Defect monitoring method and system in mold-free mirror image fiber placement process

Abstract

The invention belongs to the technical field of material processing, and relates to a defect monitoring method and system in a mold-free mirror image fiber placement process. According to the system, the left current-conducting plate and the right current-conducting plate are in contact with the two sides of the ribbon to form a capacitance detection loop, and the laying state of the ribbon is reflected by monitoring the change of a capacitance value. The method comprises the following steps: controlling a left conductive plate and a right conductive plate to continuously contact with a ribbon in a mold-free mirror image fiber placement process to obtain capacitance data, processing to obtain a capacitance curve, and analyzing to obtain a defect detection result. The die-free mirror image fiber placement defect monitoring system has the advantages of low cost, high efficiency, high compatibility and high detection precision, and provides powerful support for technical innovation in the field of composite material processing.

Description

Technical Field

[0001] The invention belongs to the technical field of material processing, and relates to a defect monitoring method and system in a patternless mirror-image wire laying process. Background Art

[0002] Wire laying technology plays a vital role in the precision process of composite material manufacturing, especially in the manufacture of complex structural parts such as aircraft wings. However, the traditional wire laying process is highly dependent on customized metal molds, which need to accurately match the unique surface contours of each component. Not only does it take a long time to make and consume a lot of materials, but each component also requires a separate mold design due to its uniqueness, which seriously restricts the flexible response and overall efficiency of the production process. In addition, the design and manufacturing process of the mold is highly technology-intensive, with high barriers and costs, further increasing the production challenges.

[0003] In order to break through this bottleneck, the field of material processing is exploring an innovative idea, which is to integrate the concept of mirror processing into the wire laying technology. Specifically, the idea is to deploy two sets of mirror-configured wire laying systems, which are symmetrically deployed on both sides of the workpiece to be processed, working together like reflections in a mirror. Under this layout, the two wire laying equipment can rely on each other and jointly perform precise and symmetrical wire laying tasks without the support of traditional molds, realizing the so-called "moldless mirror wire laying" technology innovation. If this idea can be realized, it is expected to completely subvert the traditional wire laying process's dependence on molds and usher in a new era of composite material processing.

[0004] However, the process of patternless mirror fiber placement requires dual heat sources and double-sided pressure application in the patternless state. The multi-source thermal and mechanical effects can easily lead to complex internal defects, such as voids and delamination inside the composite material. These internal defects not only affect the mechanical properties of the product, but may also cause early failure of the product during use. Therefore, if the above idea is to be realized, it is particularly important to realize real-time monitoring and detection of internal defects in the patternless mirror fiber placement process.

[0005] At present, the detection methods of internal defects mainly include active infrared thermal imaging, laser ultrasonic detection and current detection.

[0006] Active infrared thermal imaging uses lasers to actively heat the material and uses an infrared thermal imager to collect surface temperature images to monitor internal defects. Although this method can effectively detect interlayer defects, the detection cost is high, and each printed layer requires laser heating, which affects the detection efficiency and printing quality. Laser ultrasonic testing has high detection accuracy, but the equipment is complex and expensive, and it is difficult to integrate with the moldless mirror wire placement end mechanism, so it is not suitable for real-time online detection.

[0007] Current detection, such as patent CN117368281B discloses a real-time monitoring method and equipment for defects in in-situ additive manufacturing of carbon fiber composite materials. It uses current to detect internal defects, adds a conductive plate in front of the roller, lays an equipotential layer under the printed workpiece, applies a certain voltage between the conductive plate and the equipotential layer, and the conductive plate, the outer layer of the roller, the composite material, and the equipotential layer form a conductive circuit. Defects are determined by detecting the current of the printed composite material. However, this patent requires laying an equipotential layer at the bottom of the composite material, which not only limits the freedom of wire laying, but also increases the complexity of the system. In addition, the current detection is easily affected when the capacitance of the composite material is high or the resistance is low.

[0008] In summary, the existing internal defect detection methods are difficult to apply to the concept of patternless mirror wire laying. Summary of the invention

[0009] The purpose of the present invention is to solve the problems existing in the prior art and to provide a method and system for monitoring defects in a patternless mirror-image wire laying process.

