Carbon nanotube sensor applied to online manufacturing monitoring and preparation method thereof

Abstract

The invention relates to a carbon nanotube sensor applied to on-line manufacturing monitoring and a preparation method of the carbon nanotube sensor, and solves the problems that a traditional patch type sensor is poor in chemical compatibility, cannot monitor the forming process and the like. The carbon nanotube sensor comprises a matrix and a dispersion liquid attached to the matrix, the matrix is a polyimide flexible adhesive tape material resistant to the high temperature of 200 DEG C, the dispersion liquid comprises 0.1% by mass of a carbon nanotube, 3% by mass of triton and an aqueous solution, and the carbon nanotube is a multi-walled carbon nanotube with the inner diameter of 10 nm, the outer diameter of 20 nm and the length of 30 [mu] m. The preparation method of the carbon nanotube sensor comprises the step of forming a layer of 100 [mu] m two-dimensional micro-nano carbon sensing film on the surface of a polyimide flexible adhesive tape material by using a spraying system. The molding time and the rejection rate of the special phenolic composite material can be effectively reduced, and powerful guarantee is provided for the safety of equipment related to the special phenolic composite material and the product quality.

Description

Technical Field

[0001] This invention relates to the field of intelligent sensors and intelligent monitoring technology, and in particular to flexible carbon nanotube sensors for online monitoring and sensing of composite material molding processes and their preparation technology. Background Technology

[0002] Specialty phenolic composite materials have been widely used in aerospace, shipbuilding, and transportation industries. However, their molding mechanism is complex and influenced by numerous factors. Currently, the molding process is still limited to "pre-molding process control and post-molding quality inspection," lacking data on the "molding process itself." The complex resin flow and dynamic curing phenomena caused by the molding process can easily lead to process defects such as insufficient wetting, resin deficiency / richness, and uneven temperature and pressure, resulting in deformation, delamination, and degradation of mechanical properties in composite structural parts, seriously affecting the service safety of manufactured products. Traditional piezoelectric, fiber optic, and ultrasonic sensor technologies suffer from problems such as increased weight, introduction of defects, complex wiring, and difficulty in installation and removal, making it difficult to conduct efficient and accurate online molding monitoring of specialty phenolic composite materials. There is an urgent need to leverage the unique advantages of cutting-edge carbon nanomaterials such as carbon nanotubes, including high strength, low density, high electrical sensitivity, and the ability to fuse with any surface / interface. This would allow for the creative construction of a system that can easily, quickly, and non-destructively integrate with the surface of complex composite material mold systems, while also accurately and in real-time monitoring the complex physical quantities of composite resins during curing and use. This would provide a theoretical foundation and technical support for developing a new generation of intelligent composite material equipment capable of monitoring its entire lifecycle, as well as for guiding improvements in thermal protection molding processes such as temperature settings, wetting degree adjustment, and mold pressure testing. Summary of the Invention

[0003] This invention provides a carbon nanotube sensor for online manufacturing monitoring of special phenolic resin composite materials and its preparation method, which solves the problems of poor chemical compatibility and inability to monitor the molding process of traditional patch sensors.

[0004] This invention is achieved through the following technical solutions: A carbon nanotube sensor for online manufacturing monitoring includes a matrix and a dispersion attached to the matrix. The matrix is ​​a flexible polyimide tape material resistant to 200°C. The dispersion includes 0.1% by mass of carbon nanotubes, 3% by mass of Triton, and an aqueous solution. The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of 10 nm, an outer diameter of 20 nm, and a length of 30 μm.

[0005] The surface of the carbon nanotube sensor is coated with graphene sheets.

[0006] The graphene sheet is a 10-30 mg graphene sheet with a lattice size of 30 nm.

[0007] The dispersion contains 10-30 mg of graphene sheets with a lattice size of 30 nm.

[0008] The carbon nanotube sensor is prepared by forming a 100μm two-dimensional micro / nano carbon sensing film on the surface of a polyimide flexible tape material using a spraying system.

[0009] The carbon nanotube sensor described herein is applied to the online manufacturing monitoring of special phenolic resin composite materials as follows: A suitable special phenolic resin slurry for the flow-through process is selected, and a curing chamber for the phenolic resin slurry is constructed according to the VARTM process based on different ambient temperatures. The chamber is sealed with sealing tape 1. Simultaneously, the prepared carbon nanotube sensor 2 is applied inside the VARTM curing chamber. During the resin feeding process through the feed pipe 3 and resin collector 4, the sensor's sensing area is fully integrated with the resin, achieving integrated fusion of the composite material mold system. The curing time is controlled by adjusting the vacuum pressure and the ratio of fast / slow curing agents within the chamber using a vacuum pump 5, thus controlling the curing speed and pressure of the special phenolic resin. To monitor resin curing, a vacuum pressure of 0.01 atm and a resin / curing agent ratio of 111:5 are selected to eliminate interference from the external environment.

