Dual-mode coaxial fiber sensor capable of simultaneously measuring temperature and deformation rate, its manufacturing method and measurement system

Abstract

To provide a dual-mode coaxial fiber sensor which is capable of simultaneously measuring temperature and strain to compensate for a strain error caused by temperature changes using a single sensor and without using a separate temperature measurement sensor, and which has a structure that does not act as a defect even when used inside a composite material as an insertion type.SOLUTION: A dual-mode coaxial fiber sensor disclosed herein has a structure consisting of a core fiber, a strain sensing layer formed on the core fiber and made of a conductive material, and a temperature sensing layer formed on a surface of the strain sensing layer and made of a conductive material that are stacked together. Such an arrangement enables simultaneous measurement of temperature and strain using one sensor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a dual-mode coaxial fiber sensor capable of simultaneously measuring temperature and deformation rate, a manufacturing method thereof, and a measurement system. [Background technology]

[0002] Fiber-reinforced composite materials are new materials made by mixing ultra-high-strength fiber materials, such as carbon fiber, with polymer materials, such as epoxy. Among fiber-reinforced composite materials, carbon fiber-reinforced composite materials are extremely lightweight yet have high strength compared to metal materials, such as steel and aluminum, which have been used as existing structural materials. Therefore, fiber-reinforced composite materials are suitable for applications that require lightweight yet high structural strength. For this reason, research and development into the application of carbon fiber-reinforced composite materials is actively underway.

[0003] Carbon fiber reinforced composite materials have been mainly used in the military and aviation fields, and in particular, in the civil aviation field, they have been successfully used to design lightweight structures for the fuselage and main components of passenger aircraft, and their use is rapidly increasing.

[0004] As the development and spread of electric vehicles has accelerated due to the recent acceleration of carbon neutrality, attempts are underway to apply carbon fiber reinforced composite materials not only in the aviation field but also in the exterior materials of vehicle bodies and battery packs. As a clear example, major German automobile manufacturers are actively introducing carbon fiber reinforced composite materials to reduce the weight of vehicle bodies, and domestic companies are also using carbon fiber reinforced composite panels as reinforcing materials to protect the battery packs of electric vehicles, and the number of proven cases is gradually increasing.

[0005] Despite this trend, however, the application of carbon fiber reinforced composite materials has not been accelerated. One of the main reasons for this is that the properties of composite materials, which are a mixture of different materials (fiber materials and polymer resins), can change significantly depending on the manufacturing conditions. Therefore, it is necessary to use various sensors to measure the deformation that occurs during the manufacturing process, and based on this, the manufacturing process for each part must be optimized.

[0006] Fiber Bragg Grating sensors have been commonly used to monitor existing composite manufacturing processes, but to compensate for deformation rate errors caused by temperature changes, a separate temperature measurement sensor such as a thermocouple or an encapsulated FBG sensor is required to use the fiber Bragg grating sensor for temperature measurement.

[0007] However, commonly used temperature measurement sensors are excessively large, ranging from several hundred μm to several mm in size. When such sensors are inserted into composite materials, they act as defects, reducing the reliability of the entire structure after manufacturing. Summary of the Invention [Problem to be solved by the invention]

[0008] The present disclosure provides a dual-mode coaxial fiber sensor that can simultaneously measure temperature and deformation rate so that errors in deformation rate due to temperature changes can be compensated for with a single sensor without a separate temperature measurement sensor, and has a structure that does not act as a defect even when used as an insertion type inside a composite material, as well as a manufacturing method and measurement system for the same. [Means for solving the problem]

[0009] According to one aspect, a dual-mode coaxial fiber sensor includes a core fiber and a plurality of coating layers sequentially stacked on the core fiber, the plurality of coating layers including a deformation rate measurement layer formed on the core fiber and made of a conductive material, and a temperature measurement layer formed on the deformation rate measurement layer and made of a conductive material.

[0010] The plurality of coating layers may further include an elastic polymer layer coating a surface of the deformation rate measurement layer, and the temperature measurement layer may be formed on the elastic polymer layer.

[0011] The dual-mode coaxial fiber sensor may have a structure in which a portion of the deformation rate measuring layer is exposed through a slit formed on a surface of a portion of the elastic polymer layer, forming a junction between the deformation rate measuring layer and the temperature measuring layer, and measuring a thermoelectric voltage generated at the junction to measure temperature.

[0012] The slits can be created using a solvent or a laser.

[0013] The slits can be created through the laser intensity and transfer speed being set so as not to damage the elastomeric polymer layer.

