Plane temperature field reconstruction method in composite material curing process

Abstract

The invention discloses a plane temperature field reconstruction method for a composite material curing process, and the method comprises the steps: obtaining the transient non-uniform temperature field information of a composite material plate curing process through numerical simulation, and analyzing the plane temperature field distribution rule in the thickness direction of the composite material plate at a temperature peak moment, coordinates of feature point locations in the plane temperature field are extracted based on the rule; actually measured temperature information of the characteristic point positions of the composite material plate in the curing process is collected; and based on the actually measured temperature information of the feature point location, completing reconstruction of the plane temperature field in the curing process of the composite material plate on the basis of a spline interpolation method. The beneficial effects of the invention are that the method achieves the reconstruction of the plane temperature field under the condition of sparse monitoring samples through the reconstruction of the measured temperature information obtained through monitoring through a spline interpolation method, and improves the reconstruction precision and efficiency of the temperature field.

Description

Technical Field

[0001] The invention relates to a temperature field reconstruction technology, and in particular to a planar temperature field reconstruction method in a composite material curing process. Background Art

[0002] Carbon fiber composite materials have the advantages of light weight, high strength, high stiffness and excellent fatigue resistance, and are widely used in the fields of AB pillars of automobiles, doors and wings in aircraft, and housings of electronic mechanical equipment. The curing process of composite materials largely determines the performance of the material after molding. The curing process mainly refers to the process in which the resin changes from liquid to solid and combines with the fiber at a specific temperature. In this process, there is a coupling effect of multiple physical fields such as thermal-chemical field and stress-strain field.

[0003] In the curing process of composite materials, it is often necessary to pay attention to the important factor of temperature. By accurately monitoring the temperature during the curing process, the molding quality of the composite materials can be effectively improved to avoid the occurrence of curing deformation or other defects. At present, the existing technology mostly uses fiber Bragg Grating (FBG) sensors to monitor the temperature during the curing process of composite materials. FBG sensors have the advantages of simple structure, anti-electromagnetic interference, good contact compatibility with the resin matrix, easy to form a distributed monitoring network and embedded detection, etc., which can effectively monitor the temperature data during the curing process of composite materials.

[0004] However, in actual applications, due to the limitations of curing devices such as autoclaves, the limited number of fiber Bragg grating interrogator channels, and the limited space for sensor layout, it is impossible to use more FBG sensors to obtain enough point information at the same time, and it is impossible to accurately reflect the plane temperature field information.

[0005] At present, the temperature monitoring of the carbon fiber composite material curing process is achieved by monitoring the information of certain points through fiber grating sensors, and there are few studies on monitoring the entire plane temperature field. At the same time, in the field of temperature field reconstruction, research is often conducted on metals or objects with simpler temperature field distribution. However, due to the existence of nonlinear internal heat sources in the curing process of composite materials, the actual situation of its non-uniform temperature field is more complicated, and the temperature field obtained by the existing technology has poor accuracy. Therefore, how to find a method that can achieve high-precision reconstruction of the plane temperature field of the carbon fiber composite material curing process is a problem that needs to be solved at this stage. Summary of the invention

[0006] The purpose of the present invention is to provide a method for reconstructing a planar temperature field during a composite material curing process in order to improve the accuracy of temperature field reconstruction, in view of the deficiencies in the prior art.

[0007] The technical solution adopted by the present invention is: a method for reconstructing a planar temperature field during a composite material curing process, the method comprising:

[0008] The transient non-uniform temperature field information of the composite material plate during the curing process is obtained through numerical simulation, the distribution law of the plane temperature field in the thickness direction of the composite material plate at the temperature peak moment is analyzed, and the coordinates of the characteristic points in the plane temperature field are extracted based on this law;

[0009] Collect the measured temperature information of the characteristic points of the composite material plate during the curing process;

[0010] Based on the measured temperature information of the characteristic points, the plane temperature field of the composite material plate during the curing process is reconstructed using the spline interpolation method.

