A composite material tensile specimen mold for implanting an optical fiber sensor and a manufacturing process thereof

Abstract

The application discloses a composite material tensile specimen mold for implanting an optical fiber sensor and a preparation process, and particularly relates to the technical field of optical fiber sensors, and comprises a base, a long strip-shaped forming core mold is arranged on the top of the base, all positioning pins are inserted into corresponding mold positioning holes, a concave mold is arranged on the top of the base, the forming core mold is inserted into a positioning groove matched with the concave mold to form a specimen forming cavity, optical fiber guide holes are arranged on the top and bottom of the forming core mold and penetrate the forming core mold, each optical fiber guide hole is connected with a first semicircular fiber guide groove arranged at the bottom of the forming core mold, a second semicircular fiber guide groove is arranged on the base and is matched with the first semicircular fiber guide groove to form a circular channel, at least two groups of pressurizing assemblies are arranged between the concave mold and the base, the optical fiber guide holes on the forming core mold and the circular channel formed with the base provide a protection path for the optical fiber sensor, and the bending and extrusion in the process of layering and compaction are avoided, and the survival rate of implantation is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensor technology, specifically relating to a composite material tensile specimen mold for implanting fiber optic sensors and its preparation process. Background Technology

[0002] With the widespread application of composite materials in high-end equipment fields such as aerospace, wind turbine blades, and new energy vehicles, the demand for accurate monitoring of their internal damage evolution mechanisms is becoming increasingly urgent. The industry urgently needs to acquire the internal strain field distribution of components through implanted fiber optic sensors to replace the traditional surface-mounted strain gauge testing method. The latter not only fails to capture internal strain changes in materials but is also susceptible to data drift due to environmental temperature and humidity interference. However, current laboratory preparation of composite tensile specimens with implanted fiber optic sensors faces three major technical bottlenecks: First, manual pre-embedding methods easily lead to fiber spatial displacement or excessive bending, causing fiber core breakage during layup and compaction, resulting in low sensor survival rates; second, existing molds lack dedicated positioning structures, making it difficult to accurately control the embedding depth of the fiber in the thickness direction of the specimen, leading to deviations in strain measurement values; third, during the hot-pressing process in the curing stage, the lack of an effective fixing mechanism for the sensor easily leads to positional displacement or poor bonding with the matrix interface, affecting measurement reliability.

[0003] Therefore, there is an urgent need to develop a composite material tensile specimen mold with an embedded fiber optic sensor and a preparation method to solve the above problems. Summary of the Invention

[0004] To address the aforementioned issues, this invention discloses a mold and process that enables high-precision positioning, micro-damage implantation, and synchronous molding with the sample for fiber optic sensors, thus solving the problems of low fiber survival rate, poor positional accuracy, and poor interface bonding in traditional methods.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A composite material tensile specimen mold with an implanted fiber optic sensor includes a base, a plurality of vertical positioning pins inserted into the top of the base, a long strip-shaped forming core mold placed on the top of the base, and the tops of all the positioning pins inserted into corresponding mold positioning holes. A concave mold is covered on the top of the base, and the forming core mold is inserted into a positioning groove that matches it to form a specimen forming cavity. Both ends of the forming core mold are provided with fiber optic guide holes that penetrate the forming core mold vertically, and each fiber optic guide hole is connected to a first semi-circular fiber optic guide groove provided at the bottom of the forming core mold. The base has a second semi-circular fiber optic guide groove that is combined with the first semi-circular fiber optic guide groove to form a circular channel, and the connection between the circular channel and the fiber optic guide hole is provided with a rounded corner. At least two sets of pressure components are provided between the concave mold and the base, and the pressure components are located at the edge of the base.

[0007] As a preferred embodiment of the present invention, the base is provided with a silicone pad at the outlet of each circular channel.

[0008] As a preferred embodiment of the present invention, the diameters of the fiber optic guide hole and the circular channel are both 3mm, and the radius of the corner at the connection between the circular channel and the fiber optic guide hole is 1.5mm.