[0014] The plurality of coating layers may further include an elastic polymer layer coating a surface of the temperature measurement layer.

[0015] The plurality of coating layers may further include an elastic polymer layer coating the surface of the core fiber, and the deformation rate measuring layer may be formed on the surface of the elastic polymer layer formed on the surface of the core fiber.

[0016] According to another feature, a dual-mode coaxial fiber sensor can be manufactured, the dual-mode coaxial fiber sensor including the steps of: manufacturing a core fiber for a dual-mode coaxial fiber sensor; coating the core fiber with a deformation rate measurement layer made of a conductive material; coating the deformation rate measurement layer with an elastic polymer layer; removing a portion of a surface of the elastic polymer layer to form a slit exposing a portion of the deformation rate measurement layer; and coating the elastic polymer layer with a temperature measurement layer, wherein a junction point between the deformation rate measurement layer and the temperature measurement layer is formed through the slit, and the dual-mode coaxial fiber sensor can be manufactured, the dual-mode coaxial fiber sensor being capable of measuring temperature through a thermoelectric voltage measured at the junction.

[0017] After the step of coating with the temperature measurement layer, the method may further include the step of coating the surface of the temperature measurement layer with an elastic polymer layer.

[0018] The method may further include coating a surface of the core fiber with an elastic polymer layer between the manufacturing step and the coating step with the deformation rate measuring layer.

[0019] The step of coating the temperature measurement layer may be performed by using a freshwater coating method, in which the elastic polymer layer is coated with a conductive polymer solution including at least one of PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), polypyrrole (PPY), polyaniline (PANI), and silver nanowire dispersion solution.

[0020] The step of forming the slits may involve removing a portion of the surface of the elastic polymer layer using a solvent or a laser.

[0021] The solvent may include at least one of ethyl alcohol, acetone, N,N-dimethyl formamide, tetrahydrofuran, and butanone.

[0022] The laser may include at least one of a CO2 laser, a neodymium (Nd) laser, and a neodymium yttrium-aluminum-garnet (Nd:YAG) laser.

[0023] The step of forming the slit may include forming the slit by adjusting a cutter intensity of the laser and a head moving speed of the laser.

[0024] According to still another feature, the measurement system includes a dual-mode coaxial fiber sensor in which a core fiber, a deformation rate measurement layer, an elastic polymer layer, and a temperature measurement layer are sequentially stacked, and a slit is formed by removing a portion of the surface of the elastic polymer layer to expose a portion of the deformation rate measurement layer; a deformation rate measurement unit connected to the deformation rate measurement layer and measuring a change in resistance due to deformation of the deformation rate measurement layer; and a temperature measurement unit connected to the temperature measurement layer and measuring a thermoelectric voltage generated at a junction between the temperature measurement layer and the deformation rate measurement layer over the slit due to a temperature difference between the temperature measurement layer and the deformation rate measurement layer when a temperature change occurs in the temperature measurement layer, and measuring a temperature from the thermoelectric voltage.

[0025] The measurement system further includes a first electrode and a second electrode, one end of which is connected to the deformation rate measurement layer and the other end of which is connected to the deformation rate measurement unit, and the deformation rate measurement unit can measure the resistance between the first electrode and the second electrode and calculate the deformation rate from the measured resistance.

[0026] The measurement system further includes a third electrode having one end connected to the temperature measurement layer and the other end connected to the temperature measurement unit, and the temperature measurement unit is connected to the second electrode and the third electrode, and when the temperature of the temperature measurement layer changes, a voltage generated at the junction due to a temperature difference between the temperature measurement layer and the deformation rate measurement layer can be measured through the second electrode and the third electrode. [Effects of the Invention]

