A strain-sensing heat-proof composite material based on optical fiber sensing technology and a preparation method thereof

Abstract

The application discloses a strain sensing heat-proof composite material based on an optical fiber sensing technology and a preparation method thereof. The method combines the optical fiber sensing technology with the preparation of the heat-proof composite material, improves the matching of the sensor and the heat-proof material through structural design and effective packaging of the sensor. The prepared strain sensing heat-proof composite material based on the optical fiber sensing technology has a normal temperature tensile property retention rate of the heat-proof composite material body of not less than 80%, a thermal conductivity performance retention rate of not less than 80% and a sensor survival rate of not less than 70%, realizes the heat protection of the heat-proof material and the internal strain monitoring of the heat-proof material, and provides basic data for health monitoring of the heat-proof material.

Description

TECHNICAL FIELD

[0001] The present application relates to a strain sensing heat-resistant composite material based on optical fiber sensing technology and a preparation method thereof, and belongs to the technical field of functional composites. BACKGROUND

[0002] The sensing and monitoring of internal strain of heat-resistant materials are of great significance. For example, monitoring the release degree of internal stress during the forming process of heat-resistant materials helps to understand the curing mechanism of heat-resistant materials and improve the preparation process; long-term monitoring of the deformation of heat-resistant materials at room temperature can reveal the long-term creep characteristics of heat-resistant materials; monitoring the cracking strain of heat-resistant materials at high temperature provides important data support for the study of cracking-ablation mechanism. However, the variation of the thermal physical performance parameters of heat-resistant materials with temperature determines the internal heat conduction process of the material. Due to the complex pyrolysis reaction during the heating process, the thermal physical parameters of heat-resistant materials are difficult to accurately obtain through experimental methods. The internal thermal response process monitoring technology of heat-resistant materials is relatively scarce, and the conventional testing methods and performance characterization means are difficult to realize the real-time monitoring of the internal thermal response parameters of the material. The lag of the monitoring technology has become an obstacle to the development of heat-resistant materials. There are still technical problems in the research on the temperature resistance, effective packaging and matching of heat-resistant materials of the performance sensing sensor.

[0003] With the rapid development of optical fiber sensing technology, the miniaturization, strong anti-electromagnetic interference ability, corrosion resistance and networking of optical fiber sensors are highlighted. At present, optical fiber sensing technology is widely used in the health monitoring of structures such as bridges, railways, power facilities and spacecraft. According to the needs of actual application, the appropriate packaging material and reasonable packaging process can be selected to implant the sensor into the composite material, which can ensure the compatibility of the packaged sensor and the matrix material, improve the survival ability of the sensor in various environments, reduce the strain transmission loss, and improve the accuracy and reliability of the monitoring results. At present, the composite material monitoring method based on optical fiber sensing technology mostly stays at the stage of material surface test, and cannot be applied to the actual monitoring needs of heat-resistant composites.

[0004] Therefore, the combination of optical fiber sensing technology and heat-resistant composite material preparation, through structure design, effective packaging of sensors, and improvement of the matching of sensors and heat-resistant materials, can realize both the heat protection function of heat-resistant materials and the internal strain monitoring of heat-resistant materials, and provide basic data for the health monitoring of heat-resistant materials. It is a technical problem to be solved in the field. SUMMARY

[0005] The technical problem solved by the present application is to overcome the shortcomings of the prior art and provide a strain sensing heat-resistant composite material based on optical fiber sensing technology and a preparation method thereof. Both the heat protection function of heat-resistant materials and the internal strain monitoring of heat-resistant materials are realized, and basic data for the health monitoring of heat-resistant materials are provided.

[0006] The application provides a strain sensing heat-proof composite material based on an optical fiber sensing technology, which comprises a heat-proof composite material and an optical fiber grating sensor encapsulated in the heat-proof composite material.

[0007] The heat-proof composite material is a laminated quartz / phenolic composite material.

[0008] The heat-proof composite material is obtained by hot pressing a plurality of quartz / phenolic prepreg layers.

[0009] In the quartz / phenolic prepreg, the mass fraction of the phenolic resin is 40-50%, and the mass fraction of the volatile component is 5-10%. The quartz / phenolic prepreg can be obtained from various public commercial channels.

[0010] In the strain sensing heat-proof composite material based on the optical fiber sensing technology, the mass fraction of the phenolic resin in the quartz / phenolic prepreg is 45%, and the mass fraction of the volatile component is 7-9%.

[0011] In the optical fiber grating sensor, the strain and temperature can be sensed by the change of the grating reflection wavelength.

[0012] The optical fiber grating sensor is a high-temperature-resistant optical fiber grating sensor based on femtosecond laser inscription.

[0013] The optical fiber grating sensor is composed of a type I sensor and a type II sensor.

[0014] The type I sensor is a strain-temperature sensor using a bare grating.

[0015] The type II sensor is a temperature sensor using a metal capillary tube to suspend and encapsulate the grating. The length of the metal capillary tube is greater than the length of the grating.

