Optical fiber monitoring device, optical fiber laying method and monitoring method for curing deformation of super-thick foam sandwich composite material component

Abstract

The invention provides an optical fiber monitoring device, an optical fiber laying method and a monitoring method for curing deformation of a super-thick foam sandwich composite material component. The device comprises a flat plate mold, a foam core layer with a chamfer on one side, a plurality of cut prepregs and an optical fiber protection mold. According to the device and the method, the application range of the fiber grating sensor in the curing monitoring field is widened, and the temperature and the strain in the curing process of the super-thick foam sandwich component are monitored in real time by using the optical fiber protection mold and the improved optical fiber laying method for relatively thick composite components such as the super-thick foam sandwich component.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber monitoring of curing deformation of ultra-thick foam sandwich composite materials, and in particular to an optical fiber monitoring device, optical fiber laying method and monitoring method for curing deformation of ultra-thick foam sandwich composite materials. Specifically, it relates to an online monitoring device for curing deformation of ultra-thick foam sandwich composite materials with pre-embedded optical fiber grating sensors in an autoclave molding process, and an optical fiber laying and monitoring method. Background Art

[0002] Resin-based composite materials have the advantages of high strength, high temperature resistance, corrosion resistance and strong designability. They have been widely used in the aerospace field. At the same time, in order to further pursue lightweight, honeycombs and foams 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 it is used as the core layer of the sandwich structure. Foam sandwich structural parts are mainly co-cured by autoclaves. During the manufacturing process, the sandwich structure is generally cured at 180°C. Due to the mismatch in the thermal expansion coefficients of the foam and the composite panel, residual stress will be generated by cooling to the working temperature. The temperature gradient caused by the thermal hysteresis and heat release of the resin curing will cause uneven curing of the composite structure, which will aggravate the residual stress of the structure and even cause deformation after the structure is demoulded. This seriously affects the performance of the foam sandwich composite component. The large deformation makes the part size substandard and brings difficulties to assembly. Therefore, it is very important for production and application to monitor the temperature and strain during the autoclave curing molding of the foam sandwich composite component, and then improve the process to reduce the curing deformation of the part.

[0003] At present, fiber Bragg grating sensors (FBG sensors) are mainly used for curing monitoring of flat composite components. For ultra-thick foam sandwich composite components, due to their thickness, the traditional fiber laying method will cause signal interruption due to excessive angles, and it is impossible to collect temperature and strain data during the curing process of ultra-thick foam sandwich components. Therefore, improving the fiber laying method and using fiber protection molds can avoid signal interruption due to excessive angles, which is very important for curing monitoring of ultra-thick foam sandwich composite components. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that fiber grating sensors are difficult to lay and signals are easily interrupted when monitoring the curing deformation of ultra-thick foam sandwich composite materials, and propose an optical fiber monitoring device, optical fiber laying method and monitoring method for curing deformation of ultra-thick foam sandwich composite materials. In this way, real-time monitoring of temperature and strain during the autoclave curing molding process of ultra-thick foam sandwich composite materials can be achieved.

[0005] The present invention is realized by the following technical scheme. The present invention proposes an optical fiber monitoring device for curing deformation of an ultra-thick foam sandwich composite material component. The device comprises 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 optical fiber grating sensor is buried between the prepreg layers, the optical fiber lead is laid along the foam chamfer side, the optical fiber protection mold is placed at the foam chamfer, and the central groove of the mold is directly opposite to the optical fiber lead of the optical fiber 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 optical fiber grating demodulator, and the optical fiber grating demodulator is then connected to a computer to collect monitoring data of the optical fiber grating sensor in real time.

[0006] Furthermore, the grating area of ​​the fiber 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.

[0007] Furthermore, one side of the foam is chamfered at 45 degrees, and the fiber grating sensor is laid along the chamfer of the foam.

[0008] Furthermore, the optical fiber protection mold is made of aluminum with a chamfer angle of 45°. Before the vacuum bag is sealed, it is placed at the chamfer of the foam, and the center groove of the mold faces the optical fiber of the fiber grating sensor to play a protective role.

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

[0010] Furthermore, the fiber Bragg grating demodulator has four channels and can collect data from at least four fiber Bragg grating sensors simultaneously at one time.