[0009] As a preferred technical solution of the present invention, each set of pressurizing components includes: a countersunk square neck bolt and a nut, wherein the countersunk square neck bolt passes through the die and the base and is threadedly connected to the nut, and the base is provided with a countersunk square neck bolt hole adapted to the head of the countersunk square neck bolt.

[0010] As a preferred embodiment of the present invention, the dimensions of the sample forming cavity formed by the concave mold and the forming core mold conform to any one of the standards ASTM D3090, GB / T 3354-2014, and GB / T 1447-2005.

[0011] A method for preparing a composite tensile specimen with an implanted fiber optic sensor, comprising the following steps:

[0012] S1. After applying acetone release agent to the top of the molding core mold, lay down single layers of carbon fiber one by one.

[0013] S2. After laying several layers of the required carbon fiber monolayer, embed the fiber optic sensor, wherein the two ends of the fiber optic sensor pass through the lower carbon fiber layer and extend into the fiber optic guide hole, and the middle of the fiber optic sensor is placed on the already laid carbon fiber layer.

[0014] S3. Continue to lay several layers of the required carbon fiber single layer, then insert the positioning pin into the base, and then insert the forming core mold into the positioning pin. At the same time, the two ends of the fiber optic sensor are led out from the circular channel formed by the first semicircular fiber guide groove and the second semicircular fiber guide groove. The ends of the fiber optic cables are left on the silicone pad, and the ends of the fiber optic cables are fixed on the silicone pad using high temperature resistant tape.

[0015] S4. After applying acetone release agent to the inner wall of the positioning groove, insert the molding core mold into the positioning groove, insert countersunk square neck bolts at the corresponding positions of the four corners of the base, and tighten the nuts through the connecting die after the countersunk square neck bolts pass through the connecting die, so that the die and the molding core mold evenly press the carbon fiber layer in the sample molding cavity.

[0016] S5. The complete composite tensile specimen mold, together with the carbon fiber layer and the fiber optic sensor, is sent into the curing oven. After heat curing, the mold is removed and demolded to obtain the carbon fiber layup tensile specimen with the fiber optic sensor implanted.

[0017] As a preferred embodiment of the present invention, the carbon fiber monolayer is either unidirectional carbon fiber filament or orthogonal carbon fiber filament, and the carbon fiber monolayer is also either carbon fiber prepreg or pure carbon fiber.

[0018] As a preferred technical solution of the present invention, in step S2, a 1-2mm gap is made at the position of the optical fiber guide hole corresponding to the forming core mold on the carbon fiber single layer, and the pigtail of the optical fiber sensor is guided through the gap to the optical fiber guide hole.

[0019] As a preferred embodiment of the present invention, the pressure on the carbon fiber layer in the sample forming cavity formed by the concave mold and the forming core mold in step S4 is 50N-200N.

[0020] As a preferred embodiment of the present invention, in step S5, the thermosetting temperature of the carbon fiber layup tensile specimen is controlled at 110℃-150℃, and the thermosetting time is 1-4 hours.

[0021] The beneficial effects of this invention are as follows:

[0022] First, the fiber optic guide holes on the molded core and the circular channel formed with the base provide a protective path for the fiber optic sensor, avoiding bending and squeezing during the layup and compaction process, and significantly improving the implantation survival rate.

[0023] Secondly, by utilizing the process design that directly controls the fiber optic embedment depth during the layup process, the fiber optic cable is precisely placed on a specific carbon fiber layer. Combined with the positioning structure of the mold, the positional accuracy of the fiber optic cable in the thickness direction of the sample is ensured, eliminating measurement errors caused by embedment depth deviation.

