Composite material tensile sample mold implanted with optical fiber sensor and preparation process of composite material tensile sample mold

Abstract

The invention discloses a composite material tensile sample mold implanted with an optical fiber sensor and a preparation process, and particularly relates to the technical field of optical fiber sensors, the composite material tensile sample mold comprises a base, a long-strip-shaped forming core mold is placed at the top of the base, the tops of all positioning pins are inserted into corresponding matched mold positioning holes, and a female mold covers the top of the base; the forming core mold is inserted into a positioning groove matched with the forming core mold to form a sample forming cavity, optical fiber guide holes penetrating through the forming core mold up and down are formed in the two ends of the forming core mold, and each optical fiber guide hole communicates with a first semicircular fiber guide groove formed in the bottom of the forming core mold; a first semicircular fiber guide groove is formed in the female die, a second semicircular fiber guide groove is formed in the base, the first semicircular fiber guide groove and the second semicircular fiber guide groove are spliced into a circular channel, and at least two sets of pressurizing assemblies are arranged between the female die and the base. Bending and extrusion in the layering and compacting process are avoided, and the implantation survival rate is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber sensors, and particularly relates to a composite material tensile specimen mold for implanting an optical fiber sensor and a preparation process. BACKGROUND

[0002] With the wide application of composite materials in high-end equipment fields such as aerospace, wind power blades and new energy vehicles, the demand for accurate monitoring of the internal damage evolution mechanism of the composite materials is increasingly urgent. The industry urgently needs to obtain the internal strain field distribution of the components through implantable optical fiber sensors to replace the traditional surface-pasted strain gauge test method, which cannot capture the internal strain changes of the material and is easily affected by the environment temperature and humidity, resulting in data drift. However, the current laboratory preparation of the composite material tensile specimen for implanting the optical fiber sensor faces three technical bottlenecks: first, the manual pre-embedding method easily causes the spatial deviation or excessive bending of the optical fiber, resulting in the breakage of the fiber core during the layer compaction process, and the low survival rate of the sensor; second, the existing mold lacks a special positioning structure, and it is difficult to accurately control the embedding position of the optical fiber in the thickness direction of the specimen, resulting in the deviation of the strain measurement value; and third, during the heat pressing process in the curing stage, there is a lack of effective fixing mechanism for the sensor, which easily causes the position deviation of the sensor or the poor bonding between the sensor and the base, affecting the measurement reliability.

[0003] Therefore, it is urgent to develop a composite material tensile specimen mold for implanting an optical fiber sensor and a preparation method to solve the above problems. SUMMARY

[0004] To solve the above problems, the application discloses a mold and process that can realize high-precision positioning, micro-damage implantation and synchronous forming of the specimen for the optical fiber sensor, and solves the problems of low survival rate, poor position accuracy and poor interface bonding in the traditional method.

[0005] To achieve the above purpose, the technical scheme of the application is as follows:

[0006] A composite material tensile specimen mold for implanting an optical fiber sensor, comprising a base, a plurality of vertical positioning pins are inserted into the top of the base, a long strip-shaped forming core mold is placed on the top of the base, and all the positioning pins are inserted into the corresponding mold positioning holes, a concave mold is covered on the top of the base, and the forming core mold is inserted into the corresponding positioning groove to form a specimen forming cavity, fiber guide holes are arranged at both ends of the forming core mold and penetrate the forming core mold, and each fiber guide hole is communicated with a first semicircular fiber guide groove arranged at the bottom of the forming core mold, a second semicircular fiber guide groove is formed on the base and is combined with the first semicircular fiber guide groove to form a circular channel, and a round corner is arranged at the communication position of the circular channel and the fiber guide hole, at least two groups of pressing assemblies are arranged between the base and the concave mold, and the pressing assemblies are arranged at the edges of the base.

[0007] As a preferred technical solution of the present application, the base is provided with a silica gel pad at the outlet of each circular channel.

