KR101396202B1 - Structural health monitoring system of fiber reinforced composites including conductive nano-materials, the monitoring and the manufacturing method of the same, and structural health monitoring system of wind turbine blade including conductive nano-materials, the manufacturing method of the same - Google Patents

Abstract

The present invention can be applied not only to the deformation of each fiber-reinforced composite sheet, but also to the deformation of each fiber-reinforced composite sheet by stacking the fiber-reinforced composite sheets on which the sensor layers are formed by spraying conductive nanomaterials on the surface of the fiber- There is an advantage that the peeling phenomenon between the laminated fiber-reinforced composite sheets can be judged quickly and accurately.

Description

TECHNICAL FIELD [0001] The present invention relates to a structure health monitoring system for a fiber reinforced composite including a conductive nanomaterial, a monitoring method and a manufacturing method thereof, and a structure health monitoring system for a fiber for a wind turbine including a conductive nanomaterial, composites including conductive nano-materials, the monitoring and the manufacturing method of the same, and structural health monitoring systems of wind turbine blade including conductive nano-materials, the manufacturing method of the same}

The present invention relates to a structural integrity monitoring apparatus for a fiber reinforced composite including a conductive nanomaterial, a monitoring method and a manufacturing method thereof, and a structure health monitoring apparatus for a blade for a wind turbine including a conductive nanomaterial, and a manufacturing method thereof More particularly, the present invention relates to a structural integrity monitoring apparatus for a fiber reinforced composite including a conductive nanomaterial capable of measuring a change in electric resistance through conductive nanoparticles and thereby monitoring separation or cracks between a plurality of glass fiber- , A monitoring method and a manufacturing method thereof, and a structure health monitoring apparatus for a blade for a wind power generation including a conductive nanomaterial and a manufacturing method thereof.

Generally, the most widely used techniques for diagnosing the health of aircraft or bridges are visual inspection, acoustic emission (AE), eddy current, ultrasound, X-ray radiography ), Etc., and inspections are conducted periodically. Since these structures are inspected according to a fixed schedule irrespective of the state, built-in sensors are being introduced in recent years because labor costs are more than necessary and losses are caused by the use time of the structures due to the inspection. Commonly used sensors include ceramic-based piezoelectric sensors, strain gages, optical fibers, and surface acoustic wave sensors. These sensors have high accuracy, sensitivity, reliability, etc. However, there is a problem that it is difficult to grasp the stress / deformation state of the structure as a whole due to the point where the sensing element is attached, that is, only the local sensing (Point sensing) is possible.

In addition, when a composite sheet is laminated on a blade of an aircraft or a blade for a wind power generator and the like, peeling or cracks occur between the composite sheets, which is very complicated and troublesome, There is a problem in that it can not be promptly dealt with because it can not be grasped immediately when peeling or cracking occurs.

KR 10-2012-0050740 A

It is an object of the present invention to provide a structural integrity monitoring apparatus for a fiber reinforced composite including a conductive nanomaterial capable of grasping a deformation state of a structure more quickly and accurately, a monitoring method and a manufacturing method thereof, and a wind turbine including a conductive nanomaterial And to provide a structure health monitoring apparatus for a blade and a manufacturing method thereof.

The structural integrity monitoring apparatus of a fiber reinforced composite including a conductive nanomaterial according to the present invention includes a nonconductive matrix, a plurality of fiber-reinforced composite sheets stacked in the matrix, and at least one of the plurality of fiber- A plurality of electrodes disposed to be spaced apart from each other along the periphery of the sensor layer; a resistance meter for measuring a resistance value between the electrodes; And a computer for comparing the resistance values measured by the resistance meter and determining the deformation state of the fiber-reinforced composite sheets according to the resistance change value.

The method for fabricating a structural integrity monitoring apparatus for a fiber reinforced composite including a conductive nanomaterial according to the present invention includes the steps of: applying a conductive nanomaterial to one or a plurality of fiber- To form a sensor layer, connecting a plurality of electrodes to the sensor layer in pairs, and supplying the non-conductive matrix material to the fiber-reinforced composite sheet.