[0011] According to the above scheme, the plane temperature field in the thickness direction of the composite material plate at the temperature peak moment refers to the plane temperature field of the composite material plate along the thickness direction when the temperature of a point inside the composite material plate reaches the maximum value during the external heating process.

[0012] According to the above scheme, the distribution law of the plane temperature field is as follows: the plane temperature field is evenly divided into multiple temperature intervals along the thickness direction, and there is a temperature change starting point on each temperature interval dividing line parallel to the X-axis. The temperature values ​​of each point on the left dividing line of the temperature change starting point are the same, and are the same as the temperature value corresponding to the leftmost point of the dividing line; the temperature value changes of each point on the right dividing line of the temperature change starting point follow the same decreasing change law.

[0013] According to the above scheme, a fiber Bragg grating monitoring system is used to obtain the measured temperature information of characteristic points of the composite material plate during the curing process.

[0014] According to the above scheme, the fiber grating monitoring system includes a composite material plate, an autoclave, a fiber grating sensor, a coupler, a spectrum analyzer and a broadband light source;

[0015] The composite material plate is placed in an autoclave, and a fiber grating sensor is installed on the composite material plate, wherein the grating area of ​​the fiber grating sensor corresponds to the characteristic point of the composite material plate;

[0016] The fiber grating sensor passes through the reserved hole of the autoclave and is connected to a coupler outside the autoclave. The coupler is connected to a spectrum analyzer and a broadband light source respectively.

[0017] According to the above scheme, based on the measured temperature information of the characteristic points, the method for reconstructing the plane temperature field of the composite material curing process based on the spline interpolation method is as follows:

[0018] Step 1), input the measured temperature information of the characteristic points in the reconstructed plane temperature field;

[0019] Step 2), determine the starting point of the temperature change of each dividing line;

[0020] Step 3), based on the measured temperature information of the characteristic points, respectively calculate the temperature values ​​of the leftmost point and the rightmost point of each dividing line in the plane temperature field;

[0021] Step 4), obtaining the temperature change curve on the left side of the starting point of the temperature change of each dividing line;

[0022] Step 5), obtaining the temperature change curve on the right side of the starting point of the temperature change of each dividing line;

[0023] Step 6) Draw a thermal map of the composite material plate based on the temperature change curves of each boundary line, that is, complete the reconstruction of the plane temperature field during the curing process of the composite material.

[0024] According to the above scheme, the specific method of step 1) is: take the lower left corner of the plane temperature field in the thickness direction of the composite material plate at the temperature peak moment obtained by numerical simulation as the origin, the long side as the X-axis direction, and the short side as the Y-axis direction, discretize the plane temperature field into several points, input the coordinates of the feature points and the measured temperature information corresponding to the feature points obtained in step 2.

[0025] According to the above scheme, the method for determining the starting point of the temperature change of each dividing line is as follows: through numerical simulation, the interval of the X-coordinate value of the starting point of the temperature change of each dividing line of the plane temperature field is obtained, which is used as the coordinate value range of the temperature change point set during reconstruction; and the temperature change starting point is generated by a uniformly distributed random number function in the matlab software.

[0026] According to the above scheme, the method of step 3) is: select the starting point of the temperature change on a certain dividing line as the characteristic point, the measured temperature value corresponding to the characteristic point is also the temperature value corresponding to the leftmost point on the dividing line, after determining the temperature values ​​of the leftmost points of several dividing lines, use the spline interpolation method to solve the temperature values ​​of the leftmost points on other dividing lines; select the point with the minimum temperature on a certain dividing line as the characteristic point, the characteristic point is also the rightmost point on the dividing line, after determining the temperature values ​​of the rightmost points of several dividing lines, use the spline interpolation method to solve the temperature values ​​of the rightmost points on other dividing lines.

