Carbon fiber carbonization quality monitoring method based on roller surface resistance

Abstract

The invention relates to a carbon fiber carbonization quality monitoring method based on roller surface resistance. The method comprises the following steps: 1) connecting an ampere meter to electrodes at two ends of a roller; (2) a motor I drives a roller to rotate; (3) fly wires generated by the carbon fiber tows due to fiber breakage are stacked on a roller and wound on the surface of the roller under the rotation of the roller, and a conductive line formed by the fly wires is formed to be communicated with an electrode; 4) obtaining R-t function images by continuously collecting data, and then comparing the R-t function images with R0 to obtain actual conditions in the carbonization furnace, so that the carbonization quality of the carbon fiber tows is controlled by adjusting the temperature; according to the method, the carbonization quality of the carbon fibers can be accurately and effectively monitored in real time, then the temperature of the carbonization furnace is adjusted according to the actual carbonization quality, and the remarkable effect of improving the product quality stability is achieved.

Description

Technical Field

[0001] This invention relates to a method for monitoring the carbonization quality of carbon fibers, specifically a method for monitoring the carbonization quality of carbon fibers based on the surface resistance of rollers, belonging to the field of quality monitoring technology in the carbon fiber production process. Background Technology

[0002] Carbon fiber, as a key component of high-performance composite materials, has been widely used in many fields such as aerospace, automobile manufacturing, sporting goods manufacturing, and building materials due to its low density, high strength, high modulus and excellent corrosion resistance.

[0003] The preparation process of carbon fiber encompasses key stages such as precursor pyrolysis and carbonization. In the pyrolysis stage, the precursor fiber is placed in a high-temperature environment, where elements such as hydrogen and oxygen gradually dissolve, thus constructing a high-carbon-content basic structure. The subsequent carbonization stage involves deep processing of the fiber at even higher temperatures, a process that further increases the carbon content and optimizes its crystallinity. Appropriate pyrolysis and carbonization temperatures not only effectively promote the removal of residual hydrogen and oxygen from the precursor fiber but also significantly improve its carbon content and crystallinity. From the initial precursor fiber through a series of processing steps until carbonization, carbon fiber undergoes significant changes in both appearance and properties, ultimately forming a carbon structure with high purity and high crystallinity, exhibiting excellent mechanical properties and chemical stability. Furthermore, the carbonization temperature of carbon fiber directly affects the size, orientation, and defect density of graphite crystallites, ultimately determining the mechanical properties of the carbon fiber (such as tensile strength and modulus).

[0004] However, if the carbonization quality of carbon fiber fails to meet the standards during production, it indicates that the residual amount of hydrogen and oxygen in the precursor fiber exceeds the minimum limit specified for that stage. This type of problem is highly likely to significantly reduce the durability of the carbon fiber, and its various performance characteristics will also decline. Therefore, in order to improve the carbonization quality of carbon fiber and ensure the manufacture of high-quality composite materials, strict quality monitoring throughout the entire carbon fiber production process is particularly necessary. However, the conventional testing method usually involves taking a portion of the fly filaments from the roller and sending them for testing. This process is overly cumbersome, and the complex and variable operating environment often results in a time lag, making it difficult to monitor the carbonization quality of carbon fiber in real time during production.

[0005] Therefore, in order to solve the above-mentioned technical problems, it is indeed necessary to provide an innovative method for monitoring the carbonization quality of carbon fibers based on the surface resistance of rollers, so as to overcome the defects in the prior art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for monitoring the carbonization quality of carbon fibers based on the surface resistance of rollers. This method monitors the carbonization quality of the produced carbon fibers in real time by observing the rate of change in the resistance value of the winding rollers and fly yarns. It can also determine whether the temperature inside the carbonization furnace is too high or too low, and then adjust the furnace temperature in real time to improve the stability of the carbon fiber product quality.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for monitoring the carbonization quality of carbon fiber based on the surface resistance of a roller, which employs a carbon fiber carbonization quality monitoring device. This device includes a motor I, a pair of bearing seats, a roller, electrode plates, a guide rail, a slider, a crank-connecting rod mechanism, and a pressure drop device. The motor I is connected to and drives the roller to rotate; the roller is pivotally connected to the bearing seats; the electrode plates are respectively mounted on the bearing seats and have electrodes on them; the guide rail is fixed above the bearing seats; the slider cooperates with the guide rail and can move along the guide rail; the crank-connecting rod mechanism connects to and drives the slider to reciprocate; the pressure drop device is installed at the bottom of the slider and has a brush mounted on it; the brush can adhere to the surface of the roller. The monitoring method includes the following steps: 1) Connect the ammeter to the electrodes at both ends of the roller via a wire; 2) Start motor I, which transmits torque through the coupling to drive the roller to rotate; 3) The produced carbon fiber tows accumulate on the roller due to fiber breakage. As the roller rotates, it wraps around the surface, forming multiple conductive paths that are connected to the electrodes. 4) By continuously collecting data, the Rt function graph is obtained, and then compared with R0 to obtain the actual situation inside the carbonization furnace, so as to adjust the temperature to stabilize and control the carbonization quality of the carbon fiber bundle. 5) When the graph of the Rt function intersects with R=R0, the pressure drop device descends, and the brush cleans away the fly filaments from the entire surface of the roller. 6) After the fly filaments on the roller surface are cleaned, the crank connecting rod mechanism and pressure drop device will automatically shut down, and the brush will automatically reset.