[0016] The type I sensor and the type II sensor can be obtained from public commercial channels as long as the corresponding functions can be realized.

[0017] The length of the grating region is not less than 10 mm, the reflectivity is not less than 70%, the 3dB bandwidth of the reflection spectrum is not greater than 0.2 mm, and the central wavelength range is 1530-1570 nm.

[0018] The distance between the two gratings is 5 mm.

[0019] In the strain sensing heat-proof composite material based on the optical fiber sensing technology, the retention rate of the normal temperature tensile property of the heat-proof composite material is not less than 80%, the retention rate of the thermal conductivity property is not less than 80%, and the survival rate of the sensor is not less than 70%.

[0020] The application provides a method for preparing the strain sensing heat-proof composite material based on the optical fiber sensing technology, and comprises the following steps.

[0021] 1) Quartz / phenolic prepreg pretreatment:

[0022] vacuum heat treatment is conducted on the multilayer quartz / phenolic prepreg;

[0023] In the vacuum heat treatment, the temperature is 60-80 DEG C, the vacuum degree is not less than 0.05 MPa, and the holding time is 2-6 h, so that the phenolic resin infiltration performance between the quartz / phenolic prepreg layers is improved;

[0024] 2) Packaging of the fiber grating sensor between the quartz / phenolic prepreg layers, as shown in the schematic diagram Figure 1 , and comprising the following steps 2.1) to 2.3):

[0025] 2.1) Protection and fixation of the grating:

[0026] The type I sensor adopts method one or method two for protection and fixation of the grating, and the method two is a more optimal method;

[0027] The type II sensor adopts method three for protection and fixation of the grating;

[0028] The method one comprises the following steps: firstly, the type I sensor is buried between the quartz / phenolic prepreg layers; secondly, the grating is straightened at both ends; and thirdly, the grating is fixed on the quartz / phenolic prepreg by using epoxy glue or silicone rubber at both ends of the grating;

[0029] The method two comprises the following steps: firstly, a grating protection sheet is prepared for protection of the grating, so as to avoid the influence of the fabric weaving structure in the prepreg on the grating and the influence of the prepreg slippage on the grating position during the molding process of the quartz / phenolic composite material; secondly, the grating is buried in the groove of the grating protection sheet, and the grating is fixed on the grating protection sheet by using epoxy glue or silicone rubber at both ends of the grating; and thirdly, according to the size of the grating protection sheet, a groove is formed in the quartz / phenolic prepreg, the grating protection sheet is filled in the groove of the quartz / phenolic prepreg, and the surface of the quartz / phenolic prepreg is flat;

[0030] The method three comprises the following steps: since the grating of the type II sensor is packaged in a metal capillary, the metal capillary of the type II sensor is fixed in the grating protection sheet or the quartz / phenolic prepreg by using epoxy glue or silicone rubber, and the distance between the grating of the type II sensor and the grating of the type I sensor is not greater than 5 mm;

[0031] 2.2) Protection of the fiber grating sensor at the edge of the quartz / phenolic prepreg:

[0032] 2.2) Protection of the fiber grating sensor at the edge of the quartz / phenolic prepreg:

[0033] First, a stainless steel capillary tube is sleeved outside the type I sensor and type II sensor, then the surface of the upper and lower quartz / phenolic prepreg in contact with the type I sensor and type II sensor is slotted, so that the stainless steel capillary tube is embedded in the quartz / phenolic prepreg, and its surface is flush with the prepreg in the thickness direction, finally epoxy glue or silicone rubber is used to fix the edge of the stainless steel protective sleeve and the mouth of the metal capillary tube on the quartz / phenolic prepreg to prevent phenolic resin from entering the stainless steel capillary tube;

[0034] 2.3) The optical fiber grating sensor is drawn out of the quartz / phenolic prepreg:

[0035] The metal capillary tube, type I sensor and type II sensor outside the quartz / phenolic prepreg are drawn out through a PVDF hollow tube, and the length of the PVDF hollow tube is greater than the length of the type I sensor and type II sensor, the tube end is folded and sealed, the distal end is pasted with paper tape, and the grating wavelength is recorded;

[0036] 3) Curing:

[0037] PVDF / glass paint cloth is first laid on the upper and lower surfaces of the quartz / phenolic prepreg, and then polyimide film is laid, and pressure curing is carried out by using a press or an autoclave;

[0038] The pressure curing includes curing I and curing II;

[0039] In the curing I, the temperature is 80-100℃, and the holding time is 0.5-2h;

[0040] In the curing II, the temperature is 120-160℃, and the holding time is 2-8h;

[0041] The pressure of the curing I and the curing II is both 0.5-2MPa;

[0042] 4) Post-processing:

[0043] After the curing in step 3), when the temperature is reduced to below 40℃, the obtained composite material is taken out from the press or the autoclave, the polyimide film and PVDF / glass paint cloth on the surface of the material are removed, the PVDF hollow tube outside the type I sensor and type II sensor is replaced with a high-temperature-resistant protective sleeve, and the strain sensing heat-resistant composite material based on the optical fiber sensing technology is obtained.