[0027] According to the above scheme, the method for obtaining the temperature change curve on the left side of the starting point of the temperature change of each dividing line is: the temperature value corresponding to the leftmost point on each dividing line of the plane temperature field is extended in the positive direction of the X-axis to the starting point of the temperature change, that is, the temperature values ​​of each point on the left side of the starting point of the temperature change on the same dividing line are the same, and are consistent with the temperature value corresponding to the point x=0 on the dividing line, and then the temperature change curve on the left side of the starting point of the temperature change of each dividing line is drawn;

[0028] The method for obtaining the temperature change curve on the right side of the starting point of the temperature change of each dividing line is: based on the temperature values ​​of the starting point of the temperature change of each dividing line and the rightmost point, the temperature values ​​of the points on the right side of the starting point of the temperature change on each dividing line are calculated by the spline interpolation method, and then the temperature change curve on the right side of the starting point of the temperature change of each dividing line is drawn.

[0029] The beneficial effects of the present invention are as follows: the present invention analyzes the temperature variation law during the curing process of the composite material through numerical simulation to obtain the coordinates of the characteristic points; and detects the measured temperature values ​​of the characteristic points during the curing process of the composite material, and reconstructs the measured temperature information obtained through monitoring through the spline interpolation method, thereby realizing the reconstruction of the plane temperature field under the condition of sparse monitoring samples, while improving the temperature field reconstruction accuracy and efficiency, while reducing the damage to the composite material, and solving the problem that the current monitoring samples for temperature information are too few to accurately reflect the plane temperature field information. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The figure is a flow chart of a specific embodiment of the present invention.

[0031] Figure 2 Schematic diagram of the structure of the fiber Bragg grating monitoring system.

[0032] Figure 3 Schematic diagram of the composite material plate and plane temperature field position in this embodiment.

[0033] Figure 4 Schematic diagram of characteristic points in the plane temperature field in this embodiment.

[0034] Figure 5 This is a plane temperature field distribution cloud diagram along the thickness direction at the temperature peak moment during the curing process of the composite material obtained by numerical simulation in this embodiment.

[0035] Figure 6 The plane temperature field distribution cloud map is reconstructed and obtained for this embodiment.

[0036] Figure 7 It is a difference cloud diagram between the plane temperature field obtained by numerical simulation and the plane temperature field obtained by reconstruction in this embodiment.

[0037] Figure 3 In: 1. Broadband light source; 2. Coupler; 3. Fiber Bragg grating sensor; 4. Fiber Bragg grating sensor grating area; 5. Composite material; 6. Autoclave; 7. Reserved hole; 8. Spectrum analyzer. DETAILED DESCRIPTION

[0038] In order to better understand the present invention, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0039] like Figure 1 A method for reconstructing a plane temperature field during a composite material curing process is shown, specifically a method for reconstructing a plane temperature field during a carbon fiber composite material curing process, the method comprising the following steps:

[0040] Step 1: provide a composite material plate, obtain transient non-uniform temperature field information of the composite material plate during the curing process through numerical simulation, analyze the distribution law of the plane temperature field in the thickness direction of the composite material plate at the temperature peak moment, and extract the coordinates of characteristic points in the plane temperature field (that is, the plane temperature field in the thickness direction of the composite material plate at the temperature peak moment) based on the law;

[0041] Step 2: Establish a fiber Bragg grating monitoring system for measuring temperature distribution, arrange the fiber Bragg grating sensors of the fiber Bragg grating monitoring system at the characteristic points corresponding to the composite material plate, and collect the measured temperature information of the characteristic points of the composite material plate during the curing process;

[0042] Step 3: Based on the temperature field distribution law in the thickness direction at the temperature peak moment during the curing process of the composite material plate and the measured temperature information of the characteristic points, the plane temperature field of the composite material plate curing process is reconstructed through Matlab software based on the spline interpolation method.

