Mechanoluminescence optical fiber, preparation method thereof and distributed stress sensing system

Abstract

The invention discloses a mechanoluminescence optical fiber, a preparation method thereof and a distributed stress sensing system, and relates to the technical field of mechanoluminescence. The mechanoluminescence optical fiber is of a three-layer coaxial cylindrical structure and sequentially comprises a mechanoluminescence core layer, a light transmission cladding layer and a low-refractive-index coating layer from inside to outside. Wherein the mechanoluminescence core layer is a cylinder prepared from polymethyl methacrylate and mechanoluminescence powder, the light transmission cladding is a polymethyl methacrylate layer and wraps the mechanoluminescence core layer, and the low-refractive-index coating layer is low-refractive-index glue; the mechanoluminescence core layer generates an optical signal under the action of an external force, and a part of the optical signal is captured by a waveguide formed by the optical transmission cladding and the low-refractive-index coating layer and is transmitted along the optical transmission cladding. According to the invention, a double-cladding optical fiber structure in which the core layer emits light and the first cladding layer transmits is adopted, so that effective collection and transmission of optical signals are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanoluminescence, and in particular to a mechanoluminescent optical fiber and a preparation method thereof, and a distributed stress sensing system. Background Art

[0002] Stress sensors are widely used in robotics, infrastructure health monitoring, security and other fields. Among them, stress sensors based on mechanoluminescent materials have received more attention in recent years. Due to its distributed, visual, passive standby and other characteristics, its application prospects are bright.

[0003] At present, the stress sensing system based on mechanoluminescent materials mainly adopts the scheme of evenly laying mechanoluminescent materials on the measured surface, and then monitoring the luminescent materials through a photoelectric detection array or a high-speed camera. Under this scheme, when the measured surface is partially subjected to internal or external mechanical forces, the mechanoluminescent materials in the corresponding area emit light, and the detection system detects the change in the light field distribution and obtains the stress distribution. The method for realizing distributed perimeter security based on stress luminescent film disclosed in the Chinese invention patent with publication number CN115691019A adopts this scheme. This scheme has high requirements for the detector and is easily affected by environmental interference. If the optical fiber transmission scheme is adopted, the mechanoluminescent material is combined with the optical fiber to construct a mechanoluminescent optical fiber that can emit light under the action of force and can transmit the generated light along the optical fiber, which will effectively support the design of the stress sensing system. The Chinese invention patent with publication number CN116449482A discloses a flexible mechanoluminescent multi-core optical fiber and its preparation method and shape sensing system, which provides an idea of ​​mechanoluminescent optical fiber, but its structure of external light emission and internal transmission is not conducive to the collection of optical signals. Therefore, it is very important to develop a more suitable mechanoluminescent optical fiber and sensing system. Summary of the invention

[0004] In view of the above problems, the present invention discloses a mechanoluminescent optical fiber and its preparation method and a distributed stress sensing system, which adopts a double-cladding optical fiber structure with core layer luminescence and first cladding transmission to achieve effective collection and transmission of optical signals.

[0005] A mechanoluminescent optical fiber proposed according to the purpose of the present invention is a multi-layer coaxial cylindrical structure, which comprises a mechanoluminescent core layer, a light transmission cladding layer and a low-refractive index coating layer from the inside to the outside; wherein the mechanoluminescent core layer is a cylinder made of polymethyl methacrylate and mechanoluminescent powder, the light transmission cladding layer is a polymethyl methacrylate layer wrapped around the mechanoluminescent core layer, and the low-refractive index coating layer is a low-refractive index glue; the mechanoluminescent core layer generates an optical signal under the action of an external force, a part of which is captured by a waveguide composed of the light transmission cladding layer and the low-refractive index coating layer, and is transmitted along the light transmission cladding layer.

[0006] Preferably, the cross-sectional diameter of the mesoluminescent core layer is 10um-2mm, and the cross-sectional outer diameter of the light transmission cladding layer is 200um-5mm. The cross-sectional outer diameter of the light transmission cladding layer is larger than the cross-sectional diameter of the mesoluminescent core layer. Considering the characteristics of the optical fiber, the limit value is limited here, and the relationship between the core and the cladding is not shown. The thickness of the low refractive index coating layer is 1um-1mm.

[0007] The present invention further discloses a method for preparing the above-mentioned mechanoluminescent optical fiber, comprising the following steps:

[0008] Step 1: Mix polymethyl methacrylate and mesoluminescent powder to polymerize into a bulk material, and process it into a rod shape.