[0008] As a preferred technical solution of the present application, the diameter of the fiber guide hole and the circular channel is 3 mm, and the circular angle of the communication part of the circular channel and the fiber guide hole is 1.5 mm.

[0009] As a preferred technical solution of the present application, each group of the pressing assembly comprises a countersunk square neck bolt and a nut, the countersunk square neck bolt is screwed with the nut after penetrating the die and the base, and the base is provided with a countersunk square neck bolt hole matching the head of the countersunk square neck bolt.

[0010] As a preferred technical solution of the present application, the size of the sample forming cavity formed by the die and the forming core meets any one of the standards of ASTM D3090, GB / T 3354-2014 and GB / T 1447-2005.

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

[0012] S1, after smearing acetone release agent on the top of the forming core mold, layer by layer lay the carbon fiber single layer;

[0013] S2, after laying several layers of required carbon fiber single layer, bury the optical fiber sensor, wherein the two end fibers of the optical fiber sensor penetrate into the fiber guide hole from the lower carbon fiber layer, and the middle part of the optical fiber sensor is placed on the laid carbon fiber layer;

[0014] S3, continue to lay several layers of required carbon fiber single layer, then insert the positioning pin into the base, then insert the forming core mold on the positioning pin, at the same time, the two end fibers of the optical fiber sensor are drawn out from the circular channel formed by the first semicircular fiber guide groove and the second semicircular fiber guide groove, and the end part of the fiber is left on the silica gel pad, and the end part of the fiber is fixed on the silica gel pad by using high-temperature resistant adhesive tape;

[0015] S4, after smearing acetone release agent on the inner wall of the positioning groove, insert the forming core mold into the positioning groove, insert the countersunk square neck bolt into the corresponding position of the four corners of the base, and screw the nut after penetrating the connecting die, so that the die and the forming core mold uniformly press the carbon fiber layer in the sample forming cavity;

[0016] S5, the complete composite material tensile sample mold is sent into the curing oven together with the carbon fiber layer and the optical fiber sensor, and after heat curing, the mold is taken out for demolding to obtain the carbon fiber layer tensile sample implanted with the optical fiber sensor.

[0017] As a preferred technical scheme of the present application, the carbon fiber single layer is any one of unidirectional carbon fiber filaments and orthogonal carbon fiber filaments, and the carbon fiber single layer is any one of carbon fiber prepreg and pure carbon fiber.

[0018] As a preferred technical scheme of the present application, in the step S2, a 1-2 mm aperture is opened at the position of the fiber guide hole of the optical fiber sensor on the carbon fiber single layer corresponding to the forming core mold, and the tail fiber of the optical fiber sensor is guided to pass through the aperture to the fiber guide hole of the optical fiber.

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

[0020] As a preferred technical scheme of the present application, in the step S5, the heat curing forming temperature of the carbon fiber layer is controlled at 110-150℃, and the heat curing forming time is 1-4 hours.

[0021] The present application has the following beneficial effects:

[0022] First, the optical fiber sensor is provided with a protected path through the fiber guide hole on the forming core mold and the circular channel formed with the base, avoiding bending and extrusion during the laying and compaction process, and significantly improving the survival rate of implantation.

[0023] Second, the process design of directly controlling the fiber depth during the laying process is used, the fiber is accurately placed on a specific carbon fiber layer, and the positioning structure of the mold is combined to ensure the position accuracy of the fiber in the thickness direction of the sample, and the measurement error caused by the depth deviation is eliminated.

[0024] Third, the tail fiber is fixed on the silica gel pad before heat curing, and the mold is tightly pressed, which effectively limits the movement of the optical fiber during the curing stage, ensures the stability of the fiber sensor-matrix interface, and improves the reliability of the measurement signal. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a schematic diagram of the tensile specimen mold of the embodiment of the present application;

[0026] Figure 2 It is an axial section view of the tensile specimen mold of the embodiment of the present application;

[0027] Figure 3 It is an enlarged view of A in the embodiment of the present application; Figure 2

[0028] Figure 4 It is a schematic diagram of the base in the tensile specimen mold of the embodiment of the present application;

[0029] Figure 5 ​The figure shows the tensile specimen of the composite material with embedded optical fiber sensor according to the embodiment of the present application.