[0024] Third, by fixing the pigtail to the silicone pad and completing the mold clamping step before heat curing, the movement of the optical fiber is effectively restricted during the curing stage, ensuring the stability of the optical fiber sensor-substrate interface and improving the reliability of the measurement signal. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall tensile specimen mold according to an embodiment of the present invention;

[0026] Figure 2 This is a cross-sectional view of the tensile specimen mold according to an embodiment of the present invention;

[0027] Figure 3 This is an embodiment of the present invention. Figure 2 Enlarged view of point A in the middle;

[0028] Figure 4 This is a schematic diagram of the base in the tensile specimen mold according to an embodiment of the present invention;

[0029] Figure 5This is a photograph of a composite material tensile specimen after the fiber optic sensor was implanted, according to an embodiment of the present invention.

[0030] List of identifiers in attached diagrams:

[0031] 1. Die; 11. Positioning groove; 2. Carbon fiber layup tensile specimen; 3. Molding mandrel; 31. Fiber optic guide hole; 32. First semi-circular fiber guide groove; 33. Mold positioning hole; 4. Fiber optic sensor; 5. Base; 51. Second semi-circular fiber guide groove; 6. Silicone pad; 7. Positioning pin; 8. Countersunk square neck bolt; 9. Nut. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0033] Please see Figure 1-5 A composite material tensile specimen mold with an implanted fiber optic sensor includes a base 5, with several vertical positioning pins 7 inserted into the top of the base 5. A long strip-shaped molding core 3 is placed on the top of the base 5, and the tops of all the positioning pins 7 are inserted into corresponding mold positioning holes 33. A concave mold 1 covers the top of the base 5, and the molding core 3 is inserted into a corresponding positioning groove 11 to form a specimen molding cavity. Both ends of the molding core 3 are provided with fiber optic guide holes 31 that penetrate vertically through the molding core 3, and each fiber optic guide hole 31 is connected to a first semi-circular fiber guide groove 32 located at the bottom of the molding core 3. In the embodiment shown in the attached drawings, the fiber optic guide holes 31 vertically penetrate the molding core 3. The base 5 has a second semi-circular fiber guide groove 51 that, together with the first semi-circular fiber guide groove 32, forms a circular channel, and the connection between the circular channel and the fiber optic guide hole 31 is provided with a rounded corner. A silicone pad 6 is provided at the outlet of each circular channel on the base 5.

[0034] At least two sets of pressure-applying components are provided between the die 1 and the base 5, and the pressure-applying components are located at the edge of the base 5. In the embodiment shown in the attached figure, a set of pressure-applying components is provided at each of the four corners of the base 5. Each set of pressure-applying components includes: a countersunk square neck bolt 8 and a nut 9. The countersunk square neck bolt 8 passes through the die 1 and the base 5 and is threadedly connected to the nut 9. The base 5 has a countersunk square neck bolt hole adapted to the head of the countersunk square neck bolt 8.

[0035] Both the fiber optic guide hole 31 and the circular channel have a diameter of 3mm. The radius of the corner where the circular channel connects to the fiber optic guide hole 31 is 1.5mm to prevent the fiber optic sensor 4 from being bent and damaged.

[0036] The dimensions of the sample forming cavity formed by the concave mold 1 and the forming core mold 3 conform to any one of the standards ASTM D3090, GB / T 3354-2014, and GB / T 1447-2005.

[0037] If the locating pin 7 is cylindrical, the base 5 must have at least two locating pins 7 inserted into it. If the locating pin 7 is prism-shaped, the base 5 must have at least one locating pin 7 inserted into it.

[0038] A method for preparing a composite tensile specimen with an implanted fiber optic sensor, using the aforementioned composite tensile specimen mold, includes the following steps:

[0039] S1. After applying acetone release agent to the top of the molding core mold 3, lay carbon fiber single layers one by one.

[0040] S2. After laying several layers of the required carbon fiber single layer, embed the fiber optic sensor 4, wherein the two ends of the fiber optic sensor 4 pass through the lower carbon fiber layer and extend into the fiber optic guide hole 31, and the middle part of the fiber optic sensor 4 is placed on the already laid carbon fiber layer.