[0044] In the vacuum heat treatment in step 1) of the above method, the temperature is 70-75℃.

[0045] In the step 2.1), the grating protective sheet is a slotted quartz / phenolic composite body sheet with a thickness of 4-8 mm; the slotted size is 2-4 mm in diameter and 1.5-2.5 mm in depth.

[0046] In the step 2.2), the stainless steel capillary is embedded at a distance of 0.5-6 mm from the upper and lower slotted positions of the quartz / phenolic prepreg in the fiber laying direction.

[0047] In the step 3), the curing I temperature is 90 DEG C, and the holding time is 1 h.

[0048] The curing II temperature is 140-150 DEG C, and the holding time is 2-4 h.

[0049] The curing pressure is 1 MPa.

[0050] In addition, the application of the strain sensing heat-resistant composite material based on the optical fiber sensing technology in health monitoring of the heat-resistant material, thermal protection of the heat-resistant material or internal strain monitoring of the heat-resistant material also belongs to the protection scope of the present application.

[0051] Specifically, the internal strain monitoring of the heat-resistant material comprises:

[0052] 1) monitoring of the strain in the curing process of the heat-resistant material;

[0053] 2) monitoring of the strain in the high-temperature pyrolysis process of the heat-resistant material;

[0054] The high temperature is specifically room temperature-700 DEG C.

[0055] 3) monitoring of the long-time strain at room temperature of the heat-resistant material;

[0056] The long time is specifically not less than 25 days.

[0057] The present application combines the optical fiber sensing technology with the preparation of the heat-resistant composite material, improves the matching of the sensor and the heat-resistant material through structural design and effective packaging of the sensor, and prepares the strain sensing heat-resistant composite material based on the optical fiber sensing technology, which has a normal temperature tensile property retention rate of not less than 80%, a thermal conductivity performance retention rate of not less than 80%, and a sensor survival rate of not less than 70%, realizes the thermal protection of the heat-resistant material and the internal strain monitoring of the heat-resistant material, provides basic data for the health monitoring of the heat-resistant material, and has important application value. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1Fig. 1 is a schematic diagram of the packaging structure of the fiber grating sensor between the prepreg layers, ① is a type I sensor, ② is a type II sensor, ③ is the grating in the type I and type II sensors, ④ is a grating protection sheet, ⑤ is a pretreated prepreg, ⑥ is a metal capillary tube, and ⑦ is a PVDF hollow tube;

[0059] Figure 2 Fig. 4 is a monitoring diagram of the strain of a strain-sensing heat-proof composite material plate during a curing process based on the fiber sensing technology;

[0060] Figure 3 Fig. 5 is a monitoring diagram of the strain of a strain-sensing heat-proof composite material plate during a cracking process based on the fiber sensing technology;

[0061] Figure 4 Fig. 6 is a strain trend diagram of a strain-sensing heat-proof composite material curved surface at room temperature and for a long time based on the fiber sensing technology, wherein CH1 is a convex center point, CH2 is a convex edge point, CH3 is a concave center point, and CH4 is a concave edge point. DETAILED DESCRIPTION

[0062] The present application is further described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. The methods are all conventional methods unless otherwise specified. The raw materials can be obtained from public commercial channels unless otherwise specified.

[0063] Example 1

[0064] The heat-proof composite material is a laminated quartz / phenolic composite material, which is hot-pressed from multiple layers of prepreg according to the thickness of the composite material, wherein the mass fraction of phenolic resin in the prepreg is 40%, and the mass fraction of volatile matter is 7%. The fiber sensing technology refers to sensing strain and temperature through the change of the reflection wavelength of the grating in the fiber grating sensor. The fiber grating sensor is a high-temperature-resistant fiber grating sensor based on femtosecond laser inscription. The fiber grating sensor is divided into two types according to the purpose: one is a strain-temperature sensor (type I sensor) using a bare grating; the other is a temperature sensor (type II sensor) using a grating suspended and packaged by a metal capillary tube, and the length of the metal capillary tube is greater than the length of the grating. The grating has a grating zone length of 10 mm, a reflectivity of 70%, a 3dB bandwidth of the reflection spectrum of 0.2 mm, and a center wavelength range of 1530 nm.