[0027] According to the present disclosure, a fiber-type sensor that can simultaneously measure temperature and deformation rate using a single sensor can be manufactured. Therefore, when the sensor is inserted into a composite material, there is an advantage in that a separate temperature measurement sensor does not need to be installed to compensate for deformation rate errors caused by temperature changes. Therefore, compared to existing deformation rate monitoring systems based on optical fiber sensors, it is possible to stably measure deformation rate without acting as a defect within a composite material structure. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a perspective exploded view of a dual-mode coaxial fiber sensor structure according to an embodiment. FIG. [Figure 2] FIG. 2 is an exploded side view of the dual-mode coaxial fiber sensor of FIG. 1. [Figure 3] FIG. 1 is a configuration diagram of a measurement system for a dual-mode coaxial fiber sensor according to an embodiment. [Figure 4] 1 is a flowchart illustrating a manufacturing process of a dual-mode coaxial fiber sensor according to an embodiment. [Figure 5] 4A to 4C are illustrative views illustrating a process for forming a first elastic polymer layer according to an embodiment of the present invention. [Figure 6] 10A to 10C are exemplary diagrams illustrating a process of forming a deformation rate measurement layer according to an embodiment. [Figure 7] FIG. 4 is an exemplary view illustrating a process for forming a second elastic polymer layer according to an embodiment. [Figure 8] 10 is a flowchart illustrating a joint manufacturing process through the formation of a narrow gap between a deformation rate measurement layer and a temperature measurement layer according to an embodiment. [Figure 9] 9 is an exemplary diagram illustrating laser driving for manufacturing the joint of FIG. 8. FIG. [Figure 10] 9 is an exemplary view showing a deformation rate measuring layer exposed to the outside through the formation of a slit in FIG. 8; [Figure 11] 10A to 10C are exemplary diagrams illustrating a process of forming a temperature measurement layer according to an embodiment. [Figure 12] FIG. 4 is an exemplary view illustrating a process for forming a third elastic polymer layer according to an embodiment. [Figure 13] The results of surface analysis of the dual-mode coaxial fiber sensor under different laser driving conditions are shown. [Figure 14] 1 shows the resistance characteristics of the dual-mode coaxial fiber sensor before and after the slit forming process. [Figure 15] The sensing response characteristics of a dual-mode coaxial fiber sensor with a slit are shown. [Figure 16] The sensing response characteristics are shown for 1K cycles. [Figure 17] The characteristics of the sensing response to the deformation rate level are shown. [Figure 18] The analysis results of the temperature measurement characteristics of the dual-mode coaxial fiber sensor over time are shown. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be embodied in various different forms and is not limited to the embodiments described herein. In addition, in order to clearly explain the present disclosure in the drawings, parts that are not relevant to the description are omitted, and similar parts are designated by similar reference numerals throughout the specification.

[0030] Throughout the specification, when a part "comprises" any element, this does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified.

[0031] In this specification, expressions in the singular may be construed as singular or plural unless expressly stated as "one" or "single".

[0032] Herein, like reference numerals refer to like elements regardless of the drawings, and "and / or" includes each and every combination of one or more of the referenced elements.

[0033] In this specification, terms including ordinal numbers, such as "first," "second," etc., may be used to describe various components, but the components are not limited by these terms. These terms are used only to distinguish one component from another. For example, a first component may be designated a second component, and similarly, a second component may be designated a first component, without departing from the scope of the present disclosure.

[0034] In the flowcharts described herein with reference to the drawings, the order of operations may be changed, some operations may be combined, some operations may be split, and certain operations may not be performed.

[0035] FIG. 1 is an exploded perspective view of a dual-mode coaxial fiber sensor structure according to an embodiment, and FIG. 2 is an exploded side view of the dual-mode coaxial fiber sensor of FIG.

[0036] Referring to Figures 1 and 2, the dual-mode coaxial fiber sensor 100 is a dual-mode sensor including a temperature measurement mode and a strain measurement mode, and is configured to be able to measure temperature and strain simultaneously.

[0037] The dual-mode coaxial fiber sensor 100 has a structure in which a core fiber 101, a first elastomer layer 102, a strain sensing layer 103, a second elastomer layer 104, a temperature sensing layer 105, and a third elastomer layer 106 are sequentially stacked.

[0038] Referring to Figure 2, the core fiber 101 is located at the innermost position, and as we move towards the outer layers, a first elastic polymer layer 102, a deformation rate measurement layer 103, a second elastic polymer layer 104, a temperature measurement layer 105, and a third elastic polymer layer 106 are stacked around the inside.

[0039] The dual-mode coaxial fiber sensor 100 has a fiber core 101 located at the innermost portion.

[0040] The fiber core 101 may be made of a polymeric material with high strength and rigidity, for example, an ultra-high-molecular-weight polyethylene (UHMWPE)-based material.

[0041] The surface of the fiber core 101 is coated with a first elastomeric polymer layer 102 .

[0042] A deformation rate measurement layer 103 is formed on the surface of the first elastic polymer layer 102. The deformation rate measurement layer 103 may be a conductive layer with a multi-layer structure, i.e., a multi-conductive layer. For example, the deformation rate measurement layer 103 may have a structure in which three layers are stacked.

[0043] According to one embodiment, the multi-conductive layer may be fabricated by stacking layers having different concentrations of conductive particles.

[0044] According to another embodiment, the multi-conductive layer may be fabricated by stacking layers using different conductive particles, for example, layers using graphene and CNTs (carbon nanotubes).