[0010] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0011] A defect monitoring system in a patternless mirror-image wire laying process, wherein the patternless mirror-image wire laying equipment comprises a symmetrical left part and a right part;

[0012] The right part includes a main body plate and a pressure component, the pressure component includes a pressure roller, a support device, and a cylinder a. The central axis of the pressure roller is parallel to the front-back direction. The support device is located on the right side of the pressure roller and is connected to it. The cylinder a is fixed on the main body plate and is used to push the pressure roller to the left, and cooperate with the pressure roller on the opposite side to squeeze and generate compaction pressure.

[0013] The defect monitoring system includes a left conductive plate, a left tension spring, a right conductive plate, a right tension spring and a capacitance detection device;

[0014] The left end of the left conductive plate is directly connected to the support device of the left part, the middle part is connected to the support device of the left part through the left tension spring, and the right end of the left conductive plate is located in front of the pressure roller of the left part along the wire running direction;

[0015] The right end of the right conductive plate is directly connected to the supporting device of the right part, the middle part is connected to the supporting device of the right part through the right tension spring, and the left end of the right conductive plate is located in front of the pressure roller of the right part along the wire running direction;

[0016] The left conductive plate and the right conductive plate are respectively connected to the positive electrode interface and the negative electrode interface of the capacitance detection device, and the capacitance detection device is used to output capacitance data.

[0017] As the preferred technical solution:

[0018] In the defect monitoring system for the patternless mirror-image wire laying process as described above, the left conductive plate and the right conductive plate are symmetrically arranged, and the left tension spring and the right tension spring are symmetrically arranged.

[0019] As described above, in the defect monitoring system for the patternless mirror-image wire laying process, the defect monitoring system also includes a host computer, and the host computer is connected to the USB communication interface of the capacitance detection device via a network cable.

[0020] A defect monitoring system for a patternless mirror-image wire laying process as described above, wherein the right part further comprises a shearing component, a re-feeding component, a tension component, a heat source component, a connecting piece, and a wire laying end motion mechanism, wherein the pressure component, the shearing component, the re-feeding component, and the tension component are arranged in sequence from front to back along the wire running direction;

[0021] The shearing component includes a cylinder b and a blade. The cylinder b is used to drive the blade to shear the ribbon. The cylinder b is fixed on the main plate.

[0022] The heavy-feeding component includes a driving wheel, a driven wheel, a motor and a cylinder c. The driving wheel and the driven wheel are arranged vertically and parallel to the left and right directions. The motor is used to drive the driving wheel to rotate, and the cylinder c is used to press the driven wheel onto the driving wheel. The motor and the cylinder c are fixed on the main body plate. Before the silk ribbon is installed and the silk laying begins, the cylinder c is not started, and the driving wheel and the driven wheel are separated. When the silk laying begins, the silk ribbon is installed in the channel and passes between the driving wheel and the driven wheel. The cylinder c is started, and the driven wheel presses the silk ribbon onto the driving wheel to achieve the pressing of the silk ribbon. The motor drives the driving wheel to rotate during the silk laying process, driving the driven wheel to squeeze out the silk ribbon together.

[0023] The tension component includes a material tray and a brake. The material tray is used to wind the ribbon. During the wire laying process, the material roll is forced to rotate under the drive of the re-feeding component to realize the feeding of the ribbon. The brake is used to provide torque for the material tray to maintain a stable tension force for wire feeding to prevent the ribbon from being unstablely fed or even falling off due to the high-speed rotation of the material roll. The material tray and the brake are both fixed on the main plate.

[0024] The heat source component comprises a laser heater, which is used to heat the ribbon and is fixed on the main plate;

[0025] The connecting piece is fixed on the main plate and connected to the end of the wire placement end movement mechanism.

