An optical fiber monitoring device for curing distortion of an ultra-thick foam sandwich composite member, an optical fiber laying method, and a monitoring method

Abstract

The application provides a fiber monitoring device for curing deformation of an ultra-thick foam sandwich composite component, a fiber laying method and a monitoring method. The device comprises a flat mold, a foam core layer with a chamfer on one side, a plurality of cut pre-impregnated materials and a fiber protection mold. The device and method widen the use range of the fiber grating sensor in the curing monitoring field, and are used for the thicker composite components such as the ultra-thick foam sandwich composite component. The fiber protection mold and the improved fiber laying method are used to realize real-time monitoring of the temperature and strain in the curing process of the ultra-thick foam sandwich component.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fiber monitoring of curing deformation of super-thick foam sandwich composite components, in particular to an optical fiber monitoring device for curing deformation of super-thick foam sandwich composite components, a fiber laying method and a monitoring method, and more particularly to an online monitoring device for curing deformation of super-thick foam sandwich composite components with embedded fiber grating sensors in a autoclave molding process, and a fiber laying and monitoring method BACKGROUND

[0002] Resin-based composite materials have the advantages of high strength, high temperature resistance, corrosion resistance and strong designability, and have been widely used in the field of aerospace. In order to further pursue lightweight, honeycomb and foam are usually used as the internal core layer of composite structural parts. As a typical porous material, foam can greatly increase the strength and bending resistance of the structure when used as the core layer of the sandwich structure. Foam sandwich structural parts are mainly molded by autoclave co-curing. During the manufacturing process, the sandwich structure is generally cured at 180 DEG C. Due to the mismatch of the thermal expansion coefficients of the foam and the composite material panel, residual stress will be generated when cooled to the working temperature. The thermal hysteresis and temperature gradient caused by heat release of resin curing will cause uneven curing of the composite structure, which will exacerbate the residual stress of the structure, and even cause deformation after the structure is demolded, which seriously affects the performance of the foam sandwich composite component. Larger deformation makes the part size not up to standard, which brings difficulties to assembly. Therefore, it is very important for production and application to monitor the temperature and strain of the foam sandwich composite component during the autoclave curing molding process and then improve the process to reduce the curing deformation of the part.

[0003] Current fiber grating sensor (i.e. FBG sensor) curing monitoring is mainly applied to flat plate type composite components. For super-thick foam sandwich composite components, according to the traditional fiber laying method, the angle is too large, which will cause signal interruption, and the temperature and strain data during the curing process of the super-thick foam sandwich component cannot be collected. Therefore, improving the fiber laying method and using fiber protection mold can avoid signal interruption caused by too large angle, which is very important for the curing monitoring of super-thick foam sandwich composite components. SUMMARY

[0004] The present application aims to solve the problems of laying difficulty and signal interruption of fiber grating sensors when monitoring the curing deformation of super-thick foam sandwich composite components, and proposes an optical fiber monitoring device for curing deformation of super-thick foam sandwich composite components, a fiber laying method and a monitoring method. Thus, the real-time monitoring of temperature and strain during the autoclave curing molding process of super-thick foam sandwich composite components is realized.

[0005] The application is realized by the following technical scheme, the application provides a kind of optical fiber monitoring device of curing deformation of super-thick foam sandwich composite component, the device includes flat plate mould, one side chamfered foam core layer, several cut pre-impregnated and optical fiber protection mould;Pre-impregnated and foam core layer are sequentially laid on flat plate mould, fiber grating sensor is buried between pre-impregnated layer, optical fiber lead is laid along foam chamfered side, optical fiber protection mould is placed at foam chamfered, mould center recess is opposite the optical fiber lead of fiber grating sensor, and play the protection function;Optical fiber lead is led out from the optical fiber interface in autoclave, is connected with fiber grating demodulator, fiber grating demodulator is further connected with computer, and the monitoring data of fiber grating sensor is collected in real time.

[0006] Further, the grating area of fiber grating sensor is packaged in capillary steel pipe as temperature sensor, and is laid in parallel 3-5mm beside it without any treatment as strain sensor, so as to monitor temperature and strain in the curing process of component in real time.

[0007] Further, the foam is chamfered 45° on one side, and the fiber grating sensor is laid along the chamfered part of foam.