[0041] S3. Continue to lay several layers of the required carbon fiber single layer, then insert the positioning pin 7 into the base 5, and then insert the forming core mold 3 into the positioning pin 7. At the same time, the two ends of the fiber optic sensor 4 are led out from the circular channel formed by the first semi-circular fiber guide groove 32 and the second semi-circular fiber guide groove 51. The ends of the fiber optic cables are left on the silicone pad 6, and the ends of the fiber optic cables are fixed on the silicone pad 6 using high-temperature resistant tape.

[0042] S4. After applying acetone release agent to the inner wall of the positioning groove 11, insert the molding core mold 3 into the positioning groove 11. Insert countersunk square neck bolts 8 into the corresponding positions of the four corners of the base 5. After the countersunk square neck bolts 8 pass through the connecting die 1, tighten the nuts 9 with threads so that the die 1 and the molding core mold 3 evenly press the carbon fiber layer in the sample molding cavity. At this time, the bottom surface of the die 1 and the top surface of the molding core mold 3 do not contact each other, leaving a compression space and avoiding compression of the tail fiber on the silicone pad 6.

[0043] S5. The complete composite tensile specimen mold, together with the carbon fiber layer and the fiber optic sensor 4, is sent into the curing oven. After heat curing, the mold is removed and demolded to obtain the carbon fiber layup tensile specimen 2 with the fiber optic sensor 4 implanted.

[0044] The carbon fiber monolayer can be either unidirectional carbon fiber filament or orthogonal carbon fiber filament, and can also be either carbon fiber prepreg or pure carbon fiber. If pure carbon fiber is used, resin must be brushed on immediately after each layer of carbon fiber monolayer is laid to complete the impregnation and remove interlayer air bubbles before proceeding with subsequent layering operations.

[0045] In step S2, a 1-2mm gap is made on the carbon fiber monolayer at the position of the fiber optic guide hole 31 corresponding to the molded core 3 (the diameter of the fiber optic sensor 4 is 0.25mm), and the pigtail of the fiber optic sensor 4 is guided through the gap to the fiber optic guide hole 31.

[0046] In step S4, the carbon fiber layer in the sample forming cavity formed by the concave mold 1 and the forming core mold 3 experiences a pressure of 50N-200N. Pressure sensors can be installed next to each set of pressurizing components for uniform pressure monitoring, ensuring that the pressure applied by several sets of pressurizing components is relatively uniform, and ensuring process repeatability and consistency of finished product quality.

[0047] In step S5, the thermosetting temperature of the carbon fiber layup tensile specimen 2 is controlled between 110℃ and 150℃. Depending on the type of resin, the thickness of the component, and other material and process factors, the total thermosetting time is generally between 1 hour and 4 hours (in actual applications, the thermosetting temperature and the pressure on the carbon fiber layer should be adjusted accordingly).

[0048] The composite tensile specimen mold and preparation method with embedded fiber optic sensors described above are used to solve the problem that existing external monitoring technologies are limited by the integration process and cannot effectively capture interlaminar strain changes during tensile specimen testing.

[0049] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A composite material tensile specimen mold with an implanted fiber optic sensor, comprising a base (5), characterized in that, The base (5) has several vertical positioning pins (7) inserted into its top. The base (5) has a long strip-shaped molding core mold (3) placed on its top. All the positioning pins (7) are inserted into the corresponding mold positioning holes (33). The base (5) has a concave mold (1) on its top. The molding core mold (3) is inserted into the positioning groove (11) that matches it to form a sample molding cavity. Both ends of the molding core mold (3) are provided with fiber optic guide holes (31) that penetrate the molding core mold (3) vertically. Each fiber optic guide hole (31) is connected to a first semi-circular fiber optic groove (32) located at the bottom of the molding core mold (3). The base (5) has a second semi-circular fiber optic groove (51) that is combined with the first semi-circular fiber optic groove (32) to form a circular channel. The circular channel and the fiber optic guide hole (31) are connected with rounded corners. At least two sets of pressure components are provided between the concave mold (1) and the base (5). The pressure components are located at the edge of the base (5).

2. The composite material tensile specimen mold with an implanted fiber optic sensor according to claim 1, characterized in that, The base (5) is provided with a silicone pad (6) at the exit of each circular channel.