[0026] The present invention also provides a method for monitoring defects in a patternless mirror image fiber placement process, using a system for monitoring defects in a patternless mirror image fiber placement process as described in any one of the above items;

[0027] Mirror-image laying without a mold means laying two ribbons in a mirror-symmetrical manner without using a mold, and repeating the laying process multiple times;

[0028] Defect monitoring means controlling the left conductive plate and the right conductive plate to keep in contact with the two opposite sides of the two wires in each laying process, obtaining the capacitance data of each laying process, processing the capacitance data to obtain the capacitance curve, and then analyzing the capacitance curve to obtain the defect detection result;

[0029] The vertical axis of the capacitance curve is capacitance, and each fiber laying process corresponds to one capacitance curve;

[0030] When the defect monitoring system includes a host computer, the host computer executes the operation of "after processing the capacitance data to obtain the capacitance curve, analyzing the capacitance curve to obtain the defect detection result"; when the defect monitoring system does not include a host computer, a person is required to execute the operation of "after processing the capacitance data to obtain the capacitance curve, analyzing the capacitance curve to obtain the defect detection result".

[0031] As the preferred technical solution:

[0032] In the defect monitoring method during the patternless mirror-image wire laying process as described above, the horizontal coordinate of the capacitance curve is the wire laying time or the product of the wire laying time and the wire laying speed, and each wire laying process starts from 0.

[0033] As described above, in a defect monitoring method for a patternless mirror-image wire laying process, for two adjacent wire laying processes, the two wire ribbons laid in the latter wire laying process are located on two sides of the two wire ribbons laid in the former wire laying process that are away from each other.

[0034] In the defect monitoring method in the process of patternless mirror-image laying as described above, when the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is less than or equal to 10nF, the defect detection result is: the whole of the silk ribbon laid by this and all previous laying processes has no obvious defects;

[0035] When the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is greater than 10nF and less than or equal to 30nF, and the maximum capacitance is greater than 20nF and less than or equal to 40nF, the defect detection result is: the whole composed of the silk ribbons laid in this and all previous laying processes has relatively serious defects;

[0036] When the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is greater than 30nF and the maximum capacitance is greater than 40nF, the defect detection result is: the whole composed of the silk ribbons laid in this and all previous laying processes has very serious defects;

[0037] No obvious defects, that is, the total area of ​​voids and delaminations on the cross section of the ribbons laid in this and all previous laying processes is less than 3%, that is, the interior is tight and there is no obvious void or delamination;

[0038] The more serious defect is that the total area of ​​voids and delaminations on the cross section of the ribbons laid in this and all previous laying processes is greater than or equal to 3% and less than 8%, that is, there are a small amount of voids and delaminations inside;

[0039] A very serious defect is that the total area of ​​voids and stratification on the overall cross-section formed by the silk ribbons laid in this and all previous silk laying processes accounts for more than or equal to 8%, that is, there are a large number of voids and stratification inside.

[0040] Beneficial effects:

[0041] (1) The present invention cooperates with the left conductive plate, the right conductive plate and the capacitance detection device to continuously contact the ribbon during the patternless mirror-shaped fiber laying process to obtain capacitance data, and then analyzes and obtains defect detection results. It can monitor the internal defects in the patternless mirror-shaped fiber laying process in real time and accurately, including complex defects such as gaps and delaminations inside the composite material, providing a strong basis for timely adjusting process parameters and ensuring product quality.

[0042] (2) Compared with existing methods such as active infrared thermal imaging and laser ultrasonic detection, the capacitance detection method of the present invention has lower cost and is easy to integrate with the patternless mirror fiber placement equipment; at the same time, the method does not rely on the equipotential layer at the bottom of the composite material, which improves the freedom of fiber placement. It can still maintain a high detection accuracy when the composite material has a high capacitance or a low resistance, and is not easily affected by environmental factors, and has high stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the structure of the moldless mirror-image wire laying equipment;

[0044] Figure 2 A schematic diagram of the process of performing patternless mirror-image fiber placement using a whole consisting of a patternless mirror-image fiber placement device and a defect monitoring system, wherein some components of the patternless mirror-image fiber placement device are omitted in the figure;

[0045] Figure 3 It is a schematic diagram of the end of the whole composed of a left conductive plate, a left tension spring, a right conductive plate, a right tension spring, a pressure roller, and a supporting device;

[0046] Figure 4 A schematic diagram of the process of monitoring internal defects in the patternless mirror fiber placement process using a defect monitoring system;