[0008] Further, the material of optical fiber protection mould is aluminum, the chamfered angle is 45°, and it is placed at the chamfered part of foam before vacuum bag sealing, and the mould center recess is opposite the optical fiber of fiber grating sensor, to play the protection function.

[0009] Further, the center wavelength of fiber grating sensor is 1535-1560nm.

[0010] Further, fiber grating demodulator has four channels, and at least four fiber grating sensors can be simultaneously collected at a time.

[0011] Further, four fiber grating sensors are used for curing monitoring at a time, the grating area of two fiber grating sensors is protected by capillary steel pipe to make temperature sensor, and one temperature sensor and one strain sensor are laid in parallel at a distance of 3-5mm along the fiber direction in the center of a layer of pre-impregnated in actual use.

[0012] The application also provides a laying method of optical fiber in the optical fiber monitoring device, and the method comprises:

[0013] Step one: build the optical fiber monitoring network: the fiber grating sensor needs to be calibrated before use, and the temperature sensitivity coefficient and strain sensitivity coefficient of the fiber grating sensor are obtained; first, connect the fiber grating sensor with the fiber grating demodulator, when connecting the optical fiber, first cut off the end face of the optical fiber with an optical fiber cutting knife, then connect the optical fiber together with an optical fiber fusion splicer, and fix the optical fiber joint position with a heat shrink tube; after connecting, send the fiber grating sensor from the optical fiber interface of the hot press tank into the tank, and wait to be embedded in the measured component;

[0014] Step two: lay the material and pre-embed the optical fiber: first clean the surface of the optical fiber protection mold, then lay a layer of release cloth on the surface, and then lay the pre-impregnated material; pay attention to the direction of the laid layer during the laying process, manually compact after laying each layer of pre-impregnated material, and try to expel excess air, lay a layer of adhesive film between the foam core layer and the upper and lower skins; lay the fiber grating sensor between the pre-impregnated material laid on the foam upper layer, and lay the temperature sensor and strain sensor parallelly at a distance of 3-5mm in the middle of the pre-impregnated material; after completing the laying of the pre-impregnated material, lay the release film, release cloth and air-permeable felt in sequence on the upper layer, and finally place the optical fiber protection mold at the foam chamfer, and the center groove of the optical fiber protection mold is opposite to the optical fiber of the fiber grating sensor.

[0015] The application also provides a monitoring method based on the optical fiber monitoring device, and the method comprises:

[0016] Step one, calibrate the fiber grating sensor to measure the temperature sensitivity coefficient and strain sensitivity coefficient;

[0017] Step two, connect the fiber grating sensor with the fiber grating demodulator, then send the grating end of the fiber grating sensor into the hot press tank from the optical fiber interface of the hot press tank; the fiber grating demodulator has four channels, four fiber grating sensors are used for curing monitoring at a time, the grating area of two fiber grating sensors is protected with a capillary steel pipe to form a temperature sensor, and one temperature sensor and one strain sensor are laid parallelly at a distance of 3-5mm in the center of a layer of pre-impregnated material along the fiber direction in actual use; when connecting the optical fiber, first cut off the end face of the optical fiber with an optical fiber cutting knife, then connect the optical fiber together with an optical fiber fusion splicer, and fix the optical fiber joint position with a heat shrink tube;

[0018] Step 3: embed the fiber grating sensor into the interior of the ultra-thick foam sandwich composite component; chamfer one side of the foam core layer by 45 degrees, and cut the foam, prepreg, film and auxiliary materials as required; first clean the surface of the fiber protection mold, stick a layer of demoulding cloth on the surface, and then lay the prepreg in the order of laying. Pay attention to the laying direction during the laying process. After laying each layer of prepreg, manually compact it to expel excess air as much as possible, and lay a layer of film between the foam core layer and the upper and lower skins; when pre-embedding the fiber grating sensor in the lower layer of foam prepreg, directly lead it out along the fiber direction; when monitoring the upper layer of foam prepreg, lay the optical fiber lead of the fiber grating sensor along the chamfered side of the foam; when laying the fiber grating sensor, fix the fiber grating sensor in the monitoring position, and then continue to lay the prepreg in the order of laying; after the laying and pre-embedding of the optical fiber are completed, lay the isolation film, demoulding cloth and breathable felt on the structure in sequence according to the vacuum bag molding process;