[0011] Furthermore, four fiber grating sensors are used for curing monitoring at one time, and the grating areas of two of the fiber grating sensors are protected by capillary steel tubes to form temperature sensors. In actual use, a temperature sensor and a strain sensor are laid in parallel at a distance of 3-5 mm along the fiber direction in the center of a layer of prepreg.

[0012] The present invention also provides a method for laying optical fiber in the optical fiber monitoring device, the method comprising:

[0013] Step 1: Build a fiber monitoring network: The fiber Bragg grating sensor needs to be calibrated before use to obtain the temperature sensitivity coefficient and strain sensitivity coefficient of the fiber Bragg grating sensor; first connect the fiber Bragg grating sensor to the fiber Bragg grating demodulator. When connecting the optical fiber, first use a fiber optic cutter 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 a heat shrink tube. After the connection is completed, the fiber Bragg grating sensor is sent into the autoclave from the optical fiber interface of the autoclave, waiting to be buried in the component to be tested;

[0014] Step 2: Laying materials and pre-embedded optical fiber: First, clean the surface of the optical fiber protection mold, stick a layer of release cloth on the surface, and then lay the prepreg; pay attention to the laying direction during the laying process, and compact it manually after laying each layer of prepreg 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 in the middle of the prepreg at a distance of 3-5mm; after the prepreg is laid, lay the isolation film, release cloth and breathable felt on top in turn, 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.

[0015] The present invention also proposes a monitoring method based on the optical fiber monitoring device, the method comprising:

[0016] Step 1: calibrate the fiber Bragg grating sensor and measure the temperature sensitivity coefficient and the strain sensitivity coefficient;

[0017] Step 2: Connect the fiber grating sensor to the fiber grating demodulator, and then send the end of the fiber grating sensor with the grating into the autoclave from the fiber interface of the autoclave; the fiber grating demodulator has four channels, and four fiber grating sensors are used for curing monitoring at a time. The grating areas of two of the fiber grating sensors are protected by capillary steel tubes to form temperature sensors. When actually used, a temperature sensor and a strain sensor are laid in parallel at a distance of 3-5 mm along the fiber direction in the center of a layer of prepreg; when connecting the optical fiber, first use a fiber optic cutter to cut off the end face of the optical fiber, and then use a fiber optic fusion splicer to connect the optical fibers together, and fix them with a heat shrink tube at the optical fiber joint position;

[0018] Step 3, embed the fiber grating sensor into the interior of the ultra-thick foam sandwich composite material 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 optical 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, compact it manually 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 at 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 in sequence on the structure according to the vacuum bagging 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 optical fiber Bragg grating sensor in the sealant; place a vacuum suction cup near the mouth of the autoclave on the optical fiber protection mold, and then seal it with a vacuum bag. When sealing, pleat the foam sandwich structure; send the packaged device into the autoclave, and then connect the vacuum pipe of the autoclave to evacuate the vacuum, and check the air tightness of the device; connect the optical fiber Bragg grating demodulator to the computer, open the data acquisition software, process the data collected by the optical fiber Bragg grating sensor, and obtain the temperature and strain of the foam sandwich structure during the curing process.

[0020] Furthermore, the frequency of the fiber grating demodulator is 1000 Hz, that is, one data is output 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 fiber optic protection mold and the improved fiber optic 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 thickness of the component 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 manufacture 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 fiber optic grating sensors to monitor temperature and strain has high accuracy, which greatly expands the application of fiber optic 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying 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 grating sensor;

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

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Combination Figure 1-Figure 3 The present invention proposes an optical fiber monitoring device for curing deformation of ultra-thick foam sandwich composite material components, 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 a certain order, the fiber 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 chamfer of the foam, and the center groove of the mold is directly opposite to the optical fiber lead of the fiber 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 grating demodulator, which is then connected to the computer to collect the monitoring data of the fiber grating sensor in real time. The central wavelength of the fiber grating sensor is 1535-1560nm.

[0029] Since fiber Bragg grating sensors are affected by both temperature and strain, it is necessary to decouple temperature and strain to obtain a single variable. In actual use, the grating area of ​​the fiber Bragg grating sensor is encapsulated in a capillary steel tube as a temperature sensor, and the grating area 3-5mm away from it is laid parallel to it without any treatment as a strain sensor, so as to monitor the temperature and strain of the component during the curing process in real time. FBG sensors need to be calibrated experimentally before use.