[0010] The method for applying the carbon nanotube sensor to online manufacturing monitoring of special phenolic resin composite materials is as follows: A large number of sensor dots (3×3) are sprayed onto a carbon nanotube sensor 2 as a base. Signals are transmitted externally via sensor leads 15. The carbon nanotube sensors 2 are distributed within the mold to capture resin flow signals. During resin polymerization, environmental changes caused by the internal curing reaction are captured in real time by the carbon nanotube sensors. The reading of the carbon nanotube sensors 2 remains constant until the curing reaction is essentially complete. Combining the data from the carbon nanotube sensors 2 (which eliminates temperature drift) with differential thermal analysis, the specific resin curing status is obtained, and the resin curing rate is calculated. This enables the analysis and acquisition of information such as resin flow and curing rate within the resin, represented by temperature and pressure. Furthermore, by combining the temperature and pressure data converted from the electrical signals of the arrayed carbon nanotube sensors 2, structural analysis data such as differential thermal analysis and scanning microscopy of the special phenolic resin, and the performance characteristics of the phenolic resin, a special phenolic resin curing-structure-performance correlation is constructed.

[0011] Furthermore, before resin injection, the carbon nanotube sensor 2, which has already been laid out, is led out through the external electrode 9 and connected to the external circuit to the multimeter 7 of the data acquisition system 6. A piezoresistive signal detection and reading module is built using LabVIEW software to realize the real-time acquisition and data visualization of temperature and pressure data of the carbon nanotube sensor 2. The carbon nanotube sensor forms an electrical signal data spectrum of temperature and pressure field coupling based on the temperature and pressure process data changes generated by the resin flow.

[0012] This invention utilizes a carbon nanotube sensor with a micro / nano structure to sense changes in the flow field, temperature, and pressure within a specialty phenolic composite material. These internal conditions are then fed back via electrical signals. By analyzing the relationship between these electrical signals and the molding-structure-performance of the specialty phenolic composite material, the molding process is guided. Without introducing defects into the specialty phenolic composite material, the molding time and scrap rate are effectively reduced, providing strong assurance for the safety of equipment and the quality of products involving specialty phenolic composite materials. Attached Figure Description

[0013] Figure 1 Flowchart of carbon nanotube sensor fabrication and integrated molding process with special phenolic composite materials; Figure 2 Transmission microscope image of carbon nanotube sensor; Figure 3 Raman spectra of carbon nanotube sensors; Figure 4 Schematic diagram of the VARTM processing of specialty phenolic resin; Figure 5 Schematic diagram of data acquisition for integrated molding of special phenolic resin composite materials; Figure 6 Schematic diagram of monitoring signals for integrally molded composite resin; Figure 7 Figure showing the results of temperature drift elimination data from a carbon nanotube sensor. Figure 8 Graph of pressure calibration results for carbon nanotube sensor; Figure 9 Schematic diagram of a carbon nanotube array sensor; In the figure, 1 is sealing tape, 2 is carbon nanotube sensor, 3 is feed pipe, 4 is special resin collector, 5 is vacuum pump, 6 is digital acquisition system, 7 is multimeter, 8 is resin or prepreg, 9 is electrode, 10 is glue inlet pipe, 11 is vacuum bag, 12 is glue outlet pipe, 13 is plexiglass plate, 14 is pump port, and 15 is sensor lead wire. Detailed Implementation

[0014] This invention discloses a carbon nanotube sensor for online manufacturing monitoring of special phenolic resin composite materials and its preparation method. The following is a description of the sensor and its preparation method. Figure 1-9 The present invention will be further described below.

[0015] Regarding sensor types, a flexible two-dimensional carbon nanotube sensor that can be attached to the mold surface was developed. In terms of the integrated molding process of special phenolic composite materials monitored by the sensor, integrated molding and online molding monitoring of the sensor were carried out based on vacuum-assisted resin transfer molding (VARTM). By constructing the relationship between carbon nanotube material molding-structure-sensing performance, an online molding monitoring mechanism for composite materials was proposed. This mechanism guides the molding and preparation process of carbon nanotube sensors while simultaneously understanding and analyzing the internal polymerization of special phenolic composite materials during the molding process through the electrical signals provided by the sensors. This method can further realize the in-situ curing process monitoring of special phenolic composite prepregs, solving the problems of poor chemical compatibility and inability to monitor the molding process of traditional patch sensors.