[0045] The surface of the deformation rate measurement layer 103 is coated with a second elastic polymer layer 104 .

[0046] The surface of the second elastic polymer layer 104 is coated with a temperature measurement layer 105 for measuring thermoelectric voltage. The temperature measurement layer 105 may be a conductive polymer layer.

[0047] The surface of the temperature measurement layer 105 is coated with a third elastic polymer layer 106 .

[0048] As described above, the dual-mode coaxial fiber sensor 100 has a coaxial structure including a plurality of coating layers formed through a freshwater coating method.

[0049] The dual-mode coaxial fiber sensor 100 comprises a three-layer elastic polymer structure surrounding a deformation rate measurement layer 103 and a temperature measurement layer 105 .

[0050] Here, a slit 107 is formed in a portion of the second elastic polymer layer 104 by processing using a solvent or laser, and the deformation rate measuring layer 103 is exposed through the slit 107, creating a junction point 108 where the deformation rate measuring layer 103 and the temperature measuring layer 105 meet.

[0051] The temperature can be measured by measuring the thermoelectric voltage generated at the junction 108 .

[0052] FIG. 3 is a configuration diagram of a measurement system of a dual-mode coaxial fiber sensor according to an embodiment.

[0053] Referring to FIG. 3, the measurement system 200 may include the dual-mode coaxial fiber sensor 100 , a plurality of electrodes 201 , 202 , 203 , a deformation rate measurement unit 204 , and a temperature measurement unit 205 .

[0054] The measurement system 200 can simultaneously measure the deformation rate and temperature using only a plurality of electrodes, that is, three electrodes 201, 202, and 203.

[0055] Among the plurality of electrodes 201 , 202 , and 203 , the first electrode 201 has one end connected to the deformation rate measuring layer 103 and the other end connected to a deformation rate measuring unit 204 .

[0056] The second electrode 202 has one end connected to the deformation rate measuring layer 103 and the other end connected to the deformation rate measuring unit 204 .

[0057] When deformation occurs in the deformation rate measurement layer 103 due to an external load such as tension, compression, or impact, the electrical network changes, causing a change in the resistance between the first electrode 201 and the second electrode 202 .

[0058] At this time, the deformation rate measuring unit 204 can measure the change in resistance between the first electrode 201 and the second electrode 202 to measure the deformation rate occurring in the deformation rate measuring layer 103 .

[0059] The temperature measurement unit 205 is connected to the second electrode 202 and the third electrode 203. The third electrode 203 has one end connected to the temperature measurement unit 203 and the other end connected to the temperature measurement layer 105.

[0060] At this time, a joint 108 is formed in the narrow gap 107 between the deformation rate measurement layer 103 and the temperature measurement layer 105 .

[0061] When the temperature of the temperature measurement layer 105 changes, a temperature difference occurs between the temperature measurement layer 105 and the deformation rate measurement layer 103, and this temperature difference changes the electrical network, causing a thermoelectric effect at the junction 108.

[0062] At this time, the temperature measuring unit 205 measures the thermoelectric voltage between the second electrode 202 connected to one end of the junction 108 and the third electrode 203 connected to the other end of the junction 108, and converts the measured thermoelectric voltage into temperature, thereby measuring the temperature.

[0063] As described above, the structure of the dual-mode coaxial fiber sensor 100 according to the embodiment of the present invention allows not only measurement of the deformation rate but also measurement of the temperature by measuring the thermoelectric voltage at the junction 108 at the same time.

[0064] In addition, since the second electrode 202 is shared when measuring the thermoelectric voltage, the structure can be simplified. Such a simplified structure provides the effect of reducing manufacturing costs.

[0065] FIG. 4 is a flowchart illustrating a manufacturing process of a dual-mode coaxial fiber sensor according to an embodiment, FIG. 5 is an exemplary diagram illustrating a process for forming a first elastic polymer layer according to an embodiment, FIG. 6 is an exemplary diagram illustrating a process for forming a deformation rate measurement layer according to an embodiment, FIG. 7 is an exemplary diagram illustrating a process for forming a second elastic polymer layer according to an embodiment, FIG. 8 is a flowchart illustrating a process for manufacturing a joint by forming a gap between the deformation rate measurement layer and the temperature measurement layer according to an embodiment, FIG. 9 is an exemplary diagram illustrating laser driving for manufacturing the joint of FIG. 8, FIG. 10 is an exemplary diagram showing the deformation rate measurement layer exposed to the outside through the formation of a gap of FIG. 8, FIG. 11 is an exemplary diagram illustrating a process for forming a temperature measurement layer according to an embodiment, and FIG. 12 is an exemplary diagram illustrating a process for forming a third elastic polymer layer according to an embodiment.