[0019] Step 4: Start curing after the vacuum bag is sealed; after laying the materials in sequence, stick a circle of sealing strips around the optical fiber protection mold, and wrap the optical fiber lead-out line of the fiber optic Bragg grating sensor in the sealant; place a vacuum suction cup on the optical fiber protection mold near the mouth of the autoclave, and then seal it with a vacuum bag. When sealing, pleat the foam sandwich structure; send the encapsulated device into the autoclave, and then connect the vacuum pipe of the autoclave to vacuumize it and check the airtightness of the device; connect the fiber optic Bragg grating demodulator to the computer, open the data acquisition software, process the data collected by the fiber optic Bragg grating sensor, and obtain the temperature and strain of the foam sandwich structure during the curing process.

[0020] Furthermore, the fiber Bragg grating demodulator has a frequency of 1000 Hz, that is, it outputs one data every 1 ms.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The device and method described in the present invention broaden the scope of use of fiber grating sensors in the field of curing monitoring. For thicker composite components such as ultra-thick foam sandwich composite components, the optical fiber protection mold and the improved optical fiber laying method are used to realize real-time monitoring of the temperature and strain during the curing process of ultra-thick foam sandwich components. First, if the optical fiber adopts the traditional laying method, when the component thickness is large, the optical fiber lead will have a signal interruption due to the large curing pressure and bending angle. The method described in the present invention can avoid this phenomenon and ensure that the optical fiber signal of the ultra-thick foam sandwich composite component is stable and will not be interrupted during the entire curing process. Secondly, the optical fiber protection mold proposed in the present invention is simple to make and low in cost, and can be manufactured according to different component thicknesses and angles. Finally, the method is also applicable to the curing monitoring of other ultra-thick sandwich components. The use of optical fiber grating sensors to monitor temperature and strain has high accuracy, which greatly expands the application of optical fiber grating sensors in the field of curing monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0024] Figure 1 This is a schematic diagram of the optical fiber protection mold;

[0025] Figure 2 This is a schematic diagram of laying out the fiber Bragg grating sensor;

[0026] Figure 3 Schematic diagram of the optical fiber monitoring device for autoclave curing deformation of ultra-thick foam sandwich composite components. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] Combine Figures 1-3 The present invention proposes a fiber optic monitoring device for curing deformation of ultra-thick foam sandwich composite components. The device comprises a flat mold, a foam core layer with a chamfer on one side, a plurality of cut prepregs, and a fiber protection mold. The prepregs and foam core layers are laid on the flat mold in a certain order. The fiber optic Bragg grating (FBG) sensor is embedded between the prepreg layers. The fiber lead is laid along the chamfered side of the foam. The fiber protection mold is placed at the chamfered corner of the foam. The center groove of the mold faces the fiber lead of the FBG sensor to provide protection. The fiber lead is led out from the fiber interface in the autoclave and connected to a fiber optic Bragg grating (FBG) demodulator. The FBG demodulator is then connected to a computer to collect monitoring data from the FBG sensor in real time. The center wavelength of the FBG sensor is 1535-1560nm.

[0029] Because fiber Bragg grating sensors are affected by both temperature and strain, they must be decoupled to obtain a single variable. In practice, the grating region of the fiber Bragg grating sensor is encapsulated in a capillary steel tube as a temperature sensor, while a 3-5 mm parallel, untreated strain sensor is placed adjacent to it to monitor temperature and strain in real time during component curing. FBG sensors require experimental calibration before use.

[0030] Because the FBG sensor transmits data through the optical fiber channel, the optical fiber embedded in the component is not wrapped by a wire, and when the angle of the optical fiber is too large, the optical fiber lead is affected by the curing pressure, which can cause signal interruption. In order to avoid this phenomenon, the foam is chamfered at one side by 45°, and the FBG sensor is laid along the chamfered part of the foam. Meanwhile, a fiber protection mold is designed, the material of the fiber protection mold is aluminum, the chamfer angle is 45°, and the mold is placed at the chamfered part of the foam before the vacuum bag is sealed, the center groove of the mold is opposite to the optical fiber of the FBG sensor, and the mold plays a protection role.