[0047] Figure 5 This is a schematic diagram of the ribbon installation process;

[0048] Figure 6It is a schematic diagram when the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is greater than 10nF and less than or equal to 30nF and the maximum capacitance is greater than 20nF and less than or equal to 40nF, wherein the detection position is the product of the laying time and the laying speed;

[0049] Figure 7 is a schematic diagram when the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is greater than 30 nF and the maximum capacitance is greater than 40 nF, wherein the detection position is the product of the laying time and the laying speed;

[0050] Figure 8 is a schematic diagram when the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is greater than 30 nF and the maximum capacitance is greater than 40 nF, wherein the detection position is the product of the laying time and the laying speed;

[0051] Fig. 9 yes Figure 6 Cross-sectional view at 60mm in the middle detection position;

[0052] Fig.10 yes Figure 7 Cross-sectional view at 40mm in the middle detection position;

[0053] Fig.11 yes Figure 8 Cross-sectional view at 60mm in the middle detection position;

[0054] Among them, 1-pressure roller, 2-cylinder a, 3-cylinder b, 4-laser heater, 5-motor, 6-driven wheel, 7-cylinder c, 8-material tray, 9-connector, 10-main board, 11-right conductive plate, 12-left tension spring, 13-capacitance detection device, 14-host computer, 15-ribbon, 16-bracket, 17-support device. DETAILED DESCRIPTION

[0055] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0056] A defect monitoring system for patternless mirror wire laying process, such as Figure 1 As shown, the patternless mirror-image wire placement equipment includes a left part and a right part;

[0057] The right part includes a main plate 10, a pressure component, a shearing component, a re-feeding component, a tension component, a heat source component, a connecting component 9 and a wire placement end movement mechanism;

[0058] The pressure component, the shearing component, the re-feeding component and the tension component are arranged in sequence from front to back along the wire running direction;

[0059] The pressure component includes a pressure roller 1, a support device 17, and a cylinder a2. The central axis of the pressure roller 1 is parallel to the front-rear direction. The support device 17 is located on the right side of the pressure roller 1 and connected to it. The cylinder a2 is fixed on the main plate 10 and is used to push the pressure roller 1 to the left.

[0060] The shearing component includes a cylinder b3 and a blade. The cylinder b3 is used to drive the blade to shear the ribbon. The cylinder b3 is fixed on the main plate 10.

[0061] The heavy-feeding component includes a driving wheel, a driven wheel 6, a motor 5 and a cylinder c 7. The driving wheel and the driven wheel 6 are arranged vertically and parallel to the left and right directions. The motor 5 is used to drive the driving wheel to rotate, and the cylinder c 7 is used to press the driven wheel 6 onto the driving wheel. The motor 5 and the cylinder c 7 are fixed on the main plate 10.

[0062] The tension component includes a material tray 8 and a brake 15. The material tray 8 is used to wind the ribbon, and the brake 15 is used to provide torque for the material tray 8 to maintain a stable tension force for wire feeding. The material tray 8 and the brake 15 are both fixed on the main plate 10.

[0063] The heat source component includes a laser heater 4, which is used to heat the ribbon, and the laser heater 4 is fixed on the main plate 10;

[0064] The connecting member 9 is fixed on the main plate 10 and connected to the end of the wire placement end movement mechanism;

[0065] The process of placing wires using the mirror-image wire placing equipment without a mold is now explained by taking the wire placing process twice as an example:

[0066] (1) Ribbon installation;

[0067] like Figure 5 As shown, after the ribbon 15 is wound on the material roll and loaded into the wire laying channel, it leaves the material roll, passes between the driving wheel and the driven wheel, and the blade to the pressure roller, and is then fixed on the bracket 16, which is a vertical frame or a truss fixed on the ground. After that, the connecting piece is connected to the end of the wire laying end movement mechanism (mechanical arm);

[0068] When the ribbon 15 passes between the driving wheel and the driven wheel, the cylinder c starts, and the driven wheel presses the ribbon 15 onto the driving wheel to achieve compression of the ribbon 15; the motor starts, drives the driving wheel to rotate, and drives the driven wheel to squeeze out the ribbon 15;