[0066] Referring to Fig. 4, first, a core fiber 101 is manufactured (S101). Here, the core fiber 101 may be made of an ultrahigh molecular weight polyethylene (UHMWPE) material.

[0067] In S101, ultra-high molecular weight polyethylene solution can be utilized to produce core fibers.

[0068] Next, the surface of the core fiber 101 is coated with a first elastic polymer layer 102 (S102).

[0069] 5, in S102, the core fiber 101 may be immersed in an elastomer solution to perform dip coating, where the elastomer solution may be a water-based polyurethane coating solution.

[0070] In S102, the process of immersing the core fiber 101 in the elastomeric polymer solution, removing it, and drying it in an oven at 80°C for 3 minutes is repeated three times, thereby coating the surface of the core fiber 101 with a first elastomeric polymer layer 102.

[0071] Next, a deformation rate measurement layer 103 for measuring the deformation rate is formed on the surface of the first elastic polymer layer 102 (S103).

[0072] In step S103, referring to FIG. 6, in order to provide measurement characteristics, i.e., to form a deformation measurement layer 103, a core fiber (elastomer coated fiber) 101 coated with a first elastomer layer 102 can be immersed in a water-dispersed coating solution of MWCNTs (multi-walled carbon nanotubes) to perform dip coating.

[0073] In S103, the core fiber 101 coated with the first elastomeric polymer layer 102 is immersed in an MWCNT aqueous dispersion coating solution, then removed and dried in an oven at 80°C for 3 minutes. This process is repeated three times to form a deformation rate measurement layer 103 for measuring deformation rate on the surface of the first elastomeric polymer layer 102. Subsequently, the deformation rate measurement layer 103 is dried in an oven at 80°C for 1 hour to remove excess moisture.

[0074] Next, the surface of the deformation rate measurement layer 103 is coated with the second elastic polymer layer 104 (S104).

[0075] 7, in S104, the core fiber (strain sensing layer coated fiber) 101 coated with the first elastomer layer 102 and the deformation rate measuring layer 103 may be immersed in an elastomer solution to perform dip coating. At this time, a water-based polyurethane coating solution may be used as the elastomer solution.

[0076] In S104, the core fiber 101 coated with the first elastic polymer layer 102 and the deformation rate measurement layer 103 is immersed in a water-based polyurethane coating solution, then removed and dried in an oven at 80°C for 3 minutes. This process is repeated three times, thereby coating the second elastic polymer layer 104 on the surface of the deformation rate measurement layer 103.

[0077] Next, a portion of the second elastic polymer layer 104 is removed to form a slit 107 (S105), and the surface of the deformation rate measuring layer 103 inside is exposed through the slit .

[0078] In S105, according to one embodiment, a solvent may be used to remove a portion of the second elastic polymer layer 104. The solvent may be at least one of ethyl alcohol, acetone, N,N-dimethyl formamide, tetrahydrofuran, and butanone.

[0079] In S105, according to another embodiment, a laser may be used to remove a portion of the second elastic polymer layer 104. The laser may be at least one selected from the group consisting of a CO laser, a neodymium (Nd) laser, and a neodymium yttrium-aluminum-garnet (Nd:YAG) laser.

[0080] At this time, the strength and speed of the laser cutter are adjusted to prevent the deformation rate measuring layer 103 from being broken, and a portion of the second elastic polymer layer 104 can be removed to form the slit 108 .

[0081] If the laser is irradiated perpendicularly to the surface immediately, the second elastic polymer layer 104 will be damaged, so it is important to control the speed of the laser head quickly to remove only a portion of the surface while preventing damage.

[0082] According to an embodiment, the laser source can be adjusted to an intensity of 10-40W.

[0083] The laser head movement speed can be selected within the range of 40-50 mm / s.

[0084] Referring to Figures 8 and 9, the intensity and movement speed of the laser head are controlled so that the amount of energy applied per time to a portion of the surface of the second elastic polymer layer 104 is uniform (S201), and the surface of a portion of the second elastic polymer layer 104 is removed through such operation of the laser head (S202).

[0085] Referring to FIG. 10, it can be seen that a portion of the surface of the second elastic polymer layer 104 is removed through the operation of the laser head, thereby partially exposing the deformation rate measuring layer 103.

[0086] According to an experiment, by adjusting the laser head to 20 W and 46 mm / s, the slit 107 can be formed by removing only a portion of the surface while preventing the second elastic polymer layer 104 from breaking.