[0016] The flowchart of carbon nanotube sensor fabrication, placement, and integrated molding monitoring process is as follows: Figure 1 As shown.

[0017] 1. Nanotube Material: Multi-walled carbon nanotubes with an inner diameter of 1-10 nm, an outer diameter of 10-20 nm, and a length of 10-30 μm were selected as raw materials. The carbon nanotubes were uniformly dispersed using the aqueous surfactant Triton, consisting of 0.1% by mass of multi-walled carbon nanotubes, 3% by mass of Triton, and an aqueous solution. Furthermore, polyimide, resistant to temperatures up to 200℃, was selected as the matrix. The carbon nanotubes were bonded to the matrix using common spraying techniques to construct the carbon nanotube sensor. Additionally, a special phenolic resin slurry suitable for the flow-through process was selected, and the molding time was adjusted according to different ambient temperatures, vacuum pressures, and the ratio of fast / slow curing agents to prepare for real-time monitoring of resin curing.

[0018] 2. Fabrication Process of Two-Dimensional Carbon Nanotube Temperature / Pressure Sensor: For the flexible carbon nanotube sensor, a carbon nanotube spraying process was used to form a 100μm two-dimensional micro / nano carbon sensing film on the surface of flexible, high-temperature resistant polyimide. The effects of processing parameters such as carbon nanotube concentration and the type of flexible substrate material on the film structure were investigated.

[0019] 3. Sensor / Composite Material Mold Integration Process and Online Monitoring Method: A two-dimensional sensor, prepared with optimized processing parameters, is encapsulated in heat-resistant materials such as polyimide and polyethylene terephthalate and then directly embedded into a VARTM mold. The sensor is connected to a digital source meter via wires at both ends to monitor the internal environment of the mold. During the feeding process of special phenolic resin, a carbon nanotube sensor is immersed in the resin solution. Utilizing the piezoresistive properties of the carbon nanotubes, it senses the entire process of resin material filling and curing within the mold, achieving integrated integration of the composite material and sensor inside the mold and online monitoring of the curing process.

[0020] 4. Microstructure Control and Characterization Experiments of Sensing Network: Leveraging the physical properties of carbon nanotube dispersions, an average lateral size of approximately 15-20 μm was obtained in the dispersion using ultravelocity sedimentation. This allowed for control over the internal structure of the carbon nanotubes within the dispersion. Dynamic light scattering was then used to obtain the size distribution of the carbon nanotubes. Further, transmission electron microscopy and Raman spectroscopy were employed to characterize the thin film structure, obtaining information on the sensor film morphology, thickness, and packing density. Based on these experimental results, the relationship between the optimization of the carbon nanotube microstructure network fabrication process, its microstructure, and sensing performance was established and analyzed.

[0021] 5. Multi-physical quantity state monitoring and analysis: Under different curing conditions such as curing temperature, curing pressure, and fast / slow curing agent ratios, the electrical signals, thermal flow signals, and viscosity signals obtained by three different methods—carbon nanotube sensors, differential thermal analysis, and rheology—during the resin molding process are compared. The correlation between these signals reveals the monitoring mechanism of the carbon nanotube sensor for important physical parameters such as resin gel time, curing rate, temperature, and pressure.

[0022] Example: 1. Rapid fabrication technology of carbon nanotube sensors and their integration with composite material mold systems Flexible carbon nanotube sensors can be matched with resin curing monitoring on mold surfaces with different curvatures. However, due to limitations of traditional processing techniques, traditional strain gauge sensor processing methods suffer from low processing accuracy, slow molding efficiency, and inability to mass-produce, affecting the signal stability of the sensor and its subsequent applications. Therefore, this invention selects multi-walled carbon nanotubes with an inner diameter of 10 nm, an outer diameter of 20 nm, and a length of 30 μm as raw materials. A carbon nanotube dispersion is prepared by combining 0.1% by mass of carbon nanotubes, 3% by mass of Triathlon, and an aqueous solution. Furthermore, a polyimide flexible tape material resistant to 200℃ is selected as the matrix. The carbon nanotube dispersion is sprayed to bond the carbon nanotubes with the polyimide matrix to construct a carbon nanotube sensor. The sensing area is the carbon nanotube coating portion, with a thickness between 5 and 20 μm.