[0030] Since the FBG sensor transmits data through the optical fiber channel, the optical fiber embedded in the component is not wrapped with wire. When the optical fiber angle is too large, the optical fiber lead is affected by the curing pressure, which will cause signal interruption. In order to avoid this phenomenon, one side of the foam is chamfered 45°, and the FBG sensor is laid along the chamfer of the foam. At the same time, a fiber protection mold is designed. The fiber protection mold material is aluminum, and the chamfer angle is 45°. Before the vacuum bag is sealed, it is placed on the chamfer of the foam. The center groove of the mold is facing the optical fiber of the FBG sensor, which plays a protective role.

[0031] The fiber Bragg grating demodulator has four channels and can collect data from at least four fiber Bragg grating sensors at the same time. The present invention uses four fiber Bragg grating sensors for curing monitoring at one time, and the grating areas of two of the fiber Bragg grating sensors are protected by capillary steel tubes to form temperature sensors. When actually used, a temperature sensor and a strain sensor are laid in parallel at a distance of 3-5 mm along the fiber direction in the center of a layer of prepreg.

[0032] The present invention also provides a method for laying optical fiber in the optical fiber monitoring device, the method comprising:

[0033] Step 1: Build a fiber monitoring network: The fiber Bragg grating sensor needs to be calibrated before use to obtain the temperature sensitivity coefficient and strain sensitivity coefficient of the fiber Bragg grating sensor; first connect the fiber Bragg grating sensor to the fiber Bragg grating demodulator. When connecting the optical fiber, first use a fiber optic cutter 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 a heat shrink tube. After the connection is completed, the fiber Bragg grating sensor is sent into the autoclave from the optical fiber interface of the autoclave, waiting to be buried in the component to be tested;

[0034] Step 2: Laying materials and pre-embedded optical fiber: First, clean the surface of the optical fiber protection mold, stick a layer of release cloth on the surface, and then lay the prepreg; pay attention to the laying direction during the laying process, and compact it manually after laying each layer of prepreg 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 in the middle of the prepreg at a distance of 3-5mm; after the prepreg is laid, lay the isolation film, release cloth and breathable felt on top in turn, 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.

[0035] The present invention also proposes a monitoring method based on the optical fiber monitoring device, the method comprising:

[0036] Step 1: calibrate the fiber Bragg grating sensor and measure the temperature sensitivity coefficient and the strain sensitivity coefficient;

[0037] Step 2, connect the fiber grating sensor to the fiber grating demodulator, and then send the end of the fiber grating sensor with the grating into the autoclave from the optical fiber interface of the autoclave; the central wavelength of the FBG sensor is 1535-1560nm, and the fiber grating demodulator has four channels, which can collect data from at least four FBG sensors at the same time. For example, four FBG sensors are used for curing monitoring at one time, and the grating areas of two of the FBG sensors are protected by capillary steel tubes to make temperature sensors. When actually used, a temperature sensor and a strain sensor are laid in parallel at a distance of 3-5mm along the fiber direction in the center of a layer of prepreg; when connecting the optical fiber, first use a fiber optic cutter to cut off the optical fiber end face, and then use a fiber optic fusion splicer to connect the optical fibers together, and fix them with a heat shrink tube at the optical fiber joint position;

[0038] Step 3: embed the fiber grating sensor into the ultra-thick foam sandwich composite material component; in order to facilitate the laying of optical fiber, one side of the foam core layer is chamfered 45°, and the foam, prepreg, film and auxiliary materials are cut as required; first clean the surface of the optical 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, compact it manually 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-embedded 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, such as Figure 2 As shown in the figure; when laying the fiber Bragg grating sensor, since the prepreg itself has a certain viscosity, the fiber Bragg grating sensor is fixed at the monitoring position, and then the prepreg is laid in the order of laying; after the laying and pre-embedding of the optical fiber are completed, the isolation film, release cloth and breathable felt are laid on the structure in sequence according to the vacuum bagging molding process;

[0039] 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 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 packaged device into the autoclave, and then connect the vacuum pipe of the autoclave to evacuate the vacuum, and check the airtightness of the device; connect the fiber grating demodulator to the computer, open the data acquisition software, and you can see the initial wavelength data of the four channels. The frequency of the fiber grating demodulator is 1000Hz, that is, it outputs one data every 1ms. When everything is ready, close the tank door and set the curing process temperature and process pressure. The schematic diagram of the optical fiber monitoring device for the curing deformation of ultra-thick foam sandwich composite components in an autoclave is shown in Figure 3 As shown, the data collected by the fiber grating sensor is processed to obtain the temperature and strain during the curing process of the foam sandwich structure.

