effect of a composite material in which shape memory alloys are laminated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Damage detection sensor 2 Titanium-nickel alloy foil 3 Electric circuit 4 Strain gauge 10 Composite panel 11 Fiber reinforced resin layer

Claims (8)

[Claims] (1) a titanium-nickel alloy foil;
A damage detection sensor having an electric circuit adhered to one surface of a nickel alloy foil and a strain gauge arranged in the electric circuit. 2. The damage detection sensor according to claim 1, wherein the strain gauges are arranged in the same direction at predetermined intervals, and an independent output unit is provided for each strain gauge. 3. The damage detection sensor according to claim 1, wherein the electric circuit forms a Wheatstone bridge, and a strain gauge is arranged in the electric circuit. 4. The damage detection sensor according to claim 3, wherein adjacent strain gauges are arranged in directions orthogonal to each other. 5. A titanium-nickel alloy foil having a predetermined amount of strain, an oxide film is removed from the strained titanium-nickel alloy foil with a mixed aqueous solution of hydrofluoric acid and nitric acid, and the titanium-nickel alloy foil having the oxide film removed therefrom. A damage detection sensor characterized in that a nickel alloy foil is anodized with a sodium hydroxide solution, and a film having an electric circuit coupled with a strain gauge is attached on the anodized titanium-nickel alloy foil. Production method. 6. A titanium-nickel alloy foil having a predetermined amount of strain, an oxide film is removed from the titanium-nickel alloy foil with the strain by a mixed aqueous solution of hydrofluoric acid and nitric acid, and the titanium-nickel alloy foil is removed. Damage detection sensor characterized by performing a titanium coating treatment on the surface of a nickel alloy foil, further subjecting to a chemical conversion coating treatment, and attaching a film having an electric circuit with a strain gauge on the titanium coating subjected to the chemical conversion coating treatment. Manufacturing method. 7. A composite material, wherein the damage detection sensor according to claim 1 is disposed between fiber-reinforced resin layers in a state where strain is applied at normal temperature. 8. The composite material according to claim 7, wherein the damage detection sensor and the fiber reinforced resin layer are laminated.