[0008] The carbon fiber carbonization quality monitoring method based on roller surface resistance of the present invention is further described as follows: In step 4), R0 is a standard setting value, and the setting process of its value is as follows: When producing carbon fiber with qualified carbonization quality, the flying filaments are adsorbed on the roller. When the first resistance value is measured and calculated, the first flying filament conductive circuit is formed, and 50% of the value is set as R0.

[0009] The carbon fiber carbonization quality monitoring method based on roller surface resistance of the present invention is further described as follows: In step 4), the specific process of establishing the Rt function image is as follows: the broken carbon fiber, i.e., the fly filament, is adsorbed onto the roller surface and gradually covers the surface as the roller rotates, forming multiple fly filament conductive paths connected in parallel; then, the roller is connected to the electrodes on both sides, so that the series ammeter circuit is connected and its current value is measured; its resistance value is calculated by R=U / I; finally, data is continuously collected according to time t, and an Rt curve is generated.

[0010] The carbon fiber carbonization quality monitoring method based on roller surface resistance of the present invention is further described as follows: In step 4), the specific comparison process between the Rt function image and R0 is as follows: when the abscissa of the intersection point of the Rt function image and R=R0 is between t1 and t2, it reflects that the carbonization quality of the carbon fiber meets the standard; when it is less than t1, the temperature in the carbonization furnace is reduced, and when it is greater than t2, the temperature in the carbonization furnace is increased.

[0011] The carbon fiber carbonization quality monitoring method based on roller surface resistance of the present invention is further described as follows: the setting process for the values ​​of t1 and t2 is as follows: when producing carbon fibers with qualified carbonization quality, the resistance of the fly filaments is measured, and the resistance value decreases over time; when the Rt function graph intersects with R=R0, the x-coordinate of the intersection point is located between the desired t1 and t2; the temperature inside the carbonization furnace is gradually increased, and the x-coordinate of the intersection point is recorded each time; when the temperature rises to the point where the carbonization quality is unqualified, the x-coordinate of the intersection point for that time is set as t1; the same method is used to gradually decrease the temperature inside the carbonization furnace, and when the temperature decreases to the point where the carbonization quality is unqualified, the x-coordinate of the intersection point for that time is set as t2.

[0012] The carbon fiber carbonization quality monitoring method based on roller surface resistance of the present invention is further described as follows: In step 5), the specific method for cleaning carbon fiber fly filaments is as follows: start the motor II of the eccentric wheel, transmit motion to the crank, and sequentially link the connecting rod and the slider, so that the slider reciprocates along the guide rail; the pressure drop device descends, so that the brush descends to a height close to the roller, and the brush cleans the carbon fiber fly filaments under the reciprocating motion of the slider.

[0013] The carbon fiber carbonization quality monitoring method based on roller surface resistance of the present invention further comprises: the motor I is mounted on one of the bearing seats via a coupling; the two ends of the roller are pivotally connected between a pair of bearing seats via bearings, and the coupling of the motor I connects and drives the roller to rotate.

[0014] The carbon fiber carbonization quality monitoring method based on roller surface resistance of the present invention is further described as follows: the crank-connecting rod mechanism includes a connecting rod, a crank, an eccentric wheel, and a motor II; one end of the connecting rod is connected to a slider, and the other end is connected to the crank and driven by the crank; the crank is hinged to the eccentric wheel; the motor II is connected to and drives the eccentric wheel to rotate.

[0015] The carbon fiber carbonization quality monitoring method based on roller surface resistance of the present invention further includes: the brush is installed at the bottom of the pressure drop device by a spring.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The carbon fiber carbonization quality monitoring method based on roller surface resistance of the present invention combines the fly filaments adsorbed by the roller during the production of carbon fiber with its resistance characteristics. It monitors in real time whether the carbon fiber tow is qualified during the carbonization process by observing the rate of decline of the real-time Rt curve generated by continuously measured resistance values, and adjusts the temperature accordingly based on the changes in the curve, thereby improving the pass rate of carbon fiber product quality. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the carbon fiber carbonization quality monitoring device of the present invention.