The method of monitoring the structural integrity of a fiber reinforced composite including a conductive nanomaterial according to the present invention includes the steps of connecting a plurality of electrodes along a periphery of a fiber reinforced composite sheets to which conductive nanomaterials are added and laminated in a nonconductive matrix, The method comprising the steps of: measuring a change in resistance of pairs of electrodes connected to one another among a plurality of electrodes connected to the fiber-reinforced composite sheet; comparing the resistance value measured in the step and a previously stored resistance value; And determining a state of deformation of the first member.

A structure health monitoring apparatus for a blade for a wind turbine including a conductive nanomaterial according to the present invention includes a nonconductive matrix, a plurality of fiber-reinforced composite sheets stacked in the matrix, and a plurality of fiber- And a sensor layer formed by spraying conductive nanomaterials on one or a plurality of fiber-reinforced composite sheets requiring monitoring, a plurality of electrodes spaced from each other along the circumference of the sensor layer, A resistance meter for measuring resistance values of pairs of electrodes connected to each other among the electrodes, a computer for comparing a resistance value measured in advance with the resistance value measured by the resistance meter, and determining a deformation state of the blade according to a resistance change value .

A method for manufacturing a structural health monitoring apparatus for a blade for a wind turbine including a conductive nanomaterial according to the present invention includes the steps of: fabricating a blade mold; and one or more of a plurality of fiber- Reinforced composite sheets, the method comprising the steps of: adding conductive nanomaterials to the fiber-reinforced composite sheets; laminating the fiber-reinforced composite sheets to the blade mold; And a step of injecting a nonconductive matrix material into the fiber-reinforced composite sheets to which the plurality of electrodes are connected to cure, and then removing the blade mold.

The present invention can be applied not only to the deformation of each glass fiber reinforced sheet but also to the deformation of each glass fiber reinforced sheet by forming a sensor layer by spraying conductive nanomaterials on the surface of the glass fiber reinforced sheet and laminating the glass fiber- There is an advantage that the peeling phenomenon between the laminated glass fiber reinforced sheets can be judged quickly and accurately.

The present invention has an advantage that the deformation state of the fiber-reinforced composite can be determined more quickly and accurately even with a resistance value obtained with a small number of electrodes.

INDUSTRIAL APPLICABILITY The present invention has an advantage in that cracking or peeling of a blade of a wind power generator in which a glass fiber reinforced sheet is laminated can be monitored in real time.

The present invention has the advantage that the conductive nanomaterials improve bonding strength and bonding strength between the laminated sheets and the resin.

1 is a view showing a strain measuring apparatus according to an embodiment of the present invention.
Fig. 2 is a schematic view showing a manufacturing method of the strain measuring apparatus shown in Fig. 1. Fig.
3 is a control block diagram for strain measurement according to an embodiment of the present invention.
4 is a flowchart showing a strain measurement method according to an embodiment of the present invention.
5 is a graph showing the measured resistance change in the three-point bending test according to the embodiment of the present invention.
Figure 6 is a graph showing the measured resistance change at break of a fiber reinforced composite according to an embodiment of the present invention.
7 is a block diagram illustrating a method of manufacturing a blade for a wind turbine according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 to 3, a structural integrity monitoring apparatus for a fiber-reinforced composite including a conductive nanomaterial according to an embodiment of the present invention includes a strain measuring apparatus 1 for monitoring the structural integrity of a fiber- ), For example.

The strain measuring apparatus 1 includes a fiber reinforced composite sheet, a nonconductive matrix, a sensor layer 40, an electrode 20, a resistance meter 50, and a computer 60.