[0087] Next, a temperature measurement layer 105 for measuring temperature is coated on the surface of the second elastic polymer layer 104 in which the slits 107 are formed, and a bonding portion 108 is formed between the deformation rate measurement layer 103 and the temperature measurement layer 105 (S106).

[0088] In S106, as shown in FIG. 11, the sensor 100 having the slit 108 formed therein can be coated with a conductive polymer solution to form a junction 108 between the deformation rate measuring layer 103 and the temperature measuring layer 105.

[0089] Here, the conductive polymer solution can be at least one of PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), polypyrrole (PPY), polyaniline (PANI), and silver nanowire dispersion solution.

[0090] In S106, the sensor 100 with the slits 107 formed therein is immersed in a PEDOT:PSS coating solution and then dried in an oven at 80° C. for 3 minutes. This process can be repeated 15 times. Then, the temperature measurement layer 105 can be dried in an oven at 80° C. for 1 hour to remove excess moisture.

[0091] Finally, the surface of the temperature measurement layer 105 is coated with a third elastic polymer layer 106 (S107).

[0092] Referring to FIG. 12, the sensor 100 coated with the temperature measurement layer 105 is immersed in an elastomer solution, then immersed in a water-based polyurethane coating solution, and then removed and dried in an oven at 80°C for 3 minutes. This process is repeated three times, thereby coating the third elastomer layer 106 on the surface of the temperature measurement layer 105.

[0093] Through the manufacturing process described above, it is possible to measure not only the deformation rate by measuring the change in resistance due to deformation of the sensor 100, but also the temperature by measuring the thermoelectric voltage generated at the junction 108 between the deformation rate measurement layer 103 and the temperature measurement layer 105.

[0094] In addition, to provide the deformation rate measurement function, a shell is formed by sequentially layering an elastomer layer and a multi-conductive layer, which is a multi-layered conductive layer formed by coating a conductive particle-based coating solution on the surface of a polymer fiber core with high strength and rigidity. When the sensor 100 is inserted into a composite structure, the deformation rate can be measured by measuring the change in resistance of the conductive layer due to external loads such as tension, compression, and impact.

[0095] The present invention will be described in detail below through experimental examples, which are merely for illustrative purposes and are not intended to limit the scope of the present invention.

[0096] Experimental example

[0097] An experiment was conducted to analyze the surface of the dual-mode coaxial fiber sensor 100 after the slit formation process. The surface morphology and damage of the deformation rate measurement layer 103, from which part of the second elastic polymer layer 104 had been removed, were investigated using an optical microscope and Raman spectroscopy, respectively.

[0098] To investigate the effect of the slit forming process on the fabrication of the joint 108 and the temperature measurement layer 106, an experiment was conducted to analyze changes in the resistance and measurement characteristics of the dual-mode coaxial fiber sensor 100. At this time, electronic test equipment was used to measure the deformation sensitivity, i.e., gauge factor, over various deformation ranges and to perform a cycling test.

[0099] The thermoelectric voltage change was analyzed in various temperature and deformation ranges.

[0100] First, Figure 13 shows the surface analysis results of the dual-mode coaxial fiber sensor depending on the laser driving conditions.

[0101] Referring to FIG. 13, the results of analyzing the surface of the second elastic polymer layer 104 after removing a portion of the second elastic polymer layer 104 by setting various laser driving conditions are shown.

[0102] The laser driving conditions were such that the intensity of the laser head was fixed at 20 W, and the laser head movement speed was varied to analyze the area where the second elastic polymer layer 104 was removed (laser exposure area). That is, the influence of the laser movement speed on the surface morphology and slit formation was analyzed.

[0103] The moving speed of the laser head was gradually decreased to 50 mm / s, 48 ​​mm / s, 46 mm / s, and 44 mm / s, and the changes occurring on the surface of the second elastic polymer layer 104 as a result were analyzed.

[0104] Analysis showed that the surface of the second elastomeric polymer layer 104 was roughened by laser exposure, and slits 107 were formed when the laser speed was reduced from 50 mm / s to 42 mm / s.

[0105] When the laser head moving speed was faster than 50 mm / s, the surface morphology of the second elastic polymer layer 104 did not change, which is believed to be because the energy was insufficient to remove the second elastic polymer layer 104.

[0106] In addition, when the laser head moving speed was slower than 42 mm / s, the dual-mode coaxial fiber sensor 100 was damaged.