[0069] When the ribbon 15 passes through the pressing rollers, the cylinder a is started to push out the pressing rollers on both sides, and cooperate with the pressing rollers on the opposite side to squeeze the ribbon 15, thereby further pressing the ribbon 15;

[0070] (2) First wire laying;

[0071] After the ribbon 15 is fixed on the bracket 16, the wire laying end motion mechanism starts to move along the wire laying path. At the same time, the laser heater 4 is started to heat the ribbon 15. When the first wire laying is about to be completed, the cylinder b is started to drive the blade to shear the ribbon 15 and cut off the excess part. After shearing, the cylinder b is reset, and the reserved ribbon 15 between the blade and the pressure roller continues to be laid until the first laying is completed.

[0072] (3) Second wire laying;

[0073] After the first laying is completed, the end-of-wire laying motion mechanism moves to the initial position, and then starts to move along the wire laying path (the two ribbons 15 laid for the second time are located on the two sides of the two ribbons 15 laid in the first laying process that are away from each other). At the same time, the laser heater 4 is started to heat the ribbon 15. When the second laying is about to be completed, the cylinder b is started to drive the blade to shear the ribbon 15 and cut off the excess part. After shearing, the cylinder b is reset, and the reserved ribbon 15 between the blade and the pressure roller continues to be laid. After the second laying is completed, the cylinder c, the motor, the cylinder a, the cylinder c, and the laser heater 4 are turned off, and the connection between the connector and the end of the end-of-wire laying motion mechanism is disconnected;

[0074] like Figure 2 and Figure 3 As shown, the defect monitoring system includes a left conductive plate, a left tension spring 12, a right conductive plate 11, a right tension spring, a capacitance detection device 13 and a host computer 14;

[0075] The left conductive plate and the right conductive plate 11 are arranged symmetrically, and the left tension spring 12 and the right tension spring are arranged symmetrically;

[0076] The left end of the left conductive plate is directly connected to the support device 17 of the left part, and the middle part is connected to the support device 17 of the left part through the left tension spring 12. The right end of the left conductive plate is located in front of the pressure roller 1 of the left part along the wire feeding direction;

[0077] The right end of the right conductive plate 11 is directly connected to the support device 17 of the right part, and the middle part is connected to the support device 17 of the right part through the right tension spring. The left end of the right conductive plate 11 is located in front of the pressure roller 1 of the right part along the wire feeding direction;

[0078] The left conductive plate and the right conductive plate 11 are respectively connected to the positive electrode interface and the negative electrode interface of the capacitance detection device 13, and the capacitance detection device 13 is used to output capacitance data;

[0079] The host computer 14 is connected to the USB communication interface of the capacitance detection device 13 via a network cable;

[0080] The process of using the defect monitoring system to monitor internal defects in the wire laying process is as follows: Figure 4 As shown, in each wire laying process, the left conductive plate and the right conductive plate are controlled to continuously contact with the two sides of the two wires of this wire laying process that are away from each other, and the capacitance data of each wire laying process is obtained by the capacitance detection device. After the capacitance data of each wire laying process is processed to obtain the corresponding capacitance curve, the capacitance curve is analyzed to obtain the defect detection result. The abscissa of the capacitance curve is the wire laying length (i.e., the product of the wire laying time and the wire laying speed), and each wire laying process is timed from 0, and the ordinate of the capacitance curve is the capacitance;

[0081] When the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is less than or equal to 10nF (such as Figure 6 As shown in the figure, the defect detection result is: the whole (i.e., composite material) composed of the silk ribbons laid in this and all previous silk laying processes has no obvious defects; no obvious defects means that the total area of ​​gaps and delaminations on the cross section of the whole composed of the silk ribbons laid in this and all previous silk laying processes accounts for less than 3%; in order to verify whether the defect monitoring method is accurate, the defect detection result is obtained. Figure 6 The cross-sectional view at the detection position 60mm is as follows: Fig. 9 As shown, the test shows Fig. 9 The total area of ​​voids and delaminations in the cross section accounts for 0.47%, which is consistent with the above conclusion that "the total area of ​​voids and delaminations on the cross section accounts for less than 3%", which shows that the defect monitoring method of the present invention is accurate;