[0023] like Figure 2 As shown, the microscopic nanotube structure of the carbon nanotubes in the sensing layer can be observed using transmission microscopy and Raman spectroscopy, indicating that the carbon nanotube sensor can generate a discontinuous tubular structure with an electron tunneling effect; as Figure 3 As shown, the characteristic peaks D and G of the graphene-like carbon structure on the surface of the carbon nanotube sensor can also be clearly observed from the Raman spectrum, indicating that the carbon nanotubes have a conductivity similar to that of graphene. Therefore, in order to develop carbon nanotubes with good conductivity and discontinuous micro-nano conductive structures suitable for temperature sensing and piezoresistive signal sensing, further guidance can be given to the conductivity performance of carbon nanotube sensors.

[0024] In addition, special phenolic resin slurry suitable for the flow-through process is selected and, according to different ambient temperatures, [following / adjusting]... Figure 4 The VARTM process shown constructs a curing chamber for the phenolic resin slurry, which is sealed using sealing tape 1. Simultaneously, a prepared carbon nanotube sensor 2 is attached to the inside of the VARTM curing chamber. During the resin feeding process through the feed pipe 3 and the special resin collector 4, the sensor's sensing area is fully integrated with the resin, achieving seamless integration of the composite material mold system. The curing time can be controlled by adjusting the vacuum pressure and the ratio of fast / slow curing agents within the chamber using a vacuum pump 5. This controls the curing speed and pressure of the special phenolic resin, impacting resin curing monitoring. Therefore, a vacuum pressure of 0.01 atm and a resin / curing agent ratio of 111:5 are selected to eliminate interference from the external environment in resin curing monitoring.

[0025] 2. Flexible carbon nanotube sensors for multi-physical quantity detection in composite resin molding The resin curing process is crucial to the reliability of composite structures. Due to the complex physical processes and chemical reactions involved in the resin curing process, understanding and controlling the resin curing process to improve structural reliability is a significant challenge for specialty phenolic composite materials.

[0026] like Figure 5 As shown, a vacuum is drawn at one end of the pump port 14 to provide a pressure difference. Resin is introduced into a vacuum bag 11 sealed by sealing tape 1 through the inlet tube 10. After the resin is impregnated, it flows out through the outlet tube 12 at the end of the plexiglass plate 13. To understand the above complex process, the changes in the internal environment of the resin from injection to curing, such as temperature and pressure, can be inferred by the changes in the electrical signal of the sensor, providing reliable data for understanding the resin curing process. Before resin injection, the carbon nanotube sensor 2, which has already been laid out, is led out through the external electrode 9 and connected to the multimeter 7 of the data acquisition system 6. A piezoresistive signal detection and reading module is built using LabVIEW software to realize real-time acquisition and data visualization of the carbon nanotube sensor 2 data, such as... Figure 5 As shown. Specialty resin liquid material is injected into a mold to contact the sensor placed within the mold. The carbon nanotube sensor exhibits significant signal changes in response to the temperature and pressure changes generated by the resin flow, such as... Figure 6 As shown, this data is a graph of electrical signal data coupled by temperature and pressure fields.

[0027] To decouple the internal temperature and pressure environment, 10-30 mg of graphene sheets with a lattice size of 30 nm were added to the carbon nanotube dispersion sprayed onto the surface of the carbon nanotube sensor 2. This improved the conductivity of the material, allowing electrons in the conductive path to pass smoothly through the sensing region. This reduced the electron tunneling effect between different carbon nanotubes under high-temperature conditions, thus eliminating the temperature drift of the carbon nanotube sensor 2. The temperature drift elimination result of the carbon nanotube sensor 2 is as follows: Figure 7 As shown. The real-time pressure monitoring results of the carbon nanotube sensor 2 calibrated by the pressure gauge are as follows. Figure 8 As shown.

[0028] 3. Monitoring of the resin curing process using arrayed carbon nanotube sensors To better understand the internal resin flow during the resin polymerization process, a large number of sensors (approximately 3×3 dots) were sprayed onto a carbon nanotube sensor 2 as a base. Figure 9 As shown, the signal is transmitted externally via sensor lead 15, and carbon nanotube sensors 2 are distributed within the mold to capture the resin flow signal. During resin polymerization, environmental changes caused by the internal curing reaction are captured in real time by the carbon nanotube sensors until the curing reaction is essentially complete, at which point the reading of the carbon nanotube sensors 2 remains constant. By combining the data from the carbon nanotube sensors 2 (which eliminates temperature drift) with differential thermal analysis, the specific resin curing status is obtained, and the resin curing rate is calculated. This enables the analysis and acquisition of information such as resin flow and curing rate within the resin, represented by temperature and pressure. By combining the temperature and pressure data converted from the electrical signals of the arrayed carbon nanotube sensors 2, structural analysis data such as differential thermal analysis and scanning microscopy of special phenolic resins, and the performance characteristics of characteristic phenolic resins, a special phenolic resin curing molding-structure-performance correlation is constructed.