The above-described fiber-reinforced composite sheet is exemplified by the glass fiber-reinforced sheet 10 being used. However, the present invention is not limited thereto, and it is of course possible to use a sheet made of nonconductive fibers such as kevlar fibers and polyethylene fibers in addition to glass fibers. It is also possible to use a hybrid fiber sheet in which conductive fibers and nonconductive fibers are mixed, and when the hybrid fiber sheet is used, the electrode 20 is connected to the nonconductive fiber. The glass fiber-reinforced sheet 10 is formed by laminating three sheets of first, second, and third glass fiber-reinforced sheets 11, 12, 13, but is not limited thereto. For example, It is of course possible to stack a plurality of sheets other than sheets. The first, second and third glass fiber reinforced sheets 11, 12 and 13 are sheets of glass fibers.

The nonconductive matrix is a part formed by supplying resin or the like to the 1,2,3-glass fiber-reinforced sheets 11, 12, 13 and then curing. Here, the resin is used as a material for forming the matrix. However, the present invention is not limited thereto. For example, It is possible if it is a conductive material.

The sensor layer 40 may be formed on at least one surface of the first, second, and third glass fiber reinforced sheets 11, 12, That is, the sensor layer 40 may be formed on each of the first, second, and third glass fiber-reinforced sheets 11, 12, and 13, It is of course possible to form only the uppermost or the lowermost sheet among the sheets 11, 12, In the present embodiment, the sensor layer 40 is provided on each of the first, second and third glass fiber-reinforced sheets 11, 12 and 13, for example. The sensor layer 40 may be formed on all of the first, second, and third glass fiber-reinforced sheets 11, 12, and 13, .

The sensor layer is formed on the surfaces of the first, second, and third glass fiber-reinforced sheets 11, 12, 13 by a mixture liquid 30 of the conductive nanoparticles 32 and methanol 31, As shown in FIG. Accordingly, the number of the sensor layers 40 corresponds to the number of the first, second, and third glass fiber-reinforced sheets 11, 12, That is, the sensor layer 40 includes a first sensor layer 41 formed on the surface of the first glass fiber-reinforced sheet 11, a second sensor layer 41 formed on the surface of the second glass fiber- And a third sensor layer 43 formed on the surface of the third glass fiber reinforced sheet 13.

The conductive nanomaterials may be carbon nanotubes (CNTs) or graphenes, or may be mixed with the carbon nanotubes or graphenes. Hereinafter, the conductive nanomaterials are referred to as conductive nanoparticles. The conductive nanomaterials may be carbon fibers or the like. Here, the conductive nanoparticles 32 are exemplified by using multi-walled carbon nanotubes (MWCNTs).

The electrode 20 is connected to each of the first, second and third glass fiber-reinforced sheets 11, 12 and 13 in which the first, second and third sensor layers 41, 42 and 43 are formed, do. A plurality of the electrodes 20 are spaced apart from each other along respective circumferences of the first, second, and third glass fiber-reinforced sheets 11, 12, and 13. The plurality of electrodes 20 are connected so as to form two electrode pairs, and the resistance change of the electrode pairs is measured by the resistance meter 50. The plurality of electrodes 20 are electrodes connected to one same glass fiber reinforced sheet to form electrode pairs, and electrodes connected to different glass fiber reinforced sheets are connected to each other.

The resistance meter 50 is connected to the plurality of electrodes 20 to measure the resistance change of the electrode pair of the electrodes 20.

Referring to FIG. 2, a method of manufacturing a strain measuring apparatus according to an embodiment of the present invention will now be described.

First, a predetermined amount of the carbon nanotubes 32 is put into the methanol 31 and mixed appropriately. The ratio of the carbon nanotubes 32 to the methanol 31 is set to an optimum ratio by experiments or the like in advance.

The mixed liquid 30 is sprayed onto the surface of the glass fiber-reinforced sheet 10 prepared in advance. That is, the mixed liquid 30 is sprayed onto the surfaces of the first, second, and third glass fiber-reinforced sheets 11, 12, and 13, respectively.

The first, second and third glass fiber-reinforced sheets 11, 12, and 13 onto which the mixed liquid 30 is sprayed are laminated.