[0043] The composite material plate is put into the autoclave for curing. Due to the symmetry of the plate, the present invention only takes 1 / 2 of the length of the plate as the research object, and reconstructs the temperature field of the center plane of the width of the 1 / 2 plate, such as Figure 3 As shown. The composite material plates mentioned in the temperature field reconstruction process of the present invention all refer to 1 / 2 plate models. Combined with the heat-conduction model and the curing kinetics model, a numerical simulation is performed on the curing process of the composite material plate to obtain a plane temperature field cloud map in the thickness direction of the composite material plate at the temperature peak moment. The plane temperature field in the thickness direction of the composite material plate at the temperature peak moment is specifically the plane temperature field of the composite material plate along the thickness direction when the temperature of a point inside the composite material plate reaches the maximum value during the external heating process. The X direction of the plane temperature field corresponds to the length direction of the composite material plate, and the Y direction of the plane temperature field corresponds to the thickness direction of the composite material plate.

[0044] The plane temperature field cloud map is analyzed to obtain the plane temperature field distribution law: the plane temperature field is evenly divided into multiple temperature intervals along the thickness direction, and there is a special point on each temperature interval dividing line parallel to the X-axis, that is, the starting point of the temperature change. The temperature values ​​of each point on the left dividing line of the temperature change starting point are the same, and are the same as the temperature value corresponding to the point x=0 on the dividing line (that is, the leftmost point of the dividing line); the temperature value changes of each point on the right dividing line of the temperature change starting point follow the same decreasing change law.

[0045] In step 1 of the present invention, the point corresponding to the maximum temperature on the dividing line is the starting point of the temperature change, and the rightmost point on the dividing line is the point corresponding to the minimum temperature on the straight line. The number of characteristic points is not less than 6, some characteristic points select the point corresponding to the maximum temperature on the dividing line (that is, the starting point of the temperature change is selected as the characteristic point), and some characteristic points select the point corresponding to the minimum temperature on the dividing line, and determine the coordinates of each characteristic point.

[0046] In step 2 of the present invention, the fiber Bragg grating monitoring system includes a composite material plate, an autoclave, a fiber Bragg grating sensor, a coupler, a spectrum analyzer and a broadband light source;

[0047] The composite material plate is placed in an autoclave, and a fiber grating sensor is installed on the composite material plate, wherein the grating area of ​​the fiber grating sensor corresponds to the characteristic point of the composite material plate;

[0048] The fiber grating sensor passes through the reserved hole of the autoclave and is connected to a coupler outside the autoclave. The coupler is connected to a spectrum analyzer and a broadband light source respectively.

[0049] In the present invention, the curing process of the composite material plate is carried out in an autoclave, and the fiber grating sensor enters the autoclave through a reserved hole on the autoclave and is buried in the characteristic point of the composite material plate, and the reserved hole is sealed to prevent air leakage; the other end of the fiber grating sensor is directly connected to the coupler, and the coupler is also directly connected to a broadband light source at the same time to realize the sensing, measurement and regulation of optical signals; the coupler is also directly connected to a spectrum analyzer at the same time to read the temperature data of the composite material plate in real time during the curing process. The system is used to obtain the temperature data of the characteristic point of the composite material plate at the temperature peak moment as the initial data for the reconstruction of the plane temperature field.

[0050] In step 3 of the present invention, the spline interpolation method is a cubic spline interpolation method. The planar temperature field reconstruction method of the composite material curing process is specifically as follows:

[0051] 1) Input the measured temperature information of the feature points in the reconstructed plane temperature field: take the lower left corner of the plane temperature field in the thickness direction of the composite material plate at the temperature peak moment obtained by numerical simulation in step 1 as the origin, the long side as the X-axis direction (corresponding to the length direction of the composite material plate), and the short side as the Y-axis direction (corresponding to the thickness direction of the composite material plate), discretize the plane temperature field into several points, input the coordinates of the feature points and the measured temperature information corresponding to the feature points obtained in step 2.