[0029] The specific embodiments described herein serve to explain the purpose of the invention, but are not intended to limit the scope of the invention.

Claims

1. A carbon nanotube sensor for online manufacturing monitoring, characterized in that: The product includes a matrix and a dispersion attached to the matrix. The matrix is ​​a polyimide flexible tape material that can withstand temperatures up to 200°C. The dispersion includes 0.1% by mass of carbon nanotubes, 3% by mass of Triton, and an aqueous solution. The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of 10 nm, an outer diameter of 20 nm, and a length of 30 μm.

2. A carbon nanotube sensor for online manufacturing monitoring according to claim 1, characterized in that: The surface of the carbon nanotube sensor is coated with graphene sheets.

3. A carbon nanotube sensor for online manufacturing monitoring according to claim 2, characterized in that: The graphene sheet is a 10-30 mg graphene sheet with a lattice size of 30 nm.

4. A carbon nanotube sensor for online manufacturing monitoring according to claim 1, characterized in that: The dispersion contains 10-30 mg of graphene sheets with a lattice size of 30 nm.

5. A method for preparing a carbon nanotube sensor as described in any one of claims 1-4 for online manufacturing monitoring, characterized in that: A 100μm two-dimensional micro / nano carbon sensing film was formed on the surface of a polyimide flexible tape material using a spraying system.

6. The carbon nanotube sensor according to any one of claims 1-4, characterized in that: The method for applying the carbon nanotube sensor to the online manufacturing monitoring of special phenolic resin composite materials is as follows: Select a special phenolic resin slurry suitable for the flow process and build a curing chamber for the phenolic resin slurry according to different ambient temperatures and the VARTM process. Seal it with sealing tape (1). At the same time, attach the prepared carbon nanotube sensor (2) to the inside of the VARTM curing chamber. During the process of the resin being fed through the feed pipe (3) and the resin collector (4), allow the sensing area of ​​the sensor to fully integrate with the resin to achieve the integration of the composite material mold system. Adjust the vacuum pressure and the ratio of fast / slow curing agent in the chamber by the vacuum pump (5) to control the curing time, control the curing speed and curing pressure of the special phenolic resin, and affect the resin curing monitoring. Select a vacuum pressure of 0.01 atm and a resin / curing agent ratio of 111:5 to eliminate the interference of the external environment on the resin curing monitoring.

7. The carbon nanotube sensor according to any one of claims 1-4, characterized in that: The method of applying the carbon nanotube sensor to the online manufacturing monitoring of special phenolic resin composite materials is as follows: a large number of sensor arrays are sprayed on the carbon nanotube sensor (2) as the basis, and the signal is transmitted externally by the sensor lead wire (15). The carbon nanotube sensor (2) is distributed in the mold to capture the flow signal of the resin. During the resin polymerization process, the environmental changes brought about by the internal curing reaction are captured in real time by the carbon nanotube sensor. Until the curing reaction is basically over, the reading of the carbon nanotube sensor (2) remains constant. Combined with the data of the carbon nanotube sensor (2) that eliminates temperature drift and differential thermal analysis, the specific resin curing condition is obtained, the resin curing rate is calculated, and the analysis and acquisition of resin flow and curing rate information inside the resin represented by temperature and pressure are realized. Combined with the temperature and pressure conditions converted by the arrayed carbon nanotube sensor (2), the differential thermal analysis of special phenolic resin, the scanning microscope structural analysis data, and the performance of characteristic phenolic resin, the special phenolic resin curing molding-structure-performance correlation is constructed.

8. The carbon nanotube sensor according to claim 7, characterized in that: Before resin injection, the carbon nanotube sensor (2) that has been laid out is led out through the external electrode (9) and connected to the external circuit to the multimeter (7) of the data acquisition system (6). The piezoresistive signal detection and reading module is built through the computer LabVIEW software to realize the real-time acquisition and data visualization of the temperature and pressure data of the carbon nanotube sensor (2). The carbon nanotube sensor forms an electrical signal data spectrum of temperature and pressure field coupling based on the temperature and pressure process data changes generated by the resin flow.

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