3. The composite material tensile specimen mold with an implanted fiber optic sensor according to claim 1, characterized in that, The diameter of both the fiber optic guide hole (31) and the circular channel is 3mm, and the radius of the corner at the connection between the circular channel and the fiber optic guide hole (31) is 1.5mm.

4. The composite material tensile specimen mold with an implanted fiber optic sensor according to claim 1, characterized in that, Each pressurizing assembly includes a countersunk square neck bolt (8) and a nut (9). The countersunk square neck bolt (8) passes through the die (1) and the base (5) and is threaded to the nut (9). The base (5) has a countersunk square neck bolt hole adapted to the head of the countersunk square neck bolt (8).

5. The composite material tensile specimen mold with an implanted fiber optic sensor according to claim 1, characterized in that, The dimensions of the sample forming cavity formed by the concave mold (1) and the forming core mold (3) conform to any one of the standards ASTM D3090, GB / T 3354-2014, and GB / T 1447-2005.

6. A method for preparing a composite tensile specimen with an implanted fiber optic sensor, characterized in that, Using the composite tensile specimen mold with an implanted fiber optic sensor as described in any one of claims 1-5, the process includes the following steps: S1. After applying acetone release agent to the top of the molding core mold (3), lay carbon fiber single layers one by one. S2. After laying several layers of the required carbon fiber single layer, embed the fiber optic sensor (4), wherein the two ends of the fiber optic sensor (4) pass through the lower carbon fiber layer and extend into the fiber optic guide hole (31), and the middle part of the fiber optic sensor (4) is placed on the laid carbon fiber layer. S3. Continue to lay several layers of the required carbon fiber single layer, then insert the positioning pin (7) into the base (5), and then insert the forming core mold (3) into the positioning pin (7). At the same time, the two ends of the fiber optic sensor (4) are led out from the circular channel formed by the first semi-circular fiber guide groove (32) and the second semi-circular fiber guide groove (51). The ends of the fiber optic cables are left on the silicone pad (6), and the ends of the fiber optic cables are fixed on the silicone pad (6) using high-temperature resistant tape. S4. After applying acetone release agent to the inner wall of the positioning groove (11), insert the molding core mold (3) into the positioning groove (11), insert countersunk square neck bolts (8) into the corresponding positions of the four corners of the base (5), and tighten the nuts (9) after the countersunk square neck bolts (8) pass through the connecting die (1), so that the die (1) and the molding core mold (3) evenly press the carbon fiber layer in the sample molding cavity. S5. The complete composite tensile specimen mold, together with the carbon fiber layer and the fiber optic sensor (4), is sent into the curing oven. After heat curing, the mold is removed and demolded to obtain the carbon fiber layup tensile specimen (2) with the fiber optic sensor (4) implanted.

7. The method for preparing a composite tensile specimen with an implanted fiber optic sensor according to claim 6, characterized in that, The carbon fiber monolayer is either unidirectional carbon fiber filament or orthogonal carbon fiber filament, and the carbon fiber monolayer is also either carbon fiber prepreg or pure carbon fiber.

8. The method for preparing a composite tensile specimen with an implanted fiber optic sensor according to claim 6, characterized in that, In step S2, a 1-2 mm gap is opened at the position of the fiber guide hole (31) of the forming core mold (3) on the carbon fiber monolayer, and the pigtail of the fiber sensor (4) is guided through the gap to the fiber guide hole (31).

9. The method for preparing a composite tensile specimen with an implanted fiber optic sensor according to claim 6, characterized in that, In step S4, the pressure on the carbon fiber layer in the sample forming cavity formed by the concave mold (1) and the forming core mold (3) is 50N-200N.

10. The method for preparing a composite tensile specimen with an implanted fiber optic sensor according to claim 6, characterized in that, In step S5, the thermosetting temperature of the carbon fiber layup tensile specimen (2) is controlled at 110℃-150℃, and the thermosetting time is 1-4 hours.

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