[0030] List of reference signs:

[0031] 1, concave die; 11, positioning groove; 2, carbon fiber ply tensile specimen; 3, forming core; 31, fiber guide hole; 32, first semicircular fiber guide groove; 33, mold positioning hole; 4, optical fiber sensor; 5, base; 51, second semicircular fiber guide groove; 6, silica gel pad; 7, positioning pin; 8, countersunk square neck bolt; 9, nut. DETAILED DESCRIPTION

[0032] The present application will be further illustrated in conjunction with the accompanying drawings and specific embodiments, and it should be understood that the following specific embodiments are only used to illustrate the present application and not to limit the scope of the present application.

[0033] Please refer to Figures 1-5 A tensile specimen mold of the composite material with embedded optical fiber sensor comprises a base 5, the top of which is inserted with a plurality of vertical positioning pins 7. A long strip-shaped forming core 3 is placed on the top of the base 5, and the top of all the positioning pins 7 is inserted into the corresponding and adapted mold positioning hole 33. The concave die 1 is covered on the top of the base 5, and the forming core 3 is inserted into the corresponding and adapted positioning groove 11 to form a specimen forming cavity. The forming core 3 is provided with fiber guide holes 31 penetrating through the forming core 3 from top to bottom at both ends, and each fiber guide hole 31 is communicated with the first semicircular fiber guide groove 32 arranged at the bottom of the forming core 3. In the embodiment of the drawings, the fiber guide holes 31 vertically penetrate through the forming core 3 from top to bottom. The base 5 is provided with the second semicircular fiber guide groove 51 which is combined with the first semicircular fiber guide groove 32 to form a circular channel, and a round corner is arranged at the communication position of the circular channel and the fiber guide hole 31. The base 5 is provided with a silica gel pad 6 at the outlet of each circular channel.

[0034] At least two sets of pressing assemblies are arranged between the concave die 1 and the base 5, and the pressing assemblies are arranged at the edges of the base 5. In the embodiment of the drawings, one set of pressing assembly is arranged at each corner of the base 5. Each set of pressing assembly comprises a countersunk square neck bolt 8 and a nut 9, the countersunk square neck bolt 8 is threadedly connected with the nut 9 after penetrating through the concave die 1 and the base 5, and the base 5 is provided with a countersunk square neck bolt hole which is adapted to the head of the countersunk square neck bolt 8.

[0035] The diameter of the fiber guide hole 31 and the circular channel is 3 mm. The round corner radian at the communication position of the circular channel and the fiber guide hole 31 is 1.5 mm, which is used to avoid the damage of the optical fiber sensor 4 caused by bending.

[0036] The size of the specimen forming cavity formed by the concave die 1 and the forming core 3 meets any one of the standards of ASTM D3090, GB / T 3354-2014 and GB / T 1447-2005.

[0037] If the positioning pin 7 is a cylinder, the base 5 is inserted with at least two positioning pins 7. If the positioning pin 7 is a prism, the base 5 is inserted with at least one positioning pin 7.

[0038] A method for preparing a composite material tensile specimen embedded with an optical fiber sensor, using the composite material tensile specimen mold described above, comprising the following steps:

[0039] S1, after applying acetone release agent on the top of the forming core mold 3, layer by layer lay the carbon fiber single layer;

[0040] S2, after laying several layers of the required carbon fiber single layer, embed the optical fiber sensor 4, wherein the two end fibers of the optical fiber sensor 4 pass through the lower carbon fiber layer and extend into the optical fiber guide hole 31, and the middle part of the optical fiber 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, then insert the forming core mold 3 on the positioning pin 7, at the same time, the two end fibers of the optical fiber sensor 4 are drawn out from the circular channel formed by the first semicircular fiber guide slot 32 and the second semicircular fiber guide slot 51, and the end part of the fiber is left on the silica gel pad 6, and the end part of the fiber is fixed on the silica gel pad 6 using high-temperature resistant adhesive tape;