[0107] Therefore, it was confirmed that the appropriate laser speed range for forming the slit 107 without damaging the surface is 50 mm / s to 42 mm / s.

[0108] At this time, when the laser head moving speed reached 46 mm / s, it was confirmed that a portion of the surface of the second elastic polymer layer 104 was removed, exposing the internal deformation rate measuring layer 103. The size of the exposed portion was confirmed to be approximately 14 μm.

[0109] When the laser head moving speed was 44 mm / s, the size of the exposed portion was approximately 17 μm, and it was confirmed that the surface of the second elastomeric polymer layer 104 was excessively removed, leaving residue (residue PU (outer polyurethane) layer) on the surface of the sensor.

[0110] Therefore, the experiment confirmed that the optimum condition for the laser head transfer speed was set to 46 mm / s.

[0111] FIG. 14 shows the resistance characteristics of the dual-mode coaxial fiber sensor before and after the slit forming process.

[0112] 14, the resistance measurement results for the sensor 100 show that the average resistance before the junction fabrication was 14.5 kΩ and the average resistance after the junction fabrication was 14.9 kΩ. Therefore, even though the slits 107 were formed using a laser, the average resistance before and after the junction fabrication was similar, which confirmed that the laser process did not affect the internal deformation rate measurement layer 103.

[0113] FIG. 15 shows the sensing response characteristics of the dual-mode coaxial fiber sensor with slit formation.

[0114] At this time, FIG. 15(A) shows the characteristics of the relative resistance change according to the deformation rate, and FIG. 15(B) shows the characteristics of the gauge factor before and after the slit forming process.

[0115] Referring to FIG. 15(A), it can be seen that the measurement characteristics due to strain, that is, the analysis result of the change in relative resistance, maintains a linear response characteristic even after slit processing.

[0116] Referring to Figure 15 (B), the gauge factor before the slit formation (a) is 4.12, and the gauge factor after the slit formation (b) is 4.20, so it was confirmed that there was no significant change in the gauge factor even after the slit formation process.

[0117] Therefore, it can be seen from FIGS. 14 and 15 that the deformation rate measuring layer 103 is not deteriorated by forming the slits using a laser.

[0118] Next, an experiment was carried out to evaluate the durability of the dual-mode coaxial fiber sensor 100.

[0119] FIG. 16 shows the characteristics of the sensing response according to 1K cycles, and FIG. 17 shows the characteristics of the sensing response with respect to the deformation level, particularly the characteristics of the change in relative resistance with time for each deformation level.

[0120] 16 shows the evaluation results of repeatability of the dual-mode coaxial fiber sensor 100. As a result of analyzing the sensing response over 1,000 cycles, it was confirmed that the resistance change and thermoelectric voltage from the deformation rate measuring layer 103 were both stably measured over more than 1,000 cycles.

[0121] The dual-mode coaxial fiber sensor 100 maintains its cyclic stability because, even though the slit 107 is formed in the second elastic polymer layer 104, the portion corresponding to the slit 107 is coated with the temperature measurement layer 105. Furthermore, the third elastic polymer layer 106 can prevent physical damage to the temperature measurement layer 105 and the joint 108.

[0122] Subsequently, it was confirmed through Figure 17 that stable measurements were possible even when the experiment was carried out while the magnitude of the applied deformation rate was successively increased to 10%, 20%, 30%, and 40% of the breaking elongation rate of the dual-mode coaxial fiber sensor 100.

[0123] Referring to FIG. 17, when the fracture deformation rate was set in various ranges of 10% to 40%, it was confirmed that the change in resistance could be stably measured in various deformation rate ranges without degradation.

[0124] As a result, even if a gap 107 is formed in the second elastic polymer layer 104 through laser processing, the gap 107 is filled through the temperature measurement layer 105, and since the third elastic polymer layer 106 is also formed on the outermost periphery, it can be confirmed that repeated measurement stability is maintained.

[0125] FIG. 18 shows the analysis results of the temperature measurement characteristics of the dual-mode coaxial fiber sensor over time.

[0126] Referring to FIG. 18, when the signal detected from the dual-mode coaxial fiber sensor 100 was measured while the temperature was increased by 30°C from 0°C to 125°C, it was confirmed that the thermoelectric voltage (TE* voltage) and the resistance indicating the deformation rate were stably measured along the temperature cycle.

[0127] Therefore, it can be confirmed that the deformation rate and temperature can be measured simultaneously using only the dual-mode coaxial fiber sensor, i.e., a single sensor, without a separate temperature measurement sensor.

[0128] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these examples, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the claims below also fall within the scope of the present invention.