[0031] The fiber grating demodulator has four channels, and at least four fiber grating sensors can be simultaneously collected at a time. The application adopts four fiber grating sensors for curing monitoring at a time, and the grating area of two fiber grating sensors is protected by a capillary steel pipe to form a temperature sensor. In actual use, a temperature sensor and a strain sensor are laid in parallel on the center of a layer of prepreg along the fiber direction and are spaced apart by 3-5 mm.

[0032] The application further provides a laying method of the optical fiber in the fiber monitoring device.

[0033] Step one: build a fiber monitoring network: the fiber grating sensor needs to be calibrated before use to obtain the temperature sensitivity coefficient and the strain sensitivity coefficient of the fiber grating sensor; first, connect the fiber grating sensor with the fiber grating demodulator, when connecting the optical fiber, first cut the end face of the optical fiber by using an optical fiber cutting knife, then connect the optical fiber together by using an optical fiber fusion splicer, and fix the optical fiber joint position by using a heat shrink tube; after the connection is completed, send the fiber grating sensor into the tank from the optical fiber interface of the autoclave, and wait to be embedded in the measured component.

[0034] Step two: lay the material and pre-embed the optical fiber: first, clean the surface of the optical fiber protection mold, then lay a layer of release cloth on the surface, and then lay the prepreg; pay attention to the laying direction during the laying process, manually compact after laying each layer of prepreg, and try to expel the excess air, lay a layer of adhesive film between the foam core layer and the upper and lower skins; lay the fiber grating sensor between the prepregs laid on the upper layer of the foam, and lay the temperature sensor and the strain sensor in parallel in the middle of the prepreg and spaced apart by 3-5 mm; after the prepreg is laid, lay the release film, the release cloth and the air-permeable felt in sequence on the upper layer, and finally place the optical fiber protection mold at the chamfered part of the foam, and the center groove of the optical fiber protection mold is opposite to the optical fiber of the fiber grating sensor.

[0035] The application further provides a monitoring method based on the fiber monitoring device.

[0036] Step one: calibrate the fiber grating sensor to measure the temperature sensitivity coefficient and the strain sensitivity coefficient;

[0037] Step two, connect the fiber Bragg grating sensor with the fiber Bragg grating demodulator, then send the fiber Bragg grating sensor with the grating into the autoclave from the fiber interface of the autoclave; the center wavelength of the FBG sensor is 1535-1560nm, the fiber Bragg grating demodulator has four channels, and at least four FBG sensors can be collected at the same time, for example, four FBG sensors are used for curing monitoring at the same time, two FBG sensors are used to make temperature sensors by protecting the grating area with capillary steel pipes, and in actual use, a temperature sensor and a strain sensor are laid parallel on the center of a layer of prepreg along the fiber direction with a distance of 3-5mm; when connecting the optical fiber, first cut the end face of the optical fiber with an optical fiber cutting knife, then connect the optical fiber together with an optical fiber fusion splicer, and fix the optical fiber joint position with a heat shrink tube;

[0038] Step three, bury the fiber Bragg grating sensor in the ultra-thick foam sandwich composite component; in order to facilitate the laying of the optical fiber, the foam core layer is chamfered at 45° on one side, and the foam, prepreg, adhesive film and auxiliary materials are cut according to the requirements; first clean the surface of the optical fiber protection mold, then paste a layer of release cloth on the surface, then lay and paste the prepreg according to the layering sequence, pay attention to the layering direction during the laying process, manually compact after laying each layer of prepreg, and try to expel excess air, and lay a layer of adhesive film between the foam core layer and the upper and lower skins; when embedding the fiber Bragg grating sensor in the lower layer of foam prepreg, the fiber Bragg grating sensor can be directly led out along the fiber direction; when monitoring the upper layer of foam prepreg, the fiber Bragg grating sensor is laid along the chamfered side of the foam, as shown in Figure 2 When laying the fiber Bragg grating sensor, the fiber Bragg grating sensor is fixed at the monitoring position due to the certain viscosity of the prepreg, and then the prepreg is continuously laid according to the layering sequence; after laying and embedding the optical fiber, the release film, release cloth and air-permeable felt are sequentially laid on the structure according to the vacuum bag molding process;