[0018] Figure 2 yes Figure 1 A partial structural diagram.

[0019] Figure 3 yes Figure 1 The schematic diagram shows the structure of the slider, crank-connecting rod mechanism and pressure drop device.

[0020] Figure 4 This is a schematic diagram of the carbon fiber filament resistance measurement model of the present invention.

[0021] Figure 5 shows the Rt function images generated under different carbonization temperatures of the carbon fibers in this invention. Detailed Implementation

[0022] Please refer to the instruction manual appendix. Figure 1 To be continued Figure 3 As shown, the present invention is a carbon fiber carbonization quality monitoring device based on the surface resistance of a roller, which consists of several parts, including a motor I1, a pair of bearing seats 3, a roller 16, an electrode plate 4, a guide rail 5, a slider 7, a crank connecting rod mechanism, and a pressure drop device 14.

[0023] The motor I1 is connected to and drives the roller 16 to rotate. The roller 16 is pivotally connected to the bearing housing 3. Specifically, the motor I1 is mounted on one of the bearing housings 3 via a coupling 2. The two ends of the roller 16 are pivotally connected between a pair of bearing housings 3 via bearings 17, and the coupling 2 of the motor I1 connects to and drives the roller 16 to rotate.

[0024] The electrode plate 4 is mounted on a pair of bearing seats 3 by a number of bolts and nuts, and an electrode 13 is provided on it. An ammeter can be connected between the two electrodes 13.

[0025] The guide rail 5 is fixed above the bearing seat 3. The slider 7 cooperates with the guide rail 5 and can move along the guide rail 5.

[0026] The crank-connecting rod mechanism connects to and drives the slider 7 to reciprocate. In this embodiment, the crank-connecting rod mechanism consists of several parts, including a connecting rod 8, a crank 9, an eccentric wheel 10, and a motor II11. One end of the connecting rod 8 is connected to the slider 7, and the other end is connected to the crank 9, which drives the slider 7. The crank 9 is hinged to the eccentric wheel 10. The motor II11 connects to and drives the eccentric wheel 10 to rotate. The eccentric wheel 10 sequentially links the crank 9, the connecting rod 8, and the slider 7, causing the slider 7 to reciprocate.

[0027] The pressure drop device 14 is installed at the bottom of the slider 7, and a brush 15 is mounted on it. The brush 15 is mounted at the bottom of the pressure drop device 14 by a spring 6, and can adhere to the surface of the roller 16 to clean the filaments on the roller 16.

[0028] Please continue to refer to the instruction manual appendix. Figure 4 To be continued Figure 5 As shown, the method for monitoring the carbon fiber carbonization quality using the aforementioned carbon fiber carbonization quality monitoring device includes the following steps: 1) Connect the ammeter to the electrodes 13 at both ends of the roller 16 via a circuit, as shown in the attached diagram. Figure 4 As shown, the resistance of the carbon fiber flywire is measured in real time using an ammeter.

[0029] 2) Start the motor I1, which transmits torque through the coupling 2 to drive the roller 16 to rotate.

[0030] 3) The produced carbon fiber tows accumulate on the roller 16 due to fiber breakage. As the roller 16 rotates, it winds around the surface, forming multiple conductive paths that are connected to the electrode 13.

[0031] Specifically, the broken carbon fibers, or fly filaments, adhere to the surface of roller 16. As roller 16 rotates, they gradually cover the surface, forming multiple parallel conductive paths of the fly filaments. Therefore, let the resistance value of each fly filament conductive path be... The relationship between the measured resistance value R and the route resistance value is as follows: As the number of conductive paths in the fly filament increases (i.e., the parallel path increases), the resistance (R) gradually decreases. Therefore, the measured resistance value will decrease at both excessively high and low carbonization temperatures. However, excessively high carbonization temperatures lead to a lower carbon content in the carbon fiber, resulting in a lower resistance in the fly filament. Conversely, excessively low carbonization temperatures lead to a higher carbon content in the carbon fiber, resulting in a higher resistance in the fly filament. Using the parallel resistance formula, it can be seen that the measured total resistance decreases faster at higher carbonization temperatures and relatively more slowly at lower carbonization temperatures. This is reflected in the generated graph as follows: when the carbonization temperature is too high, the x-axis of the intersection point of the monitoring curve and R=R0 shifts to the left compared to the normal situation; when the carbonization temperature is too low, the intersection point shifts to the right compared to the normal situation.