[0009] Step 2: embed the rod-shaped material processed in step 1 into the polymethyl methacrylate tube, and require the two to be coaxial and fixed to form a preformed rod.

[0010] Step 3: Melt the preform rod by heating, and stretch it along its axial direction to produce an optical fiber with a two-layer structure.

[0011] Step 4: Coat the outer surface of the two-layer optical fiber with a low refractive index glue to form a mesoluminescent optical fiber.

[0012] Preferably, in step 1, the volume proportion of the mechanoluminescent powder is 1%-60%.

[0013] The present invention further discloses a distributed stress sensing system, comprising the above-mentioned mesoluminescent optical fiber, a supporting unit, a connecting optical fiber and a detector; the mesoluminescent optical fiber is a plurality of optical fibers arranged vertically and horizontally to form a grid; the supporting unit comprises an upper layer of the supporting unit and a lower layer of the supporting unit respectively arranged above and below the grid-shaped mesoluminescent optical fiber; the connecting optical fiber is a plurality of optical fibers arranged corresponding to the mesoluminescent optical fiber, and is used to connect the mesoluminescent optical fiber and the detector.

[0014] Preferably, the support unit is made of plastic or metal.

[0015] Compared with the prior art, the advantages of the mechanoluminescent optical fiber and its preparation method and the distributed stress sensing system disclosed in the present invention are:

[0016] 1. The present invention adopts a double-clad optical fiber structure with core layer luminescence and first cladding transmission, thereby achieving effective collection and transmission of optical signals.

[0017] 2. The present invention has a simple structure, high fluorescence collection efficiency, and a preparation process that is consistent with the mature plastic optical fiber process, and can be prepared at low cost and in large quantities. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is the longitudinal cross-section of the electroluminescent optical fiber.

[0020] Figure 2 This is the transverse cross-section of the electroluminescent optical fiber.

[0021] Figure 3 This is the structural diagram of the sensing unit of the distributed stress sensing system.

[0022] Figure 4 This is the structural diagram of the distributed stress sensing system.

[0023] In the figure: 1- low refractive index coating layer; 2- light transmission cladding; 3- mesoluminescent core layer; 4- upper layer of support unit; 5- lower layer of support unit; 6- mesoluminescent optical fiber; 7- connecting optical fiber; 8- detector. DETAILED DESCRIPTION

[0024] The specific implementation of the present invention is briefly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Figure 1-Figure 4 The preferred embodiments of the present invention are shown and analyzed in detail.

[0026] like Figure 1 , 2 The mechanoluminescent optical fiber 6 shown is a three-layer coaxial cylindrical structure, which is composed of a mechanoluminescent core layer 3, a light transmission cladding layer 2 and a low refractive index coating layer 1 from the inside to the outside. The mechanoluminescent core layer 3 is a cylindrical structure made of polymethyl methacrylate and SrAl2O4:Eu,Dy mechanoluminescent powder, with a cross-sectional diameter of 200um and a particle size of 500 mesh to 250 mesh. The light transmission cladding layer 2 is a polymethyl methacrylate layer, which is wrapped around the mechanoluminescent core layer 3 and has a cross-sectional outer diameter of 1mm. The low refractive index coating layer 1 is a 131 low refractive index glue provided by JENHNLEY, which is coated on the outside of the light transmission cladding layer 2 and has a thickness of 100um. The mechanoluminescent core layer 3 generates an optical signal under the action of an external force, a part of which is captured by the waveguide formed by the light transmission cladding layer 2 and the low refractive index coating layer 1, and is transmitted along the light transmission cladding layer 2.

[0027] The present invention further discloses a method for preparing the above-mentioned mesoluminescent optical fiber 6, which is a melt drawing method, which specifically includes the following steps:

[0028] Step 1: Mix polymethyl methacrylate and SrAl2O4:Eu,Dy mesoluminescent powder to polymerize them into a bulk material, wherein the volume proportion of SrAl2O4:Eu,Dy mesoluminescent powder is 30%, and process it into a rod with a diameter of 10 mm and a length of 500 mm.

[0029] Step 2: embed the rod-shaped material processed in step 1 into a polymethyl methacrylate tube with an inner diameter of 10 mm, an outer diameter of 50 mm, and a length of 500 mm. The two tubes are required to be coaxial and fixed to form a preformed rod.

[0030] Step 3: Melt the preform rod by heating, and stretch it along its axial direction to produce an optical fiber with a two-layer structure.