[0082] When the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is greater than 10nF and less than or equal to 30nF, and the maximum capacitance is greater than 20nF and less than or equal to 40nF (such as Figure 7 As shown in the figure, the defect detection result is: the whole (i.e., composite material) composed of the silk ribbons laid in this and all previous silk laying processes has relatively serious defects; relatively serious defects are that the total area of ​​voids and delaminations on the cross section of the whole composed of the silk ribbons laid in this and all previous silk laying processes is greater than or equal to 3% and less than 8%; in order to verify whether the defect monitoring result is accurate, the following is obtained: Figure 7 The cross-sectional view at the detection position 60mm is as follows: Fig.10 As shown, the test shows Fig.10 The total area of ​​voids and delaminations in the cross section accounts for 3.79%, which is consistent with the above conclusion that "the total area of ​​voids and delaminations on the cross section accounts for more than or equal to 3% and less than 8%", which shows that the defect monitoring method of the present invention is accurate;

[0083] When the difference between the maximum and minimum capacitance of the capacitance curve is greater than 30nF and the maximum capacitance is greater than 40nF (such as Figure 8As shown in the figure, the defect detection result is: the whole (i.e., composite material) composed of the silk ribbons laid in this and all previous silk laying processes has very serious defects; a very serious defect is that the total area of ​​voids and delaminations on the cross section of the whole composed of the silk ribbons laid in this and all previous silk laying processes accounts for more than or equal to 8%; in order to verify whether the defect monitoring result is accurate, the following is obtained: Figure 8 The cross-sectional view at the detection position 60mm is as follows: Fig.11 As shown, the test shows Fig.11 The total area of ​​voids and delaminations in the cross section accounts for 13.635%, which is consistent with the above conclusion that "the total area of ​​voids and delaminations on the cross section accounts for more than or equal to 8%", which shows that the defect monitoring method of the present invention is accurate;

[0084] If the silk ribbons laid by this and all previous laying processes have no obvious defects as a whole, continue laying. If there are more serious defects, adjust the process parameters (such as laying pressure, laser power, and laying speed) to improve the quality of subsequent laying. Increasing the laying pressure is a general method. When the laying pressure is too low, pressurization can usually significantly improve the defect situation. However, if the laying pressure itself is already relatively high, increasing the laying pressure will not help much in improving the effect. For defects caused by temperature problems, it is necessary to judge the appropriate laser power through the temperature curve of the infrared thermal imager. Reduce the power when the temperature is high and increase the power when the temperature is low. If there are very serious defects, directly scrap the sample and proceed with new laying.

Claims

1. A defect monitoring system for patternless mirror fiber placement process, characterized in that: The patternless mirror-image fiber placement equipment includes a symmetrical left part and a right part; The right part comprises a main body plate (10) and a pressure component, wherein the pressure component comprises a pressure roller (1), a supporting device, and a cylinder a (2), wherein the central axis of the pressure roller (1) is parallel to the front-rear direction, the supporting device is located on the right side of the pressure roller (1) and is connected thereto, and the cylinder a (2) is fixed on the main body plate (10) and is used to push the pressure roller (9) to the left; The defect monitoring system comprises a left conductive plate, a left tension spring (12), a right conductive plate (11), a right tension spring and a capacitance detection device (13); The left end of the left conductive plate is directly connected to the support device of the left part, the middle part is connected to the support device of the left part through the left tension spring (12), and the right end of the left conductive plate is located in front of the pressure roller (1) of the left part along the wire running direction; The right end of the right conductive plate (11) is directly connected to the support device of the right part, the middle part is connected to the support device of the right part through the right tension spring, and the left end of the right conductive plate (11) is located in front of the pressure roller (1) of the right part along the wire running direction; The left conductive plate and the right conductive plate (11) are respectively connected to the positive electrode interface and the negative electrode interface of a capacitance detection device (13), and the capacitance detection device (13) is used to output capacitance data.

2. According to claim 1, a defect monitoring system for patternless mirror fiber placement process is characterized in that: The left conductive plate and the right conductive plate (11) are arranged symmetrically, and the left tension spring (12) and the right tension spring are arranged symmetrically.