[0042] S4, after applying acetone release agent on the inner wall of the positioning groove 11, insert the forming core mold 3 into the positioning groove 11, insert the countersunk square neck bolt 8 into the corresponding position of the four corners of the base 5, and then screw the nut 9 after passing through the connecting concave mold 1, so that the concave mold 1 and the forming core mold 3 uniformly press the carbon fiber layer in the specimen forming cavity, at this time, the bottom surface of the concave mold 1 and the top surface of the forming core mold 3 are not in contact, leaving a space for extrusion, which can also avoid extruding the fiber on the silica gel pad 6;

[0043] S5, the complete composite material tensile specimen mold together with the carbon fiber layer and the optical fiber sensor 4 is sent into the curing oven, and after heat curing, the mold is taken out for demolding to obtain the carbon fiber lay-up tensile specimen 2 embedded with the optical fiber sensor 4.

[0044] The carbon fiber single layer is any one of unidirectional carbon fiber wire material and orthogonal carbon fiber wire material, and the carbon fiber single layer is also any one of carbon fiber prepreg and pure carbon fiber, if pure carbon fiber is used, the resin needs to be brushed immediately after laying each layer of carbon fiber single layer to complete the infiltration and exclude air bubbles between the layers, and then the subsequent layering operation is performed.

[0045] In step S2, a 1-2mm aperture is poked on the carbon fiber single layer at the position corresponding to the optical fiber guide hole 31 of the forming core mold 3 (the diameter of the optical fiber sensor 4 is 0.25mm), and the tail fiber of the optical fiber sensor 4 is guided to pass through the aperture to the optical fiber guide hole 31.

[0046] The pressure of the carbon fiber layer in the sample forming cavity formed by the die 1 and the forming core 3 in the S4 step is 50N-200N. A pressure sensor can be arranged beside each set of pressurizing assembly to monitor the pressure uniformly, so as to ensure that the pressure applied by the several sets of pressurizing assembly is relatively uniform, and ensure the process repeatability and the consistency of the finished product quality.

[0047] In the S5 step, the heat curing forming temperature of the carbon fiber layer tensile sample 2 is controlled at 110-150 DEG C. According to different resin types, part thickness and other material and process factors, the total heat curing forming time is generally 1-4 hours (in actual application, the heat curing forming temperature and the pressure of the carbon fiber layer are adjusted accordingly).

[0048] The above composite tensile sample mold and preparation method for implanting optical fiber sensors are used to solve the problem that the existing external monitoring technology is limited by the integration process and cannot effectively capture the interlayer strain change in the tensile sample test process.

[0049] It should be noted that the above content only illustrates the technical idea of the present application and cannot limit the protection scope of the present application. For ordinary skilled in the art, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements fall within the protection scope of the claims of the present application.

Claims

1. A mold for composite tensile specimens with embedded optical fiber sensors, comprising a base (5), characterized in that, The base (5) is inserted with several vertical positioning pins (7) on the top, the long strip-shaped forming core mold (3) is placed on the top of the base (5), and the top of all the positioning pins (7) is inserted into the corresponding matched mold positioning hole (33), the top of the base (5) is covered with a concave die (1), and the forming core mold (3) is inserted into the matched positioning groove (11) to form a sample forming cavity, the both ends of the forming core mold (3) are provided with fiber guiding holes (31) which penetrate through the forming core mold (3) from top to bottom, and each fiber guiding hole (31) is communicated with the first semicircular fiber guiding groove (32) arranged at the bottom of the forming core mold (3), the base (5) is provided with the second semicircular fiber guiding groove (51) which is spliced with the first semicircular fiber guiding groove (32) to form a circular channel, and a round corner is arranged at the communication position of the circular channel and the fiber guiding hole (31), at least two groups of pressurizing assemblies are arranged between the concave die (1) and the base (5), and the pressurizing assemblies are arranged at the edge of the base (5).