[0039] Step four, start curing after sealing the vacuum bag; after laying the materials in sequence, paste a circle of sealing tape around the optical fiber protection mold, wrap the fiber lead-out wire of the fiber Bragg grating sensor in the sealing glue; place a vacuum chuck near the opening of the autoclave on the optical fiber protection mold, then seal with a vacuum bag, and pleat when sealing at the foam sandwich structure; send the packaged device into the autoclave, then connect the vacuum pipeline of the autoclave for vacuumizing treatment, and check the air tightness of the device; connect the fiber Bragg grating demodulator with the computer, open the data acquisition software, and the initial wavelength data of the four channels can be seen. The frequency of the fiber Bragg grating demodulator is 1000Hz, that is, one data is output per 1ms, after all preparations are completed, close the door, and set the curing process temperature and process pressure. The schematic diagram of the fiber monitoring device for the curing deformation of the ultra-thick foam sandwich composite component autoclave is shown in Figure 3 The data collected by the fiber Bragg grating sensor is processed to obtain the temperature and strain of the foam sandwich structure during the curing process.

[0040] When the optical fiber lead is protected by the optical fiber protection mold, since the FBG sensor transmits data through the optical fiber channel, the optical fiber embedded in the member is not wrapped by a wire, and when the angle of the optical fiber is too large, the signal will be interrupted. Meanwhile, the foam sandwich member is thick, and there is the influence of curing pressure. In order to prevent the optical fiber from causing signal interruption due to the angle being too large at the foam chamfer, the optical fiber protection mold shown in Figure 1 The material of the optical fiber protection mold is aluminum, the chamfer angle is 45°, and before the vacuum bag is sealed, it is placed at the foam chamfer. The center groove of the mold is opposite to the optical fiber of the FBG sensor, and plays a protection role.

[0041] The above describes in detail the optical fiber monitoring device, the optical fiber laying method and the monitoring method for the curing deformation of the super-thick foam sandwich composite member proposed in the present application. In this paper, specific examples are applied to explain the principles and implementation modes of the present application. The above examples are only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. An optical fiber monitoring device for curing deformation of ultra-thick foam sandwich composite materials, characterized in that: The device includes a flat mold, a foam core layer with a chamfer on one side, a plurality of cut prepregs and an optical fiber protection mold; the prepreg and the foam core layer are laid on the flat mold in sequence, the fiber optic Bragg grating sensor is buried between the prepreg layers, the optical fiber lead is laid along the chamfered side of the foam, the optical fiber protection mold is placed at the foam chamfer, and the central groove of the mold is directly opposite the optical fiber lead of the fiber optic Bragg grating sensor to play a protective role; the optical fiber lead is led out from the optical fiber interface in the autoclave and connected to the fiber optic Bragg grating demodulator, which is then connected to a computer to collect monitoring data of the fiber optic Bragg grating sensor in real time.

2. The optical fiber monitoring device according to claim 1, characterized in that: The grating area of ​​the fiber Bragg grating sensor is encapsulated in a capillary steel tube as a temperature sensor, and a strain sensor is laid 3-5 mm parallel to it without any treatment, so as to monitor the temperature and strain of the component in real time during the curing process.

3. The optical fiber monitoring device according to claim 1, characterized in that: One side of the foam is chamfered at 45°, and the fiber optic Bragg grating sensor is laid along the chamfer of the foam.

4. The optical fiber monitoring device according to claim 1, characterized in that: The fiber protection mold is made of aluminum with a chamfer angle of 45°. Before the vacuum bag is sealed, it is placed on the foam chamfer, with the center groove of the mold facing the optical fiber of the fiber grating sensor to play a protective role.

5. The optical fiber monitoring device according to claim 1, characterized in that: The central wavelength of the fiber Bragg grating sensor is 1535-1560nm.

6. The optical fiber monitoring device according to claim 1, characterized in that: The fiber Bragg grating interrogator has four channels and can collect data from at least four fiber Bragg grating sensors at the same time.

7. The optical fiber monitoring device according to claim 6, characterized in that: Four fiber Bragg grating sensors are used for curing monitoring at a time. The grating areas of two of the fiber Bragg grating sensors are protected by capillary steel tubes to form temperature sensors. In actual use, a temperature sensor and a strain sensor are laid parallel to the center of a layer of prepreg along the fiber direction with a distance of 3-5 mm.