The mixture liquid 30 is sprayed onto the first, second, and third glass fiber-reinforced sheets 11, 12, and 13 formed with the first, second, and third sensor layers 41, 42, And a plurality of electrodes 20 are connected. Here, eight electrodes are connected to one glass fiber reinforced sheet for example. Therefore, a total of 24 electrodes 20 are used for the first, second, and third glass fiber reinforced sheets 11, 12, and 13 of the three sheets.

Then, resin is supplied to the first, second and third glass fiber-reinforced sheets 11, 12 and 13 to which the electrodes 20 are connected to cure. Here, the resin is supplied by using a Vacuum-assisted resin transfer molding (VARTM) method, for example.

Referring to FIG. 4, a strain measuring method using a strain measuring apparatus according to an embodiment of the present invention is described as follows.

The plurality of electrodes 20 are connected to the sensor layer 40 and the sensor layer 40 is divided into a plurality of virtual regions according to the positions of the plurality of electrodes 20. [ The number of virtual regions correlates with the number of electrodes 20. For example, when the size of the virtual zones is too small, there is no electrode path to be described later passing through a specific virtual zone. Therefore, an effective strain value for a specific virtual zone can not be calculated. Thus, the number of virtual zones should be set such that the number of electrode paths passing through that virtual zone is not zero for each virtual zone.

The resistance measuring device 50 is connected to the plurality of electrodes 20 to measure the resistance value between all the electrodes.

The computer 60 compares a measured resistance value of each of the electrode pairs with a previously stored resistance value to calculate a resistance change value DELTA R2. Lt; / RTI >

The computer 60 determines electrode pairs having a resistance change according to the resistance change value? R calculated above and confirms an electrode path connecting the electrode pairs. A virtual region through which the electrode path connecting the electrode pairs having the resistance change passes is calculated and it is judged that the strain is generated in the virtual region calculated. That is, the calculated virtual zone indicates the deformation position (S3)

Further, the computer 60 calculates the strain magnitude according to the measured resistance change value in the calculated virtual zone. The effective strain according to the measured resistance change value is calculated to determine the strain magnitude. The effective strain is calculated by a program stored in the computer 60 and preset by experiments or the like. The effective strain is proportional to the resistance change value and has a correlation with the resistance change value of the electrode paths passing through the calculated virtual zone. Therefore, the deformation magnitude at the deformation position can be obtained. (S4)

Meanwhile, FIG. 5 shows a result of measuring a resistance change value for a three-point bending test on a glass fiber-reinforced composite material.

The three-point bending test was carried out as shown in Fig. 5 (a), and the resistance change was measured as shown in Fig. 5 (b). 5 (b), the first sensor layer 41 of the first glass fiber-reinforced sheet 11 disposed on the upper side and the second glass fiber-reinforced sheet 13 of the third glass fiber- The resistance changes measured in the third sensor layer 43 showed different differences. Since the third glass fiber-reinforced sheet 13 was subjected to tensile deformation, the resistance change value measured in the third sensor layer 43 was a positive number. Since the first glass fiber-reinforced sheet 11 was compressively deformed, the resistance change value measured in the first sensor layer 41 was negative. The resistance change measured in the second sensor layer 42 of the second glass fiber-reinforced sheet 12 positioned between the first glass fiber-reinforced sheet 11 and the third glass fiber- 1 < / RTI > sensor layer 41 and the third sensor layer 43, respectively.

In Fig. 5 (c), the difference in resistance between the longitudinal direction and the lateral direction is shown. The resistance change in the longitudinal direction coinciding with the deformation direction of the glass fiber-reinforced sheets 10 was larger than the resistance change in the lateral direction.

By measuring and comparing the resistance change for each of the laminated glass fiber-reinforced sheets as described above, it is possible to easily grasp the strain occurring in each glass fiber-reinforced sheet. For example, when the resistance change of two adjacent glass fiber-reinforced sheets appears as the same signal, it can be judged that both glass fiber-reinforced sheets are both tensile or all-compressive, and in this case, Can be judged to have been peeled off.