[0052] 2) Determine the starting point of the temperature change of each dividing line: obtain the interval of the X-coordinate value of the starting point of the temperature change of each dividing line of the plane temperature field through numerical simulation, as the range of the coordinate value of the temperature change point set during reconstruction; use the uniform distribution random number function to generate the starting point of the temperature change in the matlab software. Specifically, the first step is to set the range and standard deviation of the mean value to ensure that 99.7% of the temperature starting coordinate point data falls within the set range; the second step is to generate random values ​​that match the number of dividing lines, calculate the mean of the current random value, and translate and scale the mean to make it close to the target mean; the third step is to check each random value, if it is greater than the upper limit of the value range, it is corrected to the upper limit, if it is less than the lower limit of the value range, it is corrected to the lower limit; the fourth step is to use the generated random coordinate value as the starting point of the temperature change used in the subsequent steps.

[0053] 3) Based on the measured temperature information of the characteristic points, the temperature values ​​of the leftmost point and the rightmost point of each dividing line in the plane temperature field are calculated by the spline interpolation method (specifically, the cubic spline interpolation method): the starting point of the temperature change on a certain dividing line is selected as the characteristic point, and the measured temperature value corresponding to the characteristic point is also the temperature value corresponding to the leftmost point on the dividing line. After determining the temperature values ​​of the leftmost points of several dividing lines, the spline interpolation method is used to solve the temperature values ​​of the leftmost points on other dividing lines; the point with the minimum temperature on a certain dividing line is selected as the characteristic point, and the characteristic point is also the rightmost point on the dividing line. After determining the temperature values ​​of the rightmost points of several dividing lines, the spline interpolation method is used to solve the temperature values ​​of the rightmost points on other dividing lines.

[0054] 4) Obtain the temperature change curve on the left side of the starting point of the temperature change of each dividing line: extend the temperature value corresponding to the leftmost point (i.e., the point on x=0) on each dividing line of the plane temperature field in the positive direction of the X-axis to the starting point of the temperature change (i.e., the starting point of the temperature change generated by step 2), that is, the temperature values ​​of all points on the left side of the starting point of the temperature change on the same dividing line are the same, and are consistent with the temperature value corresponding to the point on the dividing line where x=0 (i.e., the leftmost point), and then draw the temperature change curve on the left side of the starting point of the temperature change of each dividing line.

[0055] 5) Obtain the temperature change curve on the right side of the starting point of the temperature change of each dividing line: Based on the temperature values ​​of the starting point of the temperature change of each dividing line and the rightmost point, the temperature values ​​of the points on the right side of the starting point of the temperature change on each dividing line are calculated by the spline interpolation method, and then the temperature change curve on the right side of the starting point of the temperature change of each dividing line is drawn.

[0056] 6) Based on the temperature change curves of each dividing line, a thermal map of the composite material plate is drawn, that is, the plane temperature field reconstruction during the curing process of the composite material is completed, which is essentially the reconstruction of the plane non-uniform temperature field.

[0057] The composite material board in the present invention may specifically be a carbon fiber composite material board, and the plane temperature field at the temperature peak moment during the curing process of the carbon fiber composite material board is reconstructed.

[0058] Example

[0059] The object of this embodiment is a carbon fiber composite material plate of 200 mm (length) × 200 mm (width) × 5.4 mm (thickness). Due to the symmetry of the carbon fiber composite material plate, this embodiment takes the 1 / 2 model of the carbon fiber composite material plate in the length direction as the research object, and reconstructs the temperature field of the width center plane of the model, such as Figure 3 shown.

[0060] The planar temperature field reconstruction method of the carbon fiber composite material plate curing process is as follows:

[0061] Step 1: obtain the transient non-uniform temperature field information of the carbon fiber composite material plate during the curing process through numerical simulation, analyze the planar temperature field distribution law in the thickness direction of the carbon fiber composite material plate at the temperature peak moment, and extract the coordinates of the characteristic points in the temperature field based on this law.