[0065] The specific steps of the preparation method of the strain-sensing heat-proof composite material based on the fiber sensing technology are as follows:

[0066] (1) Prepreg treatment: vacuum heat treatment is performed on the multiple layers of quartz / phenolic prepreg, the heat treatment temperature is 70°C, the vacuum degree is 0.05 MPa, and the heat preservation time is 2 h, so as to improve the phenolic resin infiltration performance between the layers of the quartz / phenolic prepreg;

[0067] (2) Packaging of fiber Bragg grating sensors between prepreg layers

[0068] A schematic diagram of the packaging structure of fiber Bragg grating sensors between quartz / phenolic prepreg layers is shown in FIG. 1, and the method comprises the following steps: Figure 1

[0069] (2.1) Method for protection and fixation of the grating: method one is used for type I sensors, and method three is used for type II sensors;

[0070] The method one comprises the following steps: first, burying the type I sensor between the prepreg layers; then, straightening the two ends of the grating; and finally, using epoxy glue to fix the grating on the prepreg at the two ends of the grating.

[0071] The method three comprises the following steps: since the grating of the type II sensor has been packaged in the metal capillary, the metal capillary of the type II sensor is fixed on the prepreg using epoxy glue, and the grating of the type II sensor is close to the grating of the type I sensor, with a distance of 5 mm between the two gratings.

[0072] (2.2) Protection of fiber Bragg grating sensors at the edges of quartz / phenolic prepreg: first, wrapping the type I and type II sensors with a stainless steel capillary; then, grooving the upper and lower quartz / phenolic prepreg surfaces in contact with the type I and type II sensors, so that the stainless steel capillary is buried in the quartz / phenolic prepreg, with its surface flush with the quartz / phenolic prepreg in the thickness direction; and finally, using epoxy glue or silicone rubber to fix the edges of the stainless steel protective sleeve and the metal capillary opening on the quartz / phenolic prepreg, to prevent phenolic resin from entering the stainless steel capillary.

[0073] (2.3) Leading out of fiber Bragg grating sensors from the quartz / phenolic prepreg: leading out the metal capillary outside the quartz / phenolic prepreg, the type I and type II sensors through a PVDF (polytetrafluoroethylene) hollow tube, the length of the PVDF hollow tube being greater than the length of the type I and type II sensors, folding and sealing the end of the tube, and sticking the distal end with a paper adhesive tape, and recording the grating wavelength.

[0074] (3) Curing of quartz / phenolic composite material with internally packaged fiber Bragg grating sensors: first, laying PVDF / glass paint cloth on the upper and lower surfaces of the prepreg, and then laying polyimide film. Generally, a press is used for pressurized curing of the prepreg, and the pressurized curing comprises curing I and curing II; in the curing I, the temperature is 80°C, and the holding time is 0.5 h; in the curing II, the temperature is 120°C, and the holding time is 8 h; and the pressure of the curing I and the curing II is both 0.5 MPa.

[0075] ​(4) Post-processing of quartz / phenolic composite material encapsulating optical fiber grating sensor: after the curing process is completed, the temperature is reduced by 30°C, the composite material is taken out of the press, the polyimide film on the surface of the composite material is removed, the PVDF / glass paint cloth is removed, and the PVDF hollow tube outside the type I and type II sensors is replaced with a high-temperature resistant protective sleeve, thereby obtaining a strain sensing heat protection composite material based on optical fiber sensing technology.

[0076] The strain sensing heat protection composite material based on optical fiber sensing technology prepared has a normal temperature tensile property retention rate of 85% compared to the bulk heat protection composite material, a thermal conductivity performance retention rate of 80%, and a sensor survival rate of 70%. The material not only realizes the heat protection function of the heat protection material, but also realizes the internal strain monitoring of the heat protection material, providing basic data for the curing monitoring of the heat protection material.

[0077] As shown in Figure 2 , it can be used to sense the strain during the curing process of the heat protection composite material, and the survival rate of the sensor needs to be improved. In subsequent examples, the survival rate of the optical fiber sensor is improved by method two in step (2.1). During the measurement of high temperature strain using the material, the optical fiber is found to be damaged at 350°C. In this example, the recess in the prepreg is flush with the end face of the metal capillary tube. Inspection finds that the damage location is at the end face where the metal capillary tube contacts the recess. In subsequent examples, the material is prepared according to the optimization measures in step (2.2). The specific optimization measures are to avoid the expansion coefficient difference between the heated stainless steel tube and the quartz / phenolic composite material causing optical fiber loss or even breakage. The stainless steel capillary tube is embedded at a distance of 0.5mm to 6mm from the upper and lower slotted positions on the prepreg in the direction of optical fiber laying.

[0078] Example 2

[0079] The heat protection composite material is a laminated quartz / phenolic composite material formed by hot pressing multiple prepregs according to the thickness of the composite material, wherein the mass fraction of phenolic resin in the prepreg is 45%, and the mass fraction of volatile matter is 5%. The optical fiber sensing technology refers to sensing strain and temperature through the change of grating reflection wavelength in the optical fiber grating sensor. The optical fiber grating sensor is a high-temperature resistant optical fiber grating sensor based on femtosecond laser inscription. The optical fiber grating sensor is divided into two types according to its use: one is a strain-temperature sensor (type I sensor) using a bare grating; the other is a temperature sensor (type II sensor) using a grating encapsulated by a suspended metal capillary tube, and the length of the metal capillary tube is greater than the length of the grating. The grating has a grating zone length of not less than 12mm, a reflectivity of 75%, a 3dB bandwidth of the reflection spectrum of 0.18mm, and a center wavelength of 1550nm.