8. A method for laying optical fiber in an optical fiber monitoring device according to any one of claims 1 to 7, characterized in that: The method comprises: Step 1: Build a fiber optic monitoring network: The fiber grating sensor needs to be calibrated before use to obtain the temperature sensitivity coefficient and strain sensitivity coefficient of the fiber grating sensor; first connect the fiber grating sensor to the fiber grating demodulator. When connecting the optical fiber, first use a fiber cleaver to cut the fiber end face, then use a fiber optic fusion splicer to connect the optical fibers together, and fix the optical fiber joint position with heat shrink tubing. After the connection is completed, the fiber grating sensor is sent into the autoclave through the optical fiber interface of the autoclave and waits to be buried in the component to be tested; Step 2: Laying materials and pre-embedded optical fiber: First, clean the surface of the optical fiber protection mold, apply a layer of release cloth on the surface, and then lay the prepreg; pay attention to the laying direction during the laying process, and manually compact each layer of prepreg after laying to expel excess air as much as possible, and lay a layer of adhesive film between the foam core layer and the upper and lower skins; lay the fiber optic Bragg grating sensor between the prepregs laid on the upper layer of foam, and lay the temperature sensor and strain sensor in parallel at a distance of 3-5mm in the middle of the prepreg; after the prepreg is laid, lay the isolation film, release cloth and breathable felt on top in sequence, and finally place the optical fiber protection mold on the chamfer of the foam, with the center groove of the optical fiber protection mold facing the optical fiber of the optical fiber Bragg grating sensor.

9. A monitoring method based on the optical fiber monitoring device according to any one of claims 1 to 7, characterized in that: The method comprises: Step 1: Calibrate the fiber Bragg grating sensor and measure the temperature sensitivity coefficient and strain sensitivity coefficient; Step 2: Connect the fiber Bragg grating sensor to the fiber Bragg grating demodulator, and then feed the fiber Bragg grating end of the fiber Bragg grating sensor into the autoclave through the fiber interface of the autoclave; the fiber Bragg grating demodulator has four channels, and four fiber Bragg grating sensors are used for curing monitoring at a time. The grating areas of two of the fiber Bragg grating sensors are protected with capillary steel tubes to form temperature sensors. In actual use, a temperature sensor and a strain sensor are laid parallel to each other in the center of a layer of prepreg, 3-5 mm apart along the fiber direction; when connecting the optical fibers, first use a fiber cleaver to cut the fiber end face, then use a fiber fusion splicer to connect the optical fibers together, and fix the optical fiber joint position with heat shrink tubing; Step 3: embed the fiber grating sensor into the interior of the ultra-thick foam sandwich composite component; chamfer one side of the foam core layer by 45 degrees, and cut the foam, prepreg, film and auxiliary materials as required; first clean the surface of the fiber protection mold, stick a layer of demoulding cloth on the surface, and then lay the prepreg in the order of laying. Pay attention to the laying direction during the laying process. After laying each layer of prepreg, manually compact it to expel excess air as much as possible, and lay a layer of film between the foam core layer and the upper and lower skins; when pre-embedding the fiber grating sensor in the lower layer of foam prepreg, directly lead it out along the fiber direction; when monitoring the upper layer of foam prepreg, lay the optical fiber lead of the fiber grating sensor along the chamfered side of the foam; when laying the fiber grating sensor, fix the fiber grating sensor in the monitoring position, and then continue to lay the prepreg in the order of laying; after the laying and pre-embedding of the optical fiber are completed, lay the isolation film, demoulding cloth and breathable felt on the structure in sequence according to the vacuum bag molding process; Step 4: Start curing after the vacuum bag is sealed; after laying the materials in sequence, stick a circle of sealing strips around the optical fiber protection mold, and wrap the optical fiber lead-out line of the fiber optic Bragg grating sensor in the sealant; place a vacuum suction cup on the optical fiber protection mold near the mouth of the autoclave, and then seal it with a vacuum bag. When sealing, pleat the foam sandwich structure; send the encapsulated device into the autoclave, and then connect the vacuum pipe of the autoclave to vacuumize it and check the airtightness of the device; connect the fiber optic Bragg grating demodulator to the computer, open the data acquisition software, process the data collected by the fiber optic Bragg grating sensor, and obtain the temperature and strain of the foam sandwich structure during the curing process.

10. The method according to claim 9, characterized in that The fiber Bragg grating demodulator has a frequency of 1000 Hz, that is, it outputs one data every 1 ms.

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