[0062] The plane temperature field distribution diagram is obtained through numerical simulation. The lower left corner of the plane where the temperature field is located is the origin, the X-axis corresponds to the length direction of the carbon fiber composite material plate, and the Y-axis corresponds to the thickness direction of the carbon fiber composite material plate. The plane temperature field is divided into multiple temperature intervals, corresponding to multiple dividing lines, each dividing line has a temperature change starting point, the temperature values ​​of each point on the dividing line to the left of the temperature change starting point are the same, and the temperature values ​​on the dividing line to the right of the temperature change starting point are all decreasing.

[0063] In this embodiment, the plane temperature field of the carbon fiber composite material plate corresponds to its cross section, and the plane temperature field is divided into a temperature interval every 0.1 mm along the thickness direction, with a total of 55 temperature interval dividing lines. Select the 6 characteristic points A to F, the specific positions are as follows Figure 4 As shown, the characteristic points A and F are located on the frontmost dividing line of the carbon fiber composite material plate, the characteristic points E and D are located on the rearmost dividing line of the carbon fiber composite material plate, and the characteristic points A, E, and F are the starting points of the temperature changes of the three dividing lines, and the characteristic points B, C, and D are located at the points with the smallest temperature values ​​on the dividing lines, that is, the rightmost points of the dividing lines.

[0064] Step 2: Establish a fiber Bragg grating monitoring system for measuring temperature distribution, install the fiber Bragg grating sensors of the fiber Bragg grating monitoring system on the six characteristic points corresponding to the carbon fiber composite material plate, and collect the measured temperature information of the characteristic points.

[0065] In this embodiment, the number of the fiber grating sensors can be arranged according to actual needs.

[0066] Step 3: Based on the temperature field distribution law in the thickness direction at the peak temperature moment during the curing process of the carbon fiber composite material plate and the measured temperature values ​​of the characteristic points, the planar non-uniform temperature field of the carbon fiber composite material plate during the curing process is reconstructed through Matlab software based on the spline interpolation method.

[0067] The specific reconstruction method includes the following steps:

[0068] 1) Input the measured temperature information corresponding to the characteristic point in the plane temperature field. In this embodiment, the coordinates and measured temperature values ​​corresponding to the six characteristic points are: (80, 0)-453.84K (the horizontal coordinate of the characteristic point is 80, the vertical coordinate is 0, and the temperature at the characteristic point is 453.84K), (100, 0)-453.16K, (66, 4.2)-455.91K, (100, 4.2)-455.28, (74, 5.4)-455.71K, (100, 5.4)-455.14K. Figure 4 The approximate locations of the six feature points are shown in Figure 2.

[0069] 2) Obtain the starting point of the temperature change of each boundary line in the reconstructed plane temperature field. The specific method is: through numerical simulation, the X coordinate value of the starting point of the temperature change of each boundary line of the plane temperature field in this embodiment is in the interval [70,80], so this interval is taken as the coordinate value range of the temperature change point set during reconstruction. After obtaining the value range of the temperature starting coordinate point, using matlab software, the first step is to set the range of the mean value to 10 and the standard deviation to 10 / 6 (according to the 3σ principle of normal distribution) to ensure that 99.7% of the temperature starting coordinate point data falls within the set range; the second step is to generate 55 random values, calculate the mean of the current random value, and translate and scale the mean to make it close to the target mean value of 75 (which can be set according to actual conditions); the third step is to check each random value, if it is greater than the upper limit value 80, it is corrected to the upper limit value 80, if it is less than the lower limit value 70, it is corrected to the lower limit value 70; the fourth step is to use the generated random coordinate values ​​uniformly distributed between 70 and 80 as the starting point of the temperature change used in the subsequent steps.

[0070] 3) Based on the temperature information of the characteristic points, the temperature values ​​of the leftmost and rightmost points of each dividing line in the plane temperature field are calculated by the spline interpolation method. As shown in Figure 4, the starting point of the temperature change on the dividing line in the original numerical simulation temperature field is selected as the characteristic point, and the measured temperature value corresponding to the characteristic point is also the temperature value corresponding to the leftmost point on the dividing line; after determining the temperature value of the leftmost point of the three dividing lines, the spline interpolation method is used to solve the temperature value of the leftmost point on other dividing lines. When the point with the minimum temperature on the dividing line is selected as the characteristic point, the measured temperature of the characteristic point is also the temperature of the rightmost point on the dividing line. After determining the temperature value of the rightmost point of the three dividing lines, the spline interpolation method is used to solve the temperature value of the rightmost point on other dividing lines.