[0080] The specific steps of the method for preparing the strain sensing heat protection composite material based on optical fiber sensing technology are as follows:

[0081] (1) Quartz / phenolic prepreg pretreatment: vacuum heat treatment is performed on the multilayer quartz / phenolic prepreg, the pretreatment temperature is 60℃, the vacuum degree is 0.07MPa, and the holding time is 6h, so as to realize the improvement of the phenolic resin infiltration performance between the layers of the quartz / phenolic prepreg.

[0082] (2) Packaging of fiber grating sensor between prepreg layers

[0083] The packaging structure diagram of the fiber grating sensor between the layers of the quartz / phenolic prepreg is shown in Figure 1 The method comprises the following steps:

[0084] (2.1) Method for protecting and fixing the grating: method two is used for type I sensor, and method three is used for type II sensor;

[0085] The method two comprises the following steps: in order to avoid the influence of the fabric weaving structure in the prepreg on the measurement accuracy of the grating and the influence of the slippage of the prepreg on the position of the grating during the molding process of the quartz / phenolic composite material, a grating protection sheet is prepared for protecting the grating. The grating protection sheet is a quartz / phenolic composite material body sheet with a thickness of 4mm, and a groove is opened on the sheet. The size of the groove is 2mm in diameter and 2mm in depth. The grating is buried in the groove of the grating protection sheet, and the grating is fixed on the grating protection sheet by using epoxy glue at both ends of the grating. According to the size of the grating protection sheet, a groove is opened on the quartz / phenolic prepreg, and the grating protection sheet is filled in the groove of the quartz / phenolic prepreg, so that the surface of the quartz / phenolic prepreg is flat.

[0086] The method three comprises the following steps: since the grating of the type II sensor has been packaged in the metal capillary, the metal capillary of the type II sensor is fixed on the grating protection sheet or the prepreg by using epoxy glue. The grating of the type II sensor is close to the grating of the type I sensor, and the distance between the two gratings is 3mm.

[0087] (2.2) Protection of fiber grating sensor at the edge of quartz / phenolic prepreg: first, a stainless steel metal capillary is sleeved outside the type I and type II sensors, and then grooves are opened on the upper and lower quartz / phenolic prepreg surfaces in contact with the type I and type II sensors, so that the stainless steel metal capillary is buried in the quartz / phenolic prepreg, and the surface of the stainless steel metal capillary is flush with the quartz / phenolic prepreg in the thickness direction. Finally, epoxy glue is used to fix the edge of the stainless steel metal protection sleeve and the metal capillary opening on the quartz / phenolic prepreg, so as to prevent the phenolic resin from entering the stainless steel metal capillary; optimization measures: in order to avoid the difference in expansion coefficient between the stainless steel tube and the quartz / phenolic composite material after heating, which may cause fiber loss or even breakage, the stainless steel metal capillary is embedded 4mm away from the upper and lower groove positions of the prepreg in the fiber laying direction.

[0088] (2.3) Fiber Bragg grating sensor is drawn from quartz / phenolic prepreg: metal capillary outside quartz / phenolic prepreg, type I and type II sensors are drawn through PVDF hollow tube, the length of PVDF hollow tube is greater than the length of type I and type II sensors, the end of the tube is folded and sealed, the distal end is pasted with paper tape, and the grating wavelength is recorded.

[0089] (3) Curing of quartz / phenolic composite material encapsulating fiber Bragg grating sensor inside: PVDF / glass varnished cloth is first laid on the upper and lower surfaces of the prepreg, and polyimide film is laid. The prepreg is cured by hot press, which includes curing I and curing II; in the curing I, the temperature is 90°C, and the holding time is 1 h; in the curing II, the temperature is 150°C, and the holding time is 2 h; the pressure of curing I and curing II is 1 MPa.

[0090] (4) Post-processing of quartz / phenolic composite material encapsulating fiber Bragg grating sensor inside: after the curing process is completed, the temperature is reduced to 35°C, the composite material is taken out of the hot press, the polyimide film and PVDF / glass varnished cloth on the surface of the composite material are removed, and the PVDF hollow tube outside type I and type II sensors is replaced with a high-temperature resistant protective sleeve, thereby obtaining a strain sensing heat-resistant composite material based on fiber sensing technology.