2. The mold for a composite tensile specimen with embedded optical fiber sensor according to claim 1, wherein The base (5) is provided with a silica gel pad (6) at the outlet of each circular channel.

3. The mold for a composite tensile specimen with embedded optical fiber sensor according to claim 1, wherein The diameter of the fiber guiding hole (31) and the circular channel is 3mm, and the round corner radian at the communication position of the circular channel and the fiber guiding hole (31) is 1.5mm.

4. The mold for a composite tensile specimen with embedded optical fiber sensor according to claim 1, wherein Each group of pressurizing assemblies comprises a countersunk square neck bolt (8) and a nut (9), the countersunk square neck bolt (8) is threadedly connected with the nut (9) after penetrating through the concave die (1) and the base (5), and the base (5) is provided with a countersunk square neck bolt hole matched with the head of the countersunk square neck bolt (8).

5. The mold for a composite tensile specimen with embedded optical fiber sensor according to claim 1, wherein The size of the sample forming cavity formed by the concave die (1) and the forming core mold (3) meets any one of the standards of ASTM D3090, GB / T 3354-2014 and GB / T 1447-2005.

6. A method of preparing a composite tensile specimen for implanting an optical fiber sensor, characterized by, The use of the composite material tensile sample mold for implanting the optical fiber sensor according to any one of claims 1-5 comprises the following steps: S1, after smearing acetone release agent on the top of the forming core mold (3), layer by layer, carbon fiber single layer is laid; S2, after laying several layers of required carbon fiber single layer, the optical fiber sensor (4) is embedded, wherein the two end fibers of the optical fiber sensor (4) penetrate into the fiber guiding hole (31) from the lower carbon fiber layer, and the middle part of the optical fiber sensor (4) is placed on the already laid carbon fiber layer; S3, continue to lay several layers of required carbon fiber single layer, then insert the positioning pin (7) into the base (5), then insert the forming core mold (3) on the positioning pin (7), at the same time, the two end fibers of the optical fiber sensor (4) are drawn out from the circular channel formed by the first semicircular fiber guiding groove (32) and the second semicircular fiber guiding groove (51), and the end part of the fiber is left on the silica gel pad (6), and the end part of the fiber is fixed on the silica gel pad (6) by using high-temperature resistant adhesive tape. S4, after the inner wall of the positioning groove (11) is coated with acetone release agent, the forming core mold (3) is inserted into the positioning groove (11), the base (5) is inserted into the countersunk square neck bolt (8) at the corresponding position of the four corners, the countersunk square neck bolt (8) is screwed with the nut (9) after passing through the connecting die (1), so that the die (1) and the forming core mold (3) uniformly press the carbon fiber layer in the sample forming cavity; S5, the complete composite tensile specimen mold together with the carbon fiber layer and the optical fiber sensor (4) is sent into the curing oven, and after heat curing, the mold is taken out for demolding to obtain the carbon fiber layer tensile specimen (2) implanted with the optical fiber sensor (4).

7. The method of claim 6, wherein the step of preparing the composite tensile specimen is performed by embedding the optical fiber sensor in the composite material. The carbon fiber single layer is any one of unidirectional carbon fiber wire material and orthogonal carbon fiber wire material, and the carbon fiber single layer is any one of carbon fiber prepreg and pure carbon fiber.

8. The method of claim 6, wherein the method further comprises the step of: 8-1) applying a coating to the surface of the optical fiber sensor. In step S2, the 1-2mm aperture is opened at the position corresponding to the optical fiber guide hole (31) of the forming core mold (3) on the carbon fiber single layer, and the tail fiber of the optical fiber sensor (4) is guided to pass through the aperture to the optical fiber guide hole (31).

9. The method of claim 6, wherein the method further comprises the step of: 9-1) applying a coating to the surface of the optical fiber sensor. In step S4, the pressure of the carbon fiber layer in the sample forming cavity formed by the die (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 heat curing forming temperature of the carbon fiber layer tensile specimen (2) is controlled at 110-150℃, and the heat curing forming time is 1-4 hours.

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