[0071] 4) Extend the temperature value corresponding to the leftmost point on each dividing line of the plane temperature field (i.e., the point on x=0) in the positive direction of the X-axis to step 2) to obtain the starting point of the temperature change, and draw the temperature change curve on the left side of the starting point of the temperature change of each dividing line.

[0072] 5) Obtain the temperature change curve on the right side of the starting point of the temperature change of each dividing line: Based on the temperature value of the starting point of the temperature change of each dividing line (a randomly generated point of 2)) and the temperature value of the rightmost point, the temperature value of the point on the right side of the starting point of the temperature change on each dividing line is calculated by the spline interpolation method, and then the temperature change curve on the right side of the starting point of the temperature change of each dividing line is drawn.

[0073] 6) Draw a heat map based on the temperature change curves of each dividing line, that is, complete the reconstruction of the planar non-uniform temperature field of the carbon fiber composite material curing process.

[0074] In this embodiment, the spline interpolation method and the method for obtaining the starting point of the temperature change of each boundary line in the reconstructed plane temperature field are both mature methods and can be implemented on Matlab software. Figure 5 and Figure 6 , it can be seen that this embodiment has a very high reconstruction accuracy.

[0075] like Figure 7 As shown in the figure, the temperature value of each point obtained by numerical simulation is taken as the standard value, and the temperature value of each point reconstructed by cubic spline interpolation method is processed with the standard value. Figure 7 What is displayed is the difference cloud map of all points in the plane, where 0.1, 0.2, and 0.3 shown on the temperature scale refer to the size of the temperature difference, in units of K. The difference cloud map can also reflect that the error of the reconstructed result is small. Table 1 shows the temperature values ​​obtained by numerical simulation and the temperature values ​​obtained by reconstruction at several points in this embodiment. Through comparative analysis, it can be seen that the reconstruction method of the present invention has a small error and high precision.

[0076] Table 1 Temperature values ​​obtained by numerical simulation and temperature values ​​obtained by reconstruction

[0077]

[0078] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0079] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein with equivalents. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for reconstructing a planar temperature field during a composite material curing process, characterized in that: The method includes: The transient non-uniform temperature field information of the composite material plate during the curing process is obtained through numerical simulation, the distribution law of the plane temperature field in the thickness direction of the composite material plate at the temperature peak moment is analyzed, and the coordinates of the characteristic points in the plane temperature field are extracted based on this law; Collect the measured temperature information of the characteristic points of the composite material plate during the curing process; Based on the measured temperature information of the characteristic points, the plane temperature field of the composite material plate during the curing process is reconstructed using the spline interpolation method.

2. The planar temperature field reconstruction method according to claim 1, characterized in that: The plane temperature field in the thickness direction of the composite material plate at the temperature peak moment refers to the plane temperature field of the composite material plate along the thickness direction when the temperature of a point inside the composite material plate reaches a maximum value during the external heating process.

3. The planar temperature field reconstruction method according to claim 1, characterized in that: The distribution law of the plane temperature field is as follows: the plane temperature field is evenly divided into multiple temperature intervals along the thickness direction, and there is a temperature change starting point on each temperature interval dividing line parallel to the X-axis. The temperature values ​​of each point on the left dividing line of the temperature change starting point are the same, and are the same as the temperature value corresponding to the leftmost point of the dividing line; the temperature value changes of each point on the right dividing line of the temperature change starting point follow the same decreasing change law.

4. The planar temperature field reconstruction method according to claim 3, characterized in that: The fiber Bragg grating monitoring system is used to obtain the measured temperature information of the characteristic points of the composite material plate during the curing process.