[0091] The strain sensing heat-resistant composite material based on fiber sensing technology has a retention rate of tensile properties at room temperature of 80% compared to the bulk heat-resistant composite material, a retention rate of thermal conductivity of 85%, and a sensor survival rate of 95%. The composite material not only realizes the heat protection function of heat-resistant materials, but also realizes the internal strain monitoring of heat-resistant materials, providing basic data for health monitoring of heat-resistant materials. The internal strain monitoring of the heat-resistant material is shown in Figure 3 The strain of the heat-resistant composite material during high-temperature pyrolysis is monitored, and the temperature range is room temperature to 700°C. The sensor survival rate of Example 2 is increased by 25% compared to Example 1, and the maximum measurement temperature is increased from 350°C to 700°C, indicating that the sensor packaging method shown in steps (2.1) method two and step (2.2) optimization measures more effectively improves the survival rate and temperature resistance level of the material.

[0092] Example 3

[0093] The heat-proof composite material is a laminated quartz / phenolic composite material, which is hot-pressed from multiple layers of pre-impregnated material according to the thickness of the composite material, wherein the mass fraction of phenolic resin in the pre-impregnated material is 50%, and the mass fraction of volatile matter is 9%. The optical fiber sensing technology refers to sensing strain and temperature through the change of the wavelength of the grating reflected by the optical fiber grating sensor; the optical fiber grating sensor is a high-temperature-resistant optical fiber grating sensor based on femtosecond laser inscription, and the optical fiber grating sensor is divided into two types according to the purpose: one is a strain-temperature sensor (type I sensor), which uses a bare grating; the other is a temperature sensor (type II sensor), which uses a grating suspended and encapsulated by a metal capillary tube, and the length of the metal capillary tube is greater than the length of the grating; the grating has a grating area length of 15 mm, a reflectivity of 80%, a 3dB bandwidth of the reflection spectrum of 0.15 mm, and a central wavelength range of 1570 nm.

[0094] The preparation method of the strain sensing heat-proof composite material based on the optical fiber sensing technology comprises the following specific steps:

[0095] (1) Quartz / phenolic pre-impregnated material pretreatment: vacuum heat treatment is performed on the multiple layers of quartz / phenolic pre-impregnated material, the pretreatment temperature is 70℃, the vacuum degree is 0.09MPa, and the holding time is 4h, so as to improve the phenolic resin infiltration performance between the layers of the quartz / phenolic pre-impregnated material.

[0096] (2) Packaging of optical fiber grating sensor between pre-impregnated material layers

[0097] The packaging structure of the optical fiber grating sensor between the layers of the quartz / phenolic pre-impregnated material is shown in Figure 1 The method comprises the following steps:

[0098] (2.1) Method for protecting and fixing the grating: method two is used for type I sensor, and method three is used for type II sensor;

[0099] The method two comprises the following steps: in order to avoid the influence of the fabric weaving structure in the pre-impregnated material on the measurement accuracy of the grating and the influence of the pre-impregnated material slip on the position of the grating during the molding process of the quartz / phenolic composite material, a grating protection sheet is prepared for protecting the grating. The grating protection sheet is a quartz / phenolic composite material body sheet with a thickness of 8mm, and a groove is opened on the sheet, the size of the groove is 4mm in diameter and 2.5mm in depth. The grating is buried in the groove of the grating protection sheet, and the grating is fixed on the grating protection sheet at both ends using silicone rubber. According to the size of the grating protection sheet, a groove is opened on the quartz / phenolic pre-impregnated material, and the grating protection sheet is filled in the groove of the quartz / phenolic pre-impregnated material, so that the surface of the quartz / phenolic pre-impregnated material is flat.

[0100] The method three includes: since the grating of the type II sensor has been packaged in the metal capillary, the type II sensor metal capillary is fixed on the grating protection sheet or the prepreg using silicon rubber, the grating of the type II sensor is close to the grating of the type I sensor, and the distance between the two gratings is 2 mm.

[0101] (2.2) Protection of the fiber grating sensor at the edge of the quartz / phenolic prepreg: stainless steel metal capillary is first sleeved outside the type I and type II sensors, then the upper and lower quartz / phenolic prepreg surfaces in contact with the type I and type II sensors are slotted, so that the stainless steel metal capillary is embedded in the quartz / phenolic prepreg, the surface thereof is flush with the quartz / phenolic prepreg in the thickness direction, and finally the edge of the stainless steel metal protection sleeve and the metal capillary port are fixed on the quartz / phenolic prepreg using silicon rubber, so as to prevent the phenolic resin from entering the stainless steel metal capillary; in order to avoid the difference in expansion coefficient between the stainless steel tube and the quartz / phenolic composite material after being heated, which causes the fiber loss or even breakage, the stainless steel metal capillary is embedded at a position 2 mm away from the upper and lower slotted positions of the prepreg in the fiber laying direction.

[0102] (2.3) Leading out of the fiber grating sensor from the quartz / phenolic prepreg: the metal capillary outside the quartz / phenolic prepreg, the type I and type II sensors are led out through the PVDF hollow tube, the length of the PVDF hollow tube is greater than the length of the type I and type II sensors, the tube end is folded and sealed, the distal end is pasted with paper tape, and the grating wavelength is recorded.