3. The defect monitoring system in the process of patternless mirror fiber placement according to claim 1 is characterized in that: The defect monitoring system also includes a host computer (14), and the host computer (14) is connected to the USB communication interface of the capacitance detection device (13) via a network cable.

4. The defect monitoring system in the process of patternless mirror fiber placement according to claim 1 is characterized in that: The right part also includes a shearing component, a re-feeding component, a tension component, a heat source component, a connecting piece (9), and a wire laying end movement mechanism. The pressure component, the shearing component, the re-feeding component, and the tension component are arranged in sequence from front to back along the wire running direction. The shearing component comprises a cylinder b (3) and a blade, wherein the cylinder b (3) is used to drive the blade to shear the ribbon, and the cylinder b (3) is fixed on the main plate (10); The re-feeding component comprises a driving wheel, a driven wheel (6), a motor (5) and a cylinder c (7), wherein the driving wheel and the driven wheel (6) are arranged vertically and parallel to the left and right directions, the motor (5) is used to drive the driving wheel to rotate, the cylinder c (7) is used to press the driven wheel (6) onto the driving wheel, and the motor (5) and the cylinder c (7) are fixed on the main body plate (10); The tension component comprises a material tray (8) and a brake (15), wherein the material tray (8) is used for winding the ribbon, and the brake (15) is used for providing torque to the material tray (8) to maintain a stable tension force for wire feeding, and the material tray (8) and the brake (15) are both fixed on the main plate (10); The heat source component comprises a laser heater (4), the laser heater (4) is used to heat the ribbon, and the laser heater (4) is fixed on the main body plate (10); The connecting piece (9) is fixed on the main plate (10) and connected to the end of the wire placement end movement mechanism.

5. A defect monitoring method in a patternless mirror fiber laying process, characterized in that: A defect monitoring system for patternless mirror-image fiber placement process as claimed in any one of claims 1 to 4 is used; Mirror-image laying without a mold means laying two ribbons in a mirror-symmetrical manner without using a mold, and repeating the laying process multiple times; Defect monitoring means controlling the left conductive plate and the right conductive plate (11) to keep in contact with the two opposite sides of the two wires in the current wire laying process in each wire laying process, obtaining capacitance data of each wire laying process, processing the capacitance data to obtain a capacitance curve, and then analyzing the capacitance curve to obtain a defect detection result; The ordinate of the capacitance curve is capacitance, and each wire laying process corresponds to one capacitance curve.

6. The defect monitoring method in the process of patternless mirror fiber placement according to claim 5 is characterized in that: The horizontal axis of the capacitance curve is the laying time or the product of the laying time and the laying speed, and each laying process starts from 0.

7. The defect monitoring method in the process of patternless mirror fiber placement according to claim 5 is characterized in that: For two adjacent fiber laying processes, the two ribbons laid in the latter fiber laying process are located on two sides of the two ribbons laid in the former fiber laying process which are away from each other.

8. The defect monitoring method in the process of patternless mirror fiber placement according to claim 7 is characterized in that: When the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is less than or equal to 10nF, the defect detection result is: the whole composed of the silk ribbons laid in this and all previous laying processes has no obvious defects; When the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is greater than 10nF and less than or equal to 30nF, and the maximum capacitance is greater than 20nF and less than or equal to 40nF, the defect detection result is: the whole composed of the silk ribbons laid in this and all previous laying processes has relatively serious defects; When the difference between the maximum capacitance and the minimum capacitance of the capacitance curve is greater than 30nF and the maximum capacitance is greater than 40nF, the defect detection result is: the whole composed of the silk ribbons laid in this and all previous laying processes has very serious defects; No obvious defects means that the total area of ​​voids and delaminations on the cross section of the ribbons laid in this and all previous laying processes is less than 3%; The more serious defect is that the total area of ​​voids and delaminations on the cross section of the entire ribbon laid by this and all previous laying processes is greater than or equal to 3% and less than 8%; A very serious defect is that the total area of ​​voids and delaminations on the overall cross-section formed by the silk ribbons laid in this and all previous laying processes accounts for more than or equal to 8%.

Images