[0040] When using the optical fiber protection mold to protect the optical fiber lead, since the FBG sensor relies on the optical fiber channel to transmit data, the optical fiber embedded in the component is not wrapped with wire. When the optical fiber angle is too large, it will cause signal interruption. At the same time, the thickness of the foam sandwich component is relatively thick and there is the influence of curing pressure. In order to prevent the optical fiber from being interrupted due to the large angle at the foam chamfer, a Figure 1 The optical fiber protection mold shown. The optical 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. The center groove of the mold faces the optical fiber of the FBG sensor to play a protective role.

[0041] The optical fiber monitoring device, optical fiber laying method and monitoring method for curing deformation of ultra-thick foam sandwich composite material components proposed in the present invention are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technicians in this field, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An optical fiber monitoring device for curing deformation of ultra-thick foam sandwich composite materials, characterized in that: The device comprises 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 optical fiber 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 chamfer of the foam, and the central groove of the mold faces the optical fiber lead of the optical fiber 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 optical fiber Bragg grating demodulator, and the optical fiber Bragg grating demodulator is then connected to a computer to collect monitoring data of the optical fiber 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 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 grating sensor is laid along the chamfer of the foam.

4. The optical fiber monitoring device according to claim 1, characterized in that: The optical 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, and the center groove of the mold faces 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 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 grating sensors are used for curing monitoring at one time. The grating areas of two of the fiber grating sensors are protected by capillary steel tubes to make 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 3-5mm.

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 monitoring network: The fiber Bragg grating sensor needs to be calibrated before use to obtain the temperature sensitivity coefficient and strain sensitivity coefficient of the fiber Bragg grating sensor; first connect the fiber Bragg grating sensor to the fiber Bragg grating demodulator. When connecting the optical fiber, first use a fiber optic cutter 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 a heat shrink tube. After the connection is completed, the fiber Bragg grating sensor is sent into the autoclave from the optical fiber interface of the autoclave, waiting 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, stick a layer of release cloth on the surface, and then lay the prepreg; pay attention to the laying direction during the laying process, and compact it manually after laying each layer of prepreg 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 in the middle of the prepreg at a distance of 3-5mm; after the prepreg is laid, lay the isolation film, release cloth and breathable felt on top in turn, 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 the strain sensitivity coefficient; Step 2: Connect the fiber grating sensor to the fiber grating demodulator, and then send the end of the fiber grating sensor with the grating into the autoclave from the fiber interface of the autoclave; the fiber grating demodulator has four channels, and four fiber grating sensors are used for curing monitoring at a time. The grating areas of two of the fiber grating sensors are protected by capillary steel tubes to form temperature sensors. When actually used, a temperature sensor and a strain sensor are laid in parallel at a distance of 3-5 mm along the fiber direction in the center of a layer of prepreg; when connecting the optical fiber, first use a fiber optic cutter to cut off the end face of the optical fiber, and then use a fiber optic fusion splicer to connect the optical fibers together, and fix them with a heat shrink tube at the optical fiber joint position; Step 3, embed the fiber grating sensor into the interior of the ultra-thick foam sandwich composite material 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 optical 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, compact it manually 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 at 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 in sequence on the structure according to the vacuum bagging 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 optical fiber Bragg grating sensor in the sealant; place a vacuum suction cup near the mouth of the autoclave on the optical fiber protection mold, and then seal it with a vacuum bag. When sealing, pleat the foam sandwich structure; send the packaged device into the autoclave, and then connect the vacuum pipe of the autoclave to evacuate the vacuum, and check the air tightness of the device; connect the optical fiber Bragg grating demodulator to the computer, open the data acquisition software, process the data collected by the optical fiber 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 frequency of the fiber grating demodulator is 1000 Hz, that is, one data is output every 1 ms.

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