Meanwhile, FIG. 6 shows a result of measuring the resistance change value at the time of failure of the fiber-reinforced composite according to the embodiment of the present invention.

As shown in Fig. 6 (a), the first glass fiber-reinforced sheet 11 disposed on the uppermost side underwent compressive deformation due to bending, and a failure occurred in the central portion A thereof.

6 (b), a first electrode 21 connected to the first glass fiber-reinforced sheet 11 and a second glass fiber-reinforced sheet (not shown) disposed below the first glass fiber- When the resistance change value between the first electrode 22 and the second electrode 22 connected to the second electrode 22 is measured, the resistance increases sharply in the positive direction after about 600 seconds, which is the start point of the breakage. That is, when breakage such as peeling occurs, the electrical connection between the first electrode 21 and the second electrode 22 is cut off, so that the resistance change value increases sharply beyond the set value within a short time . Therefore, if the change rate of the resistance change value between the electrodes connected to the upper and lower adjacent sheets is equal to or higher than the set change rate, it can be determined that breakage such as peeling has occurred.

7 is a block diagram illustrating a method of manufacturing a structural health monitoring apparatus for a blade for a wind turbine according to an embodiment of the present invention.

Referring to FIG. 7, a blade for a wind power generator is composed of a sensor layer 40 and a glass fiber reinforced sheet 10, and the sensor layer 40 serves as a structure health monitoring device.

A method of manufacturing the blade for a wind power generator will now be described.

First, a blade mold for making a blade for a wind power generator is manufactured (S101)

The sensor layer is formed by spraying a mixture of carbon nanotubes and methanol on the surface of the glass fiber reinforced sheet (S102)

A plurality of glass fiber-reinforced sheets having the sensor layer formed thereon are stacked on the blade mold (S103). However, the present invention is not limited thereto, and only a glass fiber- Can be formed. For example, the sensor layer can be formed only on the trailing edge of the blade, which is a vulnerable part where peeling mainly occurs. It is of course also possible to form a sensor layer only on the glass fiber-reinforced sheets disposed on the outer side of the plurality of glass fiber-reinforced sheets, and then laminate them.

The plurality of electrodes are connected along the circumference of the glass fiber-reinforced sheets on which the sensor layer is formed (S104).

Thereafter, the resin is injected and cured, and then the blade mold is removed (S105) (S106)

In the above description, the entire shape of the blade is made of the glass fiber reinforced sheets and the sensor layer can be formed only in the fragile portion. However, the present invention is not limited thereto. Do.

Since the blade for a wind turbine fabricated as described above can measure the resistance change through the electrodes, the structural integrity of the blade can be monitored in real time. Here, the blade for a wind turbine is described as an example. However, the present invention is also applicable to an aircraft, a building, a body armor, etc. using a laminated glass fiber reinforced sheet or the like.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

10: glass fiber reinforced sheet 20: electrode
32: carbon nanotube 40: sensor layer
50: resistance meter 60: computer

Claims (15)