[0032] 4) By continuously collecting data, the Rt function graph is obtained, and then compared with R0 to obtain the actual situation inside the carbonization furnace, thereby adjusting the temperature to stabilize and control the carbonization quality of the carbon fiber bundle.

[0033] Specifically, the process of establishing the Rt function graph is as follows: Broken carbon fibers, i.e., fly filaments, adhere to the surface of roller 16. As roller 16 rotates, they gradually cover the surface, forming multiple fly filament conductive paths connected in parallel. Then, roller 16 is connected to electrodes 13 on both sides, connecting the series-connected ammeter circuit and measuring its current value. The resistance value is then calculated using R=U / I. Finally, data is continuously collected over time t, and an Rt curve is generated, as shown in the attached figure. Figure 5 As shown.

[0034] R0 is a standard setting value. The process of setting its value is as follows: When producing carbon fiber with qualified carbonization quality, the flying filaments are adsorbed on the roller. When the first resistance value is measured and calculated, the first flying filament conductive circuit is formed. The value of 50% is set as R0.

[0035] Furthermore, the specific comparison process between the Rt function graph and R0 is as follows: when the x-coordinate of the intersection point of the Rt function graph and R=R0 is between t1 and t2, it reflects that the carbonization quality of the carbon fiber meets the standard, as shown in the attached figure. Figure 5 Curve 2. When it is less than t1, the temperature inside the carbonization furnace is reduced, as shown in the attached figure. Figure 5 Curve 1. If t2 is greater than t2, the temperature inside the carbonization furnace will increase, as shown in the attached figure. Figure 5 Curve 3.

[0036] The process for setting the values ​​of t1 and t2 is as follows: During the production of carbonized carbon fibers that meet quality standards, the resistance of the fly filaments is measured, and the resistance decreases over time. When the graph of the Rt function intersects with R=R0, the x-coordinate of the intersection point lies between the desired t1 and t2. The temperature inside the carbonization furnace is gradually increased, and the x-coordinate of each intersection point is recorded. When the temperature rises to the point where the carbonization quality is unacceptable, the x-coordinate of that intersection point is set as t1. The same method is used to gradually decrease the temperature inside the carbonization furnace. When the temperature drops to the point where the carbonization quality is unacceptable, the x-coordinate of that intersection point is set as t2.

[0037] 5) When the graph of the Rt function intersects with R=R0, the pressure drop device 14 drops, and the brush 15 cleans away the fly filaments on the entire surface of the roller 16.

[0038] The specific method for cleaning carbon fiber filaments in this step is as follows: Start the motor II11 of the eccentric wheel 10 to transmit motion to the crank 9, and sequentially link the connecting rod 8 and the slider 7, causing the slider 7 to reciprocate along the guide rail 5. The pressure drop device 14 descends, causing the brush 15 to descend to a height close to the roller 16, allowing the brush 15 to clean the carbon fiber filaments under the reciprocating motion of the slider 7.

[0039] 6) After the fly filaments on the surface of roller 16 are cleaned, the crank connecting rod mechanism and pressure drop device 14 are automatically shut off, and brush 15 is automatically reset.

[0040] In summary, the carbon fiber carbonization quality monitoring method based on roller surface resistance of this invention innovatively utilizes the correlation between the adhesion behavior of fly filaments on the surface of the winding roller during carbon fiber production and their conductivity. By acquiring the surface resistance signal of the roller 16 in real time and dynamically, a resistance-time (Rt) function curve is constructed, and the stability of the carbonization reaction process is evaluated in real time based on the slope characteristics of the curve. Compared with traditional offline detection methods, the method of this invention can instantly detect abnormal waves in the formation of graphite microcrystalline structures in the carbonization furnace by analyzing the time sequence of resistance value changes. Combined with the dynamic feedback of the curve morphology, a closed-loop control mechanism is established to achieve precise compensation of the temperature field in the carbonization furnace, thereby optimizing the formation conditions of disordered graphite structures inside the carbon fiber and improving batch consistency. This technical approach, which combines process defect characterization with dynamic resistance response, significantly reduces the defect rate caused by uneven temperature field distribution during the carbonization process.