5. The planar temperature field reconstruction method according to claim 4, characterized in that: The FBG monitoring system includes a composite material plate, an autoclave, a FBG sensor, a coupler, a spectrum analyzer, and a broadband light source; The composite material plate is placed in an autoclave, and a fiber grating sensor is installed on the composite material plate, wherein the grating area of ​​the fiber grating sensor corresponds to the characteristic point of the composite material plate; The fiber grating sensor passes through the reserved hole of the autoclave and is connected to a coupler outside the autoclave. The coupler is connected to a spectrum analyzer and a broadband light source respectively.

6. The planar temperature field reconstruction method according to claim 4, characterized in that: Based on the measured temperature information of the characteristic points, the method for reconstructing the plane temperature field of the composite material curing process based on the spline interpolation method is as follows: Step 1), input the measured temperature information of the characteristic points in the reconstructed plane temperature field; Step 2), determine the starting point of the temperature change of each dividing line; Step 3), based on the measured temperature information of the characteristic points, respectively calculate the temperature values ​​of the leftmost point and the rightmost point of each dividing line in the plane temperature field; Step 4), obtaining the temperature change curve on the left side of the starting point of the temperature change of each dividing line; Step 5), obtaining the temperature change curve on the right side of the starting point of the temperature change of each dividing line; Step 6) Draw a thermal map of the composite material plate based on the temperature change curves of each boundary line, that is, complete the reconstruction of the plane temperature field during the curing process of the composite material.

7. The planar temperature field reconstruction method according to claim 6, characterized in that: The specific method of step 1) is: take the lower left corner of the plane temperature field in the thickness direction of the composite material plate at the temperature peak moment obtained by numerical simulation as the origin, the long side as the X-axis direction, and the short side as the Y-axis direction, discretize the plane temperature field into several points, input the coordinates of the feature point and the measured temperature information corresponding to the feature point obtained in step 2.

8. The planar temperature field reconstruction method according to claim 6, characterized in that: The method for determining the starting point of the temperature change of each dividing line is as follows: through numerical simulation, the interval of the X-coordinate value of the starting point of the temperature change of each dividing line of the plane temperature field is obtained, which is used as the coordinate value range of the temperature change point set during reconstruction; the starting point of the temperature change is generated by a uniformly distributed random number function in the matlab software.

9. The planar temperature field reconstruction method according to claim 4, characterized in that: The method of step 3) is: select the starting point of the temperature change on a certain dividing line as the characteristic point, the measured temperature value corresponding to the characteristic point is also the temperature value corresponding to the leftmost point on the dividing line, after determining the temperature values ​​of the leftmost points of several dividing lines, use the spline interpolation method to solve the temperature values ​​of the leftmost points on other dividing lines; The point with the minimum temperature on a certain dividing line is selected as the characteristic point, which is also the rightmost point on the dividing line. After determining the temperature values ​​of the rightmost points of several dividing lines, the spline interpolation method is used to solve the temperature values ​​of the rightmost points on other dividing lines.

10. The planar temperature field reconstruction method according to claim 4, characterized in that: The method for obtaining the temperature change curve on the left side of the starting point of the temperature change of each dividing line is as follows: the temperature value corresponding to the leftmost point on each dividing line of the plane temperature field is extended in the positive direction of the X-axis to the starting point of the temperature change, that is, the temperature values ​​of each point on the left side of the starting point of the temperature change on the same dividing line are the same, and are consistent with the temperature value corresponding to the point x=0 on the dividing line, and then the temperature change curve on the left side of the starting point of the temperature change of each dividing line is drawn; The method for obtaining the temperature change curve on the right side of the starting point of the temperature change of each dividing line is: based on the temperature values ​​of the starting point of the temperature change of each dividing line and the rightmost point, the temperature values ​​of the points on the right side of the starting point of the temperature change on each dividing line are calculated by the spline interpolation method, and then the temperature change curve on the right side of the starting point of the temperature change of each dividing line is drawn.

Images