[0103] (3) Curing of the quartz / phenolic composite material encapsulating the fiber grating sensor: PVDF / glass varnished cloth is first laid on the upper and lower surfaces of the prepreg, and polyimide film is laid; the prepreg is cured by using a hot press, and the curing includes curing I and curing II; in the curing I, the temperature is 100°C, and the holding time is 0.5 h; in the curing II, the temperature is 140°C, and the holding time is 4 h; the pressure of the curing I and the curing II is both 2 MPa.

[0104] (4) Post-processing of the quartz / phenolic composite material encapsulating the fiber grating sensor: after the curing process is completed, when the temperature decreases to 25°C, the composite material is taken out of the hot press, the polyimide film and the PVDF / glass varnished cloth on the surface of the composite material are removed, and the PVDF hollow tube outside the type I and type II sensors is replaced with a high-temperature-resistant protection sleeve, so as to obtain a strain sensing heat-resistant composite material based on fiber sensing technology.

[0105] The prepared strain sensing heat-proof composite material based on optical fiber sensing technology has a normal temperature tensile property retention rate of 90%, a thermal conductivity performance retention rate of 90%, and a sensor survival rate of 90%. The composite material not only realizes the heat protection effect of the heat-proof material, but also realizes the internal strain monitoring of the heat-proof material, thereby providing basic data for health monitoring of the heat-proof material. The internal strain monitoring of the heat-proof material includes, for example Figure 4 The normal temperature long-time strain monitoring of the heat-proof composite material is shown in FIG. 26. The sensor survival rate of Example 3 is increased by 20% compared with that of Example 1, which indicates that the sensor packaging method of method two in step (2.1) is more effective in increasing the survival rate of the material than the sensor packaging method of method one.

Claims

1. A method for preparing a strain-sensing heat-resistant composite material based on optical fiber sensing technology, comprising the following steps: 1) quartz / phenolic prepreg pretreatment: vacuum heat treatment is performed on the multilayer quartz / phenolic prepreg; in the vacuum heat treatment, the temperature is 60-80℃, the vacuum degree is not less than 0.05 MPa, and the holding time is 2-6 h; 2) encapsulation of fiber Bragg grating sensors between layers of the quartz / phenolic prepreg, comprising the following steps 2.1) to 2.3): 2.1) protection and fixation of the grating: type I sensor adopts method one for protection and fixation of the grating; type II sensor adopts method three for protection and fixation of the grating; The method comprises: type I sensor is first buried between layers of the quartz / phenolic prepreg, then the grating is straightened at both ends, and epoxy or silicone rubber is used to fix the grating on the quartz / phenolic prepreg at both ends of the grating; the method three comprises: the stainless steel capillary tube of the type II sensor is fixed on the grating protection sheet or the quartz / phenolic prepreg using epoxy or silicone rubber, and the distance between the grating of the type II sensor and the grating of the type I sensor is not greater than 5 mm; 2.2) protection of the fiber Bragg grating sensor at the edge of the quartz / phenolic prepreg: first, a stainless steel capillary tube is sleeved outside the type I sensor and the type II sensor, then grooves are made on the surfaces of the upper and lower quartz / phenolic prepregs in contact with the type I sensor and the type II sensor, so that the stainless steel capillary tube is buried in the quartz / phenolic prepreg, the surface of the stainless steel capillary tube is flush with the prepreg in the thickness direction, and finally epoxy or silicone rubber is used to fix the edge of the stainless steel capillary tube and the opening of the stainless steel capillary tube on the quartz / phenolic prepreg; 2.3) leading out of the fiber Bragg grating sensor from the quartz / phenolic prepreg: the stainless steel capillary tube outside the quartz / phenolic prepreg, the type I sensor and the type II sensor are led out through a PVDF hollow tube, and the length of the PVDF hollow tube is greater than the length of the type I sensor and the type II sensor, the end of the PVDF hollow tube is folded and sealed, the distal end is pasted with paper tape, and the grating wavelength is recorded; 3) curing: PVDF / glass paint cloth is first laid on the upper and lower surfaces of the quartz / phenolic prepreg, and then polyimide film is laid, and pressure curing is performed using a press or a hot press; the pressure curing comprises curing I and curing II; in the curing I, the temperature is 80-100℃, and the holding time is 0.5-2 h; in the curing II, the temperature is 120-160℃, and the holding time is 2-8 h; the pressure in the curing I and the curing II is 0.5-2 MPa; 4) post-treatment: after the curing in the step 3), when the temperature is reduced to below 40℃, the obtained composite material is taken out from the press or the hot press, the polyimide film and the PVDF / glass paint cloth on the surface of the material are removed, the PVDF hollow tube outside the type I sensor and the type II sensor is replaced with a high-temperature-resistant protective sleeve, and the strain-sensing heat-resistant composite material based on optical fiber sensing technology is obtained. The heat-proof composite material is a laminated quartz / phenolic composite material; The heat-proof composite material is obtained by hot-pressing molding of multiple layers of quartz / phenolic prepreg; In the quartz / phenolic prepreg, the mass fraction of phenolic resin is 40% to 50%, and the mass fraction of volatile matter is 5% to 10%; The type I sensor is a strain-temperature sensor using bare gratings; The type II sensor is a temperature sensor using stainless steel capillary tube to suspend and encapsulate gratings.