Claims

1. core fiber, and a plurality of coating layers sequentially stacked on the core fiber; the plurality of coating layers include a deformation rate measuring layer formed on the core fiber and made of a conductive material, and a temperature measuring layer formed on the deformation rate measuring layer and made of a conductive material; the plurality of coating layers further include an elastic polymer layer coating a surface of the deformation rate measurement layer, the temperature measurement layer is formed on the elastic polymer layer, a slit formed on a surface of a portion of the elastic polymer layer exposes a portion of the deformation rate measurement layer, thereby forming a joint between the deformation rate measurement layer and the temperature measurement layer; The dual-mode coaxial fiber sensor is configured to measure the temperature by measuring the thermoelectric voltage generated at the junction.

2. The plurality of coating layers are The dual-mode coaxial fiber sensor according to claim 1 , further comprising an elastic polymer layer coating a surface of the temperature measurement layer.

3. The plurality of coating layers are The core fiber further includes an elastic polymer layer coated on the surface thereof, 3. The dual-mode coaxial fiber sensor according to claim 2, wherein the deformation rate measurement layer is formed on a surface of the elastic polymer layer formed on the surface of the core fiber.

4. fabricating a core fiber for a dual-mode coaxial fiber sensor; coating the core fiber with a deformation rate measuring layer made of a conductive material; coating the deformation rate measurement layer with an elastic polymer layer; removing a portion of the surface of the elastic polymer layer to form a slit that exposes a portion of the deformation rate measurement layer; and coating the elastic polymer layer with a temperature measurement layer; A method for manufacturing a dual-mode coaxial fiber sensor, wherein a junction is formed between the deformation rate measurement layer and the temperature measurement layer through the gap, and the temperature can be measured through a thermoelectric voltage measured at the junction.

5. After the step of coating with the temperature measurement layer, The method of claim 4 , further comprising the step of coating a surface of the temperature measurement layer with an elastomeric polymer layer.

6. The method of claim 5 , further comprising the step of coating the surface of the core fiber with an elastic polymer layer between the manufacturing step and the coating step with the deformation rate measurement layer.

7. The step of coating with the temperature measurement layer includes:

5. The method of claim 4, wherein the elastic polymer layer is coated with a conductive polymer solution including at least one of PEDOT:PSS (poly(3,4-ethylenedioxythiophene)polystyrenesulfonate), polypyrrole (PPY), polyaniline (PANI), and a silver nanowire dispersion solution using a freshwater coating method.

8. The step of forming the slit comprises: The method of claim 4 , wherein a solvent or a laser is used to remove a portion of the surface of the elastic polymer layer.

9. The solvent is 9. The method of claim 8, comprising at least one of ethyl alcohol, acetone, N,N dimethylformamide, tetrahydrofuran, and butanone.

10. The laser is 9. The method of claim 8, comprising at least one of a CO2 laser, a neodymium (Nd) laser, and a neodymium yttrium aluminum garnet (Nd:YAG) laser.

11. The step of forming the slit comprises: The method of claim 8, wherein the slit is formed by adjusting the cutter power of the laser and the head translation speed of the laser.

12. a dual-mode coaxial fiber sensor in which a core fiber, a deformation rate measurement layer, an elastic polymer layer, and a temperature measurement layer are sequentially laminated, and a surface of the elastic polymer layer is partially removed to form a slit exposing a portion of the deformation rate measurement layer; a deformation rate measuring unit connected to the deformation rate measuring layer and measuring a change in resistance due to deformation of the deformation rate measuring layer; and a temperature measurement unit connected to the temperature measurement layer, which measures a thermoelectric voltage generated at a junction between the temperature measurement layer and the deformation rate measurement layer on the gap due to a temperature difference between the temperature measurement layer and the deformation rate measurement layer when a temperature change occurs in the temperature measurement layer, and measures a temperature from the thermoelectric voltage.

13. a first electrode and a second electrode, one end of which is connected to the deformation rate measurement layer and the other end of which is connected to the deformation rate measurement unit; The deformation rate measurement unit The measurement system of claim 12 , wherein the resistance between the first electrode and the second electrode is measured, and the deformation rate is determined from the measured resistance.

14. a third electrode having one end connected to the temperature measurement layer and the other end connected to the temperature measurement unit; The temperature measurement unit 14. The measurement system of claim 13, wherein the second electrode and the third electrode are connected to each other, and when the temperature of the temperature measurement layer changes, a voltage generated at the junction due to a temperature difference between the temperature measurement layer and the deformation rate measurement layer is measured through the second electrode and the third electrode.

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