[0041] The above-described specific embodiments are merely preferred embodiments of this invention and are not intended to limit this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A method for monitoring carbonization quality of carbon fibers based on roller surface resistance, characterized by: The device comprises a motor I, a pair of bearing seats, a roller, an electrode plate, a guide rail, a slider, a crank linkage mechanism and a pressure reducer; the motor I is connected to and drives the roller to rotate; the roller is pivoted to the bearing seat; the electrode plate is installed on the bearing seat and is provided with an electrode; the guide rail is fixed above the bearing seat; the slider is matched with the guide rail and can move along the guide rail; the crank linkage mechanism is connected to and drives the slider to move back and forth; the pressure reducer is installed at the bottom of the slider and is provided with a brush; the brush can be attached to the surface of the roller; The monitoring method comprises the following steps: 1) connecting an ammeter to the electrodes at both ends of the roller through a circuit; 2) starting the motor I to drive the roller to rotate through a shaft coupling; 3) the flying filaments produced by the broken carbon fibers are accumulated on the roller and are wound around the surface of the roller under the self-rotation of the roller to form a plurality of conductive circuits connected with the electrodes; 4) obtaining an R-t function image by continuously collecting data and then comparing the R-t function image with R0 to obtain the actual situation in the carbonization furnace so as to adjust the temperature to stabilize the carbonization quality of the carbon fiber tows; 5) when the R-t function image intersects with R=R0, the pressure reducer is lowered and the brush cleans the flying filaments on the surface of the roller; 6) after the surface of the roller is cleaned, the crank linkage mechanism and the pressure reducer are automatically turned off and the brush is automatically reset.

2. The carbon fiber carbonization quality monitoring method based on a roller surface resistance according to claim 1, characterized by: In step 4), R0 is a standard setting value, and the setting process of the value is as follows: when the carbon fibers with qualified carbonization quality are produced, the flying filaments are adsorbed on the roller, and when the first resistance value is measured and calculated, the first flying filament conductive circuit is formed, and the value of 50% of the measured value is set as R0.

3. The roller surface resistance based carbon fiber carbonization quality monitoring method according to claim 1, characterized by: In step 4), the specific establishment process of the R-t function image is as follows: the broken carbon fibers, i.e. the flying filaments, are adsorbed on the surface of the roller and gradually cover the surface with the rotation of the roller to form a plurality of flying filament conductive circuits in parallel; then, the roller is connected with the electrodes at both sides to make the series ammeter circuit connected and the current value measured; the resistance value is calculated through R=U / I; Finally, the data is continuously collected according to the time t to generate an R-t curve.

4. The roller surface resistance based carbon fiber carbonization quality monitoring method according to claim 1, characterized by: In step 4), the specific comparison process of the R-t function image and R0 is as follows: when the intersection point of the R-t function image and R=R0 is between t1 and t2, it reflects that the carbonization quality of the carbon fibers meets the standard; when it is less than t1, the temperature in the carbonization furnace is lowered, and when it is greater than t2, the temperature in the carbonization furnace is increased.

5. The carbon fiber carbonization quality monitoring method based on a roller surface resistance according to claim 4, characterized by: The setting process of the values of t1 and t2 is as follows: when the carbon fibers with qualified carbonization quality are produced, the resistance of the flying filaments is measured, and the resistance value decreases with time; when the R-t function image intersects with R=R0, the intersection point is located between t1 and t2 to be set; the temperature in the carbonization furnace is gradually increased, and the intersection point is recorded each time; when the temperature is increased to make the carbonization quality unqualified, the intersection point is set as t1; in the same way, the temperature in the carbonization furnace is gradually decreased, and when the temperature is decreased to make the carbonization quality unqualified, the intersection point is set as t2.

6. The roller surface resistance based carbon fiber carbonization quality monitoring method according to claim 1, characterized by: In step 5), the specific method for cleaning carbon fiber fly filaments is as follows: start the motor II of the eccentric wheel, transmit motion to the crank, and link the connecting rod and the slider in sequence, so that the slider moves back and forth along the guide rail; the pressure drop device descends, so that the brush descends to a height close to the roller, and the brush cleans the carbon fiber fly filaments under the reciprocating motion of the slider.

7. The roller surface resistance based carbon fiber carbonization quality monitoring method according to claim 1, characterized by: The motor I is mounted on one of the bearing seats via a coupling; the two ends of the roller are pivotally connected between a pair of bearing seats via bearings, and the coupling of the motor I connects to and drives the roller to rotate.

8. The roller surface resistance based carbon fiber carbonization quality monitoring method according to claim 1, characterized by: The crank-connecting rod mechanism includes a connecting rod, a crank, an eccentric wheel, and a motor II; one end of the connecting rod is connected to a slider, and the other end is connected to the crank and driven by the crank; the crank is hinged to the eccentric wheel; the motor II is connected to and drives the eccentric wheel to rotate.

9. The roller surface resistance based carbon fiber carbonization quality monitoring method according to claim 1, characterized by: The brush is mounted to the bottom of the pressure dropper by a spring.

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