2. A method for preparing a strain-sensing heat-proof composite material based on optical fiber sensing technology, comprising the following steps: 1) Quartz / phenolic prepreg pretreatment: vacuum heat treatment is performed on the multiple layers of quartz / phenolic prepreg; In the vacuum heat treatment, the temperature is 60°C to 80°C, the vacuum degree is not less than 0.05 MPa, and the holding time is 2 to 6 hours; 2) Packaging of fiber grating sensors between layers of the quartz / phenolic prepreg, comprising the following steps 2.1) to 2.3): 2.1) Grating protection and fixation: The type I sensor adopts method two for grating protection and fixation; The type II sensor adopts method three for grating protection and fixation; The method two comprises: First, a grating protection sheet is prepared; then, the grating is buried in the groove of the grating protection sheet, and epoxy glue or silicone rubber is used to fix the grating on the grating protection sheet at both ends of the grating; according to the size of the grating protection sheet, a groove is opened on the quartz / phenolic prepreg, the grating protection sheet is filled in the groove of the quartz / phenolic prepreg, and the surface of the quartz / phenolic prepreg is made flat; Method three includes: the stainless steel capillary tube of the type II sensor is fixed in the grating protection sheet or the quartz / phenolic prepreg using epoxy glue or silicone rubber, and the distance between the grating of the type II sensor and the grating of the type I sensor is not greater than 5 mm; 2.2) Protection of fiber grating sensors at the edges of the quartz / phenolic prepreg: First, a stainless steel capillary tube is sleeved outside the type I sensor and the type II sensor, then grooves are opened on the surfaces of the upper and lower quartz / phenolic prepregs in contact with the type I sensor and the type II sensor, so that the stainless steel capillary tube is buried in the quartz / phenolic prepreg, the surface of the stainless steel capillary tube is flush with the prepreg in the thickness direction, and finally epoxy glue or silicone rubber is used to fix the edges of the stainless steel capillary tube and the mouth of the stainless steel capillary tube on the quartz / phenolic prepreg; 2.3) Extraction of fiber grating sensors from the quartz / phenolic prepreg: The stainless steel capillary tube, the type I sensor and the type II sensor outside the quartz / phenolic prepreg are extracted through a PVDF hollow tube, and the length of the PVDF hollow tube is greater than the length of the type I sensor and the type II sensor, the end of the PVDF hollow tube is folded and sealed, the far end is pasted with paper tape, and the grating wavelength is recorded; 3) Curing: PVDF / glass paint cloth is first laid on the upper and lower surfaces of the quartz / phenolic prepreg, and then polyimide film is laid, and pressure curing is performed using a press or a hot press; The pressure curing includes curing I and curing II; The temperature in the curing I is 80-100℃; the holding time is 0.5-2h; The temperature in the curing II is 120-160℃; the holding time is 2-8h; The pressure in the curing I and curing II is 0.5-2MPa; 4) Post-treatment: After the curing in the step 3), when the temperature is lowered to below 40℃, the obtained composite material is taken out from the press or autoclave, the polyimide film and PVDF / glass paint cloth on the surface of the material are removed, the PVDF hollow tube outside the type I sensor and type II sensor is replaced with a high-temperature resistant protective sleeve to obtain the strain sensing heat-proof composite material based on the optical fiber sensing technology; The heat-proof composite material is a laminated quartz / phenolic composite material; The heat-proof composite material is obtained by hot pressing molding of multiple layers of quartz / phenolic prepreg; In the quartz / phenolic prepreg, the mass fraction of phenolic resin is 40-50%, and the mass fraction of volatile matter is 5-10%. The type I sensor is a strain-temperature sensor using bare gratings; The type II sensor is a temperature sensor using a stainless steel capillary tube to suspend and encapsulate the grating.

3. The method according to claim 1 or 2, characterized in that: In the step 1) vacuum heat treatment, the temperature is 70-75℃.

4. The method according to claim 1 or 2 or 3, characterized in that: In the step 2.1), the grating protection sheet is a slotted quartz / phenolic composite material body sheet with a thickness of 4-8mm; the size of the slot is 2-4mm in diameter and 1.5-2.5mm in depth.

5. The method according to any of claims 1 to 4, characterized in that: In the step 2.2), the stainless steel capillary tube is embedded at a distance of 0.5-6mm from the upper and lower slotted positions on the quartz / phenolic prepreg in the fiber laying direction.

6. The method of any one of claims 1-4, wherein: In the step 3), the temperature of curing I is 90℃, and the holding time is 1h; The temperature of curing II is 140-150℃, and the holding time is 2-4h; The curing pressure is 1MPa.

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