Nonconductive matrix;
Fiber-reinforced composite sheets laminated in the matrix;
A sensor layer formed on at least one of the plurality of fiber reinforced composite sheets, the sensor layer including conductive nanomaterials;
A plurality of electrodes spaced from each other along the circumference of the sensor layer;
A resistance meter for measuring a resistance value between the electrodes;
And a computer for comparing the resistance value measured in advance with the resistance value measured by the resistance meter and determining the deformation state of the fiber-reinforced composite sheets according to the resistance change value. The structural nanofiber- Device. The method according to claim 1,
Wherein the fiber-reinforced composite sheet comprises nonconductive fibers,
Wherein the electrodes comprise conductive nanomaterials connected to the nonconductive fiber. The method according to claim 1,
Wherein the sensor layer includes a conductive nanomaterial formed on a surface of the fiber-reinforced composite sheet. The method according to claim 1,
Wherein the sensor layer comprises a conductive nanomaterial that is locally formed in a portion of the fiber-reinforced composite sheet. Forming a sensor layer by adding conductive nanomaterials to one or a plurality of fiber-reinforced composite sheets requiring monitoring of strain state among a plurality of laminated fiber-reinforced composite sheets;
Coupling a plurality of electrodes to the sensor layer in pairs;
And supplying the non-conductive matrix material to the fiber-reinforced composite sheet. The method for manufacturing a structural integrity monitoring device of a fiber-reinforced composite including the conductive nanomaterial. The method of claim 5,
Further comprising laminating a plurality of fiber-reinforced composite sheets on which the sensor layer is formed, prior to feeding the matrix material. ≪ RTI ID = 0.0 > 21. < / RTI > The method of claim 5,
Further comprising laminating a fiber-reinforced composite sheet on which the sensor layer is formed and one or more fiber-reinforced composite sheets on which the sensor layer is not formed, prior to the step of supplying the matrix material. A method for manufacturing a structural integrity monitoring device for a reinforced composite. The method of claim 5,
Wherein the step of adding the conductive nanomaterials to the fiber-
Mixing the conductive nanomaterials in a solvent in a predetermined ratio,
And spraying a solvent containing the conductive nanomaterials onto the fiber-reinforced composite sheet. The method for manufacturing the fiber-reinforced composite according to claim 1, Connecting the plurality of electrodes along the periphery of the fiber reinforced composite sheets to which the conductive nanomaterial is added and laminated in the nonconductive matrix;
Measuring a resistance change of electrode pairs connected to each other among a plurality of electrodes connected to the fiber-reinforced composite sheet;
Comparing the measured resistance value with a previously stored resistance value, and determining a deformation state of the fiber-reinforced composite sheet according to the resistance change value. The method of claim 9,
Wherein measuring the resistance change of the electrode pairs comprises:
A method for monitoring the structural integrity of a fiber-reinforced composite comprising a conductive nanomaterial, the method comprising measuring a resistance change of electrode pairs between electrodes connected to one and the same fiber-reinforced composite sheet. The method of claim 9,
Wherein measuring the resistance change of the electrode pairs comprises:
Reinforced composite sheets laminated on the upper and lower sides of the fiber-reinforced composite sheets, and measuring the change in resistance of the electrode pairs formed between the upper and lower electrodes, respectively, Health monitoring method. The method of claim 10,
If the resistance change value of the electrode pair connected to one of the same fiber reinforced composite sheet is a positive number,
Wherein the conductive nanomaterial is determined to be compressive deformation when the resistance change value is negative. The method of claim 11,
Reinforced composite sheets, the conductive nanomaterial is determined to be peeled off when the rate of change of the resistance change value of the electrode pairs connected to the different fiber-reinforced composite sheets is greater than or equal to the set change rate. . A conductive nanomaterial is formed by spraying a conductive non-conductive matrix, a plurality of fiber-reinforced composite sheets stacked in the matrix, and one or a plurality of fiber-reinforced composite sheets requiring monitoring of a strain state among the fiber-reinforced composite sheets A blade for wind power generation having a sensor layer;
A plurality of electrodes spaced from each other along the circumference of the sensor layer;
A resistance meter for measuring a resistance value of pairs of electrodes connected to each other among the electrodes;
And a computer for comparing the resistance value measured in advance with the resistance value measured by the resistance meter and determining the deformation state of the blade according to the resistance change value. Fabricating a blade mold;
Adding a conductive nanomaterial to one or a plurality of fiber-reinforced composite sheets requiring monitoring of a strain state among a plurality of fiber-reinforced composite sheets;
Stacking the fiber-reinforced composite sheets on the blade mold;
Coupling a plurality of electrodes to the fiber-reinforced composite sheets laminated to the blade mold;
And a step of removing the blade mold after the non-conductive matrix material is injected into the fiber-reinforced composite sheets to which the plurality of electrodes are connected and cured, thereby manufacturing a structural health monitoring apparatus for a structural member of a blade for a wind turbine .

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