[0031] Step 4: low refractive index glue is coated on the outside of the two-layer optical fiber to form a mechanoluminescent optical fiber 6. The mechanoluminescent core layer 3 of the finally formed mechanoluminescent optical fiber 6 has a cross-sectional diameter of 200 um, a cross-sectional outer diameter of the light transmission cladding 2 is 1 mm, and a low refractive index coating layer 1 is 100 um thick.

[0032] The present invention further discloses a distributed stress sensing system, such as Figure 3 , 4 As shown, it includes the above-mentioned mesoluminescent optical fiber 6, a support unit, a connecting optical fiber 7 and a detector 8. The mesoluminescent optical fiber 6 is a plurality of fibers arranged vertically and horizontally to form a grid shape, and the mesh size is 10mm*10mm. The support unit includes a support unit upper layer 4 and a support unit lower layer 5 respectively arranged above and below the grid-shaped mesoluminescent optical fiber 6. The material of the support unit is a transparent PVC sheet, which is elastic and can be restored to its original state after the force is released. The thickness of the support unit upper layer 4 and the support unit lower layer 5 are both 1mm. The connecting optical fiber 7 is a plurality of fibers arranged for the mesoluminescent optical fiber 6, which are used to connect the mesoluminescent optical fiber 6 and the detector 8. Each mesoluminescent optical fiber 6 has a separate number, and the detector 8 is an APD detector 8. After the support plate is partially deformed by the force, the force is transmitted to the mesoluminescent optical fiber 6, causing it to emit light. The detector 8 detects the change in the intensity of the light signal and feeds back the magnitude of the force. At the same time, by comparing the luminescence intensity of the mesoluminescent optical fibers 6 with different numbers, the position of the force point can be detected.

[0033] According to experiments, the constructed mechanoluminescent optical fiber 6 can generate fluorescence under stress, which is collected by the light transmission cladding 2 and then transmitted axially. The constructed stress sensing system based on the mechanoluminescent optical fiber 6 can detect the magnitude and position of stress.

[0034] The above description of the disclosed embodiments enables those skilled in the art to implement and use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit and scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A mechanoluminescent optical fiber, characterized in that: The invention is a multi-layer coaxial cylindrical structure, which comprises, from the inside to the outside, a mesoluminescent core layer (3), a light transmission cladding layer (2) and a low refractive index coating layer (1); wherein the mesoluminescent core layer (3) is a cylinder made of polymethyl methacrylate and mesoluminescent powder, the light transmission cladding layer (2) is a polymethyl methacrylate layer wrapped around the mesoluminescent core layer (3), and the low refractive index coating layer (1) is a low refractive index glue; the mesoluminescent core layer (3) generates a light signal under the action of an external force, a part of which is captured by a waveguide formed by the light transmission cladding layer (2) and the low refractive index coating layer (1), and is transmitted along the light transmission cladding layer (2).

2. The mechanoluminescent optical fiber according to claim 1, characterized in that: The cross-sectional diameter of the electroluminescent core layer (3) is 10um-2mm, the cross-sectional outer diameter of the light transmission cladding (2) is 200um-5mm, and the thickness of the low refractive index coating layer (1) is 1um-1mm.

3. A method for preparing the mechanoluminescent optical fiber according to claim 1, characterized in that: The following steps are involved: Step 1: Mix polymethyl methacrylate and mesoluminescent powder to polymerize into a bulk material, and process the bulk material into a rod shape; Step 2: insert the rod-shaped material processed in step 1 into the polymethyl methacrylate tube, and require the two to be coaxial and fixed to form a preformed rod; Step 3, melting the preform rod by heating, and stretching it along its axial direction to produce an optical fiber with a two-layer structure; Step 4: Coat the outer surface of the optical fiber with a two-layer structure with a low refractive index glue to form a mesoluminescent optical fiber (6).

4. The method according to claim 3, characterized in that In step 1, the volume proportion of the mechanoluminescent powder is 1%-60%.

5. A distributed stress sensing system, characterized in that: It comprises the mechanoluminescent optical fiber (6) as claimed in claim 1, a supporting unit, a connecting optical fiber (7) and a detector (8); the mechanoluminescent optical fiber (6) is a plurality of optical fibers arranged vertically and horizontally to form a grid; the supporting unit comprises an upper supporting unit layer (4) and a lower supporting unit layer (5) respectively arranged above and below the grid-shaped mechanoluminescent optical fiber (6); the connecting optical fiber (7) is a plurality of optical fibers arranged corresponding to the mechanoluminescent optical fiber (6) and used to connect the mechanoluminescent optical fiber (6) and the detector (8).

6. A distributed stress sensing system according to claim 5, characterized in that: The support unit